Phillip E. Hinton wrote:-
> One of the fears is not just electrical shorts, but potential
>shorts where spacing is reduced down to 0.001 inch by breakout.  The
>integrity of the interconnection of the completely circumferential annular
>ring seems to be less of a problem per the ITRI report.

I agree, if the spacing between the hole and surrounding copper ground
or traces is critical, then why make the pads so small that breakout is
likely. If the pads are large enough to cope with all the potential
misalignments then the spacing will be consistent. This also avoids the
limitations of some layout packages which route traces too close to
holes on inner layers. If the pads are too small, the spacing has to be
increased. By making the pads larger on inner layers, the layout is
improved and there will be fewer conflicts at the CAM stage which delay
manufacture. Check with the fabricator what limits they place on inner
layer land and spacing before firming up on the design and bear in mind
the cost of tight clearances which may restrict panel size.

--
Paul Gould
Teknacron Circuits Ltd
[log in to unmask]
Isle of Wight,UK

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