Solid Electrolytic Capacitor Conductive Polymer Layer Heat Resistance

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Solution Overview

Problem

The high temperature reflow process using lead-free solder in the manufacturing of solid electrolytic capacitors can degrade the conductive polymer layer, leading to decreased conductivity and performance, particularly in high-frequency applications.

Innovation Solution

A solid electrolytic capacitor with a conductive polymer layer containing an aromatic sulfonic acid ion and a nitrogen-containing heterocyclic polyaromatic compound ion, such as benzopyrimidine or quinoxaline, is developed, which enhances heat resistance and stability during the reflow process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If lead-free solder is used in the reflow process, then the harmful effect of lead is reduced, but the melting point increases to 200°C to 270°C causing deterioration of the conductive polymer layer

Engineering Contradiction:

Improveharmful effect of leadVSAvoidconductivity of conductive polymer layer

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the conductive polymer layer by incorporating nitrogen-containing heterocyclic polyaromatic compounds (such as polyethylene dioxythiophene) alongside conventional polymers. This compositional modification raises the thermal stability parameter of the layer, enabling it to withstand the 200-270°C reflow temperatures without significant conductivity loss.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite conductive polymer layer by combining multiple polymer materials with different thermal properties. The composite structure includes nitrogen-containing heterocyclic polyaromatic compounds that provide high-temperature stability, while maintaining the conductive properties needed for capacitor performance. This composite approach allows the layer to resist both lead contamination and high-temperature degradation.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional conductive polymer layers are used, then the manufacturing process is simple, but the heat resistance deteriorates at high temperatures above 200°C

Engineering Contradiction:

Improvesimplicity of manufacturing processVSAvoidheat resistance

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent modifies the thermal parameter of the conductive polymer layer by selecting polymers with inherently higher thermal stability. The nitrogen-containing heterocyclic polyaromatic compounds used in the layer exhibit stable chemical structures that resist thermal degradation up to 270°C, thus improving heat resistance without fundamentally changing the manufacturing process flow.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If polyethylene dioxythiophene is used in the conductive polymer layer, then adhesiveness with the dielectric film is improved, but the reaction rate is slow requiring extended processing time

Engineering Contradiction:

Improveadhesiveness with dielectric filmVSAvoidpolymerization reaction rate

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent merges polyethylene dioxythiophene with other conductive polymers in a composite layer structure. This combination allows the benefits of slow, stable polymerization and excellent adhesiveness to be retained while the overall layer composition provides sufficient conductivity and forms adequately within practical manufacturing timeframes. The composite approach balances reaction kinetics with final performance requirements.

Inventive Principle:

Principle #5Merging (Combining)

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 use of these compounds in the conductive polymer layer results in a capacitor with improved heat resistance and reduced equivalent series resistance (ESR), maintaining performance even under high-temperature conditions.

Implementation Method 1

a conductive polymer layer which includes an aromatic sulfonic acid ion and a nitrogen-containing heterocyclic polyaromatic compound ion containing a nitrogen atom as a heteroatom

Methodology Applied

Scientific EffectThermal stability of nitrogen-containing heterocyclic polyaromatic compounds:

Implementation Method 2

The conductive polymer layer includes an aromatic sulfonic acid ion and a nitrogen-containing heterocyclic polyaromatic compound ion

Methodology Applied

Scientific EffectHeat resistance enhancement through dopant incorporation:

Implementation Method 3

forming a conductive polymer layer on the dielectric film by polymerization reaction of a monomer using the monomer, a dopant material and an NHPA compound

Methodology Applied

Scientific EffectPolymerization reaction:

Data Source

PatentUS8363385B2Solid electrolytic capacitor and method of manufacturing thereof

Publication Date: 2013.01.29 SANYO ELECTRIC CO LTD

AI summary

A solid electrolytic capacitor having a high heat resistance is provided. The solid electrolytic capacitor according to the present invention includes an anode body having a surface on which a dielectric film is formed, and a conductive polymer layer formed on the dielectric film. The conductive polymer layer includes an aromatic sulfonic acid ion and an NHPA compound ion.