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LAMINATES & GROUNDING PRODUCTS Conductive Grounding Tabs Adequate EMI protection often can be achieved by establishing low impedance ground paths between electrically conductive elements in the chassis and components. Conductive Grounding Tabs Electromagnetic interference (EMI) is frequently induced by surface currents exciting metal components to create “phantom” fields. As a generality, all metal elements should be bonded to a common ground. In some cases, conductive “tabs” provide the required grounding paths at lower costs than modifying a design or installing enclosure shielding. For example, slot length in enclosure seams can be reduced effectively using conductive tabs at appropriate intervals. With wavelength the determining factor, the smaller slot size may limit leakage sufficiently to circumvent continuous gasketing. This will provide a cost savings. Within enclosures, grounding tabs may reduce radiated EMI levels from a PCB ground plane saturated with signals. Board-mounted component shields, such as metal cans, can be grounded with conductive tabs inserted between the shield and enclosure wall. MATERIALS AND FORMS Virtually any suitable Chomerics EMI shielding material used in continuous lengths can be cut-to-length as grounding tabs. These include different profile conductive elastomers, conductively jacketed foam, knitted wire mesh and springfinger strips. Pressure-sensitive adhesive (PSA) is standard on many of these, and generally available on any material and configuration other than an O-profile. Elastomer and foam strips are supplied as continuous lengths, cut-tolength pieces, or kiss-cut parts on tape or film release sheets. Kiss-cut parts abut each other, while individual pieces can be spaced on film sheets in specified intervals for “pick and place” application. Individual springfingers can be supplied on film sheets, or as manually snapped off individual lengths. SELECTING THE SOLUTION Choosing a material typically relates more to physical suitability than to grounding performance. Since various materials offer comparable grounding, but differ widely in composition and construction, material selection should consider: • Compression/deflection • Compression set • Friction/shear forces • Flammability • Durability, abrasion, closure cycles • Corrosion More than one material may provide a cost-effective grounding solution. A typical scenario is the identification of radiated EMI during certification testing of a device, with on-the-spot resolution using available samples. Many commercial test laboratories use samples supplied by Chomerics for expedient problem solving. Customers preparing for product testing are welcome to request grounding tab samples. Contact our Applications Engineering Department. SOFT-SHIELD ® 5000 Series Conductive Fabric-Wrapped Foam Nickel-plated silver imparts conductivity to the self-terminating, nylon rip-stop jacket of this highly compressible foam gasket. Closure force of
SPRING-LINE ® “Pick and Stick” Springfingers Highly resilient, 0.002 inch (0.051 mm) thin fingers compress under low closure force. Their tin-plated beryllium copper construction provides excellent conductivity and galvanic corrosion resistance. In a typical application, springfinger tabs affixed to metal cans soldered over board components establish contact between adjacent PCBs, simplifying grounding to the housing. Tight compression does not affect resilience or electrical performance. Parts include high-tack pressuresensitive adhesive on the mounting surface, and are supplied in strips for snap-off application, as individual pieces, or spaced on film reels for “pick-and-stick” application. For more information on SPRING-LINE Springfingers, refer to page 126. SHIELD MESH TM Compressed Mesh Buttons Knitted wire mesh that has been diecompressed into cylindrical configurations exhibits significant resilience when compressed under load and released. Mesh buttons provide a low impedance ground contact in applications such as slide-out drawers in an enclosure rack. Integral compression stops can be included. Since the material compresses under load, no allowance is required for lateral deflection. Standard wires include aluminum, monel (nickel-copper alloy) or Chomerics’ Ferrex tin-plated-copper clad steel. For detailed information on SHIELD MESH Compressed Mesh, refer to page 115. CHO-BUTTON TM EMI Grounding Contacts Consisting of a molded CHO-SEAL conductive elastomer cap and integral thread-cutting screw, CHO-BUTTON contacts can provide an alternative to continuous conductive gasketing in flange joints. When spaced at 4 to 8 inch (102 to 203 mm) intervals, >40 dB shielding effectiveness is achieved between 20 and 200 MHz. Their design, resilience and flexibility accommodate wide joint gap tolerances, even under low closure forces. For more information on CHO-BUTTON EMI Grounding Contacts, refer to page 156. CHO-SEAL ® and CHO-SIL ® Conductive Elastomer “Peel and Stick” Tabs With many standard sizes and material