Darcy Davis wrote:

Hey Guys,

We just received an PCB order back from one of our suppliers who uses a dry
film soldermask. Unfortunately we quickly found that the soldermask is thick
enough to prevent FPGAs from sitting correctly on the lands. Is this to be
expected with dry film solder mask?

Yes, the dry film is a lot thicker. I think it runs .002 v- .004" thick. I think most
fabricators use a material by DuPont Riston, called Vacrel. So, you might poke
around and see if there is a spec on the material your fabricator used.
(It seems I've seen a much thicker dry film on some boards we got several years
ago, that must have been close to .020" thick. I don't know what that was, however.


Out of curiosity, does anybody know the
thickness of dry film and LPI?


LPI goes on much thinner, just a thousandth or so. I think the process allows
them to control the thickness when it is applied.


Jon



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