Silver Powder Coating for Conductive Paste Levelling
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Solution Overview
Problem
Conductive pastes used in electronic components face challenges in achieving fine line resolution due to poor compatibility between silver powder and organic vehicle, leading to issues with levelling and dispersion, and existing methods either compromise on productivity or result in insufficient line thickness.
Innovation Solution
A silver powder with an organic substance containing at least one carboxyl and one hydroxyl group is used, produced through a wet reduction method, ensuring a BET specific surface area of 0.1-2.0 m2/g and particle size distribution of 0.1-6.0 μm, enhancing compatibility and levelling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the filler concentration in the conductive paste is reduced to improve levelling property, then the levelling property is improved, but the viscosity of the conductive paste is reduced making it difficult to draw fine wired lines
Solution Approach 1:
The patent changes the chemical composition parameters of the organic substance coating on silver powder particles by specifying that it contains both a carboxyl group and a hydroxyl group. This dual-functional group combination modifies the surface properties of the silver powder, enabling improved levelling property while maintaining appropriate viscosity for fine line drawing, thus resolving the contradiction without requiring filler concentration reduction
2Reliability
If nano-size particles with high BET specific surface area are used to improve compatibility, then compatibility is improved, but it becomes difficult to increase silver concentration ensuring sufficient wired line thickness
Solution Approach 1:
The patent optimizes the BET specific surface area parameter to a moderate range of 0.5-2.0 m²/g, avoiding both extremely fine nano-size particles (which would require excessive organic vehicle) and coarse particles (which would reduce compatibility). This parameter optimization enables achieving good compatibility while maintaining high silver concentration for sufficient wired line thickness
Solution Approach 2:
The patent creates a composite structure where silver powder particles are coated with an organic substance containing both carboxyl and hydroxyl groups. This composite coating structure improves compatibility with the organic vehicle while the controlled particle size ensures adequate silver concentration, resolving the contradiction between compatibility and silver concentration
3Reliability
If the organic substance on particle surfaces is substituted to improve compatibility, then compatibility is improved, but the number of working steps is considerably increased leading to significant drop in productivity
Solution Approach 1:
The patent incorporates the desired organic substance coating containing both carboxyl and hydroxyl groups directly into the silver powder production process itself, rather than applying it as a separate post-treatment step. This preliminary action integrates the compatibility-improving function into the base material production, avoiding additional working steps and maintaining high productivity
Solution Approach 2:
The patent merges the functions of achieving both carboxyl and hydroxyl groups in the organic substance coating into a single integrated production process, rather than requiring separate substitution steps for each functional group. This merging of functions into one process maintains productivity while achieving the desired compatibility
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 solution provides a conductive paste with improved levelling and dispersion properties, enabling the formation of stable fine lines and increasing silver concentration, thus addressing the limitations of existing methods.
Implementation Method 1
adding a reducing agent to an aqueous reaction system containing silver ions to deposit spherical silver powder through reduction
Implementation Method 2
an organic substance on a surface of the silver powder
Data Source
AI summary
A silver powder, including: an organic substance on a surface of the silver powder, the organic substance containing at least one carboxyl group and at least one hydroxyl group in one molecule of the organic substance, wherein a BET specific surface area of the silver powder is 0.1 m2/g or more but 2.0 m2/g or less, and wherein a cumulative 50% point of particle diameter (D50) of the silver powder in a volume-based particle size distribution of the silver powder as measured by a laser diffraction particle size distribution analysis is 0.1 μm or more but 6.0 μm or less, and a ratio of [(D90−D10)/D50] is 3.0 or less, where D50 is the cumulative 50% point of particle diameter, D90 is a cumulative 90% point of particle diameter of the silver powder, and D10 is a cumulative 10% point of particle diameter of the silver powder.