The influence of copper nanopowders on microstructure and hardness of lead–tin solder

This paper presents the microstructure and hardness of composite solders obtained by the addition of nanopowders of copper to a conventional solder. Copper powders-reinforced lead (Pb)–tin (Sn) composite solders were prepared by thoroughly blending nano-sized copper powders (average powder particle size 100 nm) with a powder of a eutectic solder and using a water-soluble flux. The blended solder paste was melted and allowed to re-solidify in a crucible placed on a hot plate and maintained at a constant temperature. Optical microscopy observations revealed the as-solidified microstructure of the composite solder to be altered by the addition of nanopowders to the eutectic Sn–Pb solder. The copper powders precipitated as intermetallic compounds that were non-uniformly distributed through the microstructure. Microhardness measurements revealed a 30–40% increase in hardness of the composite solder over the conventional unreinforced eutectic counterpart. [Copyright &y& Elsevier]