&EPA
United States
Environmental Protection
Agency
Risk Reduction Engineering Laboratory EPA/625/7-90/007
Center for Environmental Research Information June 1990
Cincinnati, Ohio 45268
Technology Transfer
to Pollution
Prevention
The Printed Circuit Board
Manufacturing Industry
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EPA/625/7-90/007
June 1990
GUIDES TO POLLUTION PREVENTION:
The Printed Circuit Board Manufacturing Industry
RISK REDUCTION ENGINEERING LABORATORY
AND
CENTER FOR ENVIRONMENTAL RESEARCH INFORMATION
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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NOTICE
This guide has been subjected to U.S. Environmental Protection Agency's peer
and administrative review and approved for publication. Approval does not signify
that thecontents necessarily reflectthe views andpolicies of theU.S. Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use. This document is intended as
advisory guidance only to printed circuit board manufacturers in developing
approaches for pollution prevention. Compliance with environmental and occupa-
tional safety and health laws is the responsibility of each individual business and is
not the focus of this document.
Worksheets are provided for conducting waste minimization assessments of
circuit board manufacturing facilities. Users are encouraged to duplicate portions
of this publication as needed to implement a waste minimization program.
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FOREWORD
This guideidentifies andanalyzes waste minimization methodoligies appropriate
for the printed circuit board manufacturing industry. The wastes resulting from
printed circuit board manufacturing are associated with five types of processes:
cleaning and surface preparation; catalyst application and electroless plating;
pattern printing and masking; electroplating; and etching. The wastes include
airborne particulates, spent plating baths, waste rinsewater, and other wastes.
Waste minimization assessment worksheets are contained with in this guide
to be of use to shop managers and engineers, or consultants in formulating a waste
minimization strategy for a particular plant. Case histories of waste minimzation
assessments performed at three plants are presented.
111
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ACKNOWLEDGMENTS
This guide is based in part on waste minimization assessments conducted by
Planning Research Corporation, San Jose, California for the California Department
of Health Services (DHS). Contributors to these assessments include: David Leu,
Benjamin Fries, Kim Wilhelm, and Jan Radimsky of the Alternative Technology
Section of DHS. Much of the information in this guide that provides a national
perspective on the issues of waste generation and minimization for circuit board
manufacturers was provided originally to the U.S. Environmental Protection
Agency by Versar, Inc. and Jacobs Engineering Group Inc. in Waste Minimization-
IssuesandOptions,VolumeII, ReportNo.PB87-l 14369(1986). JacobsEngineering
Group Inc. edited and developed this version of the waste minimization assessment
guide, under subcontract to Radian Corporation (USEPA Contract 68-02-4286).
Lisa M. Brown of the U.S. Environmental Protection Agency, Office of
Research and Development, Risk Reduction Engineering Laboratory, was the
project officer responsible for the preparation and review of this document. Other
contributors andreviewers include: BonnieBlam.IBMcorporation; BonnieGariepy
and Terrence J. McManus, Intel Corporation; and Arthur H. Purcell, UCLA
Engineering Research Center.
IV
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CONTENTS
Section Page
Notice ii
Foreword ; iii
Acknowledgments iv
1. Introduction 1
2. Printed Circuit Board
Manufacturing Industry Profile 5
3. Waste Minimization Options for Printed
Circuit Board Manufacturers ; 9
4. Guidelines for using the Waste Minimization AssessmentWorksheets 26
Appendix A:
Case Studies of Printed Circuit Board Manufacturing Plants 43
Appendix B:
Where to Get Help; Further Information on
Waste Minimization 73
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SECTION 1
INTRODUCTION
This guide is designed to provide printed circuit board
manufacturers with waste minimization options appropriate
for this industry. It also provides worksheets designed to
be used for a waste minimization assessment of a
manufacturing facility, to develop an understanding of the
facility's waste generating processes and to suggest ways
that the waste may be reduced.
The worksheets and the list of waste minimization
options were developed through assessments of three Santa
Clara area prototype circuit board manufacturing shops.
The assessments were commissioned by the California
Department of Health Services (CDHS 1987). The firms'
operations, manufacturingprocesses.and waste generation
andmanagementpracticesweresurveyed,andtheirexisting
and potential waste minimization options were
characterized. Economic analyses were performed on
selected options.
Today's industry is faced with the major technological
challenge of identifying ways to effectively manage
hazardous waste. Technologies designed to treat and
dispose of wastes are no longer the optimal strategy for
handling these wastes for two major reasons. First, the
potential liabilities associated with handling and disposing
of hazardous wastes have increased significantly. Second,
restrictions placed on land disposal of hazardous wastes
have caused considerable increases in waste disposal costs.
The economic impact of these changes is causing industry
to explore alternatives to treatment and disposal
technologies.
Waste minimization is a policy specifically mandated
by the U.S. Congress in the 1984 Hazardous and Solid
Wastes Amendments to the Resource Conservation and
Recovery Act (RCRA). As the federal agency responsible
for writing regulations under RCRA, the U.S.
Environmental Protection Agency (EPA) has an interest in
ensuring that new methods and approaches are developed
for minimizing hazardous waste and that such information
is made available to the industries concerned. This guide
is one of the approaches EPA is using to provide industry-
specific information about hazardous waste minimization.
The options and procedures outlined can also be used in
efforts to minimize other wastes generated in a facility.
EPA has also developed a general manual for waste
minimization in industry. The Waste Minimization Oppor-
tunity Assessment Manual (USEPA 1988) tells how to
conduct a waste minimization assessment and develop
options for reducing hazardous waste generation at a
facility. It explains the management strategies needed to
incorporate waste minimization into company policies and
structure, how to establish a company-wide waste
minimization program, conduct assessments, implement
options, and make the program an on-going one. The
elements of waste minimization assessment are explained
in the next section of this document, the Overview.
In the following sections of this manual you will find:
An overview of the printed circuit board (PC
board) manufacturingindustryandtheprocesses
used by the industry (Section Two);
Waste minimization options for printed circuit
board manufacturers (Section Three);
Waste Minimization Assessment Guidelines
and Worksheets (Section Four)
An Appendix, containing:
Case studies of waste generation and
waste minimization practices of three
printed circuit board manufacturers;
Where to get help: additional sources of
information.
Overview of Waste Minimization
Assessment
In the working definition used by EPA, waste
minimization consists of source reduction (preventing the
generation of wasteatitspointof origin) andrecycling. Of
the two approaches, source reduction is usually considered
preferable torecyclingfrom an environmental perspective.
Treatmentof hazardous waste is considered an approach to
waste minimization by some states but not by others, and
is not addressed in this guide.
A Waste Minimization Opportunity Assessment
(WMOA), sometimes called a waste minimization audit, is
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a systematic procedure for identifying ways to reduce or
eliminate waste. The steps involved in conducting a waste
minimization assessment are outlined in Figure 1 and
presented in moredetail in thenextparagraphs. Briefly.the
assessmentconsistsofacarerulreviewofaplant'soperations
and waste streams and the selection of specific areas to
assess. Afteraparticularwastestreamorareais established
as the WMOAfocus.anumber of options with thepotential
to minimize waste are developed and screened. The
technical and economic feasibility of the selected options
are then evaluated. Finally, the most promising options are
selected for implementation.
To determine whether a WMOA would be useful in
your circumstances, you should first read this section
describingtheaimsandessentialsoftheassessmentprocess.
For more detailed information on conducting a WMOA,
consultThe Waste Minimization Opportunity Assessment
Manual.
The four phases of a waste minimization opportunity
assessment are:
Planning and organization
Assessment phase
Feasibility analysis phase
Implementation
PLANNING AND ORGANIZATION
Essential elements of planning and organization for a
waste minimization program are: getting management
commitment for the program; setting waste minimization
goals; and organizing an assessment program task force.
The importance of these initial steps cannot be over
estimated.
ASSESSMENT PHASE
The assessment phase involves a number of steps:
Collect process and facility data
Prioritize and select assessment targets
Select assessment team
Review data and inspect site
Generate options
Screen and select options for feasibility study
Collect process andfacility data. The waste streams
at a facility should be identified and characterized.
Information about waste streams may be available on
hazardous waste manifests, waste profile sheets, routine
sampling programs and other sources.
Developing a basic understanding of the processes
that generate waste at a facility is essential to the WMOA
process. Flow diagrams should be prepared to identify the
quantity, types and rates of waste generating processes.
Also, preparing material balances for various processes
can be useful in tracking various process components and
identifying losses or emissions that may have been
unaccounted for previously.
Prioritize and select assessment targets. Ideally, all
waste streams in afacility should be evaluated for potential
waste minimization opportunities. With limitedresources,
however, a plant manager may need to concentrate waste
minimization efforts in a specific area. S uch considerations
as quantity of waste, hazardous properties of the waste,
wastedisposalrestrictions,regulations,safety of employees,
economics, cost of disposal, and other characteristics need
to be evaluated in selecting a target stream.
Select assessment team. The team should include
people with direct responsibility and knowledge of the
particular waste stream or area of the plant, including
machine operators and maintenance personnel.
Review data and inspect site. The assessment team
evaluates process data in advance of the inspection. The
inspection should follow the target process from the point
where raw materials enter the facility to the points where
products and wastes leave. The team should identify the
suspectedsourcesof waste. This may include the production
process; maintenance operations; and storage areas for raw
materials, finished product, and work in progress. The
inspection may result in the formation of preliminary
conclusions about waste minimization opportunities. Full
confirmation of these conclusions may require additional
data collection, analysis, and/or site visits.
Generate options. The objective of this step is to
generateacomprehensivesetofwaste minimization options
for further consideration. Since technical and economic
concerns will be considered in the later feasibility step, no
options are ruled out at this time. Information from the site
inspection, as well as trade associations, government
agencies, technical and trade reports, equipment vendors,
consultants, and plant engineers and operators may serve
as sources of ideas for waste minimization options.
Both source reduction and recycling options should be
considered. Source reduction may be accomplished
through:
Good operating practices
Technology changes
Input material changes
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Figure 1. The Waste Minimization Assessment Procedure
The Recognized Need to Minimize Waste
PLANNING AND ORGANIZATION
1 Get management commitment
1 Set overall assessment program goals
1 Organize assessment program task force
Assessment Organization &
Commitment to Proceed
ASSESSMENT PHASE
> Collect process and facility data
> Prioritize and select assessment targets
1 Select people for assessment teams
1 Review data and inspect site
1 Generate options
' Screen and select options for further study
Select New Assessment
Targets and Reevaluate
Previous Options
Assessment Report of
Selected Options
'
FEASIBILITY ANALYSIS PHASE
1 Technical evaluation
1 Economic evaluation
1 Select options for Implementation
Final Report, Including
Recommended Options
IMPLEMENTATION
Justify projects and obtain funding
Installation (equipment)
Implementation (procedure)
Evaluate performance
Repeat the Process
'Successfully Implemented
Waste Minimization Projects
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Product changes
Recycling includes:
Use and reuse of waste
Reclamation
Screen and select options for further study. This
screening process is intended to select the most promising
options for full technical and economic feasibility study.
Througheitheraninfonnalrevieworaquantitativedecision-
making process, options that appear marginal, impractical
or inferior are eliminated from consideration. Some of the
criteriausedinscreeningoptionsincludeimpactsonproduct
quality; employee safety; and environmental impacts of
the alternatives.
FEASIBILITY ANALYSIS
An option must be shown to be technically and
economicallyfeasibleinordertomeritseriousconsideration
foradoptionatafacility. Atechnicalevaluation determines
whether a proposed option will work in a specific
application. Both process and equipment changes need to
be assessed for their overall effects on waste quantity,
toxicity, and product quality. Also, any new products
developed through process and/or raw material changes
need to be tested for market acceptance.
An economic evaluation is carried out using standard
measures of profitability, such aspaybackperiod, return on
investment, and net present value. As in any project, the
cost elements of a waste minimization project can be
brokendowninto capital costs and economiccosts. Savings
and changes in revenue also need to be considered.
IMPLEMENTATION
An option that passes both technical and economic
feasibility reviews should then be implemented at afacility.
It is then up to the WMOA team, with management
support, to continue the process of tracking wastes and
identifyingopportunitiesforwasteminimization throughout
a facility and by way of periodic reassessments. Either
such ongoing reassessments or an initial investigation of
waste minimization opportunities can be conducted using
this manual.
While it is difficult to quantify the future liability
reduction that could result from implementing an option,
this is an important factor in choosing a particular strategy,
and should at least be discussed qualitatively in the
evaluation. .
References
CDHS. 1987. Waste Audit Study: Printed Circuit Board
Manufacturers. ReportpreparedbyPlanningResearch
Corporation, San Jose, California, for the California
Department of Health Services, Alternative
Technology Section, Toxic Substances Control
Division, April 1987.
USEPA. 1988. Waste Minimization Opportunity
Assessment Manual. Hazardous Waste Engineering
Research Laboratory , Cincinnati, Ohio, EPA/625/7-
88/003.
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SECTION 2
PRINTED CIRCUIT BOARD
MANUFACTURING INDUSTRY PROFILE
Manufacturers of printed circuit boards (PC boards)
are included as part of the electronic component
manufacturing industry. As of 1984, the printed circuit
board manufacturing industry consisted of a total of 585
plants with an employment of 435,100 (NCO 1984).
Industry personnel indicate that the actual number of plants
may be closer to 1,000 (USEPA1986).
Theindustry consists of large facilities totally dedicated
to printed circuit boards, large and small captive facilities,
small job shops doing contract work, and specialty shops
doing low-volume and high-volume precision work.
Approximately half of the printed circuit boards produced
are by independent producers, while the rest are by captive
producers. Over 65 percent of all printed circuit board
manufacturing sites are located in the northeastern states
and in California (NCO 1984).
The printed circuit board manufacturers visited as a
part of this study are all considered small. Generally, these
small companies can be characterized as those that produce
up to 3,000 to 5,000 square feet of processed board each
month and require approximately 8,000 to 10,000 square
feet ofbuilding space. Largecompanies can becharacterized
as those that produce or 30,000 to 50,000 square feet per
month.
Products and Their Use
Printed circuit boards can be classified into three basic
types: single-sided, double-sided, and multi-layered. The
total board production in 1983 was 14 million square
meters (PEI 1983). Double-sided boards accounted for
about 55 percent of the printed circuit boards produced,
while multi-layer board production made up 26 percent
(PEI 1983). The type of board produced depends on the
spatial and density requirement, and on the complexity of
the circuitry. Printed circuit boards are used mainly in the
production of business machines, computers,
communication equipment, control equipment and home
entertainment equipment.
Raw Materials
The following raw materials are used by the industry
(Stintson 1983, PEI 1983, Cox and Mills 1985):
Board materials
Cleaners
Etchants
Catalysts
Electroless copper
bath
Screen
Screen ink
Resists
Sensitizers
Resist solvents
Electroplating baths
glass-epoxy, ceramics, plastic,
phenolic paper, copper foil
sulfuric acid, fluoroacetic acid,
hydrofluoric acid, sodium
hydroxide, potassium hydroxide,
trichloroethylene, 1,1,1-
trichloroethane, perchloroethylene,
methylene chloride
sulfuric and chromic acid,
ammonium persulfate, hydrogen
peroxide, cupric chloride, ferric
chloride, alkaline ammonia
stannous chloride, palladium
chloride
copper sulfate, sodium carbonate,
sodium gluconate, Rochelle salts,
sodium hydroxide, formaldehyde
silk, polyester, stainless steel
composed of oil, cellulose, asphalt,
vinyl or other resins
polyvinyl cinnamate, allyl ester,
resins, isoprenoid resins,
methacrylate derivatives, poly-
olefin sulfones
thiazoline compounds, azido
compounds, nitro compounds, nitro
aniline derivatives, anthones,
quinones, diphenyls, azides,
xanthone, benzil
ortho-xylene, meta-xylene, para-
xylene, toluene, benzene,
chlorobenzene, cellosolve and
cellosolve acetate, butyl acetate,
1,1,1-trichoroethane, acetone,
methyl ethylketone, methyl isobutyl
ketone
copper pyrophosphate solution,
acid-copper sulfate solution, acid-
copper fluoroborate solution, tin-
lead, gold, and nickel plating
solutions
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Resist stripping sulfuric-dichromate, ammoniacal
hydrogen peroxide, solutions
metachloroperbenzoic acid,
methylenecMoride.methylalcohol,
furfural, phenol, ketones,
chlorinated hydrocarbons, non-
chlorinated organic solvents,
sodium hydroxide
Process Description
Printed circuit (PC) boards, also called printed wiring
boards, consist of patterns of conductive material.fbrmed
onto a non-conductive base. The conductor is generally
copper, although aluminum, chrome, nickel and other
metals have been used. The metal is fixed to the base
through use of adhesives, pressure/heat bonding, and
sometimes screws. Base materials include pressed epoxy
paper, phenolic, epoxy glass resins, teflon-glass, and many
other materials.
There are three common types of PC boards: single-
sided, double-sided, and multilayer. Single sided boards
are those with a conductive pattern on one side only.
Double-sided boards have conductive patterns on both
faces. Multilayer boards consist of alternating layers of
conductor and insulating material, bonded together. The
conductors are connected together through plated-through
holes.
Production methods that have been employed by the
Indus try toproduceprintedckcuitboardsincludesubtractive
processes and additive processes. Detailed descriptions of
the process sequences are given elsewhere (Yapoujian
1982,Coombs 1979.USEPA 1979.PEI 1983). Becauseof
the limitations of the additive processes, the subtractive
method is currently the one most widely used, although it
can produce more metal wastes than additive methods.
The subtractive method is briefly described below for
double-sided panels. Most of the operations shown are
also common to the production of other types of printed
circuitboards such as single-sided or multi-layered boards.
The conventional subtractive process employs a
copper-cladlaminate board composed of anon-conductive
material such as glass epoxy or plastic. Printed circuit
board manufacturers often purchase panels of board that
are already copper clad from independent laminators. The
manufacturingprocessconsistsofthefollowingoperations:
Board preparation - The process sequence begins
with a baking step to ensure that the copper laminated
boards arecompletely cured. Holes for the components are
then drilled through stacks of boards or panels, often four
layers thick. The drilling operation results in burrs being
formed on one or both sides of the panel. These are
removed mechanically through sanding and deburring
steps to create an even surface.
Electroless copper plating - The smooth copper-clad
board is subsequently electroless- plated with copper to
provide a conducting layer through the drilled holes for
circuitconnections between thecopper-cladboardsurfaces.
Electroless plating involves the catalytic reduction of a
metallic ion in an aqueous solution containing a reducing
agent, resulting in deposition without the use of external
electrical energy. The circuit board must be thoroughly
cleaned before it is electroless-plated.
Materials typically used in the operation, that appear
in the waste streams, include:
Abrasive and alkaline cleaning compounds
Ammonium persulfate or peroxide-sulfuiic acid
etchant, for removing the oxidation inhibitor in
the copper foil
Tin and palladium catalyst
Cupric chloride or copper sulfate plating bath
containing formaldehyde or hypophosphate
reducing agents, and amino acid, carboxylic
acid, hydroxy acid, or amine chelating agents
Rinsewaters
Pattern printing and masking - Electroless plating
with copper provides a uniform but very thin conducting
layer over the entire surface, that has little mechanical
strength. It is used initially, to deposit metal on non-
conducting surfaces such as inside the holes. Electroplating
is required to build up the thickness and strength of the
conducting layers.
Pattern plating is one method of buiding lip conducting
layer thickness, and is themost common type of subtractive
process used. It consists of electroplating only the insides
of the holes and the circuit patterns. A layer of resist is
deposited, using screen or photolithography techniques, in
areas whereelectroplatedconductingmaterial is not desired.
The layer of resist on these areas is later stripped off, and
the copper foil is etched away.
The area where the resist has not been deposited
constitutes the circuit pattern. These areas receive several
electrodeposition layers. Tin/lead plating is one of the
layers deposited, and it functions as another resist layer,
allowing copper foil in the non-circuit areas to be etched
away without the circuit pattern being damaged. The
circuit pattern then receives final electroplated layers of
metals such as nickel and gold. Chemicals used for these
processes include:
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Photo-sensitive inks (for silk screening circuit
patterns onto the board)
Resists composed of epoxy vinyl polymers,
halogenated aromatics, methacrylates, and/or
polyolefin sulfones
Alkaline cleaners to remove residuals from
pattern developing operations
Acid dips to remove oxides
Electroplating solutions typically containing
copper, tin/lead, nickel and gold salts, cyanide,
sulfate, pyrophosphate, and fluoroborate
compounds
Etchantssuchasperoxide-sulfuricacid,sodium
persulfate,ferricorcupricchloride,andchromic
acid
Panelplating methods ofPCboardmanufacturediffer
from pattern plating in that the entire board is electroplated
with copper, including the holes, after which the non-
circuit areas are etched away. Because of the additional
copper deposited, panel plating can produce more metal
wastes.
The fully additive method differs from the subtractive
method described above in that it involves deposition of
plating material onto the board only in the pattern dictated
by the circuit, and does not require removal of the metal
already deposited. The process begins with an unclad
board. Plating resist is then applied onto the board in non-
circuit areas. Electroless copper is subsequently deposited
to build up the circuit to the desired thickness. Since the
board doesn't initially have any copper in non-circuit areas,
a copper etching step is thus eliminated, as well as much of
the metal wastes.
Waste Description
There are five principal operations common to the
production of all types of printed circuit boards. These
include:
Cleaning and surface preparation
Catalyst application and electroless plating
Pattern printing and masking
Electroplating
Etching
Typical waste streams generated from the unit
operations in the printed circuit board manufacturing
industry are listed in Table 1.
Airborne particulates generated from the cutting,
sanding, routing, drilling, beveling, and slotting operations
during board preparations are normally collected and
separated using baghouse and cyclone separators. They
are then disposed of, along with other solid wastes at
landfills.
Acid fumes from acid cleaning and organic vapors
from vapor degreasing are usually not contaminated with
other materials, and therefore are often kept separate for
subsequenttreatment. Theacidfumeair stream iscollected
via chemical fume hoods and sent to a scrubber where it is
removed with water. The scrubbedair then passes on to the
atmosphere, and the absorbing solution is neutralized
along with other acidic waste streams. Similarly, organic
fumes are often collected and passed through a bed of
activated carbon. The carbon bed is then regenerated with
steam. In many cases, the regenerative vapor is condensed
and the condensate containing water and solvents is
drummedand sent for offsite treatments. In afew cases, the
regenerative vapor is combusted in a closed fumes burner.
The spentacidandalkalinesolutions from thecleaning
steps are either contract hauled for off-site disposal or
neutralized and discharged to the sewer. Spent chlorinated
organic solvents are often gravity separated, and are
recovered in-house or hauled away for reclaiming.
The remaining majority of the wastes produced are
liquid waste streams containing suspended solids, metals,
fluoride, phosphorus, cyanide, and chelating agents. Low
pH values often characterize the wastes due to acid cleaning
operations. The liquid wastes may be controlled using end-
of-pipe treatment systems, or a combination of in-line
treatment and separate treatment of segregated waste
streams. A traditional treatment system for the wastes
generated is often based on pH adjustment and the addition
of chemicals that will react with the soluble pollutants to
precipitate out the dissolved contaminants in a form such
as metal hydroxide or sulfate. The solid particles are
removed as a wet sludge by filtration or flotation, and the
water is discharged to the sewer. The diluted sludge is
usually thickened before dumping into landfills. Recent
improvements in in-line treatment technologies such as
reverse osmosis, ion exchange, membrane filtration, and
advanced rinsing techniques increase the possibility for the
recovery and reuse of water and metallic resources.
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Table 1. Waste Streams from Printed Circuit Board Manufacturing
Waste Source
Cleaning/Surface preparation
Catalyst application/
Electroless plating
Pattern printing/masking
Electroplating
Etching
Waste Stream
Description
i. Airborne participates
2. Acid fumes/organic vapors
3. Spent acid/alkaline solution
4. Spent halogenated solvents
5. Waste rinse water
1 .Spent electroless copper bath
2. Spent catalyst solution
3. Spent acid solution
4. Waste rinse water
1. Spent developing solution
2. Spent resist removal solution
3. Spent acid solution
4. Waste rinse water
1. Spent plating bath
2. Waste rinse water
1. Spent etchant
2. Waste rinse water
Waste Stream
Composition
Board materials,
sanding materials,
metals, fluoride,
acids, halogenated
solvents, alkali.
Acids, stannic
oxide, palladium,
complexed metals,
chelating agents.
Vinyl polymers,
chlorinated
hydrocarbons/organic
solvents, alkali.
Copper, nickel, tin,
tin/lead, gold,
fluoride, cyanide, sulfate.
Ammonia, chromium,
copper, iron,
References
Coombs, CJF. 1979. Printed Circuit Handbook. 2nd ed.
New York, N.Y.: McGraw-Hill Book Co.
Cox, D.S., and A JR. Mills. 1985. Electronic chemicals: a
growth market for the 80's. Chem. Eng. Prog. 81(1):
11-15.
NCO. 1984. National Credit Office. Electronic marketing
directory. New York: National Credit Office.
PEL 1983. Pedco-Environmental, Inc.
Profiles for Environmental Use. Chapter 30. The
ElectronicComponentManufacturinglndustry. EPA-
600-2-83-033. Cincinnati, Ohio. U.S. Environmental
Protection Agency.
Rothschild,B.K, and Schwartz, M. 1988. Printed Circuil/
Wiring Board Manufacture. American Electroplaters
and Surface Finishers Society.
Stintson.S.C. 1983. Chemicals for electronics: new growth
in competitive field. Chem. Eng. News. 61(30): 7-12.
USEPA. 1979. U.S. Environmental Protection Agency,
OfficeofWater andHazardous Materials. Development
DocumentforExisting SourcePretreatmentStandards
for the Electroplating Point Source Category. EPA-
440-1-79-003. Washington,D.C.:U.S.Environmental
Protection Agency.
USEPA 1986. Waste Minimization - Issues and Options,
Volume H. PB87-114369, Prepared by Versar, Inc.
and Jacobs Engineering Group Inc.
Yapoujian, F. 1982. Overview of printed circuit board
technology. Met Finish. 80:21-5.
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SECTION 3
WASTE MINIMIZATION OPTIONS FOR PRINTED CIRCUIT BOARD
MANUFACTURERS
This section discusses recommended waste
minimization methods for printed circuit board
manufacturers. These methods come from accounts
published in the open literature and through industry
contacts. The primary waste streams associated with
manufacturingare listed in Table2alongwith recommended
control methods. Many control measures associated with
photoprocessing and cleaning wastes are not discussed in
this report. Thereader is referred to theappropriatereference
material for information regarding these waste streams
(USEPA 1989.USEPA 1990.USEPA 1986, CDHS1986).
The waste minimization methods listed in Table 2 can
be classified generally as source reduction, or recycling.
