Thermal stress analysis and optimization of BGA stacked solder joints under power cyclic loading

Based on ANSYS simulation software, a finite element model of BGA stacked solder joints was established. In order to analyze the effects of solder joint height and diameter and chip thickness on the thermal stress of solder joints under power cycling load, 17 sets of tests with 3-factor and 3-level parameter combinations were designed using the response surface method, and the regression equation of solder joint stress with these 3 factors was established. A genetic algorithm based regression equation was used to find the optimal combination of parameter levels for the stacked solder joint package structure and verified the correctness. The results show that: the thermal stress distribution of the stacked solder joints under power cycling load is not uniform, the key solder joints are in the four corner solder joints, and the maximum stress is in the contact area between the solder joints and the chip; by the genetic algorithm to find the best, the structural parameters of the lowest stress level combination of the stacked solder joints are: solder joint height 0.355mm, solder joint diameter 0.464mm, chip thickness 0.835mm; It is also verified through simulation that the optimal level combination of the structural parameters of the solder joints, the thermal stress of the solder joints is significantly reduced, and the structural optimization of the BGA stacked solder joints is achieved.