Reliability issues of Pb-free solder joints in electronic packaging technology

At present, the electronic packaging industry is actively searching for Pb-free solders due to environmental concerns surrounding the Pb-containing solders. Due to the lack of reliability data, some electronics companies are reluctant to adopt Pb-free solders into their products. Hence, a review of the reliability issues of Pb-free solders is timely. We have selected three topics to be reviewed here. They are interfacial reaction between Pb-free solder and thin film under-bump metallization, electromigration in Pb-free flip chip solder joints, and Sn whisker growth on the Pb-free finish on a Cu leadframe.