A Close Look on Voids in Solder Joints

A challenge for the power electronics industry is the reliability of solder joints [1] for automotive application due to the increasing performance requirements, especially in handling thermal and electrical environments. A known fact is that the presence of voids in the solder joints adversely affects thermal resistance due to decreased heat dissipation and a reduction of the cross-sectional area, which can lead to reliability effects [2]. In this work, the influence of different voids scenarios in solder joints via finite volume simulation on the example of a commercially available MOSFET was studied. Finite volume simulations (FloTHERM R) provide thermal transients that can be transferred into their corresponding structure function [3], [4]. Thus, changes in the heat path and the corresponding thermal resistance can be evaluated and interpreted. This work shows that voids implemented as random distributed, internal voids inside the solder joint can be correlated to the common approach of effective thermal conductivity [5].