This is a weird one...

We've got some boards here that we build for a DOD customer. This board has
some LCCC's on it (small ones, 32-28-pins). We've been building them and
masking off certain test via's that are un-masked that wind-up beneath the
LCCC's because of the concerns (justifably) of cleaning. Now they want to
expand the test coverage that they've had, and want to un-mask all the vias!

I know from reading posts from Werner and others that if you have un-masked
vias, that you need full-fill after wave for reliabilty concerns. I also know
that cleaning flux residues from vias beneath an LCCC is a lost cause.

I have heard that the fab vendors can fill vias for you...that to me would
alleviate the concerns about cleaning. Vias that are filled already would not
allow flux to get beneath the part.

My question is; is that very expensive to get done? Getting the via's filled
at the fab vendor? I've never asked that be done before...

And no, the design of the board can't be changed...those of you that deal
with ancient military designs know what I'm talking about...

-Steve Gregory-

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