EMI
L O G
CATA
www.lairdtech.com
ABOUT
LAIRD TECHNOLOGIES
Laird Technologies designs and manufactures customized, performance-critical
products for wireless and other advanced electronics applications.
The company is a global market leader in the design and supply of electromagnetic
interference (EMI) shielding, thermal management products, specialty metals,
signal integrity components, and wireless antennae solutions, as well as radio
frequency (RF) modules and systems.
Laird Technologies is the world leader in the design and manufacture of customized,
performance-critical products for wireless and other advanced electronics
applications. Laird Technologies partners with its customers to customize product
solutions for applications in many industries including:
• Network Equipment
• Handsets
• Telecommunications
• Data Transfer & Information Technology
• Computers
• Automotive Electronics
• Aerospace
• Defense
• Medical Equipment
• Consumer Electronics
• Industrial
Laird Technologies offers its customers unique product solutions, dedication to
research and development, as well as a seamless network of manufacturing
and customer support facilities across the globe.
TABLE OF
CONTENTS
EMI INTRODUCTION
EMI SUMMARY
BOARD LEVEL SHIELDS
Product Selection Guide
Introduction
Standard Design Shields
EZ Peel
™
Rigid Corner
ReCovr
™
ReMovl
Overview
2
3
6
6
8
9
11
11
12
12
13
14
14
15
16
17
18
18
19
21
21
22
22
23
24
25
26
27
28
29
31
31
32
32
33
33
34
34
35
35
36
36
37
37
38
38
39
39
39
39
40
Fiber Optic Shield
GBIC Fiber Optic Shield
"D" Connector Shielding / Slotted "D"
Precision Stamped Metals
Contacts
Custom Design
Metals Galvanic Compatibility Chart
40
40
41
42
42
44
46
48
49
50
51
52
52
54
56
57
58
62
65
66
67
68
69
70
72
75
76
77
78
79
79
80
81
85
86
87
93
95
99
102
103
105
105
106
109
110
111
112
113
VENT PANELS
MaxAir™
Elecro-Air™
Electrovent™
FINGERSTOCK
Product Selection Guide
Introduction
Mounting Methods
Ordering Information
UltraSoft
®
Series
Recyclable Clean Copper
Slot Mount Series
Dual Slot Series
Teardrop Series
Compact PCI Symmetrical Mount
Alternate Slot Series
Variable Slot Mount
Symmetrical (S
3
) Slotted Shielding
Solid Top (S
3
) Symmetrical Slotted Shielding
Clip-On Symmetrical Shielding
No Snag Gasket
All-Purpose Series
Clip-On Series
Low Profile Hook-On Gasket
Low Profile Gasket
Large Enclosure Series
Double-Sided Contact Series
Foldover Series
Stainless Steel I/O Shielding
Flexible Low Compression Series
Clip-On Twist Series
Twist Series
Divider Edge Shielding
Card Guide Clip-On
Clip-On Perpendicular Shielding
Clip-On Perpendicular Grounding Strip
Clip-On Longitudinal Grounding Strip
Mini-Longitudinal Grounding Gasket
Longitudinal Grounding Series
Custom Stamping
Contact Strips / Contact Rings
IEEE 1394 Horizontal Connector Gasket
DIN Connector Series
USB Connector
FABRIC-OVER FOAM
Product Selection Guide
Introduction
EcoGreen™
I/O / Gasket Selection Guide
Profile Selection Guide
I/O Selection Guide
Knitted Conductive Gaskets
Visual Part Reference Guide
Part Number Cross Reference
Ultraflex
®
All Mesh
Elastomer Core
Electroground
®
EMI Washers
Electromesh
®
Tape
Conductive Fabric
MRI "A" Fabric
Conductive Tape
ELECTRICALLY CONDUCTIVE ELASTOMERS
Introduction
Product Selection Guide
Case Study
Visual Part Reference Guide
Electroseal
™
Conductive Elastomer
Extrusions Guide
Gemini
™
Coextrusions
Fabricated Components Guide
Metal Impregnated Materials
Specialty Products
Automated Form-In-Place Gaskets
MICROWAVE ABSORBERS
Product Selection Guide
Design Guide
Q-Zorb
®
2000 HF
Q-Zorb
®
3000 HP
RFRET 4000
RFLS 5000
Analysis, Test and Prototype Development
www.lairdtech.com
EMI ESSENTIALS
EMI INTRODUCTION
Overview of EMC/RFI Issues
The phenomenon of electromagnetic interference (EMI) is familiar to virtually everyone, even if they do not
understand the underlying principles. Most people have witnessed firsthand the effects of interference.
