High‐Temperature Skin Softening Materials Overcoming the Trade‐Off between Thermal Conductivity and Thermal Contact Resistance

Abstract

heat-dissipation structures, such as fins and micro/nanochannels, have been designed to efficiently dissipate heat from heat sources. [4][5][6] However, the inevitable gap between the heat source and heat exchanger results in thermal contact resistance (R c ), deteriorating heat dissipation performance. [7,8] The R c can be decreased by filling the gap with a thermal interface material (TIM). [1,7] A variety of different TIMs are available including thermal greases, adhesives, solders, and pads. [9] The pad-type TIM is a pre-formed thermally conductive film which can be compressed between the heat source and heat sink. This is removable which is advantageous for future disassembly and reassembly of the heat sink.The TIM can be classified based on directionality. [10] An anisotropic TIM, such as a graphite sheet, provides a high thermal conductivity (κ) in the aligned direction (≈1500 W m −1 K −1 ), but the κ in the perpendicular direction is significantly lower (≈5 W m −1 K −1 ). [11] Directional heat manipulation has been actively investigated using aligned hexagonal boron nitride platelets, [12] thermal metamaterials, [13,14] and aperiodic superlattice structures. [15,16] These technologies have potential applications in anisotropic TIMs. An isotropic TIM provides a uniform κ in all directions and can be synthesized by dispersing randomly-oriented thermally conductive fillers in a polymer matrix. [10,17,18] The κ of commercial isotropic TIMs is typically small (≈10 W m −1 K −1 ). Various types of fillers, such as carbon nanotubes, graphene, boron nitrides, metal nanoparticles (NPs), and ceramic particles, have been actively investigated to enhance κ. [10,17,[19][20][21][22] Polyurethane, epoxy (EP), and silicone rubber have been employed as a matrix to achieve high compressibility and conformability. [10,17,19,23] In this study, pad-type isotropic polymeric TIMs are primarily analyzed.Another important parameter of TIMs, in addition to κ, is thermal resistance. [24] The total thermal resistance (R t ) is composed of the specimen thermal resistance (R s = l/κ, l = specimen thickness) and R c . In order to decrease R s , the κ of TIMs can be increased by increasing filler concentration. However, the high filler concentration also increases elastic modulus (E), or decreases softness, making the conformal contact with a matingThe ORCID identification number(s) for the author(s) of this article can be found under

Covalently Functionalized Leakage‐Free Healable Phase‐Change Interface Materials with Extraordinary High‐Thermal Conductivity and Low‐Thermal Resistance

“…This enhances conformality at the mating surface that is advantageous for TIM applications. [ 5 ] The stability of the OP‐Ag‐nAgMWNT is also good. The cross‐sectional SEM and energy‐dispersive X‐ray (EDX) mapping images of the OP‐Ag‐nAgMWNT and OD‐Ag‐nAgMWNT, before and after heating at 80 °C (2 h), are compared in Figure S7 (Supporting Information).…”

Performance of Thermal Interface Materials

“…The thermal pastes excel due to their conformability, and are low in cost and simple in the installation. The skin‐core polymer‐based TIM [ 59 ] is particularly attractive for gap filling and is lower in material and installation cost than the CNT array. [ 29 ] The silicone‐based thermal pad commonly used for gap filling is not among the 12 top‐performing TIMs.…”

“…The thermal pastes and low‐melting metals constitute eight of the twelve top‐performing TIMs, and are lower in cost than the CNT array, graphene vertical array, and graphene/CNT aerogel. With consideration of a large bond line thickness, high thermal contact conductance and low cost, a solder‐graphite composite [ 52 ] and a skin‐core layered polymer‐matrix composite (with a soft thermoplastic skin for conformability enhancement) [ 59 ] are particularly attractive. The value for a silicone‐based thermal pad is 1.0 × 10 4 W m −2 K −1 , [ 33 ] which is lower than all of the values in Table 1.…”

Molecular dynamics simulation of thermal transport across a solid/liquid interface created by a meniscus

“…However, the morphology features of the contact between two different species separating a heat source and heat sinks result in the presence of interfacial thermal resistance (ITR), which lead to the degradation of the heat dissipation performance. 9 Meanwhile, understanding the ITR's properties enables for the modification of heat fluxes at the nanoscale by surface treatment 10,11 or external field. 12 From the characterization point of view, it should be noted that the experimental measurements of local temperatures fields, at the nanometer-scale, are difficult because heat flux may be transferred from the heat source to the sample and then further to the sensor through various thermal channels.…”

“…However, the morphology features of the contact between two different species separating a heat source and heat sinks result in the presence of interfacial thermal resistance (ITR), which lead to the degradation of the heat dissipation performance. 9 Meanwhile, understanding the ITR's properties enables for the modification of heat fluxes at the nanoscale by surface treatment 10,11 or external field. 12…”