Conductive Ink Formulation Using Hansen Solubility Parameters
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Solution Overview
Problem
Conductive inks and pastes using water or hydrophilic solvents face challenges with low metal particle dispersibility, leading to increased volume resistivity and reduced conductive properties due to residual solvents and dispersants after sintering.
Innovation Solution
The use of a conductive ink or paste containing metal nanoparticles, a water or hydrophilic solvent with a vapor pressure of 10 hPa or more, and an additive solvent selected based on Hansen solubility parameters, with specific ranges for distances Ra and Rb, to enhance dispersibility and sinterability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water or hydrophilic solvent is used as the dispersion medium, then environmental load is reduced, but metal particle dispersibility decreases
Solution Approach 1:
A dispersant comprising a polyhydric alcohol compound and a carboxylic acid compound is introduced as an intermediary substance between the metal particles and the water-based dispersion medium. The dispersant forms a protective layer around metal particles, improving their dispersibility and stability in the aqueous environment without compromising the environmental benefits of using water as the solvent.
Solution Approach 2:
The dispersion medium is formulated as a composite system combining water or hydrophilic solvent with specific polyhydric alcohol compounds and carboxylic acid compounds. This composite approach creates a synergistic effect where the combination of components provides both environmental compatibility and enhanced metal particle dispersibility that neither component could achieve alone.
2Stability of the object's composition
If high boiling point dispersion medium is used to improve dispersibility, then metal particle stability is improved, but sintering temperature cannot be reduced
Solution Approach 1:
The high boiling point components (polyhydric alcohol and carboxylic acid dispersants) are extracted or removed during the sintering process. The dispersants perform their function of maintaining metal particle stability during storage and application, but are designed to decompose and be eliminated at relatively low sintering temperatures, allowing the final sintered product to achieve low volume resistivity without requiring high sintering temperatures.
Solution Approach 2:
The chemical composition parameters of the dispersion medium are specifically selected to enable low-temperature sintering. The dispersants are chosen based on their decomposition characteristics, ensuring they break down at low temperatures to leave behind clean metal particle contacts. This parameter optimization allows the system to maintain stability during application but enable low-temperature processing during sintering.
3Stability of the object's composition
If non-volatile dispersant is used to maintain dispersibility, then metal particle dispersibility is improved, but volume resistivity increases due to residual dispersant
Solution Approach 1:
The dispersant compounds are specifically selected and formulated to decompose and volatilize during the sintering process, converting what would normally be harmful residues into beneficial vaporized products that leave no contaminating remnants. This approach transforms the potential harm of residual dispersants into the benefit of complete removal, achieving both good dispersibility during application and low volume resistivity after sintering.
Solution Approach 2:
The chemical parameters of the dispersant are optimized to ensure complete decomposition and removal during sintering. By selecting compounds with appropriate molecular weights, functional groups, and decomposition temperatures, the system achieves effective metal particle dispersibility during storage and application, while ensuring the dispersants are completely eliminated during sintering to prevent any increase in volume resistivity.
4Reliability
If conventional conductive ink formulation is used to achieve conductivity, then conductive property is improved, but low-temperature sinterability is reduced
Solution Approach 1:
The formulation parameters of the conductive ink are fundamentally changed by using water or hydrophilic solvents with specific vapor pressures, combined with dispersants having optimized molecular weights and decomposition characteristics. These parameter changes enable the metal particles to maintain good dispersibility and conductivity while allowing the organic components to decompose and remove at low temperatures, achieving both high conductive property and excellent low-temperature sinterability simultaneously.
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 approach results in conductive inks and pastes with improved conductive properties and excellent low-temperature sinterability, reducing volume resistivity and enhancing durability.
Implementation Method 1
a distance Ra between a Hansen solubility parameter of the metal nanoparticles and a Hansen solubility parameter of the additive solvent and a distance Rb between a Hansen solubility parameter of the water or the hydrophilic solvent and the Hansen solubility parameter of the additive solvent
Implementation Method 2
a water or a hydrophilic solvent having a vapor pressure of 10 hPa or more
Implementation Method 3
the substrate on which the pattern has been formed is heated to sinter the conductive ink or the conductive paste, thereby forming a wiring material or a joint material on the substrate
Data Source
AI summary
The present disclosure provides a conductive ink or a conductive paste having highly conductive property and excellent low-temperature sinterability. One aspect of the present disclosure relates to a conductive ink or a conductive paste containing metal nanoparticles, a water or a hydrophilic solvent having a vapor pressure of 10 hPa or more, and an additive solvent. A distance Ra between a Hansen solubility parameter of the metal nanoparticles and a Hansen solubility parameter of the additive solvent is in a range of from 2.5 to 13. A distance Rb between a Hansen solubility parameter of the water or the hydrophilic solvent and the Hansen solubility parameter of the additive solvent is 35 or less. Another aspect of the present disclosure relates to a method for producing the conductive ink or the conductive paste, and a method for selecting the additive solvent contained in the conductive ink or the conductive paste.