Abstract: The electromigration (EM) of Sn96Ag3.5Cu0.5 solder interconnects is studied with Ni diffusion-barrier layers.The results show that at 180℃,intermetallic-compounds (IMCs) move in the direction of electron-flow and their evolution pre-sents a unique polarity effect.IMCs ripen,split,and migrate from the Ni/solder interface at the cathode,while accumulate at the anode area nearby.This IMC migration generates mass depletion at the cathode,which causes void nucleation and propagation on the UBM/solder interface.Large voids increase the measured resistance and deteriorate the conductive path noticeably,thereby seriously degrade the solder interconnect reliability.

Key words: electromigration, lead-free solder, solder interconnect, intermetallic compound