Electrolytic Capacitor Electrode Foil With Oxygen-Blocking Dielectric Layers
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Solution Overview
Problem
Electrolytic capacitors face increased leakage current and reduced insulation due to oxygen migration from high dielectric constant layers to the anode body when high voltage is applied, leading to decreased capacitance and withstand voltage.
Innovation Solution
A dual dielectric layer structure is implemented, where a first dielectric layer with a lower dielectric constant, typically made of silicon or aluminum oxide, is used to suppress oxygen diffusion from a second dielectric layer with a higher dielectric constant, such as tantalum or titanium oxide, ensuring the second layer maintains its insulation and preventing excessive oxygen migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a dielectric layer with high dielectric constant is formed to increase capacitance, then capacitance is improved, but oxygen migrates toward the anode body resulting in increased leakage current and reduced insulation
Solution Approach 1:
The dielectric layer is divided into two distinct layers: a first dielectric layer with lower dielectric constant (3.0-10.0) and a second dielectric layer with higher dielectric constant (10.0-100.0). This segmentation allows each layer to perform its specific function - the first layer suppresses oxygen diffusion while the second layer provides high capacitance
Solution Approach 2:
The first dielectric layer acts as an intermediary barrier between the anode body and the second dielectric layer. It prevents oxygen from migrating from the high dielectric constant layer to the anode body, thereby protecting the insulation while allowing the second layer to maintain high capacitance
2Quantity of substance
If the thickness of the high dielectric constant layer is increased to enhance capacitance, then capacitance is improved, but oxygen diffusion to the anode body increases resulting in higher leakage current
Solution Approach 1:
The dielectric structure is segmented into two layers with different thicknesses and properties. The second layer (high dielectric constant) has greater thickness for capacitance enhancement, while the first layer (lower dielectric constant) provides sufficient thickness to block oxygen diffusion path
Solution Approach 2:
The first dielectric layer serves as a protective intermediary that blocks oxygen diffusion regardless of the thickness of the second layer. This allows the second layer to be made thicker for higher capacitance without proportionally increasing leakage current
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 effectively suppresses the increase in leakage current while enhancing capacitance, maintaining high insulation and withstand voltage, thus achieving a larger capacitance value (CV) with reduced leakage current (LC).
Implementation Method 1
the first dielectric layer is a layer that suppresses oxygen diffusion from the second dielectric layer to the anode body
Data Source
AI summary
An electrode foil for an electrolytic capacitor includes: an anode body that contains a valve action metal; a first dielectric layer that covers at least a part of the anode body; and a second dielectric layer that covers at least a part of the first dielectric layer. The second dielectric layer has a higher dielectric constant than the first dielectric layer, and a thickness T2 of the second dielectric layer is greater than a thickness T1 of the first dielectric layer. The first dielectric layer is a layer that suppresses oxygen diffusion from the second dielectric layer to the anode body.