Solid Electrolytic Capacitor Structure for High Voltage and Capacitance
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Solution Overview
Problem
Solid electrolytic capacitors face challenges in achieving both high withstand voltage and large capacity, which are essential for meeting the increasing power demands in fields like power electronics.
Innovation Solution
The solid electrolytic capacitor design includes an anode foil with tunnel-shaped etching pits, a dielectric oxide film, and a pseudo boehmite layer, along with a conductive polymer layer between the anode foil and the cathode body. The pseudo boehmite layer is optimized to have an amount of 0.4 mg/cm² to 1.8 mg/cm², and the conductive polymer layer is formed with a specific weight range to enhance both capacitance and withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the dielectric oxide film is thickened to increase withstand voltage, then the withstand voltage increases, but the capacitance decreases
Solution Approach 1:
The invention introduces a pseudo boehmite layer with specific physical and chemical properties (porosity, surface area, adhesion) that differs from the dielectric oxide film. This layer is positioned locally between the anode foil and dielectric oxide film to provide defect repair and adhesion functions, allowing the dielectric oxide film to be thinner while maintaining both withstand voltage and capacitance.
Solution Approach 2:
The pseudo boehmite layer acts as an intermediary between the anode foil and the dielectric oxide film. It provides defect repair functionality that allows the dielectric oxide film to be thinner, and simultaneously provides adhesion to prevent peeling. This intermediary layer resolves the contradiction by enabling thin dielectric films to achieve both high withstand voltage and high capacitance.
2Quantity of substance
If the surface area of the anode foil is enlarged to increase capacitance, then the capacitance increases, but the adhesion of the dielectric oxide film deteriorates
Solution Approach 1:
The pseudo boehmite layer is introduced with specific local properties (high porosity, large surface area, strong adhesion to anode foil) to address the adhesion problem in specific regions where the dielectric oxide film peels due to thermal expansion differences. This allows the anode foil surface area to be greatly enlarged while maintaining adhesion through the pseudo boehmite layer's anchoring effect.
Solution Approach 2:
The pseudo boehmite layer is designed with high porosity (50-80% volume ratio) and large specific surface area. This porous structure provides mechanical interlocking with the anode foil and dielectric oxide film, significantly improving adhesion. The porous structure also allows for defect repair and accommodates thermal expansion differences, enabling the use of highly enlarged anode foil surfaces for high capacitance.
3Reliability
If a solid electrolyte is used instead of electrolytic solution to prevent evaporation, then the reliability improves, but the defect repairing effect deteriorates
Solution Approach 1:
The pseudo boehmite layer is formed in advance during the anodization process, before the dielectric oxide film is fully formed. This preliminary action creates a defect-repairing structure that is already in place to compensate for defects in the dielectric oxide film, providing continuous defect repair capability throughout the capacitor's lifetime without requiring liquid electrolyte.
Solution Approach 2:
The pseudo boehmite layer provides self-service defect repair functionality. Its specific physical and chemical properties (porosity, surface area, composition) enable it to automatically compensate for defects in the dielectric oxide film through its structure, maintaining the capacitor's reliability and performance over time without external intervention or liquid electrolyte.
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 design effectively achieves a solid electrolytic capacitor with high withstand voltage and large capacitance, addressing the limitations of traditional capacitors and meeting the demands of high-power applications.
Implementation Method 1
A surface of the anode foil is enlarged by making the valve action metal into a sintered body or a shape such as etching foil, and the enlarged surface has a dielectric oxide film thereon by treatment such as anode oxidation.
Implementation Method 2
conductive polymers derived from monomers with n-conjugated double bonds, such as poly(3,4-ethylenedioxythiophene) (PEDOT)
Data Source
AI summary
A solid electrolytic capacitor that exhibits both high withstand voltage and large capacity and a manufacturing method of the solid electrolytic capacitor are provided. The solid electrolytic capacitor includes anode foil, cathode foil facing the anode foil, and conductive polymers intervening between the anode foil and the cathode foil. The anode foil has tunnel-shaped etching pits formed on a surface layer of the anode foil, a dielectric oxide film layer formed on the surface layer of the anode foil, and a pseudo boehmite layer on the dielectric oxide film layer and formed on the surface layer of the anode foil. An amount of the pseudo boehmite layer is adjusted to be 0.4 mg·cm−2 to 1.8 mg·cm−2.