To control EMI, government organizations, such as the FCC, CSA, and EEC, mandate that manufacturers may
not design, produce or sell electronic equipment that jams the public broadcast services. In other instances,
however, EMI can constitute more than a mere nuisance. The military and medical communities, for example,
require trouble-free operation of their electronic equipment in adverse electromagnetic environments since
malfunctions could jeopardize missions and personnel. The European Union’s EMC directive also mandates
that “the apparatus has an adequate level of intrinsic immunity to electromagnetic disturbance to enable it
to operate as intended”.
EMC Design of High Speed Systems
The interference and susceptibility (immunity) effects of electronic apparatus are created by time-variant
electromagnetic fields which may be propagated along a conducting medium or by radiation through space.
Because the source of the conducted and radiated interference energy levels may be related, a coordinated
systems design effort is required to reduce these effects.
A design program for an equipment item that must meet both an emission and an immunity requirement
consists of:
• Suppression: Reducing the interference at its source.
• Isolation: Isolating the offending circuits by filtering, grounding and shielding.
• Desensitization: Increasing the immunity of any susceptible circuits.
These three steps should be carried on throughout the entire equipment design and implemented as early
as possible within the design program.
Effects of Logic Speed
The trend in today’s electronic devices is faster, smaller, and digital rather than analog. Most equipment
(95%) of today contains digital circuits. Today’s digital designer must create a circuit board that has the
lowest possible EMI, combined with the highest possible operating/processing speeds. Design of the PCB
is the most critical EMC influencing factor for any system, since virtually all active devices are located on
the board. It is the changing current (accelerated electron movement) produced by the active devices that
result in EMI.
Design Approaches
There are two approaches that can be used to reduce the emission from the PC board. The first approach is
to operate the circuit at the slowest speeds consistent with the functionality of the system, lay out the PCB
with the smallest possible loop areas (especially the high speed devices), and insert suppression components
such as filters, ferrite beads, and bypass capacitors into the circuit to reduce its bandwidth. These techniques
will result in a desired decrease in the high frequency harmonic amplitudes and circuit bandwidth and a
corresponding undesired decrease in both the operating speed and system reliability. The use of slower
speeds with reduced bandwidth will help to desensitize the circuit to external susceptibility fields.
The second is to use shielding. Shielding is the only non-invasive suppression technique. Since the shielding
is not inserted into the circuit, it does not effect the high frequency operating speed of the system, nor does
it effect the operation of the system should changes be made to the design in the future. In addition,
shielding does not create timing problems and waveform distortion; it does not decrease system reliability;
and it reduces crosstalk. Plus, shielding works for both emission suppression as well as susceptibility
(immunity) problems.
2
Even with the overall advantages of shielding, the most cost-effective approach is to use a combination
of circuit suppression/hardening and shielding.
