Preparation And Properties Of Si_p/Al Composites By Spark Plasma Sintering

Sip/Al composites have become the hotpot of the research of electronic packing materials due to its low density, high thermal conductivity (TC) and low and adjustable coefficient of thermal expansion (CTE). In this paper, Sip/Al composites with different Si contents were prepared by spark plasma sintering (SPS). The fabrication process and thermal properties were studied, including improving thermal properties.Firstly, the Sip/Al composites with various Si contents from10wt%to40wt%were prepared by SPS. The effect of process parameters (Temperature, pressure and holding time) on the relative density, phase and microstructure was investigated. The results show that Sip/Al composites contain only Al phase and Si phase. The relative density grows up gradually at elevated temperatures and pressures, and the Sip/Al composite shows a dense structure with few pores, forming a connected network structure. However, the holding time has little effect on relative density. For the Sip/Al composites with60wt%Si, it’s hard to fabricate dense composites using monomodal particle size. It should be prepared by particle-match method, and then successfully obtain Sip/Al composites with more than97%relative density, in which40μm:10μm equals to2:1. With the analysis of the sintering process, we primarily detected the mechanism of SPS sintering Sip/Al composites and believed that the densification in our study was mainly dependent on joule heat or discharging between Al particles, which resulted in local high temperature, part of Al particles will soften or even melt, and thus fill the gaps between particles when acted high pressure, forming dense microstructure.Secondly, the thermal properties of Sip/Al composites were investigated. The dependence of the thermal properties, Si content and particle size was studied in this section. The TC and CTE are both declined with Si contents increasing. When the Si content is60wt%, the TC is107W/m·K and CTE is7.17×10-6/K. At the same time, with the increment of Si particle size, the TC grows up, whereas the CTE declines. Finally, In order to improve TC, we changed the process parameters, such as increasing sintering temperature and pressure, which can improve the interface between Si phase and Al phase, and the TC increased from113W/m·K to150W/m·K. Moreover, when the samples were annealed at500℃for2h in vacuum, the TC was further improved and reached to162W/m·K.