Characterization of signal via structure in multilayer printed circuit boards up to 50 GHz

Interconnects in the latest servers need a transmission capability of tens of gigabits per second (Gbps) for high-speed digital circuits. For the system board in servers, the impact of losses in through-hole vias on the performance is large in the region of tens of Gbps. In this paper, we discuss the capability of 100 Gbps electrical signal transmission in typical through-hole vias in a system board. After the simulation model and the simulation results are validated by measurements, the causes of losses are analyzed in detail on the basis of the simulations. Consequently, it is confirmed that the reflection and the radiation losses are dominant. To reduce the reflection and radiation losses, we investigate the signal via structures and ground and differential via structures, respectively. As a result, it is clarified that these losses can be reduced by designing the above mentioned structures appropriately.