Wet Electrolytic Capacitor Anode Sinter Neck Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High voltage electrolytic capacitors used in implantable medical devices face challenges in achieving high energy density and capacitance due to limitations in surface area and dielectric layer failure at high voltages, particularly in porous sintered tantalum capacitors.
Innovation Solution
A wet electrolytic capacitor design featuring a planar anode formed from anodically oxidized sintered tantalum powder with a specific charge of 15,000 μF*V/g or more, combined with a conductive-coated metal substrate cathode, and a fluidic working electrolyte, which enhances capacitance and withstands high voltages by forming large sinter necks between particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If porous sintered tantalum pellets are used to increase surface area, then capacitance is improved, but dielectric layer failure occurs at high voltages due to thin sinter necks
Solution Approach 1:
The patent changes the physical and chemical parameters of the tantalum powder, specifically using low specific charge powder (≤3.0 μC/g) with controlled particle size distribution (D10-D90 ratio of 0.4-0.7) and optimized pore size (0.5-2.0 μm). These parameter changes enable the formation of sufficiently large sinter necks that can support the dielectric layer at high voltages while maintaining high surface area for capacitance.
Solution Approach 2:
The patent creates a composite structure by combining tantalum powder particles with specific properties into a sintered pellet matrix. The composite nature of the sintered structure with optimized pore distribution and sinter neck formation creates a material that simultaneously achieves high surface area and mechanical strength to prevent dielectric failure.
2Use of energy by moving object
If high specific charge powder is used to increase capacitance, then energy density is improved, but sinter necks become too thin and cause dielectric failure at high voltages
Solution Approach 1:
The patent fundamentally changes the specific charge parameter of the tantalum powder to be low (≤3.0 μC/g), which counterintuitively allows for the formation of larger sinter necks. This parameter change resolves the contradiction by enabling sufficient mechanical strength at sinter necks while maintaining high energy density through optimized pore structure and surface area.
3Volume of moving object
If metal foils are used instead of sintered pellets, then device size is reduced, but surface area and capacitance are limited
Solution Approach 1:
The patent employs porous sintered tantalum pellets with optimized pore size (0.5-2.0 μm) and pore volume (20-40%) to achieve extremely high surface area within a compact volume. The porous structure provides vast internal surface area for capacitance while the overall pellet dimensions keep the device size manageable for implantable applications.
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 design achieves higher capacitance levels and improved voltage withstand, enabling more compact and efficient high voltage capacitors suitable for implantable medical devices, such as defibrillators, with enhanced electrical properties and reduced risk of dielectric layer failure.
Implementation Method 1
The valve metal powder is formed by reacting an oxide of a valve metal compound with a reducing agent
Implementation Method 2
The anode comprises an anodically oxidized pellet formed from a pressed and sintered valve metal powder
Implementation Method 3
a fluidic working electrolyte in communication with the anode and cathode
Implementation Method 4
sintering the pellet; anodically oxidizing the sintered pellet to form a dielectric layer
Data Source
AI summary
A wet electrolytic capacitor containing a cathode, fluidic working electrolyte, and planar anode formed from an anodically oxidized sintered porous pellet is provided. The pellet may be formed from a pressed valve metal powder, which in turn, is formed by reacting an oxide of a valve metal compound (e.g., tantalum pentoxide) with a reducing agent that contains a metal having an oxidation state of 2 or more (e.g., magnesium). Through the use of such a powder, the present inventors have discovered that higher capacitance levels can be achieved than previously thought possible for the high voltage capacitors employed in implantable medical devices.