United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/M-91/022 July 1991
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Printed Circuit Boards
F. William Kirsch and Gwen P. Looby*
Abstract
The U.S. Environmental Protection Agency (EPA) has
funded a pilot project to assist small- and medium- size manu-
facturers who want to minimize their generation of hazardous
waste but lack the expertise to do so. Waste Minimization
Assessment Centers (WMACs) were established at selected
universities and procedures were adapted from the EPA Waste
Minimization Opportunity Assessment Manual (EPA/625/7-
88/003, July 1988). The WMAC team at Colorado State
University inspected a plant producing printed circuit boards —
a plant that already had taken steps to control its hazardous
wastes. Producing a circuit board involves many major pro-
cesses and subprocesses: preparing the board; depositing
copper en the board by electroless plating; applying dry film;
electrolytically plating copper; electrolytically plating tin; etch-
ing and stripping; applying solder; and, perhaps, plating gold on
connectors. Each of these steps produces hazardous wastes,
e.g., electrolytic copper plating results in acid soap dumps,
copper and tin drag-out, and sulf uric acid. The main sources of
metallic contamination (copper [both dissolved and metallic],
tin, lead, gold) are the rinses after scrubbing, plating, and
etching. Although the greatest amount of waste can be reduced
by reusing effluent from the MEMTEK f (with some further
treatment), the greatest dollar savings can be found by chang-
ing the dry film developer. The present brand adheres strongly
to the unexposed film and requires an aggressive acid soap; a
less aggressive, nonhazardous soap could be used with a less-
adhering dry film developer.
This Research Brief was developed by the principal inves-
tigators and EPA's Risk Reduction Engineering Laboratory,
Cincinnati, OH, to announce key findings of an ongoing re-
search project that is fully documented in a separate report of
the same title available from the authors.
Introduction
The amount of hazardous waste generated by industrial
plants has become an increasingly costly problem for manufac-
turers and an additional stress on the environment. One solu-
tion to the problem of hazardous waste is to reduce or eliminate
the waste at its source.
University City Science Center (Philadelphia, PA) has
begun a pilot project to assist small- and medium- size manu-
facturers who want to minimize their formation of hazardous
waste but lack the inhouse expertise to do so. Under agree-
ment with EPA's Risk Reduction Engineering Laboratory, the
Science Center has established three WMACs. This assess-
ment was done by engineering faculty and students at Colorado
State University's (Fort Collins) WMAC. The assessment teams
have considerable direct experience with process operations in
manufacturing plants and also have the knowledge and skills
needed to minimize hazardous waste generation.
The waste minimization assessments are done for small-
and medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall within
University City Science Center, Philadelphia, PA 19104
Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
Printed on Recycled Paper
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persons, and lack mhouse expertise in waste minimization
ment without more regulations and higher costs for manufactur-
ers
Methodology Of Assessments
WMAC staff locates the sources of hazardous waste in the plant
and identifies the current disposal or treatment methods and
their associated costs. They then identify and analyze a variety
of ways to reduce or eliminate the waste. Specific measures to
achieve that goal are recommended and the essential support-
ing technological and economic information is developed. Fi-
nally, a confidential report that details the WMAC's findings and
recommendations (including cost savings, implementation costs
and payback times) is prepared for each client. '
_. A _ ,
Plant Background
This plant typically operates about 4,500 hr/yr to turn out
printed circuit boards, which are distributed regionally Like the
plants of some other small and medium-size manufacturers this
one had taken several steps on its own initiative to control
hazardous waste emissions. It presented a challenge to the
in their 8fforts to idenwy addifonai
Manufacturing Operations
The lami'nated flat sheets of nonconducting material are
A thin layer of copper is deposited by electroless platinq on
boards that are first cleaned and rinsed and then coated wrth a
catalyst for the reduction of the copper To apply the circuit
pattern, a dry film process is used — laminating a photosensitive
polymer resist, covering parts of the board with the printed circuit
design mask before exposure to ultraviolet liqht develooina with
sod'um carbonate, and eventually rinsing with' tap water
.-.
Electrolytic plating of copper occurs on the circuit design
developed in the preceding series of operations Then tin is
electronically plated on the^copper to protect the circuft deSgn
A the alkahne etchant used to strip away the plating resist.
