Andy,

What you are describing sounds like random "thin areas". Certain LPI masks
are translucent when deposits are thin. Not being able to see it I can only
speculate. However, If there is solder where there should be solder, yet
you see what looks like exposed copper in other areas, it is unlikely that
these areas are actually "exposed copper" (unless the mask became dislodged
post HASL, but this does not sound like the case) . If these areas were
actually exposed copper prior to HASL, they would be covered with solder. I
have seen this before, and one way to determine is to cross section the
thin area. Another way would be to try to "light" the circuit with a
continuity meter (gently probing the "exposed copper area")

Compare the actual thickness of the mask to your specification. I'll bet
its thin.

Dave Pizzoferrato
QA Manager
Centerline Circuits

>Thanks for all the responses to my inquiry about problems with soldermask.
>A lot of people who responded wanted clarification on what I meant by
>"holes in the soldermask". Basically, there were small areas (less than 1"
>square") on the boards over which there appeared to be no soldermask. You
>could see the bare copper traces and rings around vias. It wasn't peeling
>or blistering, as there was no discernable edge or boundary around the bare
>area, it just sorta blended in to the surrounding mask. Hope this clears
>things up.
>
>Andy Buonviri
>

--------------------------------------------------------
"Always remember you're unique, just like everyone else."



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