Silver Powder Emulsion Control for Fine Particle Dispersion
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Solution Overview
Problem
Existing methods for producing silver powder for electrically conductive pastes struggle to prevent the formation of coarse silver secondary particles, which can lead to poor dispersibility and increased resistance in electronic components.
Innovation Solution
The method involves forming a silver-ammine complex, reducing it with a reducing agent, and then adding an O/W-type emulsion with micelles of a surface treatment agent having a volume-based cumulative 50% particle diameter of 1.5 μm or less to improve the dispersibility and prevent coarse particle formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stearic acid is added in an emulsion state to improve dispersibility of silver powder, then the dispersibility is improved, but coarse silver secondary particles still form
Solution Approach 1:
The patent changes the particle size parameter of the emulsion from conventional larger sizes to specifically 1.5 μm or less in volume-based cumulative 50% particle diameter. This parameter change allows the emulsion to penetrate and disperse silver particles more effectively without causing aggregation, thus improving dispersibility while preventing coarse secondary particle formation.
Solution Approach 2:
The patent uses an emulsion with controlled micelle size as an intermediary substance between the silver particles and the dispersion medium. The specifically sized emulsion (D50 ≤ 1.5 μm) acts as a mediator that facilitates uniform distribution of silver particles without inducing aggregation, resolving the contradiction between improving dispersibility and preventing coarse particle formation.
2Ease of manufacture
If conventional emulsion is used for surface treatment, then the process is simple, but particle size distribution is broad and resistance is high
Solution Approach 1:
The patent modifies the particle size parameter of the emulsion used in the surface treatment step, specifying that the volume-based cumulative 50% particle diameter should be 1.5 μm or less. This controlled parameter change narrows the particle size distribution of the resulting silver powder while maintaining the simplicity of the emulsion addition process, thus achieving both ease of manufacture and improved manufacturing precision.
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
This approach results in a silver powder with a smaller particle size distribution and lower resistance when made into a paste, enhancing the performance of electronic components by improving the uniformity and conductivity of the silver powder.
Implementation Method 1
a reduction step of reducing the silver complex with a reducing agent by adding the reducing agent to the aqueous solution containing the silver complex, thereby obtaining a slurry of a silver powder
Implementation Method 2
an emulsion addition step of adding an O/W-type emulsion containing micelles of a surface treatment agent having a volume-based cumulative 50% particle diameter D50 obtained by a laser diffraction particle size distribution analysis of 1.5 μm or less to the slurry of the silver powder
Implementation Method 3
the dispersibility of the silver powder in a slurry containing the reduced and deposited silver powder is improved
Data Source
AI summary
A method is provided for producing a silver powder which has a smaller particle size distribution than the conventional one without changing the type of surface treatment agent, and also for enabling a low resistance when the silver powder is made into a paste to form an electrode. The method for producing a silver powder includes adding an O/W-type emulsion containing micelles of a surface treatment agent having a volume-based cumulative 50% particle diameter D50 obtained by a laser diffraction particle size distribution analysis of 1.5 μm or less to a slurry of a silver powder. The dispersibility of the silver powder in the slurry containing the silver powder is then improved.