Hi Al
Your photo showed no metallurgical microetch.  You might want to do that.
Since you didn't show the whole hole, we can't see if there was any tenting or
plugging of the via.  The microetch will reveal any attack on the copper hole
wall from entrapped contamination. The contamination will be the result of
insufficient protection of the via. This contamination will gradually eat away at
localized areas of copper until the plating is too thin and then will crack.
This is what your photo appears to be to me instead of the air entrapped
during plating or board fab.

Susan Mansilla
Robisan Lab

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