Mechanism and parameter optimization of ultrasonic-assisted indium electroplating on Cu substrate

Indium (In) metal, valued for its high specific capacity and broad electrochemical stability window, has gained prominence in electrode material surface modification. Electroplating represents a cornerstone industrial technique for coating preparation. While ultrasonic fields are recognized as a transformative optimization strategy in electroplating processes, their application to In coatings remains underexplored, with systematic investigation into process parameters particularly scarce. This work investigates ultrasonic-assisted electrodeposition of In coatings on Cu substrates, and assesses how ultrasonic fields promote plating kinetics and the optimization of process parameters. Systematic exploration of key parameters—current density, NaCl concentration and pH—reveals their critical influence on coating morphology. The optimal process parameters for current density of 0.003 A/cm², pH of 1.5, and NaCl concentration of 0.4 mol/L were obtained. This work develops a comprehensive framework for ultrasonic-assisted In plating, delineating precise process parameters that yield high-quality coatings. The research elucidates the mechanistic pathways by which ultrasonic fields enhance ionic mass transfer and induce transitions in nucleation kinetics—from progressive to instantaneous—resulting in grain refinement and consequent improvements in coating surface morphology.