Dual-Oxide Electrode Foil for Capacitance and Withstand Voltage
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Solution Overview
Problem
Conventional methods for increasing capacitance and reducing leak current in electrolytic capacitors often fail to simultaneously achieve improved withstand voltage.
Innovation Solution
An electrode foil for electrolytic capacitors is designed with a first dielectric layer of a metal oxide, such as TiO2, Ta2O5, or Al2O3, and a second dielectric layer of a different metal oxide, such as SiO2, ZrO2, or HfO2, where the thickness of the second layer is smaller than the first, formed using anodizing and atomic layer deposition methods respectively, to achieve a balance between capacitance and withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a dielectric layer including oxide of a valve metal different from the dielectric layer and an additive such as carbon is formed on the dielectric layer, then capacitance is increased and leak current is reduced, but withstand voltage cannot be improved
Solution Approach 1:
The dielectric structure is segmented into two distinct layers: a first dielectric layer (thickness T1) made of oxide of a valve metal (Ti, Ta, Nb, or Al) and a second dielectric layer (thickness T2) made of oxide of a different metal (Si, Zr, Hf, or Ta). This segmentation allows each layer to contribute differently to the overall performance, with the first layer providing high capacitance and the second layer enhancing withstand voltage.
Solution Approach 2:
Different regions of the dielectric structure are assigned different material compositions and thicknesses to achieve local optimization. The first dielectric layer uses valve metal oxides known for high capacitance, while the second dielectric layer uses metals like Si, Zr, or Hf that provide superior insulation and withstand voltage properties. The thickness ratio T1>T2 creates local quality differences that balance capacitance and voltage resistance.
2Reliability
If the thickness of the second dielectric layer is made smaller than the first dielectric layer, then capacitance is maintained while withstand voltage is improved
Solution Approach 1:
The thickness parameter of the dielectric layers is optimized with T1>T2 to achieve the desired balance. The first dielectric layer has greater thickness to provide sufficient capacitance, while the second dielectric layer has reduced thickness to minimize its impact on total capacitance while still providing the needed withstand voltage enhancement. This parameter optimization resolves the contradiction between capacitance and withstand voltage.
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 results in an electrolytic capacitor with enhanced capacitance and withstand voltage, maintaining a good balance between the two while reducing costs, as evidenced by the increased CV value.
Implementation Method 1
forming a first dielectric layer including an oxide of a first metal by anodizing a base material including the first metal
Implementation Method 2
forming a second dielectric layer including an oxide of a second metal and having a thickness T2 smaller than a thickness T1 of the first dielectric layer so that the second dielectric layer covers at least a part of the first dielectric layer
Data Source
AI summary
An electrode foil for an electrolytic capacitor includes: an anode body including a first metal; a first dielectric layer covering at least a part of the anode body and including an oxide of the first metal; and a second dielectric layer covering at least a part of the first dielectric layer and including an oxide of a second metal. The first metal includes at least one selected from the group consisting of titanium, tantalum, niobium, and aluminum. And the second metal includes at least one selected from the group consisting of silicon, zirconium, hafnium, and tantalum. A thickness T2 of the second dielectric layer is smaller than a thickness T1 of the first dielectric layer.