How to reduce EMI leakage in industrial servo PCB vias?

Improperly handled vias on servo PCBs can become "antennas" for high-frequency EMI leakage. Etymotics reduces leakage through the following design measures: First, avoid using vias at the edges of shielded cavities or isolation zones to prevent noise coupling. For signal vias that must pass through the ground plane, add multiple grounding vias around them as "guard vias" to create a Faraday cage effect. Second, control the length of via stubs; for high-frequency signals, prioritize back-drilling to remove unwanted stubs.

Power vias should be used in parallel to reduce inductance; for example, provide at least four vias for a single power device. For thermal via arrays, cover the top or bottom with solder mask or fill the interior with non-conductive material to prevent them from becoming radiation gaps. Simulations and measurements show that optimized via design can reduce radiated emissions from PCBs by 3-5 dB in the 1-6 GHz range, positively impacting compliance with FCC Part 15 or EN55032 radiation limit tests.