Reliability evaluation of lead free solder joints subjected to multi-loads

The miniaturization and the high integration of electronic device parts were progressed by the advance in technology, and it leads the problems of warpage of high-integrated component during mounting processes. This kind mismatch would be released slowly after the components are assembled. Therefore, it is concerned that the deformation of the solder joints caused by the warpage should give some impact on the thermal fatigue reliability of solder joints, because the solder joints are subjected not only to the cyclic thermal mismatch but also to the considerable one direction bending load. This state is called as multi-loads in this study. The thermal cyclic fatigue reliability of solder joints had been studied by using analytical and heat cyclic testing approaches, and it is shown that the fatigue life can be assessed by Manson-Coffin's law. However, the reliability evaluation techniques for multi-loads problem have not been established. In this study, the relation between the fatigue reliability and the multi-loads conditions was studied and the BGA (Ball Grid Array) package was chosen as the target. The author proposed a new cyclic bending test method to achieve the different conditions of the multi-loads, and based upon the experimented and analytical results it was found that impact of the multi loads some cases neglected for could not be.