Coated wire and film resistor
A coated wire is solderable with soft solder while maintaining separate phases of the core and the coating. A 100 μm to 400 μm thick nickel wire may be coated galvanically with silver. For a film resistor with coated wires as connection wires, including a platinum measurement resistor on an electrically insulating substrate and connection wires connected to the measurement resistor, the connection wires have a coated nickel core. The coating may be made of silver or glass or ceramic or a mixture of these materials, or on its outside may be made of glass or ceramic or a mixture of these materials. For producing film resistors a thin metal or glass component is deposited on a connection wire connected to a track conductor arranged on an electrically insulating substrate, and a thick glass paste is deposited and fired on this metal or glass component. For mass production of film, several film resistors encased together in glass may be partitioned by fracturing.
1. A film resistor comprising a platinum measurement resistor on an electrically insulating substrate and connection wires connected to the measurement resistor, wherein the connection wires consist essentially of a coated core, and wherein the core comprises nickel and the coating consists essentially of silver or a mixture of silver with glass or ceramic.
2. The film resistor according to claim 1 , wherein the silver coating or a silver phase of the coating or the nickel core has a purity of at least 99 wt.%.
3. The film resistor according to claim 1 , wherein the nickel core has a diameter of 100 μm to 400 μm, and the silver coating is 0.2 to 5 μm thick.
4. The film resistor according to claim 1 , wherein the coating of the connection wires is not endangered, with respect to its electrical conductivity and in terms of its mechanical properties, by diffusion of a material of the core.
5. The film resistor according to claim 1 , wherein the measurement resistor and the connection wires are covered with glass or glass ceramic in a region of their ends attached to the measurement resistor.
6. The film resistor according to claim 1 , comprising an electrically insulating surface of the substrate, a track conductor arranged thereon, two connection wires connected to the track conductor, and a glass cover sealing the track conductor and ends of the connection wires connected to the track conductor.
7. A method for producing a film resistor having a measurement resistor and a coated wire connected thereon according to claim 1 , the method comprising bonding the coated wire to contact surfaces of the measurement resistor in an electrically conducting manner by thermocompression.