Preparation Of High Volume Fraction SiC/Al Package Materials By Gel-casting Method

High volume fraction SiC/Al composites with excellent thermal and mechanical properties, low density, showing great advantages in the area of electronic packaging applications. It is difficult for preparation of high volume fraction SiC/Al composites into the required shape by traditional machining as a result of its own high hardness, which limits its applications. In this paper, near net shape process of SiC/Al composites with high SiC volume fraction was explored by combining gel-casting method with liquid aluminium alloy pressureless infiltration technique. The gel-casting characteristics of SiC slurry were studied. The thermo-physical and mechanical properties of SiC/Al composites were investigated and their influencing factors and change regulations were discussed.The research conclusions for SiC slurry and SiC preforms by gel-casting as following: the surface zeta potential of SiC can be effectively improved by adding dispersant and oxidation treatment of SiC powder. The SiC slurry viscosity increases with volume fraction increasing, decreases with the finer particle size distribution and the increase of dispersant content increasing, the amount of dispersant 1wt% was added in SiC slurry, the best content for trigger agents and catalysts used in the process of gel casting are 0.002g/ml and 0.0004ml/ml respectively; SiC preforms with particles distribution uniform and well mechanical properties were successfully prepared by gel casting. A small quantity of high-temperature binder added can reduce the sintering temperature and oxidation content of SiC particles. When SiC mixture of F80+F325+W14,F120+F325+W14,F170+ W28+W7和F170+W14 used as raw material, SiC volume content in the preforms can reach 67%, 64%, 62% and 60% respectively .High volume fraction SiC/Al Composites derived from the mixed SiC particles have uniform, dense microstructure and good interface state. The fracture mechanism of the composites materials is mainly brittle fracture of coarse SiC particles. Small particle size distribution is conducive to high mechanical strength. Annealing can promote the mechanical strengths of SiC/Al composites with different renforcement mixture of F80+F325+W14, F120+F325+W14, F170+ W28+W7 and F170+W14 ranges from 208MPa, 241MPa, 305MPa and 303MPa to 265MPa, 276MPa , 334MPa and 365MPa respectively.The thermal conductivity of SiC/Al composites increases with SiC particle size distribution and volume fraction increasing, the thermal conductivity of SiC/Al composites for SiC mixture F80+F325+W14, F120+F325+W14 and F170+ W28+W7 are 187W/m.K, 175W/m.K and 161W/m.K respectively. under the same SiC volume fraction conditions, coefficient of thermal expansion is mainly affected by the volume fraction of SiC, decreasing with particle volume fraction, , when SiC volume fraction ranges from 64% to 67% for the mixture of F120+F325+W14, the coefficient of thermal expansion of the composites ranges from 6.8×10-6/K to 5.6 ×10-6/K.