Multiphasic Liquid Metal Soft Composites for Thermal Management of Microelectronics

Thermal management of evolving microelectronic devices is critical in achieving their optimal performance and extended lifetime. The development of thermal interface materials (TIMs) with tunable thermal and mechanical properties has been the subject of intensive industrial and academic research in recent years. TIMs consist of thermally conductive, often solid, fillers dispersed in a pliable matrix material that result in a synergistic blend of thermo-mechanical properties that enable conformability to the intrinsically rough interfaces between components and lowering of thermal resistance. However, much of the overall TIM performance is limited by thermal resistances between filler materials, the filler-matrix, and contact resistance between the TIM and substrates. Emerging gallium-based liquid metals (LMs) have been explored as an alternative material for TIM applications, yet suffer from drawbacks related to low viscosity, surface tension, and corrosiveness towards metals. In this work, we discuss strategies in which to utilize LM as a component in multiphasic soft composites for improved thermal performance. LM and silicon carbide (SiC) microparticles are investigated as a hybrid filler dispersed in an uncured silicone oil matrix.¹ Through tuning the composition and applied pressure, this composite achieves an effective thermal conductivity of ~10 W/mK (or ~17 W/mK if contact resistance is taken into account). We also demonstrate the need for a metallic wetting layer to enable reactive-wetting between LM and the non-LM-wetting SiC. Utilizing these design principles, we explored additional hybrid filler combinations and processing methodologies that led to soft emulsions with high thermal conductivity and unique microstructures.^2,3 This work outlines the structure-property relationships that influence the thermal performance of LM-based materials and aims to further catalyze exploration into these liquid phase composites in thermal management and other soft applications. <br/>References:<br/>1. Kong, Wilson, et al. "High Thermal Conductivity in Multiphase Liquid Metal and Silicon Carbide Soft Composites." Advanced Materials Interfaces 8.14 (2021): 2100069.<br/>2. Uppal, Aastha, et al. "Enhancing Thermal Transport in Silicone Composites via Bridging Liquid Metal Fillers with Reactive Metal Co-Fillers and Matrix Viscosity Tuning." ACS Applied Materials & Interfaces 13.36 (2021): 43348-43355.<br/>3. Shah, Najam Ul Hassan, et al. "Gallium oxide-stabilized oil in liquid metal emulsions." Soft Matter 17.36 (2021): 8269-8275.