Minimum effective Ni addition to SnAgCu solders for retarding Cu3Sn growth

The reactions between Cu and the Sn2.5Ag0.8Cu solders doped with 0, 0.005, 0.01, 0.03, 0.06, or 0.1 wt.% Ni were studied. Reaction conditions included multiple reflows and solid-state aging at 160 °C. The Ni additions produced much thinner Cu3Sn layers for all the Ni concentrations used. Ni concentration higher than 0.01 wt.% could effectively retard the Cu3Sn growth even after 2000 h of aging, and accordingly 0.01 wt.% can be considered the minimum effective Ni addition.