Inkjet Ink Composition for Low-Temperature Conductive Traces
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Solution Overview
Problem
Current methods for inkjet printing conductive traces face challenges such as unstable inkjetting, poor conductivity, and high temperature requirements, which limit the use of low-cost flexible substrates like paper and plastic, and result in low-resolution features with high resistivity.
Innovation Solution
An inkjet ink composition comprising polymer-capped metal nanoparticles, a monohydroxyl-substituted hydrocarbon, a polyol or monohydric ether, and water, with specific weight ratios, enables chemical sintering at room temperature, producing high-resolution conductive traces with low resistivity on various substrates without the need for surfactants or additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal sintering at high temperature (>200°C) is used to fuse metal nanoparticles, then high conductivity is achieved, but low-cost flexible substrates cannot be used due to thermal sensitivity
Solution Approach 1:
The patent changes the sintering mechanism from thermal to chemical by using chloride ions to replace the polymer capping agent. This parameter change allows sintering to occur at room temperature or low temperatures, enabling the use of flexible substrates while achieving high conductivity traces
Solution Approach 2:
The patent replaces the thermal sintering mechanism with a chemical sintering mechanism. Instead of using heat to fuse particles, chloride ions chemically facilitate the removal of capping agents and direct metal-metal bonding, enabling low-temperature processing compatible with flexible substrates
2Ease of manufacture
If conventional inkjet ink compositions are used, then printing can be performed, but unstable jetting, satellite production, and poor print quality occur
Solution Approach 1:
The patent optimizes the ink composition parameters by selecting specific solvents (water, ethanol, isopropanol) and controlling the concentration of metal nanoparticles and capping agents. These parameter changes achieve stable jetting properties and high-resolution printing while maintaining conductivity
Solution Approach 2:
The patent creates a composite ink composition combining metal nanoparticles, polymer capping agents, and specific solvents in optimized ratios. This composite formulation achieves both stable inkjetting behavior and high print quality with fine resolution features
3Reliability
If silver nanoparticles are used instead of copper, then oxidation resistance and conductivity are improved, but cost increases
Solution Approach 1:
The patent uses a small amount of silver nanoparticles with optimized concentration in the ink formulation. By reducing the quantity required through improved dispersion and sintering efficiency, the cost is reduced while maintaining the oxidation resistance and conductivity benefits of silver
4Temperature
If metal nanoparticles are reduced to nanoparticle dimensions, then sintering temperature is reduced, but reactive nature requires coating or capping to prevent oxidation
Solution Approach 1:
The patent uses polymer capping agents (PAA, PVA, PVP) as intermediaries that protect metal nanoparticles from oxidation during storage and printing, then facilitate chemical sintering when chloride ions are introduced. This intermediary approach enables low-temperature processing while preventing 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 inkjet ink composition achieves high-resolution, conductive traces with resistivity as low as 1.0×10^-7 Ωm on substrates like glossy paper, glass, and plastic, with stable jetting properties and excellent electrical performance, overcoming previous limitations of temperature and substrate compatibility.
Implementation Method 1
a low temperature chemical sintering method has been developed for the sintering of silver (Ag) nanoparticles (NPs)
Implementation Method 2
poly(acrylic acid) (PAA) capped Ag NPs can be chemically sintered by simple exposure to chloride ions to break the bonds between the PAA molecules and the metal nanoparticles
Implementation Method 3
The major parameters that affect drop performance and size are viscosity, density and surface tension
Data Source
Figure 1~2(c)
Figure 3
Figure 4(a)~4(b)
AI summary
Described herein is an inkjet ink composition for printing conductive traces. The inkjet ink composition comprises: polymer-capped metal nanoparticles; a first hydroxy compound, which is a monohydroxyl-substituted hydrocarbon comprising 1 to 6 carbon atoms; a second hydroxy compound, which is selected from a polyol, a monohydric ether and mixtures thereof; and water; wherein the weight ratio of water to first hydroxyl compound is in the range of 1:0.5 to 1:1.5; and wherein the weight ratio of water to second hydroxy compound is in the range of 1:0.5 to 1:1.5. Also described herein are a method of producing the inkjet ink composition and a method of printing conductive traces.