Conformity Magazine - March 2008 - (Page 43)

in a wide variety of cross-sections. For low compression grounding contacts, individual fingers are available with pressure sensitive adhesive (PSA) for convenient peeland-stick application. Although the standalone electrical conductivity of fingerstock is unmatched, other factors such as the dimension and number of slots in fingerstock and surface contact area in an assembly can affect the final shielding performance. In such cases, other approaches that use conductive more compliant conductive elastomers may provide better performance. Other metal gaskets such as PCB card cages, connector and panel shields, and knitted wire mesh exist to provide a solution for static applications that require good shielding performance without the requirement for environmental sealing. Molded and Extruded Elastomers By combining an elastomer – usually silicone – with a conductive filler such as nickel/graphite, a material is created that provides both EMI shielding and an environmental seal. These materials lead to the even dispersion of the conductive filler within the elastomer, providing uniform physical and electrical performance. The elastomeric binder and the dispersed conductive filler can be manufactured into almost any shape using molding, extrusion or die-cutting processes. It is also possible to overmold the material onto plastic or metal components, thus providing a onepiece shielded housing that can simplify assembly of an appliance sub-assembly. Form-in-place (FIP) dispensing of elastomer provides faster cure time, low force-deflection and lower overall cost in high-production environments. Although other elastomers are sometimes used, silicone is usually the material of choice due to its ability to compress at low closure forces and its excellent compression set performance across a wide temperature range. Designers can expect to achieve shielding effectiveness in the region of 80dB from 100MHz to 10GHz using these types of materials. Extruded conductive elastomer gaskets can be supplied in a wide range of solid and hollow cross-section configurations. With a hollow section, conductive elastomers require even lower force in order for them to be compressed, and they also have larger deflection ranges. This makes them ideal for use in applications such as appliance door sealing where it is often difficult or inconvenient to generate high closure forces and where there may be significant tolerance build-up over long lengths. Figure 3: Z-axis conductive foam gasket marCh 2008 Conformity 3 http://www.spira-emi.com http://www.spira-emi.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - March 2008

Conformity Magazine - March 2008 NewsBreaks Editor's Note Adelstein Renominated to the FCC Industry Canada Publishes FAQs On RF Fields FDA Gives Its Scientific Capabilities Poor Marks FDA Offers Guidance On its Product Review Process FDA Publishes Updates to List of Recognized Standards FDA Warns of Patient Risk From Electric Dental Handpieces Complying with the EMC Directive, Second Edition ESD Open Forum Emerging Issues in Standards - Korean "RoHS": Not Like RoHS at All The iNARTE Informer Challenges in Testing - Field-Induced Charged Device Model: What Really Happens Design Fundamentals - EMI Shielding Technologies for Consumer Electronics Equipment Focus On...Compliance Software Buyer's Guide Additional Standards Published for the EU's ATEX Directive Additional Standards for the EU's Medical Devices Directive Also Published China to Require Bar Codes to Enhance Product Safety CPSC Releases 2007 Self-Assessment CPSC Actions in News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - March 2008

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