Copper Oxide Ink Formulation for Stable Low-Resistance Conductive Films
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Solution Overview
Problem
The existing methods for manufacturing conductive substrates using metal inks or pastes face challenges such as instability of resistivity over time and the need for antioxidation treatments that hinder sintering, particularly with copper ultrafine particles, which affect the conductivity and longevity of the metal films.
Innovation Solution
A copper oxide ink comprising copper oxide, a dispersant, and a reducing agent, with specific ratios and properties, is used to form a conductive film on a substrate through firing treatments under reductive atmospheres, such as plasma or light irradiation, to achieve high dispersion and storage stability and low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper ultrafine particles are used to form conductive films, then low resistivity and excellent conductivity are achieved, but oxidation occurs readily requiring antioxidation treatment that hinders sintering
Solution Approach 1:
The patent converts the harmful oxidation of copper particles into a beneficial feature by using copper oxide particles as the starting material. The oxide layer that would normally hinder sintering is instead utilized as a stable, non-oxidizing precursor that reduces to copper during the sintering process, eliminating the need for separate antioxidation treatments while maintaining conductivity.
Solution Approach 2:
The patent changes the chemical state parameter of the copper from metallic copper to copper oxide, and controls the reduction process during sintering. By adjusting sintering temperature and atmosphere parameters, the copper oxide is reduced to copper while forming conductive networks, achieving both oxidation resistance and good sintering properties.
2Productivity
If metal ink is used with ultrafine particles for direct circuit printing, then productivity is improved and photoresist is eliminated, but antioxidation treatment is required that complicates the process
Solution Approach 1:
The patent eliminates the need for antioxidation treatment by using copper oxide particles instead of copper particles. The oxide form is inherently stable in air, allowing direct printing and sintering without complex antioxidation steps, thus maintaining high productivity while reducing process complexity.
3Reliability
If copper oxide is reduced to copper by heat or light in suitable atmosphere, then conductive film is formed, but the reducing agent may affect storage stability of the ink
Solution Approach 1:
The patent incorporates the reducing agent into the ink formulation in advance, but designs it to remain dormant during storage and only become active during controlled sintering. This preliminary preparation allows the ink to be stored stably while ensuring reduction capability is available when needed for conductive film formation.
Solution Approach 2:
The patent uses parameter changes to control the reducing agent's activity. The reducing agent is formulated to be stable at storage conditions (temperature, pH, atmosphere) but becomes active under sintering conditions, enabling conductive film formation. This separates the storage stability requirement from the reduction requirement by using different parameter regimes.
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 oxide ink method provides a conductive film with improved stability and low resistance, enabling the formation of conductive substrates suitable for various applications, including electrical conductivity and thermal management, while avoiding the limitations of traditional antioxidation treatments.
Implementation Method 1
reducing the copper oxide to copper by energy such as heat or active light rays in a suitable atmosphere
Implementation Method 2
a dispersion in which microparticles selected from a group consisting of metal microparticles and metal oxide microparticles are dispersed
Implementation Method 3
sintering at a temperature lower than the melting point of the metal can be performed
Implementation Method 4
firing treatments under reductive atmospheres, such as plasma or light irradiation
Data Source
AI summary
In the present invention, a conductive film having low resistance is formed on a substrate, said film having excellent storage stability and high dispersion stability as an ink. A copper oxide ink (1) contains a copper oxide (2), a dispersant (3), and a reducing agent. The content of the reducing agent is in the range of formula (1), and the content of the dispersant is in the range of formula (2). (1) 0.00010≤(reducing agent mass/copper oxide mass)≤0.10 (2) 0.0050≤(dispersant mass/copper oxide mass)≤0.30 The reducing agent content promotes the reduction of copper oxide to copper during firing, and promotes the sintering of copper.