A"y.coPPe[ not Protected by tin is also etched away by an
aiKalin® solution. Finally, an ammonium bifluoride-hydrogen
pero*lde s°'utl?n removes the tin to complete the electronic
circuitry on the board- whlch IS then water-rinsed and air-dried.
The plant had already taken these kinds of actions to
reduce hazardous waste:
Using dry film photoresist to eliminate chlorinated
solvents associated with silk screen application.
Substituting tin for lead solder after electrolytic
areas, which are the portions of the boards not coated by an
epoxy solder mask, which also functions as an insulator Then
a eutectic solder is coated on the surface not covered by the
mask. 7
To meet certain customers' specifications, connectors are
sometimes gold plated before solder mask application.
Combining an automated electroless plating
machine with countercurrent rinsing to cut down
drag-out of plating solution and to reduce the
quantity of rinse water.
Agitating these rinse tanks with compressed air to
get better rinsing in a given tank volume
. Most of the hazardous waste generated in this plant occurs
m various liquid streams. These major waste streams, together
with their treatment, disposal, and recycling costs are given in
Table 1 •
Tnnirttha*!«« *• • .
iI5 E "V*u lnformatlon Into Perspective, it is useful to keep
- .*•* covered racks tor those
excess copper and tin deposits on the racks.
• Applying mechanical deburrers, scrubbers, and
hot-air dryers to eliminate some hazardous
solvents. (The dusts from these operations are
collected and sold to a metal reclaimer )
''
The basic operation of the plant consists of a complex
series of mechanical and chemical process steps to deposit
copper selectively on flat sheets of nonconducting materials
formed from resins and fiber glass. Of course, the copper must
lines- and in the alkaline "ch and
Metallic copper is generated by mechanical cleaning op-
orations, drilling and routing operations, and cutting operations
. . ' In comes from electrolytic plating and stripping; lead from
rinsing and deburring.
D-
.? streams discharged to the sewer because they are
IL considlered hazardous are those from the dry film developer
,8 P03^'830 rinse- the gold plating rinse, and the spent resist
sirippor.
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Board Preparation
• Hydraulic shearing
• Drilling
• Debarring
Electroless Copper Plating
Hot soap cleaner
Rinses
Preetch
Miaoetch
Catalyst predip
Catalyst
Rinses
Accelerator
Rinses
Electroless copper plating
Rinse
Neutralizer
Rinse
Hot air dryer
Dry Film Application
• Photopolymer lamination
• Mask Application
• UV exposure
• Developer
• Rinse
Electrolytic Copper Plating
Acid soap
Cascade and bath rinse
Microetch
Spray and bath rinse
Sulfuric acid predip
Electrolytic copper plating
Spray Rinse
^-
Electrolytic Tin Plating
• Sulfuric acid predip
• Electrolytic tin plating
Etch & Strips
Resist stripper
Alkaline etch
Rinse
Tin stripper
Rinse
Hot air dryer
Gold Tab Plating
• Mask application
• Nickel plating
• Rinse
• Gold plating
• Rinse
Solder Application
Solder mask application
Thermocuring
Copper cleaner/rinse
Hot air leveling
Post clean
Fine scrubber
Final Processes
• Inspection
• Labeling
• Routing
• Packaging
• Storage
Figure 1. Sequence of Manufacturing Operations.
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The other rinses and dumps are directed into a large trench
with a level controller (but without a sewer connection). The
controller activates a pump to transport the liquids to a MEMTEK
ultrafiltration system (to 0.1 u.) that uses chemical reactions,
precipitation, and membrane filtration. Suspended solids in an
associated concentration tank are removed by bleeding a "slip
stream" to a settling tank, from which sludge is dewatered to
about 60% solids before it is hauled to a solid disposal site for
hazardous wastes.
As noted in Table 1, some solutions are taken out of the
plant for metal recovery and a credit.
Summary of Recommended Waste Minimization
Eight waste minimization opportunities (WMOs) recom-
mended by the WMAC team could cut the annual waste man-
agement costs at this plant from $86,850 to $42,225, about a
51% reduction. The largest waste volume is liquid (2.97 million
gal/yr), but one recommended WMO could reduce that by 62%
through recycling effluent from the MEMTEK filtration unit.
