Been through this years ago. You will find everyone has trace widths and
pads that they like to use. I am sure the calculations are correct but I
wouldn't use a 1mil trace in homebrew. I made a test board years ago to see
how many amps it takes for a trace to fail. Made each trace from 6mil to
100mil. That's when I found out that the inkjet printer doesn't recreate
trace widths accurately. Only laser makes the traces right. Hooked up the
wires got a 12v motorcycle battery a good Fluke meter with auto peak and
started testing. If my memory is correct the .006 trace failed at 1A. The
.010 3Amps. The .020 5Amps and so on. I found that solder coating not only
protects the trace but almost increases by 2/3 the Amps it can handle.
I like overkill on my circuits the biggest trace I can fit that doesn't take
up too much board space. I use the funnel type of design big end at the
power source or buss supply to the smallest trace at the lowest amp part of
the circuit.
I usually don't go below .020 trace anywhere on the board.
It is too hard to make a board with anything smaller and why do it if you
have the real estate use it, less etching.
As for the pads I like to drill 100mil and for power diodes and wire inputs
150mil.
Derek B.
http://groups.yahoo.com/group/Denver_CNC_Club/ >
> 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?
>
>