choices, conductive elastomer extrusions afford real design flexibility for grounding applications when supplied kiss-cut on PSA mounting tape. Hollow D profiles, available as small as 0.125 (3.18 mm) wide, are typically chosen, but others may be used, including custom profiles. Cost and performance options include a choice of conductive particle fillers in silicone or fluorosilicone binders. All offer excellent resistance to compression set over a wide temperature range. Grounding tabs can also be produced using molding techniques that accommodate special design features or geometries. For detailed information on conductive elastomer extrusions, refer to page 35. PRODUCT SOFT-SHIELD 5000 SOFT-SHIELD 4000 SOFT-SHIELD 2000 SPRING-LINE SHIELD MESH CHO-SEAL & CHO-SIL Series Foam Series Foam Series Foam Springfingers Buttons Conductive Elastomers Standard Rectangular, D, V, C, Flat rectangular, Rectangular, D Various Cylindrical Solid and hollow O, D, Profiles P and others die-cut shapes P, rectangular Custom Profiles Yes Yes Yes Yes Yes Yes Construction/ Nickel-plated silver Fabric-reinforced Silver-plated Beryllium- Knitted monel Conductive particle Composition nylon ripstop fabric aluminum foil yarn over thermo- Copper or Ferrex ® wire filled silicone or over urethane over urethane plastic EPDM foam fluorosilicone extrusion Attachment Non-conductive Conductive Non-conductive Non-conductive Friction Fit Non-conductive PSA PSA PSA PSA PSA Continuous Lengths Yes Yes Yes Yes Supplied as Yes Kiss-cut, Tape Yes Yes — Yes individual Yes Kiss-cut, Film Sheet Yes Yes — Yes parts Yes Cut-to-Length Pieces Yes Yes Yes Yes Yes Grounding Effectiveness 2 2 3 1 2 2 (1 = highest) US Headquarters TEL +(1) 781-935-4850 FAX +(1) 781-933-4318 • www.chomerics.com Europe TEL +(44) 1628 404000 FAX +(44) 1628 404090 Asia Pacific TEL +(852) 2 428 8008 FAX +(852) 2 423 8253 South America TEL +(55) 11 3917 1099 FAX +(55) 11 3917 0817 155
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Chomerics is the world’s largest
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Contents COST-EFFECTIVE SOLUTIONS F
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Cost-Effective Solutions for Major
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As Lead Supplier, Chomerics... Prov
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Shielding Solutions for Wireless Co
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SHIELDING SOLUTIONS FOR WIRELESS CO
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Table 2 Table 1 *Copies of CHO-TM-T
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stable platform for direct, high pr
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SHIELDING SOLUTIONS FOR WIRELESS CO
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gaskets will typically save 60% or
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Table 1 TYPICAL PROPERTIES OF CHO-F
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Optimizing the design of Cho-Form S
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Optimizing the design of Cho-Form S
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Conductive Elastomer Gaskets SECTIO
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Material Selection Chomerics’ arr
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Table 2 continued Equipment Materia
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Table 3 continued Test Procedure CH
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Conductive Elastomer Extrusions...
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Bonded gaskets — Similar and diss
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Table 2 EXTRUSION MANUFACTURING GUI
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Standard Extrusion Sizes Table 7 ,,
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Table 8 continued HOLLOW O-STRIPS C
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Table 11 continued Chomerics P/N* M
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C Table 15 A Chomerics P/N MIL P/N:
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19-09-12023-XXXX 19-08-12057-XXXX 1
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19-09-15245-XXXX 19-09-15486-XXXX 1
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19-05-E328-XXXX 19-08-F676-XXXX 19-
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CONDUCTIVE ELASTOMERS Co-Extruded S
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19-18-15351-XXXX 19-18-M391-XXXX 19
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Table 2 STANDARD SHEET STOCK SIZE A
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,,,,,,,,,,,, ,,,,,,,,,,,, ,,,,,,,,,
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,, ,,,,, ,,,,, ,,,, CONDUCTIVE ELAS
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Table 3 continued Chomerics P/N* MI
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CONDUCTIVE ELASTOMERS Waveguide Gas
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Table 2 continued Frequency Range (
