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Printed Circuit Board Manufacture P2
The operation you describe has tremendous pollution prevention
opportunities. Many resources are available; I have listed some good
ones at the end of this message.
Depending on the size of the operation, it may be cost effective for the
company to move to a zero-discharge or near-zero discharge (which is
usually more cost-effective) system. While the economics may be better
for a larger operation to go this route, I have seen several smaller
companies using zero discharge systems simply to avoid the hassles of
operating a treatment system and having a discharge permit. Larger
companies tend to have more inertia and are more likely to stick with
treatment if they already have it; however, since this company doesn't
yet have treatment, it might be more open than most to exploring zero
discharge operation as an alternative to a treatment system.
Whether or not a treatment system is installed, simple pollution
prevention techniques in the process will reduce both the amount of
copper to be managed and the amount of wastewater requiring treatment.
Reducing wastewater volume means that the company can buy a smaller
treatment system (if it goes that route), which can mean a big cost
savings. While I was with the city of Palo Alto, we worked with
consultant Tom Barron to develop a list of p2/best management measures
for metal finishing & printed circuit board manufacturing that we
required of essentially every facility in our area. That list, which
was specifically developed to reduce copper and nickel discharges,
included measures like:
--minimizing drag out (the solution carried out from a tank along with
the board--using a drag out tank where the solution is returned to the
bath, drain boards, and long drip times all do this)
--using countercurrent rinsing
--managing rinses with flow control devices
--extending bath life
--pretreating spent baths
--controlling bath makeup (primary recommendation was use of DI water)
--minimizing drag in (contamination from previous bath)
--and optimizing wastewater treatment systems
None of this is rocket science--in fact, one small Palo Alto area shop
installed these measures using materials purchased at Orchard Supply
In addition to the above measures, the company might also wish to
consider new technologies that reduce copper use. For example, one Palo
Alto area company switched to a new technology for making the holes in
the circuit board conductive("direct metallization")--that technology
eliminated the electroless copper plating process. Information on that
project is at: http://www.city.palo-alto.ca.us/cleanbay/davila.pdf
If they do go with treatment, they should be cautious about installing a
chemical precipitation system alone. While in theory such systems can
achieve very low discharge concentrations, in practice, many companies
have difficulty operating the system in a completely controlled manner,
so most companies experience significant variance in effluent
concentrations. Palo Alto's investigation of this issue found that
companies with effluent polishing sytems (such as microfiltration, san
filtration or ion exchange) typically generated a consistent effluent
stream and had significantly fewer compliance problems.
Information obtained by the City of Palo Alto is in the Industry section
of this web page:
Almost every document in that section relates to metal finishing. The
section contains about a dozen case studies, most of which include
The National Metal Finishing Resource Center is a great site, but you
have to join (and pay) to get the information you want. If the company
is a member, it will want to check it out.
EPA Sites on metal finishing are gateways to a number of resources (for
example, the EPA has done a sector manual on metal finishing):
-------- Original Message --------
Date: Wed, 22 Sep 1999 14:05:34 -0400
From: "Thomas Hersey" <HERSEYT@bflo.co.erie.ny.us>
Reply-To: "Thomas Hersey" <HERSEYT@bflo.co.erie.ny.us>
A manufacturer of large circuit boards, such as those for microwave and
tower antennas needs to reduce copper concentrations in its wastewater.
The copper concentrations range from 3-10ppm per four day composites.
The manufacturer needs to reduce copper concentrations to <2ppm.
The basic operation entails a subtractive manufacturing process. First,
copper clad boards are sheared to size, drilled and the holes are
drilled and plated with an electroless copper plating method.
Substrates consist of fiberglass or teflon. Tin and copper
electroplating operations are used as well. Films for the boards which
detail customer specifications are obtained from an outside source and
are copied using an ammonium hydroxide blueprint process. An image is
cast onto the board and heat lamination applies an etch resist. Each
sheet is exposed to ultraviolet light whereby the cast image appears on
the board. Chemical etching, using sulfuric peroxide or ammonium
hydroxide, removes all copper from the board except the areas of image.
Washing and rinsing of the boards occurs at various stages of
The spent ammonium hydroxide solution from the etching process is
returned to the manufacturer for recycling.
The sulfuric peroxide solution is re-used on-site and eventually the
soluble copper is plated out and recycled.
All other wastewater created within the facility is sent to a 3800
gallon capacity pH adjustment tank; it is the only on-site treatment
conducted. pH typically runs high, around 9, pH adjustment is necessary
at times to keep the pH above 5 (permit limit). Flow through the
treatment system is around 12,000 gal/day.
The manufacturer has been approached by a variety vendors with expensive
treatment equiptment and is unsure of the best technology to invest
in. They request information regarding any proven treatment or
prevention technologies and other strategies to meet the new discharge
limits (< 2ppm).