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Date: | Thu, 14 Dec 2006 18:43:44 EST |
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In a message dated 12/14/2006 5:32:18 P.M. Eastern Standard Time,
[log in to unmask] writes:
So that I might learn something here as well, wouldn't poor drilling tend
to
cause more of a hole void instead of a ring void?
To me, poor drilling does either of two things - it rips the glass and makes
a very rough hole, or there is resin smear (melted epoxy) in the entire
barrel.
Rough holes are very easy to spot when cross-sectioned in the 45 degree mode
(discussed on TechNet a couple weeks ago). That is, section in the 1:30 to
7:30 and 4:30 to 10:30 directions, as if the hole were a clock face. Rough
drilling traps bubbles preventing electroless or direct plate deposition.
That results in blow holes, but not really in circumferential voids, as seen
here.
Entire drill smear on the hole wall may plate, but you get massive
hole-wall-pull-away when the board sees assembly heat. Sometimes this is so bad the
hole wall buckles and it looks like a "5 point star" from the top down, not a
circle.
To me massive voids says the electroplate copper had nothing conductive to
carry current in the hole. Now, I am wondering why there is any copper in the
center of the hole. A good cross section will let the fab shop know the
problem source.
Denny Fritz
MacDermid.
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