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I have a two layer PCB, with signal traces and power traces on the top layer and a ground plane on the bottom layer. The top layer also has a ground plane extending over the space where there are no power or signal traces.

I have read that it is better to keep power traces far from signal traces to avoid parasitic coupling between both;

Q: Should I move my power traces to the bottom layer to move them further apart from the signal traces and use routing vias to connect the ICs instead?

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    \$\begingroup\$ Are the power traces low-voltage, well decoupled power for ICs? If yes, don't worry about it. \$\endgroup\$
    – Mattman944
    Sep 16, 2023 at 0:31
  • \$\begingroup\$ they are +-12V, they come from two LDOs at the outputs of a dual +-15V DCDC converter \$\endgroup\$ Sep 16, 2023 at 0:37
  • \$\begingroup\$ It all depends on what you are making, and what the signal environment is. Parasitic coupling is only a problem if it's between a trace with an aggressor signal on it, and a sensitive victim trace. Are any of your traces very noisy, or very sensitive? If yes, then minimise coupling, and maybe take other mitigation steps as well (shielding, minimising nasty emissions, reducing sensitivity). If no, then it's not a problem. Hint, properly decoupled power supplies are rarely a problem. \$\endgroup\$
    – Neil_UK
    Sep 16, 2023 at 5:44
  • \$\begingroup\$ Is your ground plane the same as "-" of unipolar supply and "0" of the dual supply? \$\endgroup\$
    – Maple
    Sep 18, 2023 at 15:03

1 Answer 1

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Really what you want to avoid is mixing the signals' fields and power's field together. Considering you are using a standard 2 layer PCB stackup, moving the power trace on the bottom layer will only add a distance of 1.5mm between power and signal. https://www.pcbgogo.com/blog/When_should_I_choose_2_layer_PCB_or_4_layer_PCB_.html

Depending on how much you want to minimize coupling, I would suggest the following:

  1. I think you would be better by keeping a complete GND plane on the bottom side. This will help restrict the spread of the fields.
  2. Futhermore, you can increase the distance between the power traces and the signals traces on the top side.
  3. On top of all that, you can add GND pours and stiching vias between your power and signals traces.
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