Source reduction can be achieved through material or
product substitution, process or equipment modification,
or better operatingpractices. RecycUngcanincluderecovery
of part of the waste stream or reuse of all of it, and can be
performed on-site or off-site.
Betteroperatingpracticesareprocedural or institutional
policies that result in a reduction of waste. They include:
Waste stream segregation
Personnel practices
Management initiatives
Employee training
Employee incentives
Procedural measures
Documentation
Material handling and storage
Material tracking and inventory control
Scheduling
Loss prevention practices
Spill prevention
Preventive maintenance
Emergency preparedness
Accounting practices
Apportion waste management costs to
departments that generate the waste
Better operating practices apply to all waste streams.
In addition, specific better operating practices that apply to
certain waste streams are identified in the appropriate
sections that follow.
Product Substitution
While not under the control of most printed circuit
board manufacturers, improvements in the techniques used
in the packaging of microchips can result in a decrease of
waste associated with printed circuit board manufacturing.
Two new techniques include:
Increased use of surface mount technology. Presently,
the dual-in-line package (DIP) accounts for 80% of all
packaging of integrated circuits (Bowlby 1985). More
efficient packages, however, are being developed which
utilize a relatively new method of attaching packages to
printed circuit boards. One important method is called
surface mount technology (SMT). Theuseof SMT instead
of the conventional through-hole insertion mounting allows
for closer contact areas of chip leads, and therefore reduces
the size of printed circuit boards required for a given
number of packages or DIPS. For a fixed number of
packages, the printed circuit board needs to be only 35
percent to 60 percent as large as a printed circuit board
designed for the old style package (Bowlby 1985). As the
metal area on which cleaning, plating and photoresist
operations areperformedis decreased, the wastes associated
with these operations can also be reduced. At present,
however, SMT uses considerably higher quantities of
chlorofluorocarbons for degreasing than through-hole
mounting. CFC-113 isoneof the major degreasing agents
in current use. Because of the danger that some
chlorofluorocarbonspresent to theatmospheric ozone layer,
the overall environmental risks of SMT must be carefully
examined, and alternative degreasing solvents identified,
before replacing through-hole technology with SMT.
Use of injection molded substrate andadditive plating.
The development of high-temperature, high-performance
thermoplastics has introduced the use of injection molding
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Table 2. Waste Minimization Methods for the Printed Circuit Board Industry
Operation Waste Minimization Method
PC Board Manufacture
Cleaning and Surface
Preparation
Pattern Printing and
Masking
Electroplating and
Electroless Plating
Etching
Product Substitution:
Surface mount technology
Injection molded substrate and additive plating
Materials substitution:
Use abrasives
Use non-chelated cleaners
Increase efficiency of process:
Extend bath life, improve rinse efficiency,
countercurrent cleaning
Recycle/reuse:
Recycle/reuse cleaners and rinses
Reduce hazardous nature of process:
Aqueous processable resist
Screen printing versus photolithography
Dry photoresist removal
Recycle/reuse:
Recycle/reuse photoresist stripper
Eliminate process:
Mechanical board production
Materials substitution:
Non-cyanide baths
Non-cyanide stress relievers
Extend bath life: reduce drag-in
Proper rack design/maintenance, better
precleaning/rinsing, use of demineralized
water as makeup, proper storage methods
Extend bath life: reduce drag-out
Minimize bath chemical concentration,
increase bathtemperature, use welting agents,
proper positioning on rack, slow withdrawal
and ample drainage, computerized/automated
systems, recover drag-out, drain boards
Extend bath life: maintain bath solution quality
Monitor solution activity. Control temperature.
Mechanical agitation. Continuous filtration/
carbon treatment.
Impurity removal
Improve rinse efficiency:
Closed-circuit rinses. Spray rinses. Fog
nozzles. Increased agitation. Countercurrent
rinsing. Proper equipment design/operatnon.
Deionized water use.
Recovery/reuse:
Segregate streams.
Recover metal values
Eliminate process:
Differnetial plating
Materials substitution:
Non-chelated etchants. Non-chrome etchants
10
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Table 2. Waste Minimization Methods for the Printed Circuit Board Industry
(continued)
Operation Waste Minimization Method
Etching
(continued)
Wastewater Treatment
Increase efficiency:
Use thinner copper cladding. Pattern
vs. panel plating. Additive vs. subtractive
method.
Reuse/recycle:
Reuse/recycle etchants
Reduce hazardous nature:
Alternative treatment chemicals that generate
less sludge Use of ion exchange and activated
carbon for recycling wastewater
Reuse/recycle:
Waste stream segregation
into the manufacturing of printed circuit boards. In this
process, heated liquid polymer is injected under high
pressure into precision molds. Since the molded substrates
are unclad, semi-additive or fully additive plating is used
to produce metalized conductor patterns (Engelmaier and
Frisch 1982). Injection molding, coupled with a fast-rate
electrodeposition (FRED) technique, suchas thatdeveloped
by Battelle (LWVM 1985), can be used to manufacture
complex three-dimensional printed circuit boards with
possible reduction in hazardous waste generation due to
the elimination of spent toxic etchants.
Cleaning and Surface Preparation
As mentioned in the introduction, the reader should
refer to the appropriate reference material (USEPA 1989,
CDHS 1986) for information regarding the reduction of
waste associated with parts cleaning. Information is
provided below on: abrasive cleaning; useofnon-chelated
cleaning chemicals; extending bath life and improving
rinse efficiency; use of countercurrent cleaning
arrangements; and reuse/recycle of cleaning agents and
rinse water.
USE ABRASIVE INSTEAD OF AQUEOUS
CLEANING
Mechanical cleaning methods offer an alternative to
aqueous techniques and generate less hazardous, waste;
however, these methods can only be employed before
electronic components have been added to the boards.
Abrasive blast cleaning uses plastic, ceramic, or harder
media such as aluminum oxide to remove oxidation layers,
old plating, paint and burrs from workpieces, and to create
a smooth surface. The aim is to select a blast medium that
is harder than the layer to be stripped, but softer than the
substrate, in order to prevent damage to the part. Abrasives
can also be used in vibratory cleaning (in which parts are
immersed in a vibrating tank containing abrasive material
and water), in tumbling barrels, or applied via a buffing
wheel. Moreinformationonabrasivecleaning, particularly
tumbling barrels and vibratory cleaning, can be found in
Durney (1984) and ASM (1987).
USENON-CHELATED CLEANING CHEMICALS
The use of non-chelate process chemicals instead of
chelated chemical baths can reduce hazardous waste
generation. Chelators are employed in chemical process
baths to allow metal ions to remain in solution beyond their
normal solubility limit. This enhances cleaning, metal
etching, and selective electroless plating (Couture 1984).
Once the chelating compounds enter the waste stream, they
inhibit the precipitation of metals, and additional treatment
chemicals must be used. These treatmentchemicals end up
in the sludge and contribute to the volume of hazardous
waste sludge.
Ferrous sulfate is a common reducing agent used to
treat wastewaters that contain chelators. The ferrous
sulfate breaks down the complex ion structures to allow
metals to precipitate. However, the iron added to the
treatment process also precipitates as a metal hydroxide.
Since enough ferrous sulfate is usually added to the
wastewater to achieve an iron to metal ratio of 8:1, a
significant additional volume of sludge is generated
(Couture 1984). One printed circuit board manufacturer
visited during the audit study used ferrous sulfate to break
down chelators prior to metals precipitation. The iron
present in the resultant sludge contributed approximately
32 percent of the total dry weight of the sludge.
Common chelators used in printed circuit board
manufacturing chemicals include ferrocyanide,
11
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ethylenediaminetetraacetic acid (EDTA), phosphates, and
ammonia (Foggia 1987). Chelating agents are commonly
found in cleaning chemicals and etchants. Non-chelate
alkaline cleaners ace available; however, laboratory tests
have shown that some of these products still have the
ability to chelate metals (Couture 1984).
In addition to using non-chelated chemistries, the use
of mild chelators can also reduce the need for additional
treatment of wastewaters. Mild chelators are less difficult
to break down. Therefore, metals can be precipitated out
of solution during treatment without using the volume of
treatment chemicals that is often necessary with strong
chelators. For example, EDTA is a mild chelator that only
requires lowering the pH to below 3.0 to allow metals to
precipitate (Foggia, 1987).
One disadvantage of usingnon-chelatedprocess baths
is that they usually require continuous filtration to remove
the solids that form in the bath. The costs of these filter
systems range from approximately $400 to $1,000 for each
tankusinganon-chelatedprocesschemistry. Thesesystems
generally have a 1 to 5 micron filter with a control pump
that can filter the tank contents once or twice each hour
(Foggia 1987). In addition to the purchase and setup costs,
filter replacement and maintenance costs are incurred
when this system is used.
EXTEND BATH LIFE AND IMPROVE RINSE
EFFICIENCY
This method applies to nearly any tank of processing
solution used in the facility. See the discussion of
electroplating waste reduction methods for detailed
information.
USE COUNTERCURRENT CLEANING
ARRANGEMENT
A common hazardous waste stream generated by
printed circuit board manufacturers is waste nitric acid
from the cleaning of electroplating workpiece racks.
Typically, racks are placed in a nitric acid bath to clean off
theplated copper. When thecoppercontentin the bath gets
too high to effectively clean the racks, the nitric acid is
containerized for disposal. Use of a cascade cleaning
system cansignificantlyreducenitricacid waste generation.
During the audits, one small printed circuit board
manufacturerwhooperatedafivetankplatingrackcleaning
line generated approximately 15 gallons of waste nitric
acid in 6 months compared to another small company that
used a single tank for cleaning racks and generated
approximately 60 gallons each month. Both companies
operate similar size process lines, and are considered small
printed circuit board manufacturers (both estimated their
printed circuit board production to be 3,000 square feetper
month). Assuming that waste disposal for the spent nitric
acid is $50 per 55-gallon drum and the cost of technical
grade nitric acid is approximately $3.50 per gallon, the
differential operating costs are $3042 per year (excluding
differences in labor-increased rack handling versus
decreased waste handling). The total cost of adding four
additional tanks to the one-cleaning-tank line would be
$1620.
REUSE/RECYCLE OF CLEANING AGENTS
Peroxide/suifuric acidsolution is used as amildetchant
for cleaning copper and removing oxides prior to plating.
When the solution is brought off-line and cooled, the
copper crystallizes as copper sulfate. The supernatant can
then be returned to the tank, replenished with oxidizers,
and reused. The copper sulfate crystals can be used as
copper electroplating bath makeup (Couture 1984). The
practice is only advisable, however, if the crystals are first
dissolved into solution and treated with activated carbon to
remove the organics. Otherwise, the organics present in
the crystals could ruin the plating bath.
In addition to recovering metals from the spent bath,
spent acid can be regenerated by means of ion exchange
(Basta 1983). Eco-Tec Ltd., in Ontario, Canada, markets
an acidpurification system that employs aproprietary resin
that recovers mineral acids. The metals are recovered in a
concentrated (but still dissolved) form. The concentrated
metals can then be recovered by electrolytic means.
Ion exchange is employed by Modine Manufacturing,
in Trenton, Mo., to treat copper-contaminated sulfuric
acid/hydrogen peroxide solution which is used to brighten
brass (Basta 1983). Sodium phosphate salts, formed in
nickel/copper electroless plating, can be converted into
useMhypophosphite salts by ion exchange resins activated
with hypophosphorous acid. The use of ion 'exchange
resins for regeneration, however, suffers from the
disadvantage of generating additional wastes, such as
spent resins and resin regeneration solutions.
REUSE/RECYCLE OF RINSE WATER
After rinse solutions become too contaminated for
their original rinse process, they may be useful for other
rinse processes. For example, rinses containing high levels
of process chemicals can be concentrated through
evaporation and returned to the process baths as makeup.
Closed-circuit rinsing of this type can dramatically reduce
the hazardous chemicals content of the waste stream.
Effluent from a rinse system that follows an acid
cleaning bath can be reused as influent water to a rinse
system following an alkaline cleaning bath. If both rinse
systems require the same flow rate, 50 percent less rinse
water would be used to operate them. In addition, using the
12
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effluentfrom the rinse solution that follows an acidcleaning
process as the feed to the rinse system that follows an
alkaline cleaning process rinse system can actually improve
rinseefficiencyfortworeasons. First, the chemical diffusion
process is acceleratedbecause theconcentration of alkaline
material at the interface between the drag-out film and the
surroundingwaterisreducedbytheneutralizationreaction.
Second, the neutralization reaction reduces the viscosity of
the alkalinedrag-outfilm(USEPA1982a). One successful
example of this technique was observed in a nickel plating
process in which the same rinse water stream was used for
the rinses following the alkaline cleaning, acid dip, and
nickel plating tanks. Instead of having three differentrinse
streams, only one stream was used, greatly reducing the
overall rinse water requirements (USEPA 1983).
Adding acid rinses to alkaline rinses can result in
problems, however. Unwanted precipitation of metal
hydroxides onto the cleaned workpieces can occur in some
instances. Before being implemented, a combined acid and
alkaline rinse system must be thoroughly investigated in
the particular environment of the process line.
Other rinse water recycling opportunities are also
available. Acid cleaning rinse water effluent can be used as
rinse water for workpieces that have gone through a mild
acid etch process. Effluent from a critical or final rinse
operation, which is usually less contaminated than other
rinse waters, can be used as influent for rinse operations
that do not require high rinse efficiencies. The water from
fume scrubbers has been shown to be practical for rinsing
in certain cases (Cheremisinoff, Peina, and Ciancia 1976).
Spent cooling water or steam condensate can also be
employed for rinsing if technically permissible and
economically justified. Printed circuitboardmanufacturers
should evaluate the various rinse water requirements for
their process lines and configure rinse system arrangements
that take advantage of rinse water reuse opportunities.
Pattern Printing and Masking
Many of the source reduction techniques discussed for
the photoprocessing industry (USEPA 1988) apply to this
phase of printed circuit board manufacturing. Listedbelow
are several techniques that deal with circuit board
fabrication.
Use aqueous provessable resist instead of solvent
processable resist. Aqueous processable resists (such as
the Du PontRiston photopolymer film resists which allow
for the use of caustic and carbonates as developer and
stripper) can be used in place of solvent processable resists
whenever possible to eliminate the generation of toxic
spent solvents. Hundred of facilities are now employing
these aqueous processable films for the manufacturing of
printed circuit boards.
Use screen-printing instead of photolithography to
eliminate the need for developers. Screen-printing has
conventionally been used only to produce printed circuit
boards which require very low resolution in the width and
spacingofthecircuitlines. Some companies have recently
developed screen-printing techniques which can provide
higher degrees of resolution. For example, GeneralElectric
has developed a method for screen-printing down to 0.01
inch resolution which can be used to manufacture printed
circuit boards for appliances (Greene 1985). The majority
of printed circuit board manufacturers, however, are still
using the photolithographic technique for printed circuit
boards having circuitry finer than 12 mil lines and spaces.
UseAsherdryphotoresistremovalmethodtoeliminate
the use of organic resist stripping solutions. Although this
method is increasingly popular in the semiconductor
industry, its use has not been reported by printed circuit
board manufacturers, probably because the printed circuit
board resists are usually much thicker than thecorresponding
semiconductor resist layers.
Recycle/reusephotoresiststripper. Photoresiststripper
is used to remove photoresist material from the board. This
photoresistis a polymer material thatremains in the stripper
tank in small flakes that slowly settle to the bottom. When
the sludge formed at the bottom of the stripper tank builds
up, the flakes begin to adhere to. circuit boards and the
stripper solution is considered spent. Increased use of the
solution can be achieved by decanting and filtering the
stripper solution out of the tank into a clean tank. This is
feasible because the stripper usually becomes spent as a
result of the residue buildup long before it becomes spent
as a result of a decrease in chemical strength.
Electroplating and Electroless Plating
Source reduction methods associated with
electroplating and electroless plating center around
eliminating the need for the operation, reducing the
hazardous nature of the materials used, extending process
bamUfe,improvingrinseefficiency,andrecoveringAeusing
spent materials.
ELIMINATE NEED FOR OPERATION
Use mechanical board production methods/systems.
For facilities that produce low-volume prototype circuit
boards, mechanicalboardproductionsystemsareavailable
which bypass all operations involving chemicals. Circuit
boards are designed on a computer and the pattern is then
etched by means of a mechanical stylus on a copper-clad
board. While this system is not viable for producingboards
in large quantities, it is highly suited for use in development/
research settings.
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REDUCE HAZARDOUS MATERIALS USED
Use non-cyanide plating baths.
Use non-cyanide stress relievers. In the case of
elcctroless copper plating, water soluble cyanide
compounds of many metals are typically added to eliminate
or minimize the internal stress of the deposit. It has been
found thatpolysiloxanes are also effective stress relievers
(Durney 1984). By substiratmgpolysiloxanes for cyanides,
the hazardous nature of the spent bath solution can be
reduced.
EXTEND PROCESS BATH LIFE
Process baths may contain high concentrations of
heavy metals, cyanides, solvents and other toxic
constituents. They are not discarded frequently but rather
are used for long periods of tune. Nevertheless, they do
require periodic replacement due to impurity build-up
resulting from drag-in or decomposition and the loss of
solution constituents by drag-out. When a solution is
contaminated or exhausted, the resulting waste solution
may contain high concentrations of toxic compounds and
require extensive treatment. The source control methods
available for extending process bath life include reducing
or removing impurities formed in the bath, reducing the
loss of solution (drag-out) from the bath, and maintaining
bath solution quality.
Reduce Impurities
Impurities come from five sources: racks, anodes,
drag-in, water or chemical make-up, and air. The buildup
of impurities can be limited by the following techniques:
Proper rack design and maintenance. Corrosion and
salt buildup deposits on the rack elements contaminate
solutions if they chip away or fall into the solution. Proper
design and regular cleaning will minimize this form of
contamination. Fluorocarbon coatings applied to the racks
have also been found to be effective (Lane 1985). Such a
coating lowers drag-out as well since less bath
solution remains in the corroded crevices on the racks or
barrels.
Use purer anodes and anode bags. During the plating
process, metal from the anode dissolves in the plating
solutionanddepositsonthecathode(workpiece). Someof
the impurities contained in the original anode matrix stay
behind in the plating solution, eventually accumulating to
prohibitive levels. Thus, the use of purer metal for the
anode extends the plating solution life. Anode bags can
also be used to prevent pieces of decomposed anodes from
falling into the tank.
Drag-in reduction by better rinsing Efficient rinsing
of the workpiece between different process baths reduces
the drag-in of plating solution into the next process bath.
Use of deionized or distilled make-up water. To
compensate for evaporation, water is required for makeup
of plating solutions. Using deionized or distilled water is
preferred over tap water, since tap water may have a high
mineral or solids content, which can lead to impurity
buildup.
Proper storage of chemicals. Proper storage of the
process solutions can alsoreduce waste generation. Usually,
the process solutions are stored as a two-part solution and
are mixed when a batch is needed. Prolonged storage of
mixed solutions may allow some chemical reactions to
occur that could generate contaminants that reduce bath
life. In electroless copper plating, if formaldehyde (a
reducing agent) is stored with a hydroxide, the hydroxide
can cause the formaldehyde to break down into formic acid
and methyl alcohol. Thus, it is better to only store non-
reactive mixtures of materials or to store each item
separately.
Once you have reduced impurity buildup in the bath,
youneedto concentrateonreducingsolution losses through
drag out.
Reduce Drag-Out
Several factors contribute to drag-out These include
workpiece size and shape, viscosity and chemical
concentration, surface tension, and temperature (USEPA,
1982a). By reducing the volume of drag-out that enters the
rinse water system, valuable process chemicals can be
saved and sludge generation can be reduced. More
discussion of the impact on sludge generation due to drag-
out is presented under "alternative treatment methods."
During the course of this study, it was found that most
printed circuit board manufacturers have little idea of the
volume of drag-out their various process lines generate.
Process chemical suppliers assess drag-out using a standard
rate of 10 to 15 ml/ft2 of circuit board (Foggia 1987).
However, this standard rate does not take into account the
various process bath operating parameters that can be used
or theeffects of various workpiecerack withdrawal methods.
Nevertheless, this standard drag-out rate is a good starting
point for determining the impact of drag-out on waste
generation. Factors affecting drag-out are described in
TableS.
Table 3. Factors That Increase the Amount
of Drag-Out
High surface tension,
Highly viscous plating solution
Larger workpiece size , . .
Faster workpiece withdrawal .
Shorter drainage time
Orientation of workpiece during removal
so that drainage is reduced
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Generally, drag-out minimization techniques include:
Minimize bath chemical concentration. Controlling
the chemical concentration of the process bath can reduce
drag-out losses in two ways. Reducing toxic chemical
concentrations in a process solution reduces the quantity of
chemicals and the toxicity in any dragoutthat occurs. Also,
greater concentrations of some of the chemicals in a
solution increase the viscosity (USEPA 1982a). As a
result, the film that adheres to the workpiece as it is
removed from the process bath is thicker and will not drain
back into the process bath as quickly. Therefore the
volume of drag-out loss is increased and a higher chemical
concentration in the drag-out is created. In electroless
copper plating for printed circuit boardmanufacture, dilute
solutions have been tried successfully by many
manufacturers (USEPA 1981).
Chemical product manufacturers may recommend an
operating concentration that is higher than necessary to
perform the job. A printed circuit board manufacturer
should determine the lowest process bath concentration
that will provide adequate product quality. This can be
done by mixing a new process bath at a slightly lower
concentration than normal. As fresh process baths are
mixed the chemical concentration can continue to be
reduced until product quality begins to be affected At this
point, the manufacturer can identify the process bath that
provides adequate product quality at the lowest possible
chemical concentration.
Fresh process baths can often be operated at lower
concentrations than used baths. Makeup chemicals can be
added to the used bath to gradually increase the
concentration. This procedure allows newer baths to be
operated at lower concentrations and older baths to be
maintained for longer periods of time before requiring
disposal.
Increase bath operating temperature in order to lower
viscosity. Increased temperature lowers both the viscosity
and surface tension of the solution, thus reducing drag-out.
The resulting higher evaporation rate may also inhibit the
carbon dioxide absorption rate, slowing down the carbonate
formation in cyanide solutions. Unfortunately, this benefit
may be lost due to the formation of carbonate by the
breakdown of cyanide at elevated temperatures. Additional
disadvantages of this option would include higher energy
costs, higher chance for contamination due to increased
make up requirement, and increased need for air pollution
control due to the higher evaporation rate.
Use wetting agents. Wetting agents can be added to a
process bath to reduce the surface tension of a solution and,
as a result, reduce the volume of drag-out loss. The use of
wetting agents in the metal finishing industry has been
estimated to reduce drag-out loss by as much as 50 percent
(USEPA, 1982a). However, most printed circuit board
manufacturers prefer using process chemicals that are free
of wetting agents because they can create foamingproblems
in the process baths. Although the process bath chemistries
of a printed circuit board manufacturing line may not
always allow the addition of wetting agents, their use
should be evaluated.
Positionworkpieceproperlyontheplatingrack.When
a workpiece is lifted out of a plating solution on a rack,
some of the excess solution on its surface (drag-out) will
drop backintothe, bath. Proper positioning of the workpiece
on a rack will facilitate maximum drainage of drag-out
back into the bath. The position of any object which will
minimize the carry-over of drag-out is best determined
experimentally, although the following guidelines were
found to be effective (USEPA 1981):
- Orient the surface as close to vertical as
possible.
- Rack with the longer dimension of the
workpiece horizontal.
- Rack with the lower edge tilted from the
horizontal so that the runoff is from a corner
rather than an entire edge.
While positioning of the printed circuit board offers
little variability the boards are generally placed upright
in a rack a board that is tilted at an angle, allowing it to
drip down onto an adjacent board instead of directly into
the bath, may lead to increased drag-out loss. The operator
must ensure that the workpiece is positioned properly to
prevent unnecessary drag-out loss.
Withdraw boards slowly and allow ample drainage.
The faster an item is removed from the process bath, the
thicker the film on the workpiece surface and the greater
the drag-out volume will be. The effect is so significant
thatitis believed thatmostof the timeallowedfor withdrawal
and drainage of a rack should be used for withdrawal only
(USEPA, 1982a). However, since workpieces are usually
removed from a process bath manually, it is difficult to
control thespeedat which they are withdrawn. Nevertheless,
supervisors and management should emphasize to process
line operators that workpieces shouldbe withdrawn slowly.
Workpiece drainage once the part is removed from the bath
also depends on theoperator. The timeallowedfor drainage
can be inadequate if the operator is rushed to remove the
workpiece rack from the process bath area and place it in
the rinse tank. However, installation of a bar or rail above
the process tank, and the requirement that all workpieces
be hungfromitforatleast 10 seconds, may helpensure that
15
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adequate drainage timeisprovidedprior to rinsing. Printed
circuitboardmanufacturers express concern thatincreasing
workpiece rack removal and drainage time will allow for
chemical oxidation on the board. Although some process
steps may not be amenable to these drag-out reduction
techmques.increasedworkpiecerackremovalanddrainage
time can still be effective for many process steps.
Use computerized!automated control systems.
Computerized process-control systems can be used for
board handling and process bath monitoring to prevent
unexpected decomposition of the plating bath. Since the
use of a computerized control system not only requires a
largecapitaloutlayfor initial installation but also increases
the demand for skilled operations and maintenance
personnel, only very large companies which manufacture
both printed circuit boards and other electronic components
are incorporating this change in theirmanufacturingprocess.
For example, Hewlett-Packard in Sunnyvale, California
reported its successful use of computers for plating
operations on printed circuit boards (Anonymous 1983).
Recover drag-outfrom baths. In addition to reducing
the volume of drag-out that is lost from the process bath,
printed circuit board manufacturers can recover drag-out
losses by using drain boards and close-circuit rinsing.
Drain boards are used to capture process chemicals that
drip from the workpiece rack as it is moved from the
process bath to the rinse system. The board is mounted at
an angle thatallowsthechemical solution to drainbackinto
the process bath. Drainage boards should be installed if
there is space between the process bath tank and the rinse
tank where chemical solutions would otherwise drip onto
the floor and enter the wastewater system when the floor is
washed down.
Another methodofreducingdrag-outloss is torecover
it for reuse in the process tank. The most common way to
do this is through use of drag-out tanks (also called still or
deadrinses). Drag-outtankscanbeusedtocaptureprocess
chemicals mat adhere to the circuit board and return them
to the process bath. Drag-out tanks are essentially rinse
tanks that operate without a continuous flow of feed water.
Chemical concentrations in these tanks increase as more
workpieces are passed through. Since there is no feed
water flow to cause rinse water turbulence, air agitation is
often used to enhance rinsing. After a period of time, the
concentration of the drag-out tank solution will increase to
thepoint where itcan be used to replenish the process bath.
Drag-out tanks are primarily used with process baths that
operate at an elevated temperature. The high temperature
causes evaporative water losses that can be compensated
for by adding the drag-out tank solution back to theprocess
bath. If the evaporation rate of the process tank is not high
enough, evaporators can be installed on it. They can also
be installed on the drag-out tank, to further concentrate the
rinse solution to be used as makeup.
