Reactive wetting of Sn-V solder alloys on polycrystalline CVD diamond

Abstract

In this paper, the reactive wetting of polycrystalline chemical vapour deposition (CVD) diamond by a novel Sn-V solder alloy was critically examined using the sessile drop method. It has been found the Sn-V solder alloys start to spread on the CVD diamond at around 600 °C. Moreover, 0.5 wt% addition of V is adequate to induce an outstanding spreading of Sn-V active solder alloys on CVD diamond; while the original V content in Sn-V alloys has a negligible influence on final contact angles after wetting at 950 °C. The spreading kinetics of Sn-3V alloy on CVD diamond can be described using the classical chemical reaction-limited model at 700–850 °C. However, ultrafast adsorption of V element to the fresh diamond surface was evidenced by the formation of precursor film on the periphery of solidified Sn-V droplets. Hence, both interface reaction and adsorption of active element are accountable for the reactive spreading of Sn-V alloy on CVD diamond, especially during the early stage of spreading at relatively low temperatures. Results obtained in this study are therefore significant for not only the development of diamond bonding technique, but also the understanding of reactive wetting of metals on diamond and other carbonous materials.