ELECTRICAL CONTACTS FUNDAMENTALS, APPLICATIONS AND TECHNOLOGY. MlLENKO BRAUNOVIC MB Interface, Scientific Consultants Montreal, Quebec, Canada

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1 ELECTRICAL CONTACTS FUNDAMENTALS, APPLICATIONS AND TECHNOLOGY MlLENKO BRAUNOVIC MB Interface, Scientific Consultants Montreal, Quebec, Canada VALERY V. KONCHITS National Academy of Sciences of Belarus Belarus, Russia NIKOLAI K. MYSHKIN National Academy of Sciences of Belarus Belarus, Russia (g) CRC Press Taylor &. Francis Group Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business

2 Table of Contents Parti Fundamentals of Electrical Contacts 1 Milenko Braunovic, Valery V. Konchits, and Nikolai K. Myshkin Chapter 1 Introduction to Electrical Contacts Introduction Summary of Basic Features 6 Chapter 2 Contact Mechanics Surface of Solids Surface Topography Modern Techniques of Measuring Surface Parameters Contact of Smooth Surfaces Plastic and Elastoplastic Contacts Contact between Rough Surfaces Greenwood-Williamson Model Multilevel Model Transition from Elastic to Plastic Contact 33 Chapter 3 Tribology Friction Laws of Friction Real Contact Area Interfacial Bonds (Adhesion Component of Friction) Deformation at Friction Friction as a Function of Operating Conditions The Preliminary Displacement Stick-Slip Motion Wear Stages of Wear Simple Model of Wear Basic Mechanisms of Wear Abrasive Wear Adhesive Wear Prow Formation Fatigue Wear Corrosive Wear Fretting Wear Delamination Erosion Combined Wear Modes Lubrication Current Trends in Tribology 67

3 Chapter 4 Contact Materials Metallic Contact Materials Properties of Contact Materials Copper Aluminum Silver Platinum Palladium Gold Rhodium Tungsten Nickel Metals and Alloys for Heavy- and Medium-Duty Contacts Metals and Alloys for Light-Duty Contacts Materials for Liquid-Metal Contacts Spring Contact Materials Shape-Memory Alloys and Their Applications in Electrical Contacts Coatings for Electrical Contacts Basic Requirements Surface Engineering Technologies Surface Segregation Ion Implantation Electroplating Electroless Plating Cladding Chemical Deposition Plating by Swabbing Physical Vapor Deposition Technology Electro-Spark Deposition (ESD) Intermediate Sublayers Multilayered Contacts Coating Materials Coatings for Power Connectors (Copper and Aluminum Joints) Coatings for Electronic/Electrical Applications Composite Contact Materials Composite Materials for Contacts of Commutating Apparatuses Self-Lubricating Composites for Sliding Contacts Nanostructured Materials "Bulk" Properties Nanomaterials Mechanical Properties Electrical Properties Magnetic Properties Giant Magnetoresistance (GMR) Ballistic Magnetoresistance (BMR) Nanotubes Thermal Stability Characterization Techniques for Nanostructured Materials Nanoindentation Scanning Probe Microscopes 144

4 Chapter 5 Current and Heat Transfer across the Contact Interface Contact Resistance Circular and Noncircular a-spots Effect of Signal Frequency Size Effects, Nanocontacts Effect of Surface Films Effect of Contact Geometry Conductivity of Rough Contact Interfacial Heating Principles of Heat Conduction Theory Simple Problems of Heat Conduction Theory Contact Spots Heated by Electrical Current Film-Free Metal Contact Heating of Contact Spots Having Surface Films Field Intensity in the Contact Clearance with Tunnel-Conductive Films Formulation of Heat Problem with Friction Flash Temperature of Electrical Contact Thermal Instability of Friction Contact Thermoelastic Instability Instability Caused by Temperature-Dependent Coefficient of Friction Instability Related to Friction Mode Variation 202 Chapter 6 Reliability Issues in Electrical Contacts Significance of Electrical Contacts Reliability Electrical Contact Requirements Factors Affecting Reliability Connection Degradation Mechanisms Contact Area Oxidation Corrosion Fretting Mechanisms of Fretting Factors Affecting Fretting Fretting in Electrical Contacts Contact Load Frequency of Motion Slip Amplitude Relative Humidity Temperature Effect of Current Surface Finish Hardness Metal Oxide Coefficient of Friction Electrochemical Factor Intermetallic Compounds 230

5 Effect of Electrical Current Electromigration Stress Relaxation and Creep Nature of the Effect of Electric Current Effect of Electric Current on Stress Relaxation Thermal Expansion Impact of Connection Degradation Prognostic Model for Contact Remaining Life Economical Consequences of Contact Deterioration Power Quality 258 Part II Applications of Electrical Contacts 261 Milenko Braunovic, Valery V. Konchits, and Nikolai K. Myshkin Chapter 7 Power Connections Types of Power Connectors Design Features and Degradation Mechanisms Bolted Connectors Fretting in Bolted Connectors Fretting in Aluminum Connections Intermetallics Creep and Stress Relaxation Bus-Stab Contacts Compression Connectors Degradation Mechanisms in Compression Connectors Corrosion Fretting in Compression Connectors Mechanical Connectors Binding-Head Screw Connectors Insulation Piercing Connectors Wedge Connectors Welded Connectors Mitigating Measures Contact Area-Connector Design Contact Pressure Surface Preparation Mechanical Contact Devices Retightening Bimetallic Inserts Transition Washers Multilam Contact Elements Shape-Memory Alloy Mechanical Devices Self-Repairing Joints Lubrication: Contact Aid Compounds Installation Procedures 306

