Speakers
Description
TIMs are utilized as contact material between electronic components and the heat sink. The considerably increased power requirements and the continuing trend towards miniaturization in electronic devices lead to an increased performance and desire a suitable characterization of the behavior of TIMS. As a key component in the thermal management of electronic components, TIMs should have high electrical insulation properties and a low thermal resistance.
Selecting a best matched TIM for the specific application is a difficult task. Parameters like thermal resistance, electrical insulation, contact pressure dependency and price play an important role in TIMs selection. Data sheet specifications for thermal resistance are usually determined by the ASTM D5470 method. In this case, TIMs characterization is performed under highly favorable conditions (polished surfaces, excessive pressure conditions). However, these conditions differ from operating applications. This can lead to incorrect thermal design.
In this study, a fast method for characterization of the thermal resistance of TIMs under realistic operating conditions was investigated. A 3D printed test rig was built up to measure the thermal resistance of TIM samples at different contact pressures and heat flow rates. The heat source was uniformly distributed as well as locally applied which is typical for practical applications. Four commercially available TIMs were characterized: Elastomer, silicone, PCM and graphite foil. The measured temperatures were used to calculate the thermal resistance. The PCM sample showed the lowest resistance, the elastomer the highest. Applying a non-uniform heat source, the graphite foil could not demonstrate its benefit in terms of in-plane heat distribution. A comparison between measured values with the data-sheet showed deviations between ASTM method and typical operation conditions as investigated here. Using this method TIM materials and systems can be fast characterized and allows a rapid indication of the applicability of the desired TIM under relevant operation conditions.