Thermal Reliability and Environmental Testing of Advanced Metal Diamond Composites

Advanced diamond composites with matrix metal silver, copper and aluminum alloys were developed for heat sinks and base plates in high performance electronic packages. The reliability of these composites under extreme thermal and environmental conditions was investigated in the thermal cycling and pressure cooker tests. Thermal cycling tests on metal diamond composites were performed in a two chamber cycling oven between −55°C and +150°C for 1000 thermal cycles with 20 minutes storage time in each chamber. The effect of humidity and pressure was assessed from pressure cooker test at 121°C at 2 bar for 168 h. Thermal properties such as thermal diffusivity and specific heat were measured before and after the thermal cycling to observe any changes in thermal properties of the composites due to any possible interfacial degradation. The thermal properties of the composites did not decrease and the interfaces did not degrade after the thermal cycling tests in case of Ag-diamond composites. Al-diamond composites show a slight decrease of 5–8% in thermal diffusivity after thermal cycling. The thermal diffusivity of the Cu/Cr based diamond composite is unaltered before and after testing. The thermal diffusivity of Cu/Si diamond composites decreased by 43% at room temperature measured value. Al-diamond composites did not show any degradation during the pressure cooker tests although aluminum carbide is hygroscopic and deteriorates under moisture. Ag and Al-diamond composites survived the pressure cooker test. Cu/Si and Cu/Cr based diamond composites showed a slight change in coloration and a possible corrosion after the pressure cooker test.