Brightener «InPulse H6» in acid copper baths (Atotech)

Importance of the Topic

In modern electroplating, maintaining consistent bath composition is critical to ensure uniform deposit quality, brightness and process efficiency. Organic brighteners such as InPulse H6 play a key role in refining deposit morphology and optical appearance of acid copper coatings. Precise quantification of brightener concentration directly impacts product consistency, minimizes waste and supports automated bath control in industrial settings.

Objectives and Study Overview

The primary goal of this application note is to present a reliable analytical protocol for determining InPulse H6 levels in acid copper plating baths. The study outlines the implementation of cyclic pulse voltammetric stripping (CPVS) combined with a modified linear approximation technique (MLAT) for sensitive and rapid brightener analysis.

Methodology and Instrumentation

The method requires no sample pretreatment. A working solution is prepared by mixing a defined volume of virgin make-up solution (VMS) containing CuSO₄, FeSO₄, Fe₂(SO₄)₃, H₂SO₄ and NaCl with the sample bath and a standard suppressor aliquot. Measurements employ a platinum rotating disk electrode (Pt-RDE) as working electrode, a platinum auxiliary electrode and an Ag/AgCl/KCl (3 M) reference electrode. Key CPVS parameters include:

• Equilibration potential: 0.45 V for 5 s
• Deposition potential: –0.20 V for 4 s
• Stripping potential: 0.25 V for 10 s
• Cleaning potential: 1.625 V for 5 s
• Rotation speed: 2000 rpm
• Data interval: 0.01 s

Main Results and Discussion

The CPVS curves exhibit well-defined stripping peaks proportional to InPulse H6 concentration. Applying MLAT facilitates linear calibration across the working range, ensuring accurate concentration read-out even in complex bath matrices. The method demonstrates good repeatability, low detection limits and rapid analysis (<1 min per sample).

Benefits and Practical Applications

This approach offers several advantages: rapid turnaround without chemical pretreatment, high sensitivity to low brightener levels, and compatibility with hydrodynamic measurement for improved signal stability. It can be integrated into quality control workflows for routine bath monitoring and automated process control in plating facilities.

Future Trends and Potential Applications

Advancements may include full automation of sampling and measurement, coupling with process control software for real-time bath adjustment, and adaptation to other plating chemistries. Integration with inline sensors could further enhance process efficiency and reduce manual intervention.

Conclusion

The described CPVS-MLAT method provides a robust, fast and precise tool for quantifying InPulse H6 brightener in acid copper baths, supporting reliable electroplating operations and consistent product quality.

Used Instrumentation

• Pt-RDE assembly (drive shaft 6.1246.000; Pt tip for CVS 6.1204.170)
• Auxiliary electrode Pt (6.0343.000)
• Reference electrode Ag/AgCl/KCl (3 M) with KNO₃ intermediate electrolyte (6.0728.020; 6.1245.010)