Electrolytic Capacitor Sealing Structure for Low-ESR Reliability
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Solution Overview
Problem
The package body of electrolytic capacitors often fails to maintain close contact with the anode leading part, allowing air (oxygen and water) to enter, which reduces the reliability by increasing equivalent series resistance (ESR).
Innovation Solution
The electrolytic capacitor design includes a porous surface on the cathode forming part and a non-porous surface on the anode leading part, with the anode leading part being exposed from the package body to establish a direct contact with the external electrode, and optionally using an insulating member or spacers to enhance sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the package body is formed using injection molding technique, then the manufacturing process is simple and efficient, but the package body fails to maintain close contact with the anode leading part, allowing air to enter
Solution Approach 1:
The anode leading part is segmented into two distinct surface regions: a first surface region with a first roughness (Ra1) and a second surface region with a second roughness (Ra2) where Ra2 > Ra1. This segmentation allows different portions of the same component to serve different sealing functions, enabling the package body to maintain close contact with both regions while using a simple injection molding process.
Solution Approach 2:
Different surface roughness qualities are applied to different local regions of the anode leading part. The first surface region has a smoother finish (lower Ra1) while the second surface region has a rougher finish (higher Ra2). This local quality differentiation optimizes sealing performance at each interface with the package body, preventing air entry while maintaining manufacturing simplicity.
2Manufacturing precision
If the anode leading part surface is made smooth, then the manufacturing precision is high, but the package body cannot maintain close contact and air can enter
Solution Approach 1:
The anode leading part features locally differentiated surface roughness: a first surface region with controlled smoothness (Ra1) and a second surface region with increased roughness (Ra2 > Ra1). This local quality variation ensures that the smoother region maintains manufacturing precision while the rougher region enhances mechanical interlocking with the package body, preventing air entry.
Solution Approach 2:
The surface of the anode leading part is segmented into functional zones with different roughness characteristics. This segmentation allows the component to simultaneously achieve high manufacturing precision in the first region and superior sealing performance in the second region, resolving the contradiction between smooth surfaces and close contact.
3Device complexity
If air enters the electrolytic capacitor through the boundary interface, then the structure remains simple, but the solid electrolyte layer deteriorates and ESR increases
Solution Approach 1:
By applying different surface roughness qualities to different regions of the anode leading part, the invention creates enhanced sealing interfaces without adding complex structural elements. The rougher second surface region (Ra2 > Ra1) provides better mechanical interlocking with the package body, preventing air entry and protecting the solid electrolyte layer while maintaining overall structural simplicity.
Solution Approach 2:
The anode leading part surface is segmented into functional zones that provide different sealing characteristics. This segmentation prevents air entry at the package body interface, thereby protecting the solid electrolyte layer from deterioration and preventing ESR increase, all while keeping the device structure simple and avoiding additional protective components.
Data Source
AI summary
To provide an electrolytic capacitor with improved reliability. The electrolytic capacitor including: at least one capacitor element including an anode foil having a first part including a first end, and a second part including a second end, a dielectric layer formed on at least a surface of the second part, and a cathode part covering at least part of the dielectric layer; a package body enclosing the capacitor element; and an external electrode. At least a surface of the second part has a porous portion, and at least an end face of the first end is exposed from the package body and is in contact with the external electrode.