Silver Particle Synthesis for Low-Temperature Conductive Paste
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Solution Overview
Problem
Conductive pastes with silver micro-particles produced by traditional methods require high sintering temperatures to achieve low resistivity, which is not suitable for applications with low thermal resistivity limits, and suffer from poor packability due to non-uniform particle diameters and shapes.
Innovation Solution
A method for synthesizing silver particles with specific diameter distributions, including polyhedral shapes, by reacting silver compounds with polyalcohols in a controlled liquid phase process, allowing for improved packability without the need for high-temperature sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional atomizing method and flattening processing are used to produce silver micro-particles, then resistivity can be reduced to the order of 10^-6 Ω·cm, but sintering temperature must be maintained at high levels (above 200°C) which is not suitable for low thermal resistivity applications
Solution Approach 1:
The invention changes the particle morphology parameter from flattened shapes to polyhedral shapes with specific crystal orientations. This parameter change enables low resistivity (10^-5 Ω·cm) to be achieved at lower sintering temperatures (150°C), resolving the contradiction between resistivity and sintering temperature requirements for low thermal resistivity applications.
Solution Approach 2:
The invention creates silver particles with specific local crystal orientations and polyhedral shapes that optimize electrical conductivity at particle contact points. This local quality optimization allows achieving sufficient conductivity at lower sintering temperatures, avoiding the need for high-temperature processing that would damage low thermal resistivity substrates.
2Reliability
If traditional atomizing method is used to produce silver micro-particles, then resistivity can be reduced, but packability deteriorates due to non-uniform particle diameters and shapes
Solution Approach 1:
The invention controls and standardizes particle morphology parameters by producing polyhedral shapes with consistent crystal orientations. This parameter control achieves both good packability (uniform particle sizes and shapes) and low resistivity, resolving the contradiction between these two requirements.
Solution Approach 2:
The invention creates composite structures at the particle level by forming polyhedral silver particles with specific crystal orientations that optimize both packing efficiency and electrical conductivity. This composite approach achieves uniform particle characteristics for good packability while maintaining low resistivity.
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 method achieves conductive pastes with silver particles that exhibit improved packability and low resistivity even at lower sintering temperatures, suitable for applications with low thermal resistivity limits, enhancing bonding strength and conductivity.
Implementation Method 1
synthesizing second silver particles (P2) and third silver particles (P3) by causing a reaction between a first silver compound (C2) and a first reductant (R2) in a liquid phase
Implementation Method 2
the first reductant (R2) is a first polyalcohol (PA2), in the synthesizing the second silver particles (P2), the second silver particles (P2) and the third silver particles (P3) are synthesized by heating the first polyalcohol (PA2) in which the first silver compound (C2) is dissolved
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
A silver particle synthesizing method includes reducing a dispersant from first silver particles each covered with the dispersant to obtain second silver particles. The method further includes synthesizing third silver particles each having a larger particle diameter than the second silver particles by causing a reaction between a silver compound and a reductant in a liquid phase containing the second silver particles.