Influence of Ag Layer on Microstructural Evolution and Joining Properties With Zn Foil for Power Electronics

Solid diffusion bonding of the copper-zinc system is preliminarily investigated as a possible bonding solution for power modules. This article proposed a method of bonding Zn foil on substrate-plated Ag to obtain the solder joints. The formation and transformation of intermetallic compounds (IMCs) in Cu-Zn and Ag-Zn joints were investigated. The results showed that the AgZn ₃ phase was compressed and moved into the solder side when competed with the Cu ₅ Zn ₈ phase, relieved the Kirkendall voids, and enhanced the connection of joints. Besides, the electrical resistivity could maintain at a competitive level of 9 μΩ · cm, and the shear strength reached 43-75 MPa. These properties were also appreciated even after the aging test. The deformation behaviors of different IMCs were tested by nanoindentation. This work provides a potential alternative to high-temperature solders used for high-power-density electronic packaging applications.