Reliability Analyse Of Flip Chip Solder Joint

With the rapid development of microelectronic packagings, the reliability of solder interconnection joint is one of the main issues in the development of microelectronic packagings and assembly technology. Solder joint shape is the critical factor that influences the reliability of solder joints. By hanging the shape of solder joint, its reliability may be enhanced significantly.In this paper, the distribution characteristics of the stress and strain in the elastic region of solder joints are derived and analysis of solder joints subjected to thermal cycle loads is complex because the plasticity and the viscosity has to be considered, he interaction between of solders joints. Thus, it is difficult to obtain the accurate distribution characteristics of the stress and strain in solder joints. Finite element method is used to analyze the reliability of solder joint.Some viscoplastic constitutive models of SnPb solders are analyzed in this paper. Then the Anand model which is an unified viscoplastic constitutive model is chosen. The Anand model shows better performance for the distribution characteristics of the stress and strain in solder joints under thermal cycle loads. Nonlinear finite element and the Anand model are used to solve the viscoplastic problem. The process is derived in details.The mechanical performance of SnPb solders is analyzed using the finite element method and Anand model and the distribution characteristics of the stress and strain in solder joints under thermal cycle loads are given. Thermal fatigue life of solder joints is predicted using the Coffin-Manson's empirical modified formula. Reliability of the solder joints with different structural parameters and shapes is compared. It can be found that the thermal fatigue life of solder joints increases with the increasing of its height and the diameter. The height of solder joints has the more important effect on thermal fatigue life than the diameter. The tiny concave solder joint has the longest thermal fatigue life by the shape optimization of solder joints.