*I pretty much agree with Bev's comments on the preceding material.

I recently spoke with a Melbourne based R&D lab who were investigating
intermittant failures of circuit boards. They discovered that the populated
boards were arriving with 20 to 30 micrograms of NaCl equivalent per sq
inch from the manufacturer but could not relate the failures to the ionic
contamination.
[Bev Christian] Doug?

[Doug]:  It's possible.  Since the measure is micrograms of NaCl
equivalent, then it was obtained using a ROSE test, which is a single
measure of ionic contamination.  I have seen cases in the past where a
value of 20-30 had no reliability failures.  This could be because the
circuits are not very demanding, or were very robust in design, or, as is
more often the case, you were getting some form of product from the solder
mask, such as a carbonate.  Dry film solder masks were notorious for
putting out high values by that test when not fully cured.  As such, they
gave out high ROSE values, but the more detrimental species, such as
chloride, may not have been present in detrimental amounts.

What I need is some further documented experience on the reliability of
circuit boards (Like the publication above) to support or discount my "do
nothing" case.

*I would look at the assemblies.  If there is no particulate residue from
the small fire or no other residue, then you are probably safe.  My only
thought would be if the cooling systems for the equipment may have drawn
combustion products down to the board level.  If you can't see anything, I
wouldn't worry about it.

By the way, CSL is located in Kokomo, Indiana.  765-457-8095

Doug Pauls
Rockwell
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