Feinmetall Exhibit 2024
`FormFactor, Inc. v. Feinmetall, GmbH
`IPR2019-00082
`
`Page 1 of 11
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`

`CRC Press
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`
`Library of Congress Cataloging-in-Publication Data
`-——-_—._—__—_—_—__
`Braunovic. Milenko.
`
`Electrical contacts : fundamentals. applications and technology 1' Milenko Brannovic, Nikolai K.
`Myshkin. Valery V. Koncl'u'ts.
`p. cm. _- {Electrical and computer engineering)
`Includes bibliographical references and index.
`ISBN-13: 973—1—ST444-727-9
`ISBN-10: 1-57444-727—0
`
`1. Electric contacts. 2. Friction. 3. Tribology. I. Myshkin, Nikolai Konstantinovich. ll. Konchits. V.
`V. [Valerii Vasil‘evich) III. Title. IV. Series.
`
`TK2821.3665 2006
`621.31'042ndc22 2006015470
`
`
`
`Visit the Taylor & Francis Web site at
`I'll-1P:UWWJaylorandfrancismom
`and the CRC Press Web site at
`httP=HWWW-Crcpress.com
`
`.
`'L
`'
`.
`Auburn flowers-.13.: Lioranes
`_
`._ Fe. . -, “sh-on Library
`Ralph Brez -:
`-
`.i.
`231 Mei
`Auburn Uflietadli". til. 368495606
`
`Page20f11
`
`Page 2 of 11
`
`

`

`
`
`Table of Contents
`
`Part I
`Fundamentals of Electrical Contacts.
`Milenko Brannovic’, Valery V. Konchi'rs, aridNilcoicii K Myshkm
`
`
`
`Chapter 1
`Introduction to Electrical Contacts3
`1. 1
`Introduction”
`...
`1.2 Summary of Basic Features...
`
`Chapter 2
`Contact Mechanics9
`2.1
`Surface of Solids.
`2.2 Surface Topography“:
`2.3 Modern Techniques of Measuring SurfaceParameters“
`2.4 Contact of Smooth Surfaces.
`2.4. 1 Plastic and ElastoplasticContacts.
`2.5 Contact between Rough Surfaces.
`2.5.1 Greenwood—Williamson Model”
`2.52 Multilevel Model"
`.... ....
`2.5.3 Transition from ElastictoPlastic Contact
`
`in
`
`.......11
`........17
`.......21
`23
`....27
`27
`29
`33
`
`Chapter 3
`Tribologyu 35
`3.] Friction:
`3.1.1 Laws of Friction"
`3.1.2 Real Contact Aream
`3.1.3
`Interfacial Bonds (Adhesion Component of Friction)
`3.1.4 Deformation at Friction“
`3.1.5 Friction as a Function of Operating Conditions
`3.1.6 The Preliminary Displacements"
`3.1.7
`Stick-SlipMotion
`3.2Wear
`
`........35
`35
`38
`38
`41
`42
`
`Stages of Wear
`3.2.1
`3.2.2 Simpie Model ofWear
`3.2.3 Basic Mechanisms ofWear
`3.2.4 Abrasive Wear
`3.2.5 AdhesiveWear
`3.2.6 Prow Formation
`
`3.2.7‘r FatigueWear
`3.2.8 CorrosiveWear
`
`46
`47
`48
`43
`50
`52
`56
`57
`57
`59
`59
`62
`
`3.2.9 Fretting Wear
`3.2.10 Delamination...
`3.2.11 Erosion"
`3.2.12 Combined Wear Modes
`3.3 Lubrication...
`3.4 Current Trendsin Tribology
`
`
`
`Page3of11
`
`....65
`....67
`
`Page 3 of 11
`
`

