Black Pad article in SMT Magazine
Black pad was a big problem a few years ago when ENIG (Electroless Nickel Immersion Gold) finish boards first started popping up. It's not so much of a problem these days, but we do still see it from time to time.
If you think you may be having black pad problems with you ENIG boards, or similar problems with immersion silver boards, Check out the article Screaming Circuits recently had published in SMT Magazine online.
Just note that down near the end of the fifth paragraph, I say that problems with the "tin" layer lead to black pad. It's really the nickel layer that causes the problems. I inadvertently said tin. One of our readers pointed that out to me. Oops.
Don't look; Heisenberg may have been right...