Cuboid Silver Powder for Fine-Line Conductive Paste Reliability
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Solution Overview
Problem
Existing conductive pastes using spherical and flake-like silver powders face issues with increased line resistance and disconnection rates during fine line printing.
Innovation Solution
A cuboid silver powder with a BET specific surface area of 0.5 m2/g or less, an average aspect ratio of 1.2 or greater and less than 2.0, and specific perimeter and circularity coefficients is developed, along with a method for producing this powder without a lubricant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spherical silver powder is used for conductive paste, then the paste can be easily manufactured, but line resistance increases and disconnection rate increases during fine line printing
Solution Approach 1:
The invention changes the shape parameter of silver powder from spherical to cuboid form. This shape modification improves the filling density and contact between particles in the conductive paste, thereby reducing line resistance and disconnection rate while maintaining ease of manufacture through controlled crystallization or mechanical processing methods
2Shape
If flake-like silver powder is used for conductive paste, then the aspect ratio is increased, but line resistance increases and disconnection rate increases during fine line printing
Solution Approach 1:
The invention optimizes the shape parameters by creating cuboid silver powder with controlled aspect ratio (1.05-1.30) and specific dimensional ratios (length-to-width ratio of 1.10-1.20, width-to-thickness ratio of 1.05-1.25). This controlled shape modification improves particle packing and contact without causing the line resistance and disconnection issues associated with flake-like structures
Solution Approach 2:
The invention introduces controlled asymmetry in the form of cuboid particles with specific dimensional relationships rather than perfect spheres or flat flakes. The cuboid shape with optimized aspect ratios creates better interparticle contact and filling density, improving electrical conductivity while maintaining manufacturing feasibility
3Quantity of substance
If the aspect ratio of silver powder is increased to improve filling density, then the disconnection rate increases during fine line printing
Solution Approach 1:
The invention optimizes the aspect ratio parameter to a specific range (1.05-1.30) that balances filling density improvement with disconnection prevention. The cuboid shape with controlled dimensions achieves better particle packing without creating the structural weaknesses that lead to disconnection in fine line applications
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 cuboid silver powder effectively reduces line resistance and disconnection rates in conductive pastes, enabling the formation of electric wiring with improved performance.
Implementation Method 1
allowing the spherical silver powder and the media to collide with each other by motions of the container
Data Source
AI summary
There is provided a cuboid silver powder including silver particles having a BET specific surface area of 0.5 m2/g or less. An average aspect ratio of the cuboid silver powder is 1.2 or greater and less than 2.0 as determined by observing cross-sections of 100 or more silver particles from the silver particles. An average of a ratio represented by (Formula 1) below is 0.84 or greater. The ratio is a ratio of perimeter of one silver particle among the silver particles to perimeter of a rectangle circumscribing the one silver particle.L/(2×major axis+2×minor axis) (Formula 1):where L is the perimeter (μm) of the one silver particle, and the major axis and minor axis are respectively a long side (μm) and short side (μm) of the rectangle of minimum area circumscribing an outline of cross-section of the one silver particle.