Micro-and Nano-Scopic Wave Theoretical Approach to Thermal Contact Resistance of Solid Interfaces

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Thermal contact resistance between two solid surfaces is one of the most important factors in thermal design and safety control in industrial devices. It is necessary not only to perform a basic research on clarification of thermal contact resistance phenomena systematically in the basis of thermal physics theory and wave theory, but also to develop a in-process non-contact diagnosis technique to diagnose transient phenomena of thermal contact resistance. In 2002-2003, we have studied the following two researches from this point of view :First, we have performed an experimental study to examine a diagnosis technique to diagnose thermal contact resistance from outside in-processly and non-contactly. Since microgeometry of contact interface changes at every moment corresponding with applied pressure to the surface system and elastic/plastic deformation of crystal structure, it becomes important to develop a technique to estimate contact states between two solid surfaces. We have applied … More the ultrasonic wave inspection technique to this purpose. In this experimental study, macro-scopic fundamental experiments to measure true contact areas of metal-metal (brass-SKD61 tool steel) contact interfaces, ultrasonic wave reflection and transmission in the contact interfaces and heat transmission crossing the contact interfaces, were performed. Relationships among three physical quantities, that is, (ultrasonic wave reflectance and transmittance) -(thermal contact resistance or thermal contact conductance) -(true contact areas), are clarified quantitatively throughout a parameter of applied pressure.Second, we have performed a series of molecular dynamics simulations to clarify microscopic mechanism of thermal contact resistance phenomena. Thermal contact resistance existing at an interface of two homogeneous crystal atomic layers in MEMS systems is called 'interface thermal resistance'. To investigate its detailed mechanism, damping propagation of elastics waves crossing an interface between two model crystals with different particle mass and a silicate film on silicon substrate were calculated. We have newly developed a lattice vibration analysis with wavelet transform technique, and have shown that propagation of elastic waves is hindered by the atomic interface. The obtained lifetime of the lattice vibration is found to be dependent on its frequency. With the density of states, the speed of elastic waves, and the lifetime combined, the interfacial thermal resistance was estimated. Less