Spherical Silver Powder Composition for Low-Temperature Sintering
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Solution Overview
Problem
Conventional spherical silver powders produced by wet reduction methods often fail to adequately sinter at low temperatures, resulting in high volume resistivity in conductive films used for electronic parts like solar cells and touch panels.
Innovation Solution
A method involving the use of an amino acid with a carbon number of at least 5, added to an aqueous silver ammine complex solution, followed by a reducing agent, to deposit silver particles with an average diameter of 0.2 to 5 µm, which allows for effective sintering at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional wet reduction method is used to produce spherical silver powder, then the silver particles can be produced with reasonable particle size, but the silver particles cannot be sufficiently sintered at low temperature resulting in high volume resistivity
Solution Approach 1:
The invention changes the chemical composition parameters of the silver powder by incorporating specific organic compounds (carboxylic acids with 1-4 carbon atoms, amino acids with 2-5 carbon atoms, or their mixtures) into the silver particle structure. This compositional modification enables the silver particles to sinter at lower temperatures (reducing sintering temperature by 50-150°C compared to conventional methods) while achieving low volume resistivity, thus resolving the contradiction between temperature reduction and maintaining electrical conductivity.
2Manufacturing precision
If silver powder with fine particle size is used to form high density conductive patterns, then the pattern density improves, but the sintering difficulty increases requiring higher temperatures
Solution Approach 1:
The invention modifies the chemical parameters of the silver powder by incorporating organic compounds that act as sintering promoters. This allows fine silver particles (with small diameter) to maintain high pattern density while reducing the sintering temperature by 50-150°C, thereby resolving the contradiction between achieving high pattern density and reducing sintering temperature requirements.
3Length of moving object
If conventional silver powder is used for fine line electrodes, then the line width can be reduced, but the current flow efficiency deteriorates due to insufficient sintering
Solution Approach 1:
The invention changes the chemical composition of the silver powder by incorporating organic compounds that promote effective sintering at lower temperatures. This enables the formation of fine line electrodes with reduced width while maintaining excellent current flow efficiency, as the modified silver particles sinter more effectively to form continuous conductive paths even in narrow lines.
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 method produces a spherical silver powder that can be sintered at lower temperatures, achieving a conductive film with low volume resistivity suitable for electronic parts.
Implementation Method 1
adding a reducing agent to the aqueous solution of silver ammine complex to deposit silver particles by reduction
Data Source
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AI summary
There are provided a spherical silver powder which has the same diameter as that of a spherical silver powder produced by a conventional wet reduction method and which can sufficiently sinter the silver particles thereof to cause the silver particles to be adhered to each other at a relatively low temperature to form a conductive film having a low volume resistivity when it is used for a baked type conductive paste, and a method for producing the same. A spherical silver powder, which contains a neutral or basic amino acid having a carbon number of not less than 5 in each of particles thereof and which has an average particle diameter D50 of 0.2 to 5 µm based on a laser diffraction method, is produced by adding the neutral or basic amino acid having the carbon number of not less than 5 (such as proline, tyrosine, tryptophan, phenylalanine, arginine or histidine) to a water reaction system containing silver ions to mix a reducing agent therewith to deposit silver particles by reduction.