Conductive Polymer Formulation for Solid Electrolytic Capacitors
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Solution Overview
Problem
Solid electrolytic capacitors with conductive polymer cathodes suffer from poor equivalent series resistance (ESR) under high humidity and temperature conditions, and poor coverage of conducting polymers on anodized anode corners and edges leads to high DC leakage current, with ionic crosslinkers degrading humidity performance and causing corrosion.
Innovation Solution
A polyanion copolymer with a reduced sulfonic acid concentration and incorporating performance enhancement functional groups such as adhesion promoters, moisture retention, and hydrophobic/cross-linkable units is used to improve the conductive polymer dispersion, reducing moisture absorption and enhancing corner/edge coverage while maintaining high percent solids and film forming properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ionic crosslinkers are added to improve corner/edge coverage, then coating coverage is improved, but humidity performance degrades and corrosion increases
Solution Approach 1:
The patent changes the chemical composition parameters of the polyanion, specifically reducing sulfonic acid concentration and incorporating performance enhancement functional groups. This modifies the chemical properties to achieve both good coverage and humidity resistance without ionic crosslinkers
Solution Approach 2:
The patent extracts and removes the harmful ionic crosslinkers from the system while maintaining their beneficial coverage effects through the modified polyanion composition alone, eliminating the source of humidity degradation and corrosion
2Quantity of substance
If polyanion with high sulfonic acid concentration is used, then conductivity is improved, but moisture absorption increases
Solution Approach 1:
The patent optimizes the sulfonic acid concentration parameter by reducing it from high levels to lower concentrations, and compensates for conductivity through the incorporation of performance enhancement functional groups that provide alternative conduction pathways while reducing moisture affinity
Solution Approach 2:
The patent creates a composite polyanion structure combining reduced sulfonic acid groups with performance enhancement functional groups including adhesion promoters, moisture retention groups, and hydrophobic/cross-linkable groups, achieving a balanced material with both conductivity and moisture resistance
3Manufacturing precision
If higher percent solids in conductive polymer dispersion are used, then corner/edge coating coverage is improved, but viscosity increases
Solution Approach 1:
The patent modifies the dispersion composition parameters to enable higher percent solids content while controlling viscosity through the specific polyanion formulation with performance enhancement functional groups that maintain processability
Data Source
AI summary
An improved formulation of conductive polymer is provided. The formulation comprises a conductive polymer and a polyanion wherein the polyanion is a copolymer comprising groups A, B and C represented the ratio of Formula A:AxByCz Formula Awherein:A is polystyrenesulfonic acid or salt of polystyrenesulfonate;B and C separately represent polymerized units substituted by a group selected from:—C(O)OR6 wherein R6 is selected from the group consisting of:—(CHR17)b—R18. All other groups are defined. The conductive polymer has an average particle size of at least 1 nm to no more than 10 microns.