Solid Electrolytic Capacitor Anode Lead Rounded Corners
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Solution Overview
Problem
Solid electrolytic capacitors experience cracks at the boundary between the anode element and anode lead member due to thermal stress, leading to increased leak current and reduced performance.
Innovation Solution
The anode lead member is designed with a base end having a cross-sectional contour with rounded rectangular corners, reducing thermal stress concentration during cooling, and is manufactured by rolling a conductive metal wire between rollers to embed the base end into a sintered body of valve-action metal powder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the anode lead member has a rectangular cross-section with sharp corners, then the joint area between the anode lead member and anode element is maximized, but thermal stress concentrates at the corners causing cracks during cooling
Solution Approach 1:
The patent applies curvature by rounding the corners of the anode lead member's cross-section. Instead of sharp rectangular corners that concentrate stress, the corners are formed with a specified radius of curvature (R1 and R2). This curvature redistributes the thermal stress during cooling, preventing crack initiation while maintaining a large joint area with the anode element.
2Ease of operation
If the anode element and anode lead member are made of the same material, then material compatibility is improved, but density differences still cause differential thermal contraction and stress concentration
Solution Approach 1:
Even when using the same material for both anode element and anode lead member, density variations cause differential thermal contraction. The rounded corner design with specified radii (R1 and R2) mitigates the stress concentration that arises from this differential contraction, preventing cracks despite the inherent material compatibility.
3Productivity
If the anode lead member is cooled rapidly after sintering, then manufacturing efficiency is improved, but thermal stress increases causing cracks at the boundary
Solution Approach 1:
The rounded corner geometry with controlled radii (R1 and R2) allows for more aggressive cooling rates by eliminating stress concentration points. This enables faster cooling that improves manufacturing efficiency while the curved transitions prevent crack formation that would otherwise occur at sharp corners during rapid thermal contraction.
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
This design effectively prevents cracks in the anode element, reducing leak current and improving the yield and reliability of solid electrolytic capacitors.
Implementation Method 1
The anode element 31 having the anode lead member 26 projected therefrom as shown in FIG. 10 is prepared by vacuum-sintering a molding of the valve-action metal powder having the base end of the anode lead member 26 embedded therein.
Implementation Method 2
vacuum-sintering a molding of the valve-action metal powder
Implementation Method 3
the anode element 31 can have a smaller density than the anode lead member 26, such that the anode element 31 can have a larger linear expansion coefficient than the anode lead member 26 due to the difference in density between the anode element 31 and the anode lead member 26. This causes the anode element 31 to contract more greatly than the anode lead member 26 when the anode element 31 is cooled after the molding of the valve-action metal powder is vacuum-sintered
Implementation Method 4
a dielectric coating 33 made by oxidizing the anode element surface
Data Source
AI summary
A solid electrolytic capacitor of the present invention includes an anode element made of a sintered body of a valve-action metal; a dielectric coating, a solid electrolyte layer, and a cathode lead layer, sequentially formed on a surface of the anode element; and an anode lead member made of a conductive metal projecting from the anode element, the anode lead member having a base end thereof embedded in the anode element, the base end being formed such that a cross section thereof perpendicular to a direction extending inwardly of the anode element has a contour with four rounded rectangular corners.