Ken,
The answer to your question is "it depends".  Yes, I know you are all
shocked at my response.

It depends on the flux chemistry.  If you look in J-HDBK-001, in the
section on fluxes, there is information there provided by Al Schneider of
Alpha Metals that there are over 30 dicarboxylic acids which flux
manufacturers can use in low residue fluxes.  Considering the staggering
number of chemical proportions involved, there is no way that you can get
an answer.  Take your question back to your flux vendor and ask if the bake
temperatures you suggest are sufficient to fully activate the flux residues
and make them benign.  If so, how long a bake.   We had a question here as
to whether or not liquid flux used in hand soldering (which we are trying
to discourage) could be fully activated by some of our baking operations,
should the flux spread out too far from the heat of the soldering iron.
Alpha was able to answer the question for us, but only for the Alpha flux
we were using.  Keep in mind that you will get a different results for
"dried" flux and "activated flux".

Doug Pauls




                      "Bloomquist, Ken"
                      <ken.bloomquist@G        To:       [log in to unmask]
                      D-AES.COM>               cc:
                      Sent by: TechNet         Subject:  Re: [TN] Flux Contamination Testing
                      <[log in to unmask]>


                      03/21/2003 08:18
                      AM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      "Bloomquist, Ken"






Thanks for the responses, as always the TechNet comes through.

I do have a further question on this subject that wasn't really answered.
Does an elevated temperature bake, at say 80-90 degrees C in ambient
humidity, cause any chemical change in potentially trapped flux that would
change it's state to make it conductive/more conductive?

Thanks,

KennyB

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