`

`Chapter 4
`... 71
`Contact Materials"
`4.1 Metallic Contact Materials
`4.1.]
`
`Properties of Contact Materials
`4.1.1.1 Copper
`
`4.1.1.3 Silver
`4.1.1.4 Platinum
`
`4.1.1.5 Palladium.
`4.1.1.6 Gold
`
`4.1.2
`4.1.3
`4.1.4
`4.1.5
`416
`
`4.2.3
`
`4.1.1.7 Rhodlum
`4.1.1.8
`"Tungsten...
`4.1.1.9 Nickel...
`Metals and Alloys forHeavy" and MediumDuty Contacts
`Metals and Alloys for Light-Duty Contacts
`Materials for Liquid-Metal Contacts
`Spring Contact Materials.
`Shape--Memory Alloys and’1‘11eir Applicationsin Electrical Contacts
`4.2 Coatings for Electrical Contacts“
`4.2.1
`Basic Requirements"
`4.2.2
`Surface Engineering Technolog1es
`4.2.2.1
`Surface Segregation...
`4.2.2.2
`Ion Implantation
`4.2.2.3 Elecn-oplanng
`4.2.2.4 Electroless Plating
`4.2.2.5 Cladding........................ ..
`4.2.2.6 Chemical Deposition...
`4.2.2.7 Plating by Swabbing...
`4.2.2.8 Physical Vapor Deposition Technology
`4.2.2.9 ElectraSpark Deposition (BSD)...
`4.2.2.10 Intermediate Sublayers
`4. 2. 2. 11 MultilayeredContacts
`Coating Materials.
`...
`....
`4.2.3.1 Coatings forPower Connectors(Copper antiAluminum Joints)...
`42.3.2 Coatings for ElectronicfElectrical Applications...
`4.3 Composite Contact Materials"
`431
`Composite Materials forContacts 111' Commutating Apparatuses
`4.3.2
`Self--Lubricating Composites for Sliding Contacts"
`4.4 Nanostructnred Materials
`4.4.1
`“Bulk” Properties Nanomaterials..
`4.4.2
`Mechanical Properties.Electrical Properties.
`4.4.3
`4.4.4
`
`...
`Magnetic Properties...
`4.4.4.1 Giant Magnetoreslstance (GMR)
`4.4.4.2 Ballistic Magnetoresistance (BL/1R)”-
`Nanotubes"
`Thermal Stability.
`Characterization Techmqites for Nanostructured Materials
`4.4. ‘1. l Nanoindentation...
`4.4.7.2 Scanning Probe Microscopes
`
`4.4.5
`4.4.6
`4.4.7
`
`Page4of11
`
`........71
`71
`71
`75
`76
`78
`78
`79
`79
`79
`80
`80
`83
`85
`8'1
`83
`....89
`89
`91
`92
`94
`94
`97
`97
`99
`99
`.99
`100
`.. 101
`101
`102
`... 102
`104
`...111
`111
`118
`.......125
`127
`127
`131
`136
`136
`138
`140
`.. 142
`143
`.. 143
`144
`
`Page 4 of 11
`
`

`

`149
`
`Chapter 5
`Current and Heat Transfer across the Contact Interface
`......149
`5.1 ContactResistance...
`149
`5.1.1 Circular and Noncircular a»Spots
`.. 154
`5.1.2 Effect of Signal Frequency...
`157
`5.1.3
`Size Efiects, Nanocontacts
`160
`5.1.4 Effect of SurfaceFilms
`166
`5.1.5 Efl’ect of Contact Geometry
`1'12
`5.1. 6 Conductivity of RoughContact
`...180
`Interfacial Heating.
`181
`5.2.1 Principles of Heat Conducnon Theory"
`.. 183
`5.2.2 Simple Problems of Heat Conduction Theory
`188
`5.2.3 Contact Spots Heated by Electrical Current
`188
`5 2 3.1
`Film-Free Metal Contact.
`5.2.3.2 Heating of Contact Spots Having SurfaceFilms”
`.. 190
`5.2.3.3 Field Intensity in the Contact Clearance with
`Tunnel-Conductive Films
`5.2.4 Formulation of Heat Problem with Friction
`
`5.2
`
`5.2.5 Flash Temperature of ElectricalContact
`5.2.6 Thermal Instability of Friction Contact"
`5.2.6.1 Thermoelastic Instability.
`5.2.6.2
`Instability Caused by Temperature-Dependent
`Coefficient of Friction"
`Instability Related to Friction Mode Vananon
`
`5.2.6.2
`
`194
`195
`198
`200
`
`202
`202
`
`Chapter 6
`Reliability Issues1n Electrical Contacts.
`6.1
`Significance of Electrical Contacts Rehablllty
`6.2 Electrical Contact Requirements.
`6.3 Factors Afl‘ectingReliability
`6.4 Connection DegradationMechamsms
`6.4.1 ContactArea
`6.4.2 Oxidation
`6.4. 3 Corrosion...
`
`....205
`
`6. 4.4 Fretting”
`6.4.4. 1 Meclianisms of Frettmg
`6.4.4.2 Factors Affecting Fretting:
`6.4.4.3 Fretting in ElectricalContacts
`6.4.4.4 ContactLoad
`
`205
`....206
`206
`208
`209
`211
`212
`214
`217
`
`
`
`Frequency ofMotion
`6.4.4.5
`6.4.4.6 SlipAmplitude
`6.4.4.7 Relative Humidity
`6.4.4.8 Temperature
`6.4.4.9 Effect of Current
`6.4.4.10 Surface Finish
`6.4.4.11 Hardness
`6.4.4.12 MetalOxide
`6.4.4.13 Coefl'icient ofFriction
`6.4.4.14 Electrochemical Factor
`
`6.4.5
`
`Inter-metallicCompounds
`
`Page5of11
`
`219
`219
`221
`223
`224
`224
`226
`226
`228
`
`229
`230
`230
`230
`230 ’
`
`Page 5 of 11
`
`

