Solid Electrolytic Capacitor Using Phosphonic Acid Coupling Agent
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Solution Overview
Problem
Existing solid electrolytic capacitors face issues with high equivalent series resistance (ESR) and leakage current due to poor adhesion between inorganic dielectric layers and organic conductive polymer layers, which is exacerbated by the variability of silane coupling agents in response to substrate conditions and ambient moisture.
Innovation Solution
A solid electrolytic capacitor design that uses a coupling agent with a phosphonic acid group to enhance adhesion between dielectric and conductive polymer layers, eliminating the need for silane coupling agents and improving capacitance and reducing ESR and leakage current by forming multiple layers with phosphonic acid group-containing coupling agent layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silane coupling agent is used to treat the dielectric layer before depositing the conductive polymer layer, then adhesion between the layers is improved, but the adhesion becomes variable depending on substrate surface conditions and ambient moisture
Solution Approach 1:
The patent changes the chemical parameters of the coupling agent from silane-based to phosphonic acid-based. Phosphonic acid groups have different chemical properties that enable consistent reaction with the dielectric layer surface regardless of hydroxyl content variations or ambient moisture conditions, thereby achieving reliable and consistent adhesion
Solution Approach 2:
The patent replaces the silane coupling agent with a phosphonic acid-containing coupling agent that can be applied as a simple solution treatment. This new coupling agent system is more robust and less sensitive to processing variations, providing dependable adhesion without requiring precise control of substrate surface conditions or ambient environment
2Strength
If the dielectric layer surface is treated with a silane coupling agent, then adhesion is enhanced, but leakage current increases due to poor adhesion deterioration
Solution Approach 1:
The patent changes the chemical composition of the coupling agent from silane to phosphonic acid derivatives. This parameter change results in better adhesion that prevents deterioration over time, thereby maintaining low leakage current while still achieving the desired adhesion enhancement
3Strength
If a silane coupling agent is used to reduce ESR, then adhesion is improved, but ESR increases due to adhesion deterioration
Solution Approach 1:
The patent changes the coupling agent chemistry from silane to phosphonic acid-based compounds. This parameter change achieves superior and stable adhesion that prevents ESR increase over time, while still reducing initial ESR through improved interfacial contact between layers
4Strength
If multiple treatments with silane coupling agent and conductive polymer layer formation are repeated, then adhesion is improved, but the process complexity increases and adhesion remains variable
Solution Approach 1:
The patent extracts and eliminates the need for repeated treatment cycles by using a phosphonic acid-containing coupling agent that achieves sufficient adhesion in a single treatment step. This simplifies the fabrication process while maintaining reliable adhesion
Solution Approach 2:
The patent changes the coupling agent parameters to phosphonic acid derivatives that provide effective adhesion enhancement in fewer treatment steps, reducing process complexity while achieving consistent results
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 use of phosphonic acid group-containing coupling agents increases the coverage and adhesion between dielectric and conductive polymer layers, resulting in capacitors with higher capacitance and lower ESR and leakage current, while providing superior storage stability and improved conductivity.
Implementation Method 1
a coupling agent layer which is formed on the dielectric layer and contains a coupling agent having a phosphonic acid group
Implementation Method 2
a conductive polymer layer which is formed on the coupling agent layer
Implementation Method 3
a dielectric layer which is formed on a surface of the anode
Data Source
AI summary
A solid electrolytic capacitor comprising an anode composed of a valve metal or its alloy, a dielectric layer formed on a surface of the anode, a coupling agent layer formed by subjecting the dielectric layer to a surface treatment with a coupling agent having a phosphonic acid group, a conductive polymer layer formed on the coupling agent layer, and a cathode layer formed on the conductive polymer layer.