AIN is a high thermal conductivity material and has received much interest in the electronics industry because of the need for smaller and more reliable integrated circuits and the need for higher voltage devices for power applications. Conventionally, AIN is fabricated by hot pressing, hot isostatic pressing and sometimes, pressureless sintering with post heat treatment. All these processes require high processing temperature and long processing time. The use of microwave energy as an alternative to conventional heating methods shows great promise.
Microwave heating is instantaneous, selective, and volumetric.
In addition, microwave sintering has been shown to have the potential of processing materials with improved properties over those conventionally processed. In this work, we report results of high thermal conductivity AIN sintered by a pressureless microwave process at 1820 o C for 60 minutes. The effect of sintering time on phase composition, thermal conductivity, and densification behavior was investigated. Microstructure studies and lattice parameter determination showed that thermal conductivity increases with increasing sintering time. We believe that this is primarily due to a decrease in oxygen content in the AIN lattice as more of the secondary phase forms in the grain junctions and getters oxygen.