Solvent-Free Silver Nanoparticle Ink for Low-Temperature Annealing
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Solution Overview
Problem
Current methods for preparing conductive structures for electronic devices face challenges in achieving thicknesses of several micrometers with low annealing temperatures, stability, and cost-effectiveness, particularly for plastic substrates that cannot withstand high temperatures, and require environmentally harmful solvents.
Innovation Solution
A solvent-free method involving the chemical reduction of metal compounds with reducing agents and stabilizers to form metal nanoparticles, which are then isolated and incorporated into a liquid composition with a polymeric binder for deposition and low-temperature processing to form conductive features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional methods using long-chain carboxylic acid stabilizers are used, then solubility for solution-processing is sufficient, but annealing temperature must be greater than 200°C which exceeds the withstand capability of most plastic substrates
Solution Approach 1:
The patent changes the molecular structure parameter of the stabilizer by using short-chain carboxylic acids (C2-C12) instead of long-chain carboxylic acids (greater than C12). This parameter change reduces the boiling point and weakens the bond between the stabilizer and silver nanoparticles, enabling annealing at temperatures below 200°C while maintaining sufficient solubility for solution-processing.
2Reliability
If high annealing temperatures greater than 200°C are used to obtain conductive silver films, then conductivity is achieved, but dimensional stability is compromised on plastic substrates
Solution Approach 1:
The patent changes the stabilizer's carbon chain length parameter to be shorter (C2-C12), which reduces the thermal stability of the stabilizer-silver bond. This allows the silver nanoparticles to coalesce and form conductive pathways at lower temperatures (below 200°C), thereby achieving the required conductivity while preserving the dimensional stability of temperature-sensitive plastic substrates.
3Ease of manufacture
If environmentally harmful solvents are used in current methods, then metal nanoparticles can be prepared, but environmental safety and cost-effectiveness are compromised
Solution Approach 1:
The patent extracts and eliminates harmful organic solvents from the metal nanoparticle preparation process. By using short-chain carboxylic acid stabilizers that provide sufficient solubility and processability on their own, the method removes the need for additional environmentally harmful solvents, thereby achieving green chemistry goals while maintaining ease of manufacture.
4Temperature
If short-chain carboxylic acid stabilizers are used, then annealing temperature can be reduced below 200°C, but solubility for solution-processing may be insufficient
Solution Approach 1:
The patent optimizes the carbon chain length parameter of the carboxylic acid stabilizer to fall within the C2-C12 range. This specific parameter range represents an optimal balance: the chains are short enough to enable low-temperature annealing (below 200°C) but long enough to provide sufficient hydrophobic interactions and solubility for effective solution-processing and deposition.
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
This method produces stable, low-cost, environmentally safe metal nanoparticles suitable for conductive ink applications, enabling conductive features with thicknesses up to several micrometers at annealing temperatures below 130°C, improving shelf life and reducing production costs while avoiding harmful solvents.
Implementation Method 1
reacting a metal compound with a reducing agent in the presence of a stabilizer in a reaction mixture comprising the metal compound, the reducing agent, and the stabilizer, wherein the reaction mixture is substantially free of solvent, to form a plurality of metal nanoparticles
Implementation Method 2
form a plurality of metal nanoparticles with molecules of the stabilizer on the surface of the metal nanoparticles
Implementation Method 3
heating the deposited composition to form conductive features on the substrate
Data Source
AI summary
A method of forming conductive features on a substrate, the method includes reacting a metal compound with a reducing agent in the presence of a stabilizer in a reaction mixture comprising the metal compound, the reducing agent, and the stabilizer, wherein the reaction mixture is substantially free of solvent, to form a plurality of metal nanoparticles with molecules of the stabilizer on the surface of the metal nanoparticles. After isolating the plurality of metal nanoparticles, a liquid composition that includes a polymeric binder, a liquid and the plurality of metal nanoparticles with molecules of the stabilizer on the surface of the metal nanoparticles is deposited on a substrate by a liquid deposition technique to form a deposited composition. The deposited composition is then heated to form conductive features on the substrate.