Silver Paste Layer Thickness and Composition for Low ESR Solid Capacitors
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Solution Overview
Problem
Conventional solid electrolytic capacitors face challenges in reducing thickness while maintaining low equivalent series resistance (ESR) and leakage current (LC), as reducing the cathode electrode thickness increases ESR and using a carbon paste layer can lead to increased leakage current due to silver migration.
Innovation Solution
A solid electrolytic capacitor element with a specific composition and thickness of silver and carbon paste layers, where the silver paste layer is between 5 to 20 μm thick and contains 84 to 94% silver, and the carbon paste layer is 1 to 8 μm thick with 50 to 80% carbon, using silver particles of 1 to 5 μm and carbon particles of 300 nm or less, and incorporating fluorine or polyester resin for improved wettability and reduced ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the cathode electrode thickness is reduced to meet the demand for thinner capacitors, then the capacitor thickness is reduced, but the equivalent series resistance (ESR) increases
Solution Approach 1:
The invention changes the composition parameters of the conductor layer by specifying a silver content of 84-94% and controlled thickness of 5-20 μm, which optimizes the balance between reducing overall capacitor thickness and maintaining low ESR performance
Solution Approach 2:
The conductor layer uses a composite structure combining silver paste (for low resistance) with carbon paste layer (for silver migration prevention), creating a multi-material system that simultaneously achieves low ESR and high reliability
2Reliability
If a carbon paste layer is used in the conductor layer, then silver migration is suppressed, but leakage current increases due to silver migration through the carbon paste
Solution Approach 1:
The invention optimizes the carbon paste layer thickness to 1-8 μm and silver paste layer thickness to 5-20 μm, creating a controlled structure where silver is contained within the carbon layer without excessive thickness that would cause migration pathways
Solution Approach 2:
The conductor layer structure assigns different functions to different layers: the carbon paste layer locally suppresses silver migration at the interface, while the silver paste layer provides bulk conductivity, creating a functionally differentiated structure
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 achieves reduced thickness, lower ESR, and lower LC, enhancing the overall properties of the solid electrolytic capacitor by optimizing the layer thickness and composition.
Implementation Method 1
a silver paste layer... contained in the silver paste layer is within a range of 84 to 94%
Implementation Method 2
a carbon paste layer... to suppress the equivalent series resistance (ESR) to a low level, it is desirable to reduce resistance of a cathode electrode including a conductor layer
Data Source
AI summary
The invention provides a solid electrolytic capacitor element, comprising a metal oxide layer, an electroconductive polymer layer, a carbon paste layer and a silver paste layer sequentially formed on surface of a valve-acting metal material, wherein thickness of the silver paste layer is within a range of 5 to 20 μm and the mass ratio of silver contained in the silver paste layer is within a range of 84 to 94%. According to the invention, a solid electrolytic capacitor having good electric properties such as ESR (equivalent series resistance) and LC (leakage current) and good reliability can be produced.