Characterizing Macroscopic Thermal Resistance Across Contacting Interfaces Through Local Understanding of Thermal Transp
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.485
Characterizing Macroscopic Thermal Resistance Across Contacting Interfaces Through Local Understanding of Thermal Transport Seshu Nimmala1, S. Aria Hosseini2, Jackson Harter3, Todd Palmer3, Eric Lenz1 and P. Alex Greaney2
1
Lam Research Corporation
2
Department of Material Science and Engineering, University of California — Riverside
3
School of Nuclear Science and Engineering, Oregon State University
ABSTRACT
Thermal resistance across the interface between touching surfaces is critical for many industrial applications. We developed a network model to predict the macroscopic thermal resistance of mechanically contacting surfaces. Contacting interfaces are fractally rough, with small islands of locally intimate contact separated by regions with a wider gas filled boundary gap. Heat flow across the interface is therefore heterogeneous and thus the contact model is based on a network of thermal resistors representing boundary resistance at local contacts and the access resistance for lateral transport to contacts. Molecular dynamics simulations have been performed to characterize boundary resistance of Silicon Alumina
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interfaces for testing the sensitivity of thermal resistance to contact opening. Boltzmann transport simulations of access resistance in Si are conducted in the ballistic transport regime.
INTRODUCTION Predicting the thermal resistance of mechanically contacting but unbonded interfaces is currently challenging as surfaces tend to be fractally rough below the micro or nanometer scale and so the true contact area is difficult to determine. Heat transport across a contacting interface is therefore heterogeneous and involves lateral flow of heat to regions in strong thermal contact. Moreover, depending on the temperature, surfaces possess adsorbate layers of water and other gases that will alter the effective global contact area and local transmission of heat. For this configuration, we propose that the flow of heat across a mechanically Figure 1. Schematic representation of an interface between two contacting surface could be mechanically contacting surfaces. We propose that macroscopic functionally represented as a network thermal boundary resistance may be represented with a resistor of random thermal resistors as is network abstraction of the interfacial heat flow. shown schematically in Fig. 1. Furthermore, we assert that if one can generate the library of resistances based on the contacting materials’ properties then one could use the network abstraction in a simple user tool that predicts the macroscopic thermal resistance between contacting surfaces based on the interfacial surface roughness. This would provide an efficient and scalable tool for process engineers and designer
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