The invention discloses a low-silver lead-free solder and a preparation method thereof. The low-silver lead-free solder consists of
metal element components including, by weight, Ag 0.1%-1%, Cu 0.1%-1%,
misch metal 0.01%-0.10% and the balance
tin, wherein Ce accounts for 50%, La accounts for 25%, Nd accounts for 15% and Pr accounts for 10% in the
misch metal. On the
metal purity aspect, Ce >= 99.99%, La>= 99.99%, Nd >= 99.99%, Pr >= 99.99%, and Sn, Ag and Cu are industrial refined raw materials. The low-silver lead-free solder does not contain lead and can meet the lead-free
welding requirement of electronic products.
Branch-shaped primary-phase
solid-liquid mixed
slurry is crushed in an acute stirring mode in the low-silver hypo eutectic
alloy solidification process, and a water-cooling
casting forming mode is adopted to improve
mechanical property, especially the
plastic property. A
rare earth alterant is adopted to achieve grain refinement, improve the wet performance of the solder and ensure long-term reliability of
welding points.