Metal matrix composites have been recently developed for electronic packaging applications due to their attractive combination of physical properties, manufacturing flexibilities and relatively inexpensive cost. One benefit of metal matrix composites is the ability to tailor the physical properties, such as thermal expansion coefficient and thermal conductivity, through the proper selection of reinforcement and matrix. In addition, the manufacturing flexibility of the metal matrix composite by various processes allows the fabrication of complicated shaped parts. As the low-cost production routes of reinforcements have been developed, the metal matrix composites may offer a range of cost-effective solutions to emerging problems in electronic packaging. In order to use the metal matrix composites for electronic packaging applications, it is very important to increase the volume fraction of ceramic reinforcement over 50% to reduce the thermal expansion coefficient comparable to those of semiconductors. In this research, the fabrication processes of high volume fraction SiC preforms were investigated. The high volume fraction of SiC preforms were fabricated by two different process, i.e. vacuum assisted extraction process and ball milling and pressing process. The SiC particles were wet mixed with inorganic binder, organic binder and flocculant in vacuum assisted extraction process. While the SiC particles were ball milled with inorganic binder, organic binder and flocculant in ball milling and pressing process. The mixtures were cold pressed into cylindrical preforms and followed by drying and calcination. The SiC preforms with 50∼55vol.%SiC could be fabricated in vacuum assisted extraction process, while the preform with 60∼75vol%SiC could be fabricated in ball milling and pressing process, SiC particles with two different size were used for fabrication of the preforms with the volume fraction above 60vol%SiC in ball milling and pressing process. The fabrication conditions of stirring for 10min, natural drying for 36hrs, oven drying for 12hrs, calcination at 1100℃ for 4hrs were obtained for the optimum processing condition of preforms with high strength. The compressive strength of SiC preform increases with increasing the binder concentration and calcination temperature. The effect of organic binder on preform is examined by microstructure analysis and compression test. The binder distribution was not uniform in SiC preforms. The volume fraction of binder is relatively high at the exterior part of preform while the volume fraction of binder is relatively low at the interior part of it. The SiC/Al metal matrix composite were fabricated by squeeze casting process with the melting temperature at 800℃, mold temperature at 300℃, preform preheating temperature at 750℃ and pressure 50MPa. The pressure drop during squeeze casting process were calculated through the experimental results of infiltration depth of Al melts with varying pressure holding time and theoretical value of contact angle, density of melt and surface energy of melt. When particle size of reinforcement is 48㎛, volume fraction of reinforcement is 58vol.%SiC and the temperature of melt is 800℃, the pressure drop was calculated with the value of 8.5378MPa in the consideration of capillary force, internal friction and gravitational force during squeeze casting process. The relative densities of SiC/Al metal matrix composites with the volume fraction of 50, 58 and 71vol%SiC exhibited above 99%, while the relative density of SiC/Al metal matrix composites with the volume fraction of 78vol.%SiC exhibited below 93%. The agglomerate of SiC particle with the size of 0.2㎛ inhibiting the infiltration of Al melts were observed in the microstructure of SiC/Al metal matrix composites with the volume fraction of 78vol.%SiC, thus the SiC/Al metal matrix composites with the volume fraction of 78vol.%SiC exhibited lowest relative density. Thermal conductivities were measured by Laser Flash Method and the coefficient of thermal expansion were measured by TMA. The thermal conductivities were decreased with increasing the amount of binder and with increasing the volume fraction of reinforcement. The coefficient of thermal expansion decreased with increasing the volume fraction of reinforcement, while the coefficient of thermal expansion was insensitive with increasing the amount of binder. The experimental results of coefficient of thermal expansion were good accordance with the calculated values of coefficient of thermal expansion based on Turner's Model. The thermal conductivity of SiC/Al metal matrix composites with the volume fraction of 71vol.%SiC exhibited 130W/mK and the coefficient of thermal expansion exhibited 6~7×$10^{-6}$/K. The values of thermal conductivity and coefficient of thermal expansion of SiC/Al metal matrix composites with the volume fraction of 71vol.%SiC show that the metal matrix composites have the possibility for the electronic packaging applications.
