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PCBs, copper pours, ground planes, and you
A closer look at a fashion trend in printed circuit board design.
It’s a bit of a racket: you need to submit prototypes to an accredited laboratory, pay big bucks for RF testing, and face additional costs and delays if you don’t pass. Luckily, when one door closes, another opens: if the return current sticks to the outline of the top trace, as projected onto the rear copper plane, then we get a situation analogous to the common-mode choke: the magnetic fields largely cancel out and the impedance stays comparatively low. In practice, for the vast majority of hobby projects that use ESP32, Raspberry Pi, or 8-bit AVR MCUs, you don’t need to think about this too hard; add copper pours if it makes your life easier, not because the internet is telling you to.
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