Steve,
I had related problems with several types of dryfilm soldermasks when I
used SSA back in the 1990's, which is a precursor to XJN. The solvent,
IMHO, is active enough to attack the acrylic portion of the dryfilm mask
under the correct conditions, time, temp, spray pressure, proper cure of
soldermask, proper board prep, etc... This was also true when we used 1,1,1
trich, and should also be true of n-propyl bromide. I've cleaned off more
acrylic conformal coated boards in my time than I care to admit. Acrylic is
weak stuff.
Repeated washing, typical in hi-rel environments, adds to the problem.
WE stopped using dryfilm soldermasks on our designs as a whole because we
could not find them superior to LPI's and could not justify the risks.
As a contract manufacturer, we stipulated the use of LPI's, regardless of
original design requirements, as part of the contract, which superceded the
drawing package. I believe you will continue to be plagued by "occasional"
failures of this type. If you upgrade from your batch machine to an inline,
you will see a increase in the failure rate.
Last, let me say that the purpose of the soldermask was to act as a
manufacturing aid. Therefore, selection of the soldermask should be left to
the manufacturer, and should be selected for performance in the factory.
Therefore, you should specify the soldermask to the design\customer and
stop the madness.
Good Luck
Steve Mikell
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