Silver Powder Surface Coating for Low-Resistance Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing silver powder for conductive pastes fail to completely prevent the generation of coarse silver secondary particles, affecting sinterability and electrical conductivity, particularly in the context of miniaturized electronic components and solar cells where low resistance is crucial.
Innovation Solution
A method involving the formation of a silver-ammine complex, reduction, and surface treatment with an emulsion of micelles with a cumulative 50% particle diameter of 1.5 μm or less, followed by coating with a polyvalent carboxylic acid to enhance dispersibility and conductivity without changing the surface treatment agent type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional emulsion with larger micelle particle diameter is used for surface treatment, then the dispersibility of silver powder is improved, but coarse silver secondary particles are generated
Solution Approach 1:
The invention changes the particle diameter parameter of micelles in the emulsion from conventional larger sizes to 1.5 μm or less (cumulative 50% particle diameter). This parameter change allows the emulsion to effectively disperse silver powder without generating coarse secondary particles, resolving the contradiction between dispersibility and particle size control.
2Manufacturing precision
If the particle diameter of micelles in the emulsion is reduced to prevent coarse particle formation, then manufacturing precision is improved, but the electrical conductivity of the resulting electrode decreases
Solution Approach 1:
The invention creates a composite surface treatment system combining two types of carboxylic acids (first and second carboxylic acids with different chain lengths) on the silver powder surface. This composite approach allows the use of smaller micelles for precision while the dual-carboxylic acid system maintains electrical conductivity by optimizing surface properties for both dispersibility and conduction.
3Ease of operation
If stearic acid is added in emulsion state to improve dispersibility, then the silver powder disperses uniformly in aqueous solution, but coarse silver secondary particles cannot be completely prevented
Solution Approach 1:
The invention changes the critical parameter of micelle particle diameter to 1.5 μm or less (cumulative 50%), which is significantly smaller than conventional emulsions. This parameter change enables complete prevention of coarse secondary particles while maintaining uniform dispersibility, overcoming the limitations of conventional stearic acid emulsions.
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 that achieves low resistance when formed into a paste for electrodes, improving electrical conductivity and preventing coarse particle formation, thus meeting the demands of modern electronic components and solar cells.
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
the fatty acid is emulsified in advance, that is, an emulsion in which fine micelles of the fatty acid are dispersed in water is formed
Implementation Method 3
the silver powder is surface-treated with stearic acid which is a dispersant, and the stearic acid is added in an emulsion state
Data Source
AI summary
A method for producing a silver powder enables a low resistance when the silver powder is made into a paste to form an electrode without changing the type of surface treatment agent. A silver powder, which enables an electrode to have a low resistance when the silver powder is made into a paste to form the electrode, is obtained by 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 surface of the silver powder is coated with the surface treatment agent. The surface of the silver powder is further coated with a polyvalent carboxylic acid in a step of producing the silver powder.