We are endeavouring to develop a new EMC compliant sub-rack using steel as a base metal. Having observed what appears to be the most common practice solution for EMC/EMI connectivity, I doubt that many would provide EMI compliance if undisturbed for extended periods.
The solutions I have commonly observed are typically bright nickel plated steel sub-racks and module panels, connected using either beryllium copper or stainless steel gaskets. While these metals provide a low electrochemical potential difference, surely oxidization will in time provide an open circuit to the low induced signal levels for which these connections should provide a low impedance path. I also presume this would not be obvious by open field measurement as the disturbance in transporting the equipment to a remote test site would generally have temporarily disturbed the insulating oxidation. For the obvious reason of cost, I have not seen gold contacts used for commercial EMI screening, but as for low signal connectors, is this the only reliable solution? Any recommendations or comments would be greatly appreciated. Rod Mason Datacraft Technologies
