Anode Wire Deoxygenation for Capacitor Embrittlement
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Solution Overview
Problem
The miniaturization of solid electrolytic capacitors is hindered by the brittleness of anode wires after sintering, especially when exposed to moisture, due to hydrogen embrittlement caused by high oxygen concentration in the tantalum wire, leading to high failure rates and reduced volumetric efficiency.
Innovation Solution
A method involving deoxygenation and acid leaching of the anode wire using a reducing agent like magnesium, followed by sintering and passivation, to render the wire more ductile and resistant to moisture, allowing for the use of thinner wires with higher surface area powders, thereby increasing capacitance and reducing anode wire volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the anode wire is decreased to increase volumetric efficiency, then the capacitance per anode volume increases, but the wire becomes extremely brittle and prone to breakage after sintering and exposure to moisture
Solution Approach 1:
The anode wire undergoes deoxygenation treatment before being inserted into the anode powder and sintering. This preliminary removal of oxygen from the wire prevents subsequent hydrogen embrittlement that would occur during sintering and moisture exposure, thereby maintaining wire ductility and reliability even at reduced diameters
Solution Approach 2:
The chemical composition parameter of the anode wire is changed by removing oxygen through deoxygenation treatment. This parameter change (reducing oxygen content) fundamentally alters the wire's susceptibility to hydrogen embrittlement, enabling the use of thinner wires without sacrificing reliability
2Quantity of substance
If the charge density of the anode powder is increased to improve capacitance, then the capacitance per volume increases, but the wire brittleness increases due to higher bulk oxygen concentration in the wire
Solution Approach 1:
Deoxygenation of the anode wire is performed before sintering to remove oxygen that would otherwise be present in high concentrations during high charge density processing. This preliminary action prevents the correlation between high charge density and increased wire brittleness
Solution Approach 2:
Oxygen is extracted from the anode wire through deoxygenation treatment before the wire is inserted into the high charge density anode powder. This extraction removes the harmful element (oxygen) that would interact with high charge density conditions to cause brittleness, allowing independent optimization of both charge density and wire ductility
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 process significantly reduces anode wire failure and increases volumetric efficiency by maintaining the ductility of thin anode wires, enabling higher capacitance per anode volume while minimizing discarded parts and maintaining electrical and mechanical performance.
Implementation Method 1
A method involving deoxygenation and acid leaching of the anode wire using a reducing agent like magnesium
Implementation Method 2
A method involving deoxygenation and acid leaching of the anode wire
Implementation Method 3
The anode precursor is then sintered to form the anode
Implementation Method 4
The hydrogen, as a byproduct of this reaction, diffuses into the tantalum wire making it brittle
Implementation Method 5
the wire becomes very brittle after sintering and subsequent exposure to moisture or aqueous solutions, especially at the point of egress from the anode
Data Source
AI summary
An improved capacitor, and method of manufacturing the improved capacitor, is provided. The method includes deoxygenating and leaching the anode wire to produce a capacitor comprising an anode having a surface area of at least 4.0 m2/g or a charge density of at least 200,000 CV/g with the anode wire having an equivalent diameter of less than 0.30 mm extending from said anode. A dielectric is on the anode and a cathode is on the dielectric.