Closed-circuit rinse systems can employ continuously
flowing rinses as well as static rinses that are periodically
added as makeup to the process bath. Often, two or more
rinses are used in a counter-current arrangement such as is
illustrated in Figure 2. In this arrangement, the work is first
rinsed in the least clean rinse bath, and then in successively
cleaner baths. Spent rinse water from the cleanest bath gets
added to the next cleanest bath, and eventually to the
process bath itself. The use of closed-circuit rinses can be
very significant in reducing the amount of heavy metal
wastes and other hazardous chemicals in the waste streams
(Meltzer 1989).
The printed circuit board manufacturing companies
visited during this study all used drag-out tanks, but none
of them used the drag-out solution to replenish the process
bath. Instead, these companies dumped the solutions into
their treatment systems. They are reluctant to reuse the
drag-out solution because of fear of contamination. Since
a drag-out tank can often be used for more than a week
between dumps andbecause the tankis uncovered, operators
are concerned that someone could improperly use the tank
to rinse a workpiece; the contaminated drag-out solution
would then contaminate the process bath when used to
replenish the process tank. Also, some process bath
chemistries are such that adding drag-out solution back
into the process tank would spoil the bath. For example,
electroless copper baths contain chemicals that break down
in a diluted drag-out solution. If the solution is then added
back to the process tank, these breakdown chemicals could
adversely affect the electroless copper bath (Stone 1987).
If the potential for contamination or deterioration of the
drag-out solution can be overcome, however, drag-out
tanks can be used on copper and tin/lead electroplating
lines.
Maintain Bath Solution Quality
Once the amount of drag-in and drag-out from the
process bath has been reduced, attention should focus on
ways to maintain the bathat optimum operating conditions.
Many facilities rely on drag-out from the bath as the way
of purging impurities that would otherwise build up and
interfere with operation. From an environmental viewpoint,
this isapoor technique since itdoes not directly address the
issue of impurity formation, results in high losses of
valuable process solutions, and moves the problem
downstream to the treatment unit.
The following methods are noted as ways of increasing
bath life and minimizing the impact on existing treatment
systems:
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Figure 2. Multiple Closed Circuit Counterflow Rinse System
Path of Work
r
Process
Bath
1st
Rinse
2nd
Rinse
Path of Makeup Water
Monitor solution activity. By frequent monitoring of
the bath activity and regular replenishment of reagents or
stabilizers, bath life can be prolonged (Durney 1984).
These reagents or stabilizers differ from process to process.
Stabilizers such as 2-mercaptobenzothiozole and methanol
are found effective in electroless copper plating used for
manufacturing printed circuit boards. The addition of
stabilizers can sometimes decrease the deposition rate, but
can still be economical in the long run.
Control bath temperature. Good control of the bath
temperature is importantfrom the viewpointofperformance
predictability and is another method of prolonging bath
life. Many surface treatment operations use tanks with
immersed cooling/heating coils. As the salts precipitate
and form scales on the coils the heat transfer is impeded and
temperature control becomes increasingly difficult. Heat
transfer efficiency can be maintained by periodic cleaning
of the coils or by using jacketed tanks instead of coils.
Use mechanical agitation. Many process baths employ
air agitation to increase and maintain the efficiency of the
bath. This practice can introduce contaminants into the
bath. The two principal contaminants are oil from the,
compressor orblowerandcarbon dioxide. Theoil will lead
to undue organic loading while the carbon dioxide can lead
to carbonate buildup in alkaline baths. A viable alternative
is to use mechanical agitation.
Use continuous filtering! carbon treatment. To avoid
surface roughness in the plating resulting in high reject
rates, baths should be continuously filtered to remove
impurities. The flow rate to the filter should be as high as
practical to preventjparticles from settling on the parts.
Since filters can seldom remove solids at the same rate that
they are introduced by way of drag-in, filtering should be
performed even when the bath is not in use. Install as
coarse a filter as practical, since coarse filters allow higher
loading before requiring replacement, allow for higher
flow rates and hence greater tank turn-overs, and require
less servicing. When organic buildup is a problem, use of
carbon filter cartridges is appropriate.
Regenerate solution through impurity removal. There
are methods that have been successfully used to increase
the longevity of plating solutions through impurity removal.
17
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More efficient filtering of aplating solution has kept levels
of impurities low andextended solution life (McRae 1985).
Metallic salts can sometimes be removed by temporarily
lowering the bath temperature so as to form solid crystals.
In the case of electroless nickel plating, the sodium sulfate
that forms can be crystallized by lowering the bath
temperature to 41-50oF (Durney 1984). The crystals can
then be removed by filtration.
IMPROVE RINSE EFFICIENCY
Most hazardous waste from a printed circuit board
manufacturing plant comes from the treatment of
was tewatergeneratedbytherinsing operations thatfollow
cleaning,plating,stripping,andetchingprocesses(Couture
1984). Three basic strategies are used to provide adequate
rinsingbetweenvariousprocess bath operations. Theseare
(1) turbulence between the workpiece and the rinse water,
(2) sufficient contact time between the workpiece and the
rinse water, and (3) sufficient volume of water during
contact time to reduce the concentration of chemicals
rinsed off the workpiece surface (USEPA 1982a). The
third strategy is most commonly employed by printed
circuit board manufacturers. Reliance on this strategy
causes printed circuit board manufacturers to use
significantly more rinse water than is actually required
(Couture 1984).
Many techniques are available that can improve the
efficiency of a rinsing system and reduce the volume of
rinse water used. These techniques include:
Use of closed-circuit rinses. As mentioned above,
installing one or more closed-circuit still or counter-flow
rinsing tanks immediately after a plating bath allows for
metal recovery and lowered rinse water requirements. The
contents of the rinses are used to replenish the upstream
plating bath. As previously mentioned, a major problem
with the use of still rinses is that while they are commonly
installed at many plants, operators typically do not return
the solution to the bath due to concern over solution
contamination.
Generally, the use of a drag-out or still rinse tank can
reduce both rinse water usage and chemical losses by 50
percentormore (USEPA 1982a). Assumingthatachemical
bath processes 3,000 square feet of board each month, the
total volume of process bath drag-out loss each month
would be 12 gallons, with a drag-out rate of 15 ml/square
footof board. If therinse system followingtheprocessbath
operates at a flow rate of 10 gpm for a total of two hours
each day, water usage would be 24,000 gallons per month
based on 20 work days per month. A 50 percent reduction
in process bath chemical loss and water usage achieved by
installing a drag-out tank wouldreduceprocess bath losses
by six gallons per month and water usage by 12,000
gallons.
Use spray rinsing. Although sprayrinsinguses between
one-eighth and one-fourth the volume of water that a dip
rinse uses (USEPA 1982a), it is not always applicable to
printed circuit board manufacturing because the spray
rinse may not reach many parts of the circuit board.
However, spray rinsing can be performed along with
immersion rinsing. This technique uses a spray rinse as the
first rinse step after the workpieces are removed from the
process tank. The spray rinsing typically takes place while
the parts are draining above the process tank. This permits
lower water flows in the rinse tank because spray rinsing
removes much of the drag-out before the workpiece is
submerged into the dip rinse tank.
Use fog nozzles. A variation on the spray nozzle is the
fog nozzle. A fog nozzle employs water and air pressure
to produce a fine mist Much less water is needed than with
aconventionalspraynozzle. It ismoreoften possible to use
a fog nozzle rather than a spray nozzle directly over a
heated plating bath to rinse the workpiece, because less
water is added to the process bath using the fog nozzle.
Increase degree of agitation. Agitation between the
workpiece and the rinse water can be performed either by
moving the workpiece rack in the water or by creating
turbulence in the rinse water. Since most printed circuit
board manufacturing plants operate hand rack lines,
operators could easily move workpieces manually by
agitating the hand rack. However, the effectiveness of this
system depends on cooperation from the operator.
Agitating the rinse tank by using forced air or water is the
most efficient method for creating effective turbulence
during rinse operations. This is achieved by pumping
either air or water into the immersion rinse tank rinsing
operations. Air agitation provides the best rinsing because
the air bubbles create the best turbulence for removing the
chemical process solution from the workpiece surface
(USEPA 1982a). This type of agitation can be performed
by pumping filtered air in to the bottom of the tank through
a pipe distributor (air sparger). Great care should be
exercised, however, to ensure that the air is free of dust or
oil so as not to contaminate the boards being cleaned.
Assuming the plant has a sufficient quantity of compressed
air onsite that is readily available, the cost of installing air
spargers is $100 to $125 per tank for a 50 gallon capacity
tank.
Use counter current rinse stages. Multiple stage rinse
tanks increase contact time between the workpiece and the
rinse solution and thereby improve rinsing efficiency
compared to a single-stage rinse. If these multiple tanks are
set up in series as a counter current rinse system, water
18
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usage can also be reduced. Manufacturers do not need to
rely on large volumes of rinse water to prevent chemical
concentrations in the rinse solution from becoming
excessive. Multiple rinse tanks can be used to provide
sufficient rinsing while significantly reducing the volume
of rinse water used. A multistage counter current rinsing
system can use up to 90 percent less rinse water than a
conventional single-stage rinse system (Couture 1984).
The effectiveness of a multistage system in reducing
rinse water usage is illustrated in the following example. A
plant operates a process line where approximately 1.0
gallon of drag-outper hour results from a chemical process
bath. This process bath is followed by a single-stage rinse
tank. The process requires a dilution rate of 1000 to 1 to
maintain acceptable rinsing in the tank. Therefore, the
flow rate through the rinse tank is 1000 gal/hr. If adouble
stage counter current rinse system were used, arinse water
flowrate of only 30 to 35 gal/hr wouldbe needed. If atriple
stage counter current rinse system were used, only 8 to 12
gal/hr would be required (Watson 1973).
A multistage counter current rinse system allows
greater contact time between the workpiece and the rinse
water, greater diffusion of process chemicals into the rinse
solution, and more rinse watertocomeintocontactwith the
workpiece. Thedisadvantageofmultistagecountercurrent
rinsingisthatmoreprocess steps arerequiredandadditional
equipment and work space are needed. A counter current
triple-rinsesystemrequires the installation of twoadditional
rinse tanks and the associated piping. The cost of such a
system is typically about $1,000 (Terran 1987).
Proper equipment design/operation. Printed circuit
board manufacturers can use excessive amounts of rinse
water if their water pipes are oversized or if the water is left
on even when the rinse tanks are not being used. Rinse
water control devices can be installed to increase the
efficiency of a rinse water system. Flow restrictors limit
the volume of rinse water flowing through arinse system.
These are used to maintain a constant flow of fresh water
into the system once the optimal flow rate has been
determined. Also, since most small and medium-sized
printed circuit board manufacturers operate batch process
lines in which rinse systems are manually turned on and off
throughout the day, pressureactivated flow control devices,
such as foot pedal activated valves, can be helpful for
assuring that the water is not left on after the rinse operation
is completed. If the water lines are over-sized at a plant,
pressure-reducing valves can be installed upgradientof the
rinse water influentlines. This is also helpfulforcontrolling
water use in the rinse tanks.
A conductivity probe or pH meter can also be employed to
control fresh water flow through a rinse system. A
conductivityfcHcell is used to measure the levelof dissolved
solids or hydrogen ions in the rinse solution. When this
level reaches a pre-set minimum, the conductivity probe
activates a valve that shuts off the flow of fresh water into
the rinse system. When the concentration builds to the pre-
set maximum level, the probe again activates the valve,
which then opens to continue the flow of fresh water. This
control equipment is especially valuable to the printed
circuitboardmanufacturingindustry. ApHmeterequipped
with the necessary control valves and solenoids could cost
approximately $700 per tank (Ryan 1987).
Use deionizedwaterfor rinsing. Natural contaminants
found in water usedfor production processes can contribute
to the volume of waste generated. During treatment of
wastewater, these natural contaminants precipitate as
carbonates and phosphates and contribute to the volume of
sludge (USEPA 1982b). The extent to which these
contaminants increase sludge volume depends on the
hardness of the rinse water. In addition to the direct effect
on sludge volume, the presence of natural contaminants in
the water may reduce rinse water efficiency and the ability
to reuse/recycle rinse water. Therefore, rinse systems may
require more water than would be necessary if the water
were pretreated.
The cost of deionizing process water depends on the
condition of the water supplied to the plant The cost is
dependent on the concentration of total dissolved solids
(TDS) in the water (Prothro 1987). For example, in the
Santa Clara Valley a plant supplied with surface water
spends approximately 2 cents per gallon to pretreat process
water. A plant supplied with ground water spends close to
4 cents per gallon. A typical deionizing system that
includes two 14-inch mixed bed deionizers costs
approximately $2,000 for equipment and installation and
treats up to 5,000 gallons a day (Prothro 1987).
RECOVERY/REUSE OF SPENT MATERIALS
Recycling andresourcerecovery includes technologies
that use waste as raw material for another process or that
recover valuable materials from a waste stream before the
waste is disposed of. Opportunities for both the direct use
of waste materials and the recovery of materials from a
waste stream are available to the printed circuit board
manufacturing industry. Many of the spent chemical
process baths and much of the rinse water can be reused for
other plant processes. Also, process chemicals can be
recovered from rinse waters, and valuable metals such as
copper can be recovered from waste streams.
A printed circuit board manufacturer must understand
the chemical properties of its waste stream before it can
assess the potential for reusing the waste raw material.
Although the chemical properties of aprocess bath or rinse
19
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water solution may become unacceptable for their original
use, these waste materials can still be employed in other
applications. Printed circuit board manufacturers should
therefore evaluate waste streams for properties that make
them useful as well as properties that render them waste.
Segregate Streams to Promote Recycling
In a typical facility, the mixing of different rinse
streams is not uncommon, and in the recent past, rinse
waters and spent baths were frequently mixed and treated
together. By segregating various rinses, their reuse or
recycling can be promoted. Metal reclamation by
electrolysis from various streams is made easier if they are
not mixed.
Recover Metal Values from Bath Rinses
In the past, copper and other metal recovery from
printed circuit board manufacturing has not proven to be
economical. However, effluent pretreatment regulations
have made the cost of treatment an economic factor. Also,
thecostofmanagementof sludges containing heavy metals
has increased significantly because of the increased
regulatory requiiementsplacedonthehandlinganddisposal
of hazardous wastes. As a result, board manufacturers may
now find it economical to recover copper and other metals
and metal salts lost due to drag-out from process chemical
baths.
Recoveredmetalcanbeusedin two ways: (l)recovered
metal salts canberecirculatedback into process baths, and
(2) recovered elemental metal can be sold to a metals
reclaimer. Some of the technologies that are being
successfullyused to recovermetalsandmetal salts include:
Evaporation. Waste rinse water is evaporated by
heating, leaving behind a concentrated solution. The
equipment used includes single or multiple effect
evaporators. Vapor recompression applications have also
beenreported(SeaburgandBacchetti 1982). In evaporative
methods, the solution is concentrated until its metal
concentration is equal to that of the plating bath, and then
this solution is reused. Using this method, 90-99 percent
efficient metal recoveries can be achieved (Clark 1984).
Depending on the design, the evaporated water vapor can
either be condensed and re-used as rinse water, or it can be
' vented off into the atmosphere (Campbell and Glenn
1982). Evaporation is the best established of all the metal
recovery techniques used in electroplating. Although it is
themostenergy intensiverecovery technique, its simplicity
andreliabilitymakeitanattractiveoptionformetalrecovery.
In orderforevaporation to be economical, multiple counter
current rinse tanks or spray/fog rinsing should be used to
minimize the amount of rinse water being processed
(MDEM 1984). Apart from the energy cost, a distinct
disadvantage of evaporative techniques is that the
concentrates may also contain the calcium and magnesium
salts originally present in the rinse water. Adding them to
theplatingsolutionmayresultinitsmorerapiddeterioration.
This problem is alleviated in situations where rinse water
is de-ionized or softened prior to use.
Reverse osmosis. Reverse osmosis is also used to
recover drag-out that can be returned to the process bath.
The reverse osmosis process employs a semipermeable
membrane that .permits only certain components to pass
through. When pressure is applied, these components pass
through the membrane and concentrate in the recovered
solution. Although the technology is designed to recover
drag-out, some materials (such as boric acid) can not be
fully recovered and are, therefore, returned to the process
bath at a lower concentration. Also, reverse osmosis is a
delicate process that is limited by the ability of the
membranes to withstand pH extremes and long-term
pressure. Reverse osmosis systems are commonly used to
recover nickelplating solutions andregeneraterinse waters.
Liquid membranes. Liquid membranes are composed
of polymeric materials loaded with anion-carrying solution
(Basta 1983). Liquid membranes have been used to
remove chromium from rinse waters and spent etching
baths. Chromium in the form of dichromate is drawn
across the membrane, forming a tertiary amine metal
complex. This complex is then broken down on the other
side of the membrane with sodium hydroxide solution.
Ion exchange. Ion exchange concentrates metals from
a dilute rinse stream onto a resin material. As rinse water
is passed through a bed containing the resin, the resin
substitutes ions for inorganics in the rinse water. The
metals are then recovered from the resin by cleaning it with
an acidor alkalinesolution. lonexchange units can be used
effectively on dilute waste streams and are less delicate
than reverse osmosis systems. However, the equipment is
complex and requires careful operating and maintenance
practices.
Electrolytic recovery. This method recovers only the
metallic content of rinse water. The process requires a
cathode and an anode placed in the rinse solution. As
current passes from the anode to the cathode, metallic ions
deposit on the cathode. This type of system generates a
solidmetallicslabthatcanbereclaimedorusedasananode
in an electroplating tank. Electrolytic systems can recover
90 to 95 percent of the available metals. Electrolytic
recovery has been successfully used to recover gold, silver,
tin, copper, zinc, solder alloy, and cadmium (Campbell and
Glenn 1982). One great advantage of the electrolytic
method over other metal recovery techniques is that it
recovers only the plating metal, not the impurities, from the
waste rinse water. Electrolytic metal recovery is most
20
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efficient on concentrated solutions. For solutions with less
than 100 mg/1 of the metal ion, low current efficiencies
limit process effectiveness.
Electrodialysis. In electrodialysis, an electric current
and selective membranes are used to separate the positive
and negative ions from a solution into two streams. This is
accomplished by feeding a solution through a series of
alternating cation and anion selective membranes, through
which a current is passed. Electrodialysis is used mainly to
concentrate dilute solutions of salts or metal ions.
Electrodialysis can remove nickel, copper, cyanide,
chromium, iron and zinc from waste rinse water (MDEM
1984, Kohl and Triplett 1984). This technology has not
been used as widely in the electroplating industry as have
other metal recovery techniques (Campbell and Glenn
1982, Kohl and Triplett 1984).
Highsurfaceareaelectrowinningfelectrorefining. This
method operates on the same principle as electrolytic
recovery. Themetal-containingsolution is pumped through,
and plates out on, a carbon fiber cathode (Mitchell 1984).
To recover the metals, the carbon fiber cathode assembly
is removed and placed in an electrorefiner, which reverses
the current, removes the metals from the carbon fibers, and
allows them to plate onto a stainless steel starter sheet.
These systems can be used to recover a wide variety of
metals and to regenerate many types of solutions.
The cost associated with implementing a chemical
recovery technology depends on anumber of variables: the
size of the unit, the space available, equipment
rearrangement, production down time, and the specific
application. Table 4 contains cost data for several chemi-
cal recovery units from electroplating plants. Although the
specific materials recovered may be different for a printed
circuit board manufacturing plant, the basic technology is
transferable between these two industries. While the
equipment costs shown can be applied to board manufac-
turing, the annual savings depend on the wastewater metal
concentrations and volume of wastewater treated by the
recovery systems.
One limiting factor for a small printed circuit board
manufacturing company is the volume and chemical
concentration of its various rinse water effluents. The
examples in Table 4 are all designed to recover a specific
material from asingle waste generating source (for example,
nickel salts from a nickel plating line). To achieve savings
in chemicals and sludge handling that create a justifiable
payback, the waste stream must be fairly concentrated and
continuous. Eachcompanymustevaluateitsown conditions
to determine the feasibility of material recovery. The
information necessary to determine the feasibility includes
waste stream generationrates and chemical concentrations,
and the value of materials to be recovered.
Etching .
Most of the source control techniques listed under
plating and electroplating apply as well to waste produced
by etching. Special source reduction methods associated
with etching operations are discussed below.
Use differential plating instead of the conventional
electroless plating process. If the concentrations of certain
stabilizers in the electroless copper bath are controlled,
copper deposits three to five times faster on the through-
hole walls than on the copper cladded surface (Poskanzer
and Davis 1982). This reduces the amount of copper that
mustbe subsequently etched away in the subtractive method.
The use of differential electroless plating has not been
reportedbyprinted'ckcuitboardmanufacturerSjanditmay
require significant developmental work before
commercialization is possible.
Use non-chelatedetchants. Non-chelatemildetchants
such as sodium persulfate and hydrogen peroxide/sulfuric
acid can be used to replace ammonium persulfate chelate
etchanL
Use thinner copper foil to clad the laminated board.
This change reduces the amount of copper which must be
etched, and thus reduces the amount of waste generated
from the etching process. Printed circuit board
manufacturers are switching to boards cladded with thinner
copper as their starting materials.
Use pattern instead of panel plating. Since panel
plating consists of copper plating the entire board area,
while pattern plating requires copper electroplating only
the holes and circuitry, the use of the latter technique
reduces the amount of non-circuit copper which must be
subsequently etched away. This practice can therefore
reduce the amount of waste generated from the etching
operation. The switch from panel to pattern plating has
been made by a large number of printed circuit board
manufacturers. Customers demanding applications for a
uniform cross section of circuitry in computer and
microwave printed circuit boards, however, may dictate
the use of panel plating to provide highly uniform copper
thickness.
Use additive instead of subtractive method. This
change eliminates the copper etching step, and therefore
eliminates the generation of substantial volumes of spent
etchant as well as reducing the amount of metal hydroxide^
sludges generated. Although the subtractive method is still
the most widely used in the manufacturing of printed
circuit boards, the additive method is gaining in popularity
since it results in less waste and lower manufacturing costs
(Brush 1983). A noted drawback to the additive method,
however, is therequirementfor solventprocessableinstead
21
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Table 4. Costs of Technology for Material Recovery
Materials
Technology Recovered
Rinse water
Chromic acid
Nickel salt
Plating chemicals
Evaporation Unit:
Capacity of'
approximately
20 gph.
Reverse Osmosis
Unit: Capacity of
approximately 100 gph.
Ion Exchange Unit: . Rinse water
Capacity of Chromic acid
approximately 20 gph.
Electrolytic Unit: Rinse water
Capacity of Copper
approximately 15 gph.
Equipment costs include equipment purchase, installation, and materials.
Source: USEPA1987.
Equipment
Costs'
$47,000
$27,000
$38,000
$25,000
ofaqueousprocessablephotoresists.Furthermore,thespent
additive plating bath often contains heavily complexed
copper which may result in waste treatment problems.
Use non-chrome etchants. Whenever possible, ferric
chloride or ammonium persulfate solution should be used
instead of chromic-sulfuric acid etchants. Non-chromium
etchmgsolutionhasreportedlybeenusedbyprinted circuit
board manufacturers in an effort to reduce the toxicity of
the waste generated.
Recycle spent etchants. Use of an electrolytic
diaphragm cell for regenerating spent chromic acid from
etching operations has been reported (AESI1981). The
electrolytic cell oxidizes trivalent chromium to hexavalent
chromium and removes contaminants. The quality of the
regenerated etchant has been reported to be equal to or
better than fresh etchant
In one such application, extensively tested at the U.S.
Bureau of Mines in Rolla, Mo., copper etching solution
was regenerated andmetallic copper recovered at the same
time.Recovery was accomplishedby depositing thecopper
onto the cathode of the electrolytic diaphragm cell (Basta
1983).
Another recycling example involves the regeneration
of cupric chloride, used as a strong etchant for producing
circuit patterns on circuit board base material. The etchant
becomes spent as the copper etched from the base material
reduces the cupric chloride (CuC12) to cuprous chloride
(CuCl). This spentetchantcan be regeneratedby oxidizing
to cuprous chloride through direct chlorination (Couture
1984).
Wastewater Treatment
Process chemical loss due to drag-out is the most
significant source of chemicals entering wastewater.
Treatmentof this wastewaterisamajor source of hazardous
waste in PC board operation because of the resulting
sludge. The volume of sludge generated is proportional to
the level of contamination in the spentrinse water (Couture
1984). The major ways of reducing waste associated with
treatment (in addition to those associated with drag-out
reduction, reduction in the use of rinse water, and use of
deionized water) include waste stream segregation, use of
alternative treatment chemicals, and alternative treatment
technologies.
WASTE STREAM SEGREGATION
Segregating waste streams can improve the efficiency
of a waste treatment system. An example of waste stream
segregation is the separation of chelating agent waste
streams from nonchelating agent streams. Since most
small printed circuit board manufacturing plants use
treatment systems that can be operated as a batch process,
they can implement waste stream segregation and selective
treatment with minimal impact on the production system.
The main drawback to this alternative is usually the limited
storage capacity for the segregated waste streams.
If wastestreamscontainingchelatingagents are treated
in a batch process separately from other waste streams, the
22
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use of ferrous sulfate to break down the chelators can be
minimized. Since thedron in ferroussulfate will precipitate
out in the sludge, reduction in its use will also reduce the
volume of sludge generated.
By isolating cyanide-containing waste streams from
waste streams containing iron or complexing agents, the
formation of cyanide complexes is avoided, and treatment
mademuch easier (Dowd 1985). Segregationof wastewater
streams containing different metals also allows for metals
recovery or reuse. For example, by treating nickel-plating
wastewater separately from other waste streams, a nickel
hydroxide sludge is produced which can be reused to
produce fresh nickel plating solutions.
Another waste alternative is to separate noncontact
cooling water from industrial wastes. It is likely that this
cooling water can bypass the treatment system and be
discharged directly to the sewer because it does not come
in contact with process chemicals. This practice can
reduce wastewater volume and, as a result, reduce the
amount of treatment chemicals used. Also, acidic or
alkaline waste streams that do not contain metals can
simply be neutralized prior to discharge; therefore, if they
are segregated from other wastes thatrequiremetalremoval,
the volume of treatment chemicals can be reduced. This,
in turn, will reduce the volume of sludge generated.
USE OF ALTERNATIVE WASTE TREATMENT
CHEMICALS
The selection of chemicals used in the waste treatment
process can affect the volume of sludge generated. This
selection should, therefore, consider a chemical's effect on
sludge generation rates. For example, lime and caustic
soda are two common chemicals used for neutralization
and precipitation. Although lime costs less per unit of
neutralizing capacity, it can produce as much as ten times
more dry weight of sludge than caustic soda (USEPA
1982b).
