Interfacial Microstructure Evolution of Indium Jointed with Different Surface Finishes after Thermal Treatments

High performance computing (HPC) products market is growing to meet current and future demands in business, government, engineering, and science. HPC system can process big data and perform complex calculation at high speeds, where the system also generates a lot of heat continuously. The accumulated heat needs to be managed to avoid affecting the performance and lifetime of HPC system. Therefore, a key design and development of HPC products is to achieve high thermal dissipation in electronic devices. The application of thermal interface materials (TIMs) has been a promising thermal dissipation solution for electronic devices. However, the thermal conductivities of current silicone-based TIMs have been insufficient for future products. Indium is a potential candidate for high heat dissipation needs, because the thermal conductivity of pure indium is around 86 W/mK, which is higher than most silicone-based TIMs. When indium has been applied as a metallic TIM and jointed with the metal of surface finish, there is an intermetallic compound (IMC) reaction at the interface of indium joint. The phase and microstructure of IMC depend on the conditions of thermal treatments and the type of surface finish. The interfacial condition of indium joint is the key to heat dissipation performance. Therefore, the interfacial mechanism of indium joints have been investigated by applying different surface finishes and various heat treatments in this study. In this paper, the interfacial reactions of indium jointed with different surface finishes (Au/Ni(V) and Au/Ni) have been investigated, respectively. For studying the interfacial microstructure evolution of the indium joints, they have been treated with different thermal treatments, including reflow process (with 245oC peak temperature) and high temperature storage tests (aging at 100oC, 125oC, and 150oC for 250 similar to 1000 hours). The interfacial morphologies of indium joint and the growth behaviors of IMC have been observed, and the interfacial IMC has been identified as Ni28In72 phase. For Au/Ni(V) surface finish, there is rock shaped IMC grains on the surface of Ni(V) layer, and the grain size of IMC increases with the increase of the reflow cycle. In Ni(V) layer, there is a significant In/Ni inter-diffusion reaction after different thermal treatments. For Au/Ni surface finish, the thickness of IMC increases with the increase of aging time and temperature, and the growth rate of IMC increases with the elevating storage temperature.