Date/Time: 04-23-2019 - Tuesday - 05:00 PM - 07:00 PM
Wilson Kong1 Matthew Ralphs1 Robert Wang1 Konrad Rykaczewski1

1, Arizona State University, Tempe, Arizona, United States

As increasingly powerful microelectronic chips shrink in size and scale, inadequate waste heat dissipation ultimately results in poor computational performance or early device failure. Therefore, advances in thermal interface materials (TIMs) are necessary in combating detrimental heating issues by providing improved avenues for thermal transport. Many types of polymer-filler combinations for TIMs have been explored to maximize the composite thermal conductivity, while only leading to thermal conductivities of up to 2 W m-1K-1. One of the primary limitations to efficient thermal transport in TIMs lies in the boundary resistance generated by the point-contact of filler particles. Additionally, the thermally conductive inclusions are often rigid particles which can lower the elasticity of the composite at high fill factors. Increasing the effective contact area between filler materials could potentially result in much higher composite thermal conductivities [1,2]. Previous work done by Ralphs et al. has shown a substantial increase in thermal conductivity by up to 17 W m-1K-1with copper particles bridged by liquid metals in a PDMS matrix [3].
In this work, multi-phase fillers comprised of a solid metal core with a liquid metal shell are proposed as a promising solution to reducing point-contact boundary resistance. Liquid metals form a self-limiting oxide layer that encapsulates the liquid metal and can rupture under applied pressure, therefore allowing liquid metal coated particles to connect. Due to the tendency of liquid metals to alloy with and/or embrittle many metals, tungsten is selected as the core material for its relative inertness towards liquid metals. In addition, tungsten particles coated with liquid metals can also be mechanically processed to increase the effective contact area between adjacent particles. The novel combination of deformable liquid shells and highly thermally conductive solid particles can potentially lead to composite materials that facilitate more efficient heat transport and are still stretchable. This research seeks to demonstrate a reduction in thermal boundary resistance that improves TIMs through novel materials processing methods.
[1] Mamunya et al. Eur. Polym. J. 2002. 8(9), 1887-1897.
[2] Seshadri et al. Adv. Mater. Interfaces. 2015. 27(17), 175601.
[3] Ralphs et al. ACS App. Mater Inter., 2018.10(2), 2083-2092.

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