EMC ’ 09 / Kyoto Equivalent Characteristic Impedance and Propagation Constant for Multi-Layer Via Structures

Via structures in multi-layer printed circuit boards (PCBs) and packages are studied using an equivalent transmission line model. Thus, transmission line theories, such as characteristic impedance and propagation constant, can be used to characterize the performance of via structures in a signal path. The closed-form expressions of R, L, G, C parameters of the equivalent transmission line model are derived based on a physics-based via circuit model with parallel-plane impedances and via-plate capacitances. Effects of geometrical parameters on via equivalent characteristic impedance are studied in the paper as well. The proposed method provides a straightforward approach to design via structures for better signal integrity.