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How come there are components in TO220 packages that supposedly take 100A given their small legs? (programming.dev)

submitted 1 week ago* (last edited 1 week ago) by [email protected] to c/[email protected]

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Not sure if this is a dumb question but this has me quite puzzled.

The legs on TO220 packages are very small. How is it that there are e.g MOSFETS rated as being able to continuously conduct ~100A? e.g IRF1404Z

From what I understand such large currents need busbars on PCBs and these appear a lot larger than the legs on these components.

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[–] [email protected] 3 points 1 week ago* (last edited 1 week ago)

Thanks for doing the maths. I would have also have guessed it's due to the short distance these amps have to travel. And in practice, we'd likely be using just the thicker parts at the top of the legs and clip most of them off, so it'd be way less than the almost 15mm in your numbers. Still probably an issue with the thickness of the pcb traces, but that's something the designer has to worry about.