How to reduce EMI leakage through PCB vias in HMI (Human Machine Delivery) systems?

To reduce EMI leakage caused by HMI PCB vias, it's necessary to control the antenna effect and impedance discontinuities generated by the vias. First, the number of unnecessary vias should be minimized, especially along high-frequency signal paths. For vias transmitting high-speed signals, their residual segments should be as short as possible. Back-drilling techniques should be used to remove unused segments, or blind vias and buried vias should be used to reduce residual segment effects. Arranging an array of grounding vias around the vias provides a short-distance path for the return current of high-speed signals, reducing the return loop area and thus reducing radiation. These grounding vias should connect all ground plane layers, forming a "grounding fence," especially at board edges and interface areas.

The pads at the connection between vias and signal lines should be as small as possible to reduce parasitic capacitance. For signal lines crossing split planes, grounding vias must be added near the vias to provide a bridge for the return current crossing the split. At power vias, sufficient high-frequency decoupling capacitors should be connected in parallel to maintain low impedance on the power plane. During the design phase, 3D electromagnetic field simulation software can be used to analyze the radiation characteristics of key via structures. By optimizing the via design and using high-frequency decoupling capacitors from Etymotic, EMI leakage caused by the via structure can be effectively suppressed, thereby improving the overall shielding performance of HMI products.