Leveler «Thru-Cup EVF-R» in acid copper baths (Uyemura)

Significance of the topic

Control of additive concentrations in copper electroplating baths is critical for achieving uniform deposit quality, preventing defects and ensuring process reproducibility. The leveler “Thru-Cup EVF-R” plays a key role in smoothing deposits at the microscale. A fast, reliable analytical method enables operators to monitor and adjust leveler concentration in real time, improving yield and reducing waste.

Objectives and overview

This study presents a procedure for quantifying the organic leveler Thru-Cup EVF-R in acid copper plating baths. The main goals are to establish a calibration protocol using response curve (RC) calibration and to demonstrate the application of cyclic voltammetric stripping (CVS) on a rotating disk electrode for direct analysis of industrial bath samples without additional preparation.

Methodology and instrumentation

The analysis employs CVS under hydrodynamic conditions with the following setup:

• Working electrode: Platinum rotating disk electrode (Pt-RDE) with a Pt tip for stripping measurements.
• Auxiliary electrode: Platinum wire.
• Reference electrode: Ag/AgCl in 3 mol/L KCl, with an intermediate KNO₃/H₂O bridge solution (3:1).
• Electrolyte solution: 20 mL virgin make-up solution (CuSO₄, H₂SO₄, NaCl per supplier specs) + 0.4 mL brightener EVF-1A + 0.4 mL suppressor EVF-B + sample aliquot.
• Hydrodynamic conditions: 2 600 rpm rotation speed.
• CVS parameters: potential range 1.625 V → –0.175 V → 1.625 V; step 6 mV; sweep rate 0.1 V/s; calibration by response curve technique.

Main results and discussion

Cyclic voltammograms show a well-defined copper oxidation peak around 0.2 V (±0.3 V), whose current magnitude varies linearly with EVF-R concentration. The RC calibration provided accurate quantification down to the typical operating range of the leveler. The absence of sample pretreatment minimized analysis time and avoided matrix alteration. Reproducibility was confirmed by repeated measurements on fresh and used bath samples.

Benefits and practical applications

• Rapid, in-situ quantification of leveler without complex sample preparation.
• High sensitivity and linearity enable detection at process-relevant concentrations.
• Hydrodynamic CVS reduces surface fouling and improves signal stability.
• Applicable for routine monitoring in plating shops and quality control labs.

Future trends and applications

Advances could focus on miniaturized potentiostats and flow-through cells for inline process control. Coupling CVS with chemometric models may allow simultaneous monitoring of multiple additives. Integration with automated feedback loops could optimize bath composition in real time and further reduce material consumption.

Conclusion

The described cyclic voltammetric stripping method with RC calibration offers a robust, fast and accurate tool for monitoring the leveler Thru-Cup EVF-R in acid copper plating baths. Its implementation supports improved process control and deposit quality in industrial electroplating operations.

Reference

Uyemura Application Note V-157, “Determination of leveler Thru-Cup EVF-R in acid copper baths by response curve technique using cyclic voltammetric stripping (CVS)”, Version 1.0.