Conductive Paste Composition for Stretchable 3D Printed Circuits
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Solution Overview
Problem
Existing electrically conductive pastes used in forming three-dimensional circuit patterns suffer from disconnection during thermal stretching due to thermal deformation, particularