Hermetically Sealed Electrolytic Capacitor Double Case Design
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Solution Overview
Problem
Electrolytic capacitors face reduced service life and seal failure at high operating temperatures due to electrolyte drying, increased pressure, and component damage, leading to corrosion and performance degradation.
Innovation Solution
A hermetically sealed electrolytic capacitor design featuring an inner case with a gasket-sealed opening and an outer case that resists expansion, using a high-modulus polymer spacer and metal-glass-metal hermetic seals to prevent leakage and distortion, with components capable of operating at temperatures up to 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hermetic seal is provided in a single-case electrolytic capacitor, then corrosion and electrolyte leakage are prevented, but the capacitor fails at high temperatures due to internal pressure buildup and seal degradation
Solution Approach 1:
The capacitor is divided into two separate cases: an inner case containing the capacitor element and electrolyte, and an outer case providing hermetic sealing. This segmentation allows the inner case to accommodate pressure changes while the outer case maintains the hermetic seal, resolving the contradiction between seal integrity and pressure resistance at high temperatures.
Solution Approach 2:
A spacer is introduced as an intermediary component between the inner and outer cases. This spacer provides electrical insulation and mechanical spacing, allowing the inner case to expand or contract independently while maintaining the hermetic seal integrity of the outer case, thus preventing seal failure under thermal stress.
2Loss of substance
If the inner case is sealed with a gasket, then electrolyte leakage is prevented, but the cap may move outward under pressure buildup
Solution Approach 1:
The gasket is integrated with the cap structure to form a unified sealing assembly. This merging ensures that the gasket and cap work together as a single unit, maintaining both the electrolyte seal and structural stability under pressure, preventing cap displacement while preserving leak prevention.
3Ease of manufacture
If conventional paper spacers are used between capacitor foils, then component assembly is simple, but the spacers degrade at high temperatures leading to element failure
Solution Approach 1:
The spacer material parameter is changed from conventional paper to high-temperature resistant material such as polyimide or aramid. This parameter change enables the spacer to maintain its mechanical properties and electrical insulation capabilities at elevated temperatures up to 200°C, ensuring element integrity while preserving manufacturing simplicity.
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 extends the service life of electrolytic capacitors to 2,000 hours or more at 175°C and 200°C by preventing seal failure and performance degradation, ensuring reliable operation under high temperature conditions.
Implementation Method 1
The seal created by the gasket prevents the electrolyte from leaking or outgassing
Implementation Method 2
an outer case, which incorporates a hermetic seal and resists outward expansion of the inner capacitor, thereby preventing seal failure and performance degradation
Data Source
AI summary
An electrolytic capacitor is provided having an inner case housing a capacitor element and an electrolyte, which is sealed by an inner cap insulated from the body of the inner case by a gasket, with the anode terminal of the capacitor element connected to the inside face of the inner cap and an anode lead connected to the outside face of the inner cap. The inner case is placed in an outer case having a sleeve surrounding the body of the inner case and an outer cap with a hermetic seal overlaying the inner cap. An insulating spacer is positioned between the inner cap and the outer cap, whereby the spacer resists movement of the inner cap, thereby preventing outward expansion of the inner case, which otherwise might lead to failure, especially at relatively high operating temperatures.