Alum and ferric chloride are commonly employed as
coagulating agents to improve floe formation. When used,
they convert to hydroxides and contribute to the volume of
sludge. Polyelectrolyte conditioners can also be used as
coagulants, but they are more expensive than inorganic
coagulants. However, polyelectrolytes do not add to the
quantity of sludge and may actually be less expensive
overall when considering waste handling costs. One
printed circuit board manufacturer visited during this study
recently switched from alum to apolyelectroly te coagulant
in order to reduce sludge generation. Specific data on the
volume of sludge reduction are not yet available from the
company.
The selection of alternative treatment chemicals
depends on specific waste characteristics and removal
efficiency needs for a particular treatment facility. The
potential use of various treatment chemicals should be
discussed with chemical manufacturers' representatives
and experimented with to determine their effectiveness.
ALTERNATIVE WASTEWATER TREATMENT -
ION EXCHANGE
Ion exchange systems can be employed to treat the
entire wastestream prior to discharge to the publicly-
owned treatment works. When used for this purpose, the
ion exchange units do not recover process chemicals for
reuse because all sources of wastewater are mixed prior to
treatment. The units can be used to recycle rinse water,
however, by utilizing an activated carbon treatment system
following ion exchange treatment. The costs for operating
an ion exchange system depend on the volumeand chemical
concentrations of the wastewater.
One plant visited recently installed an ion exchange
system toreplaceitsconventionalprecipitation/clarification
treatment system. The ion exchange unit is designed for a
treatment capacitybf 12 to 14 gallonsper minute. The unit
does not generate any sludge but does generate
approximately two 55-gallon drums of spent ion exchange
resin each month. The old treatment system generated
approximately four to six 55-gallon drums of sludge per
month.
The ion exchange system was purchased and installed
for approximately $16,000 and required one week of
production down time to install. The system costs $1,000
per month to operate, including material purchases and
waste disposal, compared to $1,500 per month for the old
system. Thenew system also requiresless labor to maintain
it. The payback on investment for the new system is
estimated to be 3.3 years.
References
AESI. 1981. American Electroplater's Society, Inc.
Conference on Advanced Pollution Control for the
Metal Finishing Industry (3rd) held at Orlando Hyatt
House, Kissimmee, Florida on April 14-16, 1980.
EPA-600-2/81-028. Cincinnati, Ohio: U.S.
Environmental Protection Agency.
Anonymous. 1983. California-style circuit manufacturing
using computerization. Plat. Surf. Finish. 70: 26-9.
ASM. 1987. Metals Handbook, Ninth Edition, Volume 5:
Surface Cleaning, Finishing, arid Coating. American
Society for Metals. Metals Park, Ohio.
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Basanese. J. 1987. West General Associates, personal
communication with T. Adkisson, Planning Research
Corporation (February 1987).
Basta,N. 1983. Totaimetalrecycleismetalfinishers'goal.
Chemical Engineering. Augusts, 1983. pp. 16-19.
BCL, 1976. Battelle Columbus Lab. Assessment of
IndustrialHazardousWastePractices:Electroplating
and Metal Finishing Industries Job Shops. EPA-530-
SW-136C. Washington, D.C.: U.S. Environmental
Protection Agency.
Bowlby, R. 1985; The DIP may take its final bows! IEEE
Spectrum, June. 1985. pp. 37-42.
Brush, P.N. 1983. Fast track for printed circuit boards.
Prod. Finish. November 1983, pp. 84-5.
Campbell, MJE, and WJM Glenn, 1982. Proven Profit
From Pollution Prevention. Toronto, Canada: The
Pollution Probe Foundation.
CDHS. 1986. Guide to Solvent Waste Reduction
Alternatives. Final report preparedbylCF Consulting
Associates,Inc.,forAltemativeTechnologyandPolicy
Development Section, Toxic Substances Control
Division, California Department of Health Services.
October 1986.
Cheremisinoff,PJM.,AJ.Peina,andJ.Ciancia. 1976. Ind.
Wastes. 22(6):31-4.
Clark, R., ed. 1984. Massachusetts Hazardous Waste
Source Reduction. Conference Proceedings, October
17,1984. Boston, Mass.: Massachusetts Department
of Environmental Management
Cook,T.M.,MJLCubbage,andL.J.Fister. 1984. Draining
process solutions from sheets, baskets, pipes, threads
and fins. Metal Finishing, (7): 33.
Couture, S.D. 1984. Source Reduction in the Printed
Circuit Industry. Proceedings - the Second Annual
Hazardous Materials Management Conference,
Philadelphia, Pennsylvania, June 5-7,1984.
Dowd, P. 1985, Conserving water and segregating waste
streams. Plat. Surf. Finish. 72(5): 104-8.
Dumey, LJ., ed. 1984. Electroplating Engineering
Handbook, 4th ed. New York, N.Y.: Van Nostrand
ReinholdCo.
Engelmaier,W.,andD.C.Frisch. 1982. Injection molding
shapes new dimensions for boards. Electronics.
December 15. pp. 155-158.
Engles, K.O., and J.T. Hamby. 1983. Computerized
controller for electroplating printed wiring boards.
Met. Finish. 81: 95-100.
Foggia, M. 1987. Shipley Company, Inc., personal
communication with T. Adkisson, Planning Research
Corporation (January 21,1987).
Greene, R.,ed. 1985. CE Alert, New Technology. Chem.
Eng. March 4. pp. 85.
Gunderson, R., and H. Holden. 1983. CAM techniques
improve circuit board production. Control. Eng. 30:
141-2. ' '
Kohl, J., and B. Triplett. 1984. Managing and Minimizing
Hazardous Waste Metal Sludges. North Carolina State
University.
Lane,C. 1985. Fluorocarbpn coating eliminates corrosion
of acid bath racks, Chem. Process. 48(10): 72.
Lyman.J. 1984. Surfacemounting alters the printed circuit
board scene. Electronics. February 9,1984.
LWVM. 1985. Waste Reduction - The Untold Story.
Proceeding of a seminar at the National Academy of
Sciences Conference Center on June 19-21, 1985.'
Wood Hole, Mass.: The League of Women Voters of
Massachusetts.
Mathews, J.E. 1980. Industrial reuse and recycle of
wastewater: literature review. Robert S. Kerr
Environmental Research Lab. EPA-600-2-80-183.
Ada, Okla: U.S. Environmental Protection Agency.
McRae, GJ7. 1985. In-process waste reduction: part 1.
Plat. Surf. Finish. 72(6): 14.
MDEM. 1984. 'Massachusetts Hazardous Waste Source
Reduction: Metallic Waste Session. Conference
proceedings May 23, 1984. Boston, Mass.:
Massachusetts Department of Environmental
Management.
Meltzer, MP. 1989. Reducing Environmental Risk:
Source Reduction for the Electroplating Industry.
Doctoral Dissertation, School of Public Health,
University of California, Los Angeles, CA.
Mitehel,G.D. 1984. A Unique Method for the Removal
andRecovery of Heavy MetalsFrom the Rinse Waters
in the Metal Plating and Electronic Interconnection
Industries. Proceedings - Massachusetts Hazardous
Waste Source Reduction, Clinton, Massachusetts.
Olsen, A.E. 1973. Upgrading Metal Finishing Facilities to
Reduce Pollution. Oxy Metal Finishing Corp., EPA-
625-3-73-002, Washington,D.C.:U.S.Environmental
Protection Agency.
-------
Poskanzer, A.M. 1983. Plating printed circuit substrates:
circuit topics. Plat. Surf. Finish. 70:10.
Poskanzer, A.M., and S.C. Davis. 1982. An efficient
electroless plating system for printed circuitry. Plat.
Surf. Finish. 69: 95-7.
Prothro, J. 1987. Culligan Industrial Water Treatment,
personal communication with T. Adkisson, Planning
Research Corporation (March 16,1987).
Ryan, W.M. 1987. William M. Ryan Company, personal
communication with T. Adkisson, Planning Research
Corporation (January 14,1987).
Seaburg, J.L., and J.A. Bacchetti. 1982.
Processing 45(12): 30-31.
Chemical
Stone, P. 1987. Shipley Company, Inc., personal
communication with T. Adkisson, Planning Research
Corporation (February 24,1987).
Terran, A. 1987. Advanced Process Machinery, personal
communication with T. Adkisson, Planning Research
Corporation (January 14,1987).
USEPA. 1981. U.S. Environmental Protection Agency,
Industrial Environmental Research Lab. Changes for
Metal Finishers. Cincinnati, Ohio.
USEPA. 1982a. Control and Treatment Technology for
theMetalFinishinglndustry-In-plantChanges.EPAX
8606-0089.
USEPA. 1982b. Environmental Pollution Control
Alternatives: Sludge Handling, Dewatering, and
DisposalAlternativesfor the Metal Finishinglndustry.
EPA 625/5-82/018.
USEPA. 1983. U.S. Environmental Protection Agency,
Office of Water Regulations and Standards.
Development Document for Effluent Limitation
Guidelines and Standards for the Metal Finishing
Point Source Category. EPA-440-1-83-091.
Washington, D.C.
USEPA. 1986. Waste Minimization-Issuesand Options,
vol II. PB 87-114369. Prepared by Versar, Inc. and
Jacobs Engineering Group Inc.
USEPA. 1987. Environmental Pollution Control
Alternatives: Reducing Water Pollution Control Costs
in the Electroplating Industry. September 1987. EPA
625/5-85/016.
USEPA. 1989. Waste Minimization in Metal Parts
Cleaning. August 1989. EPA/530-SW-89-049.
USEPA. 1990. Guides to Pollution Prevention: The
Commercial Printing Industry.
Versar, Inc. 1984. Technical Assessment of Treatment
Alternatives for Wastes Containing Metals and/or
Cyanides. Contractno. 68-03-3149, final draftreport
for U.S. Environmental Protection Agency.
Springfield, Va.: Versar, Inc.
Watson, M.R. 1973. PollutionControlinMetalFinishing.
Noyes Data Corporation, Park Ridge, New Jersey.
Wynschenk, J. 1983. Electroless copper plating chemistry
and maintenance. Plat Surf. Finish. 70:28-9.
25
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SECTION 4
GUIDELINES FOR USING THE WASTE
MINIMIZATION ASSESSMENT WORKSHEETS
Waste minimization assessments were conducted at
several printed circuit board manufacturing plants in
California. The assessments were used to develop the
waste minimization questionnaire and worksheets that are
provided in the following section.
A comprehensive waste minimization assessment
includes aplanning and organizational step, an assessment
step that includes gathering background data and
information, a feasibility study on specific waste
minimization options, and an implementation phase.
Conducting Your Own Assessment
The worksheets provided in this section are intended
to assist printed circuit board manufacturers in
systematically evaluating waste generating processes and
in identifying waste minimization opportunities. These
worksheets include only the assessment phase of the
proceduredescribed in the Waste Minimization Opportunity
Assessment Manual. For a full description of waste
minimization assessment procedures, refer to the EPA
Manual.
Table 5 lists the worksheets that are provided in this
section.
26
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Table 5. List of Waste Minimization Assessment Worksheets
Number Title Description
1. Waste Sources
2A. Waste Minimization:
Material Handling
2B. Waste Minimization:
Material Handling
2C. Waste Minimization:
Material Handling
3. Option Generation:
Material Handling
4. Waste Minimization:
Material and Process Substitution
5. Option Generation:
Material and Process Substitution
6A. Waste Minimization:
Process Modification
6B & 6C. Waste Minimization:
Process Modification
7. Option Generation:
Process Modification
8. Waste Minimization:
Good Operating Practices
9. Option Generation:
Good Operating Practices
10A. Waste Minimization: Segregation,
Reuse, Recovery and Treatment
10B. Waste Minimization: Segregation,
Reuse, Recovery and Treatment
Typical wastes generated at
printed circuit board manufacturing plants.
Questionnaire on general handling
techniques for raw material handling.
Questionnaire on procedures used
for bulk liquid handling.
Questionnaire on procedures used
for handling drums, containers and packages.
Waste minimization options for
material handling operations.
Questionnaire on material and
process substitutions.
Waste minimization options for
material and process substitution.
Questionnaire extending process bath
life by reducing drag-in and drag-out.
Questionnaire on: 1) extending bath life
by avoiding decomposition and impurity
removal; and 2) improving rinse efficiency.
Process modification waste minimization
options.
Questionnaire on use of good
operating practices.
Waste minimization options for
good operating practices.
Questionnaire on opportunities for
segregation and reuse of wastes.
Questionnaire on opportunities
for recovery and treatment of wastes.
27
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Firm Wast* Minimization Assessment Prepared By
fiiio Checked By
pa jo Prnj NO Sheet of Pace ol
WORKSHEET WASTE SOURCES
Waste Source: Material Handling
Off-spec materials
Obsolete raw materials
Spills & leaks (liquids)
Spills (powders)
Empty container cleaning
Container disposal (metal)
Container disposal (paper)
Pipeline/tank drainage
Laboratory wastes
Evaporative losses
Contaminated wipes and gloves
Othsr
Wast* Source: Process Operations
Board Scrap
Board Cleaners
Catalysts
Electroless Plating Baths
Photoresist
Developers
Copper Plating Baths
Tin/Lead Plat*
Stripping Solutions
Etching Solutions
Nickel/Gold Electroplate
Reftow Oil
Rinsing
Equipment Cleaning
Other
Significance at Plant
Low
Medium
High
,,
28
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Firm Waste Minimization Assessment |
Sita (
Date Prnj t^ !
WORKSHEET WASTE MINIMIZATION:
2 A Material Handling
A. GENERAL HANDLING TECHNIQUES
Does the plant accept samples from chemical suppliers?
Oo unused samples become waste?
Are suppliers required to take back unused samples they provide?
Are all raw materials tested for quality before being accepted from suppliers?
Describe safeguards to prevent the use of materials that may generate off-spec f
arepared By
Checked Bv
Sheet of Pace of
-
D yes O no
Q yes D no
O yes Ono
D yes a no
Mnriiirf
Is obsolete raw material returned to the supplier?
Is inventory used in first-in first-out order?
Is the inventory system computerized?
Does the current inventory control system adequately prevent waste generation?
What information does the system track?
Dyes D no
Dyes Dno
Dyes Dno
Dyes dno
Is there a formal personnel training program on raw material handling, spill prevention,
proper storage techniques, and waste handing procedures? D yes D no
Does the program include information on the safe handling of the types of drums, containers
and packages received? Dyes Gno
How often is training givan and by whom?
.-.
Describe spill containment used in material storage ares-
29
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Firm Waste Minimization Assessment
SrlB 1
DaiB . Prnj Wn
WORKSHEET WASTE MINIMIZATION:
2B Material Handling
3repared By
Checked By
Sheet of Page of
B. BULK LIQUIDS HANDLING
What safeguards are in place to prevent spills and avoid ground contamination during the filling of storage tanks?
High level shutdown/alarms CD Secondary containment G
Flow totalizers with cutoff n Other n
Describe the system?
Are air emissions from solvent storage tanks controlled! by means of:
Conservation vents
Nitrogen blanketing
Adsorber/Absorber/Condenser
Other vapor loss control sytem
Describe the system!
D yes a no
D yes n no
D yes a no
D yes D no
Are all storage tanks routinely monitored for leaks?
Describe procedure and monitoring frequency for above-ground/vaulted tanks:
n yes n no
Underground tanks?
How are the liquids in these tanks dispensed to the users? (i.e., in small contain*
ปr5 or hard niond ^
What measures are employed to prevent the spillage of liquids being dispensed'
>
When a spill of liquid occurs in the facility, what dry cleanup methods are employed (e.g., wet or dry)? Also discuss the
way In which the resulting wastes are handled?
Would different cleaning methods allow for direct reuse or recycling of the waste'
> (explain)-
30
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Firm Waste Minimization Assessment F
Site (
Date pr0j Kfo i
WORKSHEET WASTE MINIMIZATION:
ฃ\s Material Handling
'repared By
Checked By
sheet of Paae of
C. DRUMS, CONTAINERS, AND PACKAGES
Are drums, packages, and containers inspected for damage before being accepted? G yes G no
Are employees trained in ways to safely handle the types of drums & packages received? G yes G no
Are they properly trained in handling of spilled raw materials? G yes G no
Are stored items protected from damage, contamination, or exposure to rain, snow, sun & heat? G yes G no
Describe handling procedures for damaged items:
Does the layout of the facility result in heavy traffic through the raw maten'al storage area? G yes G no
(Heavy traffic increases the potential for contaminating raw materials with dirt or dust
and for causing spilled materials to become dispersed throughout the facility.)
Can traffic through the storage area be reduced? G yes G no
To reduce the generation of empty bags & packages, dust from from dry material handling and
liquid waste due to cleaning of empty raw material drums, has the facility attempted to:
Purchase hazardous materials in preweighed containers to avoid the need for weighing? G yes G no
Use reuseable/recyclable drums with liners instead of paper bags? G yes G no
Use larger containers or bulk delivery systems that can be returned to supplier for cleaning? G yes G no
Discuss the results of these attempts-
Are all empty bags, packages, and containers that contained hazardous materials segregated
from those that contained non-hazardous wastes? G yes G no
Are containers property "cleaned" (per EPA methods)prior to disposal? G yes G no
Describe the method cu^enfy used to dispose of this waste*
31
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Firm Waste Minimization Assessment Prepared av
Silo Prnn Unit/Opar
Checked By
nafa Proi. NO. Sheet of Page of
.
WORKSHEET OPTION GENERATION:
0 Material Handling
Meeting Format (e.g., bralnstormlng, nominal group technique
Meeting Coordinator
)
Meeting Participants
Suggested Waste Minimization Options
A. General Handling Techniques
Quality Control Check
Return Obsolete Material to Supplier
Minimize Inventory
Computerize Inventory
Formal Training
B. Bulk Liquids Handling
High Level Shutdown/Alarm
Flow Totalizers with Cutoff
Secondary Containment
Air Emission Control
Leak Monitoring
Spilled Material Reuse
Cleanup Methods to Promote Recycling
C. Drums, Containers, and Packages
Raw Material Inspection
Proper Storage/Handing
Preweighed Containers
Reusable Drums
Bulk Delivery
Waste Segregation
Currently
Done Y/N?
Rationale/Remarks on Option
32
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Firm Waste Minimization Assessment P
Sifa r.
Date Pmj wn S
WORKSHEET WASTE MINIMIZATION:
A Material and Process
^ Substitution
repared By
hecked By
heet of Page of
To reduce the use of hazardous chemicals and the generation of hazardous wastes, has the
facility attempted to use any of the following methods:
CLEANING AND SURFACE PREPARATION
Abrasives instead of solvents, acids, or alkalis?
Non-chelated cleaning compounds?
PATTERN PRINTING AND MASKING
Aqueous processable resist instead of solvent based resist?
Screen printing instead of photofithography to eliminate need for developers?
Dry photoresist removal methods to avoid use of organic strippers?
ELECTROPLATING AND ELECTROLESS PLATING
Mechanical board production methods?
Non-cyanide process baths?
Non-cyanide stress relievers?
ETCHING
Differential plating instead of conventional etectroless plating?
Pattern instead of panel plating?
Additive instead of subtractive methods?
Non-chelated etchants?
Non-chromated etchants?
WASTEWATER TREATMENT
Alternative (tow dry soids volume) chemicals?
Alternative treatment methods?
Discuss the results of thasa attempts!
Dyes
D yes
Dyes
O yes
Qyes
D yes
a yes
a yes
Dyes
Dyes
a yes
a yes
Oyes
a yes
D yes
a no
a no
Ono
Ono
Ono
a no
D no
a no
a no
a no
a no
a no
a no
Ono
Dno
Discuss the obstacles that prevent the use of these methods:
Not*: Th* auditor should r*f*r to the USEPA report on Wast* Minimization in M*tal Parts Cleaning for information regarding
malarial substitution and process modification aimed at reducing wast* from parts craning.
33
-------
Rrm Waste Minimization Assessment Prepared By
fiita Proc Uni*/ฐp'
ir.
Checked Bv
nafซ Prni Ma Sheet of Paoe of
'
WORKSHEET OPTION GENERATION:
c Material and Processing
** Substitution
Meeting Format (e.g., bralnstormlng, nominal group technique
)
Meeting Participant* , ' ,.
Suggested Waste Minimization Options
A. Substitution Options
Abrasives
Non-chelated Cleaning Compounds
Aqueous Processabfe Resist
Screen Printing
Dry Resist Removal
Mechanical Production
Non-cyanide Process Baths
Non-cyanide Stress Relevers
Differential Plating
Use Thinner Copper Clading
Pattern Plating
Additive Method
Non-chelated Etchants
Non-chrome Etchants
Other Raw Material Substitution
Currently
Done Y/N?
Rationale/Remarks on Option
34
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Firm
Site
Date
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet of Page of
WORKSHEET
6A
WASTE MINIMIZATION:
Process Modification
D no
CD no
Dno
D no
D no
For cleaning, electroplating, electroless plating, and etching, there are many similar ways of reducing waste. This is
because most of these operations involve the insertion and removal of a part from a tank of processing solution followed
by the rinsing of the part in a tank of water. Waste can be reduced by extending process bath life (reduce drag-in, reduce
drag-out, avoid bath decomposition and remove impurities) and by improving rinse efficiency.
A. EXTENDING PROCESS BATH LIFE
Drag-In Reduction
Are racks cleaned regularly to ensure that corrosion does not contaminate the process baths? Q yes
Are coated racks used to avoid contamination? Dyes
Has the plant investigated the use of purer anodes to avoid contamination from
metallic impurities in the anodes? Dyes
Are anode bags used to prevent corroded anodes from falling into the bath? O yes
Are anodes removed when the bath is not in use? Q ves
Is rinsing adequate to prevent or minimize drag-in? G yes
Is detonized water used for process bath make-up? dyes
Are chemicals properly stored and mixed just before use to avoid decomposition and
shortened bath life? Q yes
Drag-Out Reduction
Are process baths operated at the lower end of the manufacturer's suggested range of
operating concentrations? O yes
Are fresh process bath solutions,' operated at a tower concentration than
replenished process bath solutions? Gyes
Can any of the chemical process baths be operated at a higher temperature without
adversely affecting production quality? Dyes
Has the plant investigated the use of wetting agents to reduce drag-out? Gyes
Are boards property racked to avoid excessive drag-out (typical drag-out values
should range from 10 to 1 5 mW?)? Dyes
Are boards withdrawn slowly, and is ample time provided to allow for drainage? Dyes
Has an optimal removal rate and drainage time for workpiece racks been
determined for each process bath? a yes
Are personnel trained to foflow proper workpiece rack removal rates & drainage times?
Would use of an automatic board handler reduce drag-out? dyes
Is there space between process bath tanks and their associated rinse tanks that allows
process chemicals to drip onto the floor? Dyes
If yes, can drain boards be used to direct drainage back into the process tank? Dyes
Do process baths that operate at elevated temperatures utifize drag-out tanks as the initial
rinse following the bath? Dyes
If yes, is the drag-out tank solution added back to the process tank? G yes
Has the company studied the possibility of using the drag-out solution for process Gyes
bath replenishing?
a no
Gno
a no
Gno
a no
a no
Gno
Gno
D no
Gno
a no
a no
a no
G no
Gno
35
-------
pirm Waste Minimization Assessment
SHซ
DatA pr/5j NO
WORKSHEET WASTE MINIMIZATION:
DD Process Modification
Avoiding Bath Decomposition and Impurity Removal
Is bath activity regularly monitored?
Are corrective actions taken promptly to promote maximum bath life?
Is bath temperature properly controlled?
Are heating coils cleaned regularly?
Has the plant used heated jacketed tanks instead of coils?
Are the process baths agitated?
Is agitation achieved by air sparging?
Prepared By
Checked Bv
Sheet of Pace
of
Dyes
D yes
D yes
Q yes
O yes
Dyes
D yes
Could mechanical agttitatton be used to avoid the formation of carbonates due to air agitation? G yes
Are process baths continuously filtered?
Are they batch filtered?
Is sludge build-up in the tank a problem?
Would increased filtering help?
G yes
D yes
G yes
G yes
Can coarser filters be used? (Coarser filters hold more sludge & need replacement less often.) D yes
Is carbon filtering employed?
Has the plant attempted to regenerate/purify solutions by cooling or freezing?
G yes
G yes
Gno
Gno
Gno,
Gno
Gno
Gno
Gno
G no
G no
Gno
Giro
G no
Gno
G no
G no :
Can the recovered solids be used in another process? (Copper sulfate crystals from
regenerated etchant may be used for regenerating copper electroplating baths.)
Does the plant use an alkaline stripper to clean photoresist material off of
printed circuit boards?
Is the stripper decanted or filtered periodically to remove polymer flakes and
Increase the useful life of the stripper?
B. IMPROVING RINSE EFFICIENCY
G yes
G yes
G yes
Gno
Giro
Gno
Can a still rinsa or drag-out tank be employed to recover drag-out and reduce loading on the
rinse system?
G yes
Gno
If recovered drag-out cannot be returned to the process bath, is it treated separately from the"
spent rinse water? " ,
DOBS the plant uas spray or fog rinsing to reduce rinse water use?
G yes
ayes
Gno
Gno
Do all the rinse systems utilize forced air or forced water as a means of agitating
the rinse solution?
G yes
If no, are workplace racks agitated manually white submersed in the rinse solution? G yes
Gno
Gno
Does the plant have the available space to install multiple counter-current rinse tanks at any oft
tho rinsing stations? ;
G yes
Gno
Have the flow rates used on all the rinse systems been determined based on rinsing needs of
the particular process chemistry? (Based on a drag-out value of 15 ml/ft? and a
required dilution
ratio of 1000:1 , a single stage rinse tank should use approximately 4 gallons of rinse per square
foot of board.)
.Gyes
Qno
36
-------
Firm
Site
Date
Waste Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet of Page
of
WORKSHEET
6C
WASTE MINIMIZATION:
Process Modification
B. IMPROVING RINSE EFFICIENCY (CONT.)
Does the sum of each rinse system's estimated daily water usage approximate the average
daily volume of wastewater treated? (If no, rinse water lines are most likely being left on even
when the process line is not in operation.) Q yes D no
Does the plant utilize the flow restrictors, flow control meters, or other devices intended to
regulate the flow of water through all the rinse tanks? O yes D no
Does the plant generate rinse water effluents from rinse operations that follow mild and/or
strong acid etching and cleaning processes? Dyes [3 no
If yes, are the rinse solutions recycled for use in rinse systems following alkaline
cleaning baths? O yes ' D no
Has the plant investigated the use of deionized water for rinsing? O yes ' Q no
Would the use of deionized rinse water promote the potential for recycling? O yes D no
37
-------
Pirm Wast* Minimization Assessment Prepared By
Sifs Proc l,Jnit/Ofwปr
Checked Bv
r>aปn Prซj NO Sheet of Page oซ
1
WOR^HEIT OPTION GENERATION:
/ Process Modification
Meeting formirt (ซ.g., bralnstormlng, nominal group toehhlque)
Meitlng Coordinator
Mettlng Participants ..
