Pressureless Infiltration Of SiCp/Al Electronic Packaging Materials With Particles Of Bimodal Size Distribution

Silicon carbide reinforced aluminum composites have great potential applications in electronic packaging because of its high thermal conductivity (TC), high strength, low coefficient of thermal expansion (CTE) and low density. The SiC particles with bimodal distribution can decrease CTE of the composite, and the pressureless infiltration processing has the advantage of low cost and simple operation, thus Al/SiC composites with the bimodal size distribution were studied in the article, including the preparation of the preform with bimodal SiC particle size distribution, the pressureless infiltration kinetics of the aluminium alloy, the microstructure of Al/SiC preform with bimodal size particle distribution. The conclusions are shown below:When the preform composed of SiC particles with 5μm and 50μm, the particle volume fraction can change from 52% to 71% with the different particle proportion. High-pressure could cause the particle of preform crack and then damage the preform properties. Changing temperatures quickly will induce microcracks in perform. At the same sintering condition, the oxidation quantity is directly proportion to the preform surface area, and the thickness of the oxide layer in the fine and coarse particle are similar.The incubation period is determined by the chemical reactions between molten alloys and silicon oxide at SiC particle surfaces. When the chemical composition of silicon is fixed, the period will decrease with the increase of infiltration temperature and the chemical composition of magnesium. The infiltration is controlled by both chemical and physical process, the chemical process is the precondition, and the physics process mainly controls the infiltration rate. The infiltration rate of molten alloys into porous SiC is related to the loss of magnesium and the temperature. When the atmosphere is inert, the rate will decrease severely by the loss of magnesium and lower temperatures. An equation was proposed by using the Darcy law and hydromechanics. A model of macroscopically infiltration and microscopically infiltration of liquid alloy in porous SiC preform with bimodal particle size distribution was proposed, and the infiltration process is interpreted with a substitute mechanism and a consume mechanism.The microstructure and interface of the composite were studied by SEM and X-ray diffraction, the results show that the SiC particles and Al matrix are well connected, few defects exist in the composite, the density of the composite decreaseswith the particle volume fraction increases. The matrix and reinforcement are chemically bonded. The interfacial products are nanometer MgO and MgAl2O4, and the MgO proportion is increased with the Mg content increase in the matrix. The fracture of composites is controlled by particle crack when the composite is prepared under high temperature and high Mg content, the fracture is controlled by the defects in the particle and the particle size when the volume of coarse SiC particles is high, and the fracture is controlled by the interface when the interfacial bond strength is weak.