Application of a llaser flash system to the determination of thermal conductivity of thin aluminium nitride substrates

A laser flash system which accurately and reproducibly evaluates the thermal diffusivity of AlN substrates as thin as 0.064 cm has been developed. This system consists of a Nd-glass laser with pulse duration of approximately 350 mu s, an InSb infrared detector, a storage oscilloscope, and associated amplification and filtering electronic circuitry. Half-rise-time values down to 0.5 ms can be measured and accurately corrected with the application of a modified finite pulsewidth correction. The accuracy of the system was evaluated by testing high-purity metal and graphite disks. Thermal conductivities of commercially available AlN thin substrates were measured. The results were compared with those of longitudinal bar and CO/sub 2/-laser flash techniques, and were found to be in good agreement within 10% and 5%, respectively.<>