The Research On Microstructure And Properties Of Electronic Packaging SiC_p/Al Composite Fabricated By Powder Thixoforming

In recent years, the electronic packaging technology had developed towards the miniaturization, high performance, high reliability and low cost due to the rapid development of microelectronics and integrated circuit (IC). This development required high performance of the electronic packaging materials. Metal matrix composites (MMC), possessing high thermal conductivity (TC) of the metal matrix and low coefficient of thermal expansion (CTE) of the reinforcements, had become one of the most potential electronic packaging materials. SiCp reinforced A1 matrix composites (SiCp/Al) was one of the most available electronic packaging materials due to their high thermal conductivity (TC), low coefficient of thermal expansion (CTE), high flexural strength and low density. This study, based on the technologies of powder metallurgy and thixoforming, proposed a new processing technology named powder thixoforming to prepare SiCp/Al composites using the blending and pressing procedures of powder metallurgy (PM), partial remelting and forming procedure of thixoforming. This technology, combining the advantages of powder metallurgy and thixoforming technologies, had the characteristics of manageablity, low cost, high density and uniform distribution of reinforcement in the composites. Moreover, the reaction thermodynamics between the A1 and SiCp was investigated in this thesis, and the effects of different parameters, such as remelting tmperature, time and mould temperature, on microstructure and properties of the resulting SiCp/Al composite was also demonstrated. The main results achieved were summarized as follows:It was shown by DSC kinetic results that the melting point of A1-Si alloy was 585.8℃, thermodynamic chemical reaction between A1 and SiC could not easily occur when the temperature was held nearby the melting point of alloy for a short time. The experimental results were significant to choose appropriate remelting time and temperature in order to prevent harmful surface reaction from taking place effectively.In addition, the effects of the processing parameters on the microstructure and properties of composites was investigate. The results showed that all of the parameters had an obvious effect on the microstructure and properties. With extension of remelting time and increase of remelting temperature, high density and uniform distribution of SiCp of the composites were obtained. However, the TEM structure observation indicated that the reaction of interface between SiCp and A1 could be promoted by the excessive extension of remelting time. Meanwhile, the density of composites was improved with the increase of mold temperature, but congregation of SiCp would occur caused by high mold temperature, leading decrease of the uniformity of microstructure. For purpose of obtaining applicable thixoforming components, a pyknotic and uniform microstructure should be obtained through adjusting the processing parameters. The suitable processing parameters were heating at 610 ° C and holding 90 min simultaneously, subsequently adopting 350 ℃ mold temperature for thixoforming. The microstructure showed that SiC particulates were well distributed in the aluminum matrix. It had also been found that SiCp/Al composite materials with a high relative density could be obtained by the thixoforming process. The ultimate thermal conductivity (TC), coefficient of thermal expansion (CTE), hardness and bending strength of the resulting composite attained 167.35 W·m-1·K-1,115.31HV, 387.73Mpa respectively. Meanwhile, the mean linear coefficient of thermal expansion of composites from room temperature to 300℃ was less than 6.5ppm/K. The properties of the composite material could well conform to the application requirements of electronic packaging materials.