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 0.082 ppm; and from our
     quick turn facility 0.008 and 0.001 ppm 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
     muriatic acid to make ammonium chloride for returning to the etcher
     since etch rate is a function of chloride concentration and copper
     solubility depends on forming a copper-ammonium-choride complex? This
     muriatic scrub is what some etch supplier do with spent etch after
     raising the pH in an enclosed agitated tank vented to a scrubber. The
     resulting NH4Cl solution is then used to make fresh etch.

          Hope the above info helps you w/BAAQD.            Lee Wilmot
                                                            HADCO Corp
From: Brian Thomas                                      [log in to unmask]
      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