US4525249A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Two step electro chemical and chemical etch process for high volt aluminum anode foil
Assignee: Philips North America LLC
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Filing: 1984-07-16
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Granted: 1985-06-25
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Expires: 2004-07-16
Abstract
Abstract Aluminum electrolytic capacitor anode foil of a high cubic texture etched in a two step process by treating the foil in an electrolyte bath containing 3% hydrochloric acid and 1% aluminum as aluminum chloride under the influence of a direct current and at a temperature of 75° C., and in a second step treating said etched foil in an aqueous bath of 8% nitric acid and 2.6% aluminum as a nitrate at a temperature of 85° C. for 5 to 7 minutes. The foil thus etched has a significantly higher capacitance resulting from a greater density of tunnels, an elongation of the tunnels, and a fairly linear tunnel structure.
Inventors
- 👤 Mulk R. Arora
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 04:19
CPC Classifications
H; H01; H01G; H01G9/00; H01G9/004; H01G9/04; H01G9/048; H01G9/055; C; C25; C25F; C25F3/00; C25F3/02; C25F3/04
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
150 words
A two step process for etching aluminum electrolytic capacitor anode foil wherein such foil has a high cubic texture, greater than 70% cubicity, comprising a first step of: treating said foil in an electrolyte bath containing between 1.5% and 7% hydrochloric acid and 0% to 2% aluminum as a chloride under the influence of direct current at a temperature between 70° C. and 85° C.; and passing a charge of 6 to 25 coulombs through said foil while said foil is immersed in said hydrochloric acid bath and having a current density between 0.25 and 0.6 amperes/cm 2 ; and in a second step, treating said foil emerging from said first bath in an aqueous bath consisting of from 2 to 11% nitric acid and between 0% to 3.5% aluminum as aluminum nitrate for a period of 3 to 12 minutes at a bath temperature of 80° to 95° C.
Claim 2
Dependent Claim
150 words
A two step process for etching aluminum electrolytic capacitor anode foil wherein such foil has a high cubic texture, greater than 70% cubicity, comprising a first step of: treating said foil in an electrolyte bath containing between 1.5% and 7% hydrochloric acid and 0% to 2% aluminum as a chloride under the influence of direct current at a temperature between 70° C. and 85° C.; and passing a charge of 6 to 25 coulombs through said foil while said foil is immersed in said hydrochloric acid bath and having a current density between 0.25 and 0.6 amperes/cm 2 ; and in a second step, treating said foil emerging from said first bath in an aqueous bath consisting of from 2 to 11% nitric acid and between 0% to 3.5% aluminum as aluminum nitrate for a period of 3 to 12 minutes at a bath temperature of 80° to 95° C.
Claim 3
Dependent Claim
17 words
A process according to claim 1 wherein said aluminum foil has a cubicity of 70% or greater.
Claim 4
Dependent Claim
22 words
A process according to claim 1 wherein the percentage of hydrochloric acid in the electrolytic bath of said first step is 3%.
Claim 5
Dependent Claim
24 words
A process according to claim 1 wherein the percentage of aluminum as a chloride in said electrolytic bath in said first step is 1.%.
Claim 6
Dependent Claim
16 words
A process according to claim 1 wherein the temperature in said first step is 75° C.
Claim 7
Dependent Claim
19 words
A process according to claim 1 wherein the current density in said first step is 0.40 amperes/cm 2 .
Claim 8
Dependent Claim
15 words
A process according to claim 1 wherein the etch coulombs are 9 coulombs/cm 2 .
Claim 9
Dependent Claim
16 words
The process of claim 1 wherein in said second step said bath comprises 8% nitric acid.
Claim 10
Dependent Claim
18 words
The process of claim 1 wherein in said second step said bath contains 2.6% aluminum as aluminum nitrate.
Claim 11
Dependent Claim
15 words
The process of claim 1 wherein the temperature of said second bath is 85° C.
Claim 12
Dependent Claim
20 words
The process of claim 1 wherein said foil is treated in said bath in said second step for 6 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-06-24 | 1988-12-24 | 1989-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-06-24 | 1992-12-24 | 1993-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-06-24 | 1996-12-24 | 1997-06-25 | $7700.00 | Window Closed / Lapsed |