Silver Paste Composition for Printability and Dense Conductor Films
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Solution Overview
Problem
Existing electrically conductive pastes face a trade-off between achieving high electrical conductivity and maintaining good printability, with dense coating films often sacrificing printability and vice versa. Additionally, high silver powder content is necessary for conductivity but can lead to migration issues.
Innovation Solution
A silver paste with a high silver powder concentration is developed, where the specific surface area of the silver powder and the content percentage of the binder resin are controlled within specific ranges (CBND/SBET = 2.00 to 3.40) to achieve high film density and printability. The silver powder also contains a minimum necessary amount of copper to inhibit migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of metal powder is increased to obtain high electrical conductivity, then electrical conductivity is improved, but printability is deteriorated
Solution Approach 1:
The patent applies parameter changes by precisely controlling the specific surface area of silver powder (0.05-0.50 m²/g) and the binder resin content (5-20 wt%) to optimize the balance between printability and electrical conductivity. This quantitative parameter control allows the paste to maintain good printability while achieving high film density and conductivity.
Solution Approach 2:
The patent uses composite materials by combining silver powder with specific binder resins and organic solvents in optimized ratios. The composite paste formulation enables simultaneous achievement of good printability, high film density, and excellent electrical conductivity, resolving the trade-off between these properties.
2Reliability
If a dense coating film is obtained to attain high electrical conductivity, then electrical conductivity is improved, but printability is sacrificed
Solution Approach 1:
The patent achieves this resolution by changing parameters including the specific surface area of silver powder (0.05-0.50 m²/g) and binder resin content (5-20 wt%). These parameter optimizations enable the formation of dense coating films with high electrical conductivity while maintaining good printability through controlled paste rheology.
3Volume of stationary object
If the amount of small size silver powder is increased to improve film density, then film density is improved, but migration more easily occurs
Solution Approach 1:
The patent resolves this contradiction by optimizing the specific surface area parameter of silver powder (0.05-0.50 m²/g), which corresponds to controlled particle size distribution. This parameter optimization achieves high film density while preventing excessive migration by avoiding overly fine particles that would be prone to migration.
Data Source
AI summary
The present invention provides a silver paste containing at least a silver powder, a binder resin, and an organic solvent, in which a value CBND/SBET is 2.0 to 3.4 where SBET (m2/g) represents a specific surface area of the silver powder, and CBND (% by mass) represents a content percentage of the binder resin based on the silver powder, a copper content of the silver powder is 10 to 5000 ppm by mass, and the silver paste has a dry film density of 7.50 g/cm3 or more. The present invention can provide a silver paste containing a powder in a high concentration and excellent in printability, and accordingly provide a silver conductor film that has a high filling factor and a high film density, exhibits high electrical conductivity, and is excellent in migration resistance.