Effects of Au/Ni coating thickness on enhancing the properties of InPb/MoCu solder joints in microwave modules

Deep understanding of and effective improvement in interconnect performance are of great significance for developing miniaturized and high-performance microwave modules. Herein, the effects of Au/Ni coating thickness on the performance of InPb interconnect solder joints were investigated by the high-temperature storage experiment. At normal Au/Ni joints, the AuIn2 intermetallic compound (IMC) particles bordered on each other, attributing to form a “closed zone” where the diffusion rate of In atoms was faster than that of Au atoms and there was a net flux. Here, the vacancies in the “closed zone” were merged in reaction to form Kirkendall voids. However, the “closed zone” inside the thin Au/Ni joints could be greatly reduced, and thus the generation of voids was significantly suppressed. The diffusion coefficient of AuIn2 IMCs was reduced by 22.34% at the thin Au/Ni joints compared with the normal Au/Ni joints. After aging for 168 h, the shear strength of the thin Au/Ni joints was increased by 25.10% compared with the other one. Therefore, the thin Au/Ni coating could enhance the long-term performance of solder joints in microwave modules and meet the development requirements of microwave module miniaturization.