Silver Particle Wiring for Repetitive Bending on Flexible Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conductive sheets used in foldable devices, such as smartphones and wearable devices, face challenges in maintaining electrical characteristics and durability during repetitive bending deformations, especially with small curvature radii, as conventional metal pastes and wirings lack sufficient bending resistance.
Innovation Solution
A metal wiring with a sintered body of silver particles is developed, optimized for hardness and Young's modulus, with specific particle size and distribution ranges, and a conductive sheet formed on a flexible substrate to enhance bending resistance and maintain electrical properties during repetitive bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal paste is used to form metal wiring on flexible substrate, then the wiring can be formed with simple process, but the wiring lacks sufficient bending resistance and electrical characteristics change during repetitive bending
Solution Approach 1:
The patent uses a composite structure consisting of a flexible substrate and a metal wiring layer formed by sintering metal particles. The metal particles are dispersed in a binder resin matrix, creating a composite material that combines the flexibility of the substrate with the conductivity of the metal network. This composite structure maintains electrical characteristics during bending while remaining relatively simple in fabrication process.
2Reliability
If metal wiring is made softer to improve bending resistance, then the wiring can withstand repetitive bending better, but the wiring strength decreases
Solution Approach 1:
The patent optimizes the physical and chemical parameters of the metal particles and binder resin to achieve the desired balance between bending resistance and strength. Specifically, the metal particle size, shape, and concentration are controlled, along with the binder resin's molecular weight and functional groups. These parameter adjustments create a wiring that is soft enough to bend repeatedly without breaking while maintaining sufficient structural 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 metal wiring exhibits excellent bending resistance and minimal change in electrical characteristics even under severe repetitive bending deformations with small curvature radii, ensuring durability and reliability in foldable devices.
Implementation Method 1
After applying the metal paste to a substrate, the resultant is heated and calcinated to sinter the metal particles, and thus, a conductive wiring/electrode is formed.
Data Source
AI summary
The present invention relates to a metal wiring, to be formed on a flexible substrate, including a sintered body of silver particles. The sintered body constituting the metal wiring has a volume resistivity of 20 μΩ·cm or less, hardness of 0.38 GPa or less, and a Young's modulus of 7.0 GPa or less. A conductive sheet provided with the metal wiring can be produced by applying/calcinating, on a substrate, a metal paste containing, as a solid content, silver particles having prescribed particle size and particle size distribution, and further containing, as a conditioner, an ethyl cellulose having a number average molecular weight of 10,000 or more and 90,000 or less. The metal wiring of the present invention is excellent in bending resistance with change in electrical characteristics suppressed even through repetitive bending deformation.