Design And Experimental Study Of Thermal Conductivity Measuring Instrument For Thermal Interface Materials

There are multiple contact interfaces in the heat dissipation process of electronic system,and the contact thermal resistance generated affects the heat transfer between the interfaces.At present,filling the interface with thermal interface material is a common method to reduce the interface thermal resistance.Therefore,the study of thermal conductivity of thermal interface materials is of great significance to the use and promotion of materials.In this paper,according to the ASTM D5470 standard test method for heat transfer characteristics of thermal and electrical insulation interface materials,a thermal conductivity measurement device for thermal interface materials based on the steady-state method was built.The thermal interface materials of well-known brands at home and abroad were selected as experimental measurement samples to measure the thermal conductivity of the materials and the thermal resistance between the interfaces.The experimental results were compared with relevant literatures to verify the accuracy of the device in measuring different types of thermal interface materials.On this basis,the variation trend of thermal conductivity of thermal interface material with temperature and loading pressure was experimentally studied,and the uncertainty of test results under various working conditions was calculated and analyzed.Finally,a numerical model was built with COMSOL Multiphysicis 5.5 software.The effects of thermal conductivity,diameter of the metering rod,thickness of insulation layer and spacing of platinum resistors on the heat loss at the edge of the device and heat flow uniformity at the interface were discussed,which could provide a reference for further improvement of the experimental device.The main work completed in this paper is as follows:1.Summarizes several methods of measuring thermal conductivity and the measurement principle of ASTM D5470 standard,and summarizes the current research status of thermal interface material testing systems at home and abroad.2.According to ASTM D5470 standard,a thermal interface material thermal performance test system was built,suitable pressure sensors,displacement sensors,platinum resistance and other measuring elements were selected,and a cavity-type cooling unit was designed to enhance the heat dissipation effect of the device to meet greater temperature differences.Test conditions.3.Using the test device built in this article,various types of thermal interface materials were tested,and the experimental results were compared with related literature to verify the accuracy of the device in measuring various types of materials.4.In this paper,the influence of sample temperature and interfacial loading pressure on the thermal conductivity and interfacial thermal resistance of thermal interface materials was studied,and the change of the uncertainty of measurement results was explored under various test conditions.The results show that the interfacial thermal resistance decreases with the increase of loading pressure.The thermal conductivity of thermal conductive film decreases with the increase of temperature.The uncertainty of measurement results is different for different types of thermal interface materials.5.In order to explore the influence of heat loss and non-uniformity in the core measurement components on the results,a three-dimensional experimental model was established using COMSOL Multiphysicis 5.5 software to numerically simulate the temperature field inside the system.The results show that the edge heat loss and uneven heat flow of the device are affected by many factors;when the thermal insulation material with a thermal resistance value of 50 m~2·K/W is used,the radius of the metering rod is more than 15mm,and the thermal conductivity of the material is higher than 200W/m·K,the edge heat loss can be reduced to 1%,which is approximately regarded as no heat loss at the edge;when the distance between the platinum resistors is greater than 15mm,the temperature measurement platinum resistor with a probe diameter of less than 4mm can approximately ignore the influence of the temperature gradient.