Brian, Use of metal fingers or metalized material depend solely on number of factors. First typoe of material and its finish. Many times materials like chromate has nonconductive film on it. So if you use metal gasket you will get rubbing action where thin film is being pierced and you get very low impedance contact between metal parts. As a result your gasketing has beter RFI attenuation than metalized material. The metalized fabric or metalized polymer only works well if metal is highly conductive like galvanil.
As far as IEC 950 and product safety the important factor is sharp edges wher user might cut his skin. What you need to evaluate first how much you can attenuate source , secondly what apretures can you tolerate and then based on material and its finish chouse gasketing material that is not sharp and provides low RF impedence between metal parts. I would always prefer metal gaskets oveer polymer or conductive maaterial because not every time you can depend on highly conductive surface, many cleaning solvents leave thin coat of film that require rubbing action when panels are installed. Jan Purwin Jon D Curtis wrote: > From: [email protected] > Subject: EMI gaskets > > I am interested in hearing the experiences of anybody out there who has > had a need for using EMI gaskets, in particular between metal > faceplates of circuit packs in a Telecomms Sub-rack. > > We have evaluated BeCu finger stock and foam covered with a metallised > fabric and have found the metal fingers out-performed the foam. But, > due to customer complaints relating to safety hazards posed by the > metal fingers we are being pressured to use the foam. Has anybody else > faced similar problems ? > > >From our experience, if the fingers are designed suitably for the > application and applied correctly there should not be a hazard. My > reading of IEC950/EN60950/UL1950 does not indicate any prohibitive > clause relating to metal fingers. The closest (4.1.4) only stipulates > protection of the OPERATOR and does not refer to SERVICE PERSONNEL, who > would be the only persons exposed to the risk i.e. it is only when a > module is withdrawn from a shelf that the fingers are exposed (our > equipment is Central Office type). > > Does anybody know of any safety/regulatory objective reasoning for not > using fingers, if correctly designed-in, in an application such as ours > ? > > Regards, > > Brian McAuliffe > > Regulatory Engineering > Tellabs Ltd > Tel: íľť.61.703269 > > --openmail-part-000dbaa0-00000001 > > --openmail-part-000dbaa0-00000001--
