Advanced Materials and Design for Electromagnetic Interference Shielding

by Tong; Xingcun Colin

• ISBN13: 9781420073584
• ISBN10: 1420073583
• Edition: 1st
• Format: Hardcover
• Copyright: 2008-11-19
• Publisher: CRC Press

Summary

With electromagnetic compliance (EMC) now a major factor in the design of all electronic products, it is crucial to understand how electromagnetic interference (EMI) shielding products are used in various industries. Focusing on the practicalities of this area, Advanced Materials and Design for Electromagnetic Interference Shieldingcomprehensively introduces the design guidelines, materials selection, characterization methodology, manufacturing technology, and future potential of EMI shielding.After an overview of EMI shielding theory and product design guidelines, the book extensively reviews the characterization methodology of EMI materials. Subsequent chapters focus on particular EMI shielding materials and component designs, including enclosures, metal-formed gaskets, conductive elastomer and flexible graphite components, conductive foam and ventilation structures, board-level shielding materials, composite materials and hybrid structures, absorber materials, grounding andcable-level shielding materials, and aerospace and nuclear shielding materials. The last chapter presents a perspective on future trends in EMI shielding materials and design.Offering detailed coverage on many important topics, this indispensable book illustrates the efficiency and reliability of a range of materials and design solutions for EMI shielding.

Table of Contents

Preface	p. xiii
Author	p. xv
Electromagnetic Interference Shielding Fundamentals and Design Guide	p. 1
Concepts of Electromagnetic Interference and Electromagnetic Compatibility	p. 1
EMI Problems and Common Concerns	p. 2
EMI Emissions and Controlling Methods	p. 3
Conducted EMI Emission	p. 4
Radiated EMI Emission	p. 5
EMC Regulations and Testing Standards	p. 8
The International Standard	p. 9
FCC Standard	p. 9
European Standard	p. 10
Military Standard	p. 10
EMI Shielding Principles	p. 11
Shielding Effects in the E-Field and H-Field	p. 11
Shielding Effectiveness	p. 13
Absorption Loss	p. 14
Reflection Loss	p. 15
Multiple Reflection Correction Factor	p. 16
Shielding Modeling in Practice	p. 18
Metallic Enclosure	p. 18
EMI Gasket	p. 19
Shield with Apertures	p. 20
Cavity Resonance	p. 23
EMC Design Guidelines and EMI Shielding Methodology	p. 24
Design for EMC	p. 24
Shielding Methods and Materials Selection	p. 27
Shielding Housing and Enclosures	p. 27
Gasketing	p. 29
Integral Assembly	p. 30
Corrosion and Material Galvanic Compatibility	p. 31
Environmental Compliance	p. 32
RoHS Directive	p. 33
WEEE Directive	p. 34
References	p. 35
Characterization Methodology of EMI Shielding Materials	p. 37
Shielding Effectiveness Measurement	p. 37
Testing Methods Based on MIL-STD-285	p. 38
Modified Radiation Method for Shielding Effectiveness Testing Based on MIL-G-83528	p. 39
Dual Mode Stirred Chamber	p. 39
Transverse Electromagnetic (TEM) Cell	p. 40
Circular Coaxial Holder	p. 42
Dual Chamber Test Fixture Based on ASTM ES7-83	p. 42
Transfer Impedance Methods	p. 42
Transfer Impedance of Coaxial Cables	p. 43
Transfer Impedance Method for Shielding Effectiveness Measurement of Conductive Gaskets	p. 43
Electrical and Thermal Conductivities	p. 45
Electrical Conductivity and Contact Resistance	p. 45
