Hello there!

    In regards to your reply about witness marks, I do agree that having them
CENTERED on the pads are no problem whatsoever. I do agree with you that
seeing them on the pads is a indication that the fab did indeed go on to some
sort of fixture, but it is not an absolute guarantee that the board is free
from internal shorts or opens. Yes, a indication that it is likely free from
defects, but NOT a guarantee.

But as I stated, having them off-centered to the extent that they deform the
intended outline of the pad is completely unacceptable. The fab vendor needs
to be competent in the design of the fixture to ensure that each board is
repeatably and accurately located during the bed of nails testing so that the
assembler recieves a PCB that is free from the kind of defects that WILL
affect yeild. If you've never experienced the problem that I spoke of, then
you are lucky to have a good fab vendor...

The times that I've had these problems was when I've been employed at contract
assembly companies and have had no control over the quality of the fab or the
parts. I've had to deal with kits containing 100-piece strips of passives,
IC's in plastic bags, and fabs with what I'll call; "witness gouges", all
thrown into a cardboard box and expected to turn this crap into gold turning
it around in three days...I'm sure there are some of you out there that know
what I'm talking about...

                                                                -Steve
Gregory-

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