Recessed Lead Frame Structure in Solid Electrolytic Capacitors
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Solution Overview
Problem
Solid electrolytic capacitors deteriorate due to exposure to oxygen and moisture, despite being covered with an exterior body, as these substances can still penetrate and affect the electrolyte layer, leading to reliability issues and potential short circuits from metal migration.
Innovation Solution
The capacitors incorporate an anode and cathode lead frame with buried parts that have recesses on their surfaces, which are covered with an insulating film, increasing the penetration path for oxygen and moisture and enhancing adhesion, thereby preventing electrolyte layer deterioration and metal migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitor element is covered with an exterior body, then the capacitor is protected from external damage, but oxygen and moisture can still penetrate through various paths and cause electrolyte layer deterioration
Solution Approach 1:
The exterior body is segmented into multiple layers: a base exterior body and an additional insulating film layer. This segmentation creates multiple barrier paths that oxygen and moisture must penetrate, significantly reducing their ability to reach the electrolyte layer compared to a single-layer structure.
Solution Approach 2:
An insulating film is introduced as an intermediary layer between the exterior body and the capacitor element. This intermediate layer specifically targets and blocks the harmful penetration paths of oxygen and moisture that bypass the conventional exterior body, without interfering with the electrical functionality of the capacitor.
2Reliability
If recesses are formed on the surface of the buried part to increase penetration path, then adhesion is enhanced and protection is improved, but manufacturing complexity increases
Solution Approach 1:
The recesses are formed with curved, hemispherical bottoms rather than sharp corners or flat bottoms. This curvature serves multiple functions: it increases the surface area for adhesion, creates longer penetration paths for oxygen and moisture, and can be efficiently manufactured using standard laser processing or mold techniques, balancing protection enhancement with manufacturing feasibility.
Solution Approach 2:
The buried part surface is transformed from a flat solid surface to a porous-like structure with multiple recesses. This increases the effective surface area for adhesion and creates tortuous paths that block the diffusion of oxygen and moisture, achieving enhanced protection without requiring completely new manufacturing processes.
3Reliability
If an insulating film is added to cover the buried part and recesses, then protection against oxygen and moisture is enhanced, but the device structure becomes more complex
Solution Approach 1:
The insulating film serves multiple functions simultaneously: it provides electrical insulation, acts as a barrier against oxygen and moisture penetration, and enhances adhesion to the recessed surface of the buried part. This multi-functionality justifies the additional structural element by delivering multiple benefits from a single added component.
Solution Approach 2:
A thin insulating film is used to provide comprehensive protection against oxygen and moisture penetration. The thin-film approach maintains structural simplicity while effectively blocking harmful substances, as the film conforms to the recessed surface geometry without requiring thick or rigid protective structures.
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 configuration significantly enhances the reliability of solid electrolytic capacitors by reducing the impact of oxygen and moisture on the electrolyte layer and preventing metal migration, resulting in improved performance stability.
Implementation Method 1
an insulating film covering at least one selected from the group consisting of at least a part of the anode part and at least one of the plurality of first recesses... increasing the penetration path for oxygen and moisture
Implementation Method 2
A plurality of recesses are formed on a surface of at least one of the first buried part or the second buried part... increasing the penetration path for oxygen and moisture
Data Source
AI summary
A solid electrolytic capacitor includes a capacitor element, an anode lead frame, a cathode lead frame, and an exterior body. The anode lead frame includes a first buried part that is a part of the anode lead frame and is buried in the exterior body. The cathode lead frame includes a second buried part that is a part of the cathode lead frame and is buried in the exterior body. A plurality of recesses are formed on a surface of at least one of the first buried part or the second buried part. The plurality of recesses include a plurality of first recesses formed on a surface of the first buried part. The solid electrolytic capacitor further includes an insulating film disposed to cover at least one selected from the group consisting of at least a part of the anode part and at least one of the plurality of first recesses.