Effects of electromigration on grain rotation behavior of SnAg solders

The requirement for smaller devices but with much greater performance leads to a boost in current density and damage caused by electromigration. Recently, some researches show that the grain orientation changes during current stressing. In this study, the solder of SnAg2.6 with 2 um-thick UBM layer of Ni and 20 um-thick copper pad is used. Electron Backscattered Diffraction (EBSD) is applied to investigate the grain orientation in the entire solder joint during electromigration. Semi-In-situ observations are to determine the rate of change on grain orientation of tin. We can analysis these data at the same time to understand the relationship between the rotation rate of tin grain orientations and the current density applied on it. The analysis for current density in solders is accomplished by finite element simulation result. So far, based on our preliminary result, there are obvious grain rotations when they are subjected to current stressing and detailed results will be presented in the conference.