Porous Electrode Foil Structure for Crack-Resistant Capacitors

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Solution Overview

Problem

Electrode foils for electrolytic capacitors with porous portions and separation parts have low tensile strength and folding endurance, prone to breaking due to stress during production processes such as conveyance, winding, and bending, leading to cracks along the width direction.

Innovation Solution

The electrode foil features a metal foil with open pores and recessed portions in a dot pattern, where the pores are smaller than 2 μm and the recessed portions have an opening length of 2 μm or more, distributing stress and mitigating cracking through radial crack formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separation parts are provided to increase pushing depth in Erichsen test, then surface area increases and capacitance increases, but tensile strength decreases and folding endurance decreases, making the electrode foil prone to breakage

Engineering Contradiction:

ImprovecapacitanceVSAvoidtensile strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention applies local quality by creating recessed portions with specific geometric characteristics (opening length ≥2 μm, depth ≥5 μm, aspect ratio ≥2.5) at specific locations on the electrode foil surface. These localized structural modifications concentrate stress absorption capacity in specific regions without compromising the overall structural integrity of the foil, thereby improving capacitance while maintaining tensile strength.

Inventive Principle:

Principle #3Local quality

2Reliability

If separation parts extend in the width direction to increase surface area, then capacitance increases, but folding endurance decreases and the foil is likely to break during production processes

Engineering Contradiction:

ImprovecapacitanceVSAvoidfolding endurance

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The invention applies parameter changes by precisely controlling the geometric parameters of the recessed portions: opening length of at least 2 μm, depth of at least 5 μm, and aspect ratio of at least 2.5. By optimizing these parameters, the recessed portions effectively absorb bending stresses during folding operations while maintaining sufficient surface area for capacitance enhancement, thus improving folding endurance without sacrificing capacitive performance.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the electrode foil is conveyed by conveyance roller or wound by winding roller, then production process continues, but tension and bending stress generate cracks in the width direction along separation parts

Engineering Contradiction:

Improveproduction continuityVSAvoidstructural integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention applies beforehand cushioning by pre-forming recessed portions on the electrode foil surface before the foil undergoes conveyance or winding operations. These pre-existing recessed structures act as stress absorption zones that cushion the impact of tension and bending stresses generated during production processes, preventing the formation of cracks along separation parts and maintaining structural integrity throughout production.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS12525407B2Electrode foil for electrolytic capacitors, and electrolytic capacitor

Publication Date: 2026.01.13 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An electrode foil for an electrolytic capacitor includes a metal foil that includes a porous portion and a core portion continuous to the porous portion. The metal foil has a main surface in which pores in the porous portion are open. The porous portion includes a plurality of recessed portions that are open in the main surface and distributed in a dot pattern in an in-plane direction of the metal foil. The pores in the porous portion have an opening length smaller than 2 μm, and the recessed portions have an opening length of 2 μm or more.