Ink Composition for Thermal Shock Resistant Sintered Joints
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Solution Overview
Problem
The conductive paste disclosed in existing technologies experiences a decrease in joint strength of sintered bodies (conductive wires, joint structures, etc.) due to thermal shock, particularly across a temperature range of -50 to 200°C.
Innovation Solution
An ink composition containing metal particles with specific particle size ranges and mass ratios, including metal nanoparticles (1-100 nm), metal sub-microparticles (101-1000 nm), and metal microparticles (1001-10000 nm), where the mass ratio of metal microparticles to metal sub-microparticles is less than 1.00, and the content of metal nanoparticles is 8 mass% or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive paste is used, then the joint strength is initially adequate, but the joint strength decreases significantly under thermal shock conditions
Solution Approach 1:
The patent segments the metal particles into three distinct size categories: nanoparticles (1-100 nm), sub-microparticles (101-1000 nm), and microparticles (1001-10000 nm). Each size category serves a specific function in the sintered body structure, with the segmented particle size distribution enabling the joint to withstand thermal shock while maintaining strength. The nanoparticles fill voids and create strong bonds, sub-microparticles provide structural framework, and microparticles contribute to overall connectivity.
Solution Approach 2:
The patent changes the critical parameter of particle size distribution by specifying precise ranges for three different particle size categories and their respective content ratios (nanoparticles: 8-50 mass%, sub-microparticles: 40-85 mass%, microparticles: 5-30 mass%). This parameter optimization ensures that the sintered body maintains adequate joint strength before and after thermal shock, resolving the contradiction between initial strength and thermal shock resistance.
2Strength
If metal particle content is increased to maintain joint strength, then the joint strength is maintained, but the material becomes more prone to void formation and defects
Solution Approach 1:
The patent applies local quality by assigning different functions to different particle size regions within the sintered body. Nanoparticles (1-100 nm) with high surface area to volume ratio are distributed throughout to fill voids and create strong inter-particle bonds in critical regions. Sub-microparticles (101-1000 nm) form the structural framework, and microparticles (1001-10000 nm) provide connectivity. This localized functional assignment eliminates voids while maintaining strength without requiring excessive metal particle content.
Solution Approach 2:
The patent creates a composite metal particle system combining three different particle size ranges in optimized proportions (nanoparticles: 8-50 mass%, sub-microparticles: 40-85 mass%, microparticles: 5-30 mass%). This composite structure leverages the advantages of each particle size: nanoparticles for void elimination and bond strength, sub-microparticles for structural integrity, and microparticles for connectivity. The composite approach achieves both high joint strength and void-free structure simultaneously.
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 ink composition effectively suppresses the decrease in joint strength of sintered bodies due to thermal shock, maintaining high joint strength even after exposure to extreme temperature fluctuations.
Implementation Method 1
a conductive paste containing conductive particles and an organic solvent is applied onto an insulating substrate by a printing method, and then sintered, thereby producing a conductive wire
Data Source
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AI summary
To provide an ink composition that can form a sintered body (conductive wire, joint structure, or the like) capable of suppressing a decrease in joint strength due to thermal shock. An ink composition containing metal particles and a solvent, wherein the metal particles contain metal nanoparticles having a particle size of from 1 to 100 nm, metal sub-microparticles having a particle size of from 101 to 1000 nm, and metal microparticles having a particle size of from 1001 to 10000 nm; a mass ratio of the metal microparticles to the metal sub-microparticles (micro/sub-micro) is less than 1.00; and a content of the metal nanoparticles in the metal particles is 8 mass% or more.