Research On Solder Joint Shape And Residual Stress Of Solder Balls In The Process Of Reflow

Although the next generation of wireless equipment will integrate more functionsand needs better storage capacity, the mobile device producers still wish they stayunchanged in size. So saving space is getting more and more important. PoP provides aperfect package solution for hand-held mobile devices, such as digital cameras, PDAand MP3players. But a lot of questions remain unsolved in PoP producing process,such as low yield rate, the calculation of service time and etc..In this paper, the force state of the melted BGA balls in the process of reflow wasanalyzed, the Y-L(Young-Laplace) equation with volume constraint was established.The Y-L(Young-Laplace) equation was solved by numerical method, and the shape ofthe melted BGA balls were achieved. The shape could make preparations for the solidmodeling in ANSYS, and could also be used to determine whether the weld is good ornot. The residual stress of the solid balls was researched. With the finite elementanalysis software ANSYS, the stress concentration of the solids was researched,providing stress data for the study on the service time of PoP devices.