Electrophoretic Cathode for Wet Electrolytic Capacitors
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Solution Overview
Problem
Wet electrolytic capacitors face limitations such as low reverse voltage capability and limited capacitance, particularly with carbon cathodes, and handling thin tantalum cylinders is difficult and expensive.
Innovation Solution
The development of a wet electrolytic capacitor with a cathode element formed by electrophoretically deposited refractory metal powder of uniform thickness, surrounded by a porous pellet anode and electrolyte within a metal case, allowing for high capacitance and reverse voltage capability with reduced material usage and easier handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thin tantalum cylinder is used as the cathode, then capacitance per volume is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
The patent replaces the mechanical process of forming and handling thin tantalum cylinders with an electrophoretic deposition process. The cathode is formed by electrophoretically depositing tantalum particles from a slurry onto the anode, eliminating the need for mechanical cylinder formation and handling operations.
Solution Approach 2:
The patent changes the physical state and form of the cathode material from solid cylindrical tantalum to a electrophoretically deposited layer formed from a slurry suspension. This parameter change allows for easier processing and reduced manufacturing complexity while maintaining the desired capacitance properties.
2Ease of operation
If a liner or sleeve is used for the cathode, then handling is simplified, but space available for anodes is reduced
Solution Approach 1:
The patent merges the cathode formation process with the capacitor assembly process. The cathode is electrophoretically deposited directly onto the anode structure, combining what would otherwise be separate components (anode and cathode) into an integrated assembly, thereby eliminating the need for additional liners or sleeves.
Solution Approach 2:
The patent transitions from using a three-dimensional cylindrical cathode structure to a thin conformal coating deposited directly on the anode surface. This dimensional change from bulk cylinder to surface coating maximizes the space available for anodes while maintaining cathode functionality.
3Ease of manufacture
If carbon is used as the cathode, then cost is reduced, but reverse voltage capability and capacitance are limited
Solution Approach 1:
The patent uses a composite cathode structure consisting of electrophoretically deposited tantalum particles in a slurry formulation. This composite approach combines the benefits of tantalum (high reverse voltage capability and capacitance) with a cost-effective slurry-based processing method, achieving both performance and cost objectives.
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 solution enables high capacitance and reverse voltage capability with minimal space intrusion, reducing the need for expensive tantalum and simplifying handling, while achieving cost savings and increased anode space.
Implementation Method 1
a cathode element formed of an electrophoretically deposited refractory metal powder of a uniform thickness disposed within the metal case and surrounding the anode
Data Source
Figure 1
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Figure 4
AI summary
An electrolytic capacitor (10) includes a metal case (12), a porous pellet anode (18) disposed within the metal case, an electrolyte (16) disposed within the metal case, and a cathode element (14) formed of an elect-rophoretically deposited metal or metal oxide powder of a uniform thickness disposed within the metal case and surrounding the anode. A method of manufacturing an electrolytic capacitor includes providing a metal case (12), electrophoretically depositing on the metal can a refractory metal oxide to form a cathode element (14), and placing a porous pellet anode (18) and an electrolyte (16) within the can such that the cathode element (14) and the anode element (18) being separated by the electrolyte (16).