Our chip carrier product is experiencing a very interesting problem.
Random
features on the product are not plating in the Ni cell. A thick Cu seed
layer
with a photo mask is pattern plated in Cu and then goes directly to our
Ni/Au
operation. After Ni/Au we find that some features are totally devoid of
Ni! The
Au still plated (to full thickness) so I know the seed was still intact
(commoned).
The Cu plated well, so I discounted the possibility of a resist residue.
A colleague
mentioned skip plating. I've heard the term before, but I can't find
detailed
information in any of my reference books. Anybody want to fill me in? Or
speculate
on this intriguing phenomenon?

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