FOR
THE
PRINTED WIRING BOARD CASE STUDY 1
A Cooperative Project
between the
U.S. Environmental
Protection Agency
and PWB
Manufacturers
Nationwide
PRINTED WIRING BOARD
CASE STUDY 1
Pollution
Prevention
Work Practices
The Design for the Environment (DfE)
Printed Wiring Board Project is a vol-
untary, cooperative effort between the
printed wiring board (PWB) industry, the
U.S. Environmental Protection Agency (EPA),
and other stakeholders dedicated to helping
PWB manufacturers find cost-effective ways
to incorporate environmental concerns into
business decisions. To help PWB manufac-
turers improve environmental performance,
the DfE project is developing a series of case
studies highlighting industry-specific pollu-
tion prevention information.
Successful pollution prevention focuses
on reducing or eliminating pollution at the
source through changes in materials,
processes, practices, or products. Source
reduction is at the top of the pollution pre-
vention hierarchy, and is preferred by EPA
over closed-loop recycling, treatment, and
disposal. As specified in the Pollution Pre-
vention Act, EPA prefers that companies
investigate recycling and treatment only after
every attempt has been made to implement
source reduction options.
Implementing viable pollution preven-
tion alternatives can result in economic as well
as environmental benefits for your manufac-
turing operation. This case study, the first of a
series, focuses on improved work practices
and minor process changes that PWB manu-
facturers have found reduced their chemical
and water use, lowered workplace chemical
exposures, or reduced waste generation and
resulting disposal and compliance costs. These
changes have reduced the environmental
impact of the facilities' manufacturing process-
es and have cut costs at the same time. For
example, after implementing some simple
water conservation measures, one PWB manu-
facturing plant with a throughput of 1,000
boards per week was able to save over
850,000 gallons of water per year. The $250
implementation cost of purchasing and
installing the flow reducers used to achieve
these savings led to an extremely short pay-
back period of only two months.
As you think about the production
processes and work practices in your plant,
this case study may give you some new ideas
for preventing pollution in your facility. There
are many more techniques that PWB manufac-
turers have used to prevent pollution than
space available in this publication allows. In
addition, many manufacturers have invested
Pollution Prevention Hierarchy
July 1995
-------
Pollution
Prevention
Work Practices
The Design for the Environment (DfE)
Printed Wiring Board Project is a vol-
untary, cooperative effort between the
printed wiring board (PWB) industry, the
U S Environmental Protection Agency (EPA),
and other stakeholders dedicated to helping
PWB manufacturers find cost-effective ways
to incorporate environmental concerns into
business decisions. To help PWB manufac-
turers improve environmental performance,
the DfE project is developing a series of case
studies highlighting industry-specific pollu-
tion prevention information.
Successful pollution prevention focuses
on reducing or eliminating pollution at the
source through changes in materials,
processes, practices, or products. Source
reduction is at the top of the pollution pre-
vention hierarchy, and is preferred by EPA
over closed-loop recycling, treatment, and
disposal. As specified in the Pollution Pre-
vention Act, EPA prefers that companies
investigate recycling and treatment only after
every attempt has been made to implement
source reduction options.
and have cut costs at the same time. For
example, after implementing some simple
"uer conservation measures, one PWB manu-
facturing plant with a throughput of 1,000
boards per week was able to save over
850 000 gallons of water per year. The ^U
implementation cost of purchasing and
installing the flow reducers used to achieve
these savings led to an extremely short pay-
back period of only two months.
As you think about the production
processes and work practices in your plant,
this case study may give you some new ideas
for preventing pollution in your facility. There
are many more techniques that PWB manufac-
turers have used to prevent pollution than
space available in this publication allows. In
addition, many manufacturers have invested
Pollution Prevention Hierarchy
July 1995
-------
in more capital intensive changes, such as on-site etchant
regeneration (the focus of Case Study #2) or an ion
exchange/electrowinning system for metals recovery from
wastewater, which can significantly reduce waste generation.
Getting Started
The most successful pollution prevention programs are
developed as an integral part of a facility's decision-making
process, where the opportunities to prevent pollution are
considered with each decision to install new equipment, to
make process changes, or to purchase new chemicals.
The Benefits of Preventing Pollution Include
Reductions in:
• Raw materials use, exposures, and costs
• Waste generation and disposal costs
• Regulatory compliance costs
• Treatment costs
• Transportation risks and costs
In planning a pollution prevention program, it is essen-
tial to first obtain the full support of management and to
define the goals of the program. Next, examine each step of
your manufacturing process and identify the raw materials
used, wastes generated, potential occupational exposures,
and environmental releases. This assessment will allow you to
take a comprehensive look at your process and to prioritize
and select areas where pollution prevention and cost savings
are most feasible and most easily accomplished.
Once the most promising opportunities have been
implemented, evaluations of the project engineering, equip-
ment design, and performance should be conducted.
The process does not end after implementation of the
selected opportunity. Pollution prevention is an efficient
way of doing business because there is continuous evalua-
tion of pollution prevention opportunities in working
toward the goal of eliminating risk to workers and the envi-
ronment, while maintaining or improving product quality
and process efficiency.
