Nanoparticles of the Lead-free Solder Alloy Sn-3.0Ag-0.5Cu with Large Melting Temperature Depression CHANG DONG ZOU, 1 YU LAI GAO, 1,4 BIN YANG, 1 XIN ZHI XIA, 1 QI JIE ZHAI, 1 CRISTINA ANDERSSON, 2 and JOHAN LIU 2,3 1.—Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai Univer- sity, Shanghai 200072, P.R. China. 2.—Department of Microtechnology and Nanosciences (MC2) & SMIT Center, Chalmers University of Technology, 412 96 Goteborg, Sweden. 3.—SMIT Center and School of Automation and Mechanical Engineering, Shanghai University, Shanghai 200072, P.R. China. 4.—e-mail: gaoyulai@163.com Due to the toxicity of lead (Pb), Pb-containing solder alloys are being phased out from the electronics industry. This has lead to the development and implementation of lead-free solders. Being an environmentally compatible material, the lead-free Sn-3.0Ag-0.5Cu (wt.%) solder alloy is considered to be one of the most promising alternatives to replace the traditionally used Sn-Pb solders. This alloy composition possesses, however, some weaknesses, mainly as a result of its higher melting temperature compared with the Sn-Pb solders. A possible way to decrease the melting temperature of a solder alloy is to decrease the alloy particle size down to the nanometer range. The melting temperature of Sn-3.0Ag-0.5Cu lead-free solder alloy, both as bulk and nanoparticles, was investigated. The nanoparticles were manufactured using the self-developed consumable-electrode direct current arc (CDCA) technique. The melting temperature of the nanoparticles, with an average size of 30 nm, was found to be 213.9°C, which is approximately 10°C lower than that of the bulk alloy. The developed CDCA technique is therefore a promising method to manufacture nanometer-sized solder alloy particles with lower melting tem- perature compared with the bulk alloy. Key words: Lead-free solder, melting temperature depression, nanoparticles, Sn-3.0Ag-0.5Cu INTRODUCTION Soldering is an indispensable technology used for the interconnection and packaging of electronic products. 1 For the last decades, Sn-Pb solder alloys have been the preferred interconnection materials used in such applications. This preference can be attributed to their numerous advantages, such as low cost, low melting temperature, good workability and ductility, excellent mechanical properties, and good soldering and wetting behavior on several substrate materials such as Cu, Ag, Pd, Au, and respective alloys. Increased environmental and health concerns regarding the toxicity of Pb have, however, lead many countries to legislate the ban of Pb from many electronic applications. The European legislation on the restriction of certain hazardous substances (RoHS) came into power in July 2006. The phase out of Pb-containing solder alloys is a worldwide initiative. 1–4 It is therefore of utmost importance for the electronics community to find appropriate substitutes to replace Sn-Pb solders. A wide variety of new lead-free solders have already been developed to meet this need, and many have been identified as promising substitutes to the conventional Sn-Pb solders. Limitations such as high melting temperature and poor wetting and solderability still restrict, however, an extensive (Received April 21, 2008; accepted October 3, 2008; published online October 30, 2008) Journal of ELECTRONIC MATERIALS, Vol. 38, No. 2, 2009 Regular Issue Paper DOI: 10.1007/s11664-008-0591-4 Ó 2008 TMS 351