PCB Track Width for High Current

Let's say I need a 20mm wide trace in 1oz copper to handle some high current. Could I just have a 10mm trace on one side and another on the other side, connected by a plated hole to handle the same amount of current?

Sadly, due to costs, I would like to avoid going with thicker copper on the board.

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What kind of current are you working with? It seems like you're talking about 10 Amps or more? – Daniel Jul 8 '14 at 22:13
Probably around 40A per trace. Maybe a little more. – Adam Haile Jul 8 '14 at 22:19
Is this a power supply circuit board or is this trying to run a bunch of LED arrays or something? – Funkyguy Jul 8 '14 at 22:21
It's an add-on board to a commercial power supply for the sake of adding current sense readouts. – Adam Haile Jul 8 '14 at 22:27
Related: This excellent reference - TI Analog Engineer’s Pocket Reference - 4th edition provides some useful information on PCB track current/ voltage drop / heat / fusing issues. Especially pages 55-68. – Russell McMahon May 5 at 5:30

What matters is your total copper cross section and the trace length. Both of these numbers contribute to the total resistance of the trace (if that's important) and the resistance per unit length which contributes to temperature rise (if that's important). If it's a DC current, there are no issues that I can see. For higher frequencies, you might be generating magnetic noise if your return trace is farther away. (Magnetic noise is proportional to current x current path loop area)

Here is a website that can help you calculate the total amount of copper based on the target temperature rise: http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

Edit: Another way to go on the cheap side is investigated by Dave Jones and Mike:

EEVblog #317 - PCB Tinning Myth Busting (14 minutes youtube video)

Does putting solder on high current PCB tracks help? (4 minutes youtube video)

Basically, leave your trace open on the soldermask, then go over it with a LOT of solder to beef up the trace cross-section. Another possibility is to just use a big fat wire to jumper it across your PCB.

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It's DC 5V. What is considered an acceptable temp rise? – Adam Haile Jul 8 '14 at 22:09
It depends on your ambient operating temperature and the temperature range of the PCB material and any nearby components you might heat up. The total wattage given off (determined by trace resistance) might also contribute to a need for a fan. – Daniel Jul 8 '14 at 22:11
Oh, there will certainly be a fan. I just wasn't sure if I could go above the typical 10C – Adam Haile Jul 8 '14 at 22:18
Very nice videos. I was assuming that any added material (solder or extra wire) would need to go all the way from contact to contact but Dave's left a gap at the end and still got a 50% decrease I guess that small gap doesn't really matter. I think I'll go with soldering a 6 gauge wire on the trace or something. – Adam Haile Jul 9 '14 at 3:38
The tinning is going to reduce the resistance per unit length of the wire... so even if a small piece of the wire isn't tinned, the overall resistance will go down because the untinned part is small. The untinned part will still suffer from higher temperatures than the rest though. – Daniel Jul 9 '14 at 5:28

Well, sort of. The two 10mm tracks will not handle quite as much current as a single 20 mm track, since the substrate will be heated on both sides and will get somewhat hotter. The big limiter will be the plated-thru hole(s). The total amount of copper in the hole barrels will not be anything like what is in the traces. If you're going to do this, use multiple holes (big ones) and solder some wires in the holes to beef up their current capacity.

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