Brightener «Thru-Cup EVF-1A» in acid copper baths (Uyemura)

Significance of the Topic

The control of organic brightener concentration in acid copper electroplating baths is critical for achieving uniform, high–gloss deposits in electronics and decorative industries. Precise quantification ensures process stability, reproducibility of plating thickness and appearance, and minimization of defects that can compromise product performance.

Objectives and Study Overview

This application note presents a rapid, sensitive method for determining the concentration of the proprietary brightener Thru-Cup EVF-1A in acid copper baths. The technique combines cyclic voltammetric stripping (CVS) with a modified linear approximation technique (MLAT) to deliver accurate results without extensive sample preparation or lengthy analysis time.

Methodology and Instrumentation

The analytical procedure is based on recording a cyclic voltammetric stripping signal of copper in the presence of the brightener. Key steps and solutions:

• Electrolyte formulation: Virgin make-up solution (VMS) containing CuSO₄, H₂SO₄, NaCl per supplier specs.
• Measuring solution: 45 mL VMS + 0.5 mL suppressor Thru-Cup EVF-B + 5 mL plating bath sample.
• Standard addition: Brightener EVF-1A diluted 1:5 with VMS.
• CVS parameters: Start at 1.575 V, sweep to –0.25 V and back, step 0.006 V, rate 0.1 V/s; hydrodynamic conditions at 2 000 rpm.
• Calibration: MLAT applied to stripping charge versus concentration plot for accurate quantification.

Used Instrumentation

• Working electrode: Pt rotating disk electrode (Pt-RDE).
• Auxiliary electrode: Platinum rod.
• Reference electrode: Ag/AgCl/KCl (3 mol/L) with KNO₃ intermediate electrolyte.
• Rotator drive and CVS module configured for hydrodynamic and voltammetric stripping measurements.

Main Results and Discussion

The CVS response exhibited a well-defined copper stripping peak around 0.25 V (±0.2 V). The MLAT calibration plot of net charge versus added brightener concentration demonstrated linearity over the working range, yielding a detection limit in the low mg/L region. Reproducibility was within ±3% RSD for replicate analyses, confirming method precision.

The approach effectively compensates for matrix effects by incorporating standard additions and a suppressor agent. Graphical evaluation of charge intercepts against concentration allowed reliable determination of unknown samples without extensive baseline correction.

Benefits and Practical Applications

The described method offers:

• Minimal sample preparation—direct analysis of plating bath samples.
• Rapid turnaround—complete measurement within minutes.
• High sensitivity and selectivity for the target brightener.
• Potential for in-line or at-line QA/QC monitoring in plating facilities.

Future Trends and Applications

Advances in microelectrode technology and automated CVS systems may further reduce sample volume and analysis time. Integration with digital data acquisition and process control software could enable real-time monitoring of brightener levels. Expanding the technique to multiplex detection of multiple organic additives offers prospects for comprehensive bath management.

Conclusion

The combination of cyclic voltammetric stripping and MLAT provides a robust, efficient tool for quantifying Thru-Cup EVF-1A brightener in acid copper baths. The method’s speed, accuracy and low sample preparation footprint make it well suited for routine quality control and process optimization in electroplating operations.

References

No literature cited in the source document.