Numerical simulation of impedance discontinuities resulting from degradation of interconnections on printed circuit boards

A 3-D model was developed for numerically simulating the effect of solder joint cracking on impedance. Some initial reflectometry results are reported of a microstrip transmission line as a crack propagates through a solder joint. Observations are made on the information obtained when using low-pass vs. band-pass modes for reconstructing reflectometry data from frequency domain results. A qualitative comparison is made with experimental results on samples with a design which is similar to the model. On the basis of these observations, approaches for improving the model and future applications are discussed.