Observation of Dislocations in Aluminum Nitride Material Powder and Sintered Body and Mechanism of Dislocation Formation

Abstract

Aluminum nitride is used for the quick removal of exothermic heat from MPU (Micro Processing Unit) used in computers and from the power module for application to hybrid cars. It has high thermal conductivity, but this property varies with method of manufacturing material powder. Thermal conductivity of sintered body from direct nitrided powder is lower than that of sintered body from reduction nitrided powder. The decreasing of thermal conductivity caused by direct nitrided powder was larger than that of impurities in raw powder as oxygen and metal. Thus, the direct nitrided powder is thought to have another mechanism of the decreasing of thermal conductivity of AlN sintered body. We found that sintered body from direct nitrided powder has many dislocations in grains. These dislocations are thought to be the cause of the decreasing of thermal conductivity. In addition, we found that dislocations occurred in crashing process and occurred at the time of crystal breaking within 300 μm from cracks.