Ni-Sn alloys are used usually as corrosion protective and sometimes as an alternative to decorative chromium coatings. Ni barrier between the Cu-based substrate and the Sn finish can temporarily prevent the appearance of Sn whisker growth in electronic components. Ni under layer serves as a barrier for Cu diffusion into Sn, causes Cu to dissolve into Ni at a much lower rate than into Sn, allows a certain amount of Sn to diffuse into the Ni layer developing tensile stress in the Sn layer, and delays the growth of Sn whiskers.
