The Development Of Addition-Cured Rtv Silicone Rubber Based Insulative Thermal Conductive Adhesive

To reduce the thermal resistance of high-power LED packaging, this paper developed a insulated thermal conductive adhesive, which is silicone rubber based and filled with 4.9μm Al2O3, 1μm ZnO and four kinds of AlN powder. In this paper, Differential Scanning Thermal Analysis and Thermogravimetric Analysis are adopted to research the formulation of the silicone rubber, including the usage amount of catalyst, negative catalyst and the value of SiH/SiVi. At the same time, the vulcanization craft is laid down. The most suitable coupling agent is selected from KH550, ND-42 and A-171 by settlement experiment. Surface modification craft is discussed. This paper tests the heat conductivity of silicone rubber based adhesive filled with different filler by Steady-State Heat Flow method. KH-560 and high viscosity vinyl silicone oil is added into the adhesive to enhance the adhesive ability to aluminium alloy, the tensile shear strength test is performed following GB-T7124, and the viscosity of the adhesive is tested by BROOKFIELD DV-II+ viscosity meter. Finally, following ASTM149-09, the dielectric strength is tested.It is found that when the formulation of the sillicone rubber is vinyl silicone oil: containing hydrogen silicone oil: catalyst: negative catalyst=10: 3.086: 0.05: 0.025, the vulcanization craft is 15h at room temperature or cured rapidly when the temperature exceeds 78.8℃.Of all the coupling agent, KH-550 is the most effictive, but it will cause catalyst damage. So ND-42 is used as the universal coupling agent in this paper.The maximum load of Al₂O₃, ZnO, 10μm and 2.2μm AlN (after and before surface modification) is 500phr, and the thermal conductivity of the corresponding adhesive is 1.327 W/m·K , 1.021W/m·K , 1.823W/m·K (1.752W/m·K) and 1.523W/m·K (1.512W/m·K), while the 30μmAlN is 300phr and the thermal conductivity of the corresponding adhesive is 1.202W/m·K. Experimental results demonstrate that when the silicone rubber filled with 400phr 10μm AlN combining with 100phr 2.2μmAlN, synergistic effect emerges, the thermal conductivity of the corresponding adhesive is 1.87W/m·K. on the other hand, 400phr Al₂O₃ combining with 50 phr ZnO, the thermal conductivity is 1.036 W/m·K.When the usage amount of KH-560 and high viscosity vinyl silicone oil is 1phr and 20phr, the tensile shear strength of the adhesive filler by 400phr 10μm AlN and 10phr 2.2μm AlN is 1.056Mpa, the viscosity is 52000 mPa·s .The dielectric strength of the adhesive is higher than 14.78kV/mm.The addition-cured silicone rubber based insulative thermal condutive adhesive has high thermal conductivity, meanwhile, first rate dielectric strength. It can satisfy the tough requirement of LED packaging and has a very good application prospects.