Thermal Conductivity	p. 46
Permeability and Permittivity	p. 47
Permeability	p. 47
Permittivity	p. 48
Characterization of Permeability and Permittivity	p. 48
Mechanical Properties	p. 49
Uniaxial Tensile Testing	p. 49
Hardness	p. 50
Poisson's Ratio	p. 50
Stress Relaxation	p. 50
Contact Force	p. 51
Friction Force	p. 52
Permanent Set	p. 52
Surface Finish and Contact Interface Compatibility	p. 52
Corrosion and Oxidation Protection	p. 53
Noble Finish Selection	p. 53
Nonnoble Finishes	p. 54
Solderability of Surface Finishes	p. 55
Effects of Mating Cycles and Operating Environments on Contact Finishes	p. 57
Galvanic Corrosion and Contact Interface Compatibility	p. 58
Formability and Manufacturability	p. 58
Bending Formability	p. 59
Effect of Strain Hardening on Formability	p. 60
Anisotropy Coefficient	p. 61
Springback during Metal Strip Forming	p. 62
Environmental Performance Evaluation	p. 62
Thermal Cycling	p. 63
Thermal Aging	p. 63
Gaseous Testing	p. 63
Pore Corrosion and Fretting Corrosion	p. 63
Temperature and Humidity Testing	p. 64
Dust Sensitivity Test	p. 64
Vibration and Shock Test	p. 65
References	p. 65
EMI Shielding Enclosure and Access	p. 67
Enclosure Design and Materials Selection	p. 67
Magnetic Field Shielding Enclosure	p. 73
Basics of Magnetic Shielding	p. 73
Magnetic Shielding Materials Selection	p. 74
Magnetic Shielding Enclosure Design Consideration	p. 76
Shielding Enclosure Integrity	p. 78
Specialized Materials Used for Shielding Enclosure	p. 82
EMI Gaskets	p. 82
Metal Strip Gaskets	p. 82
Knitted Metal Wire Gaskets	p. 83
Metal-Plated Fabric-over-Foam (FOF)	p. 84
Electrically Conductive Elastomer (ECE) Gaskets	p. 84
Magnetic Screening Materials	p. 84
Shielding Tapes	p. 85
Thermoformable Alloys	p. 85
Honeycomb Materials	p. 85
Painted or Plated Plastic Enclosures	p. 86
Conductive Composite Shielding Materials	p. 86
Summary	p. 86
References	p. 87
Metal-Formed EMI Gaskets and Connectors	p. 89
Introduction	p. 89
Metal Strip Selection and Performance Requirement	p. 90
Copper Beryllium Alloys	p. 91
Phase Constitution and Primary Processing of CuBe Strips	p. 91
Performance and Availability of CuBe Alloys	p. 95
High-Strength Alloys	p. 95
High-Conductivity CuBe Alloys	p. 97
Nickel Beryllium	p. 97
Copper-Nickel-Tin Spinodal Alloys	p. 97
Composition and Physical Properties	p. 97
Strip Gauges and Temper Designations	p. 99
Mechanical Properties and Bending Formability	p. 100
Stress-Relaxation Resistance	p. 101
Heat Treatment and Spinodal Decomposition	p. 101
Surface Cleaning, Plating, and Soldering	p. 103
Elastic Performance	p. 103
Shielding Effectiveness	p. 104
Fatigue Strength	p. 104
Some Considerations to Improve Performance of CuNiSn Gasketing	p. 105
Copper-Titanium Alloy	p. 107
Stainless Steel	p. 108
Other Materials Options	p. 110
Phosphor Bronze	p. 110
Brass	p. 111
Nickel Silver	p. 111
Other High Strength and High Conductive Copper Alloys	p. 112
Design Guideline of Metal Gaskets and Connectors	p. 113
Primary Approaches	p. 114
Some Special Design Options	p. 115
Gasketing Design Guideline	p. 116
Fabrication Process and Types of Metal Gaskets and Connectors	p. 118
Progressive Die Forming	p. 118
Roll Forming	p. 119
Multiple-Slide Stamping	p. 120
Photoetching	p. 120
Typical Part Profiles	p. 120
Mounting Methods and Surface Mating Assurance	p. 122
Summary	p. 124
References	p. 124
Conductive Elastomer and Flexible Graphite Gaskets	p. 127
