Conductive Paste Flexibility via Metal Capture Agent
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Solution Overview
Problem
Conductive pastes and films derived from existing technologies suffer from inadequate flexibility and bending resistance, particularly when thickened, and often fail to form coherent coatings due to issues like flocculation during imidization.
Innovation Solution
A conductive paste comprising conductive particulates, a metal capture agent, and a polyimide precursor solution is developed, where the conductive particles are dispersed within a polyimide resin, allowing for high flexibility and adhesiveness, even at thicker film thicknesses (50 µm to 125 µm), achieved through specific formulations and processing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silver-containing conductive paste is used to improve conductivity, then electrical conductivity is improved, but flexibility and bending resistance deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of silver micropowder (conductive component) combined with polyamide-imide resin and poly(ether ether ketone) resin (binder components). This composite structure allows the conductive paste to maintain high electrical conductivity from the silver particles while the polymer resin matrix provides flexibility and bending resistance, resolving the contradiction between conductivity and mechanical strength.
2Reliability
If the film thickness is increased to improve conductivity, then electrical conductivity is improved, but flexibility and bending resistance deteriorate
Solution Approach 1:
The patent employs a composite formulation where silver micropowder provides conductivity pathways while the combination of polyamide-imide and poly(ether ether ketone) resins creates a flexible matrix. This composite structure enables the formation of thick films (improving conductivity) while maintaining flexibility and bending resistance through the elastomeric properties of the resin system.
Solution Approach 2:
The patent modifies the chemical composition parameters of the binder resin system by selecting specific polymer types (polyamide-imide and poly(ether ether ketone)) with appropriate molecular weights and glass transition temperatures. These parameter changes allow the material to maintain flexibility even at increased film thicknesses, resolving the contradiction between thickness for conductivity and flexibility.
3Temperature
If imidization is progressed to improve heat resistance, then heat resistance is improved, but the paste becomes flocculent and coating formation fails
Solution Approach 1:
The patent performs preliminary dispersion of silver micropowder in the binder resin system before imidization occurs. This preliminary action ensures homogeneous distribution of conductive particles throughout the resin matrix, preventing flocculation during subsequent imidization and heat treatment while maintaining paste stability and coating formability.
Solution Approach 2:
The patent controls the imidization process parameters including temperature profile, heating rate, and atmospheric conditions to prevent excessive flocculation. By optimizing these parameters, the paste maintains homogeneity and coating formability while achieving the desired heat resistance through controlled imidization of the polyimide precursor.
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 resulting conductive coatings or films exhibit superior flexibility, heat resistance, and mechanical properties, maintaining conductivity and adhesiveness, suitable for various applications including printed wiring boards and electromagnetic shielding.
Implementation Method 1
a polyimide precursor solution... where the conductive particles are dispersed within a polyimide resin
Implementation Method 2
a metal capture agent, and a polyimide precursor solution is developed, where the conductive particles are dispersed within a polyimide resin
Data Source
AI summary
The task of the present invention is to offer a conductive paste that can be molded into a conductive coating or film that can maintain flexibility and ductility even while possessing a thickness of 50 µm ∼ 125 µm. The conductive paste of the present invention includes a conductive particulate, a metal capture agent and a polyimide precursor solution. The metal capture agent can be selected as at least one from among either pyrimidinethiol compounds, triazinethiol compounds and imidazole compounds with a mercapto group. Moreover, the conductive particulate is preferably a core particle that is covered with a metal shell. In addition, a polyamic acid solution is preferred as the polyimide precursor solution.