Solid Electrolytic Capacitor Silver Layer Design
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Solution Overview
Problem
The formation of ridges and valleys on the surface of the conductive polymer layer in solid electrolytic capacitors reduces the effective contact area between the silver paste layer and the conductive carbon layer, limiting the reduction of equivalent series resistance, especially during miniaturization.
Innovation Solution
A solid electrolytic capacitor design featuring a conductive polymer layer with ridges and valleys covered by a carbon layer, and a silver layer comprising both spherical silver particles and silver flakes, where the silver flakes are layered on top of the spherical particles to enhance contact area and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ridges and valleys are formed on the surface of the conductive polymer layer to increase contact area, then mechanical adhesion force between the conductive polymer layer and the conductive carbon layer is improved, but the effective contact area between the silver paste layer and the conductive carbon layer is reduced
Solution Approach 1:
The silver layer is segmented into two distinct layers: a first silver layer containing spherical silver particles that fills the valleys and contacts the conductive carbon layer, and a second silver layer containing silver flakes that provides additional contact areas on top. This segmentation allows each layer to perform its specific function - the first layer ensures good contact with the carbon layer while the second layer provides extensive contact area for current distribution.
Solution Approach 2:
The silver layer uses a composite structure combining two different forms of silver particles (spherical particles and flakes) in separate layers. The spherical particles in the first layer effectively fill the valleys and provide point contacts, while the flake-shaped particles in the second layer create extensive surface area for electrical contact, achieving both adhesion and conductivity requirements.
2Volume of moving object
If the solid electrolytic capacitor is miniaturized to reduce size, then compactness is improved, but the influence of reduced effective contact area between the silver paste layer and the conductive carbon layer is relatively increased
Solution Approach 1:
The invention transitions from a single-layer silver structure to a two-layer silver structure, adding a vertical dimension to the silver layer configuration. This dimensional change allows the capacitor to maintain low ESR performance even when miniaturized, as the layered structure maximizes contact area within the limited horizontal space available in small capacitors.
Solution Approach 2:
The invention changes the physical parameters of the silver layer by using two different particle morphologies (spherical and flake) arranged in layers. This parameter change allows the silver layer to maintain effective contact area and low equivalent series resistance even when the overall capacitor size is reduced for miniaturization applications.
3Device complexity
If a single-layer silver paste is used to simplify the structure, then device complexity is reduced, but the equivalent series resistance cannot be sufficiently reduced
Solution Approach 1:
The silver layer is divided into two functional segments: the first silver layer with spherical particles that ensures good contact with the conductive carbon layer, and the second silver layer with flake particles that provides extensive contact area. This segmentation resolves the contradiction by achieving low ESR through the combined effect of both layers while maintaining a relatively simple overall structure that can be applied to existing manufacturing processes.
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 reduces the equivalent series resistance and enhances heat resistance reliability by increasing the contact area and adhesion strength between the conductive polymer layer and the cathode layer, while maintaining reliability under high temperature and reflow conditions.
Implementation Method 1
The silver layer includes a first silver layer, which is arranged on the carbon layer covering the ridges and valleys and mainly contains spherical silver particles. The silver layer further includes a second silver layer, which is arranged on the first silver layer and mainly contains silver flakes.
Implementation Method 2
The ridges and valleys on the surface of the conductive polymer layer formed by mixing powder, such as graphite powder, increases contact area in the interface between the conductive polymer layer and the conductive carbon layer.
Data Source
AI summary
A solid electrolytic capacitor including an anode body, a dielectric layer arranged on the anode body, a conductive polymer layer arranged on the dielectric layer, and a cathode layer including a carbon layer arranged on the conductive polymer layer and a silver layer arranged on the carbon layer. The conductive polymer layer includes ridges and valleys formed in a surface that faces toward the cathode layer. The silver layer includes a first silver layer, which is arranged on the carbon layer, covers the ridges and valleys, and mainly contains spherical silver particles, and a second silver layer, which is arranged on the first silver layer and mainly contains silver flakes.