Electrical Connectors E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Wiley - IEEE
- Sprache: Englisch
Discover the foundations and nuances of electrical connectors in this comprehensive and insightful resource
Electrical Connectors: Design, Manufacture, Test, and Selection delivers a comprehensive discussion of electrical connectors, from the components and materials that comprise them to their classifications and underwater, power, and high-speed signal applications. Accomplished engineer and author Michael G. Pecht offers readers a thorough explanation of the key performance and reliability concerns and trade-offs involved in electrical connector selection.
Readers, both at introductory and advanced levels, will discover the latest industry standards for performance, reliability, and safety assurance. The book discusses everything a student or practicing engineer might require to design, manufacture, or select a connector for any targeted application. The science of contact physics, contact finishes, housing materials, and the full connector assembly process are all discussed at length, as are test methods, performance, and guidelines for various applications.
Electrical Connectors covers a wide variety of other relevant and current topics, like:
- A comprehensive description of all electrical connectors, including their materials, components, applications, and classifications
- A discussion of the design and manufacture of all parts of a connector
- Application-specific criteria for contact resistance, signal quality, and temperature rise
- An examination of key suppliers, materials used, and the different types of data provided
- A presentation of guidelines for end-users involved in connector selection and design
Perfect for connector manufacturers who select, design, and assemble connectors for their products or the end users who concern themselves with operational reliability of the system in which they’re installed, Electrical Connectors also belongs on the bookshelves of students learning the basics of electrical contacts and those who seek a general reference with best-practice advice on how to choose and test connectors for targeted applications.
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Veröffentlichungsjahr: 2020
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Table of Contents
Cover
Title Page
Copyright
About the Editors
List of Contributors
Preface
1 What Is an Electrical Connector?
1.1 Challenges of Separable Connectors
1.2 Components of a Connector
1.3 Connector Types
1.4 Connector Terminology
References
2 Connector Housing
2.1 Mechanical Properties
2.2 Electrical Properties
2.3 Flammability
2.4 Temperature Rating
2.5 Housing Materials
References
3 Contact Spring
3.1 Copper Alloys
3.2 Nickel Alloys
3.3 Conductive Elastomers
3.4 Contact Manufacturing
References
4 Contact Plating
4.1 Noble Metal Plating
4.2 Non‐noble Metal Plating
4.3 Underplating
4.4 Plating Process
References
5 Insertion and Extraction Forces
5.1 Insertion and Extraction Forces
5.2 Contact Retention
5.3 Contact Force and Deflection
5.4 Contact Wipe
References
6 Contact Interface
6.1 Constriction Resistance
6.2 Contact Resistance
6.3 Other Factors Affecting Contact Resistance
6.4 Current Rating
6.5 Capacitance and Inductance
6.6 Bandpass and Bandwidth
References
7 The Back‐End Connection
7.1 Soldered Connection
7.2 Press‐Fit Connection
7.3 Crimping Connection
7.4 Insulation Displacement Connection
References
8 Loads and Failure Mechanisms
8.1 Environmental Loads
8.2 Failure Mechanisms in Electrical Connectors
8.3 Case Study by NASA: Electrical Connectors for Spacecraft
References
9 Fretting in Connectors
9.1 Mechanisms of Fretting Failure
9.2 Reducing the Damage of Fretting
References
10 Testing
10.1 Dielectric Withstanding Voltage Testing
10.2 Insulation Resistance Testing
10.3 Contact Resistance Testing
10.4 Current Rating Testing
10.5 Electromagnetic Interference and Electromagnetic Compatibility Testing
10.6 Temperature Life Testing
10.7 Temperature Cycling with Humidity Testing
10.8 Thermal Cycling Testing
10.9 Thermal Shock Testing
10.10 Humidity Testing
10.11 Corrosion
10.12 Mixed Flowing Gas Testing
10.13 Vibration
10.14 Highly Accelerated Life Testing
10.15 Environmental Stress Screening
References
Notes
11 Supplier Selection
11.1 Connector Reliability
11.2 Capability Maturity Models
11.3 Key Reliability Practices
11.4 Reliability Capability of an Organization
11.5 The Evaluation Process
References
12 Selecting the Right Connector
12.1 Connector Requirements Based on Design and Targeted Application
12.2 Mating Cycles
12.3 Current and Power Ratings
12.4 Environmental Conditions
12.5 Termination Types
12.6 Materials
12.7 Contact Finishes
12.8 Reliability
12.9 Raw Cables and Assemblies
12.10 Supplier Reliability Capability Maturity
12.11 Connector Selection Team
12.12 Selection of Candidate Parts from a Preferred Parts Database
12.13 Electronic Product Manufacturers' Parts Databases
12.14 Parts Procurement
12.15 Parts Availability
12.16 High‐Speed Connector Selection
12.17 NASA Connector Selection
12.18 Harsh Environment Connector Selection
12.19 Fiber‐Optic Interconnect Requirements by Market
12.20 High‐Power Subsea Connector Selection
12.21 Screening Tests
12.22 Low‐Voltage Automotive Single‐ and Multiple‐Pole Connector Validation
12.23 Failure Modes, Mechanisms, and Effects Analysis for Connectors
12.24 Connector Experiments
12.25 Summary
References
13 Signal Connector Selection
13.1 Issues Involving High‐Speed Connectors
13.2 Signal Transmission Quality Considerations
13.3 Electromagnetic Compatibility
13.4 Virtual Prototyping
13.5 Vector Network Analyzer
13.6 Simulation Program with Integrated Circuit Emphasis (SPICE)
References
14 Advanced Technology Attachment Connectors
14.1 ATA Connector and SATA Connector Overview
14.2 History of ATA and SATA
14.3 Physical Description of ATA Connectors, ATA Alternative Connectors, and SATA Connectors
14.4 ATA Standardization and Revisions
14.5 SATA Standardization and Revisions
14.6 SATA in the Future
References
15 Power Connectors
15.1 Requirements for Power Connectors
15.2 Power Connector Materials
15.3 Types of Power Connectors
15.4 Power Contact Resistance
15.5 Continuous, Transient, and Overload Current Capacities
15.6 Current Rating Method
References
16 Electrical Connectors for Underwater Applications
16.1 Background and Terminology
16.2 Commercial Off‐the‐Shelf (COTS) Connectors
