The majority of electronic failures are thermo-mechanically related by thermally induced stresses and strains. The excessive difference in coefficients of thermal expansion between the components and the board cause a large enough strain in solder and embedded copper structures to induce a fatigue failure mode. In this paper we will present the solder fatigue failure mechanism and the PTH fatigue failure. The solder fatigue failure is more complicated due to the many solder materials and different solder shapes. One example of solder fatigue occurrence is a ball grid array (BGA) solder ball. The following figure shows a cross section of a solder ball with the corresponding finite element model. The predicted location of maximum strain corresponds to the same location of solder fatigue crack initiation.