Determination of nickel in electroless plating solutions

Importance of the topic

Reliable quantification of nickel in electroless plating baths is essential for maintaining deposit quality, bath stability and process efficiency in industrial plating operations. Thermometric titration offers a rapid, accurate and automated approach that is resilient to sample coloration and turbidity.

Objectives and study overview

This study demonstrates a straightforward thermometric titration method using disodium dimethylglyoximate to determine Ni(II) concentration in electroless plating solutions. The aim is to establish optimal titration parameters, validate method performance and apply it to real plating baths.

Methodology and instrumentation used

• Principle: Exothermic reaction between Ni(II) and dimethylglyoximate in an ammonia/ammonium chloride buffer. Two moles of DMG bind one mole of Ni(II), generating a detectable heat change at the endpoint.
• Reagents:
  • 0.5 mol/L disodium dimethylglyoximate titrant.
  • NH₃/NH₄Cl buffer prepared by dissolving NH₄Cl in concentrated ammonia and diluting to volume.
• Sample preparation: Pipette 0.3–1 mmol Ni(II) into the titration vessel, add buffer and deionized water to reach 35–50 mL total volume. Acidic samples must be pre-complexed with citrate before basification.
• Titration parameters: Titrant delivery at 2 mL/min; stirrer speed 10–12 rpm depending on suspension viscosity; single exothermic endpoint detection with a data smoothing factor of 55.
• Instrumentation: Automated thermometric titrator with temperature sensor (thermistor) and controlled titrant dosing. Routine cleaning of the sensor and vessel by soaking in 1 mol/L HCl.

Key results and discussion

Analysis of six independent aliquots of electroless plating solution yielded an average nickel concentration of 29.51 g/L with a relative standard deviation of 0.11 %. Thermometric titration curves showed a distinct temperature rise at the endpoint and clear inflection in the second derivative trace, illustrating precise endpoint detection and method reproducibility.

Benefits and practical applications

• Fast, automated measurements with minimal manual intervention.
• Robust endpoint detection unaffected by sample color or turbidity.
• High precision and low variability support stringent quality control.
• Simple maintenance and cleaning procedures enhance laboratory throughput.

Future trends and potential applications

• Integration into inline process monitoring for real-time bath composition control.
• Development of multi-element thermometric titration protocols for simultaneous analyses.
• Miniaturized, portable titration systems for field-based quality checks.
• Advanced software algorithms for enhanced endpoint recognition and predictive analytics.

Conclusion

Thermometric titration with disodium dimethylglyoximate provides a rapid, accurate and automated solution for nickel determination in electroless plating solutions. Its robustness and precision make it well suited for routine industrial quality control and process optimization.

References

Thermo. Titr. Application Note No. H-052: Determination of nickel in electroless plating solutions.