&EPA
                                United States
                                Environmental Protection
                                Agency	
                                 Risk Reduction
                                 Engineering Laboratory
                                 Cincinnati, OH 45268
                                Research and Development
                                 EPA/600/M-91/045 Oct. 1991
ENVIRONMENTAL
RESEARCH  BRIEF
                       Waste Minimization Assessment for a
                Manufacturer of Prototype Printed Circuit Boards

                             F. William Kirsch andGwen P. Looby*
 Abstract
 The U.S. Environmental Protection Agency (EPA) has funded
 a pilot project to assist small- and medium-size manufacturers
 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 Minimiza-
 tion Opportunity Assessment Manual (EP A/625/7-88/003 July
 1988). The WMAC team at Colorado State University per-
 formed an assessment at a plant manufacturing prototype
 printed circuit boards. Various processes are involved including
 photographic operations, drilling, scrubbing, laminating, etch-
 ing, and plating. The majority of the waste generated by this
 plant comes from the plating process. The team's report,
 detailing findings and recommendations, indicated that the
 greatest waste reduction and cost savings would result from
 recovering copper, tin, and lead from the plating wastewater.

 This Research Brief was developed by the principal investiga-
 tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
 nati, OH, to announce key findings of  an ongoing research
 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 manufacturers

'University City Science Center, Philadelphia, PA 19104.
               and an additional stress on the environment. One solution 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 manufacturers
               who want to minimize their formation of hazardous waste but
               lack the inhouse expertise to do so. Under agreement with
               EPA's Risk Reduction Engineering Laboratory, the Science
               Center has established three WMACs. This assessment was
               done by engineering faculty and students at Colorado State
               University's (Fort Collins) WMAC. The assessmentteams 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 forthe assessment, each client must fall within
               Standard Industrial Classification Code 20-39, have  gross
               annual sales not exceeding $50 million, employ no more than
               500 persons, and lack inhouse expertise in waste minimization.

               The potential benefits of the pilot project include minimization
               of the amount of waste generated by manufacturers, reduced
               waste treatment and disposal costs for participating plants
               valuable experience for graduate and undergraduate students
               who participate in the program, and a cleaner environment
               without more regulations and higher costs for manufacturers.

                                    ^£/y Printed on Recycled Paper

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Methodology of Assessments
The waste minimization assessments require several s'rte visits
to each client served. In general, the WMACs follow the
procedures outlined in the EPA Waste Minimization Opportu-
nityAssessment Manual(EPA/625/7-88/003, July 1988). The
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.
Finally, a confidential report that details the WMAC's findings
and recommendations (including cost savings, implementation
costs, and payback times) is prepared for each client.

Plant  Background
This plant manufactures prototype single-sided, double-sided,
and multi-layer printed circuit boards, the plant operates 3,500
hr annually to produce approximately  175,000 boards/yr.

Manufacturing Process
Preproduction Activities
The manufacture of circuit boards begins with preproduction
activities such as engineering, photographic operations, and
programming. Circuit information-is usually received from the
customer in the form of diagrams, films, computer-generated
artwork, and computerized drill programs. A template for the
circuit design (known as the working film) is generated photo-
graphfcalJy by the  plant from the circuit information supplied.
Sheets of copper foil/epoxy/copper foil laminate are cut to size
as blank boards. The boards are drilled, scrubbed, and rinsed
in preparation for circuit  creation. Excess epoxy is removed
from the drilled holes by a plasma desmear machine or with
concentrated sulfurte acid.

Inner  Layers
The circuit pattern used in creating the individual inner layers of
multi-layer arrays is generated with positive-image photoresist.
In order to transfer the electrical circuit design to the board, a
U V-sens'rtive dry-film photoresist is first laminated to the board.
An image of the circuit design is generated on the board by
placing a template of the circuit over the film, exposing the film
to UV light, and then developing the  photoresist. Unexposed
photoresist is removed and the exposed photoresist is polymer-
ized and remains in order to protect the copper circuitry.

A sutfurfc acid-based etchant  is then  used to remove  the
unwanted, unprotected copper. The remaining protective film is
removed to reveal the copper circuitry that is then oxidized and
cleaned.  The oxidation  process permits effective interlayer
bonding between panels in multi-layer arrays. A heated hydrau-
lic press is used to form multi-layer arrays from the individual
boards.

Outer Layers
 Circuit patterns on the outer surfaces of multi-layer arrays and
double-sided boards  are generated using a similar process.
 First the board surfaces are copper-plated using an electroless
 plating process. Negative-image dry-film photoresist  is then
 applied in order to define the circuit pattern. Additional copper
 is then electrolytteally plated on the circuit patterns to provide a
 sturdy substrate for mounting components and connectors.
The boards are cleaned and then the circuitry is plated with a
tin-lead solder to protect it during the removal of unwanted
copper and resist film.

Further processing includes the conditioning of soldered sur-
faces, cleaning, rinsing, and inspection. The legend is then
applied using silk-screening and the boards are routed, rinsed,
electrically tested, inspected, packed, and shipped

Waste Generation
Relatively clean rinses and other wastewater with contaminant
levels below the publicly owned treatment works (POTW) limits
are discharged directly to the sewer as industrial wastewater.
Rinse streams and spent reagent solutions with contaminant
levels above the POTW limits are treated onsite in a MEMTEK*
uftraf ittration system. Dried sludgef rom the MEMTEK is shipped
to a copper smelter for final  disposal.

