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I want to create a PCB with some traces on the solder layer, so I can reinforce them with tin.

Those traces will use AC current and about 5 amps. So I want to create some traces with 3mm wide and tin above.

I just see options to create traces on top layer and bottom layer. How can I create a rule to create those traces on solder layer? I am not sure which layer I need to choose neither.

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  • \$\begingroup\$ Conductivity of copper is 6x of solder. In other words, it is almost not worth the trouble. \$\endgroup\$ – mkeith Aug 20 '16 at 8:45
  • \$\begingroup\$ How can I calculate the width of a copper trace for 5 amps in 220v AC? I am afraid of creating traces too small. \$\endgroup\$ – Biribu Aug 20 '16 at 8:53
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    \$\begingroup\$ 4pcb.com/trace-width-calculator.html \$\endgroup\$ – mkeith Aug 20 '16 at 9:27
  • \$\begingroup\$ If you have the option available, you should use thick copper for this trace. For example, 2 oz copper (which is around 70 um). This is something that you specify in a "fab drawing" which you send to the board manufacturer. \$\endgroup\$ – mkeith Aug 20 '16 at 17:24
  • \$\begingroup\$ 2oz copper is 0.07mm thick, so adding 1mm of solder, even if it's 6x less conductive, still means reducing the resistance by more than 50%, plus it adds a significant amount of thermal mass and (slightly) more surface area. If you are putting a lot of current through the trace this makes a big difference. \$\endgroup\$ – BeB00 Aug 20 '16 at 19:10
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If you want to remove solder mask above the trace, just select all the segments of the trace and use PCB inspector to set the Solder Mask Expantion Mode to From Rule.

enter image description here

If you're not fussy about how the paste is added, you can also define paste expansion in the same place.

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