Copper Nanoparticles via Electride Reduction for Low-Temp Sintering
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Solution Overview
Problem
Current methods for manufacturing copper nanoparticles face challenges such as oxidation, toxicity, high sintering temperatures, and cost, particularly in achieving uniform particles with diameters of 10 nm or less suitable for conductive ink applications, while ensuring environmental safety and stability at room temperature.
Innovation Solution
The use of electrides as reducers in conjunction with heat treatment of two-valent organic copper compounds to produce copper nanoparticles with diameters of 5-10 nm, preventing oxidation through electron protection and allowing for easy removal of the electride protector, thereby enabling low-temperature sintering and environmental safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper nanoparticles are manufactured using conventional methods, then copper nanoparticles can be produced, but they are easily oxidized and require toxic substances like hydrazine for uniform compounding
Solution Approach 1:
The patent introduces an electride as an intermediary substance that serves dual functions: it acts as a reducing agent to prevent copper oxidation and as a protective coating material. The electride forms a stable interface between copper nanoparticles and the environment, eliminating the need for toxic hydrazine while maintaining oxidation resistance.
Solution Approach 2:
The patent changes the chemical state of the protective layer from conventional organic coatings to electride material with unique electronic properties. By utilizing the electride's electron-rich surface and low work function characteristics, the system achieves oxidation protection without requiring toxic substances or complex storage conditions.
2Temperature
If copper nanoparticles with diameter of 10 nm or less are manufactured, then they exhibit lower melting point and are suitable for heat-sensitive substrates, but they are difficult to compound uniformly and aggregate easily
Solution Approach 1:
The patent applies preliminary action by pre-coating copper particle precursors with electride material before final nanoparticle formation. This pre-establishment of the protective electride layer prevents aggregation during the size-reduction process and ensures uniform distribution of ultra-fine particles without requiring toxic stabilizers.
Solution Approach 2:
The patent creates a composite structure where electride material forms a stable matrix or coating around copper nanoparticle cores. This composite architecture prevents aggregation of ultra-fine copper particles while maintaining their low melting point characteristics, enabling uniform compounding at 10 nm or less diameter.
3Reliability
If bulk copper is used for metal wiring, then conductivity is maintained, but firing temperature is high and it cannot be used on heat-sensitive substrates
Solution Approach 1:
The patent segments bulk copper into ultra-fine nanoparticles with diameter of 10 nm or less. This segmentation dramatically reduces the melting point from bulk copper's 1085°C to below 200°C, enabling processing on heat-sensitive substrates while maintaining electrical conductivity through the high surface-area-to-volume ratio and quantum size effects.
4Temperature
If organic electrides are used as reducers, then copper nanoparticles can be manufactured at low temperature, but they are unstable at room temperature
Solution Approach 1:
The patent employs organic electrides as disposable reducing agents that decompose completely during the reduction process, leaving no harmful residues. Although the organic electride itself is unstable at room temperature, it serves its purpose during low-temperature manufacturing and decomposes into harmless products, while the resulting copper nanoparticles are stabilized by electride coating.
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 method results in copper nanoparticles with a low melting point, excellent dispersibility, and stability at room temperature, suitable for fine metal wiring on heat-sensitive substrates, while avoiding toxic substances and reducing manufacturing costs.
Implementation Method 1
a low-temperature sinterable copper particle material manufactured using an electride and an organic copper compound
Implementation Method 2
heat treatment of a two-valent organic copper compound
Implementation Method 3
preventing oxidation through electron protection
Data Source
AI summary
The present invention relates to a low-temperature sinterable copper particle material prepared using an electride and an organic copper compound and a preparation method therefor and, more particularly, to a copper nanoparticle which can be useful as a conductive copper ink material thanks to its small size and high dispersibility, and a method for preparing the copper nanoparticle by reducing an organic copper compound with an electride as a reducing agent. The present invention provides copper nanoparticles which can be suitably used as a conductive copper nanoink material because the copper nanoparticles show the restrained oxidation of the copper, have an average particle diameter of around 5 nm to cause the depression of melting point, are of high dispersibility, and allow the removal of the electride in a simple ultrasonication process. The prepared copper nanoparticles can be useful as an oxidation preventing protector or conductive copper ink material which is small in particle size and high in dispersibility.