I have had some discussion with this a year ago or so, and I have
come to the conclusion that we should leave the pads IN.
>From the explanation I got from a very good source whom I trust,
the reason to leave them in has to do with the movement of the
fiberglass during heating/pressing. If you remove the lands on inner layers,
you have a more likely chance that the fiberglass will shift more - there
is less copper to keep the "strength of the fibers" from moving too far.
I know there will be more knowledgeable answers coming on this - people
in the bareboard business - but that was the gist of it.

I think of the inner lands as little "anchors" which keep the movement
of the material stable. I would suppose that if there is an ample amount
of copper evenly distributed on the layer then the inner pads are less important
for this reason. 

I also think of this as being analogous to the outer layers "plating equalization"
issue. If there is sparse routing on large outer surfaces you get copper build up
on those traces because there is nothing  to steal away (thieves) the plating.


Tom Kavendek
Lucent Technologies
Murray Hill, N.J.

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