Thanks Steve,
This was new to me as well until somebody mentioned it in one of my
workshops. What is bad about 'Champagne Voids' is that they are all concentrated at the
pad/SJ interface, and thus, severely weaken an interface that already has the
smallest cross-section for a BGA SJ.
From my other source, I thought maybe it had something to do with immersion
Ag, but this paper shows it for all surface treatments--thus, it has to be the
copper plating of the PCBs. The Bryant-paper unfortunately shows no
x-sections, but my other source shows all the voids on the PCB side.

Werner

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