Get back to your board supplier as soon as possible and discuss. I haven't
seen, or even heard of this problem in over six months now. I am in touch
with many ENIG users - as designers, assemblers, and test folks using mostly
the big board fab houses though some protos are made in smaller shops.

I hope the problems is lessening because board shops are doing a better job
with better plating/coating chemistries and processes. Much has been written
on this problem on this forum, so look in the archives.

Black pad is exactly as you describe and opens are easily found during test
but that's very unfortunate as then it's way too late. As received, you
cannot tell the problem exists.

Visually, upon device removal, non-wetted pads appear black where
non-wetting is observed often with solder "bumps or ridges" where wetting
did occur.
There is no possibility of rendering the black surfaces solderable. You
can't scrape it off and no matter how many times you try, you cannot solder
to it though I did once have success taking the boards back to the supplier
and have them HASL coated after stripping off the surface coating.

Wish you the very best in your unfortunate situation,

MoonMan

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