Suppressor «Cupracid BL-CT» in acid copper baths (Atotech)

Importance of the topic

Accurate determination of suppressor concentrations in acid copper plating baths is critical for achieving uniform deposit thickness, preventing defects, and ensuring consistent performance in electronic and decorative applications. Monitoring additives such as Cupracid BL-CT helps maintain bath stability and product quality.

Objectives and overview of the study

This study presents a dilution titration method coupled with cyclic voltammetric stripping (CVS) to quantify the suppressor Cupracid BL-CT directly in acid copper electroplating solutions. The approach aims to deliver rapid, reliable results with minimal sample pretreatment.

Methodology and instrumentation

The procedure involves incremental dilution titration of a 50 mL acid copper bath (virgin make-up solution: CuSO4, H2SO4, NaCl per supplier specs) followed by CVS analysis at a rotating disk electrode (RDE). Key parameters include:

• Working electrode: Pt-RDE assembly (drive shaft and Pt tip)
• Auxiliary electrode: Pt counter electrode
• Reference electrode: Ag/AgCl/KCl (3 mol/L), with intermediate KNO3/H2O electrolyte
• RDE rotation speed: 2000 rpm
• CVS mode potentials: start at 1.575 V, cycle to –0.25 V and back, step 0.006 V, 0.1 V/s sweep rate
• Calibration via dilution titration, evaluating the charge ratio Q/Q(0) at a peak potential near 0.2 V

Main results and discussion

Cyclic voltammograms reveal distinct stripping peaks corresponding to copper deposition and dissolution processes modulated by the suppressor. The charge ratio Q/Q(0) decreases linearly with increasing titrant volume, providing a clear calibration curve for quantification. The chosen evaluation ratio of 0.75 defines the endpoint, enabling reproducible detection across the analytical range.

Benefits and practical applications

• No sample pretreatment required, reducing analysis time
• High sensitivity and selectivity for Cupracid BL-CT in complex copper baths
• Compact instrumentation suitable for laboratory and on-site quality control
• Cost-effective monitoring of plating baths to optimize additive usage

Future trends and potential applications

• Integration into automated inline analyzers for real-time bath management
• Extension of the CVS titration approach to other plating additives
• Miniaturized sensors for portable monitoring devices
• Advanced data analytics to predict bath lifetime and additive consumption

Conclusion

The dilution titration–CVS method offers a straightforward, precise, and rapid tool for quantifying Cupracid BL-CT suppressor in acid copper baths. Its minimal sample preparation and robust calibration make it an attractive solution for industry-scale quality control and process optimization.