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Just a simple question related to AC traces. I’m designing a PCB that needs to carry 32 A @ 220 V.

I have designed a 15 mm trace (2 oz) that should guarantee a 13 degree temp increase at max power.

I see it’s common practice to add solder on those kinds of traces.

My question: As this would be a commercial product, are there any regulations about having non-covered traces with added copper? Can this kind of practice make me fail CE certification?

The PCB is enclosed in a box and traces are on the lower part.

winny
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giorgio
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  • How were you planning on applying solder over those traces on a production scale? Wave soldering them? – DKNguyen Oct 07 '21 at 20:04
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    If the traces are bare, then the spacing requirements are larger per IPC standards: https://resources.altium.com/p/using-an-ipc-2221-calculator-for-high-voltage-design – Aaron Oct 07 '21 at 20:05
  • Might want to look at this exchange: https://electronics.stackexchange.com/questions/197053/adding-solder-to-pcb-traces-to-increase-current-flow – SteveSh Oct 07 '21 at 23:42
  • _"13 degree temp increase at max power."_ I see no reason why this would fail your CE certification. I've ran at least secondary side traces hotter than that and passed. There are however more stringent limits on any protective earth traces and components. 25 degree C max IIRC. – winny Oct 08 '21 at 09:47

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The conductivity of copper is much better than that of added solder. So the change of the resistance of that kind of traces is very small. Adding solder to traces to decrease their resistance is not worth the effort.

Using very thick copper for high current traces is much more effective. Not 2 oz 70 µm 2.74 mils but up to 30 oz 1.04 mm 41.1 mils.

See https://www.epectec.com/articles/heavy-copper-pcb-design.html

The same cross-sectional area of the trace may be acheived by 4 oz and 1 inch or 8 oz and 0.5 inch or 16 oz and 0.25 inch. Maximum current and heat-rise will be the same for all three traces.

Uwe
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  • Also probably not consistent enough to be a great idea for 32Amps at 220V AC. – Wesley Lee Oct 07 '21 at 21:05
  • 30 oz sounds a bit excessive. For 32 amps, 4 or 5 ounce copper should be okay, if you use really wide traces, and it's not as difficult to find a PCB fab that can do 4 ounce as it is to find one that can do 30 ounce! – Hearth Oct 08 '21 at 00:05