Because of the relatively low cost of water supply and sewering,
however, this large volumetric reduction will save only about
$3,840/yr at the present time.
A dry film developer is applied to the circuit boards to
remove unexposed photopolymer (under the design mask) and
reveal the circuit design. The largest cost saving for a particular
WMO ($23,550/yr) is estimated to come from substituting a
different developer. The sodium carbonate developer being
used requires a very aggressive acid soap to remove it before
copper is electrolytically deposited. When this soap is rinsed and
the rinsings go to the ultrafiltration unit (MEMTEK), the relatively
large soap molecules frequently plug the pores of the filtering
membranes in the MEMTEK. With a less adhesive developer, a
less aggressive soap solution can be applied, and then the
washings can be adjusted for pH and sent directly to the sewer.
In addition, the conditioner now used to treat the spent acid soap
and rinsings before they go to the MEMTEK can be eliminated.
The circuit board manufacturer knew of alternative developers,
such as Morton Thiokol's Dynaclean, which reportedly can be
cleaned by the MacDermid L5-B that forms a nonhazardous
waste. Product names are given to illustrate that such products
are commercially available.
All eight WMOs are summarized in Table 2, together with
their reductions in emissions and the associated savings and
costs. The savings are calculated for each WMO independently,
but it is obvious that some are related, so that the results from
implementing one can affect the results independently calcu-
lated for another.
This Research Brief summarizes a part of the work done
under Cooperative Agreement No. CR-814903 by the University
City Science Center under the sponsorship of the U.S. Environ-
mental Protection Agency. The EPA Project Off icer was Brian A
Westfall.
at:
The EPA contact, Emma L. George, and can be reached
Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Table 1. Summary of Current Waste Generation
Waste Stream
Hazardous Waste Generated
Hazardous Liquid Waste
A. Electroless copper:
Waste rinses
Catalyst predip
Accelerator
B. Electrolytic copper:
Acid soap predean
Water rinses
Copper plating predip
Tin plating predip
C. Resist strip, copper
etch, and tin strip:
Water rinses
Alkaline etch
Tin strip
Rack stripper
D. Other processes:
Deburrer #1
Deburrer #2
Scrubber
Hot air leveling
Hazardous Solid Waste
A. MEMTEK unit
Annual Quantity Annual Waste Management Costs
Generated Treatment Disposal Recycling
Copper plating and chemical drag-out 916,663 gal
Table salt/water dumps 530 gal
Copper-laden, dilute hydrochloric acid 530 gal
Acid soap dumps 10,189 gal
Soap, etch, copper and tin plating drag-out 366^665 gal
10% Sulfuric acid dumps 3,266 gal
2% Sulfuric acid dumps 3^266 gal
Etch, resist and tin strips drag-out 549,997 gal
Spent ammonium hydroxide 13,950 gal
Spent ammonium bifluoride/peroxide 1,450 gal
Spent rack stripper 1 [550 gal
Copper-laden rinse water 366,665 gal
Copper-, tin/lead-, and gold-laden rinse water 366ie65 gal
Epoxy-, Copper-, and tin/tead-laden rinse water 183,332 gal
Copper-, ferric chloride-, hydrochloric
acid-laden rinse 183,332 gal
Metal hydroxide sludge 27,700 Ib
$10,488
$4,380
$587
$246
$6,285
$352
$45.765
$12,570
$704
$5,471
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Table 1. Continued.
Waste Stream
Hazardous Waste Generated
B. Electroless copper:
Microetch
C. Drilling and routing
D. Deburrer #1
E. Shearing
F. Filters:
Electrolytic copper
Post clean
Auto tab plater
Copper sulfate crystals
Copper, aluminum, and gold dust
Metallic copper
Copper/epoxy laminate dropoffs
Nonhazardous filter cake
Tin/lead-laden filters
Gold-laden resin filter cartridges
Annual Quantity Annual Waste Management Costs
Generated Treatment Disposal Recycling
2,800 Ib
200 Ib
200 Ib
1,200lb
25 Ib
25 Ib
25 Ib
Table 2. Summary of Recommended Waste Minimization Opportunities
Present Practice
Proposed Action
Waste Reduction and
Associated Savings
All but four rinse streams (dry film developer,
post dean, gold plater, spent resist stripper)
and process bath dumps go to a common trench and
from there to the MEMTEK, in which they are
chemically reduced, precipitated, filtered, and settled.
