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

-- 
--------------------------------
Long ago when men cursed and beat the 
ground with sticks,  it was called witchcraft..

Today, it's called golf.


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