Conductive Polymer Dispersion for Low ESR Solid Electrolytic Capacitors
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Solution Overview
Problem
Conductive polymers used in solid electrolytic capacitors face challenges with achieving high conductivity and heat resistance, leading to issues with equivalent series resistance (ESR) and reliability, especially under hot conditions, and are difficult to form directly on capacitor elements due to poor reproducibility and process control.
Innovation Solution
A conductive polymer dispersion liquid is developed by polymerizing thiophene or its derivatives using a copolymer from styrenesulfonic acid and non-sulfonic acid monomers like methacrylate or acrylate, or unsaturated hydrocarbon-containing alkoxysilane compounds, in the presence of water or an aqueous solution, to create a conductive polymer with improved conductivity and adhesion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ferric toluenesulfonate is used as oxidant and dopant agent, then the synthesis process is simple, but the initial resistance value and heat resistance are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the dopant agent from ferric toluenesulfonate to a specific copolymer containing sulfonic acid groups (such as styrene sulfonic acid copolymer). This parameter change in the dopant structure enables simultaneous achievement of low initial resistance and high heat resistance while maintaining synthesis simplicity.
Solution Approach 2:
The invention uses a composite dopant system comprising a copolymer with sulfonic acid groups combined with ferric salt. This composite approach leverages the advantages of both components: the copolymer provides excellent adhesion and electrical properties, while the ferric salt serves as an effective oxidant, achieving superior overall performance.
2Reliability
If ferric methoxybenzene sulfonate is used as oxidant dopant agent, then initial resistance value is lowered and heat resistance is improved, but the characteristics still cannot reach complete satisfaction
Solution Approach 1:
The patent optimizes the dopant agent parameters by selecting a copolymer with specific composition (containing sulfonic acid groups) and molecular weight range. This precise parameter optimization achieves complete satisfaction of both electrical properties and manufacturing ease, surpassing the partial satisfaction achieved by ferric methoxybenzene sulfonate.
3Manufacturing precision
If conductive polymer is formed directly on element, then the element can be coated with conductive polymer layer, but working conditions are very complicated and reproducibility is poor
Solution Approach 1:
The patent introduces a soluble copolymer containing sulfonic acid groups as an intermediary substance that facilitates the formation of conductive polymer layers. This intermediary dopant agent enables simple dip-coating or spin-coating processes to produce uniform, reproducible conductive layers without complicated working conditions, while maintaining excellent adhesion to the element surface.
4Reliability
If conventional conductive polymer is used, then high conductivity can be achieved, but adhesion properties are insufficient
Solution Approach 1:
The patent introduces local quality features by incorporating sulfonic acid groups and hydroxyl groups at specific locations in the copolymer structure. These functional groups are strategically positioned to provide strong chemical bonding sites for adhesion to the element surface, while the conjugated backbone structure maintains high electrical conductivity throughout the material.
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 resulting conductive polymer exhibits high conductivity and excellent heat resistance, enabling the production of solid electrolytic capacitors with low ESR and improved reliability under hot conditions, while also facilitating better adhesion and handling properties.
Implementation Method 1
thiophene or its derivatives is polymerized by oxidation polymerization in water, or in an aqueous solution
Data Source
AI summary
There is provided a conductive polymer having high conductivity with excellent heat resistance. Using the conductive polymer, there can be provided solid electrolytic capacitors having low ESR, high reliability, and less leakage current. There can be also provided conductive films having high conductivity and superior heat resistance. There is provided a conductive polymer dispersion liquid obtained by a method in which in the presence of a copolymer from styrenesulfonic acid, and at least one kind of a non-sulfonic acid monomer selected from the group consisting of methacrylate, acrylate, and an unsaturated hydrocarbon containing alkoxysilane compound or its hydrolysate, thiophene or its derivative is polymerized by oxidation polymerization in water, or in an aqueous solution comprising a mixture of water and a water miscible solvent to produce the conductive polymer dispersion liquid. Using the conductive polymer as solid electrolyte, a solid electrolyte capacitor can be provided. Also, using the conductive polymer, a conductive film can be provided.