Wet Tantalum Capacitor Anode Powder for High-Voltage Reliability
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Solution Overview
Problem
Existing high voltage tantalum electrolytic capacitors for implantable medical devices face challenges in achieving high energy density due to the formation of relatively large sinter necks between tantalum powder particles, leading to dielectric layer failure at high voltages.
Innovation Solution
The development of a wet tantalum electrolytic capacitor with an anode formed from a specific tantalum powder having a low specific capacitance range of 11,000 µF*V/g to 14,000 µF*V/g, combined with a pseudocapacitive ruthenium oxide coating on the cathode, and a hermetically sealed casing to enhance electrical performance and volumetric efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high specific charge tantalum powder is used to increase energy density, then capacitance is improved, but sinter necks become thin and dielectric layer fails at high voltages
Solution Approach 1:
The patent changes the particle morphology parameter from conventional spherical/irregular shapes to specifically nodular or angular shapes with controlled size distributions. This morphological parameter change results in thicker sinter necks during the sintering process, which maintains dielectric layer integrity at high voltages while preserving high energy density through optimized particle packing and contact areas.
Solution Approach 2:
The patent creates local quality differences by ensuring that sinter necks at critical locations (particle contact points) have enhanced thickness and strength compared to other regions. The nodular or angular particle morphology promotes localized material accumulation at neck regions during sintering, providing targeted reinforcement where the dielectric layer is most vulnerable to high voltage stress.
2Quantity of substance
If sinter necks are made thinner to increase specific charge, then capacitance per gram increases, but dielectric failure occurs at high voltages
Solution Approach 1:
The patent introduces asymmetry in particle morphology by using nodular or angular shapes rather than symmetric spherical particles. This asymmetric geometry creates unequal stress distribution and material flow during sintering, promoting preferential material accumulation at neck regions. The result is enhanced sinter neck strength without sacrificing the high specific charge required for high energy density.
3Volume of moving object
If capacitor size is reduced for implantable devices, then device miniaturization is achieved, but energy density requirements increase
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: particle size distribution, particle morphology (nodular/angular), and sintering conditions. These parameter changes work together to achieve superior particle packing density and enhanced specific charge values, enabling high energy density in compact capacitor volumes suitable for implantable medical devices.
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 solution results in a capacitor with improved energy density and reduced dielectric layer failure at high voltages, suitable for implantable medical devices like implantable defibrillators.
Implementation Method 1
The tantalum powder is formed by reacting an oxide of a tantalum compound with a reducing agent that contains a metal having an oxidation state of 2 or more
Implementation Method 2
a porous sintered tantalum pellet. For example, a tantalum pellet may be formed by compressing a tantalum powder under high pressure followed by sintering at high temperature to form a sponge-like structure
Implementation Method 3
an anodically oxidized tantalum pellet formed from a pressed and sintered tantalum powder
Data Source
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AI summary
A wet tantalum electrolytic capacitor containing a cathode, fluidic working electrolyte, and anode formed from an anodically oxidized sintered porous tantalum pellet is provided. The pellet is formed from a pressed tantalum powder. The tantalum powder is formed by reacting a tantalum oxide compound, for example, tantalum pentoxide, with a reducing agent that contains a metal having an oxidation state of 2 or more, for example, magnesium. The resulting tantalum powder is nodular or angular and has a specific charge that ranges from about 11,000 µF*V/g to about 14,000 µF*V/g. Using this powder, wet tantalum electrolytic capacitors have breakdown voltages that ranges from about 250 volts to about 400 volts. This makes the electrolytic capacitors ideal for use in an implantable medical device.