Reliability evaluation of fatigue life for solder joints in chip components considering shape dispersion

This paper presents mining the worst thermal fatigue life of solder joints on chip components used in vehicle electronics. The authors proposed an isothermal fatigue test method using real size solder joints to get the fatigue properties. The Manson-Coffin´s law given by this method could improve the agreement between the simulation model and experimental results. Based upon the Manson-Coffin´s law and Miner´s law, the authors proposed a fatigue crack propagation simulation approach. By using this approach, the fatigue life of typical 36 cases with various solder shapes were examined. Thermal fatigue life to not only crack initiation but also crack propagation was evaluated by using the finite element method. When the crack propagates into a fillet of solder, the fatigue life drops to a lower value. Since there is an interaction between two solder joints on the chip component, asymmetrical structure also affects the fatigue life. It means that the shape of solder joints should be designed to control the failure mode. Considering scatter at 6¿ level, such kind of the worst cases will exist and should be considered in design stage.