Theory and Practice of Metal Electrodeposition

Transcription

1 Theory and Practice of Metal Electrodeposition

2 Yuliy D. Gamburg Giovanni Zangari Theory and Practice of Metal Electrodeposition 1 3

3 Dr. Yuliy D. Gamburg Russian Academy of Sciences A.N. Frumkin Institute of Physical Chemistry and Electrochemistry Moscow Russia Dr. Giovanni Zangari University of Virginia Department of Materials Science and Engineering Charlottesville VA USA ISBN e-isbn DOI / Springer New York Dordrecht Heidelberg London Library of Congress Control Number: Springer Science+Business Media, LLC 2011 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper Springer is part of Springer Science+Business Media (

4 Preface The book reflects in a concise form the modern state of both theoretical and applied aspects of metal electrodeposition. The theoretical part concerns the electrochemistry of metals and includes a discussion of electrochemical thermodynamics and kinetics, the structure at the metal/electrolyte interface, nucleation, growth and morphology of metals and alloys, and current distribution. The applied part contains general information on the applications of metallic coatings, their selection, electrochemical basics and technology of deposition of selected metals and alloys, including individual peculiarities, properties and structure of coatings, testing and characterization. The book includes, where possible at an elementary level, a quantitative discussion of phenomena of relevance, providing formulas for the calculation of important quantities. Additionally, it contains information on surface leveling, hydrogenation, inclusion of impurities, physical properties of deposits, that is rarely available in textbooks on electrodeposition. The section on electrodeposition technology includes the most important processes and chemistries; information on any definite material system is provided using a unified scheme, namely: properties of the coating, advantages and disadvantages, solution chemistries and methods of preparation, peculiarities, anodes, and additives. The essential concepts in theoretical electrochemistry necessary for the investigation of metal deposition processes is provided here, including data that are commonly absent in specialized academic courses. These topics are important for the reader aiming to achieve a thorough understanding of the latest scientific publications in this field. Information on different aspects of the process of electrolytic crystallization is gathered here from a large body of publications and is considered from a unified point of view. The book is suitable for professional electrochemists, advanced undergraduate and postgraduate students and also for electrodeposition specialists with a physical, technical or chemical education. It can also be useful for engineers and specialists engaged in research on new electrodeposition technologies related to metallic layers, crystals and other metallic objects. One of the authors (Yu. Gamburg) is hugely grateful to his colleagues from the Laboratory of the surface layers structure (A. N. Frumkin Institute, Russian Academy of Sciences) and particularly indebted to Maria R. Ehrenburg who translated the chapters 10 and 11 written originally in Russian. v

5 Contents 1 Introduction to Electrodeposition: Basic Terms and Fundamental Concepts Electrodeposition of Metals Examples of Electrocrystallization Electrode Processes. Faraday s Law Current Density Electrodes and Electrode Potential Equilibrium Potential and Overpotential Mixed Potential Potential Current Curves (Voltammograms) Current Efficiency The Various Steps Occurring in Electrode Processes. Fast and Slow Steps Electrolytes Used for Electrodeposition The Influence of Deposition Parameters on Electrodeposition Processes Electric Conductivity of Solutions Composition, Structure and Properties of Deposits Current and Metal Distribution Anodic Processes References The Structure of the Metal-Solution Interface Introduction: Spatial Separation of Electric Charge Compact Part of the Double Layer: Helmholtz Layer Diffuse Layer: Gouy-Chapman Layer Adsorption at Electrodes Model Adsorption Isotherms Specific Adsorption Adsorption of Uncharged Organic Species Double Layer on Polycrystalline Solid Surfaces vii

