General rule for mA per mil track width?

[sjalloq]

Hi there,

I’m new to designing PCBs and just realised I don’t know something that seems like it should be a basic rule.

I have a track that is supplying current to a bunch of relays. The max current draw on this track is <400mA. Is there a general rule that states I should be using some sort of minimum track width for this trace?

I currently have it at 24mils. Is that enough?

Cheers.

[sjalloq]

OK, I know I know, I really should use Google before I post.

Just found this useful calculator: http://www.circuitcalculator.com/wordpr … alculator/

[Dielectric]

If you’re using Eagle, there’s a sweet ULP that displays the max current in every trace on your board, based on your max temperature rise. It’s called traceres.ulp, and it’s on the main Cadsoft site.