Process for chromating metallic surfaces

• US 4,082,620 A
• Filed: 04/29/1977
• Issued: 04/04/1978
• Est. Priority Date: 04/29/1977
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Inventors: Skurkiss, Peter Kenny
• Primary Examiner(s): Tufariello, T. M.
• Application Number:
  US05/792,246
• Time in Patent Office: 340 Days
• Field of Search: 204/15, 204/18 R, 204/56 R
• US Class Current: 205/135
• CPC Class Codes: C25D 11/38 Chromatising
• CPC Class Codes: C25D 5/022 using masking means

Abstract

A process is described for cathodically depositing chromate films on metal surfaces. Metal surfaces of interest are copper, and copper alloy surfaces, nickel, and nickel alloy surfaces, and iron and iron alloy surfaces. Particular electrolytic conditions and solution compositions yield chromate films which are advantageous in many applications including protection of surfaces against corrosion and improved adhesive characteristics of metal surfaces toward various films including organic (paint, etc.) films. In addition, chromate films produced in accordance with the described procedure are advantageous as plating masks for electrolytic deposition of gold.

Claims

1. A process for electrolytically producing a layer on a metallic surface said layer consisting essentially of at least 90 percent chromium and oxygen chemically combined together, including the step of passing electrical current through an anode, aqueous solution and cathode said aqueous solution comprising chromium-containing ions capable of yielding said layer on electrolysis in which the metal surface comprises at least 50 percent by weight of at least one metal selected from the group consisting of copper, nickel, and iron CHARACTERIZED IN THAT the pH of the solution is less than 7 and the solution contains ammonium ions in the concentration range from 0.005 molar to saturation and the layer is used as a mask in an electroplating process involving the plating of a metal selected from the group consisting of gold, copper, nickel and solder.

2. The process of claim 1 in which the concentration of ammonium ion is between 0.1 molar and saturation of the solution.

4. The process of claim 2 in which the ammonium ion is introduced into the solution by the addition of ammonium chloride.

5. The process of claim 2 in which the ammonium ion is introduced into the solution by the addition of aqueous ammonia solution.

6. The process of claim 1 in which the source chromium ion has a concentration range between 0.5 molar and 2.0 molar.

7. The process of claim 1 in which the chromium containing ion is Cr₂ O₇⁼.

8. The process of claim 1 in which the chromating solution has a temperature between 50°

and 90°

C.

9. The process of claim 1 in which the chromate film is patterned after formation of the film.

10. The process of claim 9 in which the patterning is done by chemical etching.

11. The process of claim 9 in which the patterning is done by sputtering.

12. The process of claim 1 in which the layer is baked after formation of the film.

13. The process of claim 12 in which the layer is baked at a temperature between 50°

and 200°

C.

14. The process of claim 1 in which the metallic surface is a copper alloy.

15. The process of claim 1 in which metallic surface with the layer is punched out so as to expose unlayered metallic surface and the unlayered metallic surface is gold electroplated so as to make an electrical contact of an electrical connector.

16. The process of claim 1 in which the layer, assuming equal density of chromium species with conventional layers, has a thickness of more than 100 angstroms.

17. The process of claim 16 in which the thickness of the layer is greater than 500 angstroms.

18. The process of claim 17 in which the layer thickness is greater than 1000 angstroms.

3. The process of claim 3 in which the concentration of ammonium ion is between 2 molar and saturation.