Brightener «Cupraspeed» in acid copper baths (Atotech)

Significance of the Topic

Monitoring the concentration of organic brighteners such as Cupraspeed in acid copper electroplating baths is critical to maintain deposit brightness, grain structure and uniformity.
Effective control of additive levels ensures consistent plating performance and reduces waste.

Objectives and Study Overview

The primary aim of this work is to develop a rapid, reliable analytical procedure for quantifying Cupraspeed brightener in acid copper plating solutions.
Key points:

• Application of cyclic voltammetric stripping (CVS) combined with a modified linear approximation technique (MLAT).
• Direct analysis of plating bath samples without elaborate pretreatment.
• Establishment of a calibration protocol to relate electrochemical signals to additive concentration.

Methodology and Instrumentation

Samples comprised a virgin make-up solution and real bath liquor spiked with known volumes of Cupraspeed.
A dedicated intercept solution was prepared by mixing the virgin make-up matrix with a defined volume of the brightener.
For sample analysis, 10 mL of plating bath was combined with 0.5 mL Cupraspeed suppressor and measured directly.
Electrochemical measurements employed cyclic voltammetry in stripping mode to induce additive-specific current responses.

Instrumentation Used

• Working Electrode: Platinum rotating disk electrode (Pt-RDE) with shaft and Pt tip.
• Auxiliary Electrode: Platinum wire.
• Reference Electrode: Ag/AgCl/KCl (3 mol/L) with saturated KNO₃ intermediate electrolyte.
• Rotational speed: 2000 rpm.
• Voltammetric Mode: Cyclic voltammetric stripping.
• Calibration Method: Modified linear approximation technique (MLAT).
• Potential Program: Start at 1.575 V, sweep to –0.175 V and back at 0.08 V/s with 6 mV steps.

Main Results and Discussion

The cyclic voltammograms exhibited reproducible stripping peaks around 0.2 V corresponding to Cupraspeed oxidation.
Application of MLAT to the integrals of the current-potential curves (Q–Q′ intercept) produced a linear relationship with the additive concentration from approximately 0 to 1 mL/L.
Calibration plots showed high linearity and minimal scatter, demonstrating the method’s suitability for routine bath monitoring.
No significant matrix interferences were observed in the acid copper environment under the chosen conditions.

Benefits and Practical Applications

• Rapid analysis without sample pretreatment, enabling on-line or at-line monitoring.
• High selectivity for Cupraspeed in complex copper plating matrices.
• Quantitative performance supports process control and quality assurance.
• Reduction of chemical waste by precise additive dosing.

Future Trends and Potential Applications

The technique can be adapted for other organic additives in metallization baths.
Integration with automated electrochemical analyzers could provide real-time process feedback.
Further enhancements in detection limits may be achieved through electrode surface modification or advanced signal processing.

Conclusion

The modified CVS-MLAT method offers a straightforward, accurate approach to determine Cupraspeed brightener levels in acid copper plating baths.
Its simplicity and robustness make it a valuable tool for industrial electroplating facilities aiming to optimize deposit quality and operational efficiency.