Evaluation of Corrosion Resistance of Multilayered Sn/Ag3Sn Electroplating on Cu Alloys for Electric Connectors

The anti-corrosion performances of multilayered Sn/Ag3Sn films with Ag thickness of 50 nm on Cu alloy materials were evaluated through a sulfidizing test in (NH4)2Sx solutions and an aging test at 473 K up to 2000 h, comparing with a commercial pure Ag film and a conventional reflowed Sn film on Cu alloy materials. The multilayered Sn/Ag3Sn films succeeded in the accelerated sulfidizing test, with unchanged appearance and stable electrical contact resistance, even after immersion in a 0.2 ml/L (NH4)2Sx solution for 120 h. Moreover, the multilayered Sn/Ag3Sn films exhibited low and stable electrical contact resistances equivalent to as-plated samples even after heating at 473 K for 2000 h. The excellent corrosion resistance of the multilayered Sn/Ag3Sn films can be mainly ascribed to the chemical stable Ag3Sn covered with a thin Sn oxide film and the inward Ag diffusion that suppressing outward Cu diffusion during aging