Distortion-free screen-printed anodes on thin Ta/Nb foils
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Solution Overview
Problem
Conventional methods for producing tantalum anodes, such as pressing Ta powder onto thin Ta sheets, result in severe distortion during sintering, limiting the production of flat capacitors with low overall height and increasing material costs due to the use of thicker foils.
Innovation Solution
A method involving surface oxidation of tantalum or niobium films, followed by oxide diffusion through heating, and the application of a paste comprising tantalum or niobium powder, which is then sintered, reduces distortion by pre-stretching the film, allowing for the production of ultra-flat anodes on very thin foils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If thin Ta foils are used for anode production, then material costs and capacitor height are reduced, but severe distortion occurs during sintering
Solution Approach 1:
The patent applies preliminary oxidation to the Ta foil surface before paste application and sintering. This pre-oxidation creates a stable oxide layer that prevents severe distortion during subsequent sintering, enabling the use of thin foils without sacrificing flatness. The preliminary action of oxidation prepares the substrate to withstand the thermal processing that would otherwise cause warping.
Solution Approach 2:
The patent changes the chemical state of the foil surface by oxidizing it before sintering. This parameter change (from metallic Ta to oxidized Ta surface) fundamentally alters how the foil responds to thermal stress during sintering, preventing the severe distortion that would occur with unoxidized thin foils.
2Quantity of substance
If higher-capacity tantalum powders and NbO powders are used, then energy storage density is improved, but distortion development is promoted
Solution Approach 1:
The patent applies preliminary oxidation to the Ta foil surface before applying high-capacity powders and sintering. This pre-oxidation creates a stable foundation that prevents distortion even when high-capacity powders like NbO are used, which would otherwise promote severe warping during sintering.
3Manufacturing precision
If thicker Ta foils are used to avoid distortion, then anode flatness is maintained, but material costs and capacitor height increase
Solution Approach 1:
The patent uses preliminary oxidation as a preparatory step that enables thin foils to maintain flatness during sintering. This eliminates the need to use thicker foils as a compensatory measure, thereby reducing material costs and capacitor height while maintaining anode flatness.
4Ease of manufacture
If conventional pressing of Ta powder is used, then anode production is simplified, but large aspect ratios cannot be achieved
Solution Approach 1:
The patent replaces the conventional mechanical pressing method with a printing-based approach combined with preliminary oxidation. This substitution enables better control over paste distribution and reduces distortion, making it possible to produce anodes with large aspect ratios (flat capacitors with low height-to-area ratio) that cannot be achieved by pressing.
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 enables the production of distortion-free, ultra-flat anodes suitable for high-capacity electrolytic capacitors, improving heat dissipation and simplifying electrical contacting, while reducing material costs and maintaining high energy storage density.
Implementation Method 1
allowing the oxides formed on the surface to diffuse in by heating the film
Implementation Method 2
heating the film oxidized on the surface to a temperature above 600 °C, preferably for a period of at least 10 minutes
Data Source
AI summary
The present invention pertains to the field of production of anodes. The present invention more particularly relates to a method for producing distortion-free anodes by means of stencil or screen printing on thin tantalum or niobium foils. The present invention also relates, furthermore, to anodes obtainable by the method of the invention.