`

`
`
`6.4.5.1 Effect of ElectricalCurrent
`
`6.4.6 Electromigratiou..
`...
`6.4.7 Stress Relaxation and Creep...
`6.4.7.1 Nature of the Effect ofElectric:Current"
`6.4.7.2 Effect of Electric Current on Stress Relaxation
`6.4. 8 Thermal Expansion...
`Impact of Connection Degradation...
`6.5 1
`Prognostic Model for Contact Remainlng Life"
`6.5.2 Economical Consequences of Contact Deterioration
`6.5.3 PowerQuality
`
`6.5
`
`232
`237
`240
`241
`242
`247
`....248
`250
`256
`253
`
`Part II
`
`Applications of Electrical Contacts.
`Milenko Brannovic, Valery V. Konchits, aridNikolai K. Myshkiii
`
`....261
`
`Chapter 7
`Power Connections.
`7.1 Types of Power Connectors
`7.2 Design Features and Degradation Mechanisms“
`7.2.1 Bolted Connectors
`7.2.1.1 Frettingin Bolted Connectors
`7.2.12 Frettingin Aluminum Connections:
`7.2.1. 3
`Intennetallics..
`
`....263
`
`........263
`........263
`263
`269
`271
`272
`275
`276
`279
`281
`..."..282
`283
`284
`285
`289
`289
`290
`........292
`7.3 Mitigating Measures"
`7.3. l Contact Area—ConnectorDesign.
`292
`7.3.2 ContactPressure
`294
`296
`297
`300
`301
`301
`302
`302
`.. 303
`304
`....306
`
`7.2.1.4 Creep and Stress Relaxation
`7.2.2 Bus-Stab Contacts...
`7.2.3 Compression Connectors
`7.2.3.1 Degradation Mechamsms'1nCompression Connectors.
`‘7. 2. 3. 2 Corrosion”
`7.2.3.3 Fretting1n Coriipi'ession Connectors...
`7.2.4 Mechanical Connectors
`.
`7.2.4.1
`Binding——Head Screw connectors.
`7.2.4.2
`Insulation Piercing Connectors”
`7.2.4.3 WedgeConnectors
`7. 2.5 Welded Connectors...
`
`.
`
`SurfacePreparation
`7.3.3
`7.3.4 Mechanical Contact Devices
`
`7.3.4.1 Retightening
`7.3.4.2 Bimetallic Inserts
`7.3.4.3 Transition Washers”
`7.3.4.4 Multilam Contact Eleiiierits...
`7.3.4.5
`Shape-Memory Alloy Mechanicai Devices.
`7.3.4.6
`Self—Repairing Joints.
`7.3.5 Lubrication: Contact Aid Compounds”
`Installation Procedures
`..
`.
`.
`
`7.4
`
`Page60f11
`
`Page 6 of 11
`
`

