Effect of indium content and rapid solidification on microhardness and micro-creep of Sn-Zn eutectic lead free solder alloy

摘要

The Sn-Zn alloys have been considered as lead-free solders. In this paper, the effect of 0.0, 0.5, 1.0, 1.5 and 2.0 wt.% Indium as ternary additions on melting temperature, structure, microhardness and micro-creep of the Sn-9Zn lead-free solders were investigated. It is shown that the alloying additions of Indium to the Sn-Zn binary system result in a suppression of the melting point to 187.9 °C. From x-ray diffraction analysis, a new intermetallic compound phase, designated β-In₃Sn is detected. The formation of an intermetallic compound phase causes a pronounced increase in the electrical resistivity and mechanical strength. Also, an interesting connection between dynamic Young's modulus and the axial ratio (c/a) of the unit cell of the β-Sn was found in which Young's modulus increases with increasing the axial ratio (c/a). The ternary Sn-9Zn-xIn exhibits creep resistance superior to Sn-9Zn binary alloy. The better creep resistance of the ternary alloy is attributed to solid solution effect and precipitation of In₃Sn in the Sn matrix. The addition of small amounts of In is found to refine the effective grain size and consequently, improves hardness. The 89%Sn-9%Zn-2%In alloy is a lead-free solder designed for possible drop-in replacement of Pb-Sn solders. (? 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)