6 Chapter 8 Electronic Connections Types of Electronic Connections Materials for Electronic Connections Solder Materials Lead-Free Solders Tin Tin-Silver Tin-Silver-Bismuth Tin-Silver-Copper Tin-Silver-Copper-Antimony Tin-Silver-Antimony Tin-Bismuth, Tin-Copper Tin-Indium Tin-Indium-Silver Tin-Zinc Tin-Zinc-Silver Tin-Zinc-Silver-Aluminum-Gallium Degradation Mechanisms in Electronic Connections Porosity Corrosion/Contamination Pore Corrosion Creep Corrosion Tarnishing Fretting Frictional Polymerization Intermetallic Compounds Creep and Stress Relaxation Electromigration Whiskers Mitigating Measures Effect of Coating Gold Coatings Palladium and Palladium Alloys Tin Coatings Nickel and Nickel-Base Alloys Effect of Lubrication 364 Chapter 9 Sliding Contacts Tribology of Electrical Contacts Interrelation of Friction and Electrical Processes Role of Boundary Films Main Means of Improving Reliability of Sliding Contacts Tribophysical Aspects in the Development of Sliding Contacts Dry Metal Contacts Low-Current Contacts Effects of Low Current and Electrical Field on Friction Effect of Interfacial Shear 378

7 Adhesion, Transfer, Wear Debris Formation, and Surface Transformation High-Current Contacts Effects of Electrical Current on Tribological Behavior Influence of Electric Fields Effect of Velocity Effect of Material Combination of Contacting Members Electroplastic Effect in Sliding Contact Friction and Current Transfer in Metal Fiber Brush Contacts Stability of the Contact Resistance. Electrical Noise Contact Noise in Closed Connections Electrical Noise in Sliding Contacts Lubncated Metal Contacts Introduction. Lubrication Factors Electrical Properties of Lubricating Boundary Layers Conductivity of Lubricated Contacts Effect of Lubricant on Conductivity near the Contact Spots Effect of Lubricant on Conductivity of Contact Spots Experimental Studies of Electric Conductivity of Lubricated Contacts Contact Resistance between Very Smooth Lubricated Surfaces Temperature Dependencies of Contact Conductivity Lubrication Factors in Sliding Contacts Effect of Lubricant Origin Lubricant Durability Tribochemical Aspects of Lubrication Effect of Velocity in Light-Current Contacts Effects of Lubricant Contact Properties Current Passage and Friction in High-Current Lubricated Contacts Lubricants for Electrical Contacts Lubricants for Sliding Electric Switch Contacts Lubricants for Sliding Contacts of Sensors Selection of Contact Lubricants Composite Contacts Effect of Intermediate Layers on Electrical Characteristics Structure and Electrical Properties of Intermediate Films Mechanism of Current Passage through the Contact with Intermediate Films Influence of Polarity on Conductivity in Composite-Metal Contact The "Lubricating" Effect of Electrical Current Effect of Current on Friction Characteristics Mechanism of the "Lubricating" Action of the Electric Current Effect of Brush Material on Friction Behavior with Electric Current Electrical Wear Wear of Currentless Contacts Effect of Current on Wear Factors Leading to Electrical Wear in the Absence of Sparking 483

8 Influence of the Electric Field in the Clearance Wear with Sparking and Arcing Some Ways to Reduce Electrical Wear 493 Part III Diagnostic and Monitoring Technologies 495 Milenko Braunovic, Valery V. Konchits, and Nikolai K. Myshkin Chapter 10 Electrical Methods in Tribology Surface Characterization Diagnosis of Contact Area and Friction Regimes Formation of Contact Area Control of Sliding Contact with the Presence of Oxide Films Experimental Study of Metallic Contact Spots Formation Evaluation of Tribological Performance of Materials and Lubricants Evaluation of Load-Bearing Capacity and Lubricity of Surface Films Estimation of Lubricant Interlayer Shear Strength under Imperfect Lubrication Evaluation of Thermal Stability of Materials and Lubricants by Electrical Methods Control of Surface Coatings and Films Novel Systems for Measuring and Analysis of Contact Characteristics Method of "Triboscopy" 523 Chapter 11 Monitoring Technologies Thermal Measurements Infrared Thermography Basic Features of Infrared Thermography Types of Infrared Thermal Systems SME Temperature Indicators Temperature Stickers (Labels) Remote Temperature Sensors Resistance Measurements Monitoring Contact Load (Pressure) Ultrasonic Measurements Wireless Monitoring Cost Benefits of Monitoring and Diagnostic Techniques 552 Appendix 1: Methods of Description of Rough Surface 555 Appendix 2: Shape-Memory Materials 565 Appendix 3: Electrical Contact Tables 585 References 599 Index 641