Etched Anode Foil With Masked Tabs For Capacitor Strength

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Solution Overview

Problem

Conventional electrolytic capacitor foils face a trade-off between increased capacitance and retained strength, as higher surface area etching reduces foil strength, limiting the useable capacitance gain in applications like implantable cardioverter defibrillators where space and reliability are critical.

Innovation Solution

A non-uniform etching method is employed using an etch-resistant mask to protect tab connection areas, allowing for increased surface area expansion while maintaining foil strength, achieved by applying the mask to define unmasked areas for etching and using a specific etch electrolyte solution to enhance capacitance without compromising strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If uniform etching is applied across the entire foil surface to increase capacitance, then surface area and capacitance increase, but foil strength is reduced

Engineering Contradiction:

ImprovecapacitanceVSAvoidfoil strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent applies different etching treatments to different regions of the foil. The center region undergoes aggressive etching to maximize capacitance, while the edge regions are masked and left unetched or lightly etched to maintain structural strength. This local differentiation resolves the contradiction by optimizing each region for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The foil surface is segmented into distinct zones: a central high-capacitance zone that is heavily etched, and peripheral strength-maintaining zones that are masked. The mask physically divides the etching process into spatially separated regions, allowing independent optimization of capacitance and strength.

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If aggressive etching is used to maximize surface area expansion, then capacitance increases, but alpha-phase boehmite oxide formation increases causing brittleness

Engineering Contradiction:

Improvesurface areaVSAvoidfoil usability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The mask is applied before the etching process to prevent excessive etching at the edges. This preliminary protective action prevents the formation of alpha-phase boehmite oxide that would otherwise occur during aggressive etching, thereby preventing brittleness before it can develop.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The masking process converts what would be a harmful effect (excessive etching leading to alpha-phase formation and brittleness) into a beneficial outcome (protected edge regions that maintain structural integrity). The mask transforms the potential damage into a design feature that enhances overall reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Use of energy by moving object

If the entire foil is etched to increase capacitance, then energy density increases, but device volume decreases less than expected due to strength limitations

Engineering Contradiction:

Improveenergy densityVSAvoiddevice volume

Core Design Contradiction:

Use of energy by moving objectVSVolume of moving object

Solution Approach 1:

By applying local quality differentiation through masking, the patent enables greater surface area expansion in the center region without compromising overall foil strength. This allows higher energy density to be achieved while maintaining the structural integrity needed for compact device design.

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

The method results in higher capacitance with improved leakage current and reduced deformation, minimizing alpha-phase boehmite oxide formation, which would otherwise increase brittleness and reduce the foil's usability, allowing for more compact and reliable electrolytic capacitors.

Implementation Method 1

surface area of the foil is increased by electrochemically removing portions of the foil to create etch tunnels

Methodology Applied

Scientific EffectElectrochemical etching: Electrolysis

Implementation Method 2

facilitation of laser cutting

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS9852849B2Using etch resist patterns and formation for facilitation of laser cutting, particle and leakage current reduction

Publication Date: 2017.12.26 PACESETTER INC

AI summary

A process for creating an anode foil for use in an electrolytic capacitor of an implantable cardioverter defibrillator is provided. The process includes placing a partially masked bulk metal foil in an etch electrolyte solution to etch exposed area of the bulk metal foil, removing the etch-resistant mask to expose the unetched areas, widening the bulk metal foil, and partially cutting the bulk metal foil between a plurality of unetched areas to form a partially detached etched foil anode, such that the unetched areas are not cut and the unetched areas serve as attachment tabs to keep the partially detached etched foil anode attached to the bulk metal foil. Additionally, the process may include an oxide formation step, wherein the step of partially cutting the bulk metal foil is performed after the etching and widening steps, and before the oxide formation step.