How to reduce EMI through I/O module vias

Proper via design is crucial for reducing EMI on I/O module PCBs. First, the number of vias should be controlled; unnecessary vias should be avoided. For critical signal lines, the number of vias used for layer transitions should be minimized. The parasitic inductance of vias can degrade power integrity and generate radiation; therefore, multiple vias in parallel should be placed near power and ground pins to reduce impedance. Grounding vias should be placed near signal vias to provide a path for return current, especially during high-speed signal layer transitions, using a "via-signal-via-ground" configuration.

Avoid placing vias below strong radiation sources such as crystal oscillators and clock lines to prevent noise coupling to other layers. Via studs should be as short as possible; for high-speed signals, back-drilling can be used to remove unnecessary studs. The via diameter should match the pad diameter to avoid excessive parasitic capacitance. On the ground plane, via arrays can form localized shielding cavities. 3D electromagnetic field simulation can be used to evaluate the impact of via design on signal integrity and EMI, and optimization can be performed.