Non-spherical Silver Paste for High-Conductivity Sintering
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Solution Overview
Problem
Existing silver pastes with spherical silver particles face issues of insufficient sintering, leading to low strength, electrical conductivity, and thermal conductivity in solid silver, and increased viscosity which decreases workability, especially with high-performance chip components generating more heat.
Innovation Solution
A pasty silver particle composition comprising non-spherical silver particles with an average diameter of 0.1 to 18 µm, a carbon content of 1.0 weight % or less, and a volatile dispersion medium, where the silver particles are flake-like or granular and partially coated with higher fatty acids, allowing for effective sintering at 100°C to 400°C to achieve strong, conductive solid silver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of silver particles is increased to improve electrical conductivity and thermal conductivity, then conductivity is improved, but the viscosity of the electrically conductive paste increases significantly, decreasing workability
Solution Approach 1:
The invention changes the shape parameter of silver particles from spherical to non-spherical (flake-like or irregular), which fundamentally alters the packing behavior and viscosity characteristics of the paste. This parameter change allows high silver content (improving conductivity) while maintaining acceptable viscosity (workability) because non-spherical particles create different flow dynamics compared to spherical particles
Solution Approach 2:
The invention uses composite material formulation by combining non-spherical silver particles with specific organic vehicle compositions and dispersants. This composite approach allows optimization of both conductivity (through high silver content) and workability (through the composite matrix that manages viscosity)
2Manufacturing precision
If spherical silver powder is used to produce electrically conductive paste with high density and precision, then manufacturing quality is improved, but sintering is insufficient leading to low strength and conductivity in solid silver
Solution Approach 1:
The invention applies asymmetry by using non-spherical (flake-like or irregular) silver particles instead of spherical particles. This asymmetric shape creates better interparticle contact areas and bonding interfaces during sintering, enabling sufficient sintering at lower temperatures while maintaining manufacturing precision. The irregular shapes allow particles to interlock and bond more effectively, resolving the contradiction between precision and sintering quality
3Ease of manufacture
If conventional silver powder is heated for sintering, then solid silver is produced, but sintering is insufficient resulting in unexpectedly low strength, electrical conductivity, and thermal conductivity
Solution Approach 1:
The invention changes multiple parameters simultaneously: particle shape (non-spherical), particle size distribution (0.5-10 μm), and surface characteristics (controlled carbon content ≤1.0%). These parameter changes enable effective sintering at conventional temperatures (100-400°C) while achieving high reliability in the sintered product. The specific carbon content control prevents excessive carbon formation that would hinder sintering while maintaining particle stability
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 composition enables strong, highly conductive solid silver with improved sintering properties, suitable for joining metal members and producing printed wiring boards with excellent wear resistance, adhesive properties, and high thermal conductivity.
Implementation Method 1
a volatile dispersion medium, wherein the volatile dispersion medium is volatilized and the non-spherical silver particles are sintered by heating
Implementation Method 2
the non-spherical silver particles are sintered by heating
Data Source
Figure 1~2
AI summary
[PROBLEMS] To provide a pasty silver particle composition, which, upon heating, allows silver particles to be easily sintered to form solid silver possessing excellent strength, electric conductivity and thermal conductivity, and a production process of solid silver and the like. [MEANS FOR SOLVING PROBLEMS] A pasty silver particle composition comprising nonspherical silver particles having an average particle diameter of 0.1 to 18 µm and a carbon content of not more than 1.0% by weight and a volatile dispersion medium, wherein, upon heating, the volatile dispersion medium is volatilized and the nonspherical silver particles are sintered to one another to form solid silver. There are also provided a process for producing solid silver comprising heating the pasty silver particle composition, solid silver having excellent strength, electric conductivity and thermal conductivity, a method for joining a metallic member using the pasty silver particle composition, and a production process of a printed wiring board comprising silver wiring.