Application of photoacoustic method and evolutionary algorithm for determination of thermal properties of layered structure

Abstract
In this paper, a method of determination of thermal parameters in a multilayer structure is presented. The main purpose of the method is to evaluate the quotient of thermal effusivities as well as the quotient of thickness and square root of thermal diffusivity d for each layer. The method developed consists in comparison of measured frequency characteristics of thermal impedance with theoretical ones. The measurements of characteristics were carried out with the help of a photoacoustic microscope. The transmission line matrix (TLM) was used for determination of the temperature response of the structure for harmonic excitation. A method based on an evolutionary algorithm was applied to evaluate thermal properties of examined structure. The aim of this method was to find the best fitness of thermal impedance of the model to the measured impedance of the examined object. In the paper, results of investigation of layered structure silicon-aluminium-molybdenum are presented. The method presented can be applied to determine thermal properties of multilayer structures such as semiconductor-substrate structures, metal-ceramics structures.