How to improve EMC in EPS multilayer boards?

Optimizing the stack-up structure of EPS multilayer boards is one of the most cost-effective ways to systematically improve EMC performance. The core principle is to provide a complete return plane for signals and power decoupling. Optimized stack-up strategies include:

1. Signal layers adjacent to reference planes: Ensure each high-speed signal layer is adjacent to a complete ground plane (or power plane), providing a defined low-impedance return path for signal current and acting as shielding.

2. Power-ground plane pairing: Place the main power and ground planes closely adjacent to each other, forming a natural planar decoupling capacitor, providing excellent decoupling for high-frequency noise.

3. Symmetrical structure: Use a symmetrical stack-up design (e.g., Top-Gnd-Sig-Pwr-Pwr-Sig-Gnd-Bottom) to prevent board warping and balance electromagnetic field distribution.

4. Critical signal inner layer routing: Route the most sensitive (e.g., analog sampling) or noisiest (e.g., clock, drive) signal lines on inner layers, using upper and lower reference planes for shielding. Avoid routing high-speed signals on outer layers unless there is a complete ground plane underneath.