Silver Metal Paste Composition for Fine-Line Printing Adhesion
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Solution Overview
Problem
Existing metal pastes struggle with printing drawability, particularly in forming narrow and complex wiring patterns, and lack continuous printability and adhesion to substrates, which are essential for modern electronic device manufacturing.
Innovation Solution
A metal paste formulation using a mixed solvent system of dihydroterpineol or terpineol with another solvent having a boiling point of 240°C or more, combined with high molecular weight ethyl cellulose and polyvinyl acetal resin, to enhance printing drawability and adhesion, while maintaining low-temperature sinterability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a metal paste contains only metal nanoparticles dispersed in a solvent, then the paste is simple in composition, but the printability is poor and may form wirings with running or disconnection
Solution Approach 1:
The patent uses composite materials by combining metal nanoparticles with organic additives (ethyl cellulose, polyvinyl acetal resin, and other binders) to create a metal paste formulation that achieves both good printability and wiring integrity. The organic components form a matrix that holds the metal particles together during printing and provides adhesion to the substrate, resolving the contradiction between simplicity and printability.
2Length of moving object
If the wiring width is narrowed to 100 μm or less for modern electronic devices, then the device complexity increases, but the printing drawability becomes insufficient and cannot form precise wiring patterns
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size distribution of metal nanoparticles (using a mix of different sizes), adjusting the concentration and type of organic additives, and controlling the solvent composition to achieve a paste viscosity and rheology that enables precise printing of narrow wirings (100 μm or less) without running or disconnection.
Solution Approach 2:
The patent uses local quality by incorporating additives with specific functions at different locations within the paste system: ethyl cellulose provides bulk viscosity control, polyvinyl acetal resin enhances adhesion at the wiring-substrate interface, and smaller particles fill gaps to improve pattern fidelity in narrow wiring regions.
3Manufacturing precision
If a metal paste uses high molecular weight ethyl cellulose to improve printability, then the printability is improved, but the continuous printability and adhesion to substrate are insufficient
Solution Approach 1:
The patent merges multiple functional components: high molecular weight ethyl cellulose (for printability and rheology control) is combined with polyvinyl acetal resin (for adhesion and continuous printability), along with other binders and solvents. This combination allows the paste to maintain its shape during printing while adhering strongly to the substrate and enabling continuous printing operations without degradation.
4Temperature
If the sintering temperature is reduced for low temperature sinterability, then the energy consumption decreases, but the adhesion and wiring integrity may be compromised
Solution Approach 1:
The patent uses organic additives (ethyl cellulose, polyvinyl acetal resin, and other binders) as intermediaries that facilitate adhesion between metal particles and the substrate at low sintering temperatures. These organic components decompose and carbonize during low-temperature sintering, forming a bonding matrix that ensures wiring integrity without requiring high temperatures that would damage the substrate or consume excessive energy.
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 significantly improves printing drawability and continuous printability, ensuring precise wiring formation with high adhesion to substrates, even in narrow and complex patterns, without compromising low-temperature sinterability.
Implementation Method 1
When in the form of a nano-level fine particle of several tens nm or less, a metal particle exhibits a phenomenon that a melting point thereof remarkably reduces as compared with a bulk material. The metal paste disclosed by the present applicant utilizes this phenomenon, and contains, as a metal component, a silver nanoparticle having controlled average particle size and particle size distribution, and is capable of wiring formation at a low temperature.
Implementation Method 2
Since the metal paste of the present applicant contains the high molecular weight ethyl cellulose, the rheology characteristic of the metal paste is made preferable to improve its printability.
Data Source
AI summary
The present invention relates to a metal paste for forming a metal wiring containing a solid content of a silver particle and kneaded with a solvent. The solid content of the metal paste contains a silver particle having prescribed particle size distribution and average particle size, and using an amine compound as a protective agent. The solvent is a mixed solvent in which two organic solvents of a solvent A and a solvent B are mixed. The solvent A is dihydroterpineol or terpineol, and the solvent B is at least one organic solvent having a boiling point of 240° C. or more. The mixed solvent has a Hansen solubility parameter distance Ra from dihydroterpineol of 3.0 MPa1/2 or less. The metal paste further contains a high molecular weight ethyl cellulose as a first additive, and a polyvinyl acetal resin as a second additive.