Electroless Sn-Ag Alloy Plating by Displacement Reaction

Abstract

Electroless Sn-Ag alloy plating by the displacement reaction was investigated. A new bath containing potassium pyrophosphate, potassium iodide, metal salts, and thiourea was used. First, examinations of electroless Sn plating and electroless Ag plating were carried out, and then electroless Sn-Ag alloy plating was investigated. Anodic and cathodic polarizations were conducted to clarify the deposition mechanism. Sn-Ag alloy films with a range of Ag concentrations from 24 to 52 at.% were obtained. The surface morphology of the films became smoother with decreasing Ag content. The Sn-Ag alloy films consisted of the β-Sn phase and the ε (Ag3Sn) phase.