Silver Powder Production via High-Pressure Water Atomization
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Solution Overview
Problem
Conventional methods for producing silver powder for electrically conductive pastes result in high carbon content impurities, leading to gas production during burning, which causes cracks in the conductive film and adhesion issues, and the powder is prone to agglutination, making it difficult to form thin films with small particle diameters for miniaturized electronic components.
Innovation Solution
A silver powder with a copper content of at least 40 ppm and carbon content not exceeding 0.1% by weight is produced by rapidly cooling and solidifying molten silver using high-pressure water atomization, resulting in a powder with a controlled particle size and low agglutination, suitable for use in electrically conductive pastes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet reducing method is used to produce silver powder, then silver particles can be deposited by reduction, but carbon containing compounds are incorporated into the particles causing impurities
Solution Approach 1:
The invention changes the chemical composition parameter by adding copper to the silver melt (40-10000 ppm), which fundamentally alters the purification mechanism during water atomization. This parameter change enables the removal of carbon impurities through oxidation at the copper-rich particle surfaces, achieving high purity silver powder that cannot be obtained by conventional wet reduction methods.
Solution Approach 2:
The invention utilizes phase transition from molten state to solid state through rapid cooling by water atomization. This phase transition occurs so quickly that carbon impurities are excluded from the solidifying silver lattice and remain in the melt or form surface oxides, thereby producing high-purity silver particles without carbon incorporation.
2Manufacturing precision
If conventional water atomizing method is used to produce silver powder with low carbon content, then carbon impurities are reduced, but the powder is easy to be agglutinated forming large secondary particles
Solution Approach 1:
The invention changes the chemical composition parameter by adding copper (40-10000 ppm) to the silver, which fundamentally alters the surface properties and oxidation behavior during water atomization. This parameter change prevents agglutination by promoting uniform oxide formation that acts as a barrier between particles, maintaining fine particle size distribution while achieving low carbon content.
3Length of moving object
If particle diameters are decreased for miniaturization, then electronic parts can be miniaturized, but the silver powder becomes more prone to agglutination
Solution Approach 1:
The invention changes the chemical composition by adding copper (40-10000 ppm) to the silver, which fundamentally alters the surface oxidation characteristics during water atomization. This parameter change creates a protective oxide layer on fine particles that prevents agglutination, enabling the use of small particle diameters (D50: 1-15 μm) for miniaturized electronic parts without suffering from agglutination problems.
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 produced silver powder effectively reduces carbon-related defects in the conductive film, enhances adhesion, and prevents agglutination, enabling the formation of thin, high-conductivity films for miniaturized electronic components.
Implementation Method 1
rapidly cooling and solidifying a molten metal of silver, which contains 40 ppm or more of copper, by spraying a high-pressure water onto the molten metal while allowing the molten metal to drop
Implementation Method 2
a silver powder, which has a copper content of not less than 40 ppm and a carbon content of not higher than 0.1% by weight, is produced by rapidly cooling and solidifying a molten metal of silver, which contains 40 ppm or more of copper
Implementation Method 3
there is known a method for producing a silver powder by a so-called water atomizing method for rapidly cooling and solidifying a molten metal of silver, which is prepared by melting silver, by spraying a high-pressure water onto the molten metal while allowing the molten metal to drop
Data Source
AI summary
A silver powder which has a small content of carbon and which is difficult to be agglutinated, and a method for producing the same. While a molten metal, which is prepared by melting silver to which 40 ppm or more of copper is added, is allowed to drop, a high-pressure water is sprayed onto the molten metal to rapidly cool and solidify the molten metal to produce a silver powder which contains 40 ppm or more of copper, 0.1% by weight or less of carbon and 0.1% by weight or less of oxygen and wherein the particle diameter (D50 diameter) corresponding to 50% of accumulation in volume-based cumulative distribution of the silver powder, which is measured by means of a laser diffraction particle size analyzer, is in the range of from 1 μm to 15 μm, the average particle diameter (SEM diameter) of single particles being in the range of from 1 μm to 8 μm when it is measured by means of a field emission scanning electron microscope (SEM), the ratio (SEM diameter/D50 diameter) of the SEM diameter to the D50 diameter being in the range of from 0.3 to 1.0.