Electrolytic silver-germanium alloy plating solution, replenishing solution for electrolytic silver-germanium alloy plating solution, electrolytic silver-germanium alloy plating method, silver-germanium alloy plating film, and electrical contact material

Abstract

Provided is an electrolytic silver-germanium alloy plating solution that exhibits excellent bath stability and is capable of forming a plating film that can maintain high hardness and low contact resistance even when subjected to heat. Specifically provided is an electrolytic silver-germanium alloy plating solution containing: (1) a total of 1-100 g / L of one or both of silver cyanide and a silver cyanide salt in terms of Ag; (2) 1-30 g / L of a water-soluble germanium compound in terms of Ge; (3) a total of 0.1-50 g / L of one or both of polyethylenimine and polyacrylic acid; and (4) 3 g / L or more of a β-naphthalenesulfonic acid-formalin condensate.

Claims

1. An electrolytic silver-germanium alloy plating solution containing: (1) one or both of silver cyanide and silver cyanide salts: 1 to 100 g / L in total (Ag equivalent); (2) water-soluble germanium compound: 1 to 30 g / L in total (Ge equivalent); (3) one or both of polyethyleneimine and polyacrylic acid: 0.1 to 50 g / L in total; and (4) β-naphthalene sulfonic acid formalin condensate: 3 g / L or more.

2. Furthermore, the electrolytic silver-germanium alloy plating solution according to claim 1, further containing (5) alkali metal cyanide compound: 5 to 300 g / L.

3. The electrolytic silver-germanium alloy plating solution according to claim 1 or 2, further comprising (6) an electrically conductive salt: 1 to 100 g / L.

4. The electrolytic silver-germanium alloy plating solution according to any one of claims 1 to 3, wherein the water-soluble germanium compound is at least one selected from the group consisting of germanium dioxide, germanium halides, tetraalkoxygermanium, germanium sulfide, inorganic acid germanium salts, organic acid germanium salts, germanic acid, and germanate salts.

5. A supplement solution for electrolytic silver-germanium alloy plating, containing (3) polyethyleneimine and / or polyacrylic acid: 0.1 to 50 g / L in total, and (4) β-naphthalene sulfonic acid formalin condensate: 3 g / L or more.

6. A method for electrolytic silver-germanium alloy plating, comprising performing electrolytic silver-germanium alloy plating using the electrolytic silver-germanium alloy plating solution described in any one of claims 1 to 4.

7. A silver-germanium alloy plating film having a Ge content of 3.7 to 10.0 wt% and a Vickers hardness of 200 Hv or higher.

8. The silver-germanium alloy plating film according to claim 7, wherein the average crystallite size is 50.0 nm or less.

9. The silver-germanium alloy plating film according to claim 7 or 8, wherein the film thickness is 3 to 30 μm.

10. An electrical contact material comprising a metal substrate and a silver-germanium alloy plating film according to any one of claims 7 to 9 formed on the metal substrate.

11. The electrical contact material according to claim 10, comprising at least one intermediate layer between the metal substrate and the silver-germanium alloy plating film.

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