Finite element analysis on the thermo-mechanical behavior of flip chip packages with Au stud bump and nonconductive paste

In this paper, we report the failure mode of a flip chip ball grid array package using Au stud bumps with non-conductive paste (NCP) as 1st level interconnect after temperature cycling (TC) testing. Finite element analysis (FEA) method was employed to investigate the failure mechanism and analyze the thermo-mechanical stress of the package. The highest stress location was calculated in the NCP near the die edge. The modeling results are consistent with the findings in the experiments, where cracks in NCP were found along the die edge. A parametric study was conducted to investigate the different NCP and mold compound (MC) properties on the package critical stress location. The results revealed that NCP material properties particularly the elastic-modulus, had a strong impact on the stress magnitude of the package as compared to MC. NCP material with a lower E-modulus and CTE, but a higher Tg gives a better TC performance