Electrolytic Capacitor Shell Design for Heat-Safe IMD Packaging
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Solution Overview
Problem
High voltage capacitors used in implanted medical devices face challenges with high energy density requirements, leading to increased manufacturing complexity, cracking, and heat build-up due to tight tolerances and complex geometries, which affect reliability and cost.
Innovation Solution
A capacitor design with a capacitor stack enclosed by a first and second cover portion, utilizing molybdic acid etching for increased anode surface area, simplified geometries, and automated manufacturing processes to reduce cracking and heat issues, with a neutrally charged cover portion to eliminate additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If high energy density is achieved through increased surface area creation per anode, then capacitor volume decreases, but manufacturing tolerances become tighter leading to higher cost and lower reliability
Solution Approach 1:
The patent changes the geometric parameters of the capacitor components, specifically using non-circular cross-sections (rectangular, square, or triangular) instead of traditional circular shapes. This parameter change allows for tighter packing and higher surface area density without requiring extremely tight manufacturing tolerances, as the geometric shapes can be more easily manufactured with standard tolerances while still achieving the desired space efficiency.
Solution Approach 2:
The patent transitions from traditional two-dimensional planar arrangements to three-dimensional stacked configurations with multi-layer anodes and cathodes. This dimensional change enables higher energy density by utilizing vertical space and creating multiple active surfaces within the same footprint, thereby reducing overall capacitor volume without compromising reliability through overly tight tolerances.
2Device complexity
If thin PEEK pockets are used for protection of the capacitor, then packaging efficiency improves, but manufacturing complexity increases and cracking risk increases
Solution Approach 1:
The patent employs thin PEEK (polyether ether ketone) pockets as protective encapsulation for the capacitor stack. These thin film structures provide necessary mechanical protection and electrical isolation while maintaining compact packaging. The PEEK material offers a good balance between protection and flexibility, allowing for efficient packaging without excessive thickness that would increase overall device size.
Solution Approach 2:
The patent uses composite construction with PEEK material combined with the capacitor stack and electrolyte layers. This composite approach integrates structural protection and electrical functionality in a unified design, where the PEEK pockets serve both as mechanical protectors and as part of the overall packaging structure, reducing the need for separate protective components and simplifying manufacturing.
3Reliability
If negative output connection is used, then internal resistance decreases, but heat build-up and bubbling increase leading to failure
Solution Approach 1:
The patent extracts the harmful negative output effect by implementing a neutral output design. Instead of allowing the traditional negative terminal to create high internal resistance and subsequent heat buildup, the design reconfigures the output connections to achieve electrical neutrality at the output terminals. This extraction of the harmful negative polarity effect eliminates the root cause of excessive heat generation and bubbling, thereby improving reliability without sacrificing performance.
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 enhances energy density, reduces manufacturing complexity, and improves reliability and cost-effectiveness by allowing automated production and neutral charge management, thus minimizing size and heat-related failures.
Implementation Method 1
utilizing molybdic acid to provide galvanic aluminum dissociation in a low pH etch solution before the electrochemical process is implemented to increase initiation sites before etching
Implementation Method 2
High voltage capacitors are utilized as energy storage reservoirs in many applications, including IMDs
Implementation Method 3
The electrolytic paper may be impregnated by an electrically conductive electrolyte
Data Source
AI summary
A capacitor is provided that includes a capacitor stack including an anode layer, cathode layer, and electrolytic layer electrically coupled together, the capacitor stack including a capacitor stack periphery. The capacitor also includes a first cover portion having a first cover portion periphery that aligns with the capacitor stack periphery, and a second cover portion having a second cover portion periphery that aligns with the capacitor stack periphery and received the first cover portion periphery to form a shell body for encasing the capacitor stack therein. The capacitor stack is isolated from the second cover portion to provide a neutrally charged second cover portion that is electrically coupled within an implanted medical device.