Micron-Scale Copper Liquid Composition for Low-Temperature Sintering
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Solution Overview
Problem
Conventional nano metal sintering technologies face challenges with high porosity, non-uniform density, and poor conductivity due to oxidation and agglomeration of nano copper particles during low-temperature sintering, leading to suboptimal electrical, thermal, and mechanical characteristics in sintered products.
Innovation Solution
A liquid composition comprising micron-scale copper particles dispersed in organic acids, such as ascorbic acid and oxalic acid, with a solvent, which undergoes a redox reaction to form a dense and uniform copper layer at temperatures below 150°C, preventing excessive oxidation and agglomeration, and enhancing sintering efficiency and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If nano copper particles are used for low-temperature sintering, then sintering temperature is reduced, but oxidation and agglomeration occur leading to high porosity and poor conductivity
Solution Approach 1:
The patent uses organic acid solution (creating an oxygen-free chemical environment) to displace atmospheric oxygen, preventing copper particle oxidation during low-temperature sintering. The organic acid acts as a protective medium that eliminates harmful oxidative reactions while maintaining low sintering temperatures.
Solution Approach 2:
The organic acid solution serves as an intermediary substance that facilitates low-temperature sintering by providing both protection against oxidation and prevention of particle agglomeration. It mediates between the copper particles and the environment, enabling densification without direct contact with oxygen.
2Temperature
If nano copper particles are scattered in solution, then low-temperature sintering is enabled, but particles agglomerate easily reducing scatterability control
Solution Approach 1:
The organic acid solution acts as an intermediary that prevents direct particle-particle contact that would cause agglomeration. It maintains particle dispersion by providing steric or electrostatic barriers, enabling controlled scattering and deposition during the sintering process.
Solution Approach 2:
The patent changes the chemical parameters of the dispersion medium by using organic acid solution with specific pH and chemical properties. This alters the surface chemistry of copper particles, modifying their interaction with the solvent and preventing agglomeration while maintaining scatterability.
3Temperature
If high surface area nano particles are used, then sintering temperature is lowered, but oxidation level increases reducing product quality
Solution Approach 1:
The organic acid solution creates a chemically inert environment that excludes oxygen from contact with high-surface-area copper particles. This prevents oxidation reactions that would otherwise occur more readily on high-surface-area particles, maintaining product quality despite the low sintering temperature.
Solution Approach 2:
The patent converts the high reactivity of nano particles (which causes oxidation) into a benefit by using the organic acid to control the reaction. The organic acid selectively reacts with or protects the particles, transforming the potential harm of high surface area into controlled, beneficial low-temperature sintering.
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 achieves a conductive structural layer with low resistance (below 0.04 ohm per square) and high structural compactness, ensuring good conductivity and uniformity, suitable for applications in electronic components and distribution layers.
Implementation Method 1
a redox reaction is taken place between the copper particles and the organic acid solution, wherein a part of the surface of the copper particle is dissolved into the organic acid solution to form copper ions, and then the liquid composition is applied to a substrate, and then the copper ions are reduced back to the copper particles
Implementation Method 2
the liquid composition formed by the micron-scale copper particles the present invention is capable of carrying out the reaction sintering at low temperature without having any excessive oxidation of the copper particles
Data Source
AI summary
A liquid composition includes copper particles, an organic acid, and a solvent. The copper particle has a particle size of 0.5 μm˜30 μm which falls in a micron scale. The liquid composition performs reaction sintering by redox reactions taken place between the copper particles and an organic acid solution at a low temperature of 150° C. in order to produce a dense copper layer and improve the conventional micron-scale copper particles that requires a protective atmosphere for the high-temperature sintering before achieving the required densification. This liquid composition also prevents an excessive oxidation of the nano copper particles during the low-temperature sintering process and a failure of the dense sintering. Due to the agglomeration of nano copper particles, some areas have to be sintered first, so that the sintered products have a good uniformity of tissue and a low resistance below 0.04 ohm per square (Ω/□).