Cold welding of latching relay contacts

When the latching relay contacts work in the closed state, in addition to some faults caused by the above-mentioned contact resistance, an accident called "cold welding" often occurs in miniature latching relays, especially reed latching relays. can't be togetherfreed. The cause of this cold welding is generally considered to be that the contact surface of the contact is under the action of pressure or slip, the surface film is destroyed, the direct metal contact area increases, and the total affinity between metal molecules increases. If the breaking force at this time is not enough (thisThe contact breaking force of similar latching relays is usually very small), and the contacts are stuck and cannot be separated.

Therefore, in order to prevent the occurrence of cold welding, it is best to keep a surface film on the joint. But this again contradicts the requirement to reduce the contact resistance. Therefore, how to take into account the two and seek unity has become the key to the development of this type of latching relay. At present, research and tests are being carried out at home and abroad, and some measures can be used to reduce the contact resistance and reduce the occurrence of cold welding. For example, the cold welding of reed latching relay contacts can be greatly improved by using appropriate surface coatings (such as plating or nails or hard gold with weak cobalt acid).