Method for producing metal film resistor by electroless plating

Claim 1

A method for producing a nickel-cobalt alloy film for use as a resistor, which comprises immersing a ceramic or glass base material in a stannous chloride solution, a silver salt solution and a palladium chloride solution, respectively, subjecting the thus treated base material to electroless plating in a bath containing 0.016 - 0.038 mol of cobalt ions, nickel ions in an amount to provide a molar ratio of cobalt ions to nickel ions of 6:1 to 15:1, 0.28 - 0.47 mol of sodium hypophosphite and 0.34 - 0.75 mol of sodium citrate, all bath component amounts being based on one liter of bath composition, at a bath temperature of 20°-50°C while maintaining the pH of the bath at 9.5 - 10.5 by means of ammonium hydroxide, heat-treating the resultant metal film in an atmosphere which substantially prevents oxidation of the metal film at a pressure below 10 mm Hg and temperature above 230°C, with the proviso that KT ≧ 1000 wherein K is the heat treatment temperature in °C and T is the time of the heat treatment in hours, and surface treating the heat-treated metal film in an atmosphere which causes oxidation of the metal film at a pressure above 10 mm Hg and temperature above 150°C, with the proviso that KT ≧ 200 wherein K and T are as defined above.

Claim 2

A method for producing a nickel-cobalt alloy film for use as a resistor, which comprises immersing a ceramic or glass base material in a stannous chloride solution, a silver salt solution and a palladium chloride solution, respectively, subjecting the thus treated base material to electroless plating in a bath containing 0.016 - 0.038 mol of cobalt ions, nickel ions in an amount to provide a molar ratio of cobalt ions to nickel ions of 6:1 to 15:1, 0.28 - 0.47 mol of sodium hypophosphite and 0.34 - 0.75 mol of sodium citrate, all bath component amounts being based on one liter of bath composition, at a bath temperature of 20°-50°C while maintaining the pH of the bath at 9.5 - 10.5 by means of ammonium hydroxide, heat-treating the resultant metal film in an atmosphere which substantially prevents oxidation of the metal film at a pressure below 10 mm Hg and temperature above 230°C, with the proviso that KT ≧ 1000 wherein K is the heat treatment temperature in °C and T is the time of the heat treatment in hours, and surface treating the heat-treated metal film in an atmosphere which causes oxidation of the metal film at a pressure above 10 mm Hg and temperature above 150°C, with the proviso that KT ≧ 200 wherein K and T are as defined above.