If there is a noticeable change in the appearance of the solder mask after
wave soldering, this is a sure sign that something is wrong! Possibilities
are:

1. The solder mask was not processed correctly in the first place. If your
copper circuitry boards are hot air solder leveled, that usually indicates
that the mask was processed okay, or nearly so (incorrectly processed masks
will "blow apart" during the hot air leveling process).

2. If the mask is processed correctly, then the problem can lie in the
assembly process itself. Possibilities would include:
   A. Excessive solder temp or excessive dwell time
   B. Excessive preheat
   C. Aggressive flux or incompatible flux
   D. Excessive exposure to the post clean process (especially alkaline
cleaners)

Under correct solder mask processing and correct assembly, there are any
number of solder masks (LPI and dry films) that should work just fine.

Regards,

Larry Fisher
Dexter Electronic Materials
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