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Modeling of Thermal Joint Resistance of Polymer-Metal Rough Interfaces

M. Bahrami, M. M. Yovanovich, E. E. Marotta

2004
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Heat Transfer, Volume 2
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unpublished

A compact analytical model is developed for predicting thermal joint resistance of rough polymer-metal interfaces in a vacuum. The joint resistance includes two components: i) bulk resistance of the polymer and ii) micro, constriction/spreading resistance of the microcontacts at the interface. Performing a deformation analysis, it is shown that the deformation mode of the polymer asperities is plastic. The required input parameters of the model can be measured in the laboratory and/or found in
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... ry and/or found in the open literature. It is observed that the thermophysical properties of the polymer control the thermal joint resistance and the metallic body properties have a second order effect on the thermal joint resistance. A non-dimensional parameter, i.e., ratio of microcontacts over bulk thermal resistances, is proposed as a criterion to specify the relative importance of the microcontacts thermal resistance. The present model is compared with more than 140 experimental data points collected for a selected number of polymers and showed good agreement. Nomenclature A = area, m 2 a s = radius of microcontacts, m b L = specimen radius, m E = Young's modulus, P a E 0 = effective elastic modulus, P a F = applied load, N H mic = microhardness, P a H e = elastic microhardness, P a h = thermal conductance, W/m 2 K k = thermal conductivity, W/mK k * = non-dimensional thermal conductivity, ≡ k p /k s m = combined mean absolute surface slope, [−] n s = number of microcontacts P = apparent contact pressure, P a P * = non-dimensional pressure, ≡ P/H mic Q = heat flow rate, W R = thermal resistance, K/W T = temperature, K t = thickness of polymer specimen, m TCR = thermal contact resistance TIM = thermal interface material Y = mean surface plane separation, m Greek γ = plasticity index≡ H mic /E 0 m λ = non-dimensional separation≡ Y/ √ 2σ σ = combined RMS surface roughness, m Θ = non-dimensional parameter ≡ R s /R b υ = Poisson's ratio Subscripts 0 = reference value 1, 2 = solid 1, 2 a = apparent b = bulk c = contact e = elastic FM = Fuller Marotta g = glass temperature j = joint mic = micro p = plastic r = real s = solid, micro

doi:10.1115/imece2004-60131
fatcat:efky7pha4bgetmef4r5ppomy64