Investigation on enhancing the thermal conductance of gallium-based thermal interface materials using chromium-coated diamond particles

The focus of this paper is how to efficiently enhance the thermal conductance of gallium-based thermal interface materials (TIMs) and greatly avoid the excessive consumption of liquid metal during its application. Highly heat-conducting diamond particles are selected as the reinforced additives for pure gallium on account of their mature technology of surface metallization. To improve the interface combination status between those inorganic fillers and liquid metal matrix, chromium transition layer is deposited on the surfaces of diamond particles by magnetron sputtering method. The phase composition of cladding layer on diamond particles is analyzed by transmission electron microscopy combined with focused ion beam technology. To measure the thermal conductivity of gallium-based TIM filled with chromium-coated diamond particles, a specific three-layer structure sample is made for laser flash analysis and the corresponding theoretical fitting model is deduced subsequently. After performing iterative solution through programming, our results present that 47 wt% addition of chromium-coated diamond particles can dramatically increase the thermal conductivity of pure gallium from 29.3 to 112.5 W/(m·K) at room temperature. And fortunately, it has not yet been observed that the chromium coating is over consumed by liquid metal or the thermal conductivity of composite seriously degrades after thermal aging treatment at 80 °C for 192 h, strongly indicating that chromium could be used as the diffusion barrier layer for heat-conducting particles and the metal substrates to maintain long-term reliable service of gallium-based TIMs.