6 viii Contents 2.8 Some Calculations of Double Layer Parameters References Electrochemical Thermodynamics and Electrochemical Kinetics Electrochemical Potential Equilibrium at Electrolyte-Solid Interfaces Electrode Potential. Nernst Equation Measurements of Electrode Potential Theory of Charge Transfer Exchange Current Density. Overpotential. Polarization Curves Multistep Electrochemical Processes Chemical Steps Ion Discharge Kinetics in Presence of Surface-Active Agents Peculiarities of the Discharge of Complexes References Influence of Diffusion on the Rate of Electrochemical Process Ion Transport and Current Diffusion Limiting Current Diffusion Overpotential Mixed Kinetics The Influence of the Electric Field on the Limiting Current Role of Diffusion in the Discharge of Complex Species Diffusion Layer on the Rotating Disc Electrode References Thermodynamics and Kinetics of Nucleation Introduction Homogeneous Nucleation Heterogeneous Nucleation Three-Dimensional Nucleation Two-Dimensional Nucleation Nucleation Mechanisms The Peculiarities Of Electrocrystallization The Partition Function For the Nuclei Size Distribution The Steady State Nucleation Kinetics Fokker Planck Equation The Non-Equilibrium Flux An Estimate of the Steady State Flux Peculiarities of the Steady State Flux Result Non-Steady State Nucleation Experimental Methods Kinetics of Mass Crystallization

7 Contents ix 5.11 The Growth of an Individual Hemispheric Oluster Under Mixed Control The Nucleation and Growth With Overlap References Morphology of the Growing Metal Surface Steps and Kinks Adatoms and Adions Normal Growth and Layer-by-Layer Growth The Rate of Normal Growth Rate of Step Propagation During Layer-by-Layer Growth Nucleation Rate Distribution Between Growth Steps Influence of Adsorption on the Rate of Crystallization Ohmic Drop Near a Growing Step Grain Size of Deposits as a Function of Overpotential Morphological Features of Compact Electrodeposits The Morphological Types of the Deposit Surface Pyramids and Spirals Layered or Lamellar Morphology, and Other Morphological Types On the Nature of Macrosteps Crystalline, Irregular Roughness References Potential Distribution in the Electrolyte and Current Distribution on the Electrode Surface Statement of the Problem Primary, Secondary and Limiting Field Distributions. Polarization Fields Basic Principles of Calculation of Electric Fields in the Electrochemical Cells Typical Examples of Primary and Secondary Current Distribution The Strip-Shaped Cathode; Primary Current Distribution (PCD) The Disc Electrode; PCD Gap Cells and Angular Cells with Linear Cathodes; PCD The Cylindrical Cathode The Sinusoidal Profile; PCD Arbitrary Case; PCD Arbitrary Case; Secondary Current Distribution (SCD) The General Case Throwing Power of Electrolytes and Polarizability of Electrodes. Standard Definition of Throwing Power Throwing Power and Cathodic Polarization. Methods for Improvement of Current Distribution

8 x Contents 7.7 Current Distribution on Microstructured and Nanostructured Electrodes: Through-Mask Electrodeposition Current Distribution at the Workpiece Scale Current Distribution at the Pattern Scale Current Distribution at the Feature Scale References Current Distribution at Rough Electrodes Introduction Coefficient of Current Distribution and the Basic Problem of Microdistribution Geometric Leveling Microprofile Evolution as Result of a Non-Uniform Primary Current Distribution Roughness Evolution Under Secondary and Tertiary Current Microdistribution True Leveling Stability of the Growth Front During Electrocrystallization Bright Deposits References Non-steady State Electrodeposition Processes and Electrochemical Methods Non-steady State Diffusion On Off Switching of the Current or Overpotential Superposition of a Sinusoidal Current Steady State and Pulsating Diffusion Layers Rectangular Pulses Role of the Pause and of the Anodic Period Current Distribution, Current Efficiency and Inclusions of Impurities During Non-steady State Processes Linear Current or Potential Scans; the Optimum Sweep Rate for the Acquisition of Polarization Curves References Electrodeposition of Alloys Introduction Applications of Electrodeposited Alloys Partial Polarization Curves for Alloy Components Construction of Partial Curves Depolarization and Overpolarization Conditions for Alloy Formation Structure Types of Electrodeposited Alloys Phase Diagrams of Alloys

