We got in a batch of boards with a bad soldermask.  When we were
compareing the bad boards to a known good board from a previous run
the most obvious difference was that the bad boards had a matt mask
where the known good boards had a glossy mask.  The obvious cause was
some kind of contamination.  The upshot is that it has been legislated
now that all future boards will LPI glossy.  Internal politics aside,
what kind of specification, if any, do you guys put on your documentation
to specify soldermask?

Do you use a note on the drawing, a material callout table, an entry
in your PCB spec, or what?

How specific are you?

Is there any real performance difference between matt and glossy LPI?

What do you fab and/or assembly shops prefer -- why?

In the past we have allowed the board shop to do their thing and only
specified LPI and standard thickness etc...  These were primarily SMT
with only passives (ie. caps, resistors, diodes) on the backside.

Thanks,
[log in to unmask]
Don Walker

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