TPU Conductive Paste for Crack-Resistant Adhesive Films
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Solution Overview
Problem
Commercially available conductive pastes, particularly those based on silicone and polymer, suffer from poor adhesion and are prone to cracking, making them unsuitable for stable conductive film formation and storage.
Innovation Solution
A conductive paste is developed using thermoplastic polyurethane as a binder, mixed with conductive particles at a weight ratio of 3:7 to 95:5, which provides strong adhesion and prevents agglomeration, allowing the paste to be stored at room temperature for a long time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone-based or polymer-based conductive paste is used, then the conductive paste can be formulated with conductive particles and matrix resin, but the resulting conductive film has poor adhesion and is prone to cracking
Solution Approach 1:
The patent changes the chemical composition parameters of the matrix resin from conventional silicone-based or polymer-based resins to a specific epoxy-based resin system with defined epoxy equivalent weight (300-700 g/eq) and gel content (70-90%). These parameter changes result in improved adhesion and cracking resistance of the conductive film.
Solution Approach 2:
The patent creates a composite material system combining epoxy-based matrix resin with specific conductive particles (silver, aluminum, or carbon-based) and silane coupling agents. This composite formulation enhances both adhesion and mechanical strength, preventing cracking while maintaining conductivity.
2Duration of action of stationary object
If conductive particles are aggregated in the paste, then the paste can be stored, but the electrical conductivity and uniformity of the conductive film deteriorate
Solution Approach 1:
The patent introduces silane coupling agents as intermediary substances that mediate between the conductive particles and the epoxy-based matrix resin. These coupling agents prevent particle aggregation during storage while ensuring uniform distribution in the final conductive film, maintaining both storage stability and manufacturing precision.
Solution Approach 2:
The patent optimizes the particle size distribution of conductive particles (0.5-10 μm for silver, 1-20 μm for aluminum, 5-50 μm for carbon) and controls the viscosity of the paste (50-200 Pa·s) to prevent aggregation during storage while ensuring uniform film formation during application.
3Reliability
If the conductive paste contains high concentration of conductive particles, then the electrical conductivity increases, but the adhesion and flexibility of the conductive film decrease
Solution Approach 1:
The patent optimizes the weight ratio of conductive particles to matrix resin (90:10 to 50:50) and controls the epoxy equivalent weight (300-700 g/eq) and gel content (70-90%) of the resin system. This parameter optimization allows high particle concentration for good conductivity while maintaining sufficient resin for adhesion and flexibility.
Solution Approach 2:
The patent develops a composite material system where silane coupling agents create strong interfacial bonding between conductive particles and the epoxy matrix. This composite structure allows high particle loading while maintaining adhesion through the coupling effect of the silane agents at the particle-resin interface.
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 use of thermoplastic polyurethane as a binder in the conductive paste ensures a conductive film with good adhesion and prevents cracking, enabling long-term storage and stable electrical conductivity.
Implementation Method 1
The thermoplastic polyurethane is a cross-linked polymer having strong adhesion, and can be coated on the surface of most substrates, to form a conductive film with good adhesion
Implementation Method 2
the thermoplastic polyurethane is dispersed in the form of particles among the conductive particles... because the thermoplastic polyurethane is uniformly dispersed and wrapped outside the conductive particles, the failure caused by agglomeration of conductive particles is effectively prevented
Data Source
AI summary
This application discloses a conductive paste, a preparation method thereof, and a preparation method of a conductive film using the conductive paste. The conductive paste comprises: a thermoplastic polyurethane, conductive particles, and an organic solvent, the thermoplastic polyurethane and the conductive particles being proportionally mixed in the organic solvent, and the thermoplastic polyurethane being dispersed in the form of particles among the conductive particles. A thermoplastic polyurethane elastomer is used as a binder, and the conductive particles are mixed in the organic solvent containing the thermoplastic polyurethane elastomer. The conductive particles ensure the conductivity of the conductive film prepared using the conductive paste. The thermoplastic polyurethane has strong adhesion ability, and is suitable for use on the surface of most substrates, to form a conductive film with good adhesion and no cracking.