Suppressor «Top Lucina α-M» in acid copper baths (Okuno Chemical Industries)

Importance of the Topic

Acid copper electroplating is a cornerstone of electronics manufacturing and decorative metal finishing. Suppressor additives such as Top Lucina α-M play a critical role in regulating deposit thickness, surface smoothness, and throwing power. Reliable quantification of these polymeric suppressors is essential to ensure consistent bath performance and product quality.

Objectives and Study Overview

This study presents a rapid and accurate approach for determining the concentration of Top Lucina α-M in acid copper plating baths. By combining cyclic voltammetric stripping (CVS) with a dilution titration (DT) calibration, the method aims to offer straightforward implementation for routine quality control.

Methodology and Instrumentation Used

No sample pretreatment is required; the bath solution is analyzed directly in a virgin make-up solution (VMS) containing CuSO4, H2SO4, and NaCl at supplier-specified levels. Key instrumentation and parameters include:

• Electrochemical cell volume: 50 mL VMS
• Working electrode: Platinum rotating disk electrode (drive shaft 6.1246.000 with Pt tip 6.1204.160)
• Auxiliary electrode: Platinum rod (6.0343.000)
• Reference electrode: Ag/AgCl/KCl (3 M) system with KNO3 intermediate (6.1245.010)
• Hydrodynamic stirring rate: 2000 rpm
• Measurement mode: Cyclic voltammetric stripping
• Calibration technique: Dilution titration
• Potential sweep: 1.625 V → –0.175 V → 1.625 V, step 6 mV, scan rate 0.1 V/s
• Evaluation metric: Stripping charge ratio Q/Q(0) set at 0.5

Main Results and Discussion

Cyclic voltammograms exhibit a well-defined copper stripping peak at approximately 0.2 V. Incremental additions of suppressor lead to a proportional decrease in the stripping charge. The dilution titration calibration curve of Q/Q(0) versus suppressor volume displays linear behavior up to 0.40 mL, enabling precise quantification under typical bath conditions.

Benefits and Practical Applications

• Eliminates complex sample preparation and accelerates analysis time
• Delivers high selectivity and sensitivity for polymeric suppressors
• Facilitates routine QA/QC monitoring to maintain stable plating performance

Future Trends and Opportunities

Integration of on-line electrochemical sensors and automated dilution titration modules promises real-time suppressor monitoring and feedback control. Further developments in miniaturized CVS systems and data analytics could enhance process optimization, reduce chemical waste, and support Industry 4.0 initiatives.

Conclusion

The combined cyclic voltammetric stripping and dilution titration method offers a robust, reproducible, and efficient solution for measuring Top Lucina α-M in acid copper baths. Its simplicity and accuracy make it ideally suited for industrial applications in plating process control.

References

• Okuno Chemical Industries. VA Application Note No. V-182, Version 1.0.