> From: Jana Carraway <[log in to unmask]>
>
> If there are any designers out there, perhaps you can help me with a
question.
>  My question(s) is: how do you calculate the current carrying capacity of
a
> via?  I have calculated the area of a 6 mil via and a 4 mil trace to the
via
> and the area of the via is about 100x that of the trace.  But, how do you
> calculate this with respect to a power layer?


Well, now I think I need a reality check here ...

I'm running a little Excel spreadsheet program that gives me
EXACT numbers. I realize no one works with "exact" numbers but
just for something to gage things by.

Anyway, with what you're using above (6 mil via, 4 mil trace),
I get a 10x factor if I use 1/2 oz Cu between the area of
the trace with the area of a solid via.

If I were to have the barrel of the via plated to a
certain thickness instead of being a solid plug and
I wanted to impose the same cross-sectional area for
the plated barrel, the thickness of the Cu down the
via would only be  0.15 mils.

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