A Novel Device for Plating Process Diagnostics ‘L-Cell’ A Novel Device for Plating Process Diagnostics L-Chem, Inc. Shaker Heights, OH 44120 www.L-Chem.com  

Introducing a novel, multi-purpose device that provides: Process parameters Process diagnostics Fully automated No expertise required Fast (2 min./test)

OUTLINE Rationalle and need Current tecnology and its defficiencies The L-Cell - principles and description Examples Conclusions

Issues in Plating Predictive Design Meeting Specs., Optimization Process Control and Maintenance Environmental and Health New Materials

} L-Cell Available Tools FUTURE: PAST: Predictive Design Optimization Process Control } Computer Aided Design Software - ‘Cell-Design’ PAST: L-Cell FUTURE: Hull-Cell Electroanalytical Techniques- Polarization studies Conductivity Titration (reactant conc.)

Limitations of CAD Software INPUT Cell configuration Cell Anodes Racks and Shields OUTPUT Current distribution Deposit thickness distribution Potential distribution Overpotential (polarization) Parasitic reaction rates Alloy composition Part’s evolving shape Deposit texture Operating Conditions current or voltage (DC or Periodic) temperature flow Numerical ‘Solver’ Process Properties Electrode polarization Electrolyte conductivity Diffusivity Often Missing

Issues with Obtaining Process Data using Conventional Approach Strong dependence on trace additives Proprietary formulations Lack of fundamental mechanistic understanding Laboratory experiments often do not duplicate process conditions Flow dependence Cost: Potentiostat ~ $ 20,000 - 40,000 Rotating disk electrode ~ $ 10,000 PhD investigator ~ $ 100K/yr i V

Limitations of the Hull-Cell Qualitative Current distribution is inherently inaccurate – varies with material No quantitative data

The L-Cell Provides: Comprehensive electrochemical process parameters Polarization curves Kinetics parameters Conductivity Process diagnostics: Indication of process variation due to additives consumption contamination Tool for process adjustment using a small (50 ml) volume Sample plated at a number of different and precisely known current densities for visual and analytical off-line testing Composition of alloy – partial currents Thickness measurements – current efficiency as f(i) Fully automated, fast (2 min.) experiment designed for non-experts Equipment is relatively inexpensive

THE L-Cell – Principle of Operation Multi-electrode cartridge and a cell that allows a separate current feed to each segment Electronics to provide a different and precisely measured current density to each segment Automated data acquisition and analysis Plated cartridge with segmented electrodes Cross-section

The L-Cell: Table-top design

The multi-pin connector

The L-Cell: Table-top design

The L-Cell: Table-top design Watts Nickel Testing

Design of the L-Cell ‘Cell-Design’ Modeling Top View (cross-section): Anode: oxygen evolution Segmented cathode (plated cartridge) Current distribution – different between segments but uniform on each segment Potential distribution: Reference electrode

THE L-Cell – Analytical Approach Unknowns: Cathodic polarization curve: iK =f (hA) Cathodic overpotentials (i0, aC, aA) Conductivity Measure: Segmental current densities Voltages (including reference electrodes) Conductivity Voltage balances Across the cell Overpotentials Data analysis Butler-Volmer fit kinetics parameters (i0, aC, aA)

DATA ANALYSIS Butler-Volmer: Mass transport included: CE = CB CB CE (pure kinetics, No transport limitations) CE = CB Mass transport included: CB CE Here, i0 is measured at CB and:

DATA ANALYSIS Tafel approximation: Equivalent mass transport boundary layer thickness

DATA ANALYSIS ik = Equivalent pure ‘kinetics‘ current derived from the measured current density, i

The L-Cell System

DATA AQUISITION 0.18 1.25 1.09 29.0 18.1 14.2 8.3 5.0 22. 6 3.02

Cu deposition Copper sulfate 0.5 M pH=2 Polarization curve Kinetics Parameters

Cu deposition Copper sulfate 0.5 M pH=2 100 ppm PEG

Comparing two tests Cu deposition Copper sulfate 0.5 M pH=2 Compare with: 100 ppm PEG Pure Cu w/PEG

Specification of acceptable deviation w/PEG

Copper deposition from copper sulfate No additives; pH=2

Copper deposition from copper sulfate pH=2 No PEG 100 ppm PEG Log i [mA/cm2]

Nickel Deposition from a standard Nickel Watts Electrolyte Overpotential, η [V]

Nickel Deposition from a standard Nickel Watts Electrolyte Overpotential, η [V]

Wagner Number

Throwing Power

Summary - The L-Cell Provides: Process properties: Polarization, Kinetics, Conductivity Use ‘regular production’ solution By-pass specialized testing – no special expertise needed No need to scan v-i, or apply transients – use steady-state data Fast (2 min.), completely automated Produces deposit samples plated at different current densities Process diagnostics tool