Microstructure Evolution and Interfacial Reaction of Cu/SAC305/Cu and Co-P/SAC305/Cu Solder Joints under High Current Density

Abstract

The size of solder joints in electronic packaging is gradually decreasing, which directly leads to a sharp increase in the current density experienced by the solder joints. Therefore, it is of great significance to study the effect of electromigration on the interface of the lead-free solder. In this paper, the effect of electromigration on the microstructure of Cu UBM and Co-P UBM solder joints was compared. By comparing the morphological changes of CoSn3 and Cu6Sn5 at the interface, combined with the calculation of the thickness of the intermetallic compound, it was found that the consumption rate of Co-P UBM in the solder joint was much lower than that of the Cu substrate. Moreover, when the Co-P UBM is completely consumed, the consumption rate of the Cu substrate is also significantly reduced.