Recent progress in the studies of low melting Sn-based Pb-free solders

Limited by the toxicity of Pb and Pb-containing compounds and the implementation of the mandatory legislations, such as WEEE and RoHS, the Pb-containing solders have been banned and accordingly the Pb-free solders have become popular in electronic industry. However, the novel developed Pb-free solders could cause a series of packaging defects such as delamination, cracking, and charring etc. due to the relatively high melting temperatures of these Pb-free substitutes compared to the former Sn-Pb.