Design of Experiments Informed Investigation of Magnetic Field-Assisted Nickel Electroplating on Copper

Abstract

Nickel coatings have demonstrated significant benefits in protecting copper from oxidation and fouling, thereby enhancing the longevity of copper-based components. This study employed an electroplating apparatus featuring a Watts bath and copper electrode to investigate the impact of flowing electrolyte, both with and without an applied magnetic field, on the interfacial characteristics of nickel-coated copper surfaces. The findings reveal the relationship between current density and deposition thickness. The application of a perpendicular magnetic field and increase in current density generally increased coating thickness to 0.2 μm from 0.05 μm, with the most pronounced effects at moderate flow rates and narrower gaps; however, at the highest flowrate and widest gap, deposition thickness diminished due to the divergence of magnetic field lines. Design of experiments (DOE) analysis revealed that the magnetic field homogeneously improved surface roughness uniformity compared to other variables. Lower current densities produced smoother surfaces, while magnetically assisted electroplating yielded consistent roughness values even at higher current densities. Exposure to the magnetic field improved wettability, evidenced by decreased contact angles. This enhancement is attributed to the alignment of nickel particles during deposition, facilitating a transition from the Cassie-Baxter to the Wenzel wetting state. Notably, thicker deposits were observed at lower flow rates and narrower electrode gaps, suggesting significant influence of gas bubble dynamics on the deposition process. These findings provide insights into the complex interplay between electrochemical reactions, hydrodynamics, and magnetic fields in nickel electrodeposition, with implications for optimizing coating.