Effect of nano-intermetallic compound on creep properties and 8-Sn grain recrystallization of Cu/Sn-Ag-Cu/Ni solder joints

In this paper, the nanoindentation method was used to study the creep properties of nano-intermetallic compound (nano-IMC) mixed solder joints. Furthermore, the microstructure evolution, crack initiation, and 8-Sn grain recrystallization during thermal cycles were discussed. The results revealed that the addition of nano-IMC increased the nano-(Cu,Ni)6Sn5 content in the mixed solder joints after reflow, which increased the stress index, reduced the stress sensitivity index, and improved the creep resistance. During thermal cycles, cracks appeared at the corner of solder joints and substrate under cyclic stress, expanding along the solder/IMC interface with the increase in thermal cycles. Compared with the mixed solder joints, the recrystallization of SAC305 solder joints aggravated during thermal cycles. This is because of the high nano-(Cu,Ni)6Sn5 content in the mixed solder joints, which can effectively pin dislocations and inhibit the dislocation slip and rotation of 8-Sn grains, thereby preventing the recrystallization of 8-Sn grains. This improved the reliability of the mixed solder joints.

Automated summary

In this paper, the creep properties of nano-intermetallic compound (nano-IMC) mixed solder joints were studied using the nanoindentation method. The microstructure evolution, crack initiation, and 8-Sn grain recrystallization during thermal cycles were discussed. The results showed that the addition of nano-IMC increased the nano-(Cu, Ni)6Sn5 content in the mixed solder joints, which improved the creep resistance.