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Influence of the bottom surface condition on the AC temperature of a microheater on a polyimide substrate
Chang-Ui Jeon, Ho-Sung Kim and Dong-Wook Oh
The bi-directional 3ω method can be utilized to analyze of samples with thermal conductivity below 1 W·m-1·K-1. In this case, the higher thermal resistance of the 3ω sensor substrate and lower frequency conditions enhance measurement sensitivity and accuracy, necessitating different experimental conditions compared to conventional thermal analysis of thin films or solid substrates. However, low-frequency temperature oscillations from the microheater can have a thermal penetration depth similar to the thickness of the 3ω sensor substrate. This variation can influence the signals based on the sensor’s bottom conditions, significantly affecting the uncertainty of the measurement results. This study analyzes the 3w signals based on different bottom conditions of a microheater deposited on a 250 μm thick polyimide film used as a 3ω sensor. Measurements were conducted with the sensor placed directly on a stainless-steel stage without a thermal interfacial material, with silver paste applied between the sensor and the stage, on a 7 mm thick PDMS block, and suspended in the vacuum. The measurement results were compared with theoretical values to calculate the thermal contact resistance between the substrate and the bottom conditions.
Keywords: 3ω method, thermal contact resistance, thermal penetration depth, bi-directional measurement
DOI: 10.32908/hthp.v54.1889