-- [ From: Douglas C. Jeffery * EMC.Ver #2.10P ] --


Tom Hybiske asked about "the inclusion or exclusion of nonfunctional
lands from internal planes or signal layers"...

We have been asking that non-functional pads be removed on dense
designs (.005" lines and spaces) to reduce the incidents of .005"
spacing.  This improves the manufacturing window for imaging and
etching these layers.  On some designs we prefer to leave the pads in
as they act as filler for lamination( when a signal layer is very
sparse).  All in all for MLB's up to 12 layers I feel the pads should
be removed to help "clean" up the image and improve the yield.

We haven't addressed the issue of pth support from the pads as we feel
that an uninterrupted hole wall will plate better than one with lots of
surface changes.  The lack of pads does improve drill wander and help
with tight registration designs especially with todays ultra thin
designs that can be 30% to 40% copper (thickness).

Doug Jeffery
Electrotek
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