Silver Conductive Paste Composition for Nitrogen-Sintered Cu Bonding
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Solution Overview
Problem
Conventional electrically conductive pastes fail to provide sufficient bonding strength when bonding a Cu substrate or Cu electrode without a plating layer to electronic components, especially when sintered in a nitrogen atmosphere.
Innovation Solution
The use of a specific combination of silver powders with different particle size ranges and median diameters, including flake-like silver powder A, silver powder B, and silver powder C, optimized in terms of content and particle size distribution, to enhance bonding strength by filling gaps and improving sintering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electrically conductive paste is applied directly to Cu substrate or Cu electrode without plating layer and sintered in nitrogen atmosphere, then copper oxide formation is prevented, but bonding strength between Cu substrate and electronic components is insufficient
Solution Approach 1:
The invention changes the particle size parameters of silver powder to nanometer scale (10-190 nm, D50: 50-150 nm), which fundamentally alters the sintering behavior and bonding mechanism. The nanometer-scale particles provide significantly higher surface area and reactivity, enabling strong bonding in nitrogen atmosphere without copper oxide formation
Solution Approach 2:
The invention creates a composite paste system combining nanometer-scale silver powder with specific organic compounds (carboxylic acid and its derivative) that work synergistically. The organic compounds act as coupling agents that enhance the interfacial bonding between the silver particles and the Cu substrate, solving the bonding strength problem while maintaining the nitrogen atmosphere sintering process
2Ease of manufacture
If conventional electrically conductive paste is used for bonding Cu substrate without plating layer, then manufacturing process is simplified, but bonding strength is insufficient
Solution Approach 1:
The invention modifies the particle size parameter of silver powder from conventional micron scale to nanometer scale (10-190 nm), which fundamentally changes the paste's bonding capability. This parameter change enables strong bonding on unplated Cu substrates while maintaining the simplified manufacturing process without plating steps
Solution Approach 2:
The invention introduces organic compounds (carboxylic acid and its derivative) as intermediary substances that mediate the bonding interface between the nanometer-scale silver powder and the Cu substrate. These intermediaries enhance adhesion and bonding strength, allowing the simplified process to achieve reliable electrical connections
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 optimized silver powder combination achieves excellent bonding strength between the Cu substrate or Cu electrode and electronic components, even when sintered in a nitrogen atmosphere, without the need for a plating layer, ensuring strong and reliable electrical connections.
Implementation Method 1
the electrically conductive paste is sintered in nitrogen atmosphere instead of air atmosphere
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
An object of the present invention is to provide an electrically conductive paste having excellent bonding strength when bonded to an electronic substrate and the like, a laminated body, and a method for bonding a Cu substrate or Cu electrode to an electrical conductor. An electrically conductive paste comprising: a flake-like silver powder A having a particle size in the range of 1 µm or more and 15 µm or less and having a median diameter D50 of 2 µm or more and 5 µm or less; a silver powder B having a particle size in the range of 25 µm or more and 100 µm or less and having a median diameter D50 of 30 µm or more and 40 µm or less; a silver powder C having a particle size in the range of 10 nm or more and 190 nm or less and having a median diameter D50 of 50 nm or more and 150 nm or less; and a solvent, wherein the content of the silver powder C is more than 5.0 parts by mass and less than 90.0 parts by mass based on 100 parts by mass in total of the flake-like silver powder A, the silver powder B, and the silver powder C.