Steady-state thermal conductivity measurements of AlN and SiC substrate materials

Measurements of thermal conductivity on conventional and newly developed electronic ceramics are presented as part of an effort to incorporate the new high-thermal-conductivity ceramics into microcircuit manufacturing. Motivated by large variations in values claimed by different vendors for ostensibly similar materials, a longitudinal bar apparatus was built to measure thermal conductivities of actual substrate materials on both an individual and a lot sampling basis. The values measured in this work are in general agreement with the manufactures' quoted values, with a few marked differences for certain AlN samples. The values measured using the longitudinal bar apparatus from room temperature to 80 degrees C on the different materials agree with both previously published data on similar materials and current measurements by other researchers. The longitudinal bar data for high-thermal-conductivity samples are completely consistent with the flash diffusivity results. Data on the AlN samples subjected to thick-film firing show no measurable change in thermal conductivity, indicating that the material is stable after repeated firings in 850 degrees C oxidizing atmospheres. The longitudinal bar apparatus appears to be operating as designed; measurements indicate that thermal resistances at the base and heater mounts are low enough not to affect the thermal conductivity measurements.<
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