Conductive Polymer Impregnation in Solid Electrolytic Capacitors
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Solution Overview
Problem
The miniaturization and weight reduction of solid electrolytic capacitors lead to fine, complex pore structures in porous film formation metals, making it difficult to impregnate conductive polymers effectively, and existing compositions struggle with moisture resistance and Equivalent Series Resistance (ESR) stability, especially under humid conditions.
Innovation Solution
A conductive composition with a conductive polymer having a specific particle diameter and a water-soluble compound with multiple hydroxyl groups is used, ensuring sufficient impregnation into fine concave-convex pores and enhancing moisture resistance by controlling the pH and acetal group content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the porous film formation metals are miniaturized and weight reduced, then the capacitor size and weight decrease, but the pore structures become fine and complex making it difficult to impregnate conductive polymers
Solution Approach 1:
The patent changes the particle diameter parameter of the conductive polymer to less than 26 nm (volume average), which enables effective impregnation into the fine and complex pore structures of miniaturized capacitors. This parameter optimization resolves the contradiction by maintaining small capacitor size while ensuring adequate polymer penetration.
Solution Approach 2:
The patent utilizes the porous structure of the film formation metal anode body with dielectric oxidation film to enable conductive polymer impregnation. The controlled porosity allows the fine conductive polymer particles to penetrate and form a solid electrolytic layer throughout the pore structure, addressing the impregnation difficulty in miniaturized devices.
2Ease of manufacture
If conventional conductive compositions are used, then the manufacturing process is simple, but moisture resistance and ESR stability under humid conditions deteriorate
Solution Approach 1:
The patent optimizes the particle diameter parameter of the conductive polymer to less than 26 nm, which simultaneously improves moisture resistance and ESR stability while maintaining manufacturing simplicity. The fine particle size enables better impregnation and forms a more reliable solid electrolytic layer that resists moisture penetration.
Solution Approach 2:
The patent creates a composite solid electrolytic layer by impregnating conductive polymer particles into the porous dielectric oxidation film structure. This composite material combines the dielectric properties of the oxidation film with the conductive properties of the polymer, achieving both moisture resistance and good ESR characteristics while keeping the manufacturing process simple.
3Ease of manufacture
If chemical oxidative polymerization or electrolytic polymerization is performed on the dielectric oxidation film, then the solid electrolytic layer can be formed, but impurities may be mixed in causing short circuits and the manufacturing process becomes complicated
Solution Approach 1:
The patent prepares conductive polymer particles in advance with a controlled particle diameter of less than 26 nm before impregnation. This preliminary preparation eliminates the need for in-situ polymerization processes, avoiding the introduction of impurities and simplifying the manufacturing process while ensuring reliable short circuit-free operation.
Solution Approach 2:
The patent extracts the polymerization step from the manufacturing process by using pre-synthesized conductive polymer particles. This removes the complex chemical reactions and potential impurity generation associated with oxidative or electrolytic polymerization, simplifying the process and improving reliability.
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 approach allows for the effective impregnation of conductive polymers into the complex pore structures of solid electrolytic capacitors, resulting in capacitors with improved moisture resistance and reliability, including stable ESR performance under humid conditions.
Implementation Method 1
The dielectric oxidation film is formed on the surface of an anode body of porous metal, and thus, has a fine concave-convex shape. For this reason, for the method for applying the dispersion including a conductive polymer on a dielectric oxidation film, it is difficult to impregnate the dispersion including a conductive polymer to the inside of the dielectric oxidation film.
Implementation Method 2
A conductive composition with a conductive polymer having a specific particle diameter and a water-soluble compound with multiple hydroxyl groups is used, ensuring sufficient impregnation into fine concave-convex pores and enhancing moisture resistance by controlling the pH and acetal group content.
Data Source
AI summary
Provided are: a conductive composition containing a conductive polymer (A) satisfying the below-mentioned condition (i) and a compound (B) having at least 3 hydroxyl groups, and having a pH at 25° C. of a 1 mol/L aqueous solution of no greater than 9.0; a conductive composition that further contains a water-soluble polymer (C) having a hydroxyl group; and a solid electrolytic capacitor having a solid electrolytic layer containing the composition. Condition (i): the volume-average particle size of the smallest particle distribution containing the smallest peak exhibited by the particle size among at least one peak obtained by measuring the particle distribution by means of a dynamic light scattering method using a conductive polymer solution containing 1% by mass of the conductive polymer being less than 26 nm.