Solid electrolytic capacitor
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Solution Overview
Problem
Existing solid electrolytic capacitors suffer from deterioration due to oxygen and moisture intrusion through interfaces with low adhesion between the lead terminal and the exterior body.
Innovation Solution
The capacitors are designed with lead terminals featuring rough surfaces on contact areas with the exterior body, having a developed area ratio of the interface of at least 0.4, and optionally covered with copper, tin, and noble metal plating layers to enhance adhesion and prevent intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead terminal has a smooth surface for embedding in the exterior body, then the manufacturing process is simple, but the adhesion at the interface is low allowing oxygen and moisture to intrude
Solution Approach 1:
The lead terminal surface is designed with a rough structure having peaks and valleys, creating a porous-like topology that increases the embedded volume within the exterior body. This rough surface structure provides mechanical interlocking that significantly enhances adhesion and prevents oxygen and moisture intrusion at the interface.
2Reliability
If the lead terminal surface is roughened to increase adhesion, then oxygen and moisture intrusion is suppressed, but the manufacturing precision requirements increase
Solution Approach 1:
The invention specifies quantitative parameters for the rough surface structure, including a developed area ratio of at least 0.4 and specific peak-to-valley height ranges. These parameter definitions provide clear manufacturing targets and acceptance criteria, enabling precise control of the roughness characteristics while ensuring effective adhesion enhancement.
3Reliability
If the developed area ratio of the rough surface is increased to improve adhesion, then the seal against oxygen and moisture is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The invention establishes a minimum threshold for the developed area ratio (at least 0.4) to ensure adequate adhesion and sealing performance. By setting this quantitative benchmark, the invention balances the need for enhanced reliability with manufacturing feasibility, avoiding excessive surface complexity while achieving effective protection against oxygen and moisture intrusion.
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 suppresses oxygen and moisture intrusion, enhancing the long-term reliability and solder wettability of the capacitors.
Implementation Method 1
At least one contact surface selected from the group consisting of the first contact surface and the second contact surface includes a rough surface having a developed area ratio of an interface of more than or equal to 0.4
Data Source
AI summary
A solid electrolytic capacitor includes at least one capacitor element including an anode part and a cathode part, an anode lead terminal, a cathode lead terminal, and an exterior body that covers the least one capacitor element. Each of the anode lead terminal and the cathode lead terminal includes an embedded part embedded in the exterior body. The embedded part of the anode lead terminal has a first contact surface in contact with the exterior body, and the embedded part of the cathode lead terminal has a second contact surface in contact with the exterior body. At least one contact surface selected from the group consisting of the first contact surface and the second contact surface includes a rough surface having a developed area ratio of an interface of more than or equal to 0.4.