PEDOT Dispersion Particle Sizing for Low-Leakage Capacitor Outer Layers
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Solution Overview
Problem
Existing polymeric outer layers in solid electrolytic capacitors, particularly those based on PEDOT/PSS, often exhibit high leakage current due to insufficient mechanical stress resistance, which can be exacerbated during the encapsulation process.
Innovation Solution
A dispersion comprising a polythiophene, preferably in the form of a PEDOT/PSS complex, with specific particle size and surface roughness characteristics is used to create a conductive layer with improved mechanical buffer properties, reducing leakage current by forming a polymeric outer layer with controlled particle distribution and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PEDOT/PSS-based dispersions are used to form a polymeric outer layer, then the capacitor gains a conductive layer with good processing properties, but the leakage current becomes too high due to insufficient mechanical stress resistance
Solution Approach 1:
The patent changes the particle size parameter of the PEDOT/PSS dispersion from conventional small particles to particles with a size of 0.1 to 10 μm. This parameter change enhances the mechanical buffer properties of the polymeric outer layer, improving its ability to withstand mechanical stresses during encapsulation, thereby reducing leakage current while maintaining good processing properties
Solution Approach 2:
The patent creates a composite polymeric outer layer by combining PEDOT/PSS particles of specific size range (0.1 to 10 μm) with other components in the dispersion. This composite structure provides both the conductive properties needed for low ESR and the mechanical strength needed to prevent direct contact between the silver layer and dielectric under stress, thus reducing leakage current
2Strength
If the polymeric outer layer is made thicker to provide better mechanical buffering, then the mechanical stress resistance improves, but the leakage current increases due to improper particle distribution and surface roughness
Solution Approach 1:
The patent applies local quality by controlling the particle size distribution within the polymeric outer layer. By using particles of 0.1 to 10 μm, the dispersion creates regions with optimal mechanical buffering properties without compromising the overall electrical performance. This localized optimization ensures that mechanical stress is distributed effectively without creating pathways for increased leakage current
Solution Approach 2:
The patent uses a particle size range (0.1 to 10 μm) that is larger than conventional PEDOT/PSS particles but controlled to avoid excessive aggregation. This partial increase in particle size provides sufficient mechanical buffering while maintaining proper particle distribution and surface roughness, preventing the leakage current increase that would occur with thicker, improperly structured layers
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 dispersion and process result in a polymeric outer layer with reduced leakage current and enhanced mechanical stability, effectively addressing the high leakage current issues in capacitors by providing a robust conductive layer that minimizes contact between the anode and cathode under mechanical stress.
Implementation Method 1
A dispersion comprising particles of a polythiophene with a particle size of 0.1 to 10 μm, in particular 1.5 to 10 μm, is used for the formation of a polymeric outer layer
Data Source
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AI summary
The present invention relates to a dispersion comprising i) a dispersant; ii) at least one polythiophene dispersed in the dispersant i); wherein the dispersion comprises particles that have a particle size of 1.5 µm or more, the total number of these particles being in the range from 20,000 to 1,000,000 per ml; and wherein a conductive layer prepared from the dispersion has a surface roughness Rq in the range from 4 to 23 nm. The invention also relates to a process for the preparation of a dispersion, to a dispersion obtainable by that process, to a process for the preparation of a layered body, to a layered body obtainable by that process and to the use of a dispersion for the formation of a polymeric outer layer in a capacitor.