Equipment design for high precision thermal conductance measurement of thermal interface materials

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Dr. Szabó Péter Gábor
Department of Electron Devices

With the development of semiconductor devices the power density per unit area shows an increasing tendency. In order to avoid the overheating of electric circuits proper cooling solutions have to be applied.

The establishment of a good heat-conduction path between the chip and its ambient is nowadays one of the most important design aspects. Using thermally good conductive packaging materials the thermal resistance between the chip and the cooling surface of a packages as well as between a cold-plate and the ambient can be reduced, however the thermal interface material (TIM) layer between the cooling surface of the package and the cold-plate still may act as a thermal bottleneck. The development of better performing TIM-s requires measurement systems capable of characterizing their thermal conductivity values in an accurate and preferably quick way.

In my work I give an overview of the most commonly used TIM types and the methods applied for the characterization of their thermal conductivity, with special emphasize put on the current steady-state standard, the ASTM D5470 method. I present the operation principle and structure of the servo-motor based measurement system developed in the framework of my final year project. I explain based on which requirements each part of the system has been chosen, which calculations, measurements and simulations were performed to support my decision. Beside these I explain the operation of the software which controls the measurement system.

The ready equipment has been tested using commercially available thermal greases. I prove the repeatability of the results by measuring the same sample several times. The accuracy of the system is assessed by comparing measurement results taken by the high precision STATIM Static TIM Tester equipment.

The results are proven to be highly repeatable and the measured values are well in-line with those measured by the STATIM.


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