US5022968A
Expired / Lapsed
US
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Method and composition for depositing a chromium-zinc anti-tarnish coating on copper foil
Assignee: GBC Metals LLC
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Filing: 1990-09-20
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Granted: 1991-06-11
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Expires: 2010-09-20
Abstract
Abstract A technique for improving the tarnish and oxidation resistance of copper and copper based alloy materials is disclosed. Copper or a copper alloy is immersed in an aqueous solution containing sodium hydroxide, zinc ions and chromium (VI) ions. While the compositional ranges may vary, the concentration of either zinc ions or chromium (VI) ions, or both, is less than 1.0 gm/l. A chromium-zinc coating is electrolytically applied. The coating provides tarnish resistance at temperatures in excess of 190 DEG C. The coating is removable by immersion in sulfuric acid. Improved results are obtained by rinsing deionized water containing a small amount of an alkaline or alkaline earth hydroxide.
Inventors
- 👤 Lifun Lin
- 👤 Chung-Yao Chao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 11:59
CPC Classifications
C; C25; C25D; C25D3/00; C25D3/02; C25D3/56; H; H05; H05K; H05K3/00; H05K3/38; H05K3/382; H05K3/384; H05K2201/00; H05K2201/03; H05K2201/0332; H05K2201/0335; H05K2201/0355; H05K2203/00; H05K2203/07; H05K2203/0703; H05K2203/0723; H05K3/22; H05K3/24; H05K3/244
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
90 words
A basic solution having hydroxide ions for electrolytically depositing an anti-tarnish coating on a copper or copper based alloy foil, comprising: from about 0.07 grams per liter to about 10 grams per liter zinc ions supplied in the form of a water soluble zinc compound;and from about 0.1 grams per liter to about 100 grams per liter of chromium (VI) ions in the form of a water soluble hexavalent chromium salt wherein the concentration of either said zinc ions or said chromium (VI) ions or both is less than 1.0.
Claim 2
Dependent Claim
90 words
A basic solution having hydroxide ions for electrolytically depositing an anti-tarnish coating on a copper or copper based alloy foil, comprising: from about 0.07 grams per liter to about 10 grams per liter zinc ions supplied in the form of a water soluble zinc compound;and from about 0.1 grams per liter to about 100 grams per liter of chromium (VI) ions in the form of a water soluble hexavalent chromium salt wherein the concentration of either said zinc ions or said chromium (VI) ions or both is less than 1.0.
Claim 3
Dependent Claim
21 words
The solution of claim 1 wherein said hydroxide ions are supplied in the form of either sodium hydroxide or potassium hydroxide.
Claim 4
Dependent Claim
39 words
The solution of claim 2 wherein said hydroxide ions are supplied as sodium hydroxide, said zinc ions as zinc oxide and said water soluble hexavalent chromium is selected to be Na 2 Cr 2 O 7 .2H 2 O.
Claim 5
Dependent Claim
42 words
The solution of claim 3 having the composition: from about 10 to about 50 grams per liter NaOH; from about 0.16 to about 1.2 grams per liter zinc ions; and from about 0.08 to about 0.78 grams per liter chromium (VI) ions.
Claim 6
Dependent Claim
51 words
The solution of claim 4 wherein the composition of said solution is: from about 10 to about 25 grams per liter NaOH; from about 0.2 to about 1.5 grams per liter ZnO; and from about 0.2 to about 2 grams per liter Na 2 Cr 2 O 7 .2H 2 O.
Claim 7
Dependent Claim
17 words
The solution of claim 5 wherein an effective amount of a surfactant is added to said solution.
Claim 8
Dependent Claim
11 words
The solution of claim 6 wherein said surfactant is lauryl sulfate.
Claim 9
Independent Claim
51 words
A method for depositing an anti-tarnish coating on a copper or copper base alloy foil strip, comprising the steps of: providing an electrolytic cell containing an anode and chromium and zinc ions; providing said foil strip as a cathode; and electrolytically depositing said chromium and zinc ions on said foil strip.
Claim 10
Independent Claim
51 words
A method for depositing an anti-tarnish coating on a copper or copper base alloy foil strip, comprising the steps of: providing an electrolytic cell containing an anode and chromium and zinc ions; providing said foil strip as a cathode; and electrolytically depositing said chromium and zinc ions on said foil strip.
Claim 11
Dependent Claim
148 words
The method of claim 8 wherein said steps include: providing said electrolYte with an aqueous basic solution containing hydroxide ions, from about 0.07 grams per liter to about 7 grams per liter zinc ions, and from about 0.1 grams per liter to about 100 grams per liter of a water soluble hexavalent chromium salt wherein the concentration of either said zinc ions or said chromium (VI) ions or both is less than 1.0; immersing said foil strip in said electrolyte; passing current through said strip and electrolyte such that a current density of from about 1 milliamp per square centimeter to about 1 amp per square centimeter is provided; electrolytically depositing a chromium-zinc coating on said foil for a time sufficient to deposit a coating having a thickness effective to prevent tarnishing; removing said strip from said electrolyte; rinsing said coated strip; and drying said rinsed coated strip.
Claim 12
Dependent Claim
53 words
The method of claim 9 wherein the composition of said electrolyte consists essentially of from about 10 to about 25 grams per liter NaOH, from about 0.2 to about 1.5 grams per liter ZnO, and from about 0.2 to about 2 grams per liter Na 2 Cr 2 O 7 .2H 2 O.
Claim 13
Dependent Claim
16 words
The method of claim 10 wherein said solution further includes an effective concentration of a surfactant.
Claim 14
Dependent Claim
11 words
The method of claim 10 wherein said surfactant is lauryl sulfate.
Claim 15
Dependent Claim
17 words
The method of claim 12 wherein the pH of said solution is from about 12 to 14.
Claim 16
Dependent Claim
23 words
The method of claim 13 wherein current density for said electrolytic deposition step is from about 5 to about 100 mA/cm 2 .
Claim 17
Dependent Claim
26 words
The method of claim 14 wherein the effective thickness of said electrolytically deposited anti-tarnish coating is from less than a hundred angstroms to about 0.1 micron.
Claim 18
Dependent Claim
17 words
The method of claim 15 said rinse step comprises immersion of said coated strip in deionized water.
Claim 19
Dependent Claim
16 words
The method of claim 16 wherein said deionized water includes an effective amount of a caustic.
Claim 20
Dependent Claim
24 words
The method of claim 17 wherein the concentration of said caustic is from about 50 parts per million to about 150 parts per million.
Claim 21
Dependent Claim
24 words
The method of claim 18 wherein said caustic is selected from the group consisting of sodium hydroxide, calcium hydroxide, potassium hydroxide and ammonium hydroxide.
Claim 22
Dependent Claim
11 words
The method of claim 19 wherein said caustic is calcium hydroxide.
Claim 23
Dependent Claim
17 words
The method of claim 20 wherein said rinse solution further contains about 1 milliliter per liter silane.
Claim 24
Dependent Claim
20 words
The solution of claim 7 wherein the concentration of lauryl sulfate is from about 10 ppm to about 50 ppm.
Claim 25
Dependent Claim
20 words
The method of claim 13 wherein the concentration of lauryl sulfate is from about 10 ppm to about 50 ppm.
Claim 26
Dependent Claim
23 words
The method of claim 15 wherein the thickness of the electrolytically deposited anti-tarnish coating is from about 10 angstroms to about 100 angstroms.
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