Determination of suppressor with CVS using the calibration technique «smartDT» with dynamic addition volumes

Importance of the topic

The accurate determination of suppressor additives in acid copper plating baths is critical for process control in electroplating industries. Suppressors such as polyethylene glycol (PEG) influence deposit morphology and thickness. Traditional dilution titration with fixed addition volumes is time-consuming and may sacrifice accuracy near the end point. The smartDT calibration technique adjusts addition volumes dynamically, improving precision and reducing analysis time.

Objectives and study overview

This bulletin presents an application of the smartDT method for electrochemical quantification of suppressor in acid copper baths by cyclic voltammetric stripping (CVS). Key aims include:

• Implementing variable addition volumes calculated in real time
• Comparing time savings versus classic titration
• Demonstrating method suitability for semiautomated and fully automated systems

Methodology and instrumentation

The dynamic titration technique is integrated into the viva 1.1 (or higher) software environment.

• Electrodes: 2 mm Pt rotating disk (RDE), Pt auxiliary rod, Ag/AgCl reference
• Instrument: 894 Professional CVS (semiautomated) with 800 Dosino for dispensing
• Reagents: CuSO4·5H2O (60 g/L), H2SO4 (130 mL/L), NaCl (50 mg/L), PEG6000 standard
• Sample: Virgin make-up solution (VMS) or plating bath aliquots
• CV parameters: 1.625 V start, –0.175 V vertex, 0.006 V step, 0.1 V/s sweep rate, two measuring cycles
• Calibration: Dilution titration (DT) with evaluation ratio set at 0.5

smartDT defines two user parameters: initial addition volume (ID4) and minimum addition volume (ID5). The software calculates intermediate additions based on the difference between standardized signal (AREANORM) and the evaluation ratio, applying an empirical factor to control step size.

Main results and discussion

Recoveries for PEG6000 standards ranged from 100.4 % to 104.7 %, demonstrating accuracy. Time savings versus classic DT were significant:

• Calibration (5 mL/L standard): classic DT 31 min vs. smartDT 21 min (32 % reduction)
• Sample 6 mL/L: classic 23 min vs. smartDT 17 min (26 % reduction)
• Sample 3 mL/L: classic 35 min vs. smartDT 23 min (34 % reduction)

The dynamic approach maintains high precision near the titration end point by reducing addition volumes as the signal approaches the evaluation ratio.

Benefits and practical applications

• Up to 40 % time savings in semiautomated workflows
• Improved end-point accuracy due to variable addition steps
• Compatibility with fully automated sample changers and various plating bath matrices (copper, tin, tin-lead)

Future trends and potential applications

Further developments may include integrating smartDT with advanced regression models, extending to online process monitoring and control in plating operations. Automation of parameter optimization and expanded applicability to other suppressor chemistries are promising directions.

Conclusion

The smartDT calibration technique for CVS titration of suppressors offers a robust, accurate and time-efficient alternative to fixed-volume dilution titrations. Its dynamic volume adjustment ensures precise end-point detection and significant labor savings, making it a valuable tool for QA/QC and research laboratories in electroplating industries.