I've searched Google and couldn't find a simple answer to this question. I'm guessing the only limiting factor is the solder's melting temperature? I don't think I should have a problem with < 20A, but now I'm just curious about this. I know the resistance of solder is calculated from its total area, but that isn't exactly easy to calculate. So I guess I'm going for more anecdotal evidence.
Anyone have experience using solder joints for high currents?
edit: Sorry, I meant for longer tracks of solder (oops)
Best Answer
I honestly don't know the answer to your question but I can point you in one direction.
I see circuit boards in commercial equipment where the traces have to handle significant current. What the manufacturers seem to do is to have a bead of solder down the middle of each high-current trace. The solder is usually not the full width of the trace but covers most of it (anywhere from 50% to 80% of the trace width).
What this does is improve the heat dissipation of the copper trace. It doesn't actually reduce the trace resistance very much - copper is a far better conductor than solder - but it gives both more surface area as well as more thermal mass.
As a production technique, it seems to work well. I rarely see damaged or destroyed traces unless the whole board section is blown up (including exploded relays) because of catastrophic shorts at the load terminals.