Abstract
Minor-addition of Ti was added into matrix to improve the wettability between diamonds and Ag matrix in this study. Pressureless liquid phase sintering process was adopted for the fabrication of diamond/Ag composites. The optimum result achieved by using 300 μm diamonds with a diamond volume fraction of 60 vol%, composites with a high thermal conductivity of 788 W/m*K and CTE of 6.7 ppm/K can be achieved. Diamond composites fabricated by silver-flake sintering method with a stainless steel plate can reduce the surface roughness to 1.1 μm which is suitable for joining with commercial substrates and thermal conductivity of 749 W/m*K can be achieved. In this study, we used four different kinds of low melting point alloys (commercial Liquid Ultra Ga0.78In0.14Sn0.08, and homemade Ga0.76Sn0.24, In0.63Ga0.37, and Sn0.37In0.36Ga0.27) as thermal interface materials to join diamond composites with commercial substrates (aluminum nitride, silicon, sapphire). In the system of joining by In0.63Ga0.37, heat spreader joining with silicon can achieve highest thermal conductivity of 398 W/m*K. In thermal cycle tests carried out from 25 °C to 85 °C with 1000 cycles, the system of joining by Sn0.37In0.36Ga0.27 showed the best thermal performance, the groups of Sn0.37In0.36Ga0.27 can still maintain at least 80% of thermal conductivity.