Electrolytic Capacitor External Polymer Coating
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Solution Overview
Problem
Conventional wound solid electrolytic capacitors face challenges in uniformly controlling chemical reactions, leading to increased production costs, low withstand voltage, and reliability issues due to impurities and defective oxide films, which complicates the formation of conductive polymers and affects capacitance and ESR characteristics.
Innovation Solution
A method involving the formation of a capacitor element by winding an anode foil with a dielectric oxide film and a surface-treated cathode foil, immersed in a fluid dispersion of conductive polymer fine particles, followed by drying and impregnation with an electrolytic solution, which adheres to the separator and foils without forming conductive polymers inside, allowing for efficient recovery of defective oxide film portions and reducing ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If in-situ chemical polymerization is used to form conductive polymer inside capacitor element, then capacitance can be increased, but manufacturing complexity and production cost increase due to multiple reactions and cleaning processes
Solution Approach 1:
The patent extracts the conductive polymer formation process from the capacitor element interior. Instead of performing in-situ polymerization inside the wound structure, the patent applies conductive polymer coating to the external surfaces of the capacitor element, eliminating the need for multiple impregnation reactions and cleaning steps while still achieving the desired capacitance enhancement.
Solution Approach 2:
The patent introduces an intermediary coating layer of conductive polymer on the external surface of the capacitor element. This coating serves as a mediator that provides the electrical conductivity and capacitance benefits without requiring the complex in-situ polymerization process inside the element, thereby simplifying manufacturing.
2Quantity of substance
If in-situ chemical polymerization is performed to form conductive polymer, then capacitance increases, but production cost increases due to multiple cleaning processes
Solution Approach 1:
The patent removes the conductive polymer formation process from the interior of the capacitor element and relocates it to an external coating operation. This extraction eliminates the need for repeated cleaning processes that would be required to remove unreacted monomers and by-products from inside the wound structure, significantly reducing production costs.
Solution Approach 2:
The patent employs a simple external coating method that uses inexpensive conductive polymer materials applied in a single step. This approach replaces the expensive multi-step in-situ polymerization process with a more economical coating operation that does not require extensive cleaning infrastructure.
3Reliability
If thick oxide film is formed to improve withstand voltage, then reliability increases, but capacitance decreases due to reduced capacitance per unit volume
Solution Approach 1:
The patent creates a composite structure combining the dielectric oxide film with an external conductive polymer coating. This composite configuration allows the oxide film to provide high withstand voltage while the external coating adds capacitance without increasing the volume of the dielectric layer, thereby maintaining high capacitance per unit volume.
Solution Approach 2:
The patent adds capacitance in a different dimension - by applying conductive polymer coating on the external surface rather than increasing the thickness of the internal oxide film. This dimensional approach allows simultaneous achievement of high withstand voltage (from thick oxide) and high capacitance (from external coating) without the traditional trade-off.
4Ease of manufacture
If strong acids like sodium persulfate and p-ferric toluenesulfonate are used for polymerization, then conductive polymer can be formed, but reliability decreases due to impurity accumulation and corrosion
Solution Approach 1:
The patent extracts the harmful polymerization chemicals from the capacitor element interior by performing coating externally. This eliminates the need to use strong acids like sodium persulfate and p-ferric toluenesulfonate inside the sealed structure, preventing impurity accumulation and corrosion while still achieving conductive polymer formation.
Solution Approach 2:
The patent converts the harmful effect of strong acids by performing the polymerization reaction outside the capacitor element. The harmful chemicals are used in the coating process but do not remain inside the sealed capacitor, thereby converting a potentially harmful process into a beneficial one that produces conductive polymer without compromising reliability.
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 electrolytic capacitors with higher capacitance, improved withstand voltage, and enhanced reliability by avoiding the formation of conductive polymers inside the capacitor element, reducing ESR, and simplifying the manufacturing process while maintaining low production costs.
Implementation Method 1
conductive polymer fine particles adhering to surfaces of fibers of the separator (3) and filling between the fibers
Implementation Method 2
impregnating the capacitor element with an electrolytic solution
Data Source
AI summary
An capacitor element is fabricated by winding an anode foil having a dielectric oxide film formed thereon, and a cathode foil subjected to a treatment of enlarging surface area in a manner that a separator is interposed therebetween. The capacitor element is immersed in a fluid dispersion containing conductive polymer fine particles dispersed therein. Thereafter, it is depressurized and dried so that the conductive polymer fine particles adhere to surfaces of fibers of the separator, fill between the fibers of the separator, and adhere to surfaces of the anode foil and the cathode foil in a manner that the adhesion and filling of the conductive polymer fine particles are such that an amount of the fine particles decreases from ends toward a center of the capacitor element. Then, it is impregnated with an electrolytic solution.