Very high volt oxide formation of aluminum for electrolytic capacitors
AssigneePacesetter, Inc.
InventorsThomas F. Strange, Timothy R. Marshall
Life of this patent
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Abstract
An anode foil treatment method produces a useful high quality oxide with inherently high capacitance at voltages as high as 750 Volts or more. The anode foil treatment method comprises a series of formation and relaxation steps. Oxide layer formation is performed in a forming mixture that includes a high molecular weight dicarboxylic acid that is made into a salt and a strong base. The concentration of the dicarboxylic acid is carefully monitored and kept within a narrow band. The complex by-product of the dicarboxylic salt created during formation process is kept below a fixed maximum level.
Claims34
A method for treating an anode foil, comprising the steps of:
- (a) forming an oxide layer on a first surface of said foil, wherein said foil is placed in a first forming composition at an applied voltage of about 800 Volts to about 1000 Volts;
- and
- (b) removing by-products formed during said forming step by adding a stock solution to said first forming composition and overflowing said first forming composition at a rate sufficient to compensate for by-product formation.
A method for treating an anode foil, comprising the steps of:
- (a) forming an oxide layer on a first surface of said foil, wherein said foil is placed in a first forming composition at an applied voltage of about 800 Volts to about 1000 Volts;
- (b) removing said foil from said first forming composition when a bleed current reaches a first preset bleed current value;
- (c) returning said foil to said first forming composition at a second applied voltage, wherein said second voltage is greater than said first voltage,
- (d) removing said foil from said first forming composition when a bleed current reaches a second preset bleed current value;
- and
- (e) removing by-products formed during said forming step and said returning step.
Dependencies are inferred from the claim text.