Suppressor « Ronastan TP Additive» in a tin- lead bath Ronastan TP (Rohm and Haas Electronic Materials)

Significance of the Topic

Determining suppressor additives such as Ronastan TP in tin-lead plating baths is critical for maintaining uniform deposit thickness, preventing defects and ensuring consistent solderability in electronic component manufacturing. Rapid, reliable quantification of these organic compounds supports process control, reduces waste and improves product quality.

Objectives and Study Overview

The primary goal of this study was to establish a straightforward dilution-titration protocol combined with cyclic voltammetric stripping (CVS) for quantifying Ronastan TP Additive directly in a tin-lead bath. Key objectives included demonstrating linearity, sensitivity and practicality of the method under real-world plating conditions.

Methodology and Used Instrumentation

This approach employs a platinum rotating disk electrode (Pt-RDE) as the working electrode, a platinum auxiliary electrode and an Ag/AgCl/KCl (3 mol/L) reference system. The measurement solution is prepared by diluting the tin-lead bath to a virgin make-up composition and adding incremental volumes of Ronastan TP standard. CVS parameters are:

• Rotation rate: 2000 rpm
• Scan mode: cyclic voltammetric stripping
• Calibration: dilution titration
• Potential range: +0.475 V → –0.625 V → +0.475 V
• Step size: 0.006 V
• Sweep rate: 0.08 V/s
• Evaluation ratio Q/Q(0): 0.5 at the Sn stripping peak (~–0.25 V ± 0.1 V)

Main Results and Discussion

Cyclic voltammograms recorded at increasing concentrations of Ronastan TP showed a systematic increase in the stripping peak current at –0.25 V, demonstrating clear sensitivity to additive level. A calibration plot of the charge ratio Q/Q(0) versus added Ronastan TP volume exhibited excellent linearity over the typical operating range (0–1.5 mL per 100 mL bath). Precision studies indicated relative standard deviations below 5 % for multiple replicate measurements, confirming method reproducibility.

Benefits and Practical Applications

• No sample pretreatment or complex extraction is required.
• Analysis time per determination is under 10 minutes.
• High throughput suitability for QA/QC in plating facilities.
• Minimal chemical waste compared to traditional titrations.
• Direct in-bath monitoring allows immediate process adjustments.

Future Trends and Opportunities

Integration of this CVS-based protocol into automated inline analyzers could enable real-time monitoring of additive levels. Expansion of the technique to other suppressor and brightener chemistries, coupled with chemometric data processing, promises enhanced multicomponent analysis. The trend toward Industry 4.0 and smart manufacturing further supports embedding electroanalytical sensors within plating equipment for closed-loop control.

Conclusion

The described dilution titration in conjunction with cyclic voltammetric stripping represents a robust, fast and accurate method for quantifying Ronastan TP Additive in tin-lead plating baths. Its simplicity and precision make it an ideal tool for routine process control in electronic plating operations.

Reference

VA Application Note No. V-144, "Suppressor Ronastan TP Additive in a tin-lead bath Ronastan TP," Rohm and Haas Electronic Materials, Version 1.0