Conductive Pattern Dispersing Element for Printed Electronics
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Solution Overview
Problem
The existing printed electronics method using metal ink and metal paste faces challenges such as instability in resistivity over time, oxidation of copper particles leading to increased resistivity, and difficulty in soldering due to binder resin exudation, as well as cracking during the firing process, especially with copper oxide precursors.
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 and low resistance, allowing for sintering via plasma, light, or laser firing, and enhancing mechanical strength and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper oxide is used as a precursor for conductive pattern formation, then the resistivity is reduced and conductivity is improved, but oxidation occurs and resistivity increases over time
Solution Approach 1:
A reducing agent is added to the dispersing element in advance to reduce copper oxide to copper metal before the firing process. This preliminary reduction action ensures that the copper particles are in a reduced state during application and drying, preventing oxidation during storage and handling, while maintaining low resistivity and stable electrical conductivity over time.
Solution Approach 2:
A reducing agent acts as an intermediary substance that facilitates the conversion of copper oxide to copper metal. The reducing agent donates electrons to copper oxide, transforming it into conductive copper particles while being consumed in the process. This intermediary action resolves the contradiction by enabling the formation of stable, low-resistivity copper patterns from copper oxide precursors.
2Ease of manufacture
If binder resin is used in metal paste, then the paste can be applied and forms a conductive pattern, but binder resin exudates during firing causing soldering difficulty
Solution Approach 1:
The binder resin is completely removed by extraction during the firing process. The dispersing element is formulated to decompose and volatilize the binder resin at firing temperatures, extracting it from the final conductive pattern. This leaves behind only the copper particles and reducing agent products, eliminating the soldering barrier while maintaining the ease of application provided by the original binder system.
Solution Approach 2:
The chemical composition parameters of the dispersing element are changed during firing to transform the binder resin from a stable, non-volatile state to a volatile, decomposable state. By selecting binder resins with appropriate decomposition characteristics and controlling firing temperature and atmosphere, the binder is converted into gaseous products that escape, leaving a solder-friendly copper surface while maintaining manufacturability.
3Reliability
If high concentration of ultrafine particles is used, then the film thickness is reduced and conductivity is improved, but aggregation occurs and dispersion stability deteriorates
Solution Approach 1:
The dispersing element is formulated as a composite system containing ultrafine copper oxide particles, reducing agents, and dispersing agents in specific combinations. The reducing agents modify the surface chemistry of the ultrafine particles, creating repulsive forces that prevent aggregation. This composite approach maintains high particle concentration for excellent conductivity while ensuring long-term dispersion stability through synergistic interactions between the different components.
Solution Approach 2:
Dispersing agents act as intermediary substances that adsorb onto the surface of ultrafine copper oxide particles, creating a protective barrier that prevents direct particle-to-particle contact and aggregation. These intermediaries provide steric or electrostatic repulsion, enabling high concentrations of ultrafine particles to remain stably dispersed in the paste without compromising conductivity or causing aggregation during storage and application.
4Reliability
If copper particles are used instead of copper oxide, then conductivity is improved, but oxidation occurs during storage and handling
Solution Approach 1:
Copper oxide is used as the preliminary form in the dispersing element, which is then reduced to copper metal during the firing process. This preliminary use of copper oxide avoids the oxidation problem during storage and handling, as copper oxide is inherently stable in air. The reduction to conductive copper occurs only under controlled firing conditions, ensuring high conductivity without exposure to atmospheric oxidation.
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 high dispersion stability, low resistance, and improved solderability of the conductive pattern, reducing cracking and maintaining stability over time, making it suitable for both thin and thick film applications and various printing methods.
Implementation Method 1
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 and low resistance
Implementation Method 2
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
Implementation Method 3
allowing for sintering via plasma, light, or laser firing
Implementation Method 4
allowing for sintering via plasma, light, or laser firing
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.