Conductive Paste Composition for Crack-Resistant Flexible Circuits
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Solution Overview
Problem
Existing conductive pastes for forming electric and electronic circuit wirings on stretchable and bendable materials face issues with breaking during thermal molding due to deformation, particularly when using thermoplastic polyurethane resins.
Innovation Solution
A conductive composition comprising conductive particles, a thermoplastic resin with a glass transition temperature of 140 to 200°C, preferably polycarbonate resin, and a solvent with a boiling point of 200°C or more, such as isophorone, is used to form electric wirings that can withstand stretching and bending without breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conductive paste containing thermoplastic polyurethane resin is used to form electric wiring on stretchable base material, then the wiring can be formed on flexible substrate, but the wiring cracks and breaks during thermal molding due to deformation
Solution Approach 1:
The patent changes the glass transition temperature parameter of the thermoplastic resin from below 100°C (conventional polyurethane) to 100°C or higher. This parameter change fundamentally alters the resin's thermal behavior, making it resistant to softening and cracking during thermal molding processes while maintaining flexibility at lower temperatures. The specific requirement of Tg ≥ 100°C directly addresses the contradiction by selecting a resin that remains structurally stable during molding heat exposure.
Solution Approach 2:
The patent creates a composite conductive paste system combining conductive particles (silver, copper, or carbon) with a specific thermoplastic resin having Tg ≥ 100°C. This composite structure leverages the conductivity of metal/carbon particles while the high-Tg resin matrix provides thermal stability and crack resistance during deformation. The synergistic combination resolves the contradiction between flexibility and breaking resistance.
2Ease of manufacture
If thermal molding is performed on electric wiring pattern formed with conventional conductive paste, then the base material can be shaped, but the thin wire pattern cracks and breaks
Solution Approach 1:
The patent raises the glass transition temperature parameter of the resin to 100°C or higher, which fundamentally changes the material's response to thermal molding temperatures. Conventional resins with Tg < 100°C soften and cause thin wiring to crack during molding, but the high-Tg resin maintains structural integrity, enabling successful thermal molding of thin wire patterns without strength degradation.
3Ease of operation
If conductive paste with low glass transition temperature resin is used, then the wiring remains flexible at low temperature, but the wiring breaks during stretching and bending due to lack of thermal stability
Solution Approach 1:
The patent optimizes the glass transition temperature parameter to 100°C or higher, creating a threshold effect where the resin remains flexible below Tg but maintains structural stability above Tg. This parameter optimization resolves the contradiction by ensuring the wiring stays operable and flexible during normal use while resisting breaking during deformation and thermal processing.
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 allows for the formation of electric wirings with a low likelihood of breaking, even when subjected to stretching and bending, and enables molding without cracking, suitable for In-Mold Electronics applications.
Implementation Method 1
a glass transition temperature of the thermoplastic resin (B) is 140 to 200 degrees C.
Data Source
AI summary
A conductive composition includes conductive particles, a thermoplastic resin, and a solvent, wherein a glass transition temperature of the thermoplastic resin is 140 to 200 degrees C.