Copper sulfate crystals precipitated from the spent copper
etching solution and waste  etchant are shipped to an  offsite
recycler for copper recovery.

Silver from waste photographic fixer is recovered onsite. Cop-
per/epoxy/aluminum dust generated by drilling and debarring
operations is disposed of as conventional waste. Aluminum
and copper foil scraps are  collected and shipped offsite for
recycling.

Table 1 shows the waste streams generated by this plant, the
waste management methods used, and the quantities  and
costs of wastes disposed.

Existing Waste Management Practices
This plant has taken the following steps to manage and mini-
mize its wastes:

   •  Deionized water is used for  makeup  thereby reducing
     sludge formation.
   •  Rinses in the plating process are used only as required.
     Time-controllers, spray-rinses, and counted low rinses are
     also used to minimize water consumption.
   •  Mechanical scrubbers are used instead of solvent-based
     cleaning and solvent-based drying is replaced by  hot-air
     dryers.
   •  The  use  of dry film plating resist replaces  the  use of
     chlorinated solvents in conjunction with silkscreening op-
     erations.
   •  Water from overflow  rinses enters the tanks from the
     bottom and drains from the top of the  tanks thereby
     improving mixing and reducing water usage.
   • Scrap aluminum is collected and sold to a recycler.
   • Silver is recovered onsite from a waste photographic fixer.
   . Copper-containing sludge is shipped to a smelter for metal
     recovery.
   • Copper sulfate crystals are shipped offsite for metal recov-
     ery.
 Mention of trade names or commercial products does not constitute
 endorsement or recommendation for use.

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Waste Minimization Opportunities
Table 2 presents brief descriptions of the waste minimization
opportunities (WMOs) recommended forthe plant by the WMAC.
The quantities of hazardous waste currently generated by the
plant and possible waste reduction depend on the production
level  of the plant. All values should be considered in that
context.

ft should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with hazardous waste treatment and disposal.  Other
savings not quantifiable by this study include a wide variety of
possible future costs related to changing emissions standards,
liability, and employee health. It should also be noted that the
savings given for each opportunity reflect the savings achiev-
able when implementing each waste minimization opportunity
independently and do not reflect duplication of savings that
would result when opportunities are implemented in a package.
                                Additional Recommendations
                                The WMAC team also investigated several other opportunities
                                for waste minimization that required lengthy paybacks or were
                                considered to be beyond the scope of this program. Those
                                measures are:
                                  • Reduce sludge volume through precipitant substitution.
                                  • Reuse the MEMTEK effluent that is discharged to the
                                   sewer.
                                  • Increase drainage times over plating baths.
                                  • Install a sludge dryer.
                                  • Recover and recycle the  copper from  the copper/epoxy
                                   scrap.

                                This Research Brief summarizes a part of the work done under
                                Cooperative Agreement No. CR-814903 by the University City
                                Science Center underthe sponsorship of the U.S. Environmen-
                                tal Protection Agency. The EPA Project Officer was Emma Lou
                                George.
Table 1. Summary of Current Waste Generation
Waste Generated
Waste Management Method
Annual Quantity
  Generated
  Annual Waste
Management Cost
Plating Operations
   Treated rinse water
   Untreated rinse water
   Copper etchant
   Plating sludge
   Copper sulfate crystals
Other Operations
   Cooling water
   Waste photo fixer
   Copper/epoxy scrap
Treated in MEMTEK and sewered
Sewered
Offsite metal recovery and disposal
Shipped to smelter
Offsite metal recovery


Sewered
Silver recovered onsite
Offsite landfill
  398,700 gal
 1,200,200 gal
      330 gal
    21,97516
     9,985 Ib


  113,750 gal
       35 gal
    13,000 Ib
     $24,630'
       1,880'
         690
       4,900
         890


         180'
           0
           0
'Includes raw material costs.
Table 2. Summary of Recommended Waste Minimization Opportunities
Present Practice
                                       Proposed Action
                                                  Waste Reduction and Associated Savings
The current waste management method
for plating wastewater and reagent bath
dumps involves precipitation and ultra-
filtration using a MEMTEK system. This
method results in a considerable amount
of plating sludge that is shipped to a
smelter for copper recovery.

Overflow rinse water rates exceed the
flow rates required for certain processes.
Cooling water from the heated press is
sewered after use.
         Install at ion exchange/electrowinning
         system to recover copper, tin, and lead
         from the plating wastewater. The recovered
         metals can be sold to a recycler and the
         treated rinse water can be discharged to the
         sewer as industrial wastewater.
         Reduce water usage by installing timers,
         flow reducers, and flow meters.
         Reuse the cooling water as rinse water
         in the plating line.
           Waste reduction = 21,975 Ib/yr
           Additional waste generated = 1,830 gal/yr
           Waste management cost savings=$22,070/yr
           Implementation cost = $60,520
           Simple payback = 2.7 yr
           Waste reduction = 293,000 gal/yr
           Waste management cost savings = $460/yr
           Implementation cost = $990
           Simple payback = 2.2 yr

           Waste reduction = 113,750 gal/yr
           Waste management cost savings = $180/yr
           Implementation cost  = $400
           Simple payback = 2.2 yr
                                                                        •ttV.S. GOVERNMENT PRINTING OFFICE: 1991 - S4S-018/40075

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United States
Environmental Protection
Agency
Center for Environmental Researqh
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/M-91/045

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