Solid Electrolytic Capacitor Silver Paste Layer Thickness Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid electrolytic capacitors with silver paste layers exhibit high equivalent series resistance (ESR) and low capacitance per unit volume due to uneven layer thickness, particularly when applied by dipping methods, which complicates the production of capacitors with both low ESR and high capacitance.
Innovation Solution
Controlling the composition and thickness of silver paste layers on an anode substrate with a carbon paste layer by using two types of silver pastes with different wettability on the side and face portions, and ensuring a water content of 0.5 mass % or less, particularly 0.3 mass % or less, to achieve a laminated structure with low ESR and high capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silver paste is applied by dipping method to cover the side (edge) part of the anode substrate, then the silver paste layer on the side part becomes thinner, but the ESR increases and capacitance per unit volume decreases
Solution Approach 1:
The patent applies different paste compositions to different regions of the anode substrate. Specifically, a first paste composition is applied to the side (edge) portions while a second paste composition is applied to the face portions. This local differentiation allows optimization of layer thickness and composition for each region, ensuring adequate coverage on sides without excessive thickness on faces, thereby maintaining low ESR and high capacitance per unit volume.
2Reliability
If silver paste is applied by brush to prevent thin portions, then the layer thickness becomes more uniform, but the capacitance per unit volume decreases due to unnecessarily thick portions
Solution Approach 1:
The patent uses different paste compositions with different properties for different regions. The first paste composition (for side portions) and second paste composition (for face portions) have different solid content ratios, vehicle compositions, or particle size distributions. This allows the side portions to achieve adequate thickness for low ESR while face portions maintain optimal thickness for high capacitance density, resolving the contradiction between uniformity and volume efficiency.
3Reliability
If the silver paste layer thickness on the side part is increased to reduce ESR, then the ESR decreases, but the element thickness increases and capacitance per unit volume decreases
Solution Approach 1:
The patent optimizes the silver paste layer thickness locally by applying a first paste composition to side portions and a second paste composition to face portions. The side portions receive sufficient thickness (optimized for low ESR) while face portions maintain thinner, more efficient layers. This spatial optimization ensures that the increased thickness for ESR reduction is confined only to where it is electrically necessary, preserving overall volume efficiency.
Solution Approach 2:
The patent employs composite paste compositions with different formulations for different regions. The first paste composition and second paste composition differ in solid content ratio, vehicle composition, or particle size distribution. These composite material variations enable region-specific optimization of electrical performance versus volume efficiency, allowing thin face layers for high density and adequately thick side layers for low ESR.
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
The approach results in a solid electrolytic capacitor with significantly reduced ESR and increased capacitance per unit volume, where the layer thickness on the side portions is adequately secured while being suppressed on the face portions, effectively addressing the challenges of uneven application and high ESR.
Implementation Method 1
These layers can be formed by dipping the anode substrate sequentially in liquid containing the component of each layer, respectively
Implementation Method 2
a silver paste layer (4b) comprising silver particles is formed on a carbon paste layer (4a) comprising carbon particles
Implementation Method 3
forming thereon a solid semiconductor layer (3) (hereinafter referred to as solid electrolyte) as a counter electrode
Data Source
AI summary
An element for a solid electrolytic capacitor having low equivalent series resistance (ESR) and high capacitance per unit volume obtained by controlling the composition or the thickness of the silver paste forming a laminated structure on the anode substrate having a carbon paste layer on the surface. Using two kinds of silver pastes each having different wettability on the carbon paste layer and applying each silver paste on the side (edge) portions and face portions of an anode substrate, respectively, a desired layer thickness can be obtained as a whole. A solid electrolytic capacitor element preferably has a silver paste layer coating the side (edge) portions of the anode substrate which is thicker than the silver paste layer covering the face portions of the anode substrate, wherein a silver paste of composition having a water amount of 0.5 mass % or less is preferably used.