Silver Powder Pore Control for Low-Resistance Conductive Paste
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Solution Overview
Problem
Silver powders with large closed pores in existing technologies result in higher resistance in electrode wirings due to residual substances, which are not effectively removed during firing, hindering the formation of fine and low-resistance conductive patterns in electronic components.
Innovation Solution
Silver powder with a controlled pore size distribution, where the average number of pores greater than 200 nm is less than 0.01 pores/μm² at 10,000 magnification and greater than 10 nm but less than 30 nm is 25 pores/μm² at 40,000 magnification, and a porosity of 1-4%, produced by maintaining a liquid temperature below 33°C during the reduction process, ensuring low thermal weight loss and improved conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If silver powder with large closed pores is used, then firing can be performed at low temperatures, but the resistance of electrode wirings becomes higher due to large spaces remaining after firing
Solution Approach 1:
The invention segments the pore structure into two distinct size ranges: small pores (10-30 nm) that fill completely during firing, and large pores (>200 nm) that are minimized or eliminated. This segmentation allows different pore sizes to serve different functions - small pores enable low-temperature firing while large pores are controlled to prevent resistance issues
Solution Approach 2:
The invention applies local quality by creating non-uniform pore distribution with specific size characteristics in different regions of the silver powder particles. The controlled pore size distribution (25 pores/μm² in 10-30 nm range, 0.01 pores/μm² or less >200 nm) ensures that local pore characteristics optimize both firing temperature and final resistance
2Length of moving object
If silver powder with small particle diameters is used to draw fine wirings, then conductor patterns can be made finer, but particle uniformity and dispersion become more difficult to achieve
Solution Approach 1:
The invention changes the pore size parameter distribution within the silver powder particles to achieve optimal performance. By controlling pores to be 10-30 nm in diameter with specific density (25 pores/μm²), the invention enables fine conductor patterns while maintaining particle uniformity and proper dispersion characteristics
3Reliability
If a large number of small pores are dispersed in silver powder, then thermal weight loss temperature decreases and low resistance wirings are formed, but pore size control during production becomes more critical
Solution Approach 1:
The invention specifies precise parameter ranges for pore size (10-30 nm diameter) and pore density (25 pores/μm²) to achieve the desired balance between low resistance performance and manufacturability. These parameter specifications provide clear manufacturing targets while ensuring optimal firing and conduction properties
Solution Approach 2:
The invention establishes feedback mechanisms through detailed pore characterization specifications that allow manufacturers to control and verify pore size distribution. By defining specific measurable parameters (pore count per area, pore size ranges), the invention enables quality control and process optimization
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 controlled pore size distribution in the silver powder enables the formation of electrode wirings with lower resistance after firing, facilitating the creation of fine conductive patterns and improving the performance of electronic components like solar cells and multilayer capacitors.
Implementation Method 1
adding a reducing agent-containing solution containing aldehyde as a reducing agent to an aqueous reaction system containing silver ions and mixing the aqueous reaction system
Implementation Method 2
the conductive paste is heated at a temperature of 500° C. or higher to remove the organic solvent
Implementation Method 3
particles of the silver powder are sintered together to form a conductive film
Data Source
AI summary
Provided is silver powder including silver particles having closed pores inside the particles, wherein when cross sections of the silver particles are observed at a magnification of 10,000, an average of numbers of the pores having Heywood diameters of 200 nm or greater relative to an area of the cross sections is 0.01 pores/μm2 or less, and wherein when the cross sections of the silver particles are observed at a magnification of 40,000, an average of numbers of the pores having Heywood diameters of 10 nm or greater but less than 30 nm relative to the area of the cross sections is 25 pores/μm2 or more.