The impact of lead-free manufacturing, as a result of the Waste Electrical and Electronic Equipment (WEEE) directive and Restriction on Hazardous Substances (RoHS), has changed surface finish specifications for PCBs and the soldering of those surfaces at assembly. Lead-free assembly has changed just about every aspect of the surface finish technology. The elimination of lead (Pb) in most designs has rendered the standard surface finish hot air solder level (HASL) increasingly obsolete. At assembly, the use of new solder alloys affects the compatibility of the finishes with the metallurgy of the final solder joint. Many of the assembly issues related to surface finishes, such as surface-mount technology (SMT) pad wettability, plated through hole (PTH) fill, and voiding are exacerbated by the Pb-free assembly process. Finally, the higher temperature of Pb-free soldering has a major impact on the shelf-life and solderability of the Pb-free finishes.

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