Finite element analysis of underfill effect on the CBGA package reliability under thermal cycling

Thermal cycling is one of the main failure factors of electronic devices, especially for CBGA packaging. The large difference in CTE between interconnect materials often results in fracture or fatigue failure of solder joints. Finite element simulation is an efficient method to analyze the critical locations of joints under various conditions such as thermal cycling reliability, and make corresponding optimizations for them. However, due to the modeling accuracy and the prediction differences of life prediction models, it is difficult to ensure the accuracy of simulation results. This work takes a high-precision simulation to analyze the failure process of solder joints of CBGA devices under thermal cycling and the thermal cycling reliability of packages with and without underfill are compared. The accuracy of the simulation is well verified by the experiment, and the life prediction error is within 5%. Final results show that the reliability of CBGA devices has been significantly improved by adding underfill.