Effects of Sodium Citrate Concentration on Electroless Ni-Fe Bath Stability and Deposition

In this research, electroless Ni-Fe bath stability and deposition characteristics were investigated for various sodium citrate concentrations. Complexing agents such as sodium citrate are one of the main components of such electroless plating baths. Since they could play various roles such as maintaining pH stability, preventing precipitation of metal salts, and reducing the concentrations of free metal ions, the concentration of complexing agents in the plating bath is an important parameter for electroless deposition processes. In this research, unstable baths were obtained for insufficient sodium citrate concentrations, and these phenomena were analyzed with ChemEQL. Moreover, the deposition characteristics of electroless Ni-Fe for under bump metallurgy diffusion barriers were also investigated using energy-dispersive spectroscopy and field-emission scanning electron microscopy.