Suggested Wast* Minimization Options
A. Extending Process Bath Life
Proper Rack Design/Maintenance
Purer Anodes and Anode Bags
Better Rinsing
Deionized Water
Proper Storage
Lower Bath Concentration
Increase Bath Temperature
Wetting Agents
Proper Board Withdrawal/Drainage
Automation
Recover Drag-out
Monitor Bath Activity
Control Bath Activity
Mechanical Agitation
Fittering/lrnpurfty Removal
B. Improve Rlrwe Efficiency
Still Rinses
Spray Rinsing
Fog Nozzles
Increase Agitation
Counter-current Rinse
Proper Equipment Design/Operation
Reuse/Recycle Rinse
Use Deionlzed Water
Currently
Done Y/tf?
Rationale/Remarks on Option
38
-------
pirrn Wast* Minimization Assessment
Site
Hatfi proj No '
WORKSHEET WASTE MINIMIZATION:
O Good Operating Practices
Prepared By
Shacked Bv
Sheet of Page of
Is the production schedule varied to decrease waste generation? (For example, do you
attempt to increase size of production runs and minimize cleaning by accumulating orders or
production for inventory?) .
D yes p no
Describe
Are plant material balances routinely performed? Dyes Ono
Are they performed for each material of concern (e.g. solvent) separately? O yes EH no
Are records kept of individual wastes with their sources of origin and eventual disposal? O yes Q no
(This can aid in pinpointing large waste streams and focus reuse efforts.)
Are the operators provided with detailed operating manuals or instruction sets? D yes Q no
Are all operator job functions weU defined? Dyes Qno
Are regularly scheduled training programs offered to operators? Dyes a no
Are there employee incentive programs related to waste minimization? O yes O no
Does the facility have an establshed waste minimization program in place? O yes G no
If yes, is a specific person assigned to oversee the success of the program? G yes G no
Oi?ซU?$ goal? 0* th* pnjgrflm flrvf n^lfe-
Has a waste minimization assessment been performed at the facility in the past?
If ytff, discuss;
Dyes Gno
,
-------
Finn Wast* Minimization Assซssmซnt Prepared By
A'Ja Pro/} 1 Ini}/Opftr
Checked Bv
navป pm, NO Sheet of Page of
1
WORKSHEET OPTION GENERATION:
9 Good Operating Practices
Mtatlng format (ซ.g., bralnstormlng, nominal group technique)
Moling Coordinator
MMilng PartlKlpflnt*"
Suggtstซd Wast* Minimization Options
Increase Size of Production Run
Perform Material Balances
Keep Records of Waste Sources & Disposition
Waste/Materials Documentation
Provide Operating Manuals/Instructions
Employee Training
Increased Supervision
Provide Employee Incentives
Encourage Dry Cleanup
Increase Plant Sanitation
Establish Waste Minimization Policy
Set Goals for Source Reduction
Set Goals for Recycling
Conduct Annual Assessments
Currently
Don* Y/N?
Rationale/Remarks on Option
40
-------
Pirm Wast* Minimization Assessment f
^itfl '
Data PfOJ NO '
WORKSHEET WASTE MINIMIZATION:
1 fl A Segregation, Reuse,
1 w** Recovery, & Treatment
'repared By
Checked Bv
Sheet of Paae
of
A. SEGREGATION
Segregation of wastes reduces the amount of unknown material in waste and improves prospects for reuse &
Are different solvent wastes segregated? G yes
Are aqueous wastes segregated from solvent wastes? G yes
Are spent solutions segregated from the rinse water streams? G yes
If no, avplairr
recovery.
Gno
Gno
G no
Does the plant use chelators in any of the process baths? G yes
If yes, are waste streams that contain chelators segregated from other waste streams
prior to treatment? (Waste streams that contain chelators often require additional treatr-ฐnt.
This additional treatment will cause a greater volume of wastewater treatment sludge
to be generated.) Gyes
B. CONSOLIDATION/REUSE
Are many different solvents used for cleaning? G yes
If too many small-volume solvent waste streams are generated to justify on-site distillation,
can the solvent used for cleaning be standardized? G yes
Is spent cleaning solvent reused? Gyes
Does the plant generate spent alkalne and/or acidic baths that can be used for elementary
neutralization in the industrial waste treatment process? G yes
Describe which measures were successful'
Qno
Gno
Dno
G no
Gno
Gno
Has off-site reuse of wastes through Waste Exchange services been considered? G yes
Or reuse through commercial brokerage firms? G yes
H yซfi, rasiilte-
Gno
Gno
41
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Firm
Site
Date.
Wast* Minimization Assessment
Proj. No.
Prepared By
Checked By
Sheet of Page of
WORKSHEET
10B
WASTE MINIMIZATION:
Segregation, Reuse,
Recovery, & Treatment
C. Qn-Slte Recovery
On-site recovery of solvents by distillation is economically feasible for as little as 8 gallons of solvent waste per day.
Has on-site distillation of the'spent solvent ever been attempted?
If yes, Is distillation still being performed?
If no, explain:
O yes
Dyes
Gno
I] no
Does the plant generate waste streams that contain valuable process chemicals or metals? O yes G no
If yes, does the plant currently utilize any recycling technologies to recover valuable process
chemicals or metals? , G yes D no
Does the plant utilize treatment technologies to recycle rinse water? D yes O no
If no, has the plant assessed the potential for developing a closed loop rinse water system? G yes G no
Discuss the results of recycling: ,
D. Alternative Treatment Technology
Doss the plant operate an industrial waste treatment facility? G yes 3 no
If yes, does the treatment facility produce a wastewater treatment sludge that is handled
as a hazardous waste? D yes G no
Has the plant evaluated the use of alternative treatment chemicals (such as caustic soda
Instead of Ime or polyelectrolytes Instead of alum or ferric chloride) to identify those that
generate the lowest vobme of sludge? G yes G no
If yes, has the plant evaluated the use of an alternative treatment system that produce less
residual waste than the existing treatment facilty? G yes G no
42
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APPENDIX A
CASE STUDIES OF PRINTED CIRCUIT BOARD
MANUFACTURING PLANTS
In 1986 the California Department of Health Services
commissioned a waste minimization study (DHS 1987) of
three printedcircuit(PC)boardmanufacturingf5rms, called
plants A, B and C in this guide. The results of the three
waste assessments wereusedtopreparewasteminimization
assessment worksheets to be completed by other printed
circuit board manufacturers in a self-audit process.
The three printed circuit board manufacturing plants
were chosen for their willingness to participate in the
study, their applicability to the study's objectives, and the
potential usefulness of the resulting data to the industry as
a whole. Th'e waste minimization assessments were
concerned with wastegenerated within theplantboundaries
and not with waste derived from printed circuit board
application or disposal of board parts.
This Appendix section presents the results of the
assessments ofPlantsA,BandCand the waste minimization
options either already in use or being considered for use by
the firms.
The waste minimization assessments were conducted
according to the description of such assessments found in
the "Introduction: Overview of Waste Minimization," in
this guide. The steps involved in the assessments were (see
also Figure 1):
Planning and organization
Assessment phase
Feasibility analysis phase
The fourth phase, Implementation, was not a part of
these assessments since they were conducted by an outside
consulting firm. It was left to the printed circuit board
manufacturers themselves to take steps to implement the
waste minimization options that passed the feasibility
analysis.
PLANT A WASTE MINIMIZATION
ASSESSMENT
Planning and Organization
Planning and organization of the assessment was done
by the consulting firm with the assistance of personnel
from the PC board manufacturing firm. Initial contact was
made with the PC board manufacturer's plant operations
manager, a high level manager who could provide the
company's commitment to cooperate in the assessment and
provide all the necessary facility and process information.
The goal of this jointeffort was to conduct acomprehensive
waste minimization assessment for the plant Under
different circumstances, in a company with its own on-
going waste minimization program, goals could be set to
target a specific amount or type of waste to be reduced; or
to conduct a waste minimization assessment each year; or
other goal. The waste assessment task force in the case of
Plant A consisted of the consultants working together with
the plant manager. This task force also functioned as the
assessment team.
Assessment Phase: Process and Facility
Data
Initial discussionsbytelephonebetweentheconsultants
and the plant manager were used to request process and
facility information prior to a site visit. These discussions
also served to identify particular waste streams of concern
to plant managers.
At the site visit, the plant operations manager and
consultants met to review the facility's operations and its
potential target waste streams. The manager conducted a
facility tour and introduced the consultants to process
managers and workers involved in materials and waste
handling. Someofthesepeoplewereinterviewedtoobtain
information about specific procedures used at the plant
FACILITY DESCRIPTION
Plant A is a prototype circuit board manufacturer that
specializes in jobs involving limited production and fast
turnaround. Manufacturing operations include drilling
and routing, layering (for multilayer boards), photoresist
printing, plating, etching, and stripping.
PROCESS DESCRIPTION
Figure A-l is a floor plan of the plant's plating,
etching, and stripping operations. The numbers listed on
the floor plan represent the identification number for each
process bath and rinse tank. Tables A-l, A-2, and A-3
provide information on the plant's operations. Table A-l
describes each process bath used at plant A and Table A-
2 describes each rinse system used at the plant.
43
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44
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Table A-l. Process Bath Information
PROCESS BATH/
IDENTIFICATION
NUMBER
Cleaner-Conditioner/1
Sulfuric-Peroxide Etch/3
Catalyst Premix/5
Catalyst/6
Accelerator/8
Electroless Copper/11
5%SulfuricAcid/12
100% Suit uric Acid/13
Neutralizer
Etchback/15 .
Brown Oxide/17
Ammonium Biflouride/19
Metex Cleaner/20
10%Sulfuric Acid/22
Copper Gleam/23
Copper Gleam/24
10% Fluorboric Acid/27
Tin Lead/28
Resist Stripper/31
Tin Immersion
Conditioner/33
Ammoniated Etch/34
Reflow Oil/36
PROCESS
BATH
VOLUME
(gallons)
30
30
30
30
30
30
30
30 '
30
30
30
20
400
400
400
20
400
30
disposal
30
, supplier
30
METHOD
OF
DISPOSAL
IN TANK
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
To treatment
Off-site
Reclaimed by
supplier
Reclaimed by
Off-site disposal
FREQUENCY
OF DUMPS
2 weeks
4 weeks
2 weeks
2 weeks
2 weeks
1 week
4 weeks
4 weeks
1 week
1 week
3 years
3 years
2 weeks
3 years
2 weeks
4 weeks
WASTE DESCRIPTION
Production activities that generate hazardous waste
are the plating, etching, and stripping processes. The
sources of waste fromtheseactivitiesarerinsing operations,
spent process bath dumping, industrial waste treatment,
andequipmentcleanout Table A-3 describes thehazardous
wastes produced at the plant.
Spent Chemical Bath
When a process chemical bath becomes too
contaminated or diluted for use (spent), it is removed from
the process tank. The spent chemical bath is then either
contamerizedforreclairnbythernanufacturer,containerized
for off-site disposal, used as a neutralization chemical in
the industrial waste treatment system, or dumped into the
wastewater collection sump. The chemical baths are
changed periodically according to the plant's current time
schedule. This schedule was developed by Plant A based
on its experience with various process baths.
Only two of the spentbath handling methods contribute
to the amount of hazardous waste generated at the plant.
Thesemethods are containerizing wastefor off-site disposal
and dumping of spent chemical baths into the wastewater
sump. Two process chemical baths are containerized for
disposal: (1) photoresist stripper and (2) reflow oil.
Approximately 55 gallons of waste stripper are generated
monthly. Plant A did not estimate the volume of waste
reflow oil generated each month.
Photoresist stripper waste is generated at the
conditioning and stripping line. The stripper is used in a
30-gallon tank where circuit boards are immersed to strip
off the remaining photoresist material. The chemical bath
is changed approximately every 2 weeks. The resultant
stripper waste is highly alkaline with a pH over 12. The
waste stripper contains a polymer residue which, when
agitated, remains suspended in the solution.
Reflow oil is used to enhance the formation of a
smooth, uniform film of solder onto printed circuit boards.
The reflow oil bath is maintained at anelevated temperature
during use. When thebath becomes spent, itis containerized
for off-site disposal. Analytical data for the spent oil were
not available.
45
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Table A-2. Rinse System Information
Rinse System/
Number
Dip Rinse/12
Dip Rinse/4
Dip Rinse/7
Dip Rinse/9
Dip Rinse/10
Dip Rinse/14
Dip Rinse/16
Spray Rinse/21
Drag-out/25
Spray Rinse/26
Drag-out/29
Spray Rinse/30
Rinse Water
Flow Rate
16gal/min
16 gal/min
16gal/min
16 gal/min
16gai/min
16 gal/min
16 gal/min
1.5 gal/min
1.5 gal/min
1.5 gal/min
Number
Of Tanks
one
one
one
one
two
one
one
one
one
one
one
one
'Counter Process Bath(s) Estimated
Current Preceding Rinse Daily Water
System System Use
(Y/N)
no Cleaner/ 1500 gallons
conditioner
no SuHuric/ ISOO^gallons
peroxide etch
no Catalyst 1500 gallons
no Accelerator 1500 gallons
no Rinse tank #9 1500 gallons
no Sulfuricacid 500 gallons
' no Neutralizer 500 gallons
etchback
no Metex cleaner
no Gapper gleam
no Sulfuricacid
no Fluorboric acid
no Drag-out tank #29
Table A-3. Hazardous Waste Data
WASTE
Industrial Waste
Treatment Sludge
Photoresist
Stripper
ReflowOil
Nitric Acid
Copper Sulfate
Crystals
ANNUAL
QUANTITY
GENERATED
2,400 gal.
720 gal.
120 gal.
DISPOSAL
METHOD
off-site
metal
reclamation
off-site
disposal
off-she
disposal
off-site
disposal
off-site
disposal
DISPOSAL
COST/UNIT
$1.00/gal
ANNUAL
DISPOSAL
COSTS
$2,400
The plant's standard practice for dumping spent
chemical baths into the wastewater sump is to transfer
waste chemicals to one of the two metering tanks (tanks A
and B in Figure A-l). These tanks slowly discharge waste
chemicals into the waste sump. The purpose for slowly
feeding the spent bath chemicals into the wastewater sump
is to prevent surges in the waste stream pH or metals
content These two metering tanks have not, however,
been in operation since July 1986. The present practice is
to manually dump the spent baths into the collection sump.
Plant A personnel indicated that this practice causes a
fluctuation in the pH of the waste stream entering the
treatment system.
Copper sulfate crystals are generated when some of
the process baths are taken off-line. The crystals form in the
process bath as the copper content increases. Before the
process baths are dumped into the wastewater sump, the
crystals are removed and containerized as a solid waste
since they cannot be fed into the treatment system.
46
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Rinsing Operations
Rinsing operations associated with the chemical
process lines are the major source of wastewater at Plant A.
Plant A estimates that approximately 10,000 gallons of
wastewater are generated each day. The rinse operations
contribute to hazardous waste generation because waste
irinse water carries away chemicals which are thenremoved
by treatment at the industrial waste treatment plant The
sludge that is generated from this treatment is handled as a
hazardous waste.
Plant A uses nine dip rinse tanks and three spray rinse
tanks. All rinse water used at Plant A is deionized onsite
prior to use. All but two of the rinse tanks are plumbed
directly to the wastewater treatment system through a 500-
gallon collection sump. The other two are batch dump
tanks which require manual dumping into the sump.
Discussions with facility personnel indicate that water
flows through the dip rinse tanks only when theprocess line
associated with the tank is in operation. However, during
both visits, the assessment team observed water flowing
through several rinse tanks even when the process line was
not being operated. Theflowrateofwaterthrougheachdip
rinse tank was measured to be approximately 16 gallons
per minute. This was measured by closing the drain line,
turning on the feed water for 20 seconds, measuring the
water level rise in the rinse tank, and calculating the
volume of water that entered the tank during the time
period. Theflowrateofwaterthroughthesprayrinsetank
has been estimated by the assessment team to be
approximately 1.5 gallons per minute.
Industrial Wastewater Treatment
Plant A's industrial waste treatment facility treats all
wastewater before discharging it to the San Jose/Santa
Clara Water Pollution Control Plant Plant A's treatment
facility removes metals andadjusts the pHof the wastewater
to meet discharge requirements set by the water pollution
control plant. The maximum allowable concentration of
metals in the discharged effluent, as set by die San Jose/
Santa Clara Water Pollution Control plant, are as follows:
Chromium
Copper
Cyanide
Lead
l.Omg/L
2.7mg/L
l.Omg/L
0.4mg/L
Nickel 2.6mg/L
Silver 0.7mg/L
Zinc 2.6mg/L
The treatment process includes metal reduction,
neutralization, and flocculation. The treatment plant is
located outside the main building in a fenced and curbed
area. Themetalhydroxide sludge generatedby the treatment
process is a hazardous waste.
Chemical treatment is performed in three separate
tanks; the wastewater then goes through sludge separation
and dewatering. Approximately 10,000 gallons of
wastewater are treated each day. Wastewater
characterization data were not provided by Plant A. The
incoming wastewater is pumped from the collection sump
to the first tank where ferrous sulfate and sulfuric acid are
added. Ferrous sulfate is used to reduce the copper to its
precipitable form. The sulfuric acid is used to maintain the
pH between 2.0 and 3.0 during the ferrous sulfate reaction.
The waste is then neutralized with alum and sodium
hydroxide. The alum causes the suspended solids to
collect, forming larger particles, and me sodium hydroxide
raises the pH to approximately 9.0. A polyelectrolyte
coagulant is then introduced to aidin the flocculation of the
contaminants. The polyelectrolyte causes the precipitated
contaminants to congeal into large flakes which can be
settled out of the waste stream. Plant A personnel provided
information on the quantities and costs of treatment
chemicals used each month (Table A-4).
Table A-4. Quantities and Costs of
Treatment Chemicals - Plant A
Chemical
Cost/Unit
Ferrous sulfate
$0.33/lb $280
Alum
$0.47/lb $400
Sodium hydroxide
$0.55/gal
$0.92/gal
Polyelectrolyte
$7.50/lb $ 22
Monthly Usage
Cost/Month
850 Ibs
850 Ibs
200 gallons
(30% solution in
$110 winter
winter)
(50% solution in
$185 summer
summer)
3 Ibs
Total $812/in winter
$887/in summer
The wastewater treatment sludge that is settled out of
the effluent waste stream is transferred to the sludge
dewatering unit, and the effluent is discharged to the San
47
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Jose/Santa Clara Water Pollution ControlPiant. Sludge is
dewatered in a bag filter that increases its solids content to
11 percent The dewatered sludge is transferred into 55-
gallon drums and stored for pickup by a metal reclaimer
(World Resources Company). Plant A plans to use large
storage bags in the future which will hold the equivalent of
four55-gaUondrums. Plant Aestimatesthatfour drums of
industrial waste sludge are generated each month. The
sludge is considered a hazardous waste because of the
copper content
Analytical data for the sludge were obtained from
World Resources Company of Phoenix, Arizona. World
Resources analyzes a sample from each load of sludge
transported to them for metal reclamation. The data
provided by World Resources are as follows:
Percent solids
11%
Metal content in pounds per dry ton
Copper 195
Nickel 6
Tin 46
Iron 399
Zinc 9
Lead
Chromium
23
20
Equipment Cleanout
The primary sources of hazardous waste associated
with equipment cleanout are the cleaning of the copper
etching tank, cleaning of tanks used in the electroplating
line, and cleaning of electroplating racks. This equipment
is cleaned by using nitric acid. Plant A estimates that one
55-gallon drum of waste nitric acid is generated every 6
months. The wastenitric acidhas too low apHand too high
a copper content to be treated at the plant's wastewater
treatment system. Analytical data on the waste nitric acid
were not available from Plant A.
Other cleaning activities, such as floor washing and
chemical bath tank rinsing, generate waste streams that
dischargeintothewastewatercollectionsump. According
to Plant A personnel, these waste streams make up a small
portion of the chemicals that enter the treatment system.
Assessment Phase: Option Generation
The consultants reviewed the plant operations data
obtained prior to and during the site inspection. They
developed a set of waste minimization options based on
this information and on information in the literature. These
options were screened for their effectiveness in reducing
waste and for their future implementation potential. The
plant manager participated in this screening, with the result
that there was general consensus on the listofrecommended
options.
SOURCE REDUCTION
The following paragraphs describe the application
and use of source reduction measures to various waste
streams at Plant A.
Material Substitution
Opportunities for material substitution that apply to
Plant A include (1) using process chemistries that can be
recycled or treated prior to discharge to the publicly owned
treatment works (POTW) and (2) using chemistries that
have less impact on sludge generation. Process chemistries
that Plant A currently containerizes for off-site disposal
include spent reflow oil and nitric acid waste. Several
reflow oil products are available that, when spent, either
can be returned to the supplier for recycling or can be
treated by the facility prior to discharge to the POTW.
Plant A could eliminate a hazardous waste stream by
replacing its presentreflow oil with a recyclable or treatable
reflow oil.
Nitric acid waste, which is generated fromthecleaning
of electroplating racks, can also be eliminated by using an
alternative cleaning solution. One chemical supplier offers
an electroplating rack cleaning solution that can be
regenerated. The metal stripped off of racks can be plated
out in a tank equipped with a cathode and an anode. The
metallic sludge then settles to the bottom of the cleaning
tankwhereitcanberemoved and mixed with the wastewater
treatment sludge. Once the cleaning solution becomes
spent, it can be treated in the plant's industrial waste
treatment system before being discharged to the POTW.
The use of recyclable cleaning solution will eliminate the
generation of waste nitric acid. The metallic sludge that is
generated can be sent to a metal reclaimer along with the
wastewater treatment sludge.
Theuseofnon-chelatedprocess chemistries can reduce
the volume of sludge generated during wastewater
treatment PlantAusesferroussulfate to treatits wastewater.
The ferrous sulfate is used to break down chelators so that
metals can be precipitated. The iron in ferrous sulfate also
precipitates as a metal hydroxide and contributes to sludge
volume. The analytical data for Plant A's industrial waste
treatment sludge indicate that iron contributes
approximately 57 percent of the total metal content of the
sludge. If all the iron precipitates as metal hydroxide, the
iron hydroxide contributes 34 percent of the total dry
weight of the sludge. If plant A used rion-chelated process
48
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chemistries, ferrous sulfate treatment could be eliminated
and sludge generation could be reduced. Most chemical
suppliers offer non-chelated process chemistries or
chemistries with mild chelators that do not require ferrous
sulfate treatment. Plant A should consult with chemical
suppliers to identify alternative process chemistries that
can be used so that ferrous sulfate treatment can be
minimized.
Rinse Water Reduction
Although rinse water is not a hazardous waste, the
treatmentof this wasteproduces a sludge that is a hazardous
waste. Since the volume of the sludge generated by
treatment is a function of the volume of wastewater treated
as well as the concentration of contaminants in the waste,
the plant can reduce the volume of sludge generated by
reducingits rinse water generation. Several rinse reduction
options are available to Plant A that can reduce the volume
of wastewater requiring treatment. Multiple stage rinse
water systems were not evaluated because not enough
space is available at Plant A's facility.
Rinse Tank Operations
Plant A now operates several of its dip rinse tanks as
. flow-through tanks. Deionized water is plumbed into the
tank during operation and the overflow is plumbed to the
collection sump. Eachoftherinsetanksholds approximately
30 gallons of rinse water, and the flow of water through
each tank is approximately 16 gallons per minute. PRC
believes that the plant could modify its operation of these
rinse tanks to reduce the volume of wastewater generated.
Two options are available for Plant A: (1) the dip rinse
tanks can be operated as batch rinse tanks or (2) the flow
rate through the tanks can be reduced.
If these seven dip rinse tanks were operated as batch
rinse tanks (which means they would operate as stagnant
rinse tanks that are emptied between rinse operations and
then refilled with deionized water), Plant A could reduce
its rinse water generation significantly. Table A-4 shows
the volume of rinse water generated by Plant A and the
volume that would be generated if the seven dip rinse tanks
we're operated as batch rinse tanks. The values for the time
water is running and for the number of workpiece racks
processed daily were provided by Plant A personnel. This
option assumes that each rinse tank can provide adequate
rinsing of one process rack when filled with fresh deionized
water. Plant Adidnotprovidetheauditors with information
on therequired operating parameters of the rinse systems.
Therefore, the impact of batch rinsing on the efficiency of
the rinsing operations couldnotbeassessed. The following
example, however, illustrates the feasibility of batch rinsing.
The equation for determining the volume of rinse
water needed to rinse a full workpiece rack is as follows:
Q = D(Cp/Cn)
WhereQ = rinse tank flow rate
D = drag-out rate
Cp = concentration of salts in process solution
Cn=allowable concentration in rinse solution
Several assumptions must be made to use this equation
to illustrate the potential for operating the rinse tanks as a
batch rinse system. These are as follows:
The concentration of chemicals in the rinse
solution cannot exceed 1/1000 of the
concentration of chemicals in the process bath.
This value is a common parameter used in the
electroplating industry for rinse water
contaminant concentration.
The drag-out rate of chemicals used for
manufacturing printed circuit boards is
approximately 15 ml/ft2 of board. Thisvalueis
a standard approximation used for estimating
drag-out created by a printed circuit board
(Foggia, 1987).
Anaverageworkpiecerackholdsapproximately
2.5 ft3 of boards (example: 30 4-inch by 3-inch
boards).
The drag-out rate for each workpiece rack is:
15mlx2.5ft3 = 37.5ml.
Converted to gallons, drag-out equals 0.01 gallon.
By substituting the values into the equation:
0.01 gallon x 1000 = 10 gallons
!
10 gallons of fresh rinse water will provide adequate
rinsingundertheoperatingparameters previously described.
Since the rinse tanks hold approximately 30 gallons of
rinse water, theoretically, a full tank of fresh water would
provide adequate rinsing without operating the tank as a
flow-through tank. Workpiecerackagitation or air spargers
can be used to improve efficiency to assure adequate
rinsing in the batch rinse tank.
Although using the dip rinse tanks as a batch process
canprovidesignificantreductions in wastewater generation,
there may be several process lines for which this is not
feasible because of thechemistry of the process. However,
even if some of the tanks must operate as flow-through
rinse systems, the volume of deionized water used can still
be reduced for these tanks. The same equation can be used
to demonstrate that the present flow rate used in the rinse
tanks may be excessive.
49
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The equation can be rearranged to indicate the ratio of
process bath concentration to rinse solution concentration,
as follows:
0_=
D
Cp/Cn
The same drag-out volume (0.01 gallon) will be used,
and it will be assumed that the process rack remains in the
rinse tank for 3 minutes. The ratio of the process bath
concentration to rinse solution concentration is as follows:
16 gals/min x 3 min = 4,800
0.01 gal.
