Preparation And Properties Of Additive Silicone Rubber/Alumina Thermal Interface Composites

Thermal interface composites can be filled between heat source and radiator,which can expel air and accelerate heat dissipation.They are widely used in power electronic equipment.Improving the thermal conductivity and comprehensive performance of thermal interface composites is of great significance for ensuring the normal operation of power electronic equipment and promoting the development of power electronic equipment towards lightweight,miniaturization and high efficiency.Firstly,this thesis introduces the preparation materials and preparation process of thermal interface composite.The silicone rubber matrix we use is vinyl silicone oil,the crosslinking agent is hydrogenated silicone oil,and the heat conduction assistant is platinum catalyst and the inhibitor.we use the dodecyl trimethoxysilane coupling agent to treat the surface of the alumina filler and form a highly thermally conductive filler system.We fill the filler system into the matrix and vulcanize at 130℃ for 10-15 min.Secondly,this thesis has a research on the thermal conductivity of thermal interface materials and analysises the effects of different factors on thermal conductivity.We mix 70μm,5μm and 1.5μm spherical aluminas treated by coupling agent at a ratio of 6:2:2 to obtain composite material,when the filler content is in the range of 0%-96%,the thermal conductivity of thermal interface composites increases with the increase of filler content.When the particle size of filler is 45μm and the filling content is 80%,the thermal conductivity of spherical alumina is higher than that of the alumina which shape is similar with sphere,and the thermal conductivity of the alumina which shape is similar with sphere is higher than that of the flaky alumina.If the silicone rubber matrix is filled with alumina which only has a single particle size,when the filling content is 88%and the particle size ranges from 1.5 to 100 μm,the thermal conductivity of the composites increases first and then decreases with the increase of particle size.When the particle size of filler is 70μm,the maximum thermal conductivity is 1.63 W/(m.K).The thermal conductivity of the composite prepared by the filler which has two different particle sizes is higher than the thermal conductivity of the composite prepared by the filler which only has a single particle size.We mix 70μm and 5μm spherical aluminas treated by coupling agent at a ratio of 6:4 to obtain composite material,when the filling content reaches 90%,its thermal conductivity is 3.1 W/(m.K).The mixing of three different particle sizes of alumina can further improve the internal heat conduction network of the material,and the composite material has higher thermal conductivity than the composite prepared by filler which has two different particle sizes.We mix 70μm,5μm and 1.5μm spherical aluminas treated by coupling agent at a ratio of 6:2:2 to obtain composite material,finally the maximum filler content we can achieve is 96%.At this time,the thermal conductivity of the sample is 6.42W/(m·K).Thirdly,this thesis has a research on the electrical properties of thermal interface composites.We mix 70μm,5μm and 1.5μm spherical aluminas treated by coupling agent at a ratio of 6:2:2 to obtain composite material,when the filler content is in the range of 0%-95%,the breakdown field strength decreases gradually with the increase of filler content;when the filler content is in the range of 0%-90%,the dielectric constant and dielectric loss increase gradually with the increase of filler content;when the temperature is the range of 20℃-160℃ and the filler content is the same,the dielectric constant and dielectric loss increase with the increase of temperature.Finally,this thesis has a research on the mechanical properties of thermal interface composites.We mix 70μm,5μm and 1.5μm spherical aluminas treated by coupling agent at a ratio of 6:2:2 to obtain composite material,when the filler content is in the range of 0%-95%,with the increase of filler content,the hardness of the composites increased gradually,while the tensile strength,elongation at break,tear strength and compression ratio decreased gradually.The research shows that the thermal conductivity of thermal interface composites can be greatly improved by surface treatment of fillers and mixing of fillers,and the electrical and mechanical properties of thermal interface composites can be also improved to a certain degree.