Enhanced thermal conductivity of liquid metal composite with lower surface tension as thermal interface materials

Abstract

Gallium (Ga)-based liquid metal (LM) has attracted great interest for thermal management due to its high thermal conductivity (Tc). However, the surface tension of LM is too high to wet the surface of the heat source and sink, and there are great risks of a short circuit of devices caused by LM leakage. The high surface tension also makes it difficult to well mix LM and fillers to prepare composite paste for thermal interface application. We found that the contact angle of LM on Boron nitride (BN) pill surface could decreased from 133° to 105° by doping tungsten (W) nanoparticles indicating the surface tension of LM could be decreased by doping W nanoparticles. The adding sequence of LM, W and BN were found could affect the final form of the composite, and the composite paste (LM+W-BN) can only be obtained by mixing W nanoparticles with LM first (LM + W). As contrast, other adding sequences or without W nanoparticles can only obtain composite powder. LM+W-BN paste exhibits a high Tc of 14.49 W m−1 K−1, and the stability of LM+W-BN paste under pressure, high-temperature, thermal shock and high humidity was also investigated in detail. LM+W-BN paste shows an excellent thermal management ability as a TIM by application in a light emitting diode (LED) module. This approach has also been extended to other thermal conductive fillers including carbon fiber and graphene. This work offers a simple approach to lower LM surface tension and might also enable the incorporation of other fillers, expanding the use of LM, such as integrated circuits and flexible electronics.

Keywords

• Liquid metal
• Surface tension
• Boron nitride
• Thermal conductivity
• Thermal interface material