Fundamental study of surface roughness dependence of thermal and electrical contact resistance
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For thermal management of electrical equipment, thermal contact resistance is one of the important parameters. However, thermal contact resistance is dependent on various factors, for example surface roughness, the contact pressure and the hardness of the material. Therefore, quantitative evaluation is difficult. Nowadays, CFD (Computational Fluid Dynamics) analysis is widely used in thermal design of electronics. However, unknown thermal contact resistance is always a problem for accurate temperature estimation. In this study, we examined surface roughness and material hardness dependence of thermal contact resistance and electrical contact resistance for simple estimation of thermal contact resistance. Measurement of thermal contact resistance takes a long time and electrical resistance measurement is much shorter. If thermal contact resistance can be estimated from electrical contact resistance, thermal contact resistance can be known in short time, and this method can support accurate CFD analysis. The materials to be measured are Al1070 and S45C, and three patterns (Ra = 0.2, 3.2, 12.5 μm) of surface roughness are examined. After the measurement of thermal and electrical contact resistance, we examined the ratio between electrical contact resistance and thermal contact resistance for the faster estimation of thermal contact resistance using the concept of Wiedemann-Franz law and Lorentz number like experimental constant.Keywords:
Contact resistance
Electrical contacts
Thermal contact
Interfacial thermal resistance
Wiedemann–Franz law
Contact area
The thermal contact interface resistance is a key technical problem in many fields,because of its features of the dependence of the multi-scale and micro-structure.With device or structure characteristic length scales becoming comparable to the mean free path and wavelength of heat carriers,classical Fouerier laws are no longer valid and new approach must be taken to develop.Based on diffusive and ballistic transport of the heat carrier,made a distinction between interface and sub-surface for interface layer,the transfer coefficient was solved using the radiation attenuation equations,and a diffusive-ballistic model was built up to predict the thermal contact interface layer resistance.The analysis shows that the diffusive-ballistic model is more precise comparing with the acoustic diffusive model in the higher temperature for the thermal contact interface layer resistance prediction of the thin film of YBCO on MgO substrate.It is useful to analyze the thermal contact interface layer resistance using the diffusive-ballistic model.
Interfacial thermal resistance
Ballistic conduction
Thermal contact
Interface (matter)
Contact resistance
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13 In this thesis, the phenomena of thermal contact resistance is examined from both an analytical and numerical standpoint. Strong emphasis is made on the differentiation between the macroscopic and microscopic mechanisms and their separate effects on the thermal resistance at the interface of two unbonded materials. Of particular interest is the interface between two dissimilar materials. A full analysis of the macroscopic influence of thermal strains on the deformations at the interface is presented. The dependence of interfacial thermal resistance on the direction of heat flow is explained. The theory of microscopic-based contact resistance is also reviewed. A computer code enabling coupled thermal-mechanical finite element analyses of models was developed to investigate the complex interplay between thermal strains, interface separation, and contact conductance. The program is used to examine past and current methods of experimentally determining thermal contact resistance. A unique procedure, based on observed interfacial phenomena, for experimentally measuring true thermal contact resistance is presented and numerically verified. Finally, the technology developed in this thesis is used to analyze some interface problems in electronic packages.
Thermal contact
Interface (matter)
Interfacial thermal resistance
Contact resistance
Thermal grease
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The study of the thermal contact resistance at the liquid–solid interface is an important subject of the heat transfer of phase change materials. In this work, a fractal model for predicting the thermal contact resistance at the liquid–solid interface is established by considering the self-affine fractal geometry of the rough surface. Based on the fractal characteristic of roughness structures, topographical and mechanical analyses have been conducted to identify the position of the liquid–solid interface and determine the thermal contact resistance at the interface. The relationship between contact parameters and the thermal contact resistance are studied. Based on the analytical predictive model for thermal contact resistance at the liquid–solid interface, the three-dimensional melting process of a nanoparticle-enhanced phase change material with different thermal contact resistances was simulated by using the finite volume method, and the enthalpy-porosity model is employed. The effects of thermal contact resistance between the composite phase change material and the heat source are investigated. It is found that the augmentation of thermal contact resistance decreases the melting and heat transfer rates and the influence of thermal contact resistance becomes more pronounced with a higher volume fraction of nanoparticles.
Interfacial thermal resistance
Contact resistance
Thermal contact
Thermal grease
Contact area
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Prediction of electrical and thermal contact resistance for pressed, nominally flat contacts is complicated by the large number of variables which influence contact formation. This is reflected in experimental results as a wide variation in contact resistances, spanning up to six orders of magnitude. A series of experiments were performed to observe the effects of oxidation and surface roughness on contact resistance. Electrical contact resistance and thermal contact conductance from 4 to 290 K on OFHC Cu contacts are reported. Electrical contact resistance was measured with a 4-wire DC technique. Thermal contact conductance was determined by steady-state longitudinal heat flow. Corrections for the bulk contribution ot the overall measured resistance were made, with the remaining resistance due solely to the presence of the contact.
Contact resistance
Electrical contacts
Thermal contact
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Single source reference on how applying thermal spreading and contact resistance can solve problems across a variety of engineering fields Thermal Spreading and Contact Resistance: Fundamentals and Applications offers comprehensive coverage of the key information that engineers need to know to understand thermal spreading and contact resistance, including numerous predictive models for determining thermal spreading resistance and contact conductance of mechanical joints and interfaces, plus detailed examples throughout the book. Written by two of the leading experts in the field, Thermal Spreading and Contact Resistance: Fundamentals and Applications includes information on: Contact conductance, mass transfer, transport from super-hydrophobic surfaces, droplet/surface phase change problems, and tribology applications such as sliding surfaces and roller bearings Heat transfer in micro-devices and thermal spreaders, orthotropic systems, and multi-source applications for electronics thermal management applications Fundamental principles, thermal spreading in isotropic half-space regions, circular flux tubes and disc spreaders, and rectangular flux channels and compound spreaders.
