[sdiy] Trace width and via diameter/hole size

[Bert Schiettecatte]

Hi all,

I'm still working on a pcb here in Eagle, and I've been using the
length-freq-ri.ulp program to find out how much current can go through
my traces. It says 640mA through a 0.2mm trace. Is this correct? It
sounds like a lot of current through such a tiny trace. The copper
thickness is 0.035mm. 

This program tells you how much current can go through the traces, but
what about the vias? How do you figure out how large the via hole needs
to be to carry the required current? I searched and searched with google
but couldn't find anything about via size, only trace width and
clearance. 

Any ideas?

Thanks,
Bert