Dear Ian
When I calculate the current of  a .035 mil .002 via I do not get 10 amps,
ether by the curcumfrience  or the 1/2 method. Think of a via as a cardboard
tube  if you fold it together it is 1/2 the curcumfriance wide and twice as
thick. The reason for the fold method is the via is like two resistors in
paralell ( sorry i cant spell this early in the morring), using the standard
current chart I roughly calculate a .035 via at .0175 * 3.14 = about .055
wide and .004 thick
the current capacity is only 4  to 5 amps at 35 degrees, and 12 in paralell
would only give you 48  to 60 amps .
I have worked with heavy copper an big current boards all my life and from
time proven tests I do not like to push a via with current, two problems,
first the via is never sold even copper, they are full of thin spots and low
density copper. second if you heat a via up to much it fails, the heat
causes the barrel to expand and push up on the top pad, and it will crack.
I wrote a book on power and printed circuits,that may help you if you are
interseted you can e-mail me at [log in to unmask]

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