EMI Bites: The best way to use a 2-layer PCB is... to not use it at all.
EMI Bites: The best way to use a 2-layer PCB is... to not use it at all.
Jokes aside, don’t fall for this common mistake.
Two-layer PCBs are not meant to have both layers used as signal layers.
From a signal integrity and EMI perspective, this setup will only cause problems.
If you understand that signals propagate in the space around and between conductors, not in the conductors themselves, then you probably already see the issue this creates.
When both layers are needed for routing, the best way to reduce EMI is to upgrade to a 4-layer board.
And I get it, 4-layer boards increase the overall project cost.
But the real problem isn’t your budget.
The problem is assuming your design fits a 2-layer budget when it actually requires a 4-layer stackup.
So, if you want to avoid EMI and signal integrity issues, your options are:
- 2-layer stackup: Route all signals on one layer and use the second layer as a solid return & reference plane.
- 4-layer stackup: Use two layers for signals, and dedicate two layers to solid return & reference planes.
Quick tip: Stop thinking of signal propagation as something happening in the conductors.
Start thinking of conductors as boundaries and guides for the electromagnetic fields.
This mindset shift will immediately improve your EMC results.
Hope this helps.
To electromagnetic enlightenment,
Dario
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