Contact resistance
Interfacial thermal resistance
Thermal contact
Thermal mass
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Enhancing the thermal conductivity of polymer composites could improve their performance in applications requiring fast heat dissipation. While significant progress has been made, a long-standing issue is the contact thermal resistance between the nanofillers, which could play a critical role in the composite thermal properties. Through systematic studies of contact thermal resistance between individual boron nitride nanotubes (BNNTs) of different diameters, with and without a poly(vinylpyrrolidone) (PVP) interlayer, we show that the contact thermal resistance between bare BNNTs is largely determined by reflection of ballistic phonons. Interestingly, it is found that a PVP interlayer can either enhance or reduce the contact thermal resistance, as a result of converting the ballistic phonon dominated transport into diffusion through the PVP layer. These results disclose a previously unrecognized physical picture of thermal transport at the contact between BNNTs, which provides insights into the design of high thermal conductivity BNNT–polymer composites.
Interfacial thermal resistance
Thermal contact
Contact resistance
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Citations (19)
Thermal rectification refers to the phenomenon that heat fluxes or equivalent thermal conductivities are different under the same temperature difference when temperature gradient directions are different. The nature of the thermal rectification is that the structure has different effective thermal conductivities in different directions. Most of previous studies focused on thermal rectification of temperature-dependent thermal conductivity materials or variable cross section area structure, and the effect of thermal contact resistance at the interface was investigated very rarely. In the present paper we present the analytical and finite element numerical solution of temperature field and thermal rectification ratios of a composite structure with variable cross section area and thermal conductivity under different interface thermal contact resistances. The prescribed temperature boundary condition is introduced by penalty method, and the temperature jump condition at the interface is implemented by the definition of thermal contact resistance directly. The nonlinear heat conduction problem caused by temperature-dependent thermal conductivity and interface thermal contact resistance is then solved with a direct iteration scheme. Comparisons between experimental results and the present theoretical and numerical results show the feasibility of the proposed model. Then parameter investigations are also conducted to reveal the effect of some key geometric and material parameters. Numerical results show that thermal contact resistance plays an important role in the temperature field and thermal rectification ratio of the two-segment thermal rectifier. With the increase of the length ratio, thermal ratification ratio increases first and decreases then, and the optimal length ratio varies with both thermal contact resistance and cross-section radius change rate of the two segments. In general, the existence of thermal contact resistance can increase the total thermal resistance of the rectifier and magnify the distinction of the heat flux in forward and reverse cases. However, if the thermal contact resistance is too large, this distinction will decrease and correspondingly the thermal rectification ratio becomes low. With the increase of the boundary temperature difference, thermal rectification ratio increases due to the effect of temperature-dependent thermal conductivity. In the present study, we propose a theoretical and numerical approach to designing and optimizing the length ratio, cross-section radius change rate, thermal conductivity, boundary temperature difference and interface thermal contact resistance to obtain the maximal thermal rectification ratio of a bi-segment thermal rectifier, as well as the manipulation of thermal flux in engineering applications.
Thermal contact
Interfacial thermal resistance
Thermal transmittance
Thermal grease
Thermal bridge
Temperature Gradient
Contact resistance
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The interfacial thermal resistance between two solid materials is usually obvious in thermal management technology, but there is still no way to eliminate it nor uniform measurement standard. When taking thermal measurements because the surface roughness of instrument probe and device package directly affects the interface morphology, the change of total thermal resistance caused by the thermal contact resistance (TCR) fluctuations disturbs the accuracy of internal thermal analysis of device. We prepared samples with different surface roughness and performed thermal measurements on them, compared with test under vacuum environment and the condition filled with thermal interface materials, respectively. We found the heat-transfer mechanism of interface. More importantly, it is shown that in the interval of surface roughness [Formula: see text], the TCR shows good consistency when filled with thermal interface materials. This result will help to improve the convenience of measurement for the accuracy of thermal measurement technology.
Interfacial thermal resistance
Thermal grease
Thermal contact
Interface (matter)
Thermal transfer
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Interfacial thermal resistance
Micrometer
Thermal conductivity measurement
Thermal contact
Microelectronics
Contact resistance
Laser flash analysis
Thermal effusivity
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For thermal management of electrical equipment, thermal contact resistance is one of the important parameters. However, thermal contact resistance is dependent on various factors, for example surface roughness, the contact pressure and the hardness of the material. Therefore, quantitative evaluation is difficult. Nowadays, CFD (Computational Fluid Dynamics) analysis is widely used in thermal design of electronics. However, unknown thermal contact resistance is always a problem for accurate temperature estimation. In this study, we examined surface roughness and material hardness dependence of thermal contact resistance and electrical contact resistance for simple estimation of thermal contact resistance. Measurement of thermal contact resistance takes a long time and electrical resistance measurement is much shorter. If thermal contact resistance can be estimated from electrical contact resistance, thermal contact resistance can be known in short time, and this method can support accurate CFD analysis. The materials to be measured are Al1070 and S45C, and three patterns (Ra = 0.2, 3.2, 12.5 μm) of surface roughness are examined. After the measurement of thermal and electrical contact resistance, we examined the ratio between electrical contact resistance and thermal contact resistance for the faster estimation of thermal contact resistance using the concept of Wiedemann-Franz law and Lorentz number like experimental constant.
Contact resistance
Electrical contacts
Thermal contact
Interfacial thermal resistance
Wiedemann–Franz law
Contact area
Cite
Citations (7)