DISPERSOID ADDITIONS TO A PB-FREE SOLDER FOR SUPPRESSION OF MICROSTRUCTURAL COARSENING

The Bi-43%Sn eutectic solder alloy is a candidate for lead-free replacement of the widely used Pb-Sn solders. The alloy exhibits a microstructural instability at elevated service temperatures causing extensive coarsening and nonuniformity in microstructure and severe creep deformation. The addition of insoluble dispersoid particles using a novel magnetic distribution technique has been found to significantly reduce the coarsening and the onset of tertiary creep. With improved microstuctural stability, the useful service range of the Bi-Sn eutectic solder can be raised to a higher homologous temperature.