Physical scaling effects of differential crosstalk in via arrays up to frequencies of 100 GHz

Data rates on copper-based links are now increasing beyond 50 Gbps which requires frequency-domain analyses up to at least 100 GHz. This work investigates for the first time the frequency behavior of differential crosstalk inside a via array for frequencies up to 100 GHz. It is shown that the crosstalk does not increase indefinitely with frequency. We evaluate if efficient modeling tools like the physics-based via modeling can be used for crosstalk assessments up to 100 GHz and compare the results with full-wave solutions. A reduced model with a single cavity is sufficient to predict the overall frequency dependence of the crosstalk inside the array. The effect of scaling down the geometry of the array is investigated. The via pitch is identified as the parameter with the greatest impact. For a frequency of 50 GHz a reduction of the via pitch from 80 mil to 40 mil could reduce the crosstalk by about 30 dB.