Electrolytic Capacitor Carbon Layer for Moisture Corrosion Resistance
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Solution Overview
Problem
Moisture entering electrolytic capacitors through the carbon layer causes corrosion of the metal foil, leading to leakage current failure, which existing technologies have not effectively prevented.
Innovation Solution
Incorporating a carbon layer with a scaly insulating inorganic filler oriented at acute angles between 0° to 45° with respect to the metal foil's longitudinal direction, creating a maze effect that prevents moisture from reaching the metal foil, thereby reducing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional carbon layer is used in the electrolytic capacitor, then the electrical conductivity is maintained, but moisture can penetrate through the carbon layer and cause corrosion of the metal foil
Solution Approach 1:
The patent applies composite materials by combining carbon particles with insulating inorganic filler particles in the carbon layer. This composite structure maintains electrical conductivity through the carbon network while the insulating inorganic filler creates a moisture barrier, preventing water penetration to the metal foil substrate.
Solution Approach 2:
The insulating inorganic filler acts as an intermediary barrier between the carbon layer and the metal foil. It mediates by blocking moisture transport paths while allowing the carbon network to maintain electrical conductivity, thus protecting the metal foil from corrosion without compromising electrical performance.
2Reliability
If the carbon layer is made more dense to prevent moisture entry, then corrosion resistance improves, but electrical conductivity may deteriorate
Solution Approach 1:
The composite structure of carbon particles and insulating inorganic filler allows the layer to be sufficiently dense for moisture protection while the conductive carbon network maintains electrical pathways. The insulating filler blocks water molecules without completely disrupting electron transport through the carbon matrix.
Solution Approach 2:
The carbon layer exhibits local quality differentiation where carbon particles provide conductivity in certain regions while insulating inorganic filler particles provide moisture barrier properties in other regions. This spatial distribution allows simultaneous achievement of electrical conductivity and moisture protection.
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
The maze effect significantly reduces moisture diffusion into the electrolytic capacitor, preventing corrosion of the metal foil and enhancing the long-term reliability of the capacitor while maintaining a low ESR.
Implementation Method 1
In a cut section of the electrolytic capacitor element in a direction perpendicular to a main face of the metal foil, an average of acute angles between a longitudinal direction of a cross-section of the insulating inorganic filler in the carbon layer adjacent to the main face of the metal foil and a longitudinal direction of a cross-section of the metal foil is 0° to 45°
Data Source
AI summary
An electrolytic capacitor element including: a valve-acting metal substrate including a core portion made of metal foil and a porous portion along a surface of the metal foil; a dielectric layer on the porous portion; a solid electrolyte layer on the dielectric layer; and a conductive layer on the solid electrolyte layer, the conductive layer including a carbon layer, the carbon layer containing a carbon filler and a scaly insulating inorganic filler, wherein, in a cut section of the electrolytic capacitor element in a direction perpendicular to a main face of the metal foil, an average of acute angles between a longitudinal direction of a cross-section of the insulating inorganic filler in the carbon layer adjacent to the main face of the metal foil and a longitudinal direction of a cross-section of the metal foil is 0° to 45°.