Richard O. Carlson

Characterization of via connections in silicon circuit boards

Conducting vias, isolated by silicon dioxide from a bulk silicon wafer and used to interconnect stripline transmission lines on opposite surfaces of the wafer, are analyzed. The net VSWR (virtual standing wave ratio) and insertion loss for a single via and the crosstalk or coupling between two nearby vias are determined as a function of geometry, frequency, and silicon resistivity. For small via dimensions and frequencies up to 1 GHz, the analysis predicts low VSWR and low insertion loss, provided the silicon resistivity is greater than about 100 Omega -cm. It is shown that crosstalk can be small, and is mostly due to inductive coupling. >