Research On Preparation And Performance Of Silicone Oil-based Thermal Interface Material With High Thermal Conductivity

Thermal interface material(TIM)is a type of material used to fill contact gaps between heat-generating components and heat-dissipating components.It is of great significance for various electronic devices to quickly dissipate heat and maintain their working stability.Compared with other types of TIM,the fluid and insulating thermal grease has better wetting performance with the contact surface,has a lower thermal resistance,and the insulation performance makes it widely used in special fields such as electronics and electrical field.In this paper,a series of thermal greases doped with BN and Al₂O₃ fillers had been prepared,and the thermal conductivity of insulating thermal greases was mainly studied.First,spray-drying method was used to produce two kinds of spherical BN particles with different particle sizes by study few factors that affect particle shape,and prepared spherical BN-filled thermal grease.Then,flake Al₂O₃ with good dispersibility and uniform thickness was prepared by molten salt method,and thermal grease filled with flake Al₂O₃,and thermal grease filled with mixed flake Al₂O₃ and spherical BN were prepared.Finally,Al₂O₃ doped thermal grease was made of micron Al₂O₃ with different particle diameters,and the thermal conductivity of micron Al₂O₃ thermal grease with mixed particle diameters.The nano Al₂O₃was sintered at a high temperature to produce a branched structure,which was added to the micron Al₂O₃ thermal grease,and the thermal properties of these Al₂O₃ thermal grease were measured.1.Using h-BN,PVA(polyvinyl alcohol),SDBS(sodium dodecylbenzene sulfonate),etc.as raw materials,through three steps of ball milling,spray drying,and sintering,spherical BN with two different particle sizes were prepared,studied the influence of different ball milling time on the size of flake BN,the influence of different PVA content on the formation of spherical BN,the influence of slurry concentration on the particle size of spherical BN,and the obtained spherical BN was characterized by FTIR and XRD.Through the molten salt method,using Al₂(SO₄)₃,Na₂CO₃,Na₂SO₄,etc.as raw materials,the flake?-Al₂O₃ with good dispersibility was prepared,and a series of characterization tests were carried out on the flake?-Al₂O₃.Studies had shown that ball milling for 36 h had the best dispersion of flake BN.PVA with a content of 1 wt%can produce BN particles with better sphericity.The higher the slurry concentration,the larger the BN particle size.Statistics of the particle size distribution of the spherical BN showed that the average particle size of the two spherical BNs are 3.02?m and 3.65?m,respectively.The FTIR and XRD characterizations of spherical BN indicated that spherical BN had good crystallinity.The flake Al₂O₃ had a smooth surface,uniform thickness and good crystallinity.2.Using spherical BN and flaky Al₂O₃ as the filler of the thermal grease,a series of BN thermal grease and Al₂O₃ thermal grease were prepared,and the thermal conductivity,total thermal resistance and contact thermal resistance of the thermal grease were measured.And we used two thermal conductivity models to explain the thermal conductivity of the spherical BN-filled thermal grease with the different filler content.Experimental results showed that the thermal conductivity of two spherical BN filled thermal grease was better than that of flaky BN.At low content,the thermal conductivity of the thermal grease filled by the second spherical BN was closer to Maxwell-Eucken model,when the content was high,the thermal conductivity was closer to the predicted value of the Agari model.The two spherical BN with different particle sizes had different effects on the thermal conductivity of the thermal grease.The thermal conductivity of the thermal grease with a smaller particle size was 1.179 W/(m·K).Using KH550 and KH570 silane coupling agents to modify spherical Al₂O₃ can improve the thermal conductivity of the thermal grease.Combining flaky Al₂O₃with No.1 spherical BN,the two different types of particles had a synergistic effect.When the Al₂O₃ content was 50 vol%,a thermal conductivity of 1.53W/(m·K)was obtained in flaky Al₂O₃/spherical BN thermal grease.3.Using Al₂O₃ particles with different particle sizes and morphologies as the filler of dimethyl silicone oil,thermal grease with different solid content were prepared.First,the effect of the viscosity of dimethyl silicone oil on the thermal conductivity was studied,and then the influence of the particle size of the four spherical Al₂O₃ of 5?m,10?m,20?m,and 40?m on the thermal conductivity was explored,and then the partical size of micron spherical Al₂O₃ was studied on the influence of thermal conductivity.Finally,high-temperature sintered branched nano Al₂O₃ was used as the filler,and the branched nano Al₂O₃ was mixed with spherical micron Al₂O₃to prepare thermal grease.Experiments had proved that the use of high-viscosity dimethyl silicone oil can improve the thermal conductivity of thermal grease.When the content of 10?m Al₂O₃ was 60vol%,the thermal conductivity of thermal grease was 1.318 W/(m·K).Using the particle size mixed Al₂O₃ fill thermal grease,when 40?m:5?m=4:1,the thermal conductivity reached 1.339 W/(m·K),and the thermal conductivity of the thermal grease mixed with micro-nano Al₂O₃ was 1.367W/(m·K).