Porous Electrode Foil Structure for High-Capacitance Capacitors
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Solution Overview
Problem
Current electrolytic capacitors require further performance improvement to enhance capacitance, reliability, and reduce ESR and leakage current.
Innovation Solution
The electrode foil for electrolytic capacitors features a porous portion with specific pit perimeter length ratios in three regions, integrated with a core portion, and a dielectric layer covering the metal framework, facilitating increased surface area, effective dielectric layer formation, and improved electrolyte impregnation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the porous portion is etched deeper to increase capacitance, then the surface area increases, but the mechanical strength and folding endurance deteriorate
Solution Approach 1:
The patent applies local quality by creating different pit perimeter length characteristics in different regions of the porous portion. The first region (outer surface side) has larger pit perimeter lengths to provide mechanical strength, while the second region (inner side) has smaller pit perimeter lengths to allow deeper etching and increase capacitance. This regional differentiation resolves the contradiction between capacitance and folding endurance.
2Quantity of substance
If the porous portion is etched deeper to increase capacitance, then the surface area increases, but the dielectric layer formation becomes difficult
Solution Approach 1:
The patent creates different pit perimeter length characteristics in different regions to optimize dielectric layer formation. The first region has larger pit perimeter lengths that facilitate dielectric layer formation near the outer surface, while the second region has smaller pit perimeter lengths that allow controlled etching depth for adequate dielectric coverage, resolving the contradiction between capacitance increase and dielectric layer formation difficulty.
3Loss of energy
If the pit size is increased to reduce ESR, then the electrolyte impregnation improves, but the leakage current increases
Solution Approach 1:
The patent applies local quality by creating different pit perimeter length characteristics in different regions. The first region has larger pit perimeter lengths that provide good electrolyte impregnation and low ESR, while the second region has smaller pit perimeter lengths that maintain adequate dielectric coverage and suppress leakage current, thus resolving the contradiction between ESR reduction and leakage current control.
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 results in a high-performance electrolytic capacitor with enhanced capacitance, reliability, reduced ESR, and suppressed leakage current, while improving folding endurance and tensile strength.
Implementation Method 1
the principal surface of the metal foil is etched into a porous portion
Implementation Method 2
The metal foil is then subjected to a chemical conversion treatment, to form a metal oxide (dielectric) layer on the surface of a metal framework constituting the porous portion
Implementation Method 3
improved electrolyte impregnation
Data Source
AI summary
An electrode foil for an electrolytic capacitor includes a porous portion, and a core portion continuous with the porous portion. When the porous portion is equally divided in three in the thickness direction of the porous portion into a first region, a second region, and a third region sequentially from the outer surface side of the porous portion, 1.1≤L2/L1, and 1.1≤L2/L3 are satisfied, where the L1 represents a pit perimeter length in the first region, the L2 represents a pit perimeter length in the second region, and the L3 represents a pit perimeter length in the third region.