Study on the Thermal Properties and Reliability of Liquid Metal/Copper-Coated Diamond Composite Thermal Interface Materials

As the integration and power density of high-power electronic devices continue to rise, efficient thermal management has become a key challenge in ensuring their performance and reliability. In this study, liquid metal gallium was used as the matrix and copper-coated diamond (CCD) as the reinforcing phase. Using a mechanical mixing method, liquid metal/copper-coated diamond (LM-CCD) composite thermal interface materials with different filler contents (10–60 vol%) were prepared, and their microstructure, thermal conductivity, and high-temperature operational reliability were systematically investigated. The results showed that when the CCD content is 50 vol%, a complete, interconnecting thermal conduction network forms within the composite, with thermal conductivity peaking at 86.9 W/(m·K)—approximately three times that of pure gallium (~29 W/(m·K)). COMSOL Multiphysics 6.2 finite element simulations confirmed that the thermal conduction framework formed by high CCD content effectively reduces heat accumulation. However, high-temperature aging tests at 125 °C revealed a synergistic effect between the formation of the CuGa2 intermetallic compound (IMC) via interfacial reactions and oxidation reactions, resulting in microstructural degradation and a drop in thermal conductivity to approximately 49.3% of its initial value after 240 h. After 336 h of aging, the thermal conductivity decreased further to approximately 27 W/(m·K), indicating that the thermal conductivity enhancement provided by CCD had been lost under these accelerated aging conditions. In addition, actual CPU thermal testing has shown that, compared to commercial thermal paste (~5 W/(m·K)), the LM-CCD composite material can reduce the chip’s steady-state temperature by approximately 14 °C. This represents a 4 °C reduction compared to pure gallium. Through combined experimental and theoretical analyses, this study provides a basis for understanding the degradation mechanisms of liquid-metal thermal interface materials and for designing more reliable TIMs through interface modification or oxidation-resistant encapsulation.