Conductive Paste Composition for Stable Discharge and Void Suppression
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Solution Overview
Problem
Conductive pastes using ether-based solvents tend to float up in dispensing devices, leading to unstable discharge, and those with multiple solvents suffer from storage and discharge stability issues, while highly polar solvents generate voids during sintering and reduce bonding strength.
Innovation Solution
A conductive paste containing specific metal nanoparticles coated with an amine-based organic protective agent and dispersed in a mixture of three organic solvents with defined boiling points and Hansen solubility parameters, ensuring stability during continuous discharge and storage, and suppressing void formation during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ether-based solvent is used in conductive paste, then printing can be performed without unevenness and high bonding strength can be achieved, but the solvent floats up in dispensing device leading to unstable discharge
Solution Approach 1:
The patent changes the physical-chemical parameters of the dispersion medium by selecting specific solvents with controlled boiling points (200-350°C) and Hansen solubility parameters. This parameter optimization prevents solvent float-up in dispensing devices while maintaining printing uniformity and bonding strength.
Solution Approach 2:
The patent uses a composite dispersion medium comprising three specific organic solvents mixed together. This composite solvent system combines the advantages of individual solvents to achieve both stable discharge from dispensing devices and high bonding strength after sintering, while preventing printing unevenness.
2Reliability
If highly polar solvent is used instead of low polar solvent, then discharge stability is improved, but voids are generated during sintering and bonding strength decreases
Solution Approach 1:
The patent optimizes the polarity parameters of the dispersion medium by carefully selecting three organic solvents with specific Hansen solubility parameters and boiling points. This balanced parameter selection achieves both discharge stability and high bonding strength without void formation during sintering.
Solution Approach 2:
The patent creates a locally optimized dispersion medium where each of the three solvents plays a specific role: one provides discharge stability, another prevents void formation, and the third ensures bonding strength. This local quality differentiation within the composite solvent system resolves the contradiction.
3Manufacturing precision
If two or more types of solvents are used in conductive paste, then printing performance is improved, but storage stability deteriorates due to metal particle and solvent separation
Solution Approach 1:
The patent uses a specifically designed composite dispersion medium of three organic solvents that are mutually miscible and maintain stable metal particle suspension. This composite solvent system improves printing performance while preventing phase separation during storage, resolving the stability contradiction.
Solution Approach 2:
The patent changes the compositional parameters of the dispersion medium by selecting solvents with complementary properties and specific ratios. This optimized composition maintains homogeneous metal particle distribution during storage while enabling high-quality printing performance.
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 conductive paste achieves stable discharge and storage, preventing voids in sintered bodies, resulting in high bonding strength for conductive wirings and bonded structures.
Implementation Method 1
metal nanoparticles (A) are coated on surfaces thereof with an organic protective agent containing an amine
Implementation Method 2
a conductive paste containing conductive particles and an organic solvent is applied onto an insulating substrate by a printing method, and then sintered, thereby manufacturing a conductive wiring
Data Source
AI summary
Provided is a conductive paste for bonding which is excellent in stability during continuous discharge and storage stability and can suppress generation of voids during formation of a sintered body. The conductive paste for bonding contains: metal nanoparticles (A) having an average particle size of 1 nm or more and less than 100 nm; and a dispersion medium containing an organic solvent (a), an organic solvent (b), and an organic solvent (c); wherein the metal nanoparticles (A) are coated on surfaces thereof with an organic protective agent containing an amine and dispersed in the dispersion medium, and the organic solvents (a) to (c) are different compounds and satisfy the following formulas (1) to (6): 150° C.≤Ta≤250° C. (1); 150° C.≤Tb≤250° C. (2); 250° C.≤Tc≤350° C. (3); δa≥10.0 (4); δc≤9.0 (5); δc≤δb≤δa (6), where Ta to Tc represent boiling points of the organic solvents (a) to (c), respectively, and δa to δc represent Hansen solubility parameters of the organic solvents (a) to (c), respectively.