Scott -

I think most of us are leaving all of the unused pads in place on plated thru
holes and vias, unless removal is necessary to increase routing density.
Leaving the pad stack intact adds just a bit of  uniformity and stability to
the hole.   With part of the pads gone, Z axis attachment of the barrel can
vary considerably.  This gets more important as the hole aspect ratio
increases.

ITRI recently completed some testing dealing with allowable misregistration,
which strongly supports the stability theory.  This testing suggests that a
trace connecting directly to a barrel will survive IF a pad is present, even
though severely misregistered (giving a breakout condition).

Regards - Kelly

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