In this paper, a kind of highly conductive thermal paste is investigated, which consists of liquid metal alloy (LMA) and copper particles. The LMA used in the current research is a gallium-indium-tin eutectic alloy (Ga62.5In21.5Sn16). The copper particles dispersing into LMA have an average diameter of 9 μm. During the dispersing process, a degassing process was conducted in order to reduce air bubbles and increase the thermal conductivity of the investigated paste. A new method based on laser flash (LFA) was used to test the total thermal conductivities of the samples. Three types of thermal pastes were prepared and tested, i.e., LMA, oxidized liquid metal alloy (OLMA), and OLMA mixed with copper particles. Results show that when LMA, OLMA, and OLMA mixed with copper particles at a ratio of 5wt%, the resulting thermal conductivities of the investigated thermal pastes can achieve 44.48 W/mK, 13.55 W/mK, and 24.34 W/mK, which result in the corresponding thermal contact resistances of 4.044 mm2K/W, 5.638 mm2K/W, and 4.075 mm2K/W, respectively. In addition, the effect of the copper particle ratio on the thermal performance was investigated. Results show that when the ratio of copper particles increased from 5wt% to 10wt%, the thermal conductivity of investigated thermal paste increased from 24.34 W/mK to 29.07 W/mK, and the thermal contact resistance decreased from 4.075 mm2K/W to 3.37 mm2K/W.

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