Fabrication And Properties Of SiC_p/Al Electrical Packaging Composites By Spark Plasma Sintering

SiC_p/Al composites have become the hotspot of the research of electronic packaging materials due to its low density, high thermal conductivities (TC) and low and adjustable coefficient of thermal expansion (CTE). At present, the methods to fabricate SiC_p/Al composites are mainly Powder Metallurgy (PM) and Infiltration. But both of them have limitations. PM has a limitation on SiC content, sometimes the content of SiC can't exceed 55vol%, which will restrict the further decline of CTEs;the high temperature during infiltration process will result in interface reaction and produce brittle phase which is adverse to composites' properties. Also, the residual pores and agglomerant exert an influence on TCs of composites.According to the limitations of the above-mentioned methods, Spark Plasma Sintering has been applied in our study. We, firstly, confirmed the plausibility of this method to fabricate SiC_p/Al composites through the fabrication of SiC_p/Al composites with low content of SiC particles, and primarily explored the effects of temperature, pressure and heating-rate on the fabrication. As our method is similar to traditional powder metallurgy, how to improve the SiC content is still a big problem. In order to overcome it, we have introduced particle-match method, and found out proper proportion among the various particles sizes, then to successfully obtain 65vol%SiC_p/Al composites with 99% relative density. The tests of thermal properties showed that TCs in our study were all higher than 200w/m.K which well met the demand of electronic packaging materials. But CTEs were a little higher than those of other methods' samples. Meanwhile, we have found that the large sized SiC particles played a more important role in the decline of CTEs than the small ones did. TCs increased with the increment of size of SiC particles, but the fracture strength were a little lower than those of other methods' samples which may be attributed to the large size of our SiC particles. To furthermore decline CTEs, we brought in Si as additive. By the adjustment of sintering process, we have obtained 60vol%SiC_p/Al composites with various contents of Si powder. The results of thermal properties showed that the addition of Si powder could reduce CTEs to a large extent, when theSi content was 10vol%, CTE was low at 7.8 X 10"6/K. However, the introduction of Si also did some harm to TCs. We tested the fracture toughness and found that composites more inclined to fracture due to the increment of Si powder. So, taking both the thermal and mechanical properties into consideration, we believed that for 60vol%SiCp/Al composites, the optimum content of Si was 5vol%. At last, with the analysis of the sintering process, we primarily detected the mechanism of SPS sintering SiC/Al, and believed that the densification in our study was mainly dependent on joule heat and high pressure.All the results demonstrated that through properly particle-match and addition contents, SiCp/al composites with low density, high thermal conductivities, low coefficient of thermal expansion and sound mechanical properties which well meet the demand of electric packaging materials can be obtained by Spark Plasma Sintering.