flat flexible cables and flat flexible assemblies - Axon Cable - #9

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RELEASED AUGUST 2009 - www.axon-cable.com © 2009/A - AXON’ CABLE - FLAT FLEXIBLE CABLES AND FLAT CABLE ASSEMBLIES 8 Shielding with conductive silver Paint Microstrip injection test bench to control transfer impedance Shielding expertise AXON’ offers two types of shielded flat cables: ›› Cables shielded with aluminium tape, ›› Cables shielded by a conductive silver paint and a protective varnish. AXON’ is able to ground one or several conductors to the shield irrespective of the type of shielding: aluminium foil or conductive paint (same voltage level and EMI performance). To characterise the shielding of flat or round cables, AXON’ uses the “Transfer Impedance ZT" parameter given in ohms/m. As this notion depends on the type of product, rather than on the application, it is better suited than the alternative notion of “shielding efficiency”, given in dB, to define shield specifications accurately. AXON’ is equipped with comprehensive test benches to characterise transfer impedance of round and flat cables as well as terminated harnesses. The flat cables are generally measured using a microstrip or strip line. In order to propose the shielding solution best suited to each application, AXON’ has compared the shielding resistance of cables shielded with aluminium foil to those shielded with conductive paint. Measurement of the shield resistance Shield efficiency is measured on a network analyser using the microstrip method. The connection between the flat cable and the coaxial cable of the network analyser is made possible with an interface PCB which links the flat cable’s ZIF connectors to the coaxial connectors. AXON’s standard shielded FFC's are usually used for static applications. For dynamic applications, please contact us for more details. 0,01 0,1 1 10 0,01 0,1 1 10 Transfer impedance Zt (mOhms) Frequency (MHz) Grounded Alu shield - P=1,00mm Grounded Painted shield - P=1,00mm Not grounded Alu shield - P=0,50mm Grounded Painted shield - P=0,50mm This graph shows the quality of shielding of four different cables in terms of transfer impedance. The lower the transfer impedance (ZT ) the more efficient the shielding.