9 Contents xi 10.7 Alloys of the Mechanical Mixture Type Alloys of the Solid Solution Type Underpotential Metal Deposition and Cathodic Metal Intercalation into a Foreign Substrate Formation of Solid Solutions Intermetallic Compounds and Amorphous Alloys Equilibrium and Steady-State Potentials of Alloys Accounting for the Energy of Alloy Formation in Calculations of Potentials of Alloy Deposition Nucleation and Growth of Metal Clusters on a Foreign Substrate upon Electrodeposition of an Alloy of the Mechanical Mixture Type Effect of Various Factors on Alloy Composition Electrodeposition of Multilayer and Surface Alloys Multilayer Alloys Surface Alloys References Codeposition of Impurities Sources of Impurities in Electrodeposits Theoretical Analysis of the Codeposition Kinetics Adsorption Equilibrium Capture of Adsorbed Species Mass Transport of Impurities to the Cathode Derivation of the Main Equation Limiting and Intermediate Cases Adsorption Control of Codeposition Diffusion Control of Incorporation The Case of Mixed Control Dependence of the Concentration of Impurities on Electrodeposition Conditions Dependence on the Current Density Dependence on the Impurity Concentration in Solution Dependence on Temperature Factors Complicating the Codeposition Kinetics Chemical State of Codeposited Impurities The Incorporation of Inhibitors Into the Deposit and Inhibition of the Electrodeposition Process Hydrogenation of Deposits Mechanisms of Substrate Hydrogenation Hydrogen Permeability of Membranes Conclusion References

10 xii Contents 12 Technologies for the Electrodeposition of Metals and Alloys: Materials and Electrolyte Selection, Substrate Preparation Materials Selection Decorative Properties: Au, Ag, Rh, Pt, Ni, Cr, Ni Sn Enhancing Solderability and Welding: Sn Alloys, Ni, Cu, Au, Pd Antifriction Properties: Pb or Sn Alloys, In, Au Corrosion Protection: Zn, Sn, Cd, Ni, Zn Ni, Pd, Ag, Ag Pd, Au Electrical Contacts and Conductivity: Cu, Ag and Its Alloys, Au and Its Alloys, Pd, Ni, Sn, Sn Pb Hardness and Wear-Resistance: Cr, Ni, Ni W, Ni B, Rh, Sn Alloys Miscellaneous Properties Deposit Thickness Selection of the Electrolyte Chemical and Electrochemical Degreasing Pickling Additional Treatments References Technologies for the Electrodeposition of Metals and Alloys: Electrolytes and Processes Deposition of Copper and Its Alloys Properties and Fields of Application of Copper Deposits Solutions for Copper Deposition Copper Plating for Semiconductor Interconnects Solutions Make Up and Purification Mechanism and Kinetics of Deposition Peculiarities, Anodes, and Additives. Removing Deposits of Poor Quality Brass, Bronze and Copper Nickel Alloys Plating Silver and Its Alloys with Sb, Cu and Pd Properties and Applications of Silver Deposits Solutions for Silver Deposition Solutions Make Up and Purification The Mechanism of Silver Deposition Peculiarities; Anodes; Additives The Silver Alloys with Antimony, Copper or Palladium Electrodeposition of Gold and Its Alloys Properties and Applications for Gold Coatings Solution Chemistries, Compositions and Operating Conditions Solutions Make Up Peculiarities; Anodes; Impurities; Correction Electrolytes for Gold Alloys Deposition