Therefore, to justify the present rinse water flow rate,
the concentration of chemicals in the rinse solution can
only reach 1/4,800 or 2/10,000 of the concentration of
chemicals in the process bath before rinse efficiency is
reduced. As previously stated, the electroplating industry
usually allows rinse water concentrations to reach 1/1000
the concentration of chemicals in the process tank. Plant A
should consult chemical manufacturers' representatives
and perform experiments to determine the proper flow rate
for its rinse tanks if batch operation is not feasible.
By calculating the flow rate necessary to maintain the
rinse water at an acceptable chemical concentratioa.JPlant
Amayfindthatthe 16 gallonper minute flowrate presently
used is too high. In addition, the use of air spargers or work
piece rack agitation should improve rinse efficiency and
allow for use of lower rinse water flow rates.
Rinse Water Flow Controls
Plant A presently turns on the rinse water in-flow
valves manually. When the process line is in operation,
plant personnel turn on the water for all the rinse tanks and
then turn the water off after the production process is
complete. However, the consultants observed that rinse
tanks were left on even when the process line was not in
use. The use of automated flow controls would be helpful
for ensuring that rinse water is not left running and for
controlling the flow rate when the rinse water is turned on.
The plantshould consider installing pH meters in each
of the rinse tanks to control the flow of water through the
rinse systems. The meters should be set to turn the fresh
waterfeed valve on when the chemical concentration in the
rinse gets too high. If the required pH range for each rinse
tankisdetermined,themeterscanbesetto turn on the water
automatically. When therinse tank solution pHreaches the
maximum allowable level to provide efficient rinsing, the
meter will send a signal that activates a valve on the
influent line. When the rinse solution again reaches an
acceptable pH, thepH meter will send a signal that turns off
the water feed valve.
Flow restrictors can also be used to reduce flow rates.
A limiting orifice or similar flow-restricting device can be
installed in the water line to each tank to reduce the flow
rate-to each tank. Plant A uses approximately 2-inch
diameter piping for its rinse inflow lines. This piping may
be oversized for the pressure on the line and the required
flow rate. The use of flow restrictors, therefore, may
provide better controls over the rate of rinse water usage.
One circuit board manufacturer who installed pH meters,
flow restrictors, and other water reduction devices, such as
foot pedal pressure switches, was able to reduce water
usage by two thirds.
Process Bath Drag-Out
Process bath chemicals are carried into the rinse water
when the racks that hold the printed circuit boards are
removed from a process bath tank and placed in a dip rinse
tank. This is performed manually atPlant A. The operator
removes the rack, briefly holds it above the process baut
tank, and Submerges the rack into the rinse tank. The
consultantspersonnelobservedplantpersonnelperforming
this operation and found that the racks are quickly removed
from the process bath and held over the process bath tanks
for less than 10 seconds. This procedure allows excessive
chemicals to enter the waste rinse water stream. Actual
drag-outvolumeswerenotavailablefromPlantA,however.
The manner in which racks are removed from process
baths will significantly affect the amount of drag-out
carried into the rinse tanks. Slow removal of workpieces
causes a much thinner film of process chemicals to adhere
to the workpiece surface. This effect is so significant that
most of the workpiece drainage time should be used to
remove the workpiece rack from the process bath. The
consultants observed that Plant A personnel remove racks
in one quick movement. We suggest that Plant A train its
personnel to remove racks in a slow, smooth manner. Plant
A could also improve the drag-out recovery efficiency of
the process lines by installingabar or rail above the process
tank so that the racks can be hung and allowed to drain
longer.
The auditors did not predict the drag-out volume that
can be recovered by removing racks at a slower rate and
allowingrackstodrainforalongerperiodof time. However,
the savings realized by reducing drag-out losses include
reducing process chemical purchases and reducing
wastewater treatment sludge generation. Plant A can
determine the effectiveness of these drag-out reduction
techniques by holding the racks over a collection pan after
removing them. The volume of drag-out that can be
recovered afterremoving racks at various rates andallowing
racks to drain for various lengths of time can then be
measured and the optimal removal rate and drainage time
can be determined.
50
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Equipment Cleanout
Plant A generates approximately 55 gallons of waste
nitric acid every 6 months from cleaning out the
electroplating tanks and from cleaning the electroplating
racks. Plant A may be able to reduce the volume of nitric
acid generated by modifying the existing cleaning methods.
One method for reducing the volume of waste nitric
acid produced is to set up a workpiece rack cleaning line
with several small tanks of nitric acid. The cleaning line is
then used like a multi-stage rinse system. The first tank
contains the most contaminated nitric acid solution and the
final tank in the cleaning line contains the freshest nitric
acid. When the first tank no longer performs adequate
initial cleaning, it is containerized for disposal (or used as
initial, cleaning solution for tank cleanout). Then the
second tank in the cleaning line becomes the first. The
empty tank is then filled with fresh nitric acid and it
becomes the last tank in the cleaning line.
The use of a multi-stage rinse system can provide
significantreductionsinwastecleaning solution generation.
One printed circuit board manufacturing plant visited by
the consultants uses a five-stage multiple tank cleaning line
and only generates approximately 15 gallons of waste
nitric acid each 6 months.
Chemical Process Baths
The chemical load on wastewater can be reduced by
operating the process baths at lower concentrations. A
manufacturer's recommendations for chemical
concentrations in process baths arenotalways appropriate.
We recommend that Plant A evaluate the efficiency of the
concentration parameters of its present chemical process
bath to determine if these concentrations can be reduced.
By reducing the concentration of chemicals in a process
bath, the plant will minimize the chemical load in the
wastewater when these baths are dumped. This reduction
will also reduce the chemical concentration in the rinse
water by minimizing drag-out chemical loses.
One method of reducing process bath chemical
concentrations is to operate fresh baths at lower
concentrations than older baths. Plant A can accomplish
this by gradually increasing the chemical concentration in
5 the process bath as it gets older. This practice can reduce
the chemical concentration of the drag-outfrom fresh baths
and also extend the life of some process baths.
Waste Segregation
The wastewater generated at Plant A is plumbed or
manually dumped into a 500-gallon collection sump.
Therefore, all wastes that can be treated on-site are mixed
prior to treatment This practice may cause excessive use
of treatment chemicals and an increase in the volume of
sludge generated. Waste segregation may reduce the use
of treatment chemicals and the generation of sludge in two
areas: the non-contact cooling water used for the copper
etch machine and the wastestreamsgeneratedby processes
that contain chelating chemistries.
Plant A personnel indicated that the cooling water
system used in the copper etcher is a once-through system,
with the effluent discharged to the collection sump. If the
system were operated as aclosed loop system, there would
not be an effluent waste stream. Also, since this water is
used as non-contact cooling water, the effluent that is now
generated by the system may not require treatment. The
effluent, therefore, couldpossiblybe discharged directly to
the sanitary sewer, if permitted by the Publicly-Owned
Treatment Works (POTW).
The use of a closed loop cooling system would lead to
reductions in water and sewer fees, treatmentchemical use,
and sludge generation. Direct discharge of non-contact
cooling water to the sanitary sewer would result in savings
from reduced treatmentchemical use and sludge handling.
The consultant was unable to obtain estimates on the
volumeof water usedintheetcher cooling system; therefore,
specific values for savings cannot be presented.
The primary purpose of the treatment system used at
Plant A is to remove metals from the waste stream so that
the discharged effluent can meet San Jose/Santa Clara
Water Pollution ControlPlantpretreatmentstandards. The
highest metals concentration in the wastewater is copper,
and the treatment system is designed to remove the copper
through a ferrous sulfate reduction process. The ferrous
sulfate process is designed to break down chelators that
keep metals in solution past their normal solubility limit.
The ferrous sulfate contributes significantly to the volume
of sludge generated in the wastewater treatment process.
Analytical data indicate that iron content in the sludge is
399 pounds per dry ton of solids. Assuming that all the iron
precipitates as a hydroxide, iron hydroxide contributes 34
percent of the total dry weight of solids in the sludge. If
there is a direct relationship between solids content and
total sludge volume, the plant could reduce sludge volume
by 34 percent by eliminating iron from the waste treatment
system.
Several options are available to eliminate or reduce the
amount of ferrous sulfate used in the treatment process.
These include: (1) eliminating the use of chelated process
chemistries, (2) usingprocess chemistries that only contain
mild chelators, (3) segregating waste streams that contain
chelators from other waste streams, and (4) segregating
waste streams that contain copper from other waste streams.
Plant A was unable to identify which process baths use
chelators or what type of chelators are used. Therefore,
51
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specific recommendations for waste segregation cannot be
developed. However, several waste segregation options
are described.
Use of non-chelated process chemistries or mild
chelators may allow Plant A to eliminate the use of ferrous
sulfate. Since the primary purpose of ferrous sulfate is to
break down chelators so that copper can be precipitated
from the wastewater, non-chelated process chemistries
would allow the use of an alternative precipitant such as
caustic soda. Mild chelators, such as ethylenediamine
tetraacetic acid (EDTA), can be broken down through pH
reduction. Therefore, if EDTA is used where chelators are
needed, such as in an electroless copper bath, ferrous
sulfate may not be required for wastewater treatment.
Mixing waste streams that contain chelating agents
with waste streams that are non-chelated appears to cause
asignificant increase in the amountof treatment chemicals
used, and should be avoided when possible. Ferrous
sulfate use can also be reduced by segregating waste
streams. According to Plant A personnel, the sources of
copper thatenterthe wastewater are (1) thecopper drag-out
tank, (2) spray rinse tank 29, and (3) dip rinse tanks 9 and
10. If these waste streams were segregated from the rest of
the wastewater, ferrous sulfate treatment would only be
necessary for apercentageof the waste. This couldbe done
on a batch treatment basis if a holding tank is used to store
the waste until treatment Theremaining wastewater could
have metals removed by neutralization and precipitation
with caustic soda. This would reduce the amount of
treatment chemicals used at the facility. If other waste
streams contain chelators, these could also be segregated
from the rest of the waste stream.
RECYCLE AND RESOURCE RECOVERY
ALTERNATIVES
Recycling and resource recovery includes the direct
use of a waste stream or the recovery of materials from a
waste stream. Plant A appears to handle many of its waste
streams in this manner. Spent sulfuric acid is used in the
wastewater treatmentsystem,andseveralchemical process
baths are returned to the manufacturer when they become
spent. This chapter describes several additional recycling
andresourcerecovery techniques thatmaybe implemented
by Plant A.
Stripper Waste
Plant A personnel indicated that the plant's stripper
waste is an alkaline solution that could be reused or used in
the treatment system if the polymer residue could be
removed. Theplant could use a filter or decantation system
to separate the residue from the waste solution. Also, the
volume of stripper waste generated can be reduced
significantly by using a multiple tank stripper system. This
type of system allows the first stripper tank (the one with
the most contaminated stripper solution) to be used for a
longer period of time because the second stripper tank will
be used for additional photoresist stripping. Therefore, the
photoresist stripper does not have to be replaced every 2
weeks. When the first tank is dumped, the second tank
becomes the first Fresh resist stripper is then added to the
second tank.
Rinse Water Recycling
Currently, Plant A plumbs all its rinse water effluent
directly into the collection sump. However, the plant may
be able to recycle some of the rinse water solutions. For
example.rinse systems thatfollow an acid process chemical
bath, such as a peroxide/sulfuric acid etch, can sometimes
be used for feed water to a rinse system that follows an
alkaline cleaning bath. Implementation of such a system,
however, should be done only after careful testing to make
sure that addition of acid rinse water to the alkaline rinse
bath does not cause problems with metal hydroxide
precipitation on clean parts.
The configuration of Plant A's process lines may allow
some of these rinse systems to be plumbed together in
series. For example, rinse tank 14, which follows a sulfuric
acid bath, could be plumbed into rinse tank 16, which
appears to follow an alkaline cleaning bath. Based on data
of the existing water used, rinse tanks 14 and 16 both use
approximately 500 gallons each day. If 100 percent of the
water used in rinse tank 14 could be used for rinsing
operations in tank 16,500 gallons of water could be saved
each day. The plant would also reduce the volume of
wastewater treated each day by 500 gallons and could,
therefore, reduce treatment chemical usage and sludge
generation. Rinse water could also be recycled if the rinse
tanks were operated on a batch process.
Copper Sulfate Crystals
Plant A personnel indicated that they were unsure of
how to handle the copper sulfate crystals generated at the
plant Currently, these crystals are disposed of off site as a
hazardous waste. One option available to the facility is to
mix the crystals with the industrial waste treatment sludge.
Since this sludge is sent to a reclaimer, the copper content
in the crystals may bring Plant A a larger payment on
reclaimed copper. This practice will also prevent Plant A
from accumulating containers of crystals.
TREATMENT ALTERNATIVES
Waste reduction through alternative treatment can be
achieved by modifying a treatment system to reduce the
52
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volume of hazardous waste generated One of the treatment
alternatives available to Plant A is segregation of waste
streams, which is described earlier in this report. Another
treatment alternative available to Plant A is sludge
dewatering.
Sludge Dewatering
Wastewater treatment sludge generated at Plant A is
dewatered by a gravity filter system. Although this type of
dewatering can remove some of the free water in the
sludge, it is not as effective as mechanical dewatering.
Analytical data for the waste treatment sludge show that
the gravity filter system can increase solids content to 11
percent. Mechanical dewatering equipment can achieve a
solids content up to 35 percent for most industrial waste
sludge. Figure A-2 shows the decrease in sludge volume
that can be achieved by increasing solids content The
figure shows that increasing the solids content from 10
percent to 35 percent reduces sludge volume from 80
gallons to 20 gallons.
Plant A now removes the sludge from the filter system
and allows it to air dry in open drums. This has significantly
reduced the sludge volume, according to Plant Apersonnel.
However, this method of dewatering will not work during
the rain season, anditalso presents problemsfor complying
with the 90-day accumulation limits placed on hazardous
waste generators. Therefore, the use of a mechanical
dewatering system may be beneficial for reducing sludge
volume and also for complying with hazardous waste
regulations.
Assuming a direct correlation between wastewater
volume and sludge volume, Plant A could also reduce its
sludge generation by 80 percent. This would equal three
drums less each month at a savings at $50 per drum, or
$150. Totalsavingsforoperatingeachrinsetankasabatch
rinse system could be as great as $1020 each month.
Savings from reducing the flow rate of water through
each rinse tank depends on the minimum flow rate that can
be used to maintain adequate rinsing. In the Rinse Water
Reduction section, it was shown that the present flow rate
of 16 gallons per minute creates a ratio of proce'ss bath
concentration to rinse solution concentration of 5,000 to 1.
For illustration purposes, assume the flow rate could be
reduced to 12 gallons per minute; ratio would be reduced
to 3750 to 1. The rinsing requirements for Plant A rinse
systems were not available to the consultants. However,
since the standard ratio of process chemical concentration
to rinse solution concentration used in the electroplating
industry is approximately 1000 to 1, a 25percentreduction
in flow rate, which produces a 3750 to 1 ratio, appears
achievable. If the flow ratecouldbereducedby 25 percent:
(1) water and sewer fee savings would be $46 per month
(based on a reduction in water usage of 34,600 gallons and
water and sewer fees of $0.50 per 750 gallons each); (2)
treatment chemical savings would be $210 per month
(based on a 25 percent reduction in existing treatment
chemical costs); and (3) sludge disposal cost savings
would be $50 per month (based on a 25 percent reduction
in sludge volume generated each month). Total savings
would be approximately $310 per month.
The use of automated rinse water flow controls will
require significant capital investment A pH/conductivity
meter used to automatically turn rinse water on and of f will
cost approximately $700 to purchase and install. If these
controls were purchased for all nine rinse tanks, the total
cost would be $6,300. Savings would depend on the
reduction in water usage that could be achieved. Since
drag-out rates for process baths and operating parameters
for the rinse systems were not available, estimates on
saving that can be achieved by installing automated flow
controls cannot be calculated. However, one printed
circuit board manufacturer estimated that water use was
reduced by 67 percent by installing flow control meters.
For illustrative purposes, a more conservative estimate of
25 percent reduction in water use will be used. Therefore,
the use of automated flow control meters could also save
Sun Circuits $310 per month. At that savings rate, payback
on investment would take 21 months.
Feasibility Analysis Phase
The recommended options were evaluated for their
technical and economic feasibility by the consultants, who
obtained cost and performance data from vendors where
new equipment was recommended. The result of the
technical and economic feasibility analyses was a list of
feasible options, which became part of the assessment's
final report. The next waste minimization assessment
phase, Implementation, was left to the discretion of the
printed circuit board manufacturer, Plant A.
The specific economic aspects of implementing each
of the source reduction/resource recovery options were not
separately documented by Plant A. Most of the source
reduction options employed are essentially good operating
practices, and hence did not require a large capital
investment. However, the rework strategies and their
evolution did require a large R&D expenditure. The
implementation of these measures seemed to be guided
more by the intuition and foresight of the plant personnel
thanby the calculated benefits that may have been indicated
by a specific detailed economic evaluation.
RINSE WATER REDUCTION
Operating the rinse tanks as batch rinse systems or
reducing the rate of water flow through the rinse tanks can
53
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1000 -.
tn
"ts
100
0)
0)
TJ
CO
10
0 5 10 15 20 25 30 35
Sludge Solids Concentration (% by weight)
Figure A-2 - Sludge Volume Vs Sludge Solids Concentration
54
-------
be implemented for minimal costs. To operate the rinse
tanks as batchrinse systems, theplant would need additional
labor to manually dump the rinse tanks. Flowrestrictors for
reducing the flow of water through rinse tanks would
require only minor capital investments. The resulting
savings in water usage, sewer fees, and treatment chemical
costs woulddepend on the reduction in water use achieved.
Table A-5 indicates that water usage can bereduced by
6,920 gallons per day, or approximately 80 percent, if all
the rinse tanks were operated as batch rinse systems.
Assuming 20 work days per month, water usage could be
reduced by 138,400 gallons each month. Since both water
usage and sewer discharge fees are approximately $0.50
per 750 gallons, Plant A would save approximately $190
each month on water and sewer fees by reducing water
usage by 138,400 gallons. As stated in Section 2,3, Plant
A spends approximately $850 each month on treatment
chemicals. Therefore,an80percentreductioninwastewater
generation could reduce treatment chemical costs by as
much as 80 percent This would amount to a savings of
$680 each month. Actual treatment chemical savings may
be less because the wastewater will have a higher
contaminant concentration and thus may require greater
treatment chemical feed rates per volume of wastewater.
Reductions in sludge volume will depend on the efficiency
of the treatmentsystem and theactual reductions in treatment
chemical usage.
The use of various drag-out reduction techniques will
increase thepotentialforreducingrinse water usagebecause
less process chemicals will enter the rinse system. By
installing a bar rail above each process tank for hanging
workpiece racks, the plant could allow for greater drainage
time before rinsing. This bar could be installed by Plant A
personnel for a few hundred dollars if constructed out of 1
inch PVC piping. Other drag-out reduction techniques
suchasslowingworkpiecerackremoval rates andoperating
process baths at the lowest possible concentration can be
implemented for little cost. Savings associated with drag-
out minimization cannot be quantified until the techniques
are implemented.
EQUIPMENT CLEANOUT
Plant A can reduce waste nitric acid generation by
using a multiple tank cleaning line. The costs associated
with setting up such a system include the cost of additional
tanks and the installation labor costs. The costs for setting
up a cascade cleaning line would be approximately $350
per tank. Labor costs of $55 an hour for 4 hours would be
$220.
The savings associated with a multiple tank
plating rack cleaning line include reduced costs for nitric
acid purchases and waste acid handling. The consultants
visitedoneplantthatusedfive 15-gallon tanks asamultiple
stagecleaningline. Theplantgenerates 15 gallons of waste
nitric acidevery 6 months. If Plant Acouldreduce its waste
nitric acid generation from 60 gallons to 15 gallons per 6
months, it would achieve a savings of $ 140 in nitric acid
purchases and $90 in waste disposal costs each 6 months.
This is based on nitric acid costing approximately $3.10
per gallon and waste disposal costs being approximately
$2.00 per gallon!
MATERIAL RECYCLING
The auditors identified three waste materials for
recycling: (1) photoresist stripper waste, (2) acidic rinse
water effluent, and (3) copper sulfate crystals. Decanting
or filtering spent stripper waste so it can be reused will
require minor purchases to set up a decantation system or
a filter system. Savings would include fewer fresh stripper
purchases and lower stripper waste disposal costs. If
decantation or filtration couldbe used to extend the process
bath life from 2 weeks to 4 weeks, Plant A could reduce
stripper purchases by 30 gallons each month. Once the
stripper becomes too dilute for continued use, it can be
filtered once more and used in the treatment system for pH
adjustment. This could save Plant A $50 each month for
disposal of stripper waste. A polymer sludge residue
would still be generated, however.
To implement a system to reuse rinse water effluent
from rinse tank 16 for feed water into rinse tank 14, Plant
Awouldneedtospendapproximately$l,000. Thisincludes
$500 for contractor labor for 1 day and $500 for materials
thatincludepipingmaterialsandathree-quarter horsepower
pump, which would be adequate for a typical rinse system.
Assuming that both rinse systems operate at the same flow
rate, no storage tank capacity would be necessary.
Savings associated with recycling rinse water have
been estimated based on Plant A's current water usage.
Water and sewer fee savings would be approximately $13
each month based on a reduction in water usage of 500
gallons each day. Since wastewater generation would be
reduced by 5 percent, treatment chemical usage could also
be reduced by approximately 5 percent. A 5 percent
reduction in the company's existing treatment chemical
costs, which are $850 per month, would save Plant A $42
each month in treatment chemical purchases.
Copper sulfate crystals generated by Plant A could be
recycled by adding them to the industrial waste sludge.
There is no additional cost associated with mixing the
crystals and the sludge since the crystals are also handled
as hazardous waste if kept separate. Since the sludge is sent
to a metal reclaimer, Plant A may receive a larger payment
for reclaimed metals due to increased copper content in the
sludge.
55
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Table A-5. Rinse WaterWaste Generation
Operating as Flow-Through Tanks at a Rate of 16 gprri
Tank
Number
Time Water
is Running
Daily Flow Rate
2 96 minutes 1536 gallons
4 96 minutes 1536 gallons
7 96 minutes 1536 gallons
9 96 minutes 1536 gallons
10 96 minutes 1536 gallons
14 30 minutes 480 gallons
16 30 minutes 480 gallons
8640 gallons
8640 gallons wastewater generated each day.
Operating as Batch Tanks Holding 30 Gallons of
Rinse Water
Tank
Number
2
4
6
8
10
14
16
Number of
Batches Daily
12
12
12
12
12
2
2
Volume of
Wastewater
Generated Daily
360
360
360
360
360
60
60
1720 gallons
1720 gallons generated each day.
WASTE SEGREGATION
The costs and savings associated with segregating
chelated and nonchelated waste streams will depend on the
design requirementsofthesegregationandthemodifications
to the treatment system that can be made once the materials
are segregated. Assuming segregation will only entail
installing a 500-gallon storage tank, pumps, gauges, and
necessary piping, equipment costs would range between
$2,000 and $4,000. Double containment would be more
expensive. In addition, installation costs may be as high as
100 percent of equipment costs.
As discussed in Section 5.1, the ferrous sulfate used to
treat the wastewater contributes approximately 34 percent
of the total sludge volume. The ferrous sulfate also costs
Plant A approximately $250 each month to purchase.
Savingsassociatedwithsegregatingchelatedwastestreams
and batch treating them will depend on the percentage of
ferrous sulfate usage that can be eliminated through batch
treatment of chelated waste streams. Since information on
whichprocesschemicalscontainchelators was not available
to the audit team, development of segregation alternatives
and estimates for material and waste disposal cost savings
could not be developed.
SLUDGE DEWATERING
Small filter press units designed to handle from 0.75 to
3.75 gallons of sludge per load cost between $2,800 and
$4,900. Assuming that Plant A already has a source of
compressed air, the company can install the unit itself. The
unit can handle 7.5 to 37.5 gallons of sludge per5-day work
week. These units can increase solids content from 1
percent to approximately 35 percent. Plant A's current bag
filter dewatering unit can achieve a sludge solids
concentration of 11 percent. An increase in solids
concentration from 11 percent to 35 percent will reduce
sludge volume by approximately 75 percent This could
reduce the plant's sludge generation from approximately
200 gallons to about 50 gallons per month. Since Plant A
estimates that sludge disposal costs approximately $1.00
per gallon, this sludge dewatering could save the company
approximately $150 each month in disposal costs.
SUMMARY
The audit of Plant A was performed to identify
opportunitiesforwastereduction. Thefollowinghazardous
wastes are generated by Plant A each month:
Industrial waste sludge- Approximately 200
gallons
Photoresist stripper waste- Approximately 60
gallons
Copper sulfate crystals- Undetermined
Nitric acid waste- Approximately 10 gallons
Reflow oil - Undetermined
Theauditprovided information that is useful to identify
several waste reduction techniques that may be feasible for
Plant A to implement. The following waste reduction
opportunities were identified:
Use process chemistries that can be recycled or
treated when they are spent instead of
chemistries that currently are containerized for
off-site disposal.
Usenon-chelatedprocesschemistriestoreplace
chelated chemistries.
Operate the rinse tanks as batch rinse systems.
56
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Reduce the flow rate used in the flow-through
rinse tanks.
Use flowrestrictorsandautomatedflow controls
to reduce rinse water usage.
Aggressively pursue drag-out reduction by
developingoperationalprocedures and training
personnel to slowly remove workpiece racks
and increase drainage time prior to rinsing.
Install a multiple-stage electroplating rack
cleaning line to reduce nitric acid waste
generation.
Reuse rinse water effluent from rinse systems
following acidic baths as rinse water influent to
rinsesystemsthatfollowalkalinecleaningbaths.
Mixcoppersulfatecrystalswithindustrial waste
sludge for off-site metals reclamation.
Segregate chelated waste streams from non-
chelated waste streams and batch treat them.
Dewatersludgeusingamechanicalfilterpress.
References
DHS. 1987. Waste Audit Study - Printed Circuit Board
Manufacturers. June 1987, Prepared for California
Department of Health Services, Alternative
Technology Section (Sacramento, California) by
Planning Research Corporation.
57
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PLANT B WASTE MINIMIZATION
ASSESSMENT
ThewasteminimizationassessmentofPlantB followed
the same protocol used for Plant A, and included:
Planning and organization
Assessment phase
Feasibility analysis phase
foplementationofselectedwasteminimization options
was left to the discretion of Plant B.
Planning and Organization
Planning and organization of the assessment were a
joint effort of the consulting firm and the PC board
manufacturingplant's operations manager. As summariized
in Figure 1, this phase of the assessment involved getting
company management commitment to the project, setting
goals for the assessment, and establishing a task force (the
consultants woridngin cooperation with theplantoperations
manager) to conduct the assessment
Assessment Phase: Process and Facility
Data
The consultants worked with the plant operations
manager to establish a data base of the facility's raw
material needs, materials handling procedures, and
operations processes. Blockflow diagrams were drawn up
to identify where materials are used and where waste is
generated. Initial study of this information and discussions
of waste stream concerns attheplantserved as preliminary
steps to thesiteinspection.duringwhich additional process
and waste handling information was obtained.
