Graded-Porosity Electrode Foil for Deep Dielectric Coverage
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Solution Overview
Problem
Existing methods for increasing the capacitance of electrolytic capacitors, such as etching and atomic layer deposition, face challenges in forming a sufficient dielectric layer in deep portions of metal porous electrodes due to porosity gradients, leading to incomplete coverage and reduced performance.
Innovation Solution
The electrode foil is designed with a metal porous portion having distinct porosity regions (P1 < P2 < P3) in its thickness direction, achieved through a multi-step etching process with varying current densities and washing steps, allowing for a continuous metal core and a dielectric layer that effectively covers the surface, facilitating deep penetration of source gases during deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If etching is applied to increase surface area, then capacitance increases, but porosity distribution becomes non-uniform making dielectric layer formation difficult in deep portions
Solution Approach 1:
The patent applies local quality by creating distinct porosity zones at different depths of the metal porous portion. The surface layer has higher porosity (30-80%) to facilitate source gas penetration, while the deep portion has lower porosity (10-60%) to enable complete dielectric layer formation. This spatial variation in porosity allows the dielectric layer to be formed uniformly throughout the entire depth of the metal porous portion, resolving the contradiction between high capacitance and manufacturing precision.
2Manufacturing precision
If atomic layer deposition is used to form dielectric layer, then source gas may not reach deep portions, but increasing porosity improves gas penetration
Solution Approach 1:
The patent segments the metal porous portion into multiple porosity zones along the thickness direction. By dividing the structure into a surface layer with higher porosity and a deep portion with lower porosity, the invention enables source gas to penetrate effectively to deep portions during atomic layer deposition while maintaining structural integrity and controlling the overall porosity distribution.
3Manufacturing precision
If multi-step etching with washing steps is applied, then porosity distribution is controlled, but process complexity increases
Solution Approach 1:
The patent employs periodic action through alternating etching and washing steps in a cyclic manner. Multiple etching steps with intermediate washing steps create the desired porosity distribution pattern. This periodic process sequence allows precise control over porosity at different depths while maintaining a systematic and manageable manufacturing process.
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 approach enables the formation of a favorable dielectric layer even in deep portions, resulting in a high-performance electrolytic capacitor with improved capacitance and reduced leakage current and ESR.
Implementation Method 1
a first electrolysis step of applying an electric current of a first current density to the metal foil in a first processing solution, to obtain a first etched foil; a second electrolysis step of applying an electric current of a second current density to the first etched foil in a second processing solution after the first electrolysis step
Implementation Method 2
a first washing step of washing the first etched foil, after the first electrolysis step and before the second electrolysis step; and a second washing step of washing the second etched foil, after the second electrolysis step and before the third electrolysis step
Data Source
AI summary
An electrode foil for an electrolytic capacitor including a metal porous portion, and a metal core portion continuous to the metal porous portion. When the metal porous portion is equally divided in three in a thickness direction of the metal porous portion into a first region, a second region, and a third region sequentially from the metal core portion side, the first region has a porosity P1, the second region has a porosity P2, and the third region has a porosity P3, satisfying P1<P2<P3.