Effects of Surface Diffusion and Solder Volume on Porous-Type Cu3Sn in Cu/Sn/Cu Microjoints

High-density interconnection technology is critical for semiconductor packages, which require high speed and multifunctional demands. The shrinkage of solder volume is needed for the miniaturization of devices. Fewer studies investigate using Cu3Sn than Cu6Sn5 in large solder joints. However, Cu3Sn has a significant and critical effect on microjoints. Cu6Sn5 can transform completely to Cu3Sn, which may cause unexpected problems in microjoints. The interfacial reactions in large and small solder joints are different. Porous-type Cu3Sn is an unusual structure at the interface. In this study, we utilize the transient liquid-phase bonding (TLP) process on microbumps to drive the transformation of Cu6Sn5 to Cu3Sn. Porous-type Cu3Sn is loose and unfavorable for joint strength. High-temperature bonding, microbumps and flux residues induce porous structure formation.補正完