The scrubber uses 183,300 gal/yr to rinse
particulates from circuit boards—metallic copper,
lead, tin, and epoxy. The liquid containing
particulates goes to the MEMTEK.from which
effluent goes to the sewer.
Thorough rinsing is mandatory for many operations
in this plant. Observation of the plant revealed
operators set flow rates for water excessively
high.
The particular brand of dry film developer in use
adheres so strongly to the unexposed film that an
aggressive acid soap is required for removal.
This soap presents problems in the MEMTEK and
necessitates prior treatment with conditioning
agents.
Tin is stripped away from the electrolytically
deposited copper sites that it protects. A
solution of ammonium bifluoride and hydrogen
peroxide is the stripping agent. The relatively
large quantity of washes is sent off-site for
treatment and recovery of tin.
Deionized water is used for rinsing on the
electrolytic copper and tin plating lines. Its
use should be extended to the electroless copper
plating line.
Reuse the MEMTEK effluent to reduce demand for
rinse water. To widen the range of possible uses,
some further treatment (e.g., ion exchange,
adsorption, and filtration) may be needed.
Additional storage tanks, pumps, and piping will
be required. Saving occurs in lower water demand
and sewer charges.
Filter (in a closed loop system) scrubber liquids
to remove hazardous particulates and recycle the
water for rinsing the scrubber. Dispose of filter
cartridge as solid hazardous waste.
Install flow reducers or flow meters on the water
supply to seven identified manufacturing
operations. Waste reduction and cost savings are
calculated only for reduced water usage, treatment
costs, and sewer costs.
Change to another dry film developer, use a less
aggressive soap (also nonhazardous), and
discharge the liquid to the sewer after pH
adjustment.
Concentrate the tin stripping solution to reduce
hauling and treatment costs. Partial freezing
will cost less than evaporation. The metal
reclaimer has said the concentrate is acceptable,
and there will be no increase in unit costs of
hauling and recycling. The separated solid can be
melted and sewered.
Use deionized water in five baths in the
electroless copper plating line, thereby reducing
sludge formation and extending the lifetime of the
bath. The savings will be achieved in lower cost
of treatment chemicals, as well as in lower water
and sewer costs. Use an ion-exchange regener-
ation system.
Waste reduction = 1,833,325 gal/yr
Cost reduction = $3,840/yr (net)
Implementation cost = $22,000
Simple payback = 5.7 yr
Waste reducion = 183,300 gal/yr
Cost reduction = $2,150/yr (net)
Implementation cost = $650
Simple payback = 4 mo
Waste reduction = 440,000 gal/yr
Cost reduction = $5,840/yr
Implementation cost = $360
Simple payback = less than 1 mo
Waste reduction = 13,500 gal/yr
Cost reduction = $23,550/yr
(based on conditioner use alone)
Implementation cost = $0
Simple payback = immediate
Waste reduction = 1,650 gal/yr
Cost reduction = $4,030/yr (net)
Implementation cost = $10,000
Simple payback = 2.5 yr
Waste reduction = 1,015 gal/yr
Cost reduction = $1,840/yr
Ion-exchange saving = $6,500/yr
Implementation cost = $9,800
Simple payback = 1.2 yr
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Table 2. Continued.
Present Practice Prooosed Action Wa*Ste Reduction and
rroposea Acnon Associated Savings
Implementation cost = $0
Simple payback = immediate
reagents implementation cost = $200
copper nuggets, and tin anodes will result. Simple payback = 9 mo
&U.S. GOVERMMENT PRINTING OFFICE: 1991 548 028/40028
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United States Center for Environmental Research BULK RATE
Environmental Protection Information POSTAGE & FEES PAID
Agency C.ncinnati, OH 45268 E^ PERM^ NO G 35
Official Business
Penalty for Private Use $300
EPA/600/M-91/022
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