Application of the laser flash diffusivity method to thin high thermal conductivity materials

The evolution of semiconductor devices and the dramatic increases in the power dissipation per unit volume of ever smaller microelectronic devices means electronic packaging technologies must evolve to manage the dissipation of heat. One of the major issues is the development of new packaging materials optimised for heat management. Future packaging will incorporate layers with thermal diffusivities exceeding that of copper in thin, sub-millimetre foils. Metrology techniques are needed to measure the thermal diffusivity of these thin, thermally fast materials. As some new materials are developed only in the form of thin substrates the laser flash technique is limited in its application to these materials. This paper addresses the application of a nanosecond pulsed laser flash instrument to the measurement of thermal diffusivity of thin high thermal conductivity materials and the errors associated with the measurement. An experimental comparison is made with a laser flash instrument where the laser pulse is of higher energy but millisecond pulse duration.