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US4131520A
Expired / Lapsed
US
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Two-stage anodization of capacitor electrodes
Assignee: Vishay Sprague Inc
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Filing: 1977-11-10
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Granted: 1978-12-26
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Expires: 1997-11-10
Abstract
Abstract In a two-stage anodization process in which the outer portion of a porous valve-metal sintered body is anodized to a higher voltage than the inner portion, the second-stage anodization is carried out in an electrolyte containing a salt of a weak acid.
Inventors
- 👤 Walter J. Bernard
- 👤 Stanley P. Szpak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 08:45
CPC Classifications
H; H01; H01G; H01G9/00; H01G9/0029; H01G9/0032; C; C25; C25D; C25D11/00; C25D11/02; C25D11/26
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
106 words
A process for forming an electrolytic capacitor electrode from a sintered valve-metal pellet including the steps of anodizing the pellet in a conventional formation electrolyte in a first-stage to a predetermined voltage and thereafter forming a thicker oxide layer on the outer surface of said pellet than in the center of said pellet by anodization in a second-stage at a higher voltage, said second-stage anodization being in an electrolyte different from that in the first-stage and containing a salt of a water-soluble weak acid having a dissociation constant of less than 1.0 × 10 -4 and then rinsing the pellet free of second-stage electrolyte with water.
Claim 2
Dependent Claim
106 words
A process for forming an electrolytic capacitor electrode from a sintered valve-metal pellet including the steps of anodizing the pellet in a conventional formation electrolyte in a first-stage to a predetermined voltage and thereafter forming a thicker oxide layer on the outer surface of said pellet than in the center of said pellet by anodization in a second-stage at a higher voltage, said second-stage anodization being in an electrolyte different from that in the first-stage and containing a salt of a water-soluble weak acid having a dissociation constant of less than 1.0 × 10 -4 and then rinsing the pellet free of second-stage electrolyte with water.
Claim 3
Dependent Claim
58 words
A process according to claim 1 wherein said pellet from the first-stage is impregnated with a material selected from the group consisting of (1) a poorly conducting solvent in which the solute of the second-stage electrolyte is soluble and (2) the weak acid which arises from the salt in said second-stage before subjecting said pellet to second-stage anodization.
Claim 4
Dependent Claim
29 words
A process according to claim 2 wherein said poorly conducting solvent or acid is miscible with water when the second-stage electrolyte is in the form of an aqueous solution.
Claim 5
Dependent Claim
23 words
A process according to claim 3 wherein said solvent is selected from the group consisting of distilled water, ethylene glycol, and mixtures thereof.
Claim 6
Dependent Claim
26 words
A process according to claim 2 wherein said poorly conducting solvent or said weak acid and said second-stage electrolyte are in the form of non-aqueous solutions.
Claim 7
Dependent Claim
27 words
A process according to claim 1 wherein said conventional formation electrolyte is selected from the group consisting of phosphoric acid, sulfuric acid, hydrochloric acid, and salts thereof.
Claim 8
Dependent Claim
34 words
A process according to claim 1 wherein 1-5 wt % of a weak acid corresponding to the salt solute in the second-stage electrolyte as an acid anion reservoir is present in said second-stage electrolyte.
Claim 9
Dependent Claim
21 words
A process according to claim 7 wherein said weak acid is boric acid and said salt is ammonium pentaborate or borax.
Claim 10
Dependent Claim
20 words
A process according to claim 1 wherein said second-stage electrolyte is an aqueous solution of 0.01-4.0 wt % ammonium pentaborate.
Claim 11
Dependent Claim
19 words
A process according to claim 1 wherein said second-stage electrolyte is an aqueous solution of 0.01-4.0 wt % borax.
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) | 1981-12-25 | 1982-06-26 | 1982-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-12-25 | 1986-06-26 | 1986-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-12-25 | 1990-06-26 | 1990-12-26 | $7700.00 | Window Closed / Lapsed |