XPS, ToF SIMS and wettability analyses on Ni surfaces after Ar-H2 RF plasma treatment: An efficient and optimized plasma treatment approach

Abstract

Electroless Ni plating is widely used for its properties such as wear resistance, uniform coating and excellent brazing and solderability. In electronic and mechatronic applications, the chemical composition of the Ni layer and its surface quality still remains elusive and improvisation of Ni layer surface quality is vital. This research work investigates the surface properties of Ni films subjected to Ar-H2 RF plasma treatment. Plasma treatment parameters are defined by utilizing D-Optimal design of experiments. A precise mapping of the evolution of Ni surface global chemical composition is obtained using an XPS. Principal component analysis on XPS mapping coupled with 3D ToF-SIMS chemical cartography enables precise identification of the different oxidation states of nickel and their distribution in the plasma-treated nickel samples. The nickel surface wettability is then determined using the classical sessile drop technique. The findings of the study enable to define the plasma optimal power and accomplish the best compromise between the positive effects of the surface decontamination and the negative effects of the surface recontamination. The optimized plasma treatment succeeds to modify the surface nature of the nickel from hydrophobic to strongly hydrophilic. It demonstrates that the Ar-H2 plasma treatment is a very efficient process to increase the Ni surface wettability and thereby to improve the electronic and mechatronic assembly processes.