To: Jeff Cullen,
Beverage and Diamond
Fr: Mark Ingle,
Project Officer, U.S. Environmental Protection Agency
Re: EPA Applicability
Interpretation Regarding Silk Screen Printing and the Printed
Circuit Board Manufacturing Process.
On May 20, 1996 you called requesting an applicability
interpretation regarding the cleaning of silk screens that are
used in the stenciling of printed circuit boards (PCBs). As you
reported, the boards were stenciled with an organic coating as
part of the manufacturing process, but this marking operation
did not involve any electroplating, etching, or other metal-based
operation. The following discussion presents my analysis and conclusions
showing that in some cases effluent from the silk screen process
would be regulated, while in other cases it would not.
Attachment A shows the first two pages of the
40 CFR 433, "Metal Finishing Point Source Category"
regulation. As shown in 433.10(a) and 433.10(c) PCB manufacture
at "independent" shops is covered by 40 CFR 413, "Electroplating
Pretreatment Standards" and all other PCB manufacturing operations
are covered by 40 CFR 433. Thus, all PCB manufacturing operations
are covered either by 40 CFR 413 or 40 CFR 433 and as such EPA's
1984 "Guidance Manual for Electroplating and Metal Finishing
Pretreatment Standards" is applicable as a reference material
for use in this applicability interpretation.
Attachment B shows the cover page and selected
additional pages from the "Guidance Manual for Electroplating
and Metal Finishing Pretreatment Standards." As shown on
pages 2-2 and 2-3 of this manual, all of the operations that EPA
used to define the PCB manufacturing process involve the application
or removal of metal from the non-conductive board substrate. None
of the manufacturing operations included in the discussion involve
the application of an organic coating or paint. Because the silk
screen process in question involves the application of an organic
coating, it is apparent that this process was not included in
the original operations examined as part of the PCB category and
as such would not independently invoke either the 40 CFR 413 or
40 CFR 433 regulations. Thus, a facility that cleaned these silk
screens, in support of another facility's PCB manufacturing operations,
should not be covered by the 40 CFR 413 or 40 CFR 433 regulations.
However, because PCB manufacturing is one of
the six "trigger" processes that are used to determine
if 40 CFR 433 is applicable at a facility, and "Painting"
is one of the 40 "other" industrial operations that
are covered by 40 CFR 433, a facility manufacturing PCB (using
etching, electroplating, or any of the other processes listed
in Attachment B) and silk screening the boards would be regulated
under 40 CFR 433. Because such a facility would be regulated,
then the effluent from the silk screening and the plating processes
would be subject to the 40 CFR 433 effluent limits. Thus, effluent
from silk screening operations, at a PCB manufacturing facility
that is covered by 40 CFR 433, would be subject to the categorical
The applicability interpretation for the subject
silk screen cleaning process is not easily defined because the
40 CFR 433 regulation utilizes PCB manufacture as a "trigger"
process for regulation. Thus, the effluent from the silk screen
or silk screen cleaning process may be regulated in some cases
and may not in others. The following summarizes the applicability
of the 40 CFR 413 and 40 CFR 433 regulations to silk screening
1. A facility that only conducts silk screening
(i.e., does not do any electroplating or electroless plating operations),
or cleans silk screens that are used to stencil PCBs, is not subject
to either 40 CFR 413 or 40 CFR 433 because the PCB-related processes
included in the development of these regulations all relate to
metal etching or plating and do not relate to organic coating
2. A facility that etches or plates metal on
PCBs and stencils the boards using a silk screen process would
be covered by 40 CFR 433. Effluent from all of the plating, silk
screening, and associated cleaning processes would be covered
because "PCB Manufacture" is one of the 40 CFR 433 "trigger"
processes and "Painting" is one of the 40 "other"
processes covered by the regulation.
3. Existing PCB manufacturers, already covered by 40 CFR 413, that also conduct silk screen printing, or silk screen cleaning, would be covered under the 40 CFR 413 regulatory limits. However, because 40 CFR 413 does not include "Painting" as a regulated unit operation (as is the case for 40 CFR 433), the effluent from the silk screen printing or silk screen cleaning should not be subject to the 40 CFR 413 regulatory limitations. However, such discharges would be likely to still be regulated using the combined waste stream formula discussed in 40 CFR 403.6(e).