I typically handle vias as inner layer traces, Then derated them anywhere up
to 50% depending on the requirements for the design. (steady state current
vs max current, duration of max current, etc.)
I haven't had any vias burn up during testing for Military use (brutal).
Regards;
Tom G.

Abd ul-Rahman Lomax wrote:
>
> At 02:49 PM 11/17/99 -0800, Rodney Carrico wrote:
>
> >To the best of our knowledge....
> >The current carrying capacity of a blind micro-via is calculated just as you
> >would for any other via or flat conductor - by finding the minimum square
> >area of the conductor's cross-section, then using the IPC-2221 "Conductor
> >Thickness and Width" charts.
>
> This may be good as an approximation, but the heat dissipation will vary
> for a trace depending on whether it is a surface trace or a buried one. I'd
> think a via might be somewhere in between, and a blind via would be even
> more like a buried trace. Fortunately, vias are typically fairly short.
>


--
Tom Garman KC4WAR           Telephone   614 860 6064
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