| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 94 === Heat conduction in multi-layer thin films is a critical issue in the design of electronic devices and packages. Normally a thermal resistance offered to heat conduction by a uniform layer of a film is directly proportional to its thickness. When two materials having different thermal conductivities are in mechanical contact, an additional contact thermal resistance occurs between the two layers since perfect contact at the interface occurs only at a limited number of spots and the void found elsewhere between the layers is filled with air. It is possible that the intrinsic thermal resistance of a thin film is significant smaller than the contact resistance at the interface. In the present study, the effect of the contact resistance on the transient heat conduction characteristic of a multi-layer thin film system is first investigated. The multi-layer thin film system severs as a model for a thin film thermal detector. It is found that the contact resistance between thin film layers can change the temperature response characteristics of the thermal detector. For a constant heat flux input, the temperature response between the active junction layer and reference junction layer increases due to contact resistance. To better understand the roughness effect on the thermal contact resistance, a simple geometric configuration is proposed to model the roughness region, and the effect of various geometric scales of the roughness region on the contact resistance is studied using a finite element program and a thermal network model. The calculated thermal resistance values from both methods show similar trends, but the one-dimensional thermal network model always gives overpredicted values due to its neglectance of the two- dimensional conduction effect. The effect of applying thermal grease in the roughness region on the thermal resistance is also studied.
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