[SI-LIST] Re: Ground clearance at connector vias

Fabrizio and all the others:

> I have a question regarding ground clearances for signal vias in a
> backplane connector, like the Molex/Teradyne HSD.  Connector and
> semiconductor manufacturers recommend using an oval ground clearance
> around the differential pairs, to minimize reflections.

I completely agree that increasing antipad sizes is one way to reduce
parasitic via capacitiance. What makes me wonder is the fact that 
oval shapes are proposed. Is that a mechanical/space requirement?

If not: has anybody ever seen a difference in via transmission between a
circular and an oval antipad of the same area?


Regards,

Christian Schuster
IBM 



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