Carbon Layer Composition for ESR-Stable Solid Electrolytic Capacitors
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Solution Overview
Problem
Solid electrolytic capacitors experience a significant increase in equivalent series resistance (ESR) when exposed to high temperature environments, due to the deterioration of the solid electrolyte layer caused by oxygen and moisture intrusion.
Innovation Solution
A solid electrolytic capacitor element with a carbon layer that has a D/G ratio of 1.5 or less in its Raman spectrum, formed using a carbon paste containing carbon particles and a dispersion medium, which improves the surface state of carbon particles and reduces air permeability, thereby suppressing ESR increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional carbon layer is used to cover the solid electrolyte layer, then the capacitor structure is complete and cathode extraction is enabled, but the solid electrolyte layer deteriorates due to oxygen and moisture intrusion, causing ESR to increase greatly after high temperature exposure
Solution Approach 1:
The invention changes the physical and chemical parameters of the carbon layer by controlling the D/G ratio to 1.5 or less, indicating a more graphitic structure with fewer defects. This parameter change reduces the carbon layer's permeability to oxygen and moisture, thereby protecting the solid electrolyte layer from deterioration and maintaining low ESR after high temperature exposure
Solution Approach 2:
The invention uses a composite structure where a specifically engineered carbon layer (with controlled D/G ratio) is combined with the solid electrolyte layer. This composite material approach creates a protective barrier that prevents harmful substances from reaching the solid electrolyte, resolving the contradiction between structural completeness and protection against environmental degradation
2Reliability
If the carbon layer has high graphitic structure (low D/G ratio), then air permeability is reduced and ESR stability improves, but manufacturing precision requirements increase
Solution Approach 1:
The invention establishes a specific parameter threshold (D/G ratio ≤ 1.5) that balances manufacturing feasibility with performance requirements. This parameter specification provides a clear manufacturing target while ensuring sufficient protection against oxygen and moisture intrusion, resolving the contradiction between reliability and manufacturing precision
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 proposed solution effectively suppresses the increase in ESR even when the solid electrolytic capacitor is exposed to high temperature environments, maintaining low initial ESR and reducing variations in ESR under high temperature and humidity conditions.
Implementation Method 1
the carbon layer shows a D/G ratio of 1.5 or less... which improves the surface state of carbon particles and reduces air permeability
Data Source
AI summary
A solid electrolytic capacitor element includes an anode body; a dielectric layer formed on a surface of the anode body; a solid electrolyte layer that covers at least a portion of the dielectric layer; and a carbon layer that covers at least a portion of the solid electrolyte layer and contains carbon particles. The carbon layer shows a D/G ratio of 1.5 or less, the D/G ratio being a ratio of an intensity of a D band relative to an intensity of a G band in a Raman spectrum of the carbon layer.