The influence of silicon content on the thermal conductivity of Al-Si/diamond composites

Diamond reinforced Al-based composites with excellent comprehensive properties (i.e., high thermal conductivity, flexible coefficient of thermal expansion) are showing great potential for high power density packaging. In this study, effect of the Silicon addition on the thermal conductivity and interfacial characteristic of the Al-Si/diamond composites are investigated. Al-Si alloy containing 1.0, 2.0, 3.0, 4.5, 7.0, 10.0, 14.0, 20.0 wt. % Si are prepared as the matrix and Al-Si/diamond composites are fabricated by pressure infiltration under 800degC and 5 Mpa. The analysis of the SEM and the element distribution maps detected by the EDX shows that, as the Si addition, the Si skeleton of the AlSi-eutectic phase segregates to the diamond particle surface and form a better bonding between the reinforcement phase and the matrix. The highest thermal conductivity of the composites gets at Al-1.0 Si/diamond as 248 W/m K. The results, which are calculated using the differential effective medium scheme (DEM), indicate that the interfacial thermal conductance (h) shows first an increase and then a decrease with Silicon content. Overall, Si addition can raise the h.