Joint‐Inspired Liquid and Thermal Conductive Interface for Designing Thermal Interface Materials with High Solid Filling yet Excellent Thixotropy

Abstract

For advanced thermal interface materials (TIMs), massive inorganic addition for high isotropic thermal conductivities conflicts with suitable rheological viscosity for low contact thermal resistance. Traditional strategies rarely resolve such a contradiction, and it remains an academic and industrial challenge. Herein, inspired by the structure and function of the bone joint, a best-of-both-worlds approach is reported that endows a standard polydimethylsiloxane/alumina (PDMS/Al 2 O 3 ) TIM with simultaneously enhanced rheological mobility and thermal conductivity. It is conducted by employing morphology-controllable gallium-based liquid metal (LM) to the surface of Al 2 O 3 by a scalable mechanochemical process. At the typical polymer-LM-Al 2 O 3 interface, LM droplets with low cohesive energy can release the freedom for macromolecular chain relaxation and reduce the viscosity, successfully allowing the high-loading TIMs (79 vol.%) to keep the thixotropic state and effectively reducing its contact thermal resistance with a copper substrate by 65%. At the same time, adjacent LMs merge to thermally bridge separate Al 2 O 3 particles, which facilitates the interfacial thermal conduction and enhances the thermal conductivity from 5.9 to 6.7 W m −1 K −1 . Along with additional electrical insulation, this filler modification strategy is believed to inspire others to develop high-performance polymer-based TIMs for future advanced electronics.

Exploring Lipoic Acid-Mediated Dynamic Bottlebrush Elastomers as a New Platform for the Design of High-Performance Thermally Conductive Materials

“…Typically, a large dose of the filler is an essential condition to achieve the critical thresholds for the construction of a thermal conductive network, which brings inevitable limitations. Often, the processing procedures (e.g., degassing) dealing with large viscosity precursors are complicated and energy-consuming; the large rigidity of the composites will be difficult to comply with the substrate, leading to an increase in interfacial thermal resistance and high packing force; the cost and density of the composite with large dose of metal fillers are high; etc.…”

“…The pursuit of high-performance thermal interface materials requires one to balance thermal conductivity with the need for physical properties that include low modulus (within the Shore OO range). A high modulus thermal pad will be difficult to match with the applied surface, leading to the increment of interfacial thermal transfer barrier and high packing stress . Bottlebrush elastomers have attracted considerable attention as the inherently low-frequency shear moduli (<few hundred kPa range) can be created by introducing side chains covalently along the network backbone.…”

Study of the Mechanism of Liquid‐Metal‐Assisted Thermal Interface Materials

“…When bond line thickness (BLT) is between 10–100 μm, The thermal contact resistance ( R c ) of TIMs contributes to most of the thermal resistance. [ 21–24 ]…”

“…When bond line thickness (BLT) is between 10-100 μm, The thermal contact resistance (R c ) of TIMs contributes to most of the thermal resistance. [21][22][23][24] Compared to solid powders, the excellent rheological properties of LMs help to address the drawbacks of traditional methods for enhancing the properties of TIMs. The traditional methods increase the thermal conductivity of thermal grease by increasing the load of powders with high thermal conductivity.…”

Effects of polymer polarity on the interface interaction of polymer/liquid metal composites

“…e.g. controlling the LM content, 7 the surface hydrophobic treatment, 8 and adjusting the mixing shear force, 2 to optimize the size and the stability. Majidi and co-workers chose a low filler content of 10 vol% and increased the sonification power and time of a LM suspension to break the agglomeration force.…”