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Date: | Wed, 16 Jul 97 02:58:05 PST |
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While I applaud the logic in saying that the post drilling wet
processes only expose the problem and are not the cause, I believe the
logic should be taken one step farther. If you look at the drilling
process, it is difficult to visualize a .0135" diameter drill (that
will break if you look at it cross-eyed) pulling layers apart.
Consider also that the stack is clamped with a pressure foot before
the drill touches the stack. I believe that drilling is very seldom
the cause, rather it plays almost the same role as the post drilling
wet processes by exposing the layer to layer join in the hole wall.
Also, my experience has been that wedge voids and pink ring will
happen on only one layer (possibly two) and not on the others in the
same panel. Again, it's difficult to imagine a drill bit selectively
wedge voiding a hole wall at one specific point in the panel
especially when the drilling takes place in a two or three high stack.
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