[sdiy] Trace width and via diameter/hole size

[harrybissell]

WHAT are you building ???  Detonator ???

If you have special needs, contact me offlist.  For the most part,
power traces for s-diy can be .040 - .050" with no measurable
temperature rise.  I use .020 - .025" for signals.  I nick down to
.015 to go between resistors or IC pins.

Vias usually have better current carrying capacity than runs. The whole
inner barrel is copper plated.

If you are still worried, you can use two vias in parallel. Its
redundant
so even if one flakes out you are covered.

For really big stuff, an array of small vias is better than one big one.

You can specify plating to a greater copper weight... the standard is
usually
1oz copper, 2oz is common as well. A company called UPE will do high
aspect
ratio copper... as much as 10oz, 20oz, or even 30oz copper. THAT IS some

serious conductor !!!

H^) harry

Bert Schiettecatte wrote:

> > Hi Tim,
> >
> > > That's a complicated question. I wonder what that
> > > program conciders when it makes its determination.
> > >
> > > There is the fusing current, which the current at
> > > which a conductor becomes a fuse. Any current below
> > > that is fine, but you get voltage drops and thus heat.
> > > Conductors are usually choosen  to limit the voltage drop
> > > along its length. Ever wonder how they can get 140 amps
> > > through a HexFet in a TO-220 package? It's because the length
> > > is short enough to limit the voltage drop.
> > >
> > > If I calculated right, your trace has 0.06 ohms/inch.
> > > At 640mA the voltage drop would be 38.4mV, the power
> > > dissipation would be 24.6 mW/inch.
> >
> > Hmm.. How do I figure out if the traces will light up or what
> > Simple rule can I use to decide if I'm still ok with the PCB
> > Trace width? Is there a PCB guidelines table somewhere that
> > Tells you the minimum track width for a certain current?
>
> Ok an update, I've used traceres.ulp in Eagle which puts Current
> Numbers on the traces on all layers. You can specify a temperature
> Rise allowed (50 degrees celcius being standard??) and then you get
> The currents allowed through the traces. If the ambient temperature
> Is at 25 degrees celcius I find a rise of 50 degrees pretty scary
> But maybe that's just me.
>
> I am still clueless how to calculate the allowed current through
> A via.
>
> bert