Modification of Al2O3 particles by T-shaped trialkoxylsilylethyl-terminated polydimethylsiloxane oligomers and their applications in thermal interface materials

Abstract

A series of T-shaped trialkoxysilylethyl-terminated polydimethylsiloxane oligomers with different terminal structures and different degrees of polymerization have been synthesized by a series of reactions and functioned as the surface treatment agent for Alumina particles. The influence of the structure, degree of polymerization, the treatment method of the prepared oligomers, the mass ratio of alumina particles with different particle sizes, the viscosity of the matrix, the ratio between the modifier and the matrix, and the volume fraction of the mixed-size alumina particles on the fluidity and thermal conductivity of the silicone paste were investigated in detail. When a T-shaped trimethoxylsilylethyl-terminated polydimethylsiloxane with a degree of polymerization of 8 was used as the modifier for the mixed-size alumina particles consisting of 70 μm, 3 μm and 0.5 μm blended in a mass ratio of 9: 4: 2 and its dosage is 1/10 mass of the dimethyl silicone oil with a viscosity of 100 mPa.s, a silicone paste filled with 87 vol% hybrid alumina particles with a thermal conductivity of 6.95 W/(m· K) and good fluidity could be prepared. In the 30 W HB-LED heat dissipation application experiment, the results of thermal infrared imaging indicated that compared with the silicone paste filled with 83 vol% alumina with the same compositions while no modifier is used, the surface temperature on the HB-LED chip dropped from 118.2 °C to 79.0 °C. Moreover, the silicone paste with 87 vol% alumina had a higher cone penetration than that without the addition of any modifier. Based on the FT-IR, XPS, and 3D microscopy images of the modified alumina filler, the modification mechanism was briefly discussed.