Analysis of Quadrol Additives in Pyrophosphate Copper-Plating Bath by Use of Boron-Doped Diamond Electrode
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-07-01 |
| Journal | Journal of The Surface Finishing Society of Japan |
| Authors | Taiga SAEKI, T. Onuki, Sachio YOSHIHARA, Yoshifusa ISHIKAWA, Kenichiro MOTOI |
| Institutions | Utsunomiya University |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study successfully utilized Boron-Doped Diamond (BDD) electrodes for the electrochemical analysis and potential quantification of Quadrol (an organic additive) in complex copper pyrophosphate plating baths.
- Core Value Proposition: BDD electrodes enable robust, selective analysis of organic plating additives due to their wide potential window, low background current, and superior chemical stability compared to traditional electrodes like Glassy Carbon (GC).
- Key Detection Signal: Quadrol oxidation was clearly observed via Cyclic Voltammetry (CV) at approximately 1.65 V vs. SCE on the BDD surface.
- Quantification Success: Linear Sweep Voltammetry (LSV) demonstrated a highly linear relationship (r2=0.9991) between current density and Quadrol concentration in the critical range up to 0.075 mol dm-3.
- Mechanism Insight: The oxidation mechanism on BDD is attributed to the generation of surface-bound hydroxyl radicals (OHâ˘), confirming BDDâs unique electrochemical pathway, which differs significantly from the direct electron transfer observed on GC.
- Kinetic Behavior: The reaction kinetics suggest that the Quadrol oxidation process is primarily diffusion-limited within the tested scan rate range (10-50 mV/s).
- Additive Selectivity: BDD successfully analyzed Quadrol even when competing additives (like L-histidine or N,N,Nâ,Nâ-ethylenediamine tetrakis-(methylenephosphonic acid)) were present, provided Quadrol oxidized at a less noble potential.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Electrode Material | Boron-Doped Diamond (BDD) | N/A | Working electrode |
| Substrate | Si (111) | N/A | BDD growth wafer |
| Boron Doping Concentration | 10,000 | ppm | B/C ratio for metallic conductivity |
| BDD Film Thickness | 20 | Âľm | Grown via MPCVD |
| Deposition Temperature | 700 | °C | MPCVD growth condition |
| Pyrophosphate K4P2O7 | 0.944 | mol dm-3 | Plating bath concentration |
| Copper Cu2P2O7â˘3H2O | 0.213 | mol dm-3 | Plating bath concentration |
| Quadrol Oxidation Potential (BDD) | 1.65 | V vs. SCE | Key analytical potential |
| Quadrol Oxidation Potential (GC) | 0.5 | V vs. SCE | Observed on Glassy Carbon |
| Linear Quantification Range | 0 to 0.075 | mol dm-3 | LSV range for concentration linearity (r2=0.9991) |
| Standard CV Scan Rate | 50 | mV/s | Electrochemical measurement speed |
Key Methodologies
Section titled âKey MethodologiesâThe analysis relied on the synthesis of high-quality BDD electrodes followed by standard electrochemical techniques in the plating solution.
-
BDD Electrode Fabrication:
- BDD films (20 Âľm thick) were grown on Si (111) wafers using Microwave Plasma Chemical Vapor Deposition (MPCVD).
- The films were heavily doped with Boron at a concentration of 10,000 ppm (B/C ratio) to achieve metallic conductivity.
- Deposition was performed at 700 °C and 70 Torr, utilizing H2 gas flow (300 sccm carrier, 3 sccm bubbling).
-
Electrolyte Preparation:
- The base electrolyte was a copper pyrophosphate plating bath (0.944 mol dm-3 K4P2O7, 0.213 mol dm-3 Cu2P2O7â˘3H2O).
- Quadrol was added at concentrations ranging from 0.025 mol dm-3 up to 0.15 mol dm-3 for quantification studies.
- Solutions were de-aerated using nitrogen gas for 20 minutes prior to measurement.
-
Electrochemical Measurements:
- A standard three-electrode cell configuration was used (BDD or GC working electrode, Pt mesh counter electrode, SCE reference electrode).
- Cyclic Voltammetry (CV): Used to determine the oxidation potential and mechanism, typically scanning from 0 V to 2.5 V vs. SCE at 50 mV/s.
- Scan Rate Dependence: CV was performed at varying scan rates (10, 30, 50, 70 mV/s) to confirm that the reaction was diffusion-limited (current proportional to the square root of the scan rate).
- Linear Sweep Voltammetry (LSV): Used for quantification, scanning from 0 V to 3.0 V vs. SCE at 50 mV/s. The resulting current density was plotted against Quadrol concentration to establish the calibration curve.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings support the use of BDD electrodes in industrial settings requiring precise control over organic chemical concentrations in aggressive environments.
- Electroplating Bath Control:
- Real-time monitoring and automated dosing of organic additives (brighteners, levelers, complexing agents like Quadrol) in high-speed copper plating lines.
- Maintaining optimal bath performance by preventing additive depletion or accumulation, which affects deposit quality (e.g., improving appearance under high current density).
- Advanced Chemical Sensing:
- Development of robust electrochemical sensors for quality control in chemical manufacturing, particularly for amine-based cross-linking agents used in polymers (polyurethane coatings and rigid foams).
- Environmental Monitoring and Remediation:
- Utilizing BDDâs ability to generate OH⢠radicals for the detection and electrochemical degradation of persistent organic pollutants (POPs) in industrial wastewater streams.
- High-Stability Analytical Tools:
- Application of BDD electrodes in analytical chemistry where high chemical resistance and a wide operating potential window are required, such as analyzing complex organic mixtures or highly corrosive electrolytes.
View Original Abstract
The purpose of this study is the use of boron-doped diamond ďźBDDďź electrodes for the electrochemical analysis of N,N,Nâ,Nâ-Tetrakis ďź2-hydroxypropylďź ethylenediamine ďźQuadrolďź as an additive in copper pyrophosphate plating baths. Actually, BDD is a quite new electrode material. Non-doped diamond shows electrical insulating properties, but its conductivity changes according to the doping concentration of boron from semiconductive, metallic conductive, to superconductivity. Moreover, BDD has unique electrochemical properties such as a wide potential window, low background current, and chemical stability. Metallic conductive BDD electrodes have been used for the electrochemical analysis of Quadrol additives. Earlier, we reported that Quadrol additives included in copper pyrophosphate plating baths had the effect of improving the appearance of thus-plated film, even under high current density. Cyclic voltammogram ďźCVďź measurements for Quadrol in a copper pyrophosphate plating bath using BDD or Glassy carbon ďźGCďź electrodes suggest that the BDD electrode showed anodic current, which was thought to be attributed to the oxidation of Quadrol at ca. 1.65 Vvs. SCE. Comparison with GC electrodes has clarified differences in the oxidation mechanism of Quadrol on each electrode. Furthermore, LSV measurements for BDD electrodes suggest the possibility of quantification of Quadrol in the bath.