Silver Conductive Paste Composition for Stable Printing and Fast Sintering
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Solution Overview
Problem
Existing adhesive conductive pastes face challenges in forming accurate conductive wiring and joined structures with high joining strength, especially when sintered in inert gas atmospheres like nitrogen, due to viscosity fluctuations and residual non-conductive components, which affect conductivity and substrate integrity.
Innovation Solution
A conductive paste containing silver particles with two different particle sizes (1 nm to 100 nm and 0.1 μm to 10 μm) and a solvent represented by Formula (I) Ra—O—(X—O)n—Rb, where Ra and Rb are hydrocarbon groups, and n is an integer from 1 to 3, is used, which maintains suitable viscosity for printing and enhances conductivity without the need for thickeners, allowing for high-accuracy printing and strong substrate-electronic element connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conductive paste containing adhesive and thickener is used, then printing accuracy is improved, but residual non-conductive components remain after sintering, reducing conductivity
Solution Approach 1:
The invention extracts and removes the adhesive and thickener components from the conductive paste formulation. By eliminating these non-conductive substances, the paste achieves high printing accuracy through its inherent viscosity while ensuring excellent conductivity after sintering, as no residual non-conductive components remain to interfere with electrical performance.
Solution Approach 2:
The invention changes the physical and chemical parameters of the conductive paste by using a specific solvent system (alcohol-based) and optimizing the particle size distribution of silver particles (0.1-10 μm). This parameter optimization provides sufficient viscosity for accurate printing without requiring adhesive additives, thereby maintaining both printability and electrical conductivity.
2Reliability
If silver particles with average size ≥0.1 μm are used, then sintering in nitrogen atmosphere is difficult, but smaller particles improve sintering progress and joining strength
Solution Approach 1:
The invention segments the silver particle population into a specific size range (0.1-10 μm) that optimizes both sintering behavior and mechanical strength. This segmented particle size distribution enables effective sintering in nitrogen atmosphere while achieving high joining strength, resolving the contradiction between processability and reliability.
3Reliability
If alcohol solvent is used, then viscosity stability at printing temperature is poor, but conductivity after sintering is improved
Solution Approach 1:
The invention optimizes the alcohol solvent selection and combines it with controlled silver particle size distribution (0.1-10 μm) to achieve adequate viscosity stability for printing while maintaining excellent conductivity. The parameter optimization of particle size compensates for the inherent volatility of alcohol solvents.
4Stability of the object's composition
If ethylene glycol is used as solvent, then viscosity stability is improved, but joining strength with substrate is reduced
Solution Approach 1:
The invention extracts ethylene glycol from the solvent system and replaces it with alcohol solvents combined with optimized silver particle size distribution. This elimination of ethylene glycol prevents the joining strength problem while maintaining adequate viscosity stability through the alternative formulation approach.
Solution Approach 2:
The invention changes the solvent parameter from ethylene glycol to alcohol-based solvents and simultaneously optimizes the silver particle size distribution (0.1-10 μm). This dual parameter change achieves both adequate viscosity stability and high joining strength, resolving the contradiction between composition stability and mechanical strength.
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 paste achieves highly accurate and strong conductive wiring and joined structures with improved electrical characteristics and reduced substrate damage, even at lower sintering temperatures, by stabilizing viscosity and preventing non-conductive component residual issues.
Implementation Method 1
the substrate is then sintered, so as to manufacture a conductive wiring
Implementation Method 2
the compound represented by the Formula (I) is less likely to volatilize at a printing temperature, and a paste containing the compound represented by the Formula (I) as a solvent can suppress fluctuations in viscosity at the time of printing
Data Source
AI summary
An object of the present disclosure is to provide a paste that can suppress fluctuations in viscosity at a printing temperature to perform printing without unevenness, and is sintered fast even in an inert gas atmosphere such as nitrogen to form a highly accurate conductive wiring and a joined structure excellent in joining strength. The present disclosure provides an adhesive conductive paste for forming a conductive wiring and/or a joined structure to connect electronic elements, the adhesive conductive paste including a conductive particle and a solvent. The adhesive conductive paste contains, as the conductive particle, a silver particle (A) having an average particle size of 1 nm or greater and less than 100 nm and a silver particle (B) having an average particle size of 0.1 μm or greater and 10 μm or less, the silver particle (A) being a silver nanoparticle having a configuration in which a surface is coated with a protective agent containing amine, andthe adhesive conductive paste contains, as the solvent, a compound (C) represented by Formula (I) below:Ra—O—(X—O)n—Rb (I)where in Formula (I), Ra represents a monovalent group selected from a hydrocarbon group having from 1 to 6 carbon atom(s) and an acyl group, X represents a divalent group selected from a hydrocarbon group having from 2 to 6 carbon atoms, Rb represents a hydrogen atom or a monovalent group selected from a hydrocarbon group having from 1 to 6 carbon atom(s) and an acyl group, Ra and Rb may be the same, n represents an integer from 1 to 3.