Silver Powder Surface Chemistry for Low-Temperature Conductive Pastes
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Solution Overview
Problem
There is a need for a silver powder suitable for low-temperature firing in conductive pastes to alleviate thermal stress on substrates with low heat resistance, particularly for applications like wire printing on resin substrates, where a firing temperature of 200°C or lower is desirable.
Innovation Solution
A method of producing a silver powder involves adding an azole to a silver ammine complex aqueous solution, followed by a reductant, and then an unsaturated fatty acid, such as linoleic or linolenic acid, to achieve a specific surface area and particle size distribution that enhances compatibility and dispersibility in butyl carbitol acetate, enabling low-temperature firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional silver powders are used in conductive pastes, then high firing temperatures are required, but this causes thermal stress on substrates with low heat resistance
Solution Approach 1:
The invention changes the surface characteristics parameters of silver powder by controlling particle size (D50: 0.5-2.0 μm) and specific surface area (2.0-4.0 m²/g), and by adding specific additives (azole and unsaturated fatty acid), thereby enabling the conductive paste to fire at lower temperatures (150-250°C) and reduce thermal stress on substrates
2Temperature
If silver powder with small particle size is used to enable low-temperature firing, then firing temperature can be reduced, but particle aggregation and poor dispersibility occur
Solution Approach 1:
The invention uses azole and unsaturated fatty acid as intermediary substances that adsorb onto the silver powder particle surfaces, providing steric and electrostatic repulsion forces that prevent particle aggregation and maintain stable dispersion in the conductive paste matrix
Solution Approach 2:
By precisely controlling the particle size distribution (D50: 0.5-2.0 μm) and specific surface area (2.0-4.0 m²/g) parameters, the invention optimizes the balance between low-temperature firing capability and particle dispersibility, preventing aggregation while enabling low-temperature processing
3Ease of manufacture
If silver powder is produced without surface treatment agents, then production cost is reduced, but compatibility with dispersion medium and dispersibility are insufficient
Solution Approach 1:
The invention introduces azole and unsaturated fatty acid as surface treatment agents that act as intermediaries between the silver powder particles and the dispersion medium (butyl carbitol acetate), improving compatibility and dispersibility through chemical adsorption and surface modification
Solution Approach 2:
By optimizing the dosage and type of surface treatment agents (azole and unsaturated fatty acid), the invention achieves adequate compatibility and dispersibility at reasonable production costs, balancing performance requirements with manufacturing economics
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 resulting silver powder provides excellent compatibility and dispersibility in butyl carbitol acetate, reducing viscosity and enabling low-temperature firing while maintaining low specific resistance, making it suitable as a conductive filler for conductive pastes.
Implementation Method 1
adding an azole to a silver ammine complex aqueous solution to obtain a first liquid; adding a reductant to the first liquid to obtain a second liquid; and adding a fatty acid to the second liquid to obtain a third liquid
Implementation Method 2
adding a reductant to the first liquid to obtain a second liquid
Data Source
AI summary
Provided are a silver powder that is suitable as a conductive filler for a conductive paste that enables low-temperature firing and a method of producing this silver powder. The method of producing a silver powder includes an azole addition step of adding an azole to a silver ammine complex aqueous solution to obtain a first liquid, a reductant addition step of adding a reductant to the first liquid to obtain a second liquid, and a fatty acid addition step of adding a fatty acid to the second liquid to obtain a third liquid. The fatty acid is an unsaturated fatty acid including two or more double bonds.