Bismuth stabilizer in an electroless Ni plating bath

Significance of the Topic

The electroless nickel plating process, widely used for printed circuit board finishing, provides exceptional wear and corrosion resistance. Precise control of stabilizer additives, such as bismuth, is essential to maintain bath stability and ensure high-quality coatings in ENIG and ENEPIG processes.

Objectives and Overview of the Study

This application note presents a straightforward voltammetric method for the determination of bismuth concentrations in electroless nickel plating baths. The approach aims to deliver fast, accurate, and robust measurements across a broad concentration range, suitable for manual and automated systems.

Methodology

The procedure involves adding water, plating bath sample, and supporting electrolyte into a measurement vessel. Bismuth levels are quantified by standard addition using the differential pulse mode:

• Deposition potential: –0.1 V
• Deposition time: 30 s
• Potential sweep: 0.0 V to 0.3 V
• Bi stripping peak at 0.15 V

The sensor is electrochemically activated before analysis. Two successive standard additions enable accurate concentration determination.

Used Instrumentation

• scTRACE Gold sensor: integrated working, reference, and auxiliary electrodes on a ceramic substrate
• 884 Professional VA system: voltammetric analyzer for manual or automated operation

Main Results and Discussion

Typical bismuth concentrations in nickel plating baths are around 1 mg/L. The described method reliably measures Bi from 100 μg/L to 1 mg/L with a 30 s deposition time. In a test sample containing 1 mg/L Bi, the measured value was 1.07 mg/L, demonstrating accuracy and reproducibility.

Benefits and Practical Applications

• Rapid analysis with minimal sensor maintenance (no polishing required)
• Wide dynamic range covering trace to mg/L levels
• Compatibility with automated sampling systems for real-time process control
• Enhanced quality assurance in plating bath management

Future Trends and Opportunities

Further development may include integration into fully automated inline monitoring platforms and coupling with data-driven bath management software. Expansion of the method to other plating bath additives and miniaturized sensor formats could broaden analytical capabilities in industrial settings.

Conclusion

The voltammetric approach using scTRACE Gold and the 884 Professional VA system offers a fast, reliable, and versatile solution for monitoring bismuth stabilizer concentrations in electroless nickel plating baths, supporting optimal process control and product quality.