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,,,, Table 4 Note: Raised portion w
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temperatures to 125°C, and CHO-SEA
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Jam Nut EMI Seals MIL-C-38999, MIL-
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CONDUCTIVE ELASTOMERS Molded-In-Pla
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Table 1 ELASTOMER SPECIFICATIONS FO
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Load, lb./inch Load, lb./inch 20 10
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Stress Relaxation As important as C
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Heat Aging The primary aging mechan
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CONDUCTIVE ELASTOMERS Part Number I
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19-06-11223-XXXX . . . . . . .Hollo
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SOFT-SHIELD® Low Closure Force, Fo
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LOW CLOSURE FORCE, FOAM CORE EMI GA
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ORDERING INFORMATION Referring to T
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Table 6 KNIFE-EDGE STRIPS OTHER SOF
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Table 1 TYPICAL PROPERTIES FOR SOFT
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LOW CLOSURE FORCE, FOAM CORE EMI GA
Page 103 and 104: LOW CLOSURE FORCE, FOAM CORE EMI GA
Page 105 and 106: Metal EMI Gaskets, Clip-on Gaskets
Page 107 and 108: METAL EMI GASKETS MESH STRIP All M
Page 109 and 110: METAL EMI GASKETS MESH STRIP with
Page 111 and 112: METAL EMI GASKETS SPRINGMESH ® Hig
Page 113 and 114: Fabricated COMBO GASKETS: Select th
Page 115 and 116: METAL EMI GASKETS SHIELDMESH Compr
Page 117 and 118: Table 2 SINGLE EMI/EMP FRAME GASKET
Page 119 and 120: Width Table 2 POLASHEET COMPOSITE G
Page 121 and 122: METAL EMI GASKETS METALASTIC ® & P
Page 123 and 124: METAL EMI GASKETS METALKLIP ® Clip
Page 125 and 126: SHIELDING EFFECTIVENESS Figures 8-1
Page 127 and 128: TWIST SERIES FOLD OVER PART NO. 81-
Page 129 and 130: RIVET & TRACK PITCH .190 (4.83) PAR
Page 131 and 132: METAL EMI GASKETS SPRING-LINE ® St
Page 133 and 134: Conductive Compounds Adhesives Seal
Page 135 and 136: CONDUCTIVE COMPOUNDS CHO-BOND ® Co
Page 137 and 138: Table 1 continued SPECIFICATIONS AN
Page 139 and 140: Silicones and Flexible Polyisobutyl
Page 141 and 142: • CHO-SHIELD 4900 silver-filled a
Page 143 and 144: Engineered Laminates & Grounding Pr
Page 145 and 146: Ordering Procedure CHO-MASK II tape
Page 147 and 148: Table 1 Property Test Method Typica
Page 149 and 150: LAMINATES & GROUNDING PRODUCTS EMI
Page 151 and 152: Table 1 SPECIFICATIONS Property Tes
Page 153: LAMINATES & GROUNDING PRODUCTS CHO-
Page 157 and 158: EMI Shielded Vents SECTION CONTENTS
Page 159 and 160: Customization Options • Alternati
Page 161 and 162: EMI SHIELDED VENTS CHO-CELL Shield
Page 163 and 164: Round SHIELD CELL and OMNI CELL Pan
Page 165 and 166: EMI SHIELDED VENTS SLIMVENT Shield
Page 167 and 168: EMI SHIELDED VENTS Common Parts Tab
Page 169 and 170: EMI Shielded Windows & Contrast Enh
Page 171 and 172: Substrate and Surface Treatment Lig
Page 173 and 174: WIN-SHIELD Windows EMI Shielding Pe
Page 175 and 176: Cable Shielding SECTION CONTENTS PA
Page 177 and 178: BEADS ON LEADS Impedance-Frequency
Page 179 and 180: Table 5 continued Dimensions - Inch
Page 181 and 182: FLAT SPLIT CABLE CORE Impedance-Fre
Page 183 and 184: CABLE SHIELDING CHO-DROP ® EMI Abs
Page 185 and 186: Figure 2 Table 2 STRAIGHT LENGTHS i
Page 187 and 188: Connector Boots and Cable Transitio
Page 189 and 190: CABLE SHIELDING CHO-JAC ® Flat Cab
Page 191 and 192: EMI Shielding Theory & Gasket Desig
Page 193 and 194: E i Current on front wall due to re
Page 195 and 196: Figure 7 Magnetic Field Reflection
Page 197 and 198: E = D 2 G ,,,, ,,,, ,,,, ,,,, G D =
Page 199 and 200: Table II Group Material Groupings*
Page 201 and 202: Non-Conductive Sealing Gasket Volum
Page 203 and 204: enclosure, or by using an insert si
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Gasket Mounting Choices Our various
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Actual deflection vs. distance betw
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percentage increase required to sat
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Figure 28d Section B-B from Figure
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Formulas (see definition of terms a
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in the unit price of the gasket. Bo
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Wire Mesh EMI Gasket Selection Guid
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Relative Conductivity: Conductivity
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Global Compliance Testing Page 222
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TEST SERVICES FCC, CSA, CISPR, VCCI
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THERM-A-GAP TM Thermally Conductive
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