Shaped Anode Wire Bridging Contoured Trough in Pressed Powder Capacitors
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Solution Overview
Problem
Capacitors with pressed powder anode pellets are prone to cracking at the contoured trough, which can render them partially or completely inoperable, posing a critical risk in implantable medical devices like cardiac defibrillators.
Innovation Solution
A shaped anode wire with an embedded portion that bridges the lateral extent of the contoured trough, ensuring electrical continuity even if a crack develops, preventing the anode wire from breaking and maintaining functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a contoured trough is provided in the anode pellet to accommodate the terminal pin, then space for electrical connection is improved, but the fracture strength of the anode pellet deteriorates
Solution Approach 1:
The anode wire is pre-shaped with an embedded portion that spans the contoured trough before the anode pellet is assembled. This preliminary shaping ensures that the wire is positioned to bridge potential crack paths from the outset, preventing crack propagation that would otherwise occur at the stress concentration point of the contoured trough.
Solution Approach 2:
The embedded portion of the anode wire acts as a preventive measure against crack propagation. By having the wire already in place spanning the vulnerable contoured trough region, the system is cushioned against the harmful effect of cracks before they can render the anode inoperable.
2Ease of manufacture
If the anode wire is straight and simply connected, then manufacturing simplicity is improved, but reliability against crack propagation deteriorates
Solution Approach 1:
The anode wire is divided into distinct functional segments: an embedded portion that spans the contoured trough, a middle portion that connects to the terminal pin, and end portions that extend into the anode pellet. This segmentation allows each part to perform its specific function - the embedded portion prevents crack propagation while the other portions maintain electrical connection.
Solution Approach 2:
The anode wire is pre-shaped with the embedded portion configured to span the contoured trough before assembly. This preliminary action of shaping the wire ensures that the reliability-enhancing feature is built into the component itself, rather than requiring complex assembly procedures or additional parts.
Data Source
AI summary
A capacitor having an anode of a pressed powder pellet is described. The pressed powder anode pellet has a contoured trough that extends inwardly into the height of the pellet from a peripheral edge of the pellet. A shaped anode wire has an embedded portion residing inside the pellet and an outwardly extending portion that is connected to the terminal pin of a feedthrough. The feedthrough is nested in the contoured trough. In order to prevent a crack from rendering the anode inoperable, the embedded portion of the anode wire is shaped to bridge the lateral extent of the contoured trough. Should a crack develop in the anode, the crack will intersect the embedded portion of the anode wire. As an embedded bridging wire structure, the crack in the anode pellet will not cause the shaped anode wire to break. Instead, the shaped anode wire provides electrical continuity from one side of the crack to the other so that the capacitor remains functional.