Effect of Warpage on Solder Joint Fatigue Life by Influencing the Solder Joint Shape in BGA Packages

Warpage occurring during surface-mount assembly reflow processes may lead to severe solder bump reliability problems. In this research, a finite-element simulation analysis of the effect of warpage on SAC305 solder joint fatigue life in a plastic ball grid array (PBGA) package was carried out. Due to the warpage of the PBGA package, the heights and solidified shapes of solder joints located at different positions are different. First, a finite element model was established to obtain the warpage, and experimental measurements were conducted to verify the accuracy of the model. The shapes of all solder joints affected by the warpage were obtained through Surface Evolver software. Finally, a solder joint fatigue life prediction model, combining package warpage and solder joint shape, was established through finite element analysis. A model without considering warpage, which was assembled with uniformly height solder joints, was also established to calculate the fatigue life of solder joints under the same conditions. The effect of warpage on solder joint fatigue life can be revealed by comparing the results of the two models. The results show that taller solder joints have a longer fatigue life. Warpage changes the location of solder joints most susceptible to fatigue failure from the bottom near the corners of the package to the bottom near the corners of the die. Due to the existence of warpage, the fatigue life of critical solder joints is, on average, 20% less than the predicted result of the model without warpage.