Proper Ground Return Via Placement for 40+ Gbps Signaling

As signaling rates move beyond 40 Gbps, a proper understanding of Ground Return Vias (GRVs) is imperative. For decades, engineers have placed GRVs next to signal layer transitions based on best practices, with little understanding of relevant quantity and spacing. Place GRVs too far away or pinout a ball-grid array’s GRVs incorrectly and a signal via’s insertion loss (IL) can drop 40dB. This paper explains the science behind GRVs using practical examples confirmed by mathematics, measurement, and simulation. GRV placement’s relationship to data rate and impact on IL, Via Impedance, and Crosstalk are described.

This paper was presented at DesignCon 2022.