11 Contents xiii 13.4 Electrodeposition of Zinc and Its Alloys Properties and Applications Electrolyte Formulations and Operating Conditions Electrolyte Preparation The Peculiarities; Anodes; Removal of Zinc Coatings Electrolyte Corrections The Additives for Zinc Deposition Zinc Alloys Plating Electrodeposition of Nickel and Its Alloys Properties, Applications and Peculiarities Electrolyte Formulations Solutions Make Up and Purification Anodes Correction and Elimination of Harmful Impurities Electrodeposition of Nickel Alloys Chromium Electrodeposition Properties and Applications Bath Compositions Preparation of the Electrolytes Peculiarities Anodes Electrolyte Correction Trivalent Electrolytes Iron and Its Alloys Electrodeposition of Soft Magnetic Materials Low-Melting Metals: Bi, Cd, In, Pb, Sb, Sn. The Alloy Sn Pb Bismuth Cadmium Indium Lead Antimony Tin Tin Lead, Tin Bismuth, and Tin Zinc Alloys Platinum Metals: Pd, Pt, Rh Palladium Platinum Rhodium Troubleshooting Electroplating Operations: Some Possible Reasons for Poor Deposit Quality References Structure and Microstructure of Electrodeposited Metals and Alloys Formation of the Polycrystalline Metal Grain Boundaries

12 xiv Contents 14.3 Stacking Faults and Twin Boundaries Dislocations and Disclinations Point Defects Post-Electrolysis Structure Relaxation Techniques for Structural Investigations References Physical Properties of Electrodeposited Metals and Alloys. Quality Control and Testing Methods Introduction Specific Electrical Resistance Measurements of the Specific Electrical Resistance Thermoelectric Force and Contact Resistance Magnetic Properties Ductility Tensile Strength Methods of Measurements of Strength and Ductility Microhardness Internal Stresses (IS) Methods of IS Measurement Adhesion of the Deposit to a Substrate Methods to Provide Strong Adhesion Methods of Adhesion Measurement Porosity Corrosion Resistance Solderability Control of the deposit thickness The Peculiarities of the Properties of the Electrodeposited Alloys 371 References Index

13 List of Symbols A atomic weight A different constants A the more electropositive metal a thermodynamic activity a first Tafel coefficient a attraction constant in Frumkin equation B the more electronegative metal B adsorption constant b second Tafel coefficient С electric capacitance (per unit area) C, с concentration CE current (cathodic) efficiency D grain size D diffusion coefficient d density d distance E Young s modulus E potential E 0 standard potential E eq equilibrium potential e electron e electronic charge F Faraday constant f F/RT f frequency f different functions G Gibbs energy g gravity factor g number of atoms in the cluster h height, thickness H hardness H root-mean-square roughness xv

14 xvi List of Symbols I electric current i current density i 0 exchange current density i d diffusion current density i lim limiting current density IS internal stress J flux K, k different constants K electrochemical equivalent of the metal K m mass transfer coefficient k r roughness coefficient k B Bolzmann constant L ligand l length, distance M metal M molar mass M z+ ion of metal m mass N number of species N A Avogadro number n net amount of transferred electrons P leveling power of the electrolyte Q net charge passed through the circuit q electric charge q m electric charge at the metal surface R molar gas constant R Ohmic resistance R c contact resistance R radius r distance along the radius ω angular rotation rate RDE rotating disc electrode S area SAS surface active substance T absolute temperature TP throwing power t time U voltage (between cathode and anode) V volume v volume per one species V m molar volume of the metal W Wagner number w velocity (of a flux) x distance y distance

15 List of Symbols xvii z Z α β γ Г Г δ δ N δ пр ε ε η η c η a θ κ l λ D μ μ ν i ν ρ ρ σ σ σ B τ Ф Ф φ ω ω ω electric charge of the species in electron units number of clusters transfer coefficient polarizability η/ i interface energy adsorption limiting adsorption thickness of the reaction layer Nernst diffusion layer Prandtl layer relative permittivity roughness amplitude overpotential cathodic overpotential anodic overpotential coverage conductivity distance of propagation Debye length chemical potential electrochemical potential stoichiometric coefficients viscosity (kinematic) volume charge density resistivity surface tension (specific surface energy) stress breaking stress duration of the process electric potential form factor Galvani potential angular rotation rate (RDE) frequency fraction (mass, molar)