Application of x-ray microtomography for researching porosity of composite materials in power electronics

Background. Operating performance and reliability of power semiconductor devices (PSD) can be attributed to the quality of an electrically active semiconductor element, as well as to the properties of thermal compensator's (TC) material, which reduces thermomechanical stress in the device's design. TC, being one of the PSD's electrodes, also serves to remove the heat, generated during operation of the device. Researches, devoted to finding new materials providing a necessary range of TC functional characteristics, are of high relevance. Previous researches have found that promising TC materials can be composed of metal-composite materials (MCM). The most important parameter in determining the MCM TC's functional characteristics is the porosity of a composite material. Therefore, the objective of the paper is to examine X-ray microtomography possibilities to obtain data on distribution of porosity in the MCMs, used in PSD's TC. Materials and methods. The X-ray microtomography method was used to study the porosity of TC's material, made of a metal matrix composite AlSiC. The experiments were performed using an X-ray microtomograph SkyScan 1172. Results. The paper presents the method of analysis of porosity distribution in MCMs, based on mathematical treatment of the distribution function of microtomogram voxels in test samples in X-ray density. The authors carried out the research of microporosity distribution in PSD's temperature compensators, composed of MCM AlSiC. It has been found that the microporosity in the TC's central region is significantly higher than in its periphery, which can be attributed to insufficient impregnation of central regions in a porous MCM preform by a molten aluminum matrix alloy.