Copper Particle Mixture with Alcohol Protective Layer for Low-Temperature Sintering
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Solution Overview
Problem
Copper nanoparticles with an average diameter of 10 nm or less are highly reactive and unstable, leading to oxidation and aggregation, making it difficult to achieve low-temperature sintering and preserving them for use in conductive copper ink materials, especially on substrates like paper or plastic.
Innovation Solution
A copper particle mixture comprising copper fine particles with an average diameter of 0.1 μm to 5 μm coated with dicarboxylic acid and copper nanoparticles with a central copper single crystal and a protective layer of C3-6 primary or secondary alcohols, allowing for low-temperature sintering and improved dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If copper nanoparticles with average diameter of 10 nm or less are used to reduce sintering temperature, then sintering temperature is reduced, but oxidation and aggregation occur more easily
Solution Approach 1:
A protective layer comprising C3-6 primary or secondary alcohols is introduced as an intermediary substance between the copper nanoparticle core and the external environment. This protective layer prevents direct contact between copper nanoparticles and oxygen, thereby suppressing oxidation while maintaining low sintering temperature. The alcohol molecules adsorb onto the copper surface, forming a barrier that stabilizes the nanoparticles without requiring high temperatures for removal.
Solution Approach 2:
The invention creates a composite structure consisting of a copper nanoparticle core (1-10 nm) surrounded by an organic protective shell (C3-6 alcohol). This core-shell composite structure combines the beneficial low-sintering-temperature property of small copper nanoparticles with the stabilizing effect of the organic protective layer, preventing both oxidation and aggregation simultaneously.
2Reliability
If polymer protective agents are used to stabilize copper nanoparticles, then oxidation is suppressed, but electrical conductivity decreases due to incomplete removal
Solution Approach 1:
The invention changes the key parameter of the protective agent from high-molecular-weight polymers to low-molecular-weight C3-6 alcohols. This parameter change allows the protective layer to be effectively removed at low temperatures (below the sintering temperature), preventing contamination of the sintered copper wire and maintaining high electrical conductivity. The low molecular weight and specific chemical structure of C3-6 alcohols enable complete decomposition and volatilization without leaving residual carbonaceous materials.
3Manufacturing precision
If copper nanoparticles are used to form fine metal wire, then thermal conductivity and electrical conductivity improve, but copper oxidation causes migration and short circuits
Solution Approach 1:
The invention converts the high reactivity of copper nanoparticles, which normally causes oxidation, into a benefit by using the same reactive copper surface to strongly adsorb C3-6 alcohol molecules. This adsorption creates a protective layer that prevents oxidation. The high surface area to volume ratio of small copper nanoparticles, which increases oxidation risk, is transformed into an advantage by providing more adsorption sites for the protective alcohol layer.
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 copper particle mixture enables efficient low-temperature sintering at 120°C or less in a non-reducing atmosphere or 150°C or less in a reducing atmosphere, forming conductive copper wires with reduced oxidation and improved electrical conductivity.
Implementation Method 1
the protective layer contains at least one member selected from the group consisting of C3-6 primary alcohols, C3-6 secondary alcohols, and derivatives thereof
Implementation Method 2
The copper particle mixture enables efficient low-temperature sintering at 120°C or less in a non-reducing atmosphere or 150°C or less in a reducing atmosphere, forming conductive copper wires
Implementation Method 3
heated at a low temperature to thereby remove the organic substance from the surface of the metal nanoparticles, thereby causing metal bonds between the metal nanoparticles
Data Source
AI summary
A copper particle mixture ensures suppression of copper oxidation and high dispersibility, and that can be sintered at a low temperature in a short period of time can suitably be used for a conductive copper ink material. The copper particle mixture contains copper fine particle A and copper nanoparticle B, the copper fine particle A having an average particle diameter of 0.1 μm to 5 μm, and being coated with at least one dicarboxylic acid selected from the group consisting of malonic acid and oxalic acid, the copper nanoparticle B comprising a central portion comprising a copper single crystal, and a protective layer surrounding the central portion, and having an average particle diameter of 1 nm to 100 nm, and the protective layer of the copper nanoparticle B containing at least one member selected from the group consisting of C3-6 primary alcohols, C3-6 secondary alcohols, and derivatives thereof.