In a message dated 12/15/2006 8:59:36 A.M. Eastern Standard Time,
[log in to unmask] writes:

Another  possibility is that the single panel was reworked through
immersion  silver.  Immersion silver is notorious for etching copper as
it  plates.  I've seen it lift narrow traces right off the substrate.
The  voids probably just correspond to naturally low areas of copper
plating,  whether from PTH or electrolytic copper.


**************************
I still vote for an imaging problem and rework (maybe more than once) at
that step.  There is nearly breakout of the surface pad at the 2:00  position of
the holes.  I am 99.9% sure this is NOT an immersion silver  problem - first,
the fine trace is OK,  and second, the small hole appears  fine.  Any silver
attack problem is usually associated with an  electrochemical cell set up
between large copper and small copper areas (fine  traces).  These sort of
"electrochemical cells" have been shown for years -  such as where 0.5 ounce inner
layers in holes are recessively etched, compared  to adjacent 2 ounce inner
layers in MLB holes.

Denny Fritz
MacDermid, Inc.

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