16.3 Connector Design
16.4 Connector Deployment and Operation
16.5 Discussion and Conclusion
References
Note
17 Examples of Connectors
17.1 Amphenol ICC M‐Series™ 56 Connectors
17.2 Amphenol ICC Paladin® Connectors
17.3 Amphenol ICC 3000W EnergyEdge™ X‐treme Card Edge Series
17.4 Amphenol ICC FLTStack Connectors
17.5 Amphenol ICC HSBridge Connector System
17.6 Amphenol ICC MUSBR Series USB 3.0 Type‐A Connectors
17.7 Amphenol ICC Waterproof USB Type‐C™ Connectors
17.8 Amphenol ICC NETBridge™ Connectors
17.9 Amphenol Sine Systems DuraMate™ AHDP Circular Connectors
17.10 Amphenol Aerospace MIL‐DTL‐38999 Series III Connectors
17.11 Fischer Connectors UltiMate™ Series Connectors
17.12 Hirose Electric DF50 Series Connectors
17.13 Hirose Electric microSD™ Card Connectors
17.14 Molex SAS‐3 and U.2 (SFF‐8639) Backplane Connectors
17.15 Molex NeoPress™ Mezzanine Connectors
17.16 Molex Impel™ Plus Backplane Connectors
17.17 Molex EXTreme Guardian™ Power Connectors
17.18 Molex Imperium™ High Voltage/High Current Connectors
17.19 TE Connectivity Free Height Connectors
17.20 TE Connectivity STRADA Whisper Connectors
17.21 TE Connectivity MULTI‐BEAM High‐Density (HD) Connectors
17.22 TE Connectivity HDMI™ Connectors
17.23 TE Connectivity AMP CT Connector Series
17.24 TE Connectivity Micro Motor Connectors
17.25 TE Connectivity AMPSEAL Connectors
17.26 TE Connectivity M12 X‐Code Connectors
17.27 TE Connectivity SOLARLOK 2.0 Connectors
17.28 TE Connectivity Busbar Connectors
References
Appendix A: Standards
A.1 Standard References for Quality Management and Assurance
A.2 General Specifications for Connectors
A.3 Safety‐Related Standards and Specifications
A.4 Standard References for Connector Manufacturing
A.5 Standard References for Socket Material Property Characterization
A.6 Standard References for Socket Performance Qualification
A.7 Standard References for Socket Reliability Qualification
A.8 Other Standards and Specifications
A.9 Telcordia
A.10 Society of Cable Telecommunications Engineers (SCTE)
A.11 Electronic Industries Alliance/Telecommunications Industry Association (EIA/TIA)
A.12 International Electrotechnical Commission (IEC)
A.13 Military Standards (MIL‐STD)
A.14 Standards for Space‐Grade Connectors
References
Index
End User License Agreement
List of Tables
Chapter 2
Table 2.1 Categorized temperature range of electronic parts.
Table 2.2 Crystalline and amorphous polymers [8].
Table 2.3 General comparisons of crystalline, amorphous, and liquid‐crystalli...
Table 2.4 Polyester characteristics: PET, PBT, and PCT [9].
Table 2.5 Comparisons of thermoplastic polymers [7, 8].
Chapter 3
Table 3.1 Stress remaining for alloys at room temperature after 10 years of u...
Table 3.2 Solderability rating of copper alloys [1].
Table 3.3 Copper alloys in which stress corrosion cracking was observed [6].
Table 3.4 Physical and mechanical properties of silicone rubbers [9].
Table 3.5 Temper name and standard tensile strength requirements [3].
Chapter 4
Table 4.1 Porosity counting via corrosion product size.
Table 4.2 Comparisons between different contact platings.
Chapter 7
Table 7.1 Common lead‐free solders [12].
Chapter 8
Table 8.1 Propensity to form tin whisker by various deposition methods [25].
Table 8.2 Whisker growth length of various types of solder dip [30].
Table 8.3 Values of ionization potential.
Chapter 9
Table 9.1 Fretting sources [1].
Table 9.2 Classification of contact resistance behaviors [14].
Chapter 10
Table 10.1 Qualification testing sequence for slot connectors required by Int...
Table 10.2 Breakdown and melting voltage of surface insulation films.
Table 10.3 Predominant degradation mechanism and pollutants in the environmen...
Table 10.4 MFG test methods developed by Battelle Labs [15].
Table 10.5 MFG test methods developed by EIA.
Table 10.6 MFG test methods developed by IEC.
Table 10.7 MFG test methods developed by Telcordia.
Table 10.8 G1 (T) MFG test method developed by IBM.
Table 10.9 CALCE MFG chamber capability.
Chapter 12
Table 12.1 Dielectric withstanding voltage (DWV) and suggested rated operatin...
Table 12.2 Connector housing material properties [24].
Table 12.3 Contact spring material characteristics [24].
Table 12.4 Contact finish characteristics [24].
Table 12.5 Harsh environment connector properties for connector selection.
Table 12.6 Typical Amphenol fiber optic interconnect requirements by market [...
Table 12.7 NASA EEE‐INST‐002 screening requirements for circular connectors.
Table 12.8 NASA EEE‐INST‐002 qualification requirements for circular connecto...
Table 12.9 NASA EEE‐INST‐002 qualification requirements for D‐subminiature co...
Table 12.10 NASA workmanship requirements for connectors.
Table 12.11 Connector validation test matrix.
Table 12.12 Sample FMMEA inputs for connectors.
Table 12.13 Specifications of the testing system [52].
Chapter 13
Table 13.1 Characteristics of Cat5e, Cat6, and Cat7 cables.
Chapter 15
Table 15.1 Test chamber temperatures and connector internal temperatures with...
Chapter 16
Table 16.1 Summary of COTS connector types and their characteristics.
Table 16.2 Thermal resistivity of isolating materials for electrical cables.
Table 16.3 Epoxy resins selection for underwater use.
Table 16.4 Advantages of wet‐mate compared to dry‐mate connectors concerning ...
Appendix A
Table A.1 Specifications of ESA for multicontact connectors.
List of Illustrations
Chapter 1
Figure 1.1 Schematic illustration of a typical connector [3].
Figure 1.2 (a) Plug contact spring and (b) receptacle contact spring [6].
Figure 1.3 Examples of connector housings.
Figure 1.4 Contact interface [10].
Figure 1.5 Levels of interconnection in connectors.
Figure 1.6 Parallel arrangement of a mezzanine connector. TX is the transmit...
Figure 1.7 PCB with mezzanine connectors [11].
Figure 1.8 Schematic of a backplane system [15]. Graphically renewed.
Figure 1.9 (a–c) Eye diagrams of 5‐Gbps nonreturn to zero signals of clear i...
Figure 1.10 A backplane system with backplane connectors [17].
Figure 1.11 (a) Schematic of insulation displacement contact [18] and (b) an...
Figure 1.12 Varieties of crimping joints.
Figure 1.13 A PCB system, including various wire‐to‐board connectors [19].
Figure 1.14 Example of male (left) and female connectors (right).
Figure 1.15 Examples of connector polarity.
Figure 1.16 Pins of different widths.
Figure 1.17 Pitch of the pins in an Arduino board [20]. Reprinted with permi...
