In a message dated 12/14/2006 4:24:06 P.M. Eastern Standard Time,
[log in to unmask] writes:

What  actually causes something like that? The panel that we're working
with is  only about 6" X 6", so I should expect that there's at least
another half  dozen or so panels out there that might have this problem
depending on how  big a panel the board house was building, right?
Further still, how does  one panel get screwed-up like this and not  the
others?



I think you have a classic case of voided PTH holes.  With no plating  in
circumferential rings, I would say there was more electroless or direct plate  on
certain layers of epoxy glass in the holes - could tell you more as to why if
 it were a multilayer.  If a lot of the panels had the problem, I would
point to the plating line as being out of control when the job ran.  But,  if you
really do find only one panel in the lot with the problem - something
happened to that one panel.

For instance, it could be that the image for the circuit traces as not
registered properly.  So, the image was stripped off and the panel was sent  for
re-imaging.  Probably went back through the microetch line before dry  film, and
that might have destroyed the copper plating in the holes. Or if it  was
direct plate, it took too much of the carbon out of the hole, so there was  poor
electroplate.  See if the fab can tell you their procedure for  in-process
re-work during fab.  There are other causes, for sure.

Denny Fritz
MacDermid, Inc

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