Electrolytic Capacitor Anode Foil Coating for Low Leak Current

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Solution Overview

Problem

In the production of electrolytic capacitors, the cutting surfaces of anode foils often lack a metal oxide layer, leading to increased leak current and reduced withstand voltage due to exposed metal layers and defective oxide films formed post-assembly.

Innovation Solution

The electrode foil features a porous body portion with a dielectric layer having varying film thickness, where the end surface vicinity region has a thicker coating layer than the deep inner region, achieved through atomic layer deposition, ensuring a dense and defect-free dielectric layer coverage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a metal oxide layer is formed on the anode foil surface through anodization treatment, then the electrostatic capacity increases, but the cutting surfaces lack proper dielectric coverage leading to increased leak current

Engineering Contradiction:

Improveelectrostatic capacityVSAvoidleak current

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies different dielectric layer configurations to different regions of the anode foil. The end surface vicinity region receives a thicker dielectric layer (first film thickness) compared to the deep inner region (second film thickness). This local differentiation ensures that cutting surfaces have adequate dielectric coverage to prevent leak current, while the inner regions maintain optimized electrostatic capacity.

Inventive Principle:

Principle #3Local quality

2Strength

If the dielectric layer is made uniformly thick across the entire anode foil, then the withstand voltage improves, but the electrostatic capacity decreases due to reduced effective surface area

Engineering Contradiction:

Improvewithstand voltageVSAvoidelectrostatic capacity

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent implements a non-uniform dielectric layer thickness distribution where the end surface vicinity region has a greater film thickness to ensure adequate withstand voltage and leak current prevention at cutting surfaces, while the deep inner region maintains a smaller film thickness to preserve effective surface area for electrostatic capacity. This localized differentiation resolves the contradiction between withstand voltage and electrostatic capacity.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the anode foil is cut into smaller pieces for assembly, then the manufacturing flexibility improves, but the cutting surfaces expose metal layers leading to reduced withstand voltage

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidwithstand voltage

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent performs preliminary dielectric layer formation on the end surfaces of the anode foil before cutting. By pre-forming the dielectric layer that extends to the end surfaces, the patent ensures that subsequent cutting operations will expose dielectric material rather than raw metal layers. This preliminary action maintains withstand voltage while enabling manufacturing flexibility.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies dielectric layer treatment specifically to the end surface vicinity region, creating a localized protective layer at the cutting surfaces. This local quality enhancement ensures that when the foil is cut, the exposed surfaces have adequate dielectric coverage to maintain withstand voltage, while the rest of the foil structure remains optimized for electrostatic capacity.

Inventive Principle:

Principle #3Local quality

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 configuration enhances the withstand voltage and reduces leak current by providing a dense, defect-free dielectric layer on the cutting surfaces, improving the overall performance of electrolytic capacitors.

Implementation Method 1

a step of forming a second dielectric layer on the cutting surface by an atomic layer deposition method

Methodology Applied

Scientific EffectAtomic layer deposition: Physical Vapour Deposition

Data Source

PatentUS12014884B2Electrode foil for electrolytic capacitor, electrolytic capacitor, and methods for manufacturing same

Publication Date: 2024.06.18 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An electrode foil for an electrolytic capacitor includes an anode electrode body including a base material part having a porous body portion, and a dielectric layer disposed on a surface of the porous body portion. The anode electrode body has a first main surface in which pores of the porous body portion are opened, a second main surface opposite to the first main surface, and an end surface connecting the first main surface and the second main surface. In the porous body portion, a first film thickness of the dielectric layer in an end surface vicinity region is larger than a second film thickness of the dielectric layer in a deep inner region, the end surface vicinity region being a region within a predetermined distance from the end surface, the deep inner region being a region located away from the first main surface and at a central portion in a direction parallel to the first main surface.