Formation And Characteristion Of Multicomponent Boron Carbide Cermets

The continuing increase in electronic packaging density and integrated circuit (IC) power levels has resulted in a need for High-performance electronic packaging materials with high thermal conductivities (TCs), coefficients of thermal expansion (CTEs) matching those of silicon chips and ceramic substrates, low densities, low dielectric constants, and so on.Boron carbide (B4C) is a potential material for electronic packaging materials, which has lower density, lower CET, higher hardness, better chemical inertness compared with others. B4C is main research object of this paper. Multicomponent B4C cermets (CERamic METal) were fabricated by pressureless infiltration technology, and the feasibility of using them as electronic packaging materials was researched. Pressureless infiltration processing technique involves the preparation of a ceramic perform, where ceramic particles are sintered into a porous, stiff and near-net-shape structure, and the spontaneous infiltration of molten metal into the ceramic perform. Due to the three-dimensional interconnected structure of the porosity in the ceramic perform, an interpenetrating network of ceramic and metal phase results if the pores can be filled completely with metal. Such interpenetrating structures are favorable for making best use of the interesting properties of the metal and ceramic constituents. The Cermets combine the low CETs, low densities and stiffness of ceramics with the high TCs and ductility of the infiltrated metal.In order to obtain the high quality B4C performs, the removal of oxides in raw B4C powders and the preparation process of B4C performs were investigated. The results showed that the pickling and ultrasonic treatment in absolute ethyl alcohol could remove boron oxide completely, and the quality and density of B4C performs were correlated with the addition amount of adhesive, grain composition and the parameters in cold-press process.The effects of surface coating treatment and preheating on the behavior of molten Al infiltrating spontaneously into B4C performs were discussed. In surface coating treatment, a sol-gel technique was employed to coat the B4C performs with TiO2, then a subsequent heat treatment produced TiB2 layers. In preheating process, the heat treatment of B4C performs at respectively 1900℃and 2000℃for 1h was involved. The findings showed that the TiB2 layers can facilitate the wetting of liquid Al on B4C performs, and the heat treatment at higher temperature can decrease surface area and increase the pore size of B4C performs, so as to enhance the infiltration kinetics of the B4C-Al system and reduce the reaction between B4C and Al.In situ synthesis of B4C/Al-AlN composites by infiltrating Al into B4C performs contained BN was proposed. The TCs of B4C/Al-AlN composites are higher than pure B4C ceramic, and are affected by the size of AlN grains and the contents of Al and pore.