Brian Thomas (b_thomas@sigmacir.com)
Thu, 28 Mar 1996 10:27:05 PST

From: "Brian Thomas"
To: ComplianceNet@ipc.org
Date: Thu, 28 Mar 1996 10:27:05 PST
Subject: Air Emissions from Printed Circuit Manufacturing
Message-Id: <1A8AEF60E86@sigmacir.com>

From: Brian Thomas
Printed Circuit Alliance (PCA)
Sigma Circuits, Inc.
408-727-9168 x 106
408-727-8859 fax

Greetings:
Local area manufacrures in the San Jose, CA area are working on a cooperative effort with
the Bay Area Air Quality Management District (BAAQMD) developing a permitting handbook and
Chapter for the Printed Circuit Industry. We would anticipate that it will eventually be
adopted for the entire state of California. We are collecting information regarding emissions
from manufacturing processes. Of particular interest are VOC emissions, either calculations,
estimates or stack measurements. We also need information on other emissions including acids,
formaldehyde, and ammonia.

The most difficult area to resolve at this point are resist strippers. Current BAAQMD methodology
assumes that all of the organics will be emitted including monoethanolamine.

We plan to include estimated emission rates in the permitting handbook.

If you have any information that may be of assistance in this effort please e-mail me or
give me a call.

Regards,
Brian Thomas

Brian and Everyone,
Some comments based on 1) my discussions w/Scott Campbell of Surface Tek Specialty Products
re: MEA stripper vapor pressure, and 2) an 8/89 PC Fab article on formaldehyde losses from
electroless plating plus our own stack samples.

MEA stripper losses - MEA vapor pressure is determined by applying Raoults law, which is
Pi(comp) = Xi*Pi(pure) (NOTE: It's tough not being able to write subscripts.) So to
interpret, the vapor pressure of a dilute component in a solution equals the MOLE fraction
of that component times the vapor pressure of the pure component at the temp. in question.
Thanks to Scott who supplied a Dow Chemical vapor pressure graph, and ran the extrapolation
below 10 mm Hg (where 100% MEA vapor pressure is at 163F), the vapor pressure at 130F
(typical temp for a stripper) would be 3.9 mm Hg. Applying Raoults law to a 5% (by wt)
solution of MEA (1.5% molar) would yield an MEA concentration of 0.003% in air. So if you
know your air flow from your stripper, multiplying this by the weight of air and 0.003%
would yield the MEA emissions. This would be a conservative estimate, as it assumes that
the air flow is saturated with MEA for this operating condition.

Formaldehyde (CH2O) losses - The 8/89 PC Fab article by Dr. Francesco Tomaiuolo, Alfachimici
in Moncalieri, Italy measured the CH2O concentration in an electroless bath based on 1) a new
bath, 2) a steady bath, and 3) an old bath. What was determined was that the CH2O loss
was driven primarily by the reaction converting CH2O to sodium formiate and sodium chloride.
with CH2O loss to formiate formation at the 2:1 molar ratio rate. Article concludes that
"... in the global balance consumption, the formaldehyde evaporation is of secondary importance. " Further, "... the solubility of CH2O in an aqueous solution of electroless copper is extremely high. Therefore, it is rather difficult to strip it with air bubbling."

HADCO's stack sampling results confirm this report. In 1991 results from our large facility were
0.024 and 0.082ppm; and from our quick turn facility 0.008 and 0.001ppm using OSHA method 52 and
NIOSH method 3500 respectively. Analysis of the higher concentrations using EPA's stack dispersion
modelling confirmed compliance with NH's air toxic ambient air limits (AALs) at the property lines.
Our consultant concluded that there's more CH2O coming from the exhausts from autos travelling I93
than from our stacks.

Finally, this data was accepted by the Monterey Bay Unified Air Polution Control District (MBUAPCD).
Although each district has separate rules, I would think that acceptable scientific data for one
district would be acceptable to another. (P.S. On this account, Scott Campbell advises that he
addressed the MEA issue in the Bay Area about one year ago!)

Finally, ammonia - This is quite variable based on what etchant you use, and how you run your
etcher. Quantitative sample tubes will give you a +/- 25% of tube scale concentration for
calculating emissions estimates. But since NH3 is very soluble in water, and its odor threshold
is below the TLV, or STEL, scrubbing it is fairly inexpensive. My question is why don't board
shops scrub this with muriati?