Abstract
Pressureless liquid phase sintering process was adopted for the fabrication of diamond/Cu composites. After suitable surface treatment these composites were joined with AlN, Si, and Al2O3 substrates by silver, graphite, and epoxy gels. The results show that adding minor active Zr element to enhance the wettability between Cu and diamond, the composites with a high thermal conductivity of 608 W/mK and CTE of 6.4 ppm/K can be achieved by using 300 μm diamonds with the volume fraction of 50 vol%. One order of surface roughness can be reduced through attaching a Cu/Zr flake to the composites before sintering. Packages joined by the silver gel have best performance, reaching 210 W/mK; those joined by epoxy shows excellent tensile strength, larger than 8.34 MPa. The tensile strength of graphite gel is around 1 MPa, providing a suitable condition to observe the distribution of the gel on the fracture surface. In thermal cycle tests carried out at 200 °C with 150 cycles, it was found that Cu/Zr flake addition can postpone the degradation of thermal properties of the composites, and the alumina package joined by epoxy gel has good reliability. While in thermal cycle tests carried out at 80 °C with 1000 cycles, packages joined by silver gel shows great reliability in normal circumstances, showing great commercial potential.