Prediction of Fatigue Life Time and Optimization of PoP Solder Joints under Thermal Cycling Load

A PoP device model was established using finite element analysis (FEA) method to investigate solder joint reliability under thermal cycling load. Thermal stress was analyzed to identify critical solder joints according to the ANAND constitutive model, and the fatigue life of critical solder joints was calculated using the strain-based Coffin-Manson formula. The overall life of the PoP device was 708 cycles according to the shortest plank principle. The height of the top and bottom layer solder joints and the thickness of the ceramic substrate and the bottom layer substrate were selected as structural parameters. With the fatigue life as the target value, the Taguchi experimental method was employed to design nine experimental combinations with different parameter levels. The results indicate that fatigue life increases with higher solder joint heights and thicker ceramic substrates, but decreases with thicker bottom substrates. The optimal structural parameters are as follows: the top layer solder joints are 0.34 mm high, the bottom layer solder joints are 0.26 mm high, the ceramic substrate is 1.4 mm thick, and the bottom substrate is 0.5 mm thick. After optimization, the overall fatigue life of the PoP device reaches 1340 cycles. This research provides theoretical support for the design optimization of PoP devices and offers practical guidelines to enhance the thermal cycling reliability of electronic products.