Novel Rare-Earth-Containing Lead-Free Solders with Enhanced Ductility

Several lead-free material systems are available as replacements for traditional lead-based solders in microelectronic packaging, including near-eutectic combinations of tin-rich alloys. Although these materials have superior mechanical properties as compared to the Pb-Sn system, much work remains in developing these materials for electronic packaging. Small additions of rare-earth elements have been shown to refi ne the microstructure of several lead-free solder systems, thus improving their mechanical properties. This study investigated the effect of the addition of lanthanum on the melting behavior, microstructure, and shear strength of an Sn-3.9Ag-0.7Cu alloy. The infl uence of LaSn 3 intermetallics on microstructural refi nement and damage evolution in these novel solders is discussed.