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 949 W/mK and CTE of 6.7 ppm/K can be achieved. Diamond composites fabricated by silver-flake sintering method can reduce the surface roughness to 1.8 μm which is suitable for joining with commercial substrates and thermal conductivity of 805 W/ mK can be achieved. In this study, we used three different kinds of thermal interface materials (colloidal silver liquid, graphite gel, thermal resistant epoxy adhesive) to join diamond composites with commercial substrates (aluminum nitride, silicon, sapphire). In the system of joining by colloidal silver liquid, heat spreader joining with aluminum nitride can achieve high thermal conductivity of 259 W/mK. In thermal cycle tests carried out at 85°C with 1000 cycle, the groups of epoxy adhesive showed no decay in thermal conductivity, demonstrating the high reliability of electronic package produced in this study. While in the system of graphite gel, only the sapphire’s package can maintain 100% of thermal conductivity. Furthermore, the pressureless sintering is a simple technique that requires only low-cost equipment, making this cost-effective method attractive for metal matrix composite fabrication.