You simply take the length the via is carrying the current and divide that
by the circumference (pi * d). For power designs, you should insist on a
full ounce on the via wall. One ounce copper film is 0.7 milliohms/square,
so you just take the calc above and multiply by 0.7 and now you have the
resistance of a single via. Multiply that by the current to get voltage
drop. If the voltage drop is too high, the via will get warm and someone
will complain about your lousy power distribution system. So add vias, or
make bigger vias until you're sure that won't happen!

Wayne Thayer

On Fri, Jan 19, 2018 at 11:00 AM, Nutting, Phil <[log in to unmask]>
wrote:

> Many of our designs use 1, 2 or 4 ounce copper for our heavy current
> applications.  Vias and plated holes might have ½ or 1 ounce of copper
> plated in.  So, is there a design guide for the number and size of holes to
> effectively transfer the current from one side of the board to the other
> side of the board?
>
> Phil Nutting  |  HVP Senior Development Engineer   |  Excelitas
> Technologies Corp
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> Lab: +1 978.224.4332   |  Office: +1 978.224.4152
> 35 Congress St, Salem, MA  01970 USA
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