Electroconductive Silver Paste with Nitrile Rubber for Stretchable Electronics
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Solution Overview
Problem
Current electroconductive materials struggle with stability during long-term storage, anti-migration properties, and achieving a balance between high stretchability and low resistance, particularly in flexible electronics and wearable devices, where they often fail to maintain conductivity and adhesion during repetitive expansion and contraction.
Innovation Solution
An electroconductive silver paste is developed with a specific composition of amorphous or flaky silver powder and nitrile group-containing rubber, with a controlled ratio and low alkali metal content, forming an electroconductive network that maintains conductivity and stretchability, and is stable over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroconductive silver paste is used, then it provides basic conductivity, but it shows instability during long-term storage and poor anti-migration property
Solution Approach 1:
The patent changes the chemical composition parameters of the rubber binder by strictly controlling alkali metal content to 4,000 ppm or less and specifying nitrile group content of 25% or more. This parameter control prevents degradation reactions during storage, achieving both long-term stability and anti-migration property without sacrificing conductivity
Solution Approach 2:
The patent creates a composite material system combining silver powder with specially formulated nitrile group-containing rubber with controlled alkali metal content. This composite structure provides synergistic effects where the rubber matrix stabilizes the silver particles, preventing migration while maintaining electrical conductivity over extended storage periods
2Reliability
If high silver powder content is used to achieve low resistance, then conductivity improves, but stretchability and extensibility deteriorate
Solution Approach 1:
The patent optimizes the silver powder to rubber binder ratio within the range of 77/23 to 90/10, finding the optimal balance point where sufficient silver content provides low resistance while adequate rubber content maintains stretchability. The specific chemical composition parameters of the rubber further enhance this balance
Solution Approach 2:
The patent develops a composite material where silver powder is dispersed in a specially formulated nitrile group-containing rubber matrix. This composite structure allows the silver particles to form conductive pathways while the rubber matrix provides elastic deformation capability, achieving both low resistance and high stretchability simultaneously
3Adaptability or versatility
If the electroconductive film is expanded to achieve stretchability, then extensibility improves, but specific resistance greatly increases and the film breaks
Solution Approach 1:
The patent modifies the rubber binder parameters, specifically nitrile group content (≥25%) and alkali metal content (≤4,000 ppm), to create a matrix that maintains its structural integrity and conductive network during expansion. This allows the film to stretch over 35% without breaking or experiencing excessive resistance increase
Solution Approach 2:
The patent creates a composite material structure where silver powder is embedded in a specially formulated rubber matrix that can undergo large elastic deformations. The composite maintains its integrity during expansion, allowing the conductive network to remain intact even at 35% or greater elongation
4Adaptability or versatility
If repetitive expansion and contraction are applied to achieve flexibility, then adaptability improves, but adhesion decreases and wiring breaks
Solution Approach 1:
The patent optimizes the rubber binder composition parameters, particularly nitrile group content and alkali metal content, to enhance the material's resistance to fatigue and adhesion maintenance during repetitive deformation. This allows the wiring to withstand repeated expansion and contraction cycles without breaking or delaminating
5Ease of manufacture
If alkali metal content is not controlled in the rubber, then manufacturing is easier, but stability upon storage and anti-migration property deteriorate
Solution Approach 1:
The patent establishes a specific parameter threshold for alkali metal content (≤4,000 ppm) in the rubber binder, balancing manufacturing feasibility with performance requirements. This controlled parameter level prevents harmful chemical reactions during storage while remaining achievable through standard manufacturing processes
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 paste achieves a specific resistance of less than 1.0×10−3 Ω·cm, an elongation at break of over 35%, and repetitive stretchability without breaking, even after 50 cycles, while maintaining stability during long-term storage, thus addressing the limitations of existing materials.
Implementation Method 1
an electroconductive network is apt to be easily formed in spite of a low filling amount of the silver powder
Implementation Method 2
a rubber (B) containing a nitrile group... capable of forming an electroconductive film having an elongation at break of more than 35% and, when a repetitive stretchability is evaluated
Data Source
AI summary
The present invention provides an electroconductive paste which is excellent in a stability upon storage for a long period and in an anti-migration property, and capable of forming electrodes, wirings and sheets having a low resistance, an extensibility and a repetitive stretchability.An electroconductive silver paste, characterized in that, it contains a silver powder (A) and a rubber (B) containing a nitrile group, that a ratio by weight of (A)/(B) is within a range of from 77/23 to 90/10, that the silver powder (A) is an amorphous aggregated powder and/or a flaky powder, and that a content of an alkali metal in the nitrile group-containing rubber (B) is 4,000 ppm or less.