Conductive Polymer Solid Electrolyte Capacitor ESR Reduction

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Solution Overview

Problem

Conductive polymers used in solid electrolytic capacitors face challenges in achieving a balance between high electrical conductivity and heat resistance, leading to increased equivalent series resistance (ESR) and decreased reliability under hot conditions when modified with 3,4-alkylenedioxythiophene.

Innovation Solution

A conductive polymer is developed by polymerizing a mixed monomer of 2,3-dihydro-thieno[3,4-b][1,4]dioxine and 2-alkyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine at a specific molar ratio in the presence of an organic sulfonic acid, enhancing both electrical conductivity and heat resistance, and utilizing this polymer as a solid electrolyte to reduce ESR and improve capacitance and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If 3,4-alkylenedioxythiophene is used to increase electrical conductivity, then electrical conductivity is improved, but heat resistance is significantly decreased and ESR becomes high

Engineering Contradiction:

Improveelectrical conductivityVSAvoidheat resistance

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent uses a composite monomer system combining 3,4-ethylenedioxythiophene (providing high conductivity) with 2-alkyl-3,4-ethylenedioxythiophene (providing heat resistance). This composite approach allows the resulting polymer to simultaneously achieve high electrical conductivity and excellent heat resistance, resolving the contradiction between these two properties that plague single-component systems.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces alkyl-substituted monomer units at specific ratios (0.05:1 to 1:0.1 molar ratio) within the polymer chain. These localized alkyl-substituted segments provide heat resistance and structural stability, while the majority 3,4-ethylenedioxythiophene units maintain high electrical conductivity. This local quality differentiation allows simultaneous optimization of both conductivity and heat resistance.

Inventive Principle:

Principle #3Local quality

2Reliability

If 3,4-alkylenedioxythiophene is used to increase electrical conductivity, then electrical conductivity is improved, but ESR becomes high

Engineering Contradiction:

Improveelectrical conductivityVSAvoidESR

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The composite monomer system produces a polymer with balanced electronic properties. The alkyl-substituted units modulate the polymer's electronic structure and packing, reducing energy losses and improving charge transport efficiency. This results in simultaneously high electrical conductivity and low ESR, eliminating the harmful high-ESR side effect that occurs with pure alkyl-substituted polymers.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional conductive polymers are used, then manufacturing is simple, but reliability under hot conditions is decreased

Engineering Contradiction:

Improvepolymerization processVSAvoidreliability under hot condition

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent modifies the monomer composition parameters by introducing alkyl-substituted 3,4-ethylenedioxythiophene at controlled ratios. This parameter change in the monomer system translates to improved thermal stability and reliability under hot conditions while maintaining compatibility with conventional chemical oxidative polymerization processes using ferric salt and aromatic sulfonic acid, thus preserving ease of manufacture.

Inventive Principle:

Principle #35Parameter changes

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 electrical conductivity and excellent heat resistance, resulting in solid electrolytic capacitors with low ESR, large capacitance, and improved reliability under hot conditions.

Implementation Method 1

a mixed monomer of 2,3-dihydro-thieno [3,4-b] [1,4] dioxine and 2-alkyl-2,3-dihydro-thieno [3,4-b] [1,4] dioxine at a molar ratio of 0.05:1 to 1:0.1 is polymerized in the presence of an organic sulfonic acid

Methodology Applied

Scientific EffectChemical oxidative polymerization:

Implementation Method 2

the organic sulfonic acid is included as a dopant

Methodology Applied

Scientific EffectDoping: Dopants

Data Source

PatentEP2508547B1Conductive polymer and solid-electrolyte capacitor including same as solid electrolyte

Publication Date: 2015.04.08 TAYCA CORP

AI summary

There is provided a conductive polymer having a high electrical conductivity and an excellent heat resistance. Using it as a solid electrolyte, there is provided a solid electrolyte capacitor having a low ESR and a large capacitance with good reliability under a hot condition. A monomer mixture of 2,3-dihydro-thieno [3,4-b] [1,4] dioxine and 2-alkyl -2,3-dihydro-thieno [3,4-b] [1,4] dioxine at a mixture ratio of 0.05:1 1 to 1:0.1 by the molar ratio is polymerized in the presence of an organic sulfonic acid, and the organic sulfonic acid is included as a dopant. As the 2-alkyl -2,3-dihydro-thieno [3,4-b] [1,4] dioxine, the alkyl portion can be methyl, ethyl, propyl or butyl.