Angled Leadwire Embedding in Planar Anode Capacitors
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Solution Overview
Problem
High voltage electrolytic capacitors used in implantable medical devices, such as defibrillators, face challenges in minimizing size while maintaining high energy density and electrical performance due to high equivalent series resistance and mechanical weaknesses from leadwire connections.
Innovation Solution
A planar anode for wet electrolytic capacitors is developed, comprising an anodically oxidized pellet formed from pressed and sintered powder with a leadwire embedded at an angle, reducing the likelihood of wire pull-out and enhancing electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a multi-anode stack configuration is used to increase energy density, then the number of cathodes and paper spacers is reduced, but the equivalent series resistance increases due to tortuous charge flow paths
Solution Approach 1:
The anode is divided into multiple discrete anode elements (first anode element, second anode element, etc.) that are arranged in a stack configuration. Each anode element has its own leadwire connection point, allowing independent electrical connections rather than requiring charge to flow through tortuous paths through continuous anode material.
Solution Approach 2:
The leadwires are extended in a longitudinal direction away from the anode stack, and the anode elements are arranged with spacing in the longitudinal direction. This dimensional arrangement allows charge to flow through multiple parallel paths rather than a single tortuous path, reducing equivalent series resistance while maintaining high energy density.
2Object-generated harmful factors
If a leadwire is welded to a metal strip to minimize contact with the anode body, then unnecessary contact is reduced, but gravitational force causes the wire to pull out of the anode
Solution Approach 1:
The leadwire is embedded within a leadwire extension structure that is integrated with the anode element. The leadwire is contained within the leadwire extension, which is itself integrated with the anode element structure, creating a nested arrangement that strengthens the connection while minimizing direct leadwire contact with the anode body.
Solution Approach 2:
The leadwire assembly comprises multiple components including the leadwire itself, the leadwire extension, and the anode element, forming a composite structure. This composite construction distributes mechanical stresses and strengthens the overall connection, preventing wire pull-out while maintaining minimal contact with the anode body.
3Quantity of substance
If metal foil is etched to increase surface area, then capacitance is improved, but the surface area is still limited
Solution Approach 1:
The anode elements are formed from porous anodized metal foil. The porous structure provides a dramatically increased effective surface area compared to smooth metal foil, allowing for higher capacitance while maintaining a compact physical footprint. The porosity is created through anodization that forms a porous oxide layer on the metal foil surface.
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 improved volumetric efficiency and energy density, with reduced equivalent series resistance and enhanced mechanical robustness, making it suitable for compact medical devices.
Implementation Method 1
the gravitational force imparted by hanging can nevertheless cause the wire to pull out of the anode
Implementation Method 2
The anode comprises an anodically oxidized pellet formed from a pressed and sintered powder
Implementation Method 3
The capacitance of the electrolytic capacitor is determined by the extent of roughing (the surface area) of the anode foil and the thickness and the dielectric constant of the oxide film
Implementation Method 4
an anodically oxidized pellet formed from a pressed and sintered powder
Implementation Method 5
an electrolyte in communication with the anode and the cathode
Data Source
AI summary
A relatively thin planar anode for use in a wet electrolytic capacitor is provided. An anode leadwire is embedded within the anode and extends in a longitudinal direction therefrom. The wire may be formed from any electrically conductive material, such as tantalum, niobium, aluminum, hafnium, titanium, etc., as well as electrically conductive oxides and/or nitrides of thereof. To reduce the tendency of the leadwire to pull out of the anode due to stresses encountered during manufacturing (e.g., sintering) and/or use of the capacitor, the manner in which the wire is inserted is selectively controlled in the present invention. That is, at least a portion of the wire within the anode is bent at an angle relative to the longitudinal axis of the wire. This “bend” reduces the ease to which the wire can be pulled out in the longitudinal direction after the anode is pressed and sintered.