Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

previous by date index next by date
  topic list next in topic

Subject: Choosing a trace width

From: "ghidera2000 <ghidera2000@...>" <ghidera2000@...>
Date: 2003-01-01

Been checking the net and I've found a few trace width calculators.
I'm having trouble believing what I'm seeing though! I have two 7
segment displays (man71A). Each one takes about 80mA to operate. I
had just guessed and used a 20 thou' trace (0.02 inch). According to
the calculators I've found though, 1oz copper carrying 160mA with a
max temp rise of 5C only needs to be 0.0014 thou' (1.4 mills). Is
this correct? Are the trace sizes I see on boards as big as they are
simple due to limitations in the pcb making process and not for
carrying current?

What trace sizes do you generally use for TTL circuits?

And actually, while I'm at it - what pad sizes do you like to use?
PCB123's default pad size is 0.05 inch. Seems pretty small to me
but, I'm just a noob :D Any trouble soldering on pads that small?