Electrolytic Capacitor Foil Coating for Low-ESR Polymer Adhesion
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Solution Overview
Problem
The increasing demand for higher voltage alternators in mild hybrid systems requires electrolytic capacitors with reduced equivalent series resistance (ESR) to manage higher ripple currents, but existing methods struggle to adequately adhere a sufficient amount of conductive polymer to the capacitor elements.
Innovation Solution
A method involving the application of a conductive polymer dispersion onto an electrode foil using a coating method, followed by partial removal of the dispersion medium, to form a conductive polymer layer that covers at least 90% of the foil's surface, enhancing the adhesion and reducing ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the amount of conductive polymer is increased to reduce ESR, then the ESR decreases, but it becomes difficult to allow a sufficient amount of conductive polymer to adhere onto the capacitor element
Solution Approach 1:
The conductive polymer layer is divided into multiple layers (first conductive polymer layer and second conductive polymer layer) with different components and functions. The first layer provides base adhesion and conductivity, while the second layer enhances conductivity and reduces ESR, allowing each layer to be optimized independently for both adhesion and low ESR performance
Solution Approach 2:
Different regions of the conductive polymer layer have different properties - the first layer contains specific components for adhesion, while the second layer contains different components optimized for conductivity. This local differentiation allows the structure to simultaneously achieve good adhesion and low ESR
2Area of stationary object
If a coating method is used to apply conductive polymer dispersion, then the coverage area increases, but the adhesion of conductive polymer to the electrode foil surface becomes challenging
Solution Approach 1:
The electrode foil surface undergoes preliminary treatment (etching and/or roughening) before applying the conductive polymer dispersion. This preliminary action creates a textured surface that mechanically interlocks with the polymer layer, significantly improving adhesion while maintaining wide coverage
Solution Approach 2:
The conductive polymer layer is formulated as a composite material containing the conductive polymer component and a dispersant component. This composite structure improves both the coating processability for wide coverage and the adhesion to the electrode surface
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 allows for a substantial increase in the amount of conductive polymer on the capacitor element, resulting in a capacitor with lower ESR and improved heat resistance, suitable for high ripple current applications, while also reducing impurities and enhancing withstand voltage.
Implementation Method 1
forming a first conductive polymer layer containing the first conductive polymer component, by applying the first conductive polymer dispersion to a surface of the electrode foil by a coating method
Implementation Method 2
at least partially removing the first dispersion medium
Data Source
AI summary
A method for producing an electrolytic capacitor, the method including steps of: preparing an electrode foil; preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium; forming a first conductive polymer layer containing the first conductive polymer component, by applying the first conductive polymer dispersion to a surface of the electrode foil by a coating method, and then at least partially removing the first dispersion medium; and fabricating a capacitor element, using the electrode foil having the first conductive polymer layer.