Anodized tantalum pellet for an electrolytic capacitor
AssigneeWilson Greatbatch Ltd.
InventorsDonald H. Stephenson, Martin D. Cymerman, Barry C. Muffoletto
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Abstract
An anodized pressed valve metal powder pellet is described. The anodized pellet is particularly useful as an anode in an electrolytic capacitor having an improved breakdown voltage. The anodized pellet is formed by periodically holding the pellet at a constant voltage and allowing the current to decay over a period of time, or by turning the formation power supply off altogether during the anodization process. Either way provides an opportunity for heated electrolyte to diffuse from the anodized pellet.
Claims23
A method for anodizing a pressed valve metal structure to a target formation voltage, comprising the steps of:
- a) providing the pressed valve metal structure in an anodizing electrolyte;
- b) performing a first anodizing step by subjecting the structure to a first current until the structure reaches a first formation voltage less than the target formation voltage;
- c) diffusing the electrolyte from the structure by turning off the current for at least about 20 minutes;
- and
- d) performing a final anodizing step by subjecting the structure to a last current until the structure reaches the target formation voltage.
A method for anodizing a pressed valve metal structure to a target formation voltage, comprising the steps of:
- a) providing the pressed valve metal structure in an anodizing electrolyte;
- b) performing a first anodizing step by subjecting the structure to a first current until the structure reaches a first formation voltage less than the target formation voltage;
- c) diffusing the electrolyte from the structure by turning off the current for at least about 20 minutes;
- d) performing at least one subsequent anodizing step by subjecting the structure to a subsequent current until the structure reaches a subsequent formation voltage greater than the first formation voltage but less than the target formation voltage;
- e) diffusing electrolyte from the structure after the subsequent formation voltage is attained;
- and
- f) performing a final anodizing step by subjecting the structure to a last current until the structure reaches the target formation voltage.
An anodized pressed valve metal structure characterized as having been anodized in an aqueous electrolyte comprising ethylene glycol or polyethylene glycol and phosphoric acid to a target formation voltage greater than about 330 volts in a first anodization step by the structure having been subjected to a first current until the structure reaches a first formation voltage less than the target formation voltage, followed by the electrolyte having been diffused from the structure by turning off the current for at least about 20 minutes, followed by the structure having been subjected to at least one subsequent current until the structure reaches the target formation voltage.
Dependencies are inferred from the claim text.