Joint Interface Microstructure Analysis of Gallium-based Thermal Interface Material During Reflow

Thermal interface materials (TIMs), which are recently being used in high-power and new-generation materials, improve thermal stability at high temperatures because of the formation of intermetallic compounds. In this study, Cu-type Ga-based TIM solder has been selected to investigate the interface reaction of Ga-based thermal interface materials after curing, annealing, and reflow. During the curing process, liquid Ga diffuses through the X-alloy and reacts with Cu, resulting in the formation of the CuGa₂ phase. With the increase of annealing time, the area fraction of CuGa₂ and Cu₉Ga₄ decreases by 38% and increases by 44% because of the further diffusion of Cu into Ga, respectively. During reflow, the diffusion of Cu atoms into Ga leads to the formation of the solid solution of Cu and Ga. Meanwhile, the melted X-alloy reacts with Cu and forms Cu₆X₅.