Sponge-Porous Anode Foil for Capacitor Gas Venting and Strength

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Solution Overview

Problem

Conventional anode foils for solid electrolytic capacitors face challenges in balancing the specific surface area and strength, as through-tunnel pits often connect adjacently, leading to decreased core metal strength and limited surface area expansion, hindering effective filling with conductive polymer.

Innovation Solution

The anode foil features a core metal with a sponge-like porous layer and through holes in a sponge shape, allowing for improved gas exchange and polymer impregnation while maintaining structural integrity, achieved through controlled electrolytic etching with alternating current and protective film management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If conventional electrolytic etching is used to form porous layer, then specific surface area is increased, but gas escape becomes difficult and deep portion filling is hindered

Engineering Contradiction:

Improvespecific surface areaVSAvoidgas escape ability

Core Design Contradiction:

Area of moving objectVSEase of operation

Solution Approach 1:

The patent segments the gas escape path by creating through-tunnel pits that penetrate the entire porous layer thickness, dividing the single escape route into multiple independent paths from deep portions to the surface, enabling efficient gas evacuation during conductive polymer filling

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent utilizes a porous layer with controlled pore structure formed by electrolytic etching, where the porous structure provides both high specific surface area for capacitance and interconnected channels for gas escape, resolving the contradiction between surface area expansion and gas venting capability

Inventive Principle:

Principle #31Porous materials

2Ease of operation

If through-tunnel pits are formed to improve gas escape, then gas venting is improved, but core metal strength decreases

Engineering Contradiction:

Improvegas escape abilityVSAvoidcore metal strength

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent applies local quality by forming through-tunnel pits only in specific regions of the porous layer rather than uniformly throughout, creating localized gas escape channels in areas where they are most needed while preserving the structural integrity and strength of the core metal in other regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses partial action by forming through-tunnel pits that extend only partially through the porous layer thickness or in selected areas, rather than creating complete through-holes across the entire structure, thus providing sufficient gas escape pathways while minimizing the impact on core metal strength

Inventive Principle:

Principle #16Partial or excessive action

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 design enhances the balance between specific surface area and strength, improving capacitance expression and impregnation properties of the solid electrolytic capacitor.

Implementation Method 1

etching a surface of a base material to form a porous layer in a sponge shape

Methodology Applied

Scientific EffectElectrolytic etching: Electrolysis

Implementation Method 2

etching a part in a plane of a core metal of the base material to form a through hole in a sponge shape penetrating the core metal

Methodology Applied

Scientific EffectAlternating current etching: Electrolysis

Data Source

PatentUS20260038744A1Anode foil for solid electrolytic capacitor, solid electrolytic capacitor, and method for manufacturing anode foil for solid electrolytic capacitor

Publication Date: 2026.02.05 MURATA MFG CO LTD

AI summary

An anode foil for a solid electrolytic capacitor that includes: a core metal; a porous layer in a sponge shape on the core metal; and one or more through holes in a sponge shape in a part in a plane of the core metal and penetrating the core metal. A method for forming the anode foil is also described.