`

`Chapter 8
`Electronic Connections...
`
`309
`
`8.1 Types of Electronic Connections
`8.2 Materials for Electronic Connections
`Solder Materials
`8.2.1
`Lead-FreeSokders
`8.2.2
`8.2.2.1 Tin"
`8.2.2.2 Tin—Silver."
`8.2.2.3
`Tin—Silver—Blsmuth
`
`8.2.2.4 Tin—Silver-Copper....
`8.2.2.5 T1n—S1lver—Copper—Ant1mony
`8.2.2.6 Tm—SilveruAntimony"
`
`8.2.2.8 Tin—Copper
`
`||||
`
`........309
`....309
`310
`312
`312
`312
`313
`313
`314
`314
`314
`315
`315
`316
`316
`316
`317
`317
`319
`322
`322
`323
`324
`32?
`334
`336
`348
`353
`35'?
`361
`361
`361
`362
`
`8.2.2.10 Tinfllnchum—Sllver
`8.2.2.11 Tin—Zinc...
`...
`8.2.2.12 Tin—ch—Sflver
`8.2.2.13 Tin—Ztnc—Sflver—Alununmn—Galhum
`
`8.3 Degradation Mechanisms in Electronic Connectlons
`8.3.1
`Porosity...
`...
`8.3.2
`Corros1onchntanm-1ation
`8.3.2.1
`PoreCorrosmn
`
`8.3.2.2 CreepCorrosion
`
`8.3.3
`8.3.4
`8.3.5
`8.3.6
`8.3.7
`8.3.8
`
`Fretting”
`Frictional Polymerization...
`Inter-metallic Compound5...
`Creep and StressRelaxation
`Electromigration
`Whiskers
`
`8.4 Mitigating Measures
`8.4.1
`Effect of Coating.
`8.4.1.1 Gold Coatings
`8.4. 1.2 Palladium and Palladium Alloys
`8.4.1.3 Tin Coatings.
`8.4.1.4 Nickel and NickelEase A11oy5..
`Effect of Lubrication
`
`8.4.2
`
`364
`364
`
`Chapter 9
`Sliding Contacts..
`9.1 Tribology of Electr1ca1 Contacts
`Interrelation of Friction and ElectricalProcesses
`9.1.1
`91.2
`Role of Boundary Films.
`9 1.3 Main Means of Improving Rehabihty of Sliding Contacts
`9.1.4 Tribophysical Aspects in the Development of Sliding Contacts”;
`9.2 Dry Metal Contacts"
`Low-Current Coniacts.
`9..21
`9.2.1.1 Efiects of Low Ciitrent and Electrical Fieldmon Fnction
`9.2.1.2 Effect of InterfacialShear
`
`........369
`370
`371
`3'11
`
`373
`........376
`3'16
`377
`378
`
`....369
`
`Page7of11
`
`Page 7 of 11
`
`

`

`9.2.2
`
`9.2.3
`
`9.3.4
`
`9.3.5
`
`9.2.1.3 Adhesion, Transfer, Wear Debris Formation. and
`Surface Transformation
`
`High--Current Contacts“
`9.2.2.1 Effects of ElectricalCurrenton Trrbologrcal Behavior
`9.2.2.2
`Influence of Electric Fields.
`
`9.2.2.3 Effect of Velocity.
`9.2.2.4 Effect of Material Combmatron of Contacting Members
`9.2.2.5 Electroplastic Effect1n Sliding Contact.
`9.2.2.6 Friction and Current Transfer'in Metal FiberEmsh Contacts
`Stability of the Contact Resistance. Electrical Noise
`9.2.3.1 Contact Noise in ClosedConnections......................................................
`
`380
`386
`386
`390
`392
`393
`394
`.. 396
`400
`
`402
`.......414
`414
`415
`419
`419
`420
`
`427
`430
`431
`433
`434
`435
`438
`441
`442
`
`9.2.3.2 Electrical Noise in Sliding Contacts .
`Lubricated Metal Contacts.
`Introduction. LubricationFactors.
`9.3.1
`Electrical Properties of Lubricating Boundary Layers
`9.32
`9.3.3
`Conductivity of Lubricated Contacts...
`9.3.3 1 Effect of Lubricant on Conductivity neartheContact Spots
`9.3.3.2 Effect of Lubricant on Conductivity of Contact Spots...
`9.3.3.3 Experimental Studies of Electric Conductivity
`of Lubricated Contacts
`9.3.3.4 Contact Resistance between Very Siiibotli Lubricated Surfaces
`9.3.3.5 Temperature Dependencies of Contact Conductivityuu
`Lubrication Factors in Sliding Contacts
`9.3.4.1 Effect of Lubricant Origin...
`9.3.4.2 Lubricant Durability"
`9.3.4.3 Tribochemical Aspects of Lubrication"
`9.3.4.4 Effect of Velocity'111 Light-Current Contacts
`9.3.4.5 Effects of Lubricant Contact Properties
`..
`9.3.4.6 Current Passage and Friction in High~CurTent
`Lubricated Contacts.
`Lubricants for Electrical Contacts
`9.3.5 1 Lubricants for Sliding Electric Switch Contacts
`9.3.5.2 Lubricants for Sliding Contacts of Sensors
`9.3.5. 3 Selection of Contact Lubricants
`
`449
`450
`451
`454
`............454
`455
`456
`
`Composite Contacts...
`Efiect of Interriiediate Layerson Electrical Characteristics
`9.4.1
`9.4.1.1
`Structure and Electrical Properties of Intermediate Films
`9.4.1.2 Mechanism of CurrentPassage through the Contact with
`Intermediate Films...
`9.4.1.3
`Influence of Polarityon Conductivityin
`Composite—Metal Contact...
`The “Lubricating” Effect of Electrical Current
`9.4.2.1 Effect of Current on Friction Characteristics
`9.4.22 Mechanism of the “Lubricating” Action of the ElectricCurrent............
`9.4. 2. 3 Effect of Brush Material on Friction Behavior with
`ElectricCurrent.
`Electrical Wear...
`9.4.3.1 Wear of Curientless Contacts
`9.4.3.2 Effect of Current on Wear...
`9.4.3.3 Factors Leading to Electrical Wearinthe
`Absence of Sparking...
`
`9.4.2
`
`9.4.3
`
`460
`
`46'?
`471
`471
`473
`
`477
`479
`479
`.. 480
`
`483
`
`9.3
`
`9.4
`
`Page80f11
`
`Page 8 of 11
`
`