Figure 1.18 Three methods of mounting the same barrel connector: (left to ri...
Figure 1.19 Arlington LPCG50 low‐profile strain relief cord connector [21]....
Chapter 2
Figure 2.1 Comparison of melting temperatures and heat deflection temperatur...
Figure 2.2 An eight‐cavity mold with an H‐type shape [10].
Chapter 3
Figure 3.1 Rank of conductivity of copper alloy [4].
Figure 3.2 Manufacturing process for metallic alloys [4].
Chapter 4
Figure 4.1 Guidelines for selecting contact plating materials [1].
Figure 4.2 Porosity as a function of plating thickness and substrate roughne...
Figure 4.3 Schematic representation of Au/Ni process and comparable NCS/NCNA...
Chapter 5
Figure 5.1 Schematic illustrations of (a) mating and engagement process and ...
Figure 5.2 Insertion force measurements of connectors during dust/humidity t...
Figure 5.3 Schematic illustration of a zero‐insertion‐force connection [6]. ...
Figure 5.4 Contact resistance versus contact normal force and deflection [2]...
Figure 5.5 The effect of wipe distance on the increase in contact resistance...
Chapter 6
Figure 6.1 Schematic illustration of (a) contact interface and (b) asperitie...
Figure 6.2 Asperity interaction [3].
Figure 6.3 Contact between two spheres.
Figure 6.4 Schematic of four‐wire measurement.
Figure 6.5 Time dependence of contact resistance by increasing the contact c...
Figure 6.6 Temperature distribution in a constriction of a contact [13]. Gra...
Figure 6.7 Contact resistance during fretting of gold‐flashed palladium agai...
Figure 6.8 Schematic illustration for parasitic capacitance of an electrical...
Figure 6.9 A model for calculation of mutual capacitance and mutual inductan...
Chapter 7
Figure 7.1 (a) Connectors embedded on a PCB using the PTH method and (b) a s...
Figure 7.2 (a) Solder‐pasted PCB and (b) connectors embedded on a PCB using ...
Figure 7.3 Typical SMT process.
Figure 7.4 Example of a reflow profile. Graphically renewed [5, 6].
Figure 7.5 Schematic of press‐fit connection [26]. Graphically renewed.
Figure 7.6 (a) Connection using press‐fit [26] and (b) cross‐section image o...
Figure 7.7 Types of press‐fit pins [30].
Figure 7.8 Model of compliant press‐fit pin connection [30].
Figure 7.9 (a) Schematic diagram of the crimping method and (b) cross‐sectio...
Figure 7.10 Crimp terminal configurations: (a) straight barrel, (b) open bar...
Figure 7.11 Residual radial contact force after crimping.
Figure 7.12 Crimp connection characteristics relative to the crimp height [3...
Figure 7.13 A typical IDC process [34].
Chapter 8
Figure 8.1 Schematic illustration of a typical connector [1].
Figure 8.2 Temperature profiles for electrical connectors used at different ...
Figure 8.3 Wear tracks due to micro‐motion [13].
Figure 8.4 Fishbone diagram for failures in electrical connectors.
Figure 8.5 Land grid array socket assembly [15].
Figure 8.6 Electrochemical cell formation and growth of silver dendrites.
Figure 8.7 Electrochemical reactions on the insulating surface [15].
Figure 8.8 (a) Dendrite film and (b) dendrites in region a on a polyimide su...
Figure 8.9 Fishbone diagram for silver electrochemical migration.
Figure 8.10 Connector pins on board side with tin finish [19].
Figure 8.11 Tin whisker growth on a connector pin [19].
Figure 8.12 (a) Board connections of APPS and (b)–(d) tin whiskers on the co...
Figure 8.13 (a) Grain growth mechanism of tin whisker growth and (b) a typic...
Figure 8.14 Schematic illustration of whisker initiation model by contact lo...
Figure 8.15 Fishbone diagram for tin whiskers.
Figure 8.16 Fishbone diagram for corrosion in electrical connectors.
Figure 8.17 Schematic of (a) galvanic corrosion in anode‐to‐cathode joint an...
Figure 8.18 Example of pore corrosion in a gold‐plated contact [41].
Figure 8.19 Mechanism of pore corrosion [42]. Graphically renewed.
Figure 8.20 (a) Mechanism of creep corrosion [46] and (b) example of creep c...
Figure 8.21 SEM image of fretting corrosion at a gold‐plated copper alloy su...
Figure 8.22 Mechanism of fretting corrosion in electrical connectors [51].
Figure 8.23 (a) Resistance change with excitation level under fixed frequenc...
Figure 8.24 Breakdown voltage according to the contact distance between Fe c...
Figure 8.25 Breakdown voltage versus relative humidity [61].
Figure 8.26 A flashover model on polluted electrode, proposed by Obenaus [62...
Figure 8.27 Arc formation in electrical connectors.
Figure 8.28 (a) Crater and (b) pip on a contact of electrodes [64].
Figure 8.29 Creep curve with constant load [68].
Figure 8.30 Schematic diagrams of (a) dislocation creep and (b) diffusional ...
Figure 8.31 Creep deformation mechanisms with various temperature and stress...
Figure 8.32 Fishbone diagram of creep failure in electrical connectors.
Figure 8.33 (a) Creep cavities along grain boundary [73] and (b) schematic o...
Figure 8.34 Typical curves of wear process [77]. Graphically renewed.
Figure 8.35 Failure mechanism of wear in electrical connectors.
Figure 8.36 Schematic illustration of adhesive wear.
Figure 8.37 Adhesive wear debris [81].
Figure 8.38 Schematic illustrations of (a) two‐body abrasion [83] and (b) th...
Figure 8.39 (a) Schematic of fatigue wear and (b) cross‐section of worn stee...
Figure 8.40 Contact resistance of contact pair versus fretting cycles [90]....
Figure 8.41 Vinylite replica of (a) palladium contact with organic deposit a...
Figure 8.42 Contact resistance of palladium surfaces in benzene‐saturated dr...
Figure 8.43 Overall schematic of the ECO system and ET liquid hydrogen cryog...
Figure 8.44 Soldered pins and sockets [99].
Chapter 9
Figure 9.1 Summarized fretting failure process.
Figure 9.2 Actual variation of contact resistance over fretting cycles in go...
Figure 9.3 Schematic representation of the degradation process [9].
Figure 9.4 Illustration of classification of material behavior.
Figure 9.5 Contact resistance behavior of various tested metal combinations ...
Figure 9.6 Effect on contact resistance of palladium‐palladium contacts by f...
Figure 9.7 Effect of grain size on critical number of cycles for copper conn...
Figure 9.8 Effect of contact load on contact resistance [11].
Figure 9.9 Sequence of events in contact zones of contacts with contact load...
