Electrolytic Capacitor Cathode Lead-out Layer ESR Reduction
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Solution Overview
Problem
Existing electrolytic capacitors face challenges in reducing equivalent series resistance (ESR) due to high contact resistance between the silver paste layer and the carbon layer, which is not adequately addressed by previous improvements in silver paste layers.
Innovation Solution
The electrolytic capacitor design incorporates a cathode lead-out layer with a carbon layer, a first metal layer containing high-volume metal particles with minimal binder resin, and a second metal layer with larger particles and binder resin, which reduces contact resistance and enhances adhesion, thereby lowering ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silver paste layer with binder resin is used to ensure adhesion, then adhesion is improved, but contact resistance increases and ESR cannot be reduced
Solution Approach 1:
The cathode lead-out layer is segmented into multiple functional layers: a first metal layer (silver) for low contact resistance, a second metal layer (aluminum) for adhesion and ESR reduction, and an optional third metal layer for additional adhesion. This segmentation allows each layer to perform its specific function optimally without the trade-off present in single-layer designs.
Solution Approach 2:
Different metal layers are applied to different regions of the carbon layer. The first metal layer is applied to the central region where low contact resistance is critical, while the second metal layer is applied to peripheral regions where adhesion is more important. This local differentiation resolves the contradiction between adhesion and contact resistance.
2Reliability
If a single metal layer is used to reduce ESR, then contact resistance is reduced, but adhesion deteriorates and peeling occurs
Solution Approach 1:
The cathode lead-out layer uses a composite structure of multiple metal layers (silver, aluminum, and optionally other metals) with different properties. The silver layer provides low contact resistance while the aluminum layer provides adhesion, creating a composite material system that achieves both low ESR and strong adhesion simultaneously.
3Strength
If binder resin is added to metal paste to improve adhesion, then adhesion is enhanced, but ESR increases due to higher contact resistance
Solution Approach 1:
The invention extracts and removes the binder resin from the metal paste formulation. By using pure metal particles without binder resin, the paste achieves both low contact resistance (low ESR) and sufficient adhesion through the multi-layer structure, eliminating the need for binder resin and its associated trade-offs.
Data Source
AI summary
An electrolytic capacitor includes a capacitor element having: an anode; a dielectric layer covering at least a part of the anode body; a solid electrolyte layer covering at least a part of the dielectric layer; and a cathode lead-out layer covering at least a part of the solid electrolyte layer. The cathode lead-out layer includes a carbon layer covering at least a part of the solid electrolyte layer, a first metal layer covering at least a part of the carbon layer, and a second metal layer covering at least a part of the first metal layer. The first metal layer contains first metal particle, and the second metal layer contains second metal particles and a second binder resin. The first metal layer contains no binder resin, or contains a first binder resin in a volume ratio smaller than a volume ratio of the second binder resin contained in the second metal layer.