Porous Anode Surface Zoning for Low-Leakage Electrolytic Capacitors
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Solution Overview
Problem
The reliability of electrolytic capacitors with solid electrolytes is compromised due to increased leakage current, which is attributed to defects in the dielectric layer formed on porous anode substrates, particularly at corner portions where mechanical strength is low and thermal stress concentrates.
Innovation Solution
The anode substrate is designed with distinct regions: a less compact first region away from corner portions to allow gas discharge and reduce carbon residue, and a more compact second region to minimize defects and enhance mechanical strength, thereby reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode substrate surface is made highly compact to reduce defects, then the mechanical strength and reliability improve, but gas discharge becomes difficult leading to increased carbon residue and leakage current
Solution Approach 1:
The anode substrate surface is divided into different regions with different compactness: a first region with high compactness for mechanical strength and a second region with lower compactness for gas discharge. This local differentiation allows the structure to simultaneously achieve both defect reduction and effective gas discharge, preventing carbon residue accumulation and reducing leakage current.
2Manufacturing precision
If the anode substrate surface is made highly compact to minimize defects, then the dielectric layer quality improves, but thermal stress concentration increases at corner portions
Solution Approach 1:
Different regions of the anode substrate surface are given different compactness levels: the central region has high compactness to minimize defects, while corner portions have reduced compactness to lower thermal stress concentration and prevent dielectric layer damage, thereby maintaining mechanical strength where most needed.
3Manufacturing precision
If the anode substrate is uniformly compacted, then defects are minimized, but carbon residue accumulates due to insufficient gas discharge pathways
Solution Approach 1:
The anode substrate surface is designed with a second region having lower compactness that serves as a gas discharge pathway. This localized less-compact region allows gases to escape during sintering, preventing carbon residue accumulation, while the rest of the substrate maintains high compactness to minimize defects.
Data Source
AI summary
An electrolytic capacitor including a capacitor element that includes an anode body being porous and including an anode substrate body and a dielectric layer formed on a surface of the anode substrate body, and a solid electrolyte layer covering at least part of the dielectric layer. The anode body has a plurality of principal faces. A surface of the anode body has a first region and a second region different from the first region, and the first region does not include a corner portion where a plurality of the principal faces meet. A surface roughness in the first region is greater than a surface roughness in the second region.