Figure 9.10 Effect of frequency on number of cycles required to attain prede...
Figure 9.11 Coefficient of friction versus time for different fretting frequ...
Figure 9.12 Distance from initial position (wear depth) versus time for diff...
Figure 9.13 Effect of fretting slip amplitude on number of cycles required t...
Figure 9.14 Schematic diagram of contact areas with lower (left) and higher ...
Figure 9.15 Effects of (a) 10, (b) 100, (c) 500, and (d) 1000 mA electric cu...
Figure 9.16 Effect of temperature on cycles to attain 20 mΩ by tin‐plated co...
Figure 9.17 Effect of quartz particles on contact resistance [27].
Figure 9.18 Contact surface morphology with quartz particles [27].
Figure 9.19 Comparison of combined effect of humidity and quartz particles w...
Figure 9.20 Effect of quantity of lubricant on contact resistance [33].
Figure 9.21 Effects of different coating materials on contact resistance: (a...
Chapter 10
Figure 10.1 Schematic of (a) contact interface and (b) asperity.
Figure 10.2 Schematic of four‐wire measurements.
Figure 10.3 MFG chamber located at CALCE at the University of Maryland.
Chapter 11
Figure 11.1 Key reliability practices [3].
Chapter 12
Figure 12.1 (a) Construction of the basic current‐carrying curve and (b) der...
Figure 12.2 Thermal properties of electrical insulating materials [21]. Grap...
Figure 12.3 NASA connector selection process [39].
Figure 12.4 Materials selection based on an Ashby plot [43].
Figure 12.5 Failure site‐mode‐cause‐mechanism structure for adverse event in...
Figure 12.6 Failure percentage of A and B Minifit connectors as a function o...
Figure 12.7 Reconstructed interferograms of the PCB connector surface for sa...
Figure 12.8 Test samples with different lengths of epoxy dispensing (Epoxy B...
Figure 12.9 Assembly drawing of plug device [52].
Figure 12.10 Diagram of the relationship between contact resistance and cycl...
Chapter 13
Figure 13.1 Block diagram of a TDR circuit [3]. Graphically renewed.
Figure 13.2 Simplified diagram of a TDR waveform.
Figure 13.3 TDR results for (a) open‐ and (b) short‐circuit terminations; (c...
Figure 13.4 Aberration on TDR pulse [4]. Graphically renewed.
Figure 13.5 MMTL model of high‐speed and high‐density connectors [5].
Chapter 14
Figure 14.1 ATA power interface and data interface.
Figure 14.2 (a) SATA power interface and data interface, and (b) schematic o...
Figure 14.3 An ATA interface with three connectors.
Figure 14.4 A SATA interface with two connectors.
Figure 14.5 AT attachment 40‐pin connector.
Figure 14.6 Pin arrangement of the 44‐pin connector [10].
Figure 14.7 The SFF8057 connector, an alternative for ATA 40‐pin connector [...
Figure 14.8 The SFF8058 connector, an alternative for ATA 40‐pin connector [...
Figure 14.9 SATA connector magnified.
Figure 14.10 A SATA interface with one L‐shaped connector and one flat conne...
Figure 14.11 Connection of two SATA interfaces to a motherboard.
Chapter 15
Figure 15.1 Power connector designs: (a) compression connector, (b) bolted c...
Figure 15.2 SAE J1772 connector for electric vehicles [17].
Figure 15.3 Various types of compression connectors [18].
Figure 15.4 Various types of bolted connectors (a); cross‐section images of ...
Figure 15.5 Wedge connector installation.
Figure 15.6 Insulation‐piercing connector with wires [21].
Figure 15.7 Effect of current cycling on the contact resistance and temperat...
Figure 15.8 Arbitrarily shaped conductor, thermally and electrically insulat...
Figure 15.9
ϕ
–
ϑ
curve of a thermally symmetric contact system [26]...
Figure 15.10 Starting current of an induction motor.
Figure 15.11 A general qualification procedure for current rating of power c...
Chapter 16
Figure 16.1 Sketch of a basic fluid‐filled connector.
Figure 16.2 Rubber‐molded connectors, dry mate on the left, and wet mate on ...
Figure 16.3 12‐pin bulkhead connector with metallic housing [28].
Figure 16.4 Scheme of a pressure‐balanced oil‐filled connector [25].
Figure 16.5 Scheme of a pressure‐balanced oil‐filled connector [27, 28].
Figure 16.6 Non‐contact wet‐mateable connector [2].
Figure 16.7 Cable termination [31] (top) and Y‐splice [24] (bottom).
Figure 16.8 Characteristic curves of the endurance to pressure cycles depend...
Figure 16.9 Nautilus connector, ROV mateable [64].
Figure 16.10 A diver filling the pocket with air to perform the dry connecti...
Figure 16.11 CAD file of the air pockets for underwater cable connections at...
Figure 16.12 Mated connector inside oil‐filled clamshell tool [66].
Chapter 17
Figure 17.1 Amphenol ICC M‐Series™ 56 connectors [1].
Figure 17.2 Amphenol ICC Paladin® 112G connectors [2].
Figure 17.3 Amphenol ICC 3000W EnergyEdge™ X‐treme connector [3].
Figure 17.4 Amphenol ICC FLTStack connectors [4].
Figure 17.5 Amphenol ICC HSBridge connectors [5].
Figure 17.6 Amphenol ICC MUSBR series USB 3.0 connector [6].
Figure 17.7 Amphenol ICC waterproof USB Type‐C™ connectors [7].
Figure 17.8 Amphenol ICC NETBridge™ connector [8].
Figure 17.9 Amphenol Sine Systems DuraMate™ AHDP circular connectors [9].
Figure 17.10 Amphenol Aerospace MIL‐DTL‐38999 Series III connectors [10].
Figure 17.11 Fischer Connectors UltiMate™ series 27‐pin connector [11].
Figure 17.12 Hirose Electric DF50 connectors [12].
Figure 17.13 Hirose Electric MicroSD™ DM3AT connector [13].
Figure 17.14 Molex SAS‐3 backplane receptacle (left) and U.2 connectors (rig...
Figure 17.15 Molex NeoPress™ high‐speed mezzanine connector [15].
Figure 17.16 Molex Impel™ Plus backplane connectors [16].
Figure 17.17 Molex EXTreme Guardian™ power connectors [17].
Figure 17.18 Molex Imperium™ power connectors.
Figure 17.19 TE Connectivity free height connectors [19].
Figure 17.20 TE Connectivity STRADA Whisper connectors [20].
Figure 17.21 TE Connectivity MULTI‐BEAM HD connectors [21].
Figure 17.22 TE Connectivity HDMI connector [22].
Figure 17.23 TE Connectivity AMP CT connector series [23].
Figure 17.24 TE Connectivity Micro Motor connectors [24].
