Peter,
I would agree with Karen Tellefsen.  In the past 6 months or so, we have seen
four or five problem cases where the culprit was a latex peelable solder
mask.  The data that Karen provided is similar to what I have seen with SIR
data, probably even lower.  Part of the problem is the material itself
(ammonia based are worse), which often leaves behind either halides or a
conductive organic residue.  In the former, you get corrosion and metal
migration.  In the latter you get electrical leakage.  The situation is worse
for no-clean assemblers since there is no opportunity to remove the residues.
 As Karen said, no visible residue does not mean no residue.  Another fault
mechanism we have seen is that the materials can outgas during thermal
exposures, contaminating regions around the latex mask.  Often, conformal
coating will not stick to the latex mask residues.

I don't agree with your supposition that thousands of companies are using it
with no problems.  Lots of companies have intermittent problems they can't
explain or believe their local rep "there's absolutely no problems with my
product, buy 10 cases".  This is becoming a much bigger issue as more
companies move out of the cleaning realm (or couldn't make no-clean work) and
into no-clean technology.  

I may have a rather jaded view, but those four or five cases I mentioned
earlier - all had been told that no visible residue means no residues and
everything is AOK with the product.  Must be something in your assembly
process Bucko.

Doug Pauls
CSL

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