Particle-Free Silver Ink for Low-Temperature Sintering
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Solution Overview
Problem
Current inkjet printing technologies face challenges with nozzle clogging, high sintering temperatures, and surface oxidation issues, particularly with silver and constantan inks, which limit high-resolution printing and safety concerns due to the need for flammable reducing gases.
Innovation Solution
Development of particle-free silver ink using silver salt complexes and a chemical reduction process, and a constantan particle suspension ink with a chemical reduction sintering method to avoid nozzle clogging and achieve low-temperature sintering without flammable gases, utilizing surfactants and additives like sodium carboxymethyl cellulose and thiourea dioxide to enhance film uniformity and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nanoparticle based ink is used for printing, then electrical conductivity is improved, but nozzle clogging occurs during printing
Solution Approach 1:
The patent uses an organic solvent as an intermediary carrier to dissolve silver salts, replacing direct nanoparticle suspension. This mediator enables the ink to flow through nozzles without clogging while still delivering silver material that forms conductive paths after thermal decomposition.
Solution Approach 2:
The patent changes the physical state of silver from solid nanoparticles to dissolved silver salt complexes in organic solvent. This parameter change transforms the ink from a suspension that clogs nozzles to a solution that flows freely, while maintaining the ability to form conductive silver patterns through thermal decomposition.
2Reliability
If silver and constantan nanoparticle inks are used, then electrical conductivity is improved, but high sintering temperature is required
Solution Approach 1:
The patent changes the chemical form from metallic nanoparticles to organic-soluble silver salts and constantan complexes. This parameter change enables low-temperature thermal decomposition that forms conductive patterns without requiring high-temperature sintering, thus reducing the temperature parameter while maintaining electrical conductivity.
Solution Approach 2:
The patent replaces the mechanical sintering process (high-temperature particle bonding) with chemical decomposition and reduction processes. The organic-soluble precursors decompose thermally at lower temperatures to form conductive metal patterns, substituting the high-temperature mechanical sintering mechanism with a lower-temperature chemical transformation mechanism.
3Reliability
If constantan based ink is used for printing, then thermoelectrical properties are improved, but surface oxidation occurs
Solution Approach 1:
The patent uses organic solvents and complexing agents as intermediaries to deliver constantan material. This intermediary approach allows constantan to be deposited from solution without direct exposure to oxidizing environments during printing, and the organic matrix protects the deposited material from surface oxidation.
Solution Approach 2:
The organic-soluble constantan complex creates a protective environment during deposition and drying. The organic solvent and complexing agents form an inert-like atmosphere that prevents oxygen from reaching and oxidizing the constantan surface during the printing and drying process.
4Reliability
If constantan is sintered at high temperature, then electrical conductivity is improved, but flammable reducing gas is required
Solution Approach 1:
The patent replaces the high-temperature sintering process requiring flammable reducing gas with low-temperature thermal decomposition of organic-soluble precursors. This substitution eliminates the need for hazardous reducing gas atmospheres by using inherent organic reducing agents in the precursor molecules that decompose safely at lower temperatures.
Solution Approach 2:
The patent uses disposable organic solvent and complexing agent molecules that decompose during low-temperature processing. These short-living organic intermediaries provide the reducing environment needed for constantan formation without requiring external flammable gas supplies, eliminating safety hazards while enabling conductive pattern formation.
5Manufacturing precision
If particle-free silver ink is used, then high resolution printing is achieved, but film uniformity needs improvement
Solution Approach 1:
The patent uses organic complexing agents as intermediaries to control silver ion distribution and deposition. These intermediaries ensure uniform dissolution and controlled decomposition of silver salts, producing uniform silver films while maintaining the particle-free high-resolution printing capability.
Solution Approach 2:
The patent optimizes the chemical parameters of the organic-soluble silver salt complexes, including molecular structure, solubility, and decomposition temperature. These parameter changes enable controlled decomposition that produces uniform silver film thickness and composition while maintaining the particle-free formulation for high-resolution printing.
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 solutions enable high-resolution, flexible, and conductive patterns with lower sintering temperatures, reducing the risk of nozzle clogging and eliminating the need for hazardous reducing gases, resulting in improved electronic conductivity and adhesion of silver and constantan films.
Implementation Method 1
Chemical reduction makes denser silver film than thermal decomposition caused by volume shrinkage of silver precursor decomposition after thermal sintering. The resistivity of silver patterns made by chemical reduction is also lower than made by thermal decomposition because of less porosity.
Implementation Method 2
Thermal decomposition and chemical reduction of silver salts are two methods disclosed for particle-free silver ink. Thermal decomposition caused by volume shrinkage of silver precursor decomposition after thermal sintering.
Implementation Method 3
NP based ink requires a high sintering temperature to join particles. The sintering process of constantan usually requires a reducing atmosphere which is flammable gas, for instance hydrogen and methane.
Implementation Method 4
Addition of a surfactant additive further makes the silver film more uniform and easier to be sintered.
Implementation Method 5
A new chemical reducing sintering (CRS) is used to eliminate oxidation layers and sinter the constantan at low temperature.
Implementation Method 6
By using the functional fluid, inkjet printing technology is a promising method to deposit metallic nanoparticles on polymer substrate with designed patterns
Data Source
AI summary
A chemical process to formulate conductive ink with low sintering temperature for inkjet printing is described and shown. The application of fabricated flexible conductive film on lithium ion batteries is also described. This chemical method and composition can remove the oxidation on metallic nanoparticle surface during ink fabrication and sintering processes. Etched metallic ions in the conductive ink are reduced and particles bridged while annealing printed patterns to achieve low temperature sintering at about 350° C. The chemical process can be applied on nickel materials that are excellent current collectors for lithium ion batteries due to high chemical stability especially at high charging-discharging potential of less than 3 Volts. Thermal decomposition and chemical reduction of silver salts are two methods disclosed for particle-free silver ink. Surfactant additive further make silver film more uniform and easier to be sintered.