How much current can different copper weight PCBs handle? Not so muchin terms of how much can traces handle, but a PCB in general. I'mtalking strictly DC current, relatively low voltage (+24VDC).If traces are more or less avoided and copper pours are used for thehigh current nets, what would be a rough estimate of the maximumcurrent that could be run through 1/2 oz. PCB? How about 1oz. or 2oz.?I'm really just curious because one of the things I am thinking ofdesigning in the future is a motor driver, where the current couldreach 15A + continuous and could easily spike to 100A or more, in somecases. I know there are motor driver pcbs out there now that are verysmall size and can handle these types of current outputs, but I'm notsure what guidelines are used to determine what is needed (even copperpour area size) for high current in terms of a PCB.I am just a newbie, but when I hear about 20 to 30 amps being passedthrough a PCB, I get nervous... even if there was an entire planededicated to the high current power and ground. Am I worried for noreason? Can an entire plane of, say, 1/2 oz. weight, board size, say,9sqin or how about 25sqin handle 15-20 amps continuous (or at least fora minute or two)? How about a copper pour area of 1/2oz. that is sizedat about 1sqin? Could that handle this type of current?Any info on high current PCB design or any general high current designnotes would be greatly appreciated, or any pointers to where I couldget further information or maybe even calculations for amount of copperneeded to safely run certain current levels.

How much current can a PCB handle?

Aug 15, 2006 21 Replies

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Eeyore 19 years ago

Right, I'm thinking of some old BS we had an extract from.

Graham

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przemek klosowski 19 years ago

http://64.233.179.104/translate_c?hl=en&ie=UTF-8&oe=UTF-8&langpair=de%7Cen&u=

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Andreas Weber (author of AAcircuit) did measurements on a test PCB with .1" traces. He showed resistivity data, which seemed to go linear up to

10 A, and then show resistivity increase due to self-heating. I fitted his data and got 0.010 Ohm resistance for his traces and 35+-15 K/W thermal resistance for a zig-zagging shunt about 1.3 inch long and .1 inch wide on a plain PCB (he doesn't give much detail--I assume standard 1 oz)

The formula I used was U = R*I*(1+.0039*Rtherm*R*I.^2) where U and I are measured voltage and current, R is the ohmic resistance, .0039 is resistivity thermal coefficent of copper and Rtherm is the thermal resistance of this particular PCB trace configuration

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