Figure 17.25 TE Connectivity AMPSEAL connectors [25].
Figure 17.26 TE Connectivity M12 X‐code connectors [26].
Figure 17.27 TE Connectivity SOLARLOK 2.0 connectors [27].
Figure 17.28 TE Connectivity busbar connectors [28].
Guide
Cover Page
Table of Contents
Begin Reading
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Electrical Connectors
Design, Manufacture, Test, and Selection
Edited by
San Kyeong and Michael G. Pecht
Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland, College Park, MD, USA
This edition first published 2021Chapter 10 © 2021 JohnWiley & Sons Ltd and United States Government as represented by the Administrator of the National Aeronautics and Space Administration. Published by JohnWiley & Sons Ltd. The contributions to the chapter written by Bhanu Sood were performed as part of his official duties as an employee of the National Aeronautics and Space Administration. No copyright is claimed in the United States under Title 17, U.S. Code. All Other Rights Reserved.
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Library of Congress Cataloging‐in‐Publication Data
Names: Kyeong, San, editor. | Pecht, Michael G., editor.
Title: Electrical connectors : design, manufacture, test, and selection / edited by San Kyeong and Michael G. Pecht, Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, USA.
Description: Hoboken, New Jersey : Wiley IEEE Press, 2021. | Includes index.
Identifiers: LCCN 2020028241 (print) | LCCN 2020028242 (ebook) | ISBN 9781119679769 (cloth) | ISBN 9781119679806 (adobe pdf) | ISBN 9781119679820 (epub)
Subjects: LCSH: Electric connectors.
Classification: LCC TK3521 .E39 2021 (print) | LCC TK3521 (ebook) | DDC 621.319/3--dc23
LC record available at https://lccn.loc.gov/2020028241
LC ebook record available at https://lccn.loc.gov/2020028242
Cover Design: Wiley
Cover Images: (inset) Designed by San Kyeong
About the Editors
San Kyeong ([email protected]) is a staff engineer at the R&D headquarters of Samsung Electro‐Mechanics. He is currently with the Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland. He received a BE degree and PhD in chemical and biological engineering from the Seoul National University of Seoul, South Korea, in 2010 and 2016, respectively. He has expertise in material engineering for passive electronic components. He is the author/co‐author of Chapters 1, 6, 7, 8, 12, 15, and 17.
Michael G. Pecht ([email protected]) has a BS in physics, an MS in electrical engineering, and an MS and PhD in engineering mechanics from the University of Wisconsin at Madison. He is the George E. Dieter chair professor of mechanical engineering and a professor of applied mathematics, statistics, and scientific computation at the University of Maryland. He is the founder of the Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland, which is sponsored by more than 150 of the world's leading electronics companies. He is a professional engineer, an IEEE fellow, an ASME fellow, an SAE fellow, and an IMAPS fellow. He served as editor in chief of Circuit World for two years, as editor in chief of IEEE Access for six years, as editor in chief of IEEE Transactions on Reliability for nine years, and as editor in chief of Microelectronics Reliability for 16 years. He has also served on three US National Academy of Science studies, on two US Congressional investigations into automotive safety, and as an expert to the US FDA. He has written more than 40 books on product reliability, development, and use, and supply chain management. He has also written a series of books on the electronics industry in China, Korea, Japan, and India. He has written more than 900 technical articles and holds 10 patents. He has consulted for more than 50 major international electronics companies, providing expertise in strategic planning, design, test, prognostics, intellectual property, and risk assessment of electronic products and systems.
List of Contributors
Michael H. Azarian
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Ilknur Baylakoglu
SATURN Engineering, TUBITAK, Ankara, Turkey
Deepak Bondre
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Diganta Das
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Jens Engström
Division for Electricity, Uppsala University, Uppsala, Sweden
Chien‐Ming Huang
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Lovlesh Kaushik
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
San Kyeong
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Kyle LoGiudice
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Michael G. Pecht
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Flore Remouit
Division for Electricity, Uppsala University, Uppsala, Sweden
Pablo Ruiz‐Minguela
Division for Energy and Environment, TECNALIA, Derio, Spain
Neda Shafiei
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
Bhanu Sood
NASA Goddard Space Flight Center, Greenbelt, MD, USA
Lei Su
Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, Wuxi, China
Xiaonan Yu
Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, Wuxi, China
Preface
Connectors allow circuits and products that are manufactured independently to be electrically connected, tested, maintained, and upgraded. Manufacturers are thus able to optimize electronic systems and keep up with the rapid pace of electronic product development. Today, the connector market is valued at more than $50 billion, and there is still an increasing trend in the usage and applications of electronic connectors.
This book covers everything one would need to design, manufacture, and select a connector for any targeted application. It covers the science of contact physics and the engineering involved in the choice and manufacture of contact materials, contact finishes, housing materials, and the full connector assembly process. Test methods, performance and reliability concerns, and guidelines are provided, and various application requirements and selection considerations are discussed.
Key features of the book include the following:
Provides a comprehensive description of electrical connectors, from the components and materials that comprise connectors to their applications and classifications
Provides information on the design and manufacture of all the parts of a connector
Thoroughly explains the key performance and reliability concerns and trade‐offs related to electrical connector selection
Details current industry standards for performance, reliability, and safety assurance
Examines application‐specific criteria for contact resistance, signal quality, and temperature rise
Provides information on key suppliers, materials used, and different types of data provided
Presents guidelines for end users who have concerns about connector selection and new connector designs
This book is intended for connector designers and manufacturers, device manufacturers that select connectors for their products, and end users who are concerned with the operation and reliability of the whole product or system. Students who are learning the basics of electrical contacts will also find this book instructive. The book can also be considered as a guidebook, offering best‐practice advice on how to choose and test the correct connectors for a targeted application. A summary of the chapters is presented here.
Chapter 1 describes the advantages and challenges of separable connectors. It covers the components of a connector: contact spring, contact finish, connector housing, and contact interface. The chapter discusses the types of components, and it ends with a short glossary of basic connector terminology.
Chapter 2 discusses the housing that electrically insulates contact members and provides mechanical support for proper electrical connection. This chapter reviews the design and manufacture of the connector housing as well as the mechanical properties. It also presents relevant standards. The second half of the chapter focuses on materials and design trade‐offs, including a comparison of the advantages and limitations of various thermoplastic polymers.
Chapter 3 discusses contact spring materials in terms of their design trade‐offs, including electrical conductivity, mechanical strength, resistance to stress relaxation or creep, solderability, and resistance to corrosion. Because copper alloys are the predominant material for contacts, their properties are discussed, and the Unified Number System for alloys is explained. The second half of the chapter includes a section on design trade‐offs associated with conductive elastomers and concludes with a discussion of how metal alloy contacts are manufactured. The terminology for commonly used treatment is explained.
