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DIAGNOSTICS OF THERMOPHYSICAL PROPERTIES AND QUALITY CONTROL FOR DEVICES MADE OF HIGH THERMAL CONDUCTIVITY MATERIALS

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Subject of study. We propose detection method for potential defects in the structure of device made of materials with high thermal conductivity, and thermal conductivity determination by the method of contact-free noninvasive thermal-imaging macrography. Method. The principle of the method lies in the following: local heating and cooling of the device is carried out, the temperature fields of its surfaces are measured. This method is based on the analysis of temperature fields. Main results. The study on the presence of defects in highly heat conductive material based on silicon carbide with diamond filling was performed. The experimental setup was developed. It consists of a measuring cell, a test sample with a cooler installed on the one edge and electric heater on the opposite edge. The test samples had the form of silicon carbide plates with diamond filling, each of 120×60 mm in size and 2 mm in thickness. Thermal imaging of samples was carried out. The samples heating range varied from 10 to 90 °С. The test samples were in radiation-convective heat exchange with the environment on both sides. Initially, it was unknown which of the samples has a defect. The thermograms with thermal imaging results were obtained. The analysis of the obtained thermograms was carried out; the temperature distribution on the samples was compared. As a result of this comparison, both the sample with a defect in the form of a crack (a stepwise temperature change in the crack region was observed), and the sample without defect (with the uniform temperature gradient) were determined. Practical relevance. The proposed method of thermal imaging is non-destructive, contactless and allows for the quality control of electronic devices made of highly conductive materials, as well as their thermal properties. The thermal conductivity of the sample can be determined by the temperature gradient and the measured heat flux values. This method is used for research of high-heat ceramic materials (with thermal conductivity above 200 W/(m·K)). Measurements were carried out in steady state behavior. At thermal imaging it is necessary to provide a high radiation coefficient of test sample observed surface. For this purpose, the surface is covered with paint with a radiation coefficient not less than 0.95 or the surface is covered with soot.

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