`

`9.4.3.4
`
`Influence of the Electric Field in the Clearance
`
`9.4.3.5 Wear with Sparking and Arcing
`9.4.3.6 Some Ways to Reduce Electrical Wear
`
`489
`491
`493
`
`Part III
`
`Diagnostic and Monitoring Technologies”
`Milenko Brannovz'c', Vaiery V. Konchits, and NikolaiK. Myshkm
`
`....495
`
`........49'r'
`.......503
`503
`508
`509
`....511
`511
`
`515
`
`517
`519
`521
`
`Chapter 10
`Electrical Methods in Tribology.. 497
`10.1
`Surface Characterization.
`10.2 Diagnosis of Contact Area andFrictionRegunes
`10.2.1
`Formation of Contact Area...
`10.2.2 Control of Sliding Contact withthePresenceofoxideFilms
`10.2.3 Experimental Study of Metallic Contact Spots Formation.
`10.3 Evaluation of Tribological Performance of Materials and Lubricants:
`10.3.1 Evaluation of Load-Bearing Capacity and Lubricity of Surface Films
`10.3.2 Estimation of Lubricant interlayer Shear Strength under Imperfect
`Lubrication.
`10.3.3 Evaluation of Therriiai Stabdrty of Materials and Lubricants
`by Electrical Methods...
`10.3.4 Control of Surface CoatingsandFilms"
`10.3.5 Novel Systems for Measuring and AnalysisofContact Characterrstrcs............ 523
`
`10.3.5.1 Method of ‘Triboscopy”...
`
`Chapter 11
`Monitoring Technologies... 529
`.......530
`11.] Thermal Measurement5..
`532
`. ...
`11.1.1
`Infrared Thermographyw
`532
`11.1.2 Basic Features of Infrared Thermography
`534
`11.1.3 Types of Infrared Thermal Systems...
`538
`11.1.4 SME Temperature Indicators
`540
`11.1.5 Temperature Stickers (Labels)
`541
`11 1. 6 Remote TemperatureSensors
`....542
`11.2 Resistance Measurements.
`....545
`11.3 Monitoring Contact Load (PressureJ...
`546
`11.4 Ultrasonic Measurements
`....548
`....552
`
`
`11.5 Wireless Monitoring
`11.6 Cost Benefits of Monitorrn‘gnandDiagnostic Technlques
`
`Appendix 1: Methods of Description of Rough Surface
`
`Appendix 2: Shape-Memory Materials
`
`Appendix 3: Electrical Contact Tables
`
`References
`
`555
`
`565
`
`585
`
`599
`
`Index
`
`.641
`
`Page90f11
`
`Page 9 of 11
`
`

