Solid Electrolytic Capacitor Coating for Humidity Resistance
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Solution Overview
Problem
Conventional solid electrolytic capacitors exhibit increased Equivalent Series Resistance (ESR) in high-temperature and high-humidity environments, compromising their reliability and humidity resistance.
Innovation Solution
A manufacturing method involving sequential application and drying of a first conductive polymer solution, a coating solution containing aromatic sulfonic acid or its salt, and a second conductive polymer solution to form laminated conductive polymer layers, enhancing the capacitor's humidity resistance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional crosslinking agent (p-toluenesulfonic acid with 1,10-diaminodecane) is used to form the solid electrolyte layer, then the outer layer can be satisfactorily coated without local peeling and initial ESR is decreased, but the capacitor exhibits increased ESR in high-temperature and high-humidity environments
Solution Approach 1:
The solid electrolyte layer is divided into multiple sub-layers with different functions: an inner layer (first conductive polymer layer) providing adhesion and basic conductivity, and an outer layer (second conductive polymer layer) providing surface coating quality. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between coating uniformity and humidity resistance.
Solution Approach 2:
A coating layer containing aromatic sulfonic acid or its salt is introduced as an intermediary layer between the inner and outer conductive polymer layers. This intermediary layer acts as a barrier against humidity penetration while maintaining electrical conductivity, preventing the outer layer from peeling and maintaining low ESR in humid environments.
2Ease of manufacture
If the solid electrolyte layer is formed to ensure good outer layer coating, then initial ESR is decreased, but ESR increases in high-temperature and high-humidity environments
Solution Approach 1:
The coating layer containing aromatic sulfonic acid is applied in advance between the inner and outer conductive polymer layers before final assembly. This preliminary action creates a protective barrier that prevents humidity from degrading the interface between layers, ensuring long-term ESR stability in humid environments while maintaining good initial ESR characteristics.
3Device complexity
If a simple single-layer conductive polymer structure is used, then the manufacturing process is simple, but the capacitor shows poor humidity resistance
Solution Approach 1:
The solid electrolyte layer is constructed as a composite structure combining multiple conductive polymer materials with an aromatic sulfonic acid-containing coating layer. This composite structure leverages the adhesion properties of the inner layer, the protective properties of the coating layer, and the surface coating properties of the outer layer, achieving superior humidity resistance while maintaining reasonable manufacturing complexity.
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 a solid electrolytic capacitor with improved humidity resistance and reliability, maintaining ESR performance in challenging environmental conditions.
Implementation Method 1
a first step of applying a first conductive polymer solution in which fine particles of a conductive polymer are dispersed, and drying the solution to form a first conductive polymer layer
Implementation Method 2
a second step of applying, to the first conductive polymer layer, a coating solution containing at least one selected from an aromatic sulfonic acid having, in one molecule of the acid, a carboxyl group and a hydroxyl group, or two carboxyl groups, and salt of the aromatic sulfonic acid, and drying the coating solution
Data Source
AI summary
A first conductive polymer solution in which fine particles of a conductive polymer are dispersed is applied to a dielectric layer of aluminum oxide, and this solution is dried to form a first conductive polymer layer. Next, a coating solution is applied to the first conductive polymer layer, this solution containing at least one selected from an aromatic sulfonic acid having, in one molecule of the acid, a carboxyl group and a hydroxyl group, or two carboxyl groups, and a salt of the aromatic sulfonic acid. The solution is then dried to form a coating layer. Next, a second conductive polymer solution is applied to the coating layer, the solution being a solution in which fine particles of a conductive polymer are dispersed. This solution is then dried to form a second conductive polymer layer. This process gives a solid electrolyte layer of a capacitor element.