Thermo-fatigue life evaluation of SnAgCu solder joints in flip chip assemblies

Thermal fatigue failure, due to the fracture of solder joints which was cased by the mismatch deformation, is frequently encountered in flip chip assemblies. Unfortunately, there is no widely accepted method to evaluate the reliability of solder joints, especially for lead-free solder joints, in such assemblies up to now. The constitutive models of double power law and the hyperbolic sine law were implemented to simulate the deformation of SnAgCu solder joints in flip chip assemblies in this paper. The accumulated creep strain and accumulated creep strain energy density of the solder joints were calculated, via finite element method, and were used to predict the thermal fatigue life of flip chip assemblies. The applicability of the above life prediction methods was evaluated through cross check of the present results with that of the literatures. It was found that the life of the FC assemblies could be estimated by the prediction of the life of the corner solder joints. The thermal fatigue life, estimated by accumulated creep strain energy density is closer to the test data than that of the life estimated by accumulated creep strain. The life predicated according to accumulated creep strain shows a slightly high value than that predicated according to accumulated creep strain energy density. The double power law constitutive equation results in higher predicted life.