Hydration Layer on Etched Anode Foil Edges
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Solution Overview
Problem
The existing methods for manufacturing high voltage capacitors for implantable medical devices, such as implantable cardioverter defibrillators, face challenges in maximizing energy density due to the brittleness and high leakage current caused by the mechanical punching process of anode foils, which results in burrs and exposed edges without high-quality oxide formation, leading to potential short circuits and reduced capacitor lifespan.
Innovation Solution
A method involving the formation of a hydration layer on etched anode foils before assembly, which includes electrochemical etching, widening, and oxidation, followed by a hydration process in water and a passivation step in ammonium dihydrogen phosphate to enhance oxide quality and reduce edge-related issues, thereby improving capacitor reliability and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical punching is used to shape anode foils, then capacitor assembly is simplified, but the anode foil becomes brittle and develops burrs causing high leakage current and potential short circuits
Solution Approach 1:
The patent applies preliminary action by forming a quality oxide layer on the anode foil edges through electrochemical etching and oxidation processes before the mechanical punching step. This pre-formed oxide layer protects the edges during subsequent punching operations, preventing burr formation and maintaining low leakage current. The hydration layer is also formed in advance to facilitate controlled oxide growth before mechanical processing occurs.
2Quantity of substance
If more aluminum is removed during etching to increase surface area, then capacitance increases, but the foil becomes more brittle and difficult to punch without cracks
Solution Approach 1:
The patent applies parameter changes by controlling the oxidation parameters (voltage, time, electrolyte composition) to form a dense, adherent oxide layer on the etched surface. This oxide layer reinforces the brittle etched structure, allowing high surface area foils to withstand mechanical punching without cracking. The hydration layer formation also modifies the physical parameters of the oxide, making it more flexible and less prone to fracture during assembly.
3Productivity
If mechanical punching is used to create anode shapes, then manufacturing efficiency increases, but exposed edges without high-quality oxide lead to short circuits
Solution Approach 1:
The patent applies preliminary action by performing electrochemical etching and oxidation to form a quality oxide layer on all surfaces including future edge areas, before the mechanical punching step. This ensures that when edges are created by punching, they already have a protective oxide layer that prevents short circuits and reduces leakage current, maintaining both high productivity and edge quality.
4Reliability
If standard oxidation is performed after punching, then edges are protected, but the process is time-consuming and oxide quality is insufficient
Solution Approach 1:
The patent applies preliminary action by forming the oxide layer on edges through electrochemical oxidation before punching, eliminating or reducing the need for post-punching oxidation steps. This preliminary oxide formation is of higher quality and reduces the subsequent aging time required, directly addressing both oxide quality and time loss concerns.
Solution Approach 2:
The patent applies parameter changes by using controlled electrochemical oxidation parameters (voltage, electrolyte composition, temperature, time) to form a dense, high-quality oxide layer rapidly before punching. This electrochemical oxidation process is faster and produces superior oxide quality compared to standard thermal oxidation performed after punching, reducing overall process time while improving reliability.
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 hydration layer formation reduces capacitor deformation, leakage current, and extends the lifespan by creating a higher quality oxide on edges, facilitating faster aging and assembly while minimizing the risk of short circuits.
Implementation Method 1
placing the removed anode foil into a bath comprising water to form a hydration layer over the exposed metal on the cut edges of the anode foil
Implementation Method 2
etched/formed aluminum anode foil is punched by use of a mechanical die into an anode shape to conform to the necessary geometry of the capacitor case. In order to obtain higher capacitance, aluminum is removed from the anode foil during an etching process to create tunnels to increase surface area
Implementation Method 3
Exposed surfaces of the etched metal foil are then oxidized
Data Source
AI summary
A capacitor and a method of processing an anode metal foil are presented. The method includes electrochemically etching the metal foil to form a plurality of tunnels. Next, the etched metal foil is disposed within a widening solution to widen the plurality of tunnels. Exposed surfaces of the etched metal foil are then oxidized. The method includes removing a section of the etched metal foil, where the section of the etched metal foil includes exposed metal along an edge. The section of the etched metal foil is placed into a bath comprising water to form a hydration layer over the exposed metal on the section of the etched metal foil. The method also includes assembling the section of the etched metal foil having the hydration layer as an anode within a capacitor.