Monocrystalline Silver Flake Particles for Conductive Paste
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Solution Overview
Problem
Conventional fine metal particles used in electrically conductive pastes for printed circuit boards have insufficient printing characteristics, thermal conductivity, and electrical conductivity due to their particle size and surface roughness.
Innovation Solution
The development of flake-like fine particles with a smooth surface (arithmetical mean roughness Ra not larger than 10 nm) and a median size of 0.1 μm to 20 μm, made from monocrystalline metals like silver, which are dispersed in a solvent to create an electrically conductive paste with enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fine metal particles are used, then the paste can be manufactured, but the printing characteristics, thermal conductivity, and electrical conductivity are insufficient
Solution Approach 1:
The invention changes the surface roughness parameter of the fine metal particles by controlling the particle formation process to achieve Ra ≤ 10 nm. This parameter change improves printing characteristics while maintaining particle size and composition, directly resolving the contradiction between reliability and manufacturing precision.
2Ease of manufacture
If the particle surface is rough, then the particles can be easily manufactured, but the dispersibility and contact area are reduced
Solution Approach 1:
The invention optimizes the surface roughness parameter to Ra ≤ 10 nm, which balances ease of manufacture with maximization of contact surface area. The controlled surface quality enables better dispersibility and larger contact area between particles, resolving the contradiction between manufacturing ease and quantity of effective contact surface.
3Device complexity
If the particles aggregate, then the paste formulation is simpler, but the printing characteristics and dispersibility deteriorate
Solution Approach 1:
By changing the surface roughness parameter to Ra ≤ 10 nm, the invention reduces particle aggregation tendencies. The smooth surface enables better dispersibility without complicating the paste formulation, as the improved surface properties naturally prevent aggregation, resolving the contradiction between device complexity and reliability.
4Productivity
If heating temperature is increased, then sintering is achieved faster, but thermal damage and energy consumption increase
Solution Approach 1:
The invention changes the surface roughness parameter to Ra ≤ 10 nm, which improves thermal contact between particles. This enables efficient sintering at lower temperatures, resolving the contradiction between productivity and temperature by allowing fast sintering without high thermal input through enhanced inter-particle contact.
5Reliability
If particle size is reduced, then electrical conductivity improves, but printing characteristics and thermal conductivity become insufficient
Solution Approach 1:
The invention changes the surface roughness parameter to Ra ≤ 10 nm for fine particles, which improves printing characteristics and thermal conductivity while maintaining the small particle size needed for electrical conductivity. The smooth surface enables better particle packing and contact, resolving the contradiction between electrical conductivity and 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
The smooth surface of the fine particles improves their dispersibility and contact area, leading to superior printing characteristics, high thermal conductivity, and efficient sintering at low temperatures, resulting in enhanced electrical conductivity.
Implementation Method 1
The fine particles according to the present invention have an arithmetical mean roughness Ra of not larger than 10 nm. In other words, the surface of the fine particles is smooth. The fine particles are superior in slidability. Thus, aggregation of a plurality of fine particles is suppressed.
Implementation Method 2
In the paste after printing, the fine particles overlap with each other with a large contact surface area. Thus, the paste shows a high thermal conductivity when being heated. With the paste, sintering is achieved through heating for a short period of time. With the paste, sintering is achieved through heating at a low temperature.
Implementation Method 3
In a pattern after sintering, the fine particles overlap with each other with a large contact surface area. Thus, the pattern can easily conduct electricity. The fine particles are also superior in electrical conductivity.
Data Source
AI summary
[Object] To provide fine particles 2 having excellent printing characteristics, thermal conductivity, and electrical conductivity.[Solution] The fine particles 2 are flake-like. A main component of the fine particles 2 is an electrically conductive metal. A representative metal is silver. The structure of this metal is monocrystalline. An arithmetical mean roughness Ra of the surface of the fine particles 2 is not larger than 10 nm. The fine particles 2, a solvent, a binder, and a dispersant, etc., are mixed to obtain an electrically conductive paste. By using the electrically conductive paste, a pattern connecting elements is printed on a printed circuit board of an electronic device.