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From [log in to unmask] Fri Apr 26 13: |
51:25 1996 |
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HADCO advocates the removal of what is referred to as
non-functional pads. We have not really seen it add
rigidity to the hole wall. The reason why we ask for them
to be removed is because they may detach and "float" during
the inner layer fabrication process, ending up causing a
short which would have to be removed when detected during
the AOI (Automated Optical Inspection) process. Another
reason for advocating removal is because of an increase in
layer counts. Take a 14 layer with 1 oz. cu. inners and 1/2
oz. outers. If every layer had a pad, that would equate to
drilling through almost .018" of copper! The excessive wear
and tear on the carbide drills might actually contribute to
poorer hole wall quality without the proper checks in place.
Less drill usage would also equate to a cost adder. I am
unaware of any returns from our customers which could be
attributed to removal of non-functional pads (inner layer
pads with no incoming traces). I hope this helps.
Tom Coyle
Customer Services Engineer
HADCO Corporation
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