Shane: We don�t dispense, but we have thought about it. Several points about peelable solder masks in a no-clean (low residue) process:
� Beware of latex peelable solder mask with a low res process without extensive testing. The problem is usually the cure reaction and what out-gasses from the mask during the curing. The good part about that is that you can do the evaluation of the solder mask, while you compare fluxes with your board finishes. � Some peelable solder masks are laced w/ammonium hydroxide and are real SIR killers. This should be a big time concern for low res people. � Natural latex, low ammonia, types were less conducive than higher ammonia content types, but still produce corrosion. The variable in the process seems to be mask thickness. The mask should be applied in as thin a layer as possible. Thick mask must trap ammonia under the mask. Baking a thick layer of the mask seems to make the problem worse, because the mask skins over, the board and protected land pattern are basked in ammonia and corrosion results. (Doesn�t sound like dispensing to me, does it?) � Check your assumption about curing processes as you move through the product evaluation. UV, humidity (light air), and heat cures could be part of your evaluation matrix. � Consider the ability of the mask to "stand-up" under solder heat cycles. Some peelables get crusty after their first cycle.
Good luck Dave F
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