Lead (Pb)-free solders for electronic packaging

The harmful effects of lead on the environment and human health, coupled with the threat of legislation, have prompted a serious search for lead-free solders for electronic packaging applications. At present, Sn-Pb eutectic and other Pb-containing solders find widespread use in printed circuit board assembly. Several Pb-free solder alloys which appear to have the potential for replacing Sn-Pb solders are receiving increased attention from the electronic assembly community. Recently, numerous studies have been published detailing the wetting characteristics, tensile and shear strength, and creep and low-cycle fatigue properties of these alloys. It is the purpose of this paper to review these results and assess the suitability of the solders for electronic packaging from the viewpoints of process technology and reliability.