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Fabric-Over-Foam and Conductive Foam
Applications
• Shielding or grounding of computer and
telecommunication equipment seams
and apertures
Wire Mesh
• Covers opened infrequently for servicing
(6-12 times per year)
• Long lasting resiliency is ideal for highly
sensitive components in permanent or
semi-permanent enclosures
• Consistent point-to-point contact for high
shielding effectiveness over the life of the
gasket
• Most economical gasket for low-cycling
applications
• High shielding effectiveness over broad
frequency range
• Available in wide variety of sizes and shapes
• Knit construction for long lasting resiliency
• Versatile mounting options
• Available with elastomer gasket for moisture
and dust sealing
90 - 105 dB
Tape
• Design flexibility provides grounding and
shielding solutions for I/O shielding panels,
disk drive insulators, ground planes or circuit
boards, electromedical devices, keyboard
devices
• Mask-and-peel tape for painted electronic
enclosures
• Cable and wire harness wrapping
• Simple installation
• Ideally suited for thin or low-profile
applications
• Conductive foil tape with release mask for
painted enclosures
• Tin copper cloth and nickel copper cloth
versions provide easy-to-handle alternatives
to foils
—
Features and Benefits
Product Highlights
• UL 94VO and HB flame retardant
• Ideal for applications requiring low
pressure force
• Self-terminating cut-to lengths
• High conductivity and shielding attenuation
• Galvanically-compatible with most mating
surfaces
• High abrasion and shear resistance
>85 dB
Electrical Shielding
Effectiveness
Transfer Impedance (500 MHz)
H-field (200 MHz)
Modified Mil 285
Plane Wave (2 GHz)
Modified Mil 285
Surface Resistivity
Volume Resistivity
Mechanical
Available Size Range
30 - 45 dB
90 - 100 dB
<0.07 ohms/square
N/A
Height: 0.015 - 0.945 (0,038 - 24,0)
55 - 65 dB
80 - 115 dB
N/A
0.0004 - 0.114 ohm-cm
Height: 0.062 - 0.500 (1,57 - 12,7)
—
85 - 95 dB
Low surface resistivity based on material selection
N/A
Width: 0.025 - 2.00 (6,4 - 50,8)
Thickness: 0.003 - 0.007 (0,08 - 0,18)
Deflection Operating Range
20 - 75% deflection
20 - 70% deflection
N/A
Compression Force
(based on shape selection)
3 - 10 Ibs/in. ft. (4,5 - 15,0 Kg/m)
@ 20% deflection (dependent on foam
selection and shape)
<4 - 20% @ 50% deflection
0.020 - 0.050 (0,51 - 1,27)
From 6 - 50 Ibs/in. ft.
(8,8 - 74 Kg/m) round
N/A
Compression Set
Joint Unevenness
Accommodation
Compound/Material
Availability
10% @ 20% compression
0.010 - 0.300 (0,25 - 7,6)
N/A
N/A
Tin-plated copper, copper foil, nickel copper
cloth tape
Cover: Flame retardant metallized Ni/Cu,
BeCu, Monel, aluminum, tin-plated steel,
Tin/Cu and silver woven or non-woven textile. tin-plated brass, Enviroseal version with
Core: Flame retardant urethane, TPE
neoprene or silicone
Temperature Range
Available Profiles
-40 - 158°F (-40 - 70°C)
Enviroseal -103 - 500°F (-75 - 260°C)
50 - 500°F (10 - 260°C) based on material
selection
Rolls
Round, rectangular, square “D”, “C”, “J”, “P”, Round, rectangular, square, single-round with
“U”, clip-on, knife edge
fin, double-round with fin
Groove, PSA, clip-on, dart
Cut-to lengths, mitered and spliced corners,
kiss-cut, other profiles
N/A
Groove, pressure-sensitive adhesive,
mechanical fasteners, channel mount
Cut-to lengths, mitered corners, flat tape, and
EMI washers
Enviroseal product only: moisture, rain
Mounting Methods
Custom Shapes Available
Pressure-sensitive adhesive, conductive or
non-conductive
Die-cut shapes
Environmental
Fluid Seal
Air/Dust
Galvanic Compatibility
N/A
Provides barrier against dust
Compatible with a wide variety of mating
surfaces—zinc, aluminum, stainless steel, etc.
Enviroseal product only
Variety of platings to ensure galvanic
compatibility with mating surface
N/A
Wide variety of materials available to meet
galvanic compatibility requirements
3
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