Broadband via transition analysis and characterization

This paper presents a new methodology to analyze the key aspects of via transition. Proliferation of mixed-signal functionality in modem applications is strongly driving the level of physical integration where the performance of vias is becoming highly critical. Previous proposed methodologies do not accurately model the return current path and hence, the power plane cavity resonance is not included. As a result, crosstalk characteristics are not well modelled. A new methodology is proposed to accurately account for interaction between cavity resonance and via transition. Test vehicles comprising of multi-layer ceramic and FR-4 substrates were fabricated. Test vehicle characterizations were carried out to demonstrate the impact of power plane resonance characteristics on signal via transition. Measurements in both frequency and time domain indicate that the proposed approach does not suffer from inaccuracies in broadband performance prediction, particularly in terms of return current path and cavity resonance interaction. In addition, it was shown that the use of ground vias will not only enhance impedance matching but also significantly suppress noise due to power plane resonance.