Improvement on return-path-discontinuity issue through RLC termination for plating-via-stub

摘要

Due to low cost and easy manufacturing, plated-through-hole (PTH) via has extensively deployed in multilayer board/package compared to other types of via. Via is extensively used to connect one layer to another layer. However, via transition might lead to return path discontinuity (RPD) issues due to stub if it is not properly handled. Stub is the unused length or portion of via due to the transition between respective signaling layers. Stub introduces impedance mismatched at the via transition due to unterminated excessive length and shunt capacitance, thus introduces signal integrity issue. In this paper, the RPD effect is studied based on the three different configuration of through hole via for microstrip to stripline via transition of 8-layer board. A 3D electromagnetic field simulator, HFSS will be used to model via stub with recommended stack-up. Subsequently, analysis of RC and proposed RLC termination were carried out on the plating-via-stub introduced at the bottom pad of via transition, targeting an improvement of signal integrity quality. The analysis focused on the S-parameter of return loss, insertion loss and eye diagram covering both time and frequency domain result in 14.8%, 20.8% and 15.6% improvement in eye opening for PTH, Drill and Split via configurations respectively.