Electrolytic Capacitor Leakage Current Reduction via Anode Terminal Oxide Film
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Solution Overview
Problem
Conventional rolled type electrolytic capacitors experience high leakage current due to damage and oxidation of the oxide film during the manufacturing process, which affects their impedance and reliability, especially at high frequencies.
Innovation Solution
The capacitor design incorporates a π-conjugated conductive polymer solid electrolyte layer with a second oxide film on the anode terminal having higher water repellency, formed through a re-anodizing process using an ammonium adipate-based solution, to reduce leakage current and protect the oxide film from damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxide film is formed on the anode foil surface and then rolled, then the capacitor structure is formed, but the oxide film is damaged during rolling causing high leakage current
Solution Approach 1:
A second oxide film is formed on the anode terminal surface after rolling but before final assembly. This preliminary protective action restores the oxide film that was damaged during the rolling process, thereby reducing leakage current and improving reliability without requiring changes to the rolling process itself.
2Reliability
If conventional anodizing is used to form oxide film, then the oxide film is formed, but it has poor water repellency leading to oxidation and leakage current
Solution Approach 1:
The anodizing process parameters are changed by using an ammonium adipate-based solution instead of conventional solutions. This chemical parameter change results in an oxide film with enhanced water repellency properties, preventing water penetration and subsequent oxidation, thereby reducing leakage current and improving reliability.
3Manufacturing precision
If the capacitor element is impregnated with conductive polymer particles, then solid electrolyte layer is formed uniformly, but the oxide film is still susceptible to damage from heat and oxidation
Solution Approach 1:
The second oxide film is formed on the anode terminal surface as a preliminary protective measure before the capacitor undergoes final assembly and testing. This preliminary protection ensures the oxide film is restored and protected against heat and oxidation that may occur during subsequent manufacturing steps, while the conductive polymer impregnation proceeds to form the solid electrolyte layer.
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 configuration significantly reduces leakage current and enhances the reliability and capacitance of the electrolytic capacitor, making it suitable for high-frequency applications with improved water repellency and reduced risk of short circuiting.
Implementation Method 1
An oxide film is provided on a surface of the anode foil has by anodizing
Implementation Method 2
The oxide film is formed on a cutting surface of the anode foil and the surface of the anode terminal
Implementation Method 3
a solid electrolyte layer formed using π-conjugated conductive polymer dispersing material on the first oxide film
Data Source
AI summary
A capacitor element includes an anode foil, the first oxide film on a surface of the anode foil, a solid electrolyte layer formed using π-conjugated conductive polymer dispersing material on the first oxide film, and a cathode foil on the solid electrolyte layer. The cathode foil faces the first oxide film across the solid electrolyte layer. An electrolytic capacitor includes the capacitor element, an anode terminal connected to the anode foil, and a second oxide film on a surface of the anode terminal. The second oxide film provided on the anode terminal has higher water repellency than the first oxide film provided on the anode foil. This electrolytic capacitor can reduce a leakage current.