Copper Oxide Dispersing Element for Low-Resistance Conductive Patterns
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Solution Overview
Problem
The existing printed electronics method using metal ink and paste faces challenges such as instability of resistivity over time, oxidation of copper particles leading to increased resistivity, and difficulties in soldering due to binder resin exudation, along with issues of cracks during the firing process.
Innovation Solution
A dispersing element containing copper oxide, a reductant, and a dispersing agent, with specific mass ratios and particle sizes, is used to form a conductive pattern with improved dispersion stability, low resistance, and enhanced solderability, employing plasma, light, or laser firing to promote sintering and reduce oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper particles are used as metal ink or paste, then conductivity is improved, but oxidation occurs leading to increased resistivity over time
Solution Approach 1:
The patent uses a core-shell structure where a non-oxidizing metal core (such as nickel or copper) is covered by a shell of metal oxide (such as copper oxide or nickel oxide). The metal oxide shell acts as an intermediary that prevents oxidation of the conductive metal core while maintaining electrical conductivity through the oxide layer, thus resolving the contradiction between conductivity and oxidation resistance.
Solution Approach 2:
The patent creates composite particles consisting of a metal core and a metal oxide shell. This composite structure combines the high conductivity of the metal core with the oxidation resistance of the metal oxide shell, achieving both improved conductivity and long-term resistivity stability by preventing the oxidation that would otherwise degrade pure metal particles.
2Stability of the object's composition
If binder resin is used in metal paste, then particle aggregation is prevented, but binder resin exudation occurs hindering soldering
Solution Approach 1:
The patent removes the binder resin component from the metal paste formulation entirely. Instead of using binder resin to prevent aggregation, the invention relies on the core-shell particle structure and controlled firing processes to achieve both dispersion stability and solderability, eliminating the source of the problem (binder resin exudation) while maintaining the benefits.
Solution Approach 2:
The patent changes the physical and chemical parameters of the metal particles by creating a core-shell structure with specific size ratios and compositions. This allows the particles to maintain stable dispersion without binder resin, and the surface characteristics of the core-shell structure provide good solderability directly, eliminating the need for binder resin and avoiding exudation issues.
3Volume of moving object
If ultrafine copper particles are used, then thin film thickness is achieved, but sintering temperature control becomes difficult
Solution Approach 1:
The patent uses composite core-shell particles where the metal oxide shell has a higher melting point than the metal core. During the firing process, the metal oxide shell remains stable at temperatures that would cause ultrafine metal particles to sinter excessively, allowing precise control of the sintering process to achieve thin films while maintaining particle size control and preventing unwanted aggregation.
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 solution achieves a conductive pattern with high dispersion stability, low resistance, and excellent solderability, reducing the likelihood of cracks and maintaining performance over time, while allowing for both thin and thick film applications.
Implementation Method 1
the copper oxide is reduced to copper under an appropriate atmosphere by energy, such as heat and active ray to form a copper thin film
Implementation Method 2
A surface diffusion itself in the ultrafine particles of the copper oxide occurs at a temperature lower than 300° C. Accordingly, when the copper oxide is reduced to the copper under the appropriate atmosphere by energy, the superparticles of the copper mutually form fine random chains through sintering
Implementation Method 3
The content of the dispersing agent is in a range of formula (2). The dispersing agent prevents aggregation of copper oxide particles
Implementation Method 4
employing plasma, light, or laser firing to promote sintering and reduce oxidation
Implementation Method 5
employing plasma, light, or laser firing to promote sintering and reduce oxidation
Data Source
AI summary
A conductive pattern having high dispersion stability and a low resistance over a board is formed. A dispersing element (1) contains a copper oxide (2), a dispersing agent (3), and a reductant. Content of the reductant is in a range of a following formula (1). Content of the dispersing agent is in a range of a following formula (2).0.0001≤(reductant mass/copper oxide mass)≤0.10 (1)0.0050≤(dispersing agent mass/copper oxide mass)≤0.30 (2)The dispersing element containing the reductant promotes reduction of copper oxide to copper in firing and promotes sintering of the copper.