Preventing Pollution
While the materials used, releases, exposures, and
wastes generated will vary from one facility to another, the
pollution prevention ideas presented in this case study have
been successfully implemented under a variety of operating
conditions. This case study concentrates on relatively simple
changes that PWB manufacturers have found to be helpful in
reducing chemical losses, increasing bath life, conserving
water, reducing sludge volume, or recovering materials that
otherwise would have been disposed.
By reducing dragout between the process baths and
the rinsewater, both the amount of chemical removed from
the bath and the amount of chemical added to the rinsewa-
ter can be reduced. The following options will help to
reduce dragout:
• Withdraw racks at a slower rate: lengthen dragout time to
allow more chemical to drip back to the process tank.
• Tilt racks at an angle to allow dragout chemicals to collect
and drain back into the tank.
• Install drainboards between process and rinse tanks.
Drainboards will minimize spillage between tanks. By
sloping the drainboards away from rinse tanks, dragout
chemicals drain back into the process tank.
WORK
PIECE
PROCESS
TANK
Using a cam, add a slight bump at the end of the rack
withdrawal stroke to shake excess chemical back into
the bath.
Install an under-rack tray that travels with the rack from
one tank to the next and empties dragout back into
the tank.
In addition to reducing dragout, process bath chemi-
cals and replenisher can be conserved by maximizing the
useful life of process baths. Sludge generated from treatment
of spent baths will also be reduced with the lengthening of
bath life.
• Useful bath life can be maximized by understanding the
bath conditions through monitoring. With some process-
es such as electroless lines, cupric chloride etching, and
ammoniacal etching, continuous monitoring (pH, con-
ductivity, specific gravity, colorimetric, or on-line titra-
tion) allows the operator to maintain consistent,
optimum conditions. Other types of baths (e.g., copper
plating and tin-lead plating) can be maintained through
periodic monitoring.
July 1995
-------
• Facilities that currently send bath samples off-site for test-
ing may find it cost-effective to test the bath chemistry
on-site. This allows for improved control of process baths
through shorter turnaround times between the bath mea-
surement and the bath adjustment. The capital required
for equipment and personnel may be justified through the
savings associated with improved process control and
reduced fees for laboratory testing.
• Baths that require dumping due to particle build-up, such
as the resist build-up in the stripper for photoresist, can
be filtered to increase the bath life.
• Use rinse water as make-up to top off the bath.
• Using a ''drain and fill" system as an alternative to a "feed
and bleed" system for process bath replenishment can
reduce chemical use while still allowing for in-process
replenishment. The drain and fill system automatically
removes a measured volume of the spent process solution
(draining) by lowering the level slightly in the process tank
and then replacing (filling) the removed solution with
fresh chemical without interrupting production. Unlike a
feed and bleed system where a portion of the fresh solu-
tion is bled with the spent solution, the drain and fill sys-
tem does not waste fresh solution. This technology can be
applied to the feed and bleed process in photoresist devel-
oping and photoresist stripping operations, electroless cop-
per bath growth, and ammoniacal etchant replenishment,
as well as to rinse tanks where water use can be reduced.
Oft
By taking steps to prevent copper build-up on your
plating racks, you can reduce the amount of stripping solu-
tion needed, thereby reducing the amount of plating sludge
generated.
One facility converted to polyethylene racks on their elec-
trolytic plating lines and reduced the amount of strip-
ping solution needed (and spent stripper) by 75%.
• Plating rack design and material choice can reduce cop-
per build-up. Using polyethylene-coated plating racks in
the electrolytic copper plating lines can significantly
reduce copper build-up.
• Some facilities have found they can easily scrape the cop-
per build-up from racks with a knife instead of chemical-
ly removing it. This option may only be feasible for
smaller facilities.
• Check racks periodically for wear. Replace insulation
where it has worn out and, when necessary, rebuild and
recoat racks.
from
Process chemicals lost through evaporation contribute
to your environmental releases and increase your raw materi-
al costs.
• Verify that your ventilation and air circulation system is
engineered to achieve an optimal balance between
increasing ventilation to reduce employee exposure and
decreasing ventilation to reduce chemical losses and
releases to the environment through evaporation.
• Float polypropylene balls on plating baths to reduce
evaporation from process tanks. The success of this
technique depends on the type of bath and the tank
configuration.
Improvements in your rinsing efficiency can reduce the
amount of water required for rinsing while reducing the
amount of wastewater sent to treatment.
• Install flow controls. For example, use spray rinsing in the
first rinse tank or use flow restrictors to reduce the quanti-
ty of water used. Additionally, installing contact switches
automatically turns off the fresh water supply when the
rinse is not in use.
• Use a countercurrent rinse configuration.
• Use an evaporator to concentrate the wastewater from the
first tank after the copper plating tank and return the cop-
per to the plating tank as a make-up.
• Install a rinse tank controller to measure conductivity
dynamically. As acidic rinsewater indicates contamination,
a conductivity sensor provides information on the cleanli-
ness of the rinsewater, and can be set to trigger the flow
of fresh water only when necessary.
• Install turbulence devices, such as mixers or agitators to
increase contact between the rinse water and the board.
Air agitation or workpiece agitation can also improve
rinse efficiency.
Workpiece
Movement
Work
Product
1
T
Process
Tank
Rinse
Rinse
Rinse
'
T
Effluent to recycle,
resource recovery
or treatment
Rinse
Water
Influent
July 1995
------- |