Introduction	p. 127
Raw Material Selection and Conductive Elastomer Fabrication	p. 128
Base Binder Materials	p. 128
Silicone	p. 128
Fluorosilicone	p. 129
Ethylene Propylene Diene Monomer (EPDM)	p. 129
Fluorocarbon	p. 129
Natural Rubber and Butadiene-Acrylonitrile	p. 129
Conductive Fillers	p. 129
Fabrication of Conductive Elastomer Materials	p. 130
Conduction Mechanism and Processing Optimization of Conductive Elastomer Materials	p. 131
Conduction Mechanism and Process Parameters	p. 131
Appearance Properties and Performance Evaluation	p. 133
Physical and Mechanical Properties	p. 133
Electrical Properties	p. 135
Thermal Properties	p. 137
Conductive Elastomer Gasket Design Guideline	p. 137
Flange Joint Geometry and Unevenness	p. 138
Applied Clamping/Compressive Force and Deformation Range	p. 139
Gasket Profile and Materials Selection	p. 141
Flange Materials and Joint Surface Treatment	p. 145
Conductive Elastomer Gasket Fabrication	p. 146
Extrusion	p. 146
Molding	p. 147
Form-in-Place and Screen Printing	p. 148
Reinforced Shielding Gaskets with Oriented Wires and Metal Meshes	p. 149
Conductive Elastomer Gasket Installation and Application	p. 149
Comparable Flexible Graphite Gaskets	p. 152
Flexible Graphite and Its Properties	p. 153
Fabrication and Application of Flexible Graphite Gaskets	p. 155
Summary	p. 157
References	p. 157
Conductive Foam and Ventilation Structure	p. 159
Introduction	p. 159
Waveguide Aperture and Ventilation Panel	p. 159
Waveguide Aperture and Its Design	p. 160
Materials Selection and Fabrication Options	p. 163
Conductive Foam and Integral Window Structure	p. 165
Conductive Plastic Foam and Vent Panels	p. 165
Integral EMI Window Structure	p. 168
Metallized Fabrics and Fabric-over-Foam	p. 169
Metallized Fabrics	p. 170
Fabric-over-Foam	p. 171
Summary	p. 175
References	p. 175
Board-Level Shielding Materials and Components	p. 177
Introduction	p. 177
Board-Level Shielding Design and Materials Selection	p. 178
Basic Principles of Board Circuit EMC Design	p. 178
PCB Layout	p. 178
Power Decoupling	p. 179
Trace Separation	p. 179
Grounding Techniques	p. 180
Chassis Construction and Cabling	p. 180
Board-Level Shielding Design with Proper Materials Selection	p. 181
Board-Level Shielding Components and Their Manufacturing Technology	p. 185
Metal Cans	p. 186
Single-Piece Shielding Cans	p. 186
Two-Piece Cans	p. 189
Multilevel Shielding and Multicompartment Cans	p. 190
Metal-Coated Thermoform Shields	p. 190
snapSHOT Shield	p. 191
Form/Met Shield	p. 192
Formable Shielding Film	p. 196
Conductive Coating Methods Used for EMI Shielding Components	p. 196
Electroplating	p. 197
Electroless Plating	p. 197
Electrolytic Plating	p. 198
Tin Plating and Tin Whisker Growth in EMI Shielding Systems	p. 199
Immersion Surface Finishes	p. 202
Conductive Paints	p. 204
Vapor Deposition	p. 205
Conductive Coating Application and Design Consideration for EMI Shielding	p. 206
Board-Level Shielding with Enhanced Heat Dissipating	p. 207
Minimizing EMI from Heat Sinks	p. 207
Combination of Board-Level Shielding and Heat Dissipation	p. 207
Thermal Interface Materials (TIMs) for Thermal-Enhanced Board-Level Shielding	p. 208
Summary	p. 211
References	p. 212
Composite Materials and Hybrid Structures for EMI Shielding	p. 215
Introduction	p. 215
Knitted Wire/Elastomer Gaskets	p. 215
Fabrication Process and Materials Selection	p. 216
Knitted Wire Gasket Performance	p. 218
