Solid Electrolytic Capacitor Resin Stress Buffering
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Solution Overview
Problem
Solid electrolytic capacitors using conductive polymers as electrolyte layers face increased leakage current due to stress transmission through the anode lead and electrolyte layer during outer package formation, which existing techniques fail to adequately address.
Innovation Solution
A solid electrolytic capacitor design where a first resin part covers part of the anode lead extending from the electrolyte layer to the anode terminal, and a second resin part covers the capacitor element, distributing resin injection pressure and reducing stress on the anode body, with a preferred silicone resin for the first resin part to enhance stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conductive polymer is used as an electrolyte layer to reduce ESR, then the equivalent series resistance is reduced, but the leakage current increases due to stress transmission through the anode lead and electrolyte layer during outer package formation
Solution Approach 1:
The resin covering structure is divided into two segments: a first resin part covering the anode lead and a second resin part covering the capacitor element. This segmentation allows the first resin part to specifically buffer stress on the anode lead while the second resin part provides overall protection, thereby reducing stress transmission to the dielectric layer and electrolyte layer during outer package formation.
Solution Approach 2:
The first resin part acts as an intermediary between the anode lead and the outer package structure. It absorbs and distributes the resin injection pressure, preventing direct stress transmission through the anode lead and electrolyte layer to the dielectric layer, thus reducing leakage current while maintaining the low ESR benefit of conductive polymer electrolytes.
2Strength
If resin molding is applied to form an outer package, then mechanical protection is provided, but resin injection pressure damages the dielectric layer and increases leakage current
Solution Approach 1:
The first resin part is applied beforehand to cover the anode lead and exposed electrolyte layer before the outer package formation. This creates a cushioning layer that absorbs and distributes the resin injection pressure during molding, preventing direct damage to the dielectric layer and reducing leakage current while still providing the mechanical protection benefits of resin molding.
3Ease of manufacture
If the anode lead is mechanically fixed only through embedding in the anode body, then assembly is simplified, but stress during outer package formation is transmitted through the anode lead to damage the dielectric layer
Solution Approach 1:
The first resin part is selectively applied only to cover the anode lead and exposed electrolyte layer, providing localized stress buffering where needed. This maintains the simplicity of the overall assembly process while specifically addressing the stress transmission problem at the critical anode lead location, reducing leakage current without complicating manufacturing.
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
Significantly reduces leakage current by distributing resin injection pressure and relaxing stress on the anode body, achieving a leakage current reduction of up to 1/10 compared to capacitors without this design.
Implementation Method 1
an anode made of a valve metal is anodized in an aqueous solution of phosphoric acid to form a metal oxide layer serving as a dielectric on the surface of the anode
Implementation Method 2
a first resin part is provided to cover a part of the anode lead extending from the exposed face of the electrolyte layer of the capacitor element to the anode terminal... to relax the resin injection pressure and thereby reduce the damage to the dielectric layer
Data Source
AI summary
An object of the present invention is to provide a solid electrolytic capacitor having reduced leakage current and a manufacturing method thereof. The solid electrolytic capacitor of the present invention includes a capacitor element including: an anode 3 composed of a sintered body of metal particles; an anode lead 2 provided so that one end thereof is embedded in the anode 3; a dielectric layer 4 formed on the surface of the anode 3; an electrolyte layer 5 formed on the dielectric layer 4; and a cathode layer 6 formed on the electrolyte layer 5 so that an exposed face 50 of the electrolyte layer 5 exists around the anode lead 2, wherein an anode terminal 1 electrically connected to the other end of the anode lead 2 and a cathode terminal 7 electrically connected to the cathode layer 6 are attached to the capacitor element, and a first resin part 10 is provided to cover a part of the anode lead 2 extending from the exposed face 50 of the electrolyte layer 5 of the capacitor element to the anode terminal 1, and a second resin part 8 is provided to cover at least the above capacitor element and the first resin part 10.