Carbon Paste Shrinkage Stress Reduction in Solid Electrolytic Capacitors

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Solution Overview

Problem

Conventional solid electrolytic capacitor elements face issues with leakage current defects due to shrinkage stress from the drying of carbon layers, which affects the mechanical characteristics and contact resistance, leading to insufficient leakage current characteristics.

Innovation Solution

A carbon paste is developed with a phenoxy resin and a carbon filler, where the phenoxy ratio and carbon content ratio are optimized within specific ranges to reduce shrinkage stress, incorporating a thermosetting resin and a curing agent to form a carbon layer that minimizes stress on dielectric oxide films.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a carbon paste containing thermosetting resin is applied onto the solid electrolyte layer and subjected to drying, then the carbon layer is formed, but the shrinkage stress during drying breaks down the oxide films (dielectric layers), causing leakage current defects

Engineering Contradiction:

Improvecarbon layer formationVSAvoidleakage current characteristics

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the thermosetting resin by controlling the phenoxy resin content within 20-70 wt% and the carbon filler content ratio within 30-70 wt%. This parameter optimization reduces the shrinkage stress during drying while maintaining adequate adhesion, thereby preventing dielectric film breakdown and improving leakage current characteristics.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite material system consisting of carbon filler, phenoxy resin, and other thermosetting resins in specific proportions. This composite approach balances the conflicting requirements of adhesion (needing resin) and stress reduction (needing less resin or lower shrinkage), achieving both adequate bonding and reduced shrinkage stress to prevent oxide film breakdown.

Inventive Principle:

Principle #40Composite materials

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 optimized carbon paste reduces shrinkage stress during drying, resulting in solid electrolytic capacitors with improved leakage current characteristics and enhanced reliability by preventing dielectric film breakdown.

Implementation Method 1

The optimized carbon paste reduces shrinkage stress during drying, resulting in solid electrolytic capacitors with improved leakage current characteristics

Methodology Applied

Scientific EffectShrinkage stress reduction:

Implementation Method 2

incorporating a thermosetting resin and a curing agent to form a carbon layer that minimizes stress on dielectric oxide films

Methodology Applied

Scientific EffectThermosetting resin curing:

Data Source

PatentUS10923294B2Carbon paste and capacitor element for a solid electrolytic capacitor using carbon paste

Publication Date: 2021.02.16 MURATA MFG CO LTD

AI summary

A carbon paste that includes at least a carbon filler, and a thermosetting resin including a phenoxy resin. The phenoxy ratio X in the thermosetting resin is within a range of 20 Wt %≤X≤70 Wt %, and the carbon filler content ratio Y with respect to a total of the carbon filler and the thermosetting resin is within a range of 30 Wt %≤Y≤70 Wt %.