There is a mix of opinions, including black pad, un-melted solder,
Nickel-Tin interface, reflow profile; ENIG is evil, wetting problems and
brittle fractures (and maybe more).  

I just finished checking the 20 boards we have on the shelf, finding 2
more with the problem.  On the bad assemblies, all of the solder pulls
off the PCB pad, leaving the pad with no Gold.  Turning my destructive
tendencies to assemblies; if I pull hard enough on the SMT electrolytic
cap, the cap leads pull out of the solder blob with the expected blob
surface tearing.

Our board assembly house has asked for the bad boards so they can
evaluate the problem.  They will probably have the experience to make a
proper determination of root cause.  If they do come to a conclusion,
I'll let the group know "the rest of the story".

Thanks to all who took time to share opinions and suggestions,
Carl





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