Hi, Earl,

Funny, your 10X pic looks like it's supposed to be like that - a missing
corner ball to denote orientation or avoid the stress build up that so
often fractures corner ball s-j's. On the other hand, your other two pics
look like a good IMC layer showing only tiny areas of alloying where solder
adhesion has taken place between the ball and the pad material.

Lousy supplier? Too many thermal excursions? Poor substrate plating? Only
suggestions, sorry. No learned or scientific disputation from me on these
things. I do generally wonder, though, how many times that interface type
is brought to reflow or near-reflow temps during component fab and when
it's mounted onto a board. It must suffer a bit.

Peter

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