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How many 0 Ohm, 0402 resistors to conduct 10A??......

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Smokey:
This is sort of a silly question, but I think it would be interesting to hear all the opinions.

Say I have a properly sized 10A trace on a board.  I want to make the voltage on that trace selectable (5V or 12V) based on component stuffing but I can't add any other line items to the BOM.  What I do have is a thick film, 0402, 0 Ohm resistor already on the BOM that I can add more locations to.  This part is not specified to act as a high current shunt.  It's just a generic 0 Ohm resistor.  To make it interesting, lets say that's all the information you have about that particular resistor.

So the question is... If it was your only option, how many generic 0 Ohm, thick film, 0402 resistors in parallel would you feel comfortable to conduct 10A.

ArdWar:
Most thick film jumpers are 50mOhm (regardless of size since they all more or less same aspect ratio), and most 0402 are 1/16 W rated. You can calculate I2R from that. Don't forget to derate.

Use metal film jumpers if you're that concerned with current carrying capacity. It's much better than thick films, and not as expensive as current shunt.
Example: https://www.digikey.com/en/products/detail/thin-film-technology-corp/D1LPC0402CJUMPF-T10/18158218

Monkeh:
IME they're usually stated as being up to 50mΩ and 0.5A to 1A. So 20 of them will make me sleep at night. In practice you'd probably get away with 5 or 6.

tooki:

--- Quote from: ArdWar on June 16, 2024, 11:09:45 am ---Use metal film jumpers if you're that concerned with current carrying capacity. It's much better than thick films, and not as expensive as current shunt.
Example: https://www.digikey.com/en/products/detail/thin-film-technology-corp/D1LPC0402CJUMPF-T10/18158218

--- End quote ---
Did you miss the constraint of “I can’t add any other line items to the BOM”?

Psi:
I would just solder some onto a random test PCB and then do some testing. Figure out how many works good temp-wise and then add 50% more.
Use solder paste and only add a tiny bit when reflowing them to the PCB, you want to replicate how a paste/SMT reflow machine will solder the resistor.
If you use an iron you'll probably get excessive solder on the pads and that will give them extra heatsinking.
Don't forget you can add extra/wider pcb tracks from a resistor to decrease it's temp for the same power rating.  And having them spread out is better than bunched up which makes a hot spot.