&EPA
United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/020 September 1995
ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment for a
Printed Circuit Board Plant
Harry W. Edwards*, Michael F. Kostrzewa*,
and Gwen 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 waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at
Colorado State University performed an assessment at a plant
that manufactures printed circuit boards. Templates for the
circuit design are generated from customer-supplied circuit
information. Copper/epoxy laminates and copper foil are cut
into blank boards and layers. Circuit patterns are generated
through a series of photolithographic and plating processes.
The team's report, detailing findings and recommendations,
indicated that the onsite ion-exchange treatment of metal-
containing rinse water generates regenerant solutions that could
be further treated by electrowinning to recover metals and to
achieve significant cost savings.
This Research Brief was developed by the principal investiga-
tors and EPA's National Risk Management Research Labora-
tory, Cincinnati, OH, to announce key findings of an ongoing
research project that is fully documented in a separate report
of the same title available from University City Science Center.
* Colorado State University, Department of Mechanical Engineering
* University City Science Center, Philadelphia, PA
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the
problem of waste generation 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 generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
National Risk Management Research 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 assessment teams
have considerable direct experience with process operations in
manufacturing plants and also have the knowledge and skills
needed to minimize waste generation.
The pollution prevention opportunity 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 Standard Industrial Classification Code 20-39, have
gross annual sales not exceeding $75 million, employ no more
than 500 persons, and lack in-house expertise in pollution
prevention.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, and
reduction of waste treatment and disposal costs for participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
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Methodology of Assessments
The pollution prevention opportunity assessments require sev-
eral site visits to each client served. In general, the WMACs
follow the procedures outlined in the EPA Waste Minimization
Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).
The WMAC staff locate the sources of waste in the plant and
identify 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.
Plant Background
This plant manufactures printed circuit boards. It operates
approximately 4700 hr/yr to produce about 100,000 ft2 of prod-
uct annually.
Manufacturing Process
The plant, which functions as a job- and small-production-
shop, produces single-sided, double-sided, and multi-layer cir-
cuit boards.
Circuit information is received from customers as blueprints,
films, computer diskettes, or computer-generated artwork. Cir-
cuit information that is received as artwork is digitized and
computer-stored. The template for the circuit design, known as
the working film, is laser-generated from the customer's circuit
information. Programs that provide drilling instructions for the
computer-controlled drilling machines are generated digitally.
The raw materials for printed circuit boards include copper/
epoxy laminates and copper foil. Laminates and foil are cut
into blank boards and layers using hydraulic shears. Compo-
nent holes are then generated in the blank boards using high-
speed, numerically-controlled drilling machines. The drilled
boards are mechanically scrubbed in preparation for plating.
Circuit patterns are created on the individual layers of multi-
layer boards with dry-film, positive-image photoresist. The first
step in transferring the electrical circuit design to the individual
layers is laminating a UV-sensitive dry-film photoresist to the
layers. An image of the design is generated by placing a
template of the circuit over the film and exposing the film to UV
light. Exposed film is polymerized and protects the underlying
copper circuitry and unexposed photoresist is removed with an
aqueous developing solution and rinse. Unwanted copper is
then removed with an ammonia/hydrogen peroxide etchant.
The remaining protective film is removed with an alkaline resist
stripper leaving the desired copper circuitry. Fiberglass weave
sheets impregnated with resin are placed between each layer,
and the array is heated and bonded in a hydraulic press.
Component holes are then drilled in the multi-layer panels, and
the holes are cleaned with a sulfuric acid-based de-smear
solution. Further processing of multi-layer boards is identical
to that of single and double-sided boards.
series of photolithographic and plating processes. First, the
surfaces are copper-plated in an electroless plating process.
This process deposits copper on all exposed surfaces, includ-
ing the surfaces of drilled holes. Photoresist is then laminated
to the board surfaces. Additional copper is electrolytically
plated on the surface circuit patterns. After cleaning, the
pattern is electrolytically plated with tin/lead solder to protect
the copper circuity during subsequent steps to remove the
resist film and unwanted copper. The tin/lead layer is removed
following resist stripping and copper etching. A solder mask is
silk-screened and thermally cured to the board surfaces prior
to dipping the boards in molten tin/lead solder. The solder
layer provides the customer with a surface for mounting electri-
cal components. Additional processing involves conditioning of
the soldered surfaces, cleaning, rinsing, and inspecting the
finished circuit boards. Final processing includes silk-screen
application of a legend, routing, rinsing, electrical testing, in-
spections, packaging, and shipping.
An abbreviated process flow diagram for the production of
printed circuit boards is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and mint flowing rinses.
Pollution Prevention Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the waste management cost for each waste
stream identified are given in Table 1.
Table 2 shows the opportunities for pollution prevention that
the WMAC team recommended for the plant. The opportunity,
the type of waste, the possible waste reduction and associated
savings, and the implementation cost along with the simple
payback time are given in the table. The quantities of 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.
It should be noted that the economic savings of the opportuni-
ties, in most cases, results from reduction in raw material and
costs associated with 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 also should be noted that the
savings given for each opportunity that pollution prevention
opportunity alone and do not reflect duplication of savings that
may result when the opportunities are implemented in a pack-
age.
This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-819557 by the University City
Science Center under the sponsorship of the U. S. Environ-
mental Protection Agency. The EPA Project Officer was Emma
Lou George.
The circuit patterns for single and double-sided boards, and
the outer layers of the multi-layer boards are generated by a
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Circuit Design
Copper/Epoxy Laminates,
Copper Foil
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Laser Generation
of Working Film
Dry Film Application,
Exposure, and
Development
T
Cutting and
Drilling
Copper Etch and
Resist Stripping
Baking and
Bonding of Layers
Electroless Copper
Plating
Dry Film Application
and Development
Cleaning
Electrolytic Copper
Plating
Electrolytic Tin/Lead
Plating
Resist Strip and
Copper Etch
Solder Stripping
Solder Reflow
Silkscreening
Routing
Circuit Boards Packaged and
Shipped to Customers
Figurel. Abbreviated process flow diagram for circuit board production.
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solutions. Sell the recovered metals
A total of 309 Ib/yr of scrap metal will
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United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/020
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