Over the years, copper electroplating has emerged as a pivotal electrochemical process, extensively utilized in various industrial applications to enhance the surface characteristics of metallic substrates. Research efforts have predominantly focused on identifying the optimal combination of different parameters influencing the process such as temperature, electrolyte concentration, and complexing agent. However, there is a limited body of literature that specifically explores the electrochemical dynamics of copper electrodeposition at the electrode-electrolyte interface. The current study aims to explore the underlying mechanism of copper electrodeposition from a cyanide-free alkali medium using a solution consisting of copper sulfate, glycine (a complexing agent), and sodium hydroxide for pH control. Deposition was performed at − 560, − 660, and − 760 mV, with a detailed phase transformation analysis conducted via electrochemical impedance technique (EIS) under varying ion concentrations (0.01, 0.05, and 0.1 M) and temperatures (5°, 10°, 15°, and 20 °C). Initial cyclic voltammetry and potentiostatic studies suggest that the system did not undergo 3D nucleation and growth. Impedance analysis further revealed that at a low copper concentration (0.01 M), mass transfer kinetics likely dominated, as evidenced by the high charge transfer resistance (Rct = 114.2 Ω cm2) and the presence of Warburg resistance (W = 58.12 Ω cm2). Conversely, the higher charge transfer resistance observed with increasing potentials (Rct = 39.63 Ω cm2 at DP5 to Rct = 76.18 Ω cm2 at DP7) and decreasing temperatures (Rct = 18.88 Ω cm2 at T = 20 °C to Rct = 26.7 Ω cm2 at T = 5 °C) resulted in the formation of superior quality deposits, which likely included an outer oxide/hydroxide layer. X-ray diffraction confirmed the presence of copper oxide and hydroxide, while morphological analysis using FESEM and surface roughness measurements via AFM verified the formation of smooth uniform copper films. Based on impedance findings and morphological results, a plausible deposition mechanism has been proposed. Although, in this study, impedance analysis has been used to comprehend the electrochemical phenomena occurring at the electrode-electrolyte interface, EIS can also be used to further optimize film properties for specific applications.

Copper Electrodeposition from a Non-cyanide Glycinate Alkaline Bath under Varying Potential, Bath Concentration, and Temperature: An Impedance Analysis

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发表日期：

2025年5月8日

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Sudeshna Parida,
Rajath R. Mendon,
Sanskar Soven,
Sanjeev Das,
Archana Mallik

摘要

Over the years, copper electroplating has emerged as a pivotal electrochemical process, extensively utilized in various industrial applications to enhance the surface characteristics of metallic substrates. Research efforts have predominantly focused on identifying the optimal combination of different parameters influencing the process such as temperature, electrolyte concentration, and complexing agent. However, there is a limited body of literature that specifically explores the electrochemical dynamics of copper electrodeposition at the electrode-electrolyte interface. The current study aims to explore the underlying mechanism of copper electrodeposition from a cyanide-free alkali medium using a solution consisting of copper sulfate, glycine (a complexing agent), and sodium hydroxide for pH control. Deposition was performed at − 560, − 660, and − 760 mV, with a detailed phase transformation analysis conducted via electrochemical impedance technique (EIS) under varying ion concentrations (0.01, 0.05, and 0.1 M) and temperatures (5°, 10°, 15°, and 20 °C). Initial cyclic voltammetry and potentiostatic studies suggest that the system did not undergo 3D nucleation and growth. Impedance analysis further revealed that at a low copper concentration (0.01 M), mass transfer kinetics likely dominated, as evidenced by the high charge transfer resistance (R_ct = 114.2 Ω cm²) and the presence of Warburg resistance (W = 58.12 Ω cm²). Conversely, the higher charge transfer resistance observed with increasing potentials (R_ct = 39.63 Ω cm² at DP5 to R_ct = 76.18 Ω cm² at DP7) and decreasing temperatures (R_ct = 18.88 Ω cm² at T = 20 °C to R_ct = 26.7 Ω cm² at T = 5 °C) resulted in the formation of superior quality deposits, which likely included an outer oxide/hydroxide layer. X-ray diffraction confirmed the presence of copper oxide and hydroxide, while morphological analysis using FESEM and surface roughness measurements via AFM verified the formation of smooth uniform copper films. Based on impedance findings and morphological results, a plausible deposition mechanism has been proposed. Although, in this study, impedance analysis has been used to comprehend the electrochemical phenomena occurring at the electrode-electrolyte interface, EIS can also be used to further optimize film properties for specific applications.