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 AgZn3 phase was compressed and moved into the solder side when competed with the Cu5Zn8 phase, relieved the Kirkendall voids, and enhanced the connection of joints. Besides, the electrical resistivity could maintain at a competitive level of $9~\mu \Omega \cdot {\mathrm {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.