Chapter 4 provides insight into managing the mechanical and electrical properties of the contact interface by choosing the appropriate plating material and plating thickness. Contact plating can be divided into two categories: noble metal plating and non‐noble metal plating. These categories are covered in detail, with emphasis on gold, silver, tin, and nickel. The discussion on silver looks at tarnish‐accelerating factors such as chlorine gas, water, nitrogen dioxide, and ozone, and covers management of silver corrosion. Finally, the chapter discusses the four methods of contact plating.
Chapter 5 discusses the contact force that is required to maintain a consistent and reliable contact interface along with contact resistance and contact deflection. The equation for calculating the insertion force is given. The standards relating to measurement of the insertion and extraction forces, as well as the retention force, are listed. Zero‐insertion‐force (ZIF) connectors are also described.
Chapter 6 focuses on the actual surface area of a connector that makes true electrical contact, which differs from the total surface area. The chapter explores factors that affect connector mating, such as contact resistance, temperature, electrical current, and fretting. The chapter provides standards for measuring contact force, contact resistance, current rating, capacitance and inductance, and contact electrical performance. It also describes the mechanics of the mating process, with emphasis on the contact wipe motion. Finally, the chapter discusses determination of the maximum current that a conductor can carry.
Chapter 7 considers the interface between the connector and the cable, circuit board, or assembly. While the contact interface is critical for performance and reliability, the back‐end connection also affects connector assembly cost and reliability. Soldering, press‐fit, crimping, and insulation displacement are described along with their processing flow, mechanism, advantages, and limitations.
Chapter 8 explores environmental and operating load conditions and the failure mechanisms that can arise from the load conditions. The performance and reliability of an electrical connector will depend on its ability to transmit power or signals from the source to the electrical circuit via the contact interface under different loading. To predict and enhance the reliability of electrical connectors, the underlying root cause of any failure mechanism must be investigated. Fishbone diagrams illustrate the causes and effects of each of the failure mechanism discussed, which include silver migration, tin whiskers, corrosion, arc formation, creep, and surface wear.
Chapter 9 focuses on fretting, one of the key failure mechanisms in electromechanical apparatuses having touching surfaces that move relative to each other. Fretting can cause serious degradation in electrical components with separable contacts, such as connectors. The chapter covers the studies on materials, including frictional polymer‐forming metals. It also discusses testing methodologies and test conditions that researchers use.
Chapter 10 provides insight into the testing conducted to verify that the connectors will perform properly over time. Testing by the manufacturer usually involves performance testing per the datasheet requirements. However, the customer may have applications that require performance under unique operational and environmental conditions. This chapter discusses electrical tests for connectors, including dielectric withstanding voltage, low‐signal‐level contact resistance, insulation resistance, contact resistance, and standing wave ratio. Environmental tests include humidity, temperature, and contaminating conditions, and mechanical stress environments include vibration, mechanical shock, and durability cycling exposures. Standards are listed for each of the test methods. The chapter also discusses specific mixed flowing gas (MFG) tests.
Chapter 11 emphasizes that reliability must be managed across all the tiers of the supply chain. Each supplier's reliability practices need to be adequate to satisfy the end‐product requirements of the customers. After discussing the guidelines provided by the IEEE Reliability Program Standard 1332 for the development of a reliability program, the chapter discusses key reliability practices in detail. The chapter concludes with a description of the process for evaluating the reliability capability of suppliers.
Chapter 12 covers the key factors/requirements that must be considered when selecting a connector, including physical application, electrical requirements, mechanical requirements, application environment, mating force, number of mating cycles, current and power ratings, termination types, environmental conditions (e.g. temperature, vacuum, chemicals, radiation, and vibration), materials, and reliability. The chapter discusses screening tests, with emphasis on NASA's three levels of screening. It also explores the use of failure modes and effects analysis (FMEA) to identify the possible failure modes and causes of devices. The chapter concludes with a discussion on recent experiments to test connector reliability.
Chapter 13 focuses on issues involving high‐speed signal connectors, such as signal integrity, transmission quality, signal distortion, interconnect delays, and electromagnetic compatibility. The chapter discusses the process of virtual prototyping. It describes a vector network analyzer, which determines the magnitude and phase characteristics of connectors. The chapter introduces filtered connectors. The chapter concludes with a section on SPICE and how it is used in connector circuit modeling.
Chapter 14 focuses on a mass storage device interface that connects hard disk, optical disk, and solid‐state drives to the computer motherboard. These connectors have important applications in data transmission for personal computer hard disk drives and optical drives alike. They are the intermediate link between a computer's motherboard and the disk controller on the hard disk drive, allowing the drive to read and write information at a fast speed.
Chapter 15 focuses on the requirements (design and use) of connectors for power transmission. The types of power connectors are introduced. It discusses a theoretical approach to estimate temperature rise by constriction current at the contact point. The chapter concludes with a description of the points to consider when setting the rated current and the setting procedure.
Chapter 16 provides an overview of the type of connectors that exist for underwater and subsea electrical connections. The first part presents different types of commercial‐off‐the‐shelf electrical connectors, lists their performances and defaults, and details their typical failure modes and known causes. The second part contains the theory on sealing and on connectors' thermal, electrical, and mechanical properties. The last part provides information on connection procedures and other details about connecting subsea cables, with a focus on the connection of offshore renewable energy farms.
Chapter 17 discusses some of the latest products from the key connector manufacturers (Amphenol, Fischer, Hirose, Molex, and TE Connectivity) and focuses on the specifications, types, limitations, advantages, and usage in various targeted applications.
The appendix lists the recognized specification standards for connectors. These documents were developed by professional organizations internationally.
In addition to the main authors, the following researchers from the Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland contributed to this book: Chien‐Ming Huang, Lovlesh Kaushik Dr. Bhanu Sood, Dr. Michael Azarian, Dr. Diganta Das, Ilknur Baylakoglu, Neda Shafiei, and Kyle LoGiudice. Various CALCE interns were involved in gathering information, including Sumeer Khanna, Gopalakrish Kalarikovilagam Subramanian, Amarah Ahmed, and Ayeesha Jaswal, as well as Cheryl Wurzbacher who conducted an English edit of the book. Other co‐authors include Drs. Flore Remouit, Jens Engström, Pablo Ruiz‐Minguela, and Lei Su and his student Xiaonan Yu.
Dr. San Kyeong and Professor Michael G. Pecht
Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland – College Park
1What Is an Electrical Connector?
