I modeled a via some time back with ground planes and
clearance holes through it. I had intended to use the capacitance
to make up for an inductance and needed 300 ff.
I used an OEA field solver Metal and to my amazement there was
hardly any capacitance. I surmised that this was due to the small
area of the ground planes in tha horizontal direction. Since I needed
capacitance I added some big fat ground vias all around the signal
via, and got the 300 ff.
Also, HP ADS which is the cadillac of RF simulators models vias
as inductor, as does Touchstone before EEsof got swallowed up by
HP.
Ron
Douglas McKean wrote:
> Could someone give rough estimate
> of via capacitance?
>
> I'm thinking the orientation of the traces
> connected to the via have a major impact.
>
> For instance, an .062 board with a via
> from one side to the other, different
> capacitances would be had with the two
> following constructions ...
>
> I. Top Trace
> -------------
> |via
> -------------
> Bottom Trace
>
> II. Top Trace
> -------------
> |via
> -------------
> Bottom Trace
>
> Ideas? Comments?
>
> Regards, Doug McKean
>
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Ronald B. Miller _\\|//_ Signal Integrity Engineer
(408)487-8017 (' 0-0 ') fax(408)487-8017
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