Wet Tantalum Capacitor Cathode Filament Fabrication
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Solution Overview
Problem
The production of high capacitance tantalum electrolytic capacitors faces challenges with fine powders and flakes, including sensitivity to sintering temperature, anodization conditions, poor flowability, and incomplete electrolyte infiltration, which affect the capacitance and reliability of capacitors.
Innovation Solution
The process involves forming tantalum or niobium components into elongated elements, cutting them into segments, leaching out the ductile metal, and casting them into a thin sheet using a slurry, allowing for the creation of uniform and high-surface-area cathodes for wet tantalum capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fine tantalum powders and flakes are used to fabricate cathodes, then high surface area and high capacitance can be achieved, but sensitivity to sintering temperature and anodization conditions increases
Solution Approach 1:
The invention changes the physical form parameter of the cathode material from fine powders/flakes to filaments with diameter of 0.5-10 micrometers. This parameter change maintains high surface area while significantly reducing sensitivity to sintering temperature and anodization conditions, as filaments provide more consistent geometric properties compared to irregular powder particles.
2Quantity of substance
If fine tantalum powders are used for cathode fabrication, then high surface area is achieved, but poor flowability and incomplete electrolyte infiltration occur
Solution Approach 1:
The invention segments the cathode structure into discrete filaments with controlled diameter and length ratios. This segmentation creates a structured porous network that improves both flowability during manufacturing and electrolyte infiltration during operation, while maintaining high surface area through the filament geometry rather than relying on fine powder particles.
3Ease of manufacture
If conventional powder pressing and sintering methods are used, then cathode structure is formed, but mechanical strength and density uniformity are compromised
Solution Approach 1:
The invention uses a composite approach by forming filaments within a ductile metal matrix (such as copper), then leaching out the matrix material. This composite fabrication method provides mechanical strength during handling and processing, while the resulting filament structure achieves uniform density and improved mechanical properties in the final cathode product.
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 method enables consistent and reliable high capacitance values, improved mechanical strength, and cost-effectiveness, facilitating large-scale manufacturing of capacitors with uniform density and high yield.
Implementation Method 1
a plurality of filaments of a valve metal, preferably tantalum, are combined with a ductile material, such as copper, to form a billet
Implementation Method 2
The billet is then sealed in an extrusion can, and extruded and drawn to a point where the filament diameter is in the range of 0.2 to 5.0 microns in diameter. The second metal is then removed, preferably by leaching in mineral acids, leaving the valve metal filaments intact.
Implementation Method 3
The billet is then sealed in an extrusion can, and extruded and drawn to a point where the filament diameter is in the range of 0.2 to 5.0 microns in diameter
Implementation Method 4
After sintering, the compact is anodized to form the dielectric tantalum pentoxide (Ta2O5) on the exposed surfaces
Implementation Method 5
The porous regions of the anodized compact are then infiltrated with a conductive electrolyte
Data Source
AI summary
A process for making a valve metal material useful for forming electrolytic devices comprising the steps of: establishing multiple tantalum or niobium components in a billet of a ductile material; working the billet to a series of reduction steps to form said tantalum or niobium components into elongated elements; cutting the resulting elongated elements and leaching the ductile metal from the elements; washing and mixing the cut elements; and forming the cut elements into a sheet. The resulting sheet may be formed into anodes and cathodes and assembled to form a wet electrolytic capacitor.