Preparation And Thermal Conductivity Of Liquid Metal-based And Silicone-based Thermal Interface Materials

Efficient thermal interface materials are the key to improve the heat dissipation of electronic devices.Liquid metals have high thermal conductivities and good flow characteristics,and therefore have received widespread attention.However,excessive fluidity also causes material migration problems and limits the use of liquid metals.In this paper,liquid metal base and silicone rubber base composite materials were prepared by mixing liquid metal with metallic particles and fixing liquid metal in silicone rubber.The thermal conducting properties of the composite materials were studied.The main contents are as follows:1.Copper powder/liquid metal composite material and silver powder/liquid metal composite material were prepared with liquid metal(Ga75In25 alloy)as matrix.The composite materials were prepared by mixing different particle sizes of copper powder with different shapes of silver powder and liquid metal through degassing and stirring methods.The thermal conductivity and interface thermal resistance of the composite materials were tested on a thermal conductivity and interface thermal resistance test system(Long Win Science&Technology Corp LW9389).The effects of filling amount,particle size,shape,and size grading of copper powder and silver powder on the thermal conductivity of the liquid metal matrix composites were investigated.The causes of the changes in the thermal conductivity of the composites were analyzed.The influences of pressure and temperature on the thermal conductivity of the copper powder/liquid metal composites were studied.The results show that when the particle size of copper powder is 2.5?m and the volume of copper powder is 12vol.%,the thermal conductivity of the composite is the highest,which is 34.665W/(m·K)and is about 6 times as high as that of the thermal conductive products on the market.When the volume fraction of the filler is 5 vol.%and the ratio of flake silver powder to spherical silver powder is 1:2,the thermal conductivity of the composite material reaches 19.532 W/(m·K)and is higher than that of other products on the market.2.Liquid metal/silicon rubber composite materials,copper powder/silicone rubber composite materials,silver powder/silicone rubber composites materials and flake silver/liquid metal/silicone rubber composite materials were prepared by mixing liquid metal,copper powder,silver powder and vinyl silicone oil,followed by degassing and curing at an appropriate temperature.The thermal conductivity and interface thermal resistance of the composite materials were tested on a thermal conductivity and interface thermal resistance test system(Long Win Science&Technology Corp LW9389).The thermal conductivity of the composite materials was also tested on a thermal conductivity test system(XIATECH TC3000D).The internal structure of the composite materials was observed by scanning electron microscopy(SEM).The effects of liquid metal loading,copper powder loading,particle size of the copper powder,shape of silver particle and flake silver loading on the thermal conductivity of silicone rubber matrix composites were studied.The results show that the composites can be ranked as follow respecting to thermal conductivity:flake silver powder/liquid metal/silicone rubber composites,liquid metal/silicone rubber composites,silver/silicone rubber composites,copper powder/silicone rubber composites.The thermal conducting property of flake silver/liquid metal/silicone rubber composites is enhanced with the increase of the amount of flake silver powder.The lowest interface thermal resistance is 0.85°C?cm~2/W,which is two orders of magnitude lower than that of ordinary silicone rubber.