Aluminum Anode Foil Hydration and Chemical Conversion
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Solution Overview
Problem
Existing methods for manufacturing anode foil for aluminum electrolytic capacitors fail to effectively reduce leakage current while maintaining high capacitance, as they either damage the hydrated film or result in defective oxide films due to crystallization and insufficient chemical conversion.
Innovation Solution
The method involves forming a hydrated film on aluminum foil by dipping it in hot pure water, attaching organic acid, and performing a multi-stage chemical conversion treatment with controlled voltage, followed by depolarization and follow-up chemical conversion treatments to minimize defects and enhance pit diameter utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If aluminum foil is dipped into weak acid solution to form hydrated film, then leakage current is suppressed, but the hydrated film structure is damaged and defects increase
Solution Approach 1:
The patent changes the pH parameter of the solution from weak acid (conventional) to strongly acidic (innovation). This parameter change allows the formation of a hydrated film without damaging its structure, as the strongly acidic condition prevents the dissolution issues that occur with weak acids while still enabling effective leakage current suppression.
Solution Approach 2:
The patent creates a composite structure by forming a hydrated film on aluminum foil that combines the benefits of structural integrity and leakage current suppression. The hydrated film acts as a protective layer that maintains the underlying aluminum foil structure while providing the necessary electrical insulation properties.
2Object-generated harmful factors
If multi-stage chemical conversion is performed with depolarization treatment, then leakage current decreases, but etched pits are embedded in chemical film reducing effective surface area
Solution Approach 1:
The patent extracts the depolarization treatment step from the conventional multi-stage chemical conversion process. By removing this intermediate treatment, the etched pits remain accessible and do not become embedded in the chemical film, thereby maintaining effective surface area while still achieving leakage current reduction through the final chemical conversion treatment.
Solution Approach 2:
The patent segments the chemical conversion process into distinct stages with specific pH conditions. The first stage uses strongly acidic conditions to form the hydrated film, followed by a second stage with different pH conditions to complete the chemical conversion. This segmentation allows each stage to optimize for its specific function without compromising the other.
3Object-generated harmful factors
If organic acid is attached to hydrated film before chemical conversion, then leakage current is suppressed, but capacitance increases due to effective pit utilization
Solution Approach 1:
The patent changes the pH parameter to strongly acidic conditions, which alters the chemical environment for organic acid attachment. This parameter change enables the organic acid to attach to the hydrated film in a way that suppresses leakage current while simultaneously allowing better utilization of etched pits, thereby increasing capacitance rather than decreasing it as previously expected.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in anode foils with reduced leakage current and increased capacitance, enabling the production of compact, high-reliability aluminum electrolytic capacitors.
Implementation Method 1
a first step of boiling aluminum foil in pure water
Implementation Method 2
a chemical conversion treatment on the aluminum foil in a boric-acid solution
Implementation Method 3
an oxide film is formed into a structure with no defect
Data Source
AI summary
The present invention provides a method of manufacturing anode foil for aluminum electrolytic capacitors with high capacitance and decreased leakage current. The method has the following steps: dipping etched aluminum foil into pure water having a temperature of 90° C. or higher so as to form a hydrated film on the foil; attaching organic acid to the surface of the hydrated film; performing main chemical conversion on the aluminum foil with application of formation voltage after the attaching step; performing depolarization on the aluminum foil after the main chemical conversion step; and performing follow-up chemical conversion on the aluminum foil after the main chemical conversion step. The main chemical conversion treatment has two-or-more stages. In the first stage of the treatment, the foil is dipped into a phosphate aqueous solution, and in the last stage, it is dipped into an aqueous solution different from the phosphate aqueous solution.