Suppressor «Cupraspeed» in acid copper baths (Atotech)

Significance of the Topic

Accurate determination of organic suppressors such as Cupraspeed in acid copper plating baths is critical for ensuring consistent deposit quality, uniform thickness, and desired surface properties in electroplating processes. Regular monitoring enables proactive bath maintenance, reduces defects, and supports cost-effective production in electronics and decorative plating industries.

Study Objectives and Overview

This application note presents a rapid analytical approach combining dilution titration (DT) with cyclic voltammetric stripping (CVS) to quantify Cupraspeed directly in an acid copper electroplating bath. The method aims to deliver reliable, in-line measurements without extensive sample preparation, facilitating routine quality control.

Methodology and Instrumentation

The procedure uses a virgin make-up solution (VMS) containing CuSO4, H2SO4, and NaCl as the background electrolyte. No sample pretreatment is required beyond dilution. Key electrochemical components include:

• Working electrode: platinum rotating disk electrode (Pt-RDE, rotor speed 2000 rpm)
• Auxiliary electrode: platinum wire
• Reference electrode: Ag/AgCl/KCl (3 mol/L) with intermediate KNO3 solution

Cyclic voltammetric stripping parameters:

• Initial and final potentials: 1.575 V
• First and second vertex potentials: -0.25 V and 1.575 V
• Voltage step: 0.006 V; sweep rate: 0.1 V/s
• Evaluation based on peak current ratio Q/Q(0) at 0.7; copper peak at 0.2 V ± 0.2 V
• Calibration via incremental dilution titration of suppressor

Main Results and Discussion

The CVS titration produced well-defined copper stripping peaks whose charge diminished proportionally with increasing suppressor concentration. A linear relationship between the charge ratio Q/Q(0) and the added volume of Cupraspeed was demonstrated up to approximately 0.52 mL in 100 mL of VMS. Repeatability tests showed relative standard deviations below 5%, indicating robust precision. Detection limits correspond to suppressor levels relevant for bath maintenance.

Benefits and Practical Applications

The combined DT-CVS method offers several practical advantages:

• Minimal sample handling and no complex pretreatment
• Rapid turnaround (~minutes per analysis)
• High sensitivity to suppressor levels affecting plating system performance
• Compatibility with routine QA/QC workflows in plating facilities

Future Trends and Possibilities

Extensions of this approach may include:

• Automation of titration and voltammetric measurements for inline monitoring
• Miniaturized sensor arrays enabling multiplexed analysis of multiple bath additives
• Integration with digital process control systems for real-time bath condition adjustments
• Application to other organic additives such as brighteners and levelers in diverse plating chemistries

Conclusion

The described dilution titration coupled with cyclic voltammetric stripping provides a fast, reliable, and sensitive method for quantifying Cupraspeed suppressor in acid copper baths. Its simplicity and compatibility with existing electrochemical instrumentation make it an attractive tool for industrial plating quality control.