`

`208
`
`Electrical Contacts: Fundamentals, Applicatiorrs and Technology
`
`Design—technological factors
`
`
`
`
`
`Contact materials
`Contact coatings
`
`
`(thickness, rneci'lantcallIr
`{mechanicaifetectricai
`
`
`electrical properties)
`
`
`properties.)
`surfaces
`
`Effects of
`contact spot
`interactions
`
`Size of single
`contact spots
`
`Number at
`contact spots
`
`
`
`
`
`despite extensive investigations in the past of the effect of different parameters on the contact
`
`
`Conductingcontactarea
`
`
`II_ealcontactarea
`
`
`
`
`
`
`
`Reliability of electrical contacts
`
`
`
`FIGURE 6.2 Effect of design—technological factors on the performance of electrical contacts.
`
`The diagrams shown in Figure 6.1 and Figure 6.2 are not free of simplifications and approxi-
`mations typical for such formalizations. One should always hear in mind that in addition to the
`above-mentioned factors uncontrollable (random) conditions may act in contact operation such as
`impact, vibration, and acceleration. Second, each type of electrical contact is characterized by a
`specific set of factors governing the contact reliability. It is not always easy to determine the most
`important factors.
`In the following sections, a general description of degradation mechanisms in electrical
`contacts and their impact on the reliability of electrical contacts will be given. A detailed and
`exhaustive account of these degradation mechanisms and characteristic examples is provided in
`Chapters 7 and 8.
`
`6.4 CONNECTION DEGRADATION MECHANISMS
`
`The primary purpose of an electrical connection is to allow the uninterrupted passage of electrical
`current across the contact interface. This can only be achieved if a good metal—to~metal contact is
`established. The processes occurring in the contact zone are complex and not fully explained within
`the limits of present knowledge.
`Although the nature of these processes may differ, they are all governed by the same funda-
`mental phenomena, the degradation of the contacting interface and the associated changes in
`contact resistance, load, temperature, and other parameters of a multipoint contact. However,
`
`.
`
`-.'
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`Page 10 of 11
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`

`

`Sliding Contacts
`
`123 456
`
`3'
`
`107
`
`106
`
`105
`
` 103
`
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`61‘ 104
`§
`3
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`E
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`8
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`10°
`10‘1
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`10-2
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`0.1
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`1
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`10
`
`100
`
`Contact load (cN)
`
`429
`
`1.70
`
`1.55
`
`1.40
`
`1.25
`
`1.10
`
`0.95
`
`0.30
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`0.55
`0.50
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`
`FIGURE 9.64 Substitution schematic diagram and typical dependences of R: (N) at normal loading when gold
`probe was loaded over platinum: (1) unlubricated; (2) lubricated by Vaseline oil; (3] oleic acid; (4) Vaseline oil
`+195 oleic acid; (5) polyglycol diproxamine D157; (6) Epilamen (fluororganic film}; lubricants thickened by
`(7) lithium stearate, (8) lithium oxystearate, and (9) lithium 12 hydroxystearate. R, and Rum-n are calculated
`constriction resistance and tunnel resistance, respectively, for lubricant layer of 0.5-nm thickness.
`
`exceed NC, by an order of magnitude or even more. Monolayers appear to survive under average
`contact pressures of about 0.5 GPa, which is comparable with the microhardnesses of
`several metals.
`The data obtained experimentally, together with the analytical results presented above, lead to
`sorne general conclusions on the current flow through the point contacts under conditions of
`boundary lubrication:
`
`1. In terms of conductivity of a lubricated contact, boundary lubricating films may be
`conditionally divided into two types:
`a. “Thic ” (over 1 nm) monomolecular and multimolecular films ensuring excellent
`antifriction characteristics of the contact and excluding its high electric conductivity;
`b. “Thin" (less than 1 nm) continuous (or containing few breaks) films characterized
`by high contact conductivity. In practice, pairs with the point contact geometry in a
`fixed position as well as in sliding can create conditions when two types of boundary
`lubricating films are possible. In order to form a thin film, a critical pressure pct should
`be reached which is characteristic of the given lubricant and the substrate metal and
`leads to boundary layer structure decomposition. This is in agreement with data on
`noble metals with adsorbed lubricant monolayers that show a transition from low to
`high contact conductivity upon exceeding a critical load.23
`
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`Page 11 of 11
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