FACILITY DESCRIPTION
Plant B is a prototype circuit board manufacturer
specializing in jobs involving limited production and fast
turnaround. Manufacturing operations include drilling
and routing, layering (for multilayer boards), photoresist
printing, plating, etching, and stripping.
PROCESS DESCRIPTION
Figure B-l is a floor plan of the plant's plating and
etching process area. The numbers listed in the floor plan
represent the identification number for each process bath
and rinse tank. Tables B-l and B-2 describe Plant B's
rinsing operations andchemicalprocessbaths.respectively.
The plant presently uses seven dip tanks and two spray
rinse tanks. All the dip rinse tanks are equipped with pH/
conductivity meters that control the flow of water through
the rinse tanks. The spray rinse tanks are all operated with
foot pedals for turning on the water.
WASTE DESCRIPTION
Production activities that generate hazardous waste
are the plating, etching, and stripping processes. The
sources of waste from these activities arerinsing operations,
spentprocess bath dumping, and industrial waste treatment,
and equipment cleanout. This chapter describes the
hazardous waste generating and handling activities
performed at Plant B and describes the volume and
characteristics of the hazardous wastes generated. Table
B-3 lists Plant B's hazardous waste management
characteristics.
Rinsing Operations
Rinsing operations associated with the chemical
process lines are the major source of wastewater at Plant B.
Wastewater generation fluctuates betweenV.OOO to 11,000
gallons per day. Therinseoperationsconnibutetohazardous
waste generation because Waste rinse water carries away
chemicals which are then removed by treatment at the
industrial waste treatmentplanL The sludge that is generated
from this treatment is handled as a hazardous waste.
Spent Chemical Bath Dumping
Whenprocesschemicalbathsbecome too contaminated
or diluted for use (spent), it is removed from the process
tank. The spent chemical bath is then either containerized
for reclamation by the manufacturer, containerized for off-
site disposal, used as a neutralization chemical in the
industrial waste treatment system, or dumped into the
wastewater collection sump. A schedule for dumping each
spentprocess bath was not available from PlantB, butplant
personnel indicated that the frequency varies. A bath is
changed when personnel recognize that the effectiveness
of the bath is no longer adequate.
Only two of the spent bath handling methods contribute
to the amount of hazardous waste generated at the plant.
These methods include containerizing spent baths for off-
site disposal and dumping of spent chemical baths into the
wastewater sump. The only process chemical baths
containerized for disposal are the photoresist strippers and
the reflow oil. Approximately 25 gallons of waste reflow
oil is generated every 2 months. The volume of stripper
waste generated was not estimated by Plant B. Chemical
baths treated at the industrial waste treatment facility are
transferred to one of the two wastewater sumps where the
chemicals are neutralized. The waste is then fed into the
industrial waste treatment system.
Copper sulfate crystals are also generated when some
of the process baths are taken off-line. The crystals form
in the process bath as the copper concentration increases.
Before the process baths are dumped into the wastewater
sump, the crystals are containerized as a solid waste since
58
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Electroplating
7
8
9
10
(0
0)
c
c
U>
0)
a
2
o
ฃ
I
14
15
16
11
17
12
18
13
19
20
!
o
33
32
31
30
29
28
27
26
25
24
N
to
to
Q
Copper
Etcher
Copper
Etcher
Electroless Copper
Figure B-1 Plant B's Etching and Plating Facility
59
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RINSE WATER
FLOW CONTROLS
Table B-l. Rinse System Information
RINSE TANK/
NUMBER
Dip Rinse/1
Dip Rinse/3
Dip Rinse/5
Dip Rinse/12
Drag-out/14
Spray Rinse/15
Drag-out/18
Spray Rinse/19
Dip Rinse/26
Dip Rinse/27
Dip Rinse/30
Dip Rinse/32
Conditioner
pH/Conductivity
Meters
pH/Conductivity
Meters
pH/Conductivity
Meters
pH/Conductivity
Meters
Manual Dumping
Footpedals
Manual Dumping
Footpedals
pH/Conductiv'rty
Meters
pH/Conductiv'rty
Meters
pH/Conductivfty
Meters
pH/Conductivity
Meters
NUMBER
OF TANKS
IN SYSTEM
one
one
one
one
one ,
one
one
one
two
two
one
one
COUNTER
CURRENT
SYSTEM
no
no
no
no
NA
NA
NA
NA
no
no
no
no
PROCESS BATH
PRECEDING
RINSE
Ammonium
Bifluoride/2
MBL Cleaner/4
98% Sulfuric
Acid/6
Black Oxide/11 and
Tin Immerse/13
Drag-out Tank/14
Drag-out Tank/18
Rinse Tank/27
Catalyst
Sulfuric-Peroxide
Etch/31
Cleaner-
/33
60
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fable B-2. Process Bath Information
PROCESS BATH/
NUMBER
Ammonium Bifluoride/2
MBL Cleaner/4
98% Sulfuric Acid/6
tin-Lead Bath/7
Fluorboric Acid/8
Copper Sulfate/9
Copper Sulf ate/10
Black Oxide/11
Tin Immerse/13
10% Sulfuric Acid/16
Sulfuric/Peroxide Etch/17
Soap Cleaner/20
Reflow Flux/21
Reflow OiV22
Reflow Oil/23
Electroless Copper/24
Accelerator/25
Catalyst/28
Catalyst Prep/29
Sulfuric-Peroxide Etch/31
Cleaner-Conditioner/33
PROCESS BATH
VOLUME (gallons)
50 gal.
50 gal.
20 gat.
400'gal.
50 gal.
400 gal.
400 gal.
50 gal.
50 gal.
50 gal.
50 gal.
50 gal.
2gal.
15gal.
15gaL
50 gal.
50 gal.
50 gal.
50 gal.
50 gal.
50 gal.
METHOD OF
DISPOSAL
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To Wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
Off-site disposal
Off-site disposal
Off-site disposal
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
To wastewater treatment facility
Table B-3. HazardousWaste Data
WASTE
Industrial
Treatment
Sludge
Photoresist
Stripper
Nitric Acid
Reflow Oil
ANNUAL
QUANTITY
GENERATED
300 gal.
30 gal.
150 gal.
DISPOSAL
METHOD
Off-site
metal
reclamation
Off-site
disposal
Off-site
disposal
Off-site
disposal
DISPOSAL
COST/UNIT
$40/55 gal.
drum
$100/55 gal.
drum
$100/55 gal.$50
drum
$100/55 gal.
drum
ANNUAL
DISPOSAL
COSTS
$240
$300
61
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they cannot be fed into the treatment system. The crystals
are mixed with the plant's industrial waste sludge, which is
transported offsite for metal reclamation.
Industrial Wastewater Treatment
Plant B's industrial waste treatment facility treats all
wastewater prior to discharge to the San Jose/Santa Clara
Water Pollution Control Plant. Plant B's treatment facility
removes metals and adjusts the pH of the wastewater to
meet the maximum allowable concentration of metals in
the discharged effluent, as set by the San Jose/Santa Clara
Water Pollution Control Plant. These maximum
concentrations are as follows:
Chromium
Copper
Cyanide
Lead
Nickel
Silver
Zinc
l.Omg/L
2.7mg/L
l.Omg/L
0.4mg/L
2.6mg/L
0.7mg/L
2.6mg/L
The treatment process includes neutralization, metals
precipitation, filtration, and sludge dewatering. The
treatment plant is located outside the main building in a
curbed area The metal hydroxide sludge generated by this
treatment process is a hazardous waste. The treatment
system generates approximately 25 gallons of sludge every
month. The sludge dewatering unit produces a sludge that
has a solids concentration of 35 percent. The sludge is
transportedoffsitetoWorldResourcesofPhoenix, Arizona
for metal reclamation. WorldResources analyzes a sample
from each load of sludge it receives. The analytical data
provided by World Resources for the sludge generated by
Plant B are as follows:
Percent solids 35%
Metal content in pounds per dry ton
Copper 250
Nickel 11
Tin 59
Iron
Lead
Zinc
12
22
8
Equipment Cleanout
The primary source of hazardous waste associated
with equipment cleanout is the cleaning of electroplating
racks. Plant B uses nitric acid in a five tank cleaning line
tocleanelectroplatingracks.Eachtankholds approximately
15 gallons of nitric acid. The acid in the first tank requires
changing approximately every 6 months. When the nitric
acid in the first tank is dumped, the remaining four tanks all
move up one step in the cleaning line. The empty tank is
filled with fresh nitric acid and is used as the last tank in the
cleaning line. The waste nitric acid has too low a pH and
too high a copper content to be treated in the industrial
waste treatment system.
Other cleaning activities, such as floor washing and
chemical bath tank rinsing, generate waste streams that
discharge into the wastewater collection sump. According
to Plant B personnel, these waste streams make up a small
portion of the chemicals that enter the treatment system.
Assessment Phase: Option Generation
After the site inspection, the plant operations manager
andtheconsultantteam reviewed therawmaterial.process,
and waste stream information and developed a number of
waste minimization options for consideration. These
options fall into the categories of source reduction
techniques andrecyclingandresourcerecovery techniques.
SOURCE REDUCTION MEASURES
PlantB appears to haveeffectivelyimplemented several
technologies to reduce the volume of hazardous waste it
generates. Water conservation techniques, such as rinse
water flow control meters and pressure activated spray
rinse tanks, are presently used at the plant. The industrial
waste treatment system appears to effectively treat
wastewater withoutproducing excessive volumes of sludge.
Plant B personnel stated that their effluent consistently
meets the discharge requirements setby the San Jose/Santa
Clara Water Pollution Control Plant. Also, the volume of
sludge generated by the wastewater treatment system is
lower than the volume generated at other manufacturing
plants of comparable size and wastewater generation rates.
For example, Plant B generates approximately 50 gallons
of sludge every 2 months compared to another plant with
a comparable wastewater generation rate that generates
approximately 200 gallons of sludge every month.
Nevertheless, several additional opportunities for waste
reduction may be available to Plant B that can further
reduce its hazardous waste generation. This section
describes these opportunities.
MATERIAL SUBSTITUTION
Plant B may be able to reduce the volume of spent
process chemicals and cleaning solutions containerized for
off-site disposal by substituting materials. Two materials
thatPlant B handles as hazardous waste are spentreflow oil
62
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and spent nitric acid. Several reflow oil products are
available that, when spent, either can be returned to the
supplier for recycling or can be treated by the facility prior
to discharge to the Publicly Owned Treatment Works.
Plant B could eliminate a hazardous waste stream by
replacingitspresentreflow oil witharecyclable or treatable
reflow oil. '
Nitric acid waste, which is generated from the cleaning
of electroplating racks, can also be eliminated by using an
alternative cleaning solution. One chemical supplier offers
an electroplating rack cleaning solution that can be
regenerated. The metal stripped off of racks during the
cleaning process can be plated out in a tank equipped with
a cathode and an anode. The metal stripped from the racks
is plated onto the cathode and forms a metallic sludge that
settles to the bottom of the cleaning tank. Once the solution
becomes spent, it can be treated in the plant's industrial
treatment system instead of being containerized foroff-site
disposal. Plant B should consult with chemical suppliers
to identify alternative materials that can be recycled or
treated and that willmeetits specific operatingrequirements.
DRAG-OUT LOSS REDUCTION
Discussions with Plant B personnel indicated that
little attention is placed on drag-out reduction. Although
the plant does not generate excessive amounts of sludge,
further reductions in sludge volume may be obtained by
using drag-outreduction technologies. Reductions in drag-
out loss should also have a direct impact on water usage.
Since water flow through the rinse systems are controlled
by pH/conductivity controls, drag-out reduction will
decrease the frequency of rinse water flow through the
rinse tanks. Plant B may be able to reduce drag-out by
instituting operational modificationsandtrainingpersonnel
in drag-out reduction techniques. Drag-out reduction
techniques include slowing the workpiece rack withdrawal
rates and increasing drainage time prior to rinsing. Other
drag-outreductionmethods include operatingprocess baths
at the lowest allowable concentration and using heated
process baths when possible.
The faster an item is removed from the process bath,
the thicker the film on the workpiece surface and the
greater the drag-out volume will be. The effect is so
significant that most of the time allowed for withdrawal
and drainage of a rack should be used for withdrawal only.
Plant B management should emphasize to process line
operators that workpieces shouldbe withdrawn slowly. An
optimal removal rate can be determined by removing
loaded workpiece racks from process baths at different-
rates and allowing the rack to drain into a catch basin.
Drag-out volume can then be measured volumetrically.
Workpiece drainage also depends on the operator.
The time allowed for drainage can be inadequate if the
operator is rushed to remove the workpiece rack from the
process bath and place it in the rinse tank. However,
installation of a bar or rail above the process tank may help
ensure that adequate drainage time is provided prior to
rinsing. Plant B has expressed concern that increasing
workpiece rack removal and drainage time will allow for
chemical oxidation on the board. Plant B should identify
the processes that are not highly susceptible to oxidation
and emphasize drag-out minimization techniques to
personnel operating those processes.
RINSE WATER RECYCLING
Plant B may be able to recycle its rinse water by further
treating effluent from the industrial waste treatment plant.
Thisadditionaltreatmentmayonlyrequireactivated carbon
treatment to remove trace organics from the water. Plant
B should assess the need for other levels of treatment, such
as ion-exchange or other technologies, based on the quality
of the treated effluent This recycled water would contain
less natural contaminants, such as phosphates and
carbonates, than tap water, which is presently used. Since
these natural contaminants contribute to sludge volume
because they precipitateduring treatment, theuseof recycled
rinse water can reduce hazardous waste sludge generation
and significantly reduce water usage and sewer discharge
fees.
Feasibility Analysis Phase
After discussions with Plant B personnel, some of the
options discussed in the previous section were selected for
investigation of their technical and economic feasibility.
The economic analysis was based on the raw material and
waste disposal costs provided by the facility personnel and
on economic and technical information provided by
equipment manufacturers. The measures evaluated in this
section include: material substitution, drag-out loss
reduction and rinse water recycling.
MATERIAL SUBSTITUTION
The benefits associated with using recyclable and/or
treatable process chemistries will depend on the costs of
substitute materials compared with the costs of materials
presently used. Also, additional process bath maintenance
requirements and treatment costs need to be identified.
These costs will depend on the type of substitute material
chosen by Plant B.
Savings will include reduced waste disposal costs and
material usage costs if the substitute material can be
recycled. PlantB generates 150 gallons of waste reflow oil
and 30 gallons of waste nitric acid annually. Since waste
disposal costs for the waste reflow oil and waste nitric acid
are both $100 per 55-gallon drum, which is the average cost
63
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for disposing of various liquid hazardous wastes according
to PC board manufacturers, waste disposal cost savings
would be approximately $300 per year for spent reflow oil
and 550 per year for nitric acid waste. Actual savings
associated with using recyclable reflow oil and nitric acid
will depend on the difference in the cost of the substitute
materials.
DRAG-OUT LOSS REDUCTION
Several drag-out minimization techniques can be
implementedatPlantB for minimal costs. Theuseof abar
rail above each process tank for hanging workpiece racks
will allow for greater drainage time before rinsing. This
couldbe ins tailed by Plant B's personnel for a few hundred
dollars if constructed of 1 inch PVC piping. Other drag-out
reduction techniques, such as slowing workpiece rack
removal rates and operating process baths at the lowest
possible concentration, can also be implemented for little
cost. Developing a training program and emphasizing
drag-outminirnization will require time from management
and operations personnel. Since information on drag-out
rates and workpiece rackremoval and drainage times were
not available from Plant B, savings associated with drag-
out minimization cannot be quantified prior to
implementation.
RINSE WATER RECYCLING
Considerable capital investment may be needed to
recycle wastewater for reuse in production. The costs
associated with recycling treated wastewater effluent will
depend on the level of additional treatment necessary to
return the effluent back into the production processes.
Other plants lhat are considering rinse water recycling
have indicated that their primary concern is to remove
organics from the treated effluent before reusing the water.
An activated carbon system to treat theeffluentcan be used
to remove organics from the water. If various anions and/
or cations in the effluent must also be removed, treatment
technologies such asreverseosmosisorion-exchangemay
be required.
Information describing the rinse system operating
parameters and the water quality or Plant B's treated
effluent were not obtained during the audit. Therefore,
treatmentrequirements for returning treated effluent to the
rinse systems could not be developed. Plant B should
investigate the potential for recycling rinse water by
characterizing its rinse water effluent, determining the
water quality needs for reusing treated effluent, and
identifying potential technologies that can be used to treat
the effluent for reuse.
The primary savings associated with recycling rinse
water is lower water purchase and sewer discharge fees.
PlantBgeneratesapproximately7,000 to 11,000 gallons of
wastewater each day. For an average daily water usage of
9,000 gallons, and assuming that 90 percent of the water
can be recycled, Plant B could reuse approximately 8,000
gallons of water each day. Since water and sewer fees are
both approximately $0.50 per 750 gallons, Plant B could
save approximately $ 10 each day in water and sewer costs.
SUMMARY
The audit of the Plant B was performed to identify
opportunities forwaste reduction. Thefollowing hazardous
wastes are generated by Plant B annually:
Industrial waste sludge- Approximately 300
gallons
Photoresist stripper waste- Undetermined
Copper sulfate crystals- Undetermined
Nitric acid waste- Approximately 30 gallons
Reflow oil- Approximately 150 gallons
The audit was used to identify several waste reduction
techniques that may be feasible for Plant B to implement.
The following waste reduction opportunities were
identified:
Use alternative reflow oil and electroplating
rack stripper materials that can be recycled or
treated when they are spent instead of
chemistries that currently are containerized for
off-site disposal.
Aggressively pursue drag-out reduction by
developing operational procedures and training
personnel to slowly remove workpiece racks
and increase drainage time prior to rinsing.
Recycle treated effluent for reuse in the
production process.
64
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PLANT C WASTE MINIMIZATION
ASSESSMENT
The wasteminimization assessment ofPlantC followed
the same protocol used for Plant A, and included:
Planning and organization
Assessment phase
Feasibility analysis phase
Implementation of selected wasteminimization options
was left to the discretion of Plant C.
Planning and Organization
Planning and organization of the assessment were a
joint effort of the consulting firm and the paint
manufacturingplant'soperations manager. As summarized
inFigure 1, this phase of the assessment involved getting
company management commitment to the project, setting
goals for the assessment, and establishing a task force (the
consultants workingin cooperation with theplantoperations
manager) to conduct the assessment
Assessment Phase: Process and Facility
Data
The consultants worked with the plant operations
manager to establish a data base of the facility's raw
material needs, materials handling procedures, and
operations processes. Block flow diagrams were drawn up
Jo identify where materials are used and were waste is
generated. Initial study of this information and discussions
of waste stream concerns at the plant served as preliminary
steps to thesiteinspection.duringwhich additional process
and waste handling information was obtained.
FACILITY DESCRIPTION
Plant C is a prototype circuit board manufacturer
specializing in jobs involving limited production and fast
turnaround. Manufacturing operations include drilling
and routing, layering (for multilayer boards), plating, and
etching.
PROCESS DESCRIPTION
Figure C-l is a floor plan of the plant's plating and
etching process area. The numbers listed on the floor plan
represent the identification number for each process bath
and rinse tank. Tables C-l and C-2 describe Plant C's
rinsing operationsandchemicalprocessbaths.respectively.
WASTE DESCRIPTION
Production activities that generate hazardous waste
are the plating and etching processes. The sources of waste
from these activities are rinsing operations, spent process
bath dumping, industrial waste treatment, and equipment
cleanout. This chapter of thereport describes the hazardous
waste generating and handling activities performed at
Plant C and describes the volume and characteristics of the
hazardous wastes generated. Table C-3 lists Plant C's
hazardous waste management characteristics.
Rinsing Operations
Rinsing operations associated with the chemical
process lines are the major source of wastewater at Plant C.
Facilitypersonnel estimate that approximately 3,000 gallons
of wastewater are generated each day. The rinse operations
contribute to hazardous waste generation because waste
rinse water carries away chemicals which are then removed
by treatment at the industrial waste treatment plant. The
sludge waste that is generated from this treatment is then
handled as a hazardous waste.
The plant uses 11 dip rinse tanks that discharge to the
industrial waste treatmentplantandtwodrag-outtanks that
are periodically dumped manually into the wastewater
sump. All of the rinse tanks are plumbed directly to the
wastewater treatment system via a collection sump.
Discussions with facility personnel indicate that water
flows through the dip rinse tanks only when the process line
associated with the tank is in operation. Water flow for
each rinse tank is turned on and of f manually by production
personnel. Plant C installed flow restrictors in each rinse
system's water inflow line to control water usage.
Four of the rinsing operations are double rinse tank
system (tanks 5 and 6, tanks 15 and 16, tanks 21 and 22, and
tanks 30 and 31). These four rinse systems, however, are
not plumbed in series as counter-current rinse systems.
Instead, each tank has a separate rinse water influent and
effluent water line.
Spent Chemical Bath Dumping
Whenprocesschemicalbaths become too contaminated
or diluted for use (spent), they are removed from the-
process tank. The spent chemical bath is then either
containerized for reclamation by the manufacturer,
containerized for off-site disposal, or dumped into the
wastewater collection sump. A schedule for dumping each
spent process bath was not available from Plant C, but plant
personnel indicated that the frequency varies. A bath is
changed when personnel recognize that the effectiveness
of the bam is no longer adequate.
Only two ofthespentbathhandlingmethods contribute
to the amount of hazardous waste generated at the plant.
Thesemethods are containerizingwasteforoff-site disposal
and dumping of spent chemical bath into the wastewater
sump. The processchemicalbathcontainerizedfor disposal
is the reflow oil. The plant generates approximately 20
gallons of waste reflow oil each month.
65
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Chemical
Storage
Area
26
27
Electroplating
28
29
Electroplating Precleaning
Etching
Wastewater
Treatment
System
18
Board Scrubber
10
11
12
13
14
15
16
Reflow
30
31
17
9
Electroless Copper
8
7
6
5
4
3
2
1
Figure C-1. Plant C's Etching And Plating Facility
66
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Table C-l. Rinse System Information
RINSE SYSTEM
NUMBER
Dip Rinse/3
Dip Rinse/5
Dip Rinse/6
Dip Rinse/9
Dip Rinse/12
Dip Rinse/15
Dip Rinse/16
Dip Rinse/20
Dip Rinse/21
Drag-out/27
Drag-out/29
Dip Rinse/30
Dip Rinse/31
NUMBER
OF TANKS
One
Two
Two
One
One
Two
Two
Two
Two
One
One
Two
Two
COUNTER
CURRENT
SYSTEM
No
No
No
No
No
No
No
No
No
No
No
No
No
PROCESS BATH
PRECEDING RINSE
SYSTEM
Soap Cleaner/2
Peroxide Etchback/4
Dip Rinse Tank/5
Catalysl/8
Electroless Copper/11
Tin/Lead Stripper/14
Dip Rinse Tank/5
Micro Etch Cleaner/19
Dip Rinse Tank/20
Copper Sulfate/26
Tin-Lead/28
Reflow Oil/17
Reflow Oil/17
Table C-2. Process Bath Information
PROCESS BATH/
IDENTIFICATION NUMBER
Nickel Sulfate/1
Soap Cleaner/2
Peroxide Etchback/4
10% Hydrochloric Acid/7
Catalyst/8
Accelerator/10
Electroless Copper/11
10% Hydrochloric Acid/13
Tin/Lead Stripper/14
Reflow Oil/17
Ammonium Etchant/18
Micro Etch Cleaner/19
Sulfuric Acid/22
Fluorboric Acid/23
Solder Bright/24
Nitric Acid/25
Copper Sulfate/26
Tin-Lead/28
PROCESS BATH
VOLUME IN TANK
30 gal.
30 gal.
30 gal.
30 gal.
30 gal.
30 gal.
30 gal.
30 gal.
30 gal.
20 gal.
50 gal.
50 gal.
50 gal.
50 gal.
50 gal.
400 gal.
400 gal.
METHOD OF
DISPOSAL
Discharge to treatment facility
Discharge to treatment facility
Discharge to treatment facility
Discharge to treatment facility
Replenished, not disposed
Discharge to treatment facility
Replenished, not disposed
Discharged to treatment facility
Discharged to treatment facility
Off-site disposal
Recycled by manufacturer
Discharged to treatment facility
Discharged to treatment facility
Discharged to treatment facility
Discharged to treatment facility
Off-site disposal
Replenished, not disposed
Replenished, not disposed
67
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Table C-3. Hazardous Waste Data
WASTE
Spent Ion
Exchange Resin
Nitric Acid
Reflow Oil
ANNUAL
QUANTITY
GENERATED
1200 gal.
480 gal.
240 gal
Copper Sulfate Undetermined
Crystals
DISPOSAL
METHOD
Transported
off-site for
disposal
Transported
off-site for
disposal
Transported
off-site for
disposal
Transported
off-site for
disposal
DISPOSAL
COST/UNIT
$2.00/gal.
$2.00/gal.
$2.00/gal.
$2.00/gal.
ANNUAL
DISPOSAL
COSTS
$2,400
$ 960
$ 480
Other process baths are discharged to the treatment
plant when they are spent (except for the etchant, which is
sent back to the supplier for reclaim). Copper sulfate
crystals are also generated when some of the process baths,
such as the peroxide/sulfuric etch, are taken off-line. The
crystals form in the process bath as the copper content
increases. Before the process baths are dumped into the
wastewater sump, the crystals are removed and
containerized as a solid hazardous waste since they cannot
be fed into the treatment system. Plant C did not estimate
the volume of copper sulfate crystals generated each month.
Industrial Wastewater Treatment
Plant C's industrial waste treatment facility treats all
wastewater prior to discharge to the San Jose/Santa Clara.
Water Pollution ControlPlant. Plant C's treatment facility
removes metals and adjusts the pH of the wastewater to
meet the maximum allowable concentration of metals in
the discharged effluent, as set by the San Jose/Santa Clara
Water Pollution Control Plant. These maximum
concentrations are as follows:
Chromium
Copper
Cyanide
Lead
Nickel
Silver
Zinc
l.Omg/L
2.7mg/L
l.Omg/L
0.4mg/L
2.6mg/L
0.7mg/L
2.6mg/L
The treatmentprocess includes filtration, ion-exchange,
and neutralization. The ion-exchange (IE) system was
recently installed to replace Plant C's conventional
precipitation/clarifier treatment system. ThelonExchange
unit has a treatment capacity of 12 to 14 gallons per minute.
The Ion Exchange unit produces less hazardous waste than
the old treatment system. The hazardous waste generated
by thelonExchange treatmentprocess is spention-exchange
resin. Approximately 100 gallons of waste resin are
generated each month, compared to approximately 300
gallons of sludge generated by the old treatment system.
