The Influence of Coating Technology on Contact Resistance During Life Testing of Reed Switches

Reed switches fail in one of two ways: the switch will fail to open when expected (stick) or it will fail to close when expected (miss). During life testing at rated power it was found that switches with plated contacts exhibited variable and gradually increasing contact resistance up to the first stick followed by very stable contact resistance after the first stick. For reed switches with sputtered contacts, variable and gradually decreasing contact resistance was observed up to the first stick followed by an abrupt increase in contact resistance which then stabilized. End of life failure analysis is used to explain these different behaviors.