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It's an "abuse of language" shared by many, including manufacturers of
switches and relays of all kinds. A google search on "contact 'wiping action'" brought around 3000 hits. The few I glanced at dealt with just that topic, using those words. The only contact-related document I have readily at hand is a 3M catalog of "Electronic Interconnection Systems". Just about every connector has a specification for "wipe area" or "wiping area". Roy Lewallen, W7EL Richard Clark wrote: Hi Art, You are out of your turf. Pressure is the way all contacts work to break the insulating barrier formed by oxides. Your typical abuse of language here with "wipe" is another example that demonstrates pressure. The indiscriminate use of chemicals to treat a mechanical problem is one that I have demonstrated as being wholly unnecessary: none of your new gear, nor any old gear just acquired that works fine came with this chemical bath treatment. Long before anyone here was born, precision contacts were tapered plugs that fit into tapered sockets. The sockets were bifurcated (split in two halves) such that the plug created the closure between them with a simple insert and twist to break the layer of oxide. Note, there is no "wipe" as the twist translates the torque into pressure (wiping has nowhere to deposit what is "wiped" away in the tapered socket). No one needed sandpaper or a bottle of acid to erode the surface and corrode other parts through the solvent's vapor (a very insidious imposition). There is a very good reason why electronics manufacturers avoid acid core solder (unless they use a water wash down following board construction and faithfully use rosin core solder for touch up work - with extreme care not to mix the two solders). For contacts that have little pressure, the voltage presented across them can penetrate the barrier; however, there are applications where those voltages are not sufficient, and when the contact pressure is not enough either, you get into these problems. Mechanical TV tuners back in the early days suffered this problem and a special grease surfactant was used to insulate the contact face from corrosion while the pressure was sufficient to displace it for electrical contact. 73's Richard Clark, KB7QHC |
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