Optimisation of indium electroplating performance in a sulphamate system with composite additives: a response surface methodology study

Indium, characterised by its low melting point and high electrical conductivity, is indispensable in electronic applications. However, indium electroplating faces poor surface quality and low deposition rate. This study introduces a composite additive formulation consisting of 1,4-butynediol and Gum Arabic to optimise the electroplating process. Single-factor experiments combined with the Response Surface Methodology (RSM) were employed to optimise the process parameters. Optimal conditions of adding 0.13 g L−1 1,4-butynediol and 0.16 g L−1 Gum Arabic, achieved a 13% higher deposition rate (24.9 μm h−1) and 34% lower Ra (9.168 μin (0.23 μm)). Microscopic characterisation revealed that the coating is primarily composed of In and Cu elements, with uniform and dense grains and no obvious pores. XRD reveals lattice expansion and (101)/(112) preferential growth. In summary, through the synergistic effect of compound additives, this study successfully optimised the sulphamic acid-based indium electroplating process. The findings provide critical theoretical insights and technological frameworks for indium coatings in electronics and protection.