To All,

I think we can not overlook other aspects of having non-fuctional pads.

1. With cores getting thinner in products today, the more reatained copper
on the layer the better the dimensional stability will be.
2. For x-section analysis it is far better to have a complete pad stack to
verify registration.
3. On high aspect ratio holes(>8:1) we need to look at the interconnect
stress.  We have built a significant amount of 18 layer product around .105
thick.  Initially without non-functional pads present.  Product was
assembled and opens were detected in ICT test.  In ALL cases the opens were
traced back to components or via holes that had interconnects only on
layers 1/2 and 17/18.  The next revision product was built with non
functional pads included and no defects were detected after assembly.  This
was not an isolated occurance and was not dependant on resin system(high Tg
materials minimize but do not omitt the condition).
4. In our porducts the inclusion of non functional pads has shown to
minimize the amount of drill splay on small holes(<.012)

I am not sure of the parameters of the commisioned testing that is
currently underway.  I hope this will address the higher aspect ratio
problems that are out there.  It has taken us years to overcome the stigma
of the last round robin test where a great deal of our customers were
afraid(based on that report) to design product that violated the findings
of that testing.

The only negative that we have encountered with including non functional
pads is, the increase in capacitance on some higher speed designs.  This
needs to be modeled and accounted for prior to routing.

Regards,

Alan B. Cochrane
Corporate Director of New Technology
Multek Inc.

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