Two small vias a better than a large one, three are much better than two...
http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/

Vasile

On 1/18/07, Phil Keller <Phil@pkeller.net> wrote:
>  I have a design that is controlling an incandescent lamp with a
> current of about 1 Amp.  I am not as concerned with the voltage drop as
> I am with overall reliability and ensuring that the via does not become
> a fuse.  There are many places that help in calculating the suggested
> PCB trace width for a given current but what about the via?
>
>  The calculators tell me that the trace should be 30 mils wide.  (I use
> 40 to be safe.)  Now when I need to go from top to bottom metal, what
> size via (also called feed-thru holes) is required?  Drill size and
> overall diameter of the 'cover' metal?  The only reference that I was
> able to find indicated that the via drill size should be greater than
> the metal width/3.  So for a 40mil wide metal the drill size should be
> greater than 14mils.
>
>  Thanks for any suggestions.
> Phil
>
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