Typical Gasket Types and Mounting Methods	p. 219
EMI Shielding Tapes	p. 221
Conductive Fiber/Whisker Reinforced Composites	p. 224
Materials Selection and Process of Conductive Composites	p. 225
Carbon Fiber/Whisker Reinforced Materials	p. 226
Metal Fiber/Whisker Reinforced Composites	p. 227
Nanofiber Reinforced Polymer Composites	p. 229
Hybrid Flexible Structures for EMI Shielding	p. 230
Electroless Metal Deposition for Reinforcements of Composite Shielding Materials	p. 231
Summary	p. 234
References	p. 234
Absorber Materials	p. 237
Introduction	p. 237
Microwave Absorber Materials	p. 238
Resonant Absorbers	p. 240
Dallenbach Tuned Layer Absorbers	p. 240
Salisbury Screens	p. 241
Jaumann Layers	p. 242
Graded Dielectric Absorbers: Impedance Matching	p. 242
Pyramidal Absorbers	p. 242
Tapered Loading Absorbers	p. 243
Matching Layer Absorbers	p. 244
Cavity Damping Absorbers	p. 244
Anechoic Chambers	p. 245
Antennas	p. 245
Absorber Materials Used in Anechoic Chambers	p. 246
Dielectric Materials for Absorber Applications	p. 246
Electromagnetic Wave Absorbers	p. 249
Absorbing Materials Selection and Absorber Applications	p. 251
Absorbing Materials and Absorber Types	p. 251
Applications	p. 252
Military	p. 252
Commercial	p. 253
Summary	p. 253
References	p. 254
Grounding and Cable-Level Shielding Materials	p. 257
Introduction	p. 257
Cable Assembly and Its EMI Shielding Design	p. 257
Cable-Level Shielding Materials	p. 261
Metallic Shielding	p. 261
Conductive Heat-Shrinkable Shielding	p. 263
Ferrite Shielding Materials	p. 264
Bonding and Grounding	p. 267
Bonding	p. 268
Grounding	p. 269
Shields Grounded at One Point	p. 270
Multigrounded Shields	p. 271
Hybrid Grounding	p. 271
Summary	p. 271
References	p. 272
Special Shielding Materials in Aerospace and Nuclear Industries	p. 275
Introduction	p. 275
Lightweight Shielding Materials for Aerospace Applications	p. 275
Lightweight Radiation Shielding Material	p. 276
Fiber Reinforced Composite Materials	p. 277
Nanomaterials	p. 279
Foam Structures	p. 280
Radiation Shielding for Space Power Systems	p. 281
Neutron Shielding Design and Materials Selection	p. 282
Shielding Materials for Earth Neighborhood Infrastructure	p. 282
Active Electromagnetic Shielding for Space Radiation	p. 283
Optimization of Space Radiation Shielding	p. 285
Nuclear Shielding Materials	p. 286
Summary	p. 289
References	p. 291
Perspectives and Future Trends	p. 293
Introduction	p. 293
Early Design-in for EMC and Optimal Design of EMI Shielding	p. 293
Advanced Materials Selection for EMI Shielding	p. 297
Materials Selection for EMI Shielding Enclosure/Cover/Barrier	p. 298
EMI Gasketing Material Selection	p. 299
Other Shielding Materials Selection	p. 301
Future Trends and Applications	p. 302
EMI Shielding Design Techniques	p. 302
Integrated Circuit-Level Shielding	p. 303
Printed Circuit Board (PCB)-Level Shielding	p. 305
Lightweight Shields for PCB-Level Shielding	p. 305
Mold-in-Place Combination Gaskets for Multicompartment Shields	p. 306
Rotary Form-in-Place Gaskets	p. 307
EMI Shielding Modules or Enclosures	p. 308
Conductive Foam with Z-Axis Conductivity	p. 308
Dent-Resistant Vent Panels	p. 309
Nanocomposite Shielding Materials	p. 309
Ultrasoft Sculpted Fabric-over-Foam	p. 310
Interconnecting Level Shielding	p. 310
EMI Control or Immunity by Software	p. 311
Summary	p. 311
References	p. 312
Index	p. 315
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