Hermetic Capacitor Packaging with Conformal Coatings
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Solution Overview
Problem
Existing methods for hermetically sealing solid electrolytic capacitors result in low volumetric efficiency due to the occupation of significant volume by non-contributory components like ceramic housings and polymeric resins, and the close approach of anodic and cathodic components poses mounting issues.
Innovation Solution
A method involving a conformal non-conductive hermetic encasement with a conformal metal coating that hermetically seals the anode wire and dielectric, using a conformal non-conductive layer to minimize volume occupation and prevent electrical contact between the anode and cathode, while maintaining a hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic housing is used for hermetic sealing, then hermetic sealing is achieved, but volumetric efficiency decreases due to the housing occupying significant volume without contributing capacitance
Solution Approach 1:
The patent removes the separate ceramic housing structure from the capacitor design. Instead of enclosing the capacitor in a distinct housing, the hermetic sealing is achieved through a conformal coating applied directly to the capacitor body, eliminating the extra volume occupied by a separate housing structure.
Solution Approach 2:
The hermetic sealing function is merged with the capacitor body itself through a conformal coating that directly encapsulates the capacitor components. This integration eliminates the need for a separate housing and reduces the overall volume while maintaining hermetic sealing.
2Reliability
If polymeric resin is used to encase the capacitor, then hermetic sealing is achieved, but volumetric efficiency decreases as the resin occupies additional space without contribution to capacitance
Solution Approach 1:
The patent eliminates the polymeric resin encapsulation layer from the capacitor structure. The hermetic sealing is achieved through alternative means (conformal coating) that do not require the additional volume of polymeric resin.
Solution Approach 2:
The patent uses a thin conformal coating instead of thick polymeric resin encapsulation. This thin film approach provides hermetic sealing while occupying minimal volume, in contrast to the bulky polymeric resin encasement.
3Ease of operation
If the anode lead wire extends axially from the anode to the lead frame, then electrical connection is achieved, but volumetric efficiency decreases as the wire occupies significant non-contributory volume
Solution Approach 1:
The patent transitions the anode lead wire from an axial extension (one-dimensional linear path) to a planar configuration integrated within the capacitor body. This dimensional change allows the lead wire to occupy less volume while maintaining electrical connection functionality.
4Reliability
If the entirety of the capacitor body is conductive, then hermetic sealing is achieved, but mounting issues arise due to electrical isolation requirements
Solution Approach 1:
The patent applies local quality by making only specific portions of the capacitor body conductive rather than the entire body. This selective conductivity is achieved through conformal metal coating applied to specific areas, providing hermetic sealing and electrical functionality while avoiding mounting issues associated with fully conductive bodies.
Data Source
AI summary
An improved method of forming a capacitor, and capacitor formed thereby, is described. The method comprises forming an anode with an anode lead extending therefrom, forming a dielectric on the anode, forming a solid cathode layer on the dielectric and forming a hermetic encasement on the capacitor wherein the hermetic encasement comprises a conformal non-conductive layer.