&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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