Michael G. Pechtand San Kyeong
Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA
An electrical connector is an electromechanical component that provides a separable interface between two parts of an electronic system without compromising the performance of the system. Separability enables circuits that are manufactured independently to be electrically connected, tested, maintained, and upgraded. For example, in a computer or smartphone, the main circuit board and the display and its electronics are manufactured at different locations and are electrically connected using connectors. These subsystems (assemblies) can be tested and upgraded independently of each other. Connectors thus remove the problems of permanent connection of parts and eliminate issues associated with rewiring interconnects [1], such as damage to circuit board conduction paths due to repeated soldering and de‐soldering.
Connectors provide much more flexibility to optimize electronic systems than permanent connections. For example, there are a variety of connectors on the market to satisfy the needs for testing, burn‐in, and assembly of different kinds of electronic systems. They help in supply‐chain management, avoid direct connections, provide opportunities for part replacement and repair, and, in some cases, offer cost savings.
1.1 Challenges of Separable Connectors
The evolution of microelectronics toward higher speeds and switching frequency enforces stringent requirements on connectors. The challenges that confront connectors are extra electrical length, the need for a larger assembly area, compatibility with new technologies, and reliability concerns [2]. A connector introduces an extra electrical path that can lead to added propagation delay and electrical noise, such as cross talk. A connector also introduces new concerns for reliability, because degradation of the contact interface can lead to an increase in contact resistance, which can lead to signal degradation, joule heating, and power loss [2]. These losses are due to increases in contact resistance, which is dependent on the material properties of the connectors, environmental conditions, and mode of operation. Furthermore, because a connector occupies more area than a simple solder or adhesive, the use of connectors might be difficult in applications that have constraints on area.
In the case of signal connectors, signal transmission quality (STQ) must be maintained. STQ refers to the transmission of high‐speed signals through connectors and interconnects without loss of signal quality. The losses may be due to cross talk, transmission delay, or characteristic impedance variation on signal propagation and reflections. The transmission and preservation of signal waveforms forms the crux of STQ.
Electromagnetic compatibility (EMC) refers to the ability of the system to prevent the degradation of the digital signals from external electromagnetic energy. The mitigation of EMC generally involves shielding, filtering, and grounding practices to control electromagnetic interference (EMI).
1.2 Components of a Connector
The main components of a connector include the contact springs, contact finish, and connector housing, as shown in Figure 1.1 [3]. The contact interface is defined by the physical–electrical connection of the pieces of the connector that are mated, and this determines how well the connector performs.
1.2.1 Contact Springs
The contact spring provides the path for the transmission of a signal, power, and/or ground between the circuits that the connector connects. It also provides the normal force, the component of the force that is perpendicular to the surface of contact, which helps in the formation and maintenance of the separable interface [4].
The key mechanical requirements of the contact spring are insertion and extraction force, contact force, contact retention, and contact wipe. The electrical requirements of the contact spring are contact resistance, current rating, inductance, capacitance, and bandwidth. Chapters 3 and 6 provide more discussion on these requirements.
There are two types of contact springs: a receptacle, which is generally a spring member, and a plug, which in most cases is rigid and provides a means for deflecting the receptacle spring to generate the contact normal force [5]. A receptacle contact spring ensures low insertion force while mating and helps the connector endure overstress during nonaligned insertions. Figure 1.2 shows examples of plug and receptacle contact springs [6].
Figure 1.1 Schematic illustration of a typical connector [3].
Figure 1.2 (a) Plug contact spring and (b) receptacle contact spring [6].
The material properties that influence the performance of the contact spring are the modulus of elasticity and the yield strength. The modulus of elasticity is the ratio of the stress applied to the object to the resulting strain within the elastic limit. The yield strength is the point of stress at which the body begins to deform plastically. Before the yield strength is reached, the body deforms elastically – that is, it returns to its original shape when the stress is removed. These properties influence the deflection abilities of the spring and the amount of deflection the spring can support while remaining elastic. This also affects the contact force required to make a proper electrical connection.
Stress relaxation resistance is a property of the material that reduces the contact normal force over time [6]; thus, it is a selection criterion that can affect connector performance. It is the decrease in stress that occurs when the structure is kept in the same strained posture for some interval of time, causing the formation of plastic strain [5]. Loss of normal force through plastic deformation is a design exercise to ensure that spring stresses are not excessive. The yield strength is different for commonly used copper alloys; hence, stress relaxation resistance varies across them. Beryllium copper is the most commonly used alloy when stress relaxation resistance is a concern. Phosphor bronzes are also suitable for most applications [7].
1.2.2 Contact Finishes
The contact finish protects the contact spring base metal from corrosion and limits the formation of films on the surface of the contact spring. To be effective, the contact finish has to completely cover the contact spring and must be corrosion‐resistant.
Films that can increase the contact resistance include thin oxides, sulfides, chloride, and complex mixtures of film layers of the metals formed on the contact's surface. The reduction of contact resistance requires the formation of a metallic interface that is free of films. Contact finishes can be made of noble metals (e.g. gold, palladium, and alloys of these metals) or non‐noble metals (e.g. silver, tin). The type of finish determines the types of surface films that can form on the contact interfaces. The noble metals, especially gold, are inert because there is no formation of any oxides on the surface. In the case of non‐noble metal finishes made of tin, however, tin‐oxide may form in the contact spring and may need to be periodically removed.
Owing to the repeated mating and unmating in separable contact interfaces, some of the surface film is removed by frictional forces. Therefore, two layers of contact finishes referred to as “duplex‐plated” are used [7] to protect the underlying metal. These consist of a layer of noble metal coated on top of a layer of nickel. Duplex‐plated connectors are discussed in Chapter 3.
1.2.2.1 Noble Metal Contact Finishes
The noble metals gold and, to a lesser extent, palladium and its alloys are inert in typical connector operating environments without the presence of acidic gases. But in environments where chlorine or sulfur is present, corrosion of noble metal–finished connectors can occur. Shielding by housing can help prevent corrosion. Lubrication is another means of protection.
Pore corrosion and corrosion due to exposed base metal are of particular concern. If the coating with noble metal is not thick enough or if it is not continuous, the underplate and base metal will be exposed to the environment, leading to corrosion. At elevated temperatures, base metal atoms may migrate to the contact surface and react with oxygen and pollutant gases, allowing corrosion products to migrate out of the pores. This phenomenon is called “pore corrosion.” Hence, pore corrosion of the copper layer beneath the noble metal layer can take place when the noble metal layer becomes porous, exposing the copper to a corrosive environment containing acidic gases of sulfides and chlorides.
Because gold is a noble metal and because thin gold platings tend to be porous, gold coatings are susceptible to the creep of base metal corrosion products across the surface of the gold after formation at pore sites and edge boundaries. Corrosion creep can be inhibited by applying an overall nickel coating prior to application of the gold.
