Sonic Vibration Oxide Stressing for Aluminum Capacitor Foils
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Solution Overview
Problem
Conventional oven depolarization processes in aluminum electrolytic capacitors negatively affect foil capacitance and introduce stress cracking, limiting the energy density and reliability of high-voltage capacitors used in implantable medical devices.
Innovation Solution
Replacing the oven depolarization process with sonic vibration to stress and crack the oxide on anode foils, followed by reformation to heal fractures, which increases capacitance while managing leakage current and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oven depolarization process is used to stress and crack the oxide, then leakage current is reduced, but capacitance decreases by 5-8%
Solution Approach 1:
The patent replaces the thermal oven depolarization process with a mechanical sonic vibration process to stress and crack the oxide. The sonic vibration system uses mechanical oscillations at specific frequencies (20-20,000 Hz) to induce stress in the oxide layer, achieving the same leakage current reduction effect without the harmful thermal field that causes capacitance loss.
Solution Approach 2:
The patent changes the fundamental parameter of the stress application method from thermal (oven depolarization) to mechanical vibrational (sonic vibration). By controlling vibration frequency and duration, the process achieves oxide cracking and leakage current reduction while avoiding the capacitance degradation associated with thermal treatment.
2Reliability
If oven depolarization is used to drive off water and induce stress cracking, then oxide weak areas are exposed, but oxide growth and conversion reduce foil capacitance
Solution Approach 1:
The patent substitutes the thermal mechanism of oxide growth and conversion with a mechanical vibration mechanism. Sonic vibrations directly stress and crack the oxide through mechanical oscillations, bypassing the thermal pathways that lead to unwanted oxide growth and capacitance loss.
Solution Approach 2:
The patent applies mechanical vibration at sonic frequencies (20-20,000 Hz) to induce stress cracking in the oxide layer. This mechanical vibration method directly achieves oxide stress and cracking without requiring thermal treatment, thereby avoiding the capacitance-reducing side effects of oven depolarization.
3Quantity of substance
If high surface area foil is created through tunnel etching, then capacitance increases, but oxide deformation properties worsen
Solution Approach 1:
The patent uses mechanical vibration to stress and crack the oxide on high surface area etched foils. This method addresses the oxide deformation issues by using controlled mechanical oscillations to initiate cracking at weak points, which can then be healed through reformation, rather than relying on thermal processes that exacerbate deformation.
Solution Approach 2:
The patent employs a feedback approach where oxide stress cracking is induced by sonic vibration, then the oxide is reformed to heal the cracks, and the process is repeated. This iterative process progressively improves oxide quality and deformation properties while maintaining the high capacitance provided by the etched surface area.
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 method enhances capacitance by 5-8% and reduces deformation by over 70%, while maintaining or slightly increasing leakage current, thereby improving the energy density and reliability of capacitors.
Implementation Method 1
The foil is exposed to sonic vibration with frequencies in the range of 20 Hz to 20,000 Hz
Implementation Method 2
This formation process (also referred to as anodization or electrolysis) oxidizes the surface of the metal foil
Implementation Method 3
tunnels are often etched through the thickness of the anode metal foils. The energy density in an aluminum electrolytic capacitor is directly related to the surface area of the anodes generated in the electrochemical etching processes
Data Source
AI summary
Methods are presented that includes replacing oven depolarization of a foil with a sonic vibration process for stressing the oxide. The method includes electrochemically etching the metal foil to form a plurality of tunnels in the metal foil and forming an oxide on a surface of the metal foil. The method further includes applying sonic vibration to the metal foil to induce stress fractures in the oxide, and reforming the oxide to heal at least a portion of the stress fractures.