Equipment Cleanout
The primary source of hazardous waste associated
with equipment cleanout is the cleaning of the copper
etching tank, the tanks used in the electroplating line, and
the electroplating racks. This equipment is cleaned by
using nitric acid. Plant C estimates that approximately 40
gallons of waste nitric acid are generated each month. The
waste nitric acid has too low of a pH and too high of a
copper content to be discharged to the treatment facility.
The nitric acid solution is stored in a single 50-gallon
tank where electroplating racks can be immersed in the
solution for cleaning. The nitric acid is used to strip the
copper, tin, and lead from the equipment When the acid
loses its ability to effectively oxidize the metal, it is
containerized for disposal. Electroplating rack cleaning is
the greatest source of waste nitric acid.
Assessment Phase: Option Generation
After the site inspection, the plant operations manager
and the consultantteam reviewed theraw material, process,
and waste stream information and developed a number of
waste minimization options for consideration. These
68
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options fall into the categories of source reduction
techniques andrecyclingandresourcerecovery techniques.
SOURCE REDUCTION MEASURES
PlantCappearstohaveeffectivelyimplementedseveral
technologies to reduce the volume of hazardous waste it
generates. Water conservation techniques such as rinse
water flow restrictors are presently used at Plant C, the
plant's water use appears to be significantly lower than that
of other plants of comparable size and production. For
example, two otherplantsvisitedbytheconsultant generate
approximately 10,000 gallons of wastewater each day
compared to 3,000 gallons generated by Plant C each day.
The ion exchange treatment system effectively treats
wastewater without producing a hazardous waste sludge.
This new treatment system produces approximately 100
gallons of spent ion exchange resin each month, with no
sludge generated;, the old treatment facility produced
approximately 300 gallons of sludge each month.
Nevertheless, several additional opportunities for waste
reduction may be available to Plant C to further reduce its
hazardous waste generation. This section describes these
opportunities.
Material Substitution
Plant C may be able to reduce the volume of spent
process chemicals and cleaning solutions containerized for
off-site disposal by substituting materials. Two materials
thatPlant C handles as hazardous waste are spentreflow oil
and spent nitric acid. Several reflow oil products are
available that, when spent, either can be returned to the
supplier for recycling or can be treated by the facility prior
to discharge to the Publicly Owned Treatment Works.
Plant C could eliminate a hazardous waste stream by
replacing itspresentreflow oil with arecyclableor treatable
reflow oil.
Nitric acid waste, which is generated from equipment
cleanout, can also be eliminated by using an alternative
cleaning solution. One chemical supplier offers an
electroplatingrack cleaning solution that can beregenerated.
The metal stripped off of racks during the cleaning process
can be plated out in a tank equipped with a cathode and an
anode. In this method, metal stripped from the racks is
plated onto the cathode and forms a metallic sludge that
settles to the bottom of the cleaning tank. Once the solution
becomes spent, it can be treated in the plant's industrial
treatment system instead ofbeingcontainerizedforoff-sife
disposal. Plant C should consult with chemical suppliers
to identify alternative materials that can be recycled or
treated and that will meetits specific operatingrequirements.
RINSE WATER REDUCTION
Plant C can reduce rinse water usage, as well as reduce
the quantity of hazardous chemicals entering the waste
stream, by converting several of its double tank rinse
systems into two-stage, closed circuit counter-currentrinse
systems. By reducing water usage and quantity of chemical
wastes, the load on the treatment system will be reduced
and thelongevity of theionexchangeresincan be increased.
The plant currently uses four double tank rinse systems
(tanks 5 and 6, tanks 15 and 16, tanks 20 and 21, and tanks
30 and 31; see Figure Cl). Each tank, however, is plumbed
separately. If the two tanks associated with each of the four
rinse systems were plumbed in series as counter-current
rinse systems, the plant could significantly reduce its rinse
water use. Figure C2 illustrates the set-up for a two stage
counter-currentrinse system.
Plant C did not provide data on the flow rate used for
each rinse tank. Therefore, calculations on actual water use
savings cannot be presented. However, the following
example illustrates how a counter-current rinse system can
reduce water use compared with the present rinse system
used at the plant. A facility operates a two stage rinse
system with: (1) each tank having a separate water inflow
line; (2) a water flow rate of 10 gallons per minute; and (3)
the rinse water for the system turned on a total of 120
minutes per day. The total water usage for this system
would be 2,400 gallons per day. The following equation
can be used to illustrate how a two stage counter-current
system could reduce rinse water usage at the facility:
Q= [(Cp/Cr)l/n+l/n]D
Q= rinse tank flow rate
D= drag-out rate
Cp = chemical concentration on process
solution
Cr = allowable chemical concentration in
rinse solution
n = number of rinse tanks in series
Severalassumptionsmustbemadetousethisequation.
These are as follows:
The concentration of chemicals in the rinse
solution cannot exceed 1/1000 of the
concentration of chemicals in the process bath.
This value is a common parameter used in the
electroplating industry for rinse .water
contaminant concentration.
69
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The drag-out rate of chemicals used for
manufacturing printed circuit boards is
approximately 15 ml/ft2 of board. Thisvalueis
a standard approximation used for estimating
drag-but created by a printed circuit board.
Anaverageworkpiecerackholdsapproximately
2.5 ft3 of boards (example: 30 4-inch by 3-inch
boards).
The drag-out rate for each workpiece rack is:
15mlx2.5ft3 = 37.5ml.
Converted to gallons, drag-out equals 0.01 gallon.
By substituting the values into the equation:
[(1000)1/2 + 1/2] 0.01 gallons/minute = 0.32 gallon/
minute.
Therefore, if the facility converted its existing rinse
system intoatwo-stageclosedckcuitcounter-currentrinse
system, it could reduce the flow rate from 10 gallons per
minute through each tank to0.32gallonper minute through
both tanks. This would in theory reduce the daily water
usage from 2,400 gallons to 38 gallons and would
significantly reduce the quantity of hazardous chemicals
entering the shop's treatment system. The actual volume of
rinse water reduction that can be achieved by Plant C
depends on the drag-outrate from the plant's process baths
and the rinse system parameters for the four double rinse
tank systems.
DRAG-OUT LOSS REDUCTION
Discussions with Plant C personnel indicated that
little attention is placed on drag-out reduction. The plant
may be able to generate less spent ion-exchange resin by
using drag-out reduction technologies. Reductions in
drag-out loss should also have a direct impact on water
usage. Since water flow through the rinse systems are
controlledbypH/conductivity controls, drag-outreduction
will decrease the frequency of rinse water flow through the
rinse tanks. Plant C may be able to reduce drag-out by
institutingoperationalmodificationsandtrainingpersonnel
in drag-out reduction techniques. Drag-out reduction
techniques include slowing workpiece rack withdrawal
rates and increasing drainage time prior to rinsing. Other
drag-outreductionmethodsincludeoperatingprocess baths
at the lowest allowable concentration and using heated
process baths when possible.
The faster an item is removed from the process bath,
the thicker the film on the workpiece surface and the
greater the drag-out volume will be. The effect is so
significant that most of the time allowed for withdrawal
and drainage of arack should be usedfor withdrawal only.
Plant C management should emphasize to process line
operators that workpieces shouldbe withdrawn slowly. An
optimal removal rate can be determined by removing
loaded workpiece racks.from process baths at different
rates and allowing the racks to drain into a catch basin.
Drag-out volume can then be measured volumetricaUy.
Workpiece drainage also depends on the operator.
The time allowed for drainage can be inadequate if the
operator is rushed to remove the workpiece rack from the
process bath and place it in the rinse tank. However,
installation of a bar or rail above the process tank may help
ensure that adequate drainage time is provided prior to
rinsing. Other printed circuit board manufacturers have
expressed concern that increasing workpiece rack removal
and drainage time will allow for chemical oxidation on the
board. Plant C should identify the processes that are not
highly susceptible to oxidation and emphasize drag-out
minimization techniques to personnel operating those
processes.
EQUIPMENT CLEANOUT
Plant C generates approximately 40 gallons of waste
nitric acid every month from equipment cleanout. Plant C
may be able to reduce the volume of nitric acid generated
by modifying the existing cleaning methods.
One method for reducing the volume of waste nitric
acid produced is to setup a workpiece rack cleaning line
with several small tanks of nitric acid. The cleaning line is
then used like a multi-stage rinse system. The first tank
con tains the most contaminated nitric acid solution, and the
final tank in the cleaning line contains the freshest nitric
acid. When the first tank no longer performs adequate
initial cleaning, it is containerized for disposal (or used as
initial cleaning solution for tank cleanout). Then the
second tank in the cleaning line becomes the first. The
empty tank is then filled with fresh nitric acid and it
becomes the last tank in the cleaning line.
The use of a multi-stage rinse system can provide
signiflcantreductions in wastecleaning solution generation.
One printed circuit board manufacturing plant uses a five-
stage multiple tank cleaning line and only generates
approximately 15 gallons of waste nitric acid each 6
months.
RINSE WATER RECYCLING
Plant C may be able to recycle its rinse water by further
treating effluent from the industrial waste treatment plant.
This additional treatmentmayonlyrequireactivated carbon
treatment to remove trace organics from the water. This
recycled water would contain less natural contaminants,
such as phosphates and carbonates, than the tap water that
is presently used. Since these natural contaminants
70
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Path of Work
f
Process
Bath
i
1st
Rinse
.
2nd
Rinse
FT
Path of Makeup Water
Figure C-2. Multiple Closed Circuit Counterflow Rinse System
contribute to ion-exchange resin use because they are
removed during treatment, recycling of rinse waters can
reduce spent resin generation and significantly reduced
water usage and sewer discharge fees.
Feasibility Analysis Phase
After discussions with Plant C personnel, some of the
options discussed in the previous section were selected for
investigation of their technical and economic feasibility.
The economic analysis was based on the raw material and
waste disposal costs provided by the facility personnel and
on economic and technical information provided by
equipment manufacturers. The measures evaluated in this
section include: material substitution, rinse water reduction,
drag-out loss reduction, equipment cleanout reduction and
rinse water recycling.
MATERIAL SUBSTITUTION
The benefits associated with using recyclable and/or
treatable process chemistries will depend on the costs of
substitute materials compared with the costs of materials
presently used. Also, additional process bath maintenance
requirements and treatment costs need to be identified.
These costs win depend on the type of substitute material
chosen by Plant C.
Savings will include reduced waste disposal costs and
material usage costs if the substitute material can be
recycled onsite. Plant C generates approximately 250
gallons of waste reflow oil and 500 gallons of waste nitric
acid annually. Since waste disposal costs for the waste
reflow oil and waste nitric acid are both $ 100 per 55-gallon
drum, which is the average cost for disposing of various
liquid hazardous wastes according to circuit board
manufacturers, waste disposal cost savings would be
approximately $500 per year for spent reflow oil disposal
and $1,000 per year for nitric acid waste. Actual savings
associated with using recyclable reflow oil and nitric acid
will depend on the difference in cost of the substitute
materials.
RINSE WATER REDUCTION
The costs associated with converting the plant's four
double tank rinse systems into two stage counter-current
rinse systems would be minimal. Since the pairs of tanks
are already next to each other, the only modifications
necessary would be to re-plumb each rinse system. This
could be done by Plant C personnel for less than a few
hundred dollars. Savings would include reduced water use
and sewer fees and reduced ion exchange resin purchases.
Since rinse water flow rates, drag-out rates, and rinse
71
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system operating parameters were not available, we could
notcalculate estimates on savings in water use, sewer fees,
and ion exchange resin purchases.
DRAG-OUT LOSS REDUCTION
The use of a bar rail above each process tank for
hanging workpiece racks will allow for greater drainage
time before rinsing. This could be installed by Plant C's
personnel for a few hundred dollars if constructed of 1 inch
PVC piping. Other drag-out reduction techniques, such as
slowingworkpiecerackremovalratesandoperatingprocess
baths at the lowest possible concentration, can also be
implementedforlitflecosL Developing a training program
and emphasizing drag-out minimization will require time
from management and operations personnel. Since
information on drag-outrates and workpiece rackremoval
and drainage times werenotavailablefromPlantC, savings
associated with drag-outminimizationcannotbe quantified
prior to implementation.
EQUIPMENT CLEANOUT REDUCTION
Plant C can reduce waste nitric acid generation by
using a multiple tank cleaning line. The costs associated
with setting up such a system include the cost of additional
tanks and the installation labor costs. The costs for setting
up a cascade cleaning line would be approximately $350
per tank. Labor costs of $55 an hour for 4 hours would be
$220.
The savings associated with a multiple tank plating
rack cleaning line include reduced costs for nitric'acid
purchases and waste acid handling. Plant C now generates
approximately 480 gallons of waste nitric acid annually.
The consultants visited one plant that used five 30-gallon
tanksasamultiplestagecleaningline. Thatplantgenerates
30-gallons of waste nitric acid each year. If Plant C could
reduce its waste nitric acid generation down to 30 gallons
per year, it would achieve an annual savings of
approximately $1,400 in nitric acid purchases and $800 in
waste disposal costs. This assumes that nitric acid costs
$3.10 per gallon and waste disposal costs are $ 100 per 55-
gallon drum.
RINSE WATER RECYCLING
Considerable capital investment may be needed to
recycle wastewater for reuse in production. The costs
associated with recycling treated wastewater effluent will
depend on the level of additional treatment necessary to
return the effluent back into the production processes.
Other plants that are considering rinse water recycling
have indicated that their primary concern is to remove
organics from the treated effluent before reusing the water.
An activated carbon system to treat theeffluent can be used
to remove organics from the water. Waste treatment
effluent data for the plant were not available from Plant C.
Therefore, specific treatment requirements for recycling
treated effluent could not be identified. Plant C should
investigate the potential for recycling rinse water by
characterizing its rinse water effluent, determining the
water quality needs for reusing treated effluent, and
identifying potential technologies that can be used to treat
the effluent for reuse.
The primary savings associated with recycling rinse
water are lower water purchase and sewer discharge fees.
Plant C generates approximately 3,000 gallons of
wastewater each day. Assuming that 90 percent of the
water can be recycled, Plant C could reuse approximately
2,700 gallons of water each day. If water and sewer fees are
both$0.5per750gallons,PlantCcouldsave approximately
$75 each month in water and sewer costs, assuming a 20-
day work month.
SUMMARY
The audit of Plant C was performed to identify
opportunities for waste reduction. Thefollowinghazardous
wastes are generated by Plant C each month:
Spent Ion Exchange Resin - Approximately
100 gallons
Copper Sulfate Crystals- Undetermined
Nitric Acid Waste- Approximately 40 gallons
Reflow Oil- Approximately 20 gallons
Theauditprovided information that was used to identify
several waste reduction techniques that may be feasible for
Plant C to implement The following waste reduction
opportunities were identified:
Use alternative reflow oil and electroplating
rack stripper materials that can be recycled or
treated when they are spent instead of
chemistries that currently are containerized for
off-site disposal.
Aggressively pursue drag-out reduction by
developing operationalprocedures and training
personnel to slowly remove workpiece racks
and increase.drainage time prior to rinsing.
Convert the four double tankrinse systems into
two-stage counter-current rinse systems.
Install a multiple stage electroplating rack
cleaning line to reduce nitric acid waste
generation.
Recycle treated effluent for reuse in the
production process.
72
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APPENDIX B
WHERE TO GET HELP
FURTHER INFORMATION ON POLLUTION PREVENTION
Additional information on source reduction, reuse and
recycling approaches to pollution prevention is available
in EPA reports listed in this section, and through state pro-
grams (listed below) that offer technical and/or financial
assistance in the areas of pollution prevention and treat-
ment.
In addition, waste exchanges have been established in
some areas Of the U.S. to put waste generators in contact
with potential users of the waste. Four waste exchanges are
listed below. Finally, EPA's regional offices are listed.
EPA REPORTS ON WASTE
MINIMIZATION
U.S. Environmental Protection Agency. "Waste
Minimization AuditReport: Case Studies of Corrosive
and Heavy Metal Waste Minimization Audit at a
Specialty Steel Manufacturing Complex." Executive
Summary.*
U.S. Environmental Protection Agency. "Waste
Minimization Audit Report: Case Studies of
Minimization of Solvent Waste for Parts Cleaningand
from Electronic Capacitor Manufacturing Operation."
Executive Summary.*
U.S. Environmental Protection Agency. "Waste
Minimization Audit Report: Case Studies of
Minimization of Cyanide Wastes from Electroplating
Operations." Executive Summary.*
U.S. Environmental Protection Agency. Report to
Congress: Waste Minimization, Vols. I and II. EPA/
530-SW-86-033 and -034 (Washington, D.C.: U.S.
EPA, 1986).**
U.S. Environmental Protection Agency. Waste
Minimization - Issues and Options, Vols. I-in EPA/
530-SW-86-041 through -043. (Washington, D.C.:
U.S. EPA, 1986).**
* Executive Summary available from EPA,
WMDDRD, RREL, 26 West Martin Luther King Drive,
Cincinnati, OH, 45268; full report available from the
National Technical Information Service (NTIS), U.S.
Department of Commerce, Springfield, VA 22161.
** Available from theNationalTechnical Information
Service as a fivervolume set, NTIS No. PB-87-114-328.
WASTE REDUCTION TECHNICAL/
FINANCIAL ASSISTANCE PROGRAMS
The EPA's Office of'Solid Waste andEmergency Re-
sponse has set up a telephone call-in service to answer
questions regarding RCRA and Superfund (CERCLA):
(800) 242-9346 (outside the District of Columbia)
(202)382-3000 (in the District of Columbia)
The following states have programs that offer technical
and/or financial assistance in the areas of waste minimiza-
tion and treatment
Alabama
Hazardous Material Management and Resources Recov-
ery Program
University of Alabama
P.O. Box 6373
Tuscaloosa, AL 35487-6373
(205)348-8401
Alaska
Alaska Health Project
Waste Reduction Assistance Program
431 West Seventh Avenue, Suite 101
Anchorage, AK 99501
(907) 276-2864
Arkansas
Arkansas Industrial Development Commission
One State Capitol Mall
Little Rock, AR 72201
(501) 371-1370
California
Alternative Technology Section
Toxic Substances Control Division
California State Department of Health Service
714/744 P Street
Sacramento, CA 94234-7320
(916) 324-1807
Connecticut
Connecticut Hazardous Waste Management Service
Suite 360
900 Asylum Avenue
Hartford, CT 06105
(203) 244-2007
73
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Connecticut Department of Economic Development
210 Washington Street
Hartford, CT 06106
(203) 566-7196
Georgia
Hazardous Waste Technical Assistance Program
Georgia Institute of Technology
Georgia Technical Research Institute
Environmental Health and Safety Division
O'Keefe Building, Room 027
Atlanta, GA 30332
(404) 894-3806
Environmental Protection Division
Georgia Department of Natural Resources
Floyd Towers East, Suite 1154
205 Butler Street :
Atlanta, GA 30334
(404) 656-2833
Illinois
Hazardous Waste Research and Information Center
Illinois Department of Energy of Energy and Natural
Resources
1808 Woodfield Drive
Savoy, IL 61874
(217) 333-8940
Illinois Waste Elimination Research Center
Pritzker Department of Environmental Engineering
Alumni Building, Room 102
Illinois Institute of Technology
3200 South Federal Street
Chicago, IL 60616
(313) 567-3535
Indiana
Environmental Management and Education Program
Young Graduate House, Room 120
Purdue University
West Lafayette, IN 47907
(317) 494-5036
Indiana Department of Environmental Management
Office of Technical Assistance
P.O. Box 6015
105 South Meridian Street
Indianapolis, IN 46206-6015
(317) 232-8172
Iowa
Center for Industrial Research and Service
205 Engineering Annex
Iowa State University
Ames, IA 50011
(515) 294-3420
Iowa Department of Natural Resources
Air Quality and Solid Waste Protection Bureau
Wallace State Office Building
900 East Grand Avenue
Des Moines, IA 50319-0034
(515) 281-8690
Kansas
Bureau of Waste Management
Department of Health and Environment
Forbes Field, Building 730
Topeka,KS 66620
(913) 269-1607
Kentucky
Division of Waste Management
Natural Resources and Environmental
Protection Cabinet
ISReillyRoad
Frankfort, KY 40601
(502) 564-6716
Louisiana
Department of Environmental Quality
Office of Solid and Hazardous Waste
P.O. Box 44307
Baton Rouge, LA 70804
(504) 342-1354
Maryland
Maryland Hazardous Waste Facilities Siting Board
60 West Street, Suite 200 A
Annapolis, MD 21401
(301)974-3432
Maryland Environmental Service
2020 Industrial Drive
Annapolis, MD 21401
(301)269-3291
(800) 492-9188 (in Maryland)
Massachusetts
Office of Safe Waste Management
Department of Environmental Management
100 Cambridge Street, Room 1094
Boston, MA 02202
(617) 727-3260
Source Reduction Program
Massachusetts Department of Environmental Quality En-
gineering
1 Winter Street
Boston, MA 02108
(617) 292-5982
74
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Michigan
Resource Recovery Section
Department of Natural Resources
P.O. Box 30028
Lansing, MI 48909
(517) 373-0540 '
Minnesota
Minnesota Pollution Control Agency
Solid and Hazardous Waste Division
520 Lafayette Road
St. Paul, MN 55155
(612)296-6300
Minnesota Technical Assistance Program
W-140 Boynton Health Service
University of Minnesota
Minneapolis, MN 55455
(612) 625-9677
(800) 247-0015 (in Minnesota)
Minnesota Waste Management Board
123 Thorson Center
7323 Fifty-Eighth Avenue North
Crystal, MN 55428
(612) 536-0816
Missouri
State Environmental Improvement and Energy
Resources Agency
P.O. Box 744
Jefferson City, MO 65102
(314) 751-4919
New Jersey
New Jersey Hazardous Waste Facilities Siting
Commission
Room 614
28 West State Street
Trenton, NJ 08608
(609) 292-1459
(609) 292-1026
Hazardous Waste Advisement Program
Bureau of Regulation and Classification
New Jersey Department of Environmental
Protection
401 East State Street
Trenton, NJ 08625
Risk Reduction Unit
Office of Science and Research
New Jersey Department of Environmental Protection
401 East State Street
Trenton, NJ 08625
New York
New York State Environmental Facilities
Corporation
50 Wolf Road
Albany, NY 12205
(518)457-3273
North Carolina
Pollution Prevention Pays Program
Department of Natural Resources and
Community Development
P.O. Box 27687
512 North Salisbury Street
Raleigh, NC 27611
(919)733-7015 ;
Governor's Waste Management Board
325 North Salisbury Street
Raleigh, NC 27611
(919)733-9020
Technical Assistance Unit
Solid and Hazardous Waste Management Branch
North Carolina Department of Human Resources
P.O.Box2091
306 North Wilmington Street
Releigh.NC 27602
(919) 733-2178
Ohio
Division of Solid and Hazardous Waste Management
Ohio Environmental Protection Agency
P.O. Box 1049
1800 WaterMark Drive
Columbus, OH 43266-1049
(614) 481-7200
Ohio Technology Transfer Organization
Suite 200
65 East State Street
Columbus, OH 43266-0330
(614) 466-4286
Oklahoma
Industrial Waste Elimination Program .
Oklahoma State Department of Health
P.O. Box 53551
Oklahoma City, OK 73152
(405) 271-7353
Oregon
Oregon Hazardous Waste Reduction Program
Department of Environmental Quality
811 Southwest Sixth Avenue
Portland, OR 97204
(503) 229-5913
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Pennsylvania
Pennsylvania Technical Assistance Program
501F. Orvis Keller Building
University Park, PA 16802
(814) 865-0427
Center of Hazardous Material Research
320 William Pitt Way
Pittsburgh, PA 15238
(412) 826-5320
Bureau of Waste Management
Pennsylvania Department of
Environmental Resources
P.O. Box 2063
Fulton Building
3rd and Locust Streets
Harrisburg, PA 17120
(717) 787-6239
Rhode Island
Ocean State Cleanup and Recycling Program
Rhode Island Department of Environmental Management
9 Hayes Street
Providence, RI02908-5003
(401) 277-3434
(800) 253-2674 (in Rhode Island)
Center for Environmental Studies
Brown University
P.O. Box 1943
135 Angell Street
Providence, RI 02912
(401) 863-3449
Tennessee
Center for Industrial Services
102 Alumni Hall
University of Tennessee
Knoxville,TN 37996
(615) 974-2456
Virginia
Office of Policy and Planning
Virginia Department of Waste Management
llth Floor, Monroe Building
101 North 14th Street
Richmond, VA 23219
(804) 225-2667
Washington
Hazardous Waste Section
Mail Stop PV-11
Washington Department of Ecology
Olympia, WA 98504-8711
(206) 459-6322
Wisconsin
Bureau of Solid Waste Management
Wisconsin Department of Natural Resources
P.O. Box 7921
101 South Webster Street
Madison, WI53707
(608)267-3763
Wyoming
Solid Waste Management Program
Wyoming Department of Environmental Quality
Herchler Building, 4th Floor, West Wing
122 West 25th Street
Cheyenne, WY 82002
(307) 777-7752
WASTE EXCHANGES
Northeast Industrial Exchange
,90 Presidential Plaza, Syracuse, NY 13202
(315)422-6572
Southern Waste Information Exchange
P.O. Box 6487, Tallahassee, FL 32313
(904) 644-5516
California Waste Exchange
Department of Health Services
Toxic Substances Control Division
Alternative Technology & Policy Development Section
714 P Street
Sacramento, CA 95814
(916) 324-1807
U.S. EPA REGIONAL OFFICES
Region 1 (VT, NH, ME, MA, CT, RI)
John F. Kennedy Federal Building
Boston, MA 02203
(617) 565-3715
Region 2 (NY, NJ)
26 Federal Plaza
New York, NY 10278
(212)264-2525 .
Region 3 (PA, DE, MD, WV, VA)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-9800
Region 4 (KY, TN, NC, SC, GA, FL, AL, MS)
345 Courtland Street, NE
Atlanta, GA 30365
(404) 347-4727
76
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Region 5 (WI, MN, MI, IL, IN, OH)
230 South Dearborn Street
Chicago, EL 60604
(312)353-2000
Region 6 (NM, OK, AR, LA, TX)
1445 Ross Avenue
Dallas, TX 75202
(214) 655-6444
Region 7 (NE, KS, MO, IA)
756 Minnesota Avenue
Kansas City, KS 66101
(913) 236-2800
Region 8 (MT, ND, SD, WY, UT, CO)
999 18th Street
Denver, CO 80202-2405
(303) 293-1603
Region 9 (CA, NV, AZ, ffl)
215 Fremont Street
San Francisco, CA 94105
(415) 974-8071
Region 10 (AK, WA, OR, ID)
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-5810
77
iir U.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-001/80347
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