1.2.2.2 Non‐noble Metal Contact Finishes
Non‐noble metal contact finishes consist primarily of tin, although silver, nickel, solder, and lead are commonly used. Alloys of tin‐lead and nickel‐tin are also used sometimes. Tin finishes degrade primarily because of fretting corrosion, which can occur in any operating environment [7]. Fretting corrosion of electrical contacts is caused by repeated micromotions between closed contacts, creating oxides or wear debris that can raise contact resistance. Micromotion can result from vibration, shock, or differential thermal expansion of materials in contact. The connector must be designed to minimize fretting susceptibility, which can be done by providing sufficient friction force at the contact interface to prevent motion from occurring [8].
Tribology refers to the study of friction, lubrication, and wear of contact surfaces. Contact finishes are generally thin. It is therefore essential to maintain the integrity of the contact finishes when subjugated to wear and tear to protect the base metals from exposure to a corrosive environment. The resistance to corrosion and tarnishing and the thermal stability of contact resistance should be kept in mind when choosing a contact finish [8]. Chapter 4 presents a more detailed discussion on contact finish materials.
1.2.3 Connector Housing
Connectors must remain dimensionally stable in the presence of extreme chemical and temperature effects. The maintenance of connector center line spacing, straightness, and flatness is necessary for ensuring proper connector assembly and mating behavior [9]. The connector housing achieves this stability by electrically insulating and mechanically shielding the contact spring, maintaining the position of contacts, and providing mechanical protection of the contacts from the operating environment. Figure 1.3 shows examples of connector housing.
Figure 1.3 Examples of connector housings.
The electrical properties that affect the insulating abilities of the housing include surface and volume resistivity and dielectric withstanding voltage. The mechanical characteristics of the connector housing include flexural strength/modulus and creep strength.
Most of the contact housing designs are similar, but the material used in them varies. This material range serves not only to meet the environmental conditions during operation but also to meet the conditions while manufacturing and assembling. Some of the common materials that are used for making connector housing are polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexylenedimethylene terephthalate (PCT), liquid‐crystalline polymer (LCP), FR‐4, and polyimide. Chapter 2 provides more discussion on connector housing.
1.2.4 Contact Interface
A separable interface is established each time the “male” and “female” parts of the connector are brought into contact. There is a need to create and maintain contact interfaces to achieve the desired electrical performance. The metallic interface is created mechanically [6].
When separable connectors are mated, only the high spots on the surfaces, which are called “asperities,” come into contact. Therefore, the entire connector surface does not come into contact. The asperities depend on the geometry of the surfaces in contact. Figure 1.4 depicts a normal contact interface [10]. It can be seen from the figures that only the asperities of both surfaces come into contact. The size and the number of asperities depend on the surface roughness and the applied load. The applied load also determines the magnitude of the contact area.
The structure of the contact interface depends on the roughness of the surface (which influences the number of asperities), the applied force, and the contact interface geometry. The mechanical characteristics of the contact interfaces, particularly the frictional and wear forces, depend on the asperity microstructure of the contact interfaces [7]. The constriction resistance of the contact interfaces also depends on the asperities. A discussion of contact interface is provided in Chapter 6.
Figure 1.4 Contact interface [10].
1.3 Connector Types
Connectors are classified into three types based on their termination ends: board‐to‐board connectors, cable/wire‐to‐cable/wire connectors, and cable/wire‐to‐board connectors. These are discussed in the following sections. Figure 1.5 gives a pictorial example of the levels of interconnection discussed in this section. An electronic system is a hierarchical interconnection network that allows communication among different electronic devices. Several interconnects are required to ensure proper functioning of electronic devices for signal transmission and power distribution.
As shown in Figure 1.5, six levels of interconnection are normally seen in connectors. Level 0 is the connection between a basic circuit element and its lead, such as the link between a semiconductor chip and the lead frame. Level 1 is the connection between a component lead and a printed circuit board (PCB), exemplified by chip carrier sockets, dual inline package (DIP) sockets, and switches. Level 2 is the connection between two or more PCBs. A motherboard–daughterboard connection is typical. Level 3 is the connection between two subassemblies, such as a power supply and an associated subassembly. Level 4 is the connection from a major subassembly to the input/output (I/O) port of the complete system. Level 5 is the connection between physically separated systems typified by the link between a computer and a printer or other piece of peripheral equipment, or components of a local network.
Figure 1.5 Levels of interconnection in connectors.
1.3.1 Board‐to‐Board Connectors
Board‐to‐board connectors are used to connect PCBs without a cable. The board‐to‐board connectors can save space on cables, making them suitable for systems with limited space. The PCBs can be connected using connectors in “parallel” or “perpendicular” configuration. A connector that connects two PCBs in a stacking configuration is called “mezzanine connector,” as shown in Figure 1.6. The dotted arrow in the right side of Figure 1.6 shows the electrical channel from the transmitter through the connector to the receiver. However, the term is sometimes used to describe “perpendicular” or side‐by‐side PCB arrangements. These arrangements are usually seen for motherboard–daughterboard arrangements, where the focus is on the parallel arrangement. Figure 1.7 shows an example of a circuit board that includes five 1.0‐mm‐pitch 64‐pin mezzanine connectors [11]. This mezzanine connector is described in the IEEE 1386 standard [12].
The specifications that need to be considered when choosing a mezzanine connector include separability; mechanical requirements such as stack height and tolerances; constraints such as standoffs, brackets, or chassis slots and frames; and types of mountings. Separability is dependent on many factors, such as whether the connector is separable or permanent, the number of mating cycles required over its lifetime, and the maximum and minimum value of insertion force required. The operating temperature and humidity also should be considered. EIA 700AAAB is a standard for mezzanine connectors [13].
A backplane is a group of electrical connectors in parallel with each other so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a connector bus. A backplane system is widely used in computer and telecommunication systems because of its flexibility and reliability [14]. As shown in Figure 1.8, the backplane system is used for connecting multiple plug‐in cards along a single backbone to make a complete backplane system [15]. The signal generated by the transmitter passes through two connectors and reaches the receiver. A backplane system with high signal integrity is required in devices used in high‐speed applications. In a gigabit backplane channel design, the backplane and the associated pin field are essential parameters.
Figure 1.6 Parallel arrangement of a mezzanine connector. TX is the transmitter, and RX is the receiver.
Figure 1.7 PCB with mezzanine connectors [11].
Figure 1.8 Schematic of a backplane system [15]. Graphically renewed.
As the data rate increases, the backplane channels can attenuate the transmitted signal. The channels cause inter‐symbol interference (ISI), reflection, and cross talk. Cross talk and reflection introduce noise, decrease the signal amplitude, and degrade the signal edge rate, which further deteriorates channel jitter performance. At high data rates and long distances between channels, the signal integrity becomes worse. Figure 1.9 shows the signal integrity regarding transmission distance and data rate, respectively [16]. When a clean signal passes through a long distance, its eye becomes smaller.
