Suppressor «InPulse H6» in acid copper baths (Atotech)

Importance of the Topic

Electroplated copper layers play a crucial role in electronics manufacturing, corrosion protection, and decorative finishes. Suppressor additives like InPulse H6 regulate deposit morphology, throwing power, and internal stress. Accurate monitoring of suppressor concentration in acid copper baths ensures consistent layer quality, extends bath life, and reduces production costs by avoiding overuse or premature bath replacement.

Study Objectives and Overview

The primary goal of this work was to establish a reliable and straightforward procedure for quantifying the suppressor InPulse H6 directly in acid copper electroplating solutions. The study demonstrates a combined dilution titration (DT) and cyclic voltammetric stripping (CVS) approach that requires no sample pre-treatment, enabling rapid in-line or at-line quality control. Calibration and method validation were performed using a virgin make-up solution (VMS) with defined CuSO4, H2SO4, and NaCl content.

Methodology

The analysis involved incremental additions of suppressor to the measuring solution followed by CVS measurements. Key procedural elements:

• Measuring solution: 100 mL of VMS
• Calibration technique: dilution titration (DT) with standard suppressor doses
• Electrochemical mode: cyclic voltammetric stripping (CVS)
• Potential program: start at 1.575 V, scan to –0.25 V, return to 1.575 V, step 6 mV, sweep rate 0.1 V/s
• Evaluation metric: ratio Q/Q(0) at the Cu stripping peak (around 0.2 V ±0.2 V), with a response ratio of 0.65 used for quantification

Used Instrumentation

An RDE setup with platinum electrodes and an Ag/AgCl reference system was employed:

• Working electrode: Pt rotating disk electrode (drive shaft 6.1246.000; Pt tip 6.1204.160)
• Auxiliary electrode: Pt wire (6.0343.000)
• Reference electrode: Ag/AgCl/KCl (3 M) with KNO3 intermediate electrolyte (sat.:H2O 3:1, part no. 6.1245.010)
• Hydrodynamic conditions: 2000 rpm stirring

Main Results and Discussion

CVS responses showed a clear decrease in stripping charge (Q) with increasing suppressor concentration. The titration curve plotting Q/Q(0) against added suppressor volume exhibited a linear region suitable for calibration. Reproducibility was high, and the method allowed detection of InPulse H6 at concentrations relevant to standard bath maintenance.

The selected evaluation ratio (0.65) corresponded to a mid-titration point, minimizing effects of baseline drift and ensuring robust quantification across typical bath concentrations.

Benefits and Practical Applications

This analytical protocol offers:

• Minimal or no sample pretreatment
• Rapid turnaround (single measurement cycle)
• High reproducibility under routine plating conditions
• Compatibility with in-plant control systems

It supports QA/QC laboratories and plating process engineers in maintaining optimal suppressor levels, improving deposit uniformity, and reducing waste.

Future Trends and Opportunities

Advancements may include automated flow-injection CVS systems for continuous monitoring, integration with process control software for real-time adjustment of additive dosing, and adaptation to other suppressor families or alternative plating chemistries. Machine-learning algorithms could further enhance endpoint detection and data interpretation.

Conclusion

The dilution titration coupled with cyclic voltammetric stripping provides a fast, accurate, and user-friendly method for determining InPulse H6 suppressor in acid copper baths. Its simplicity and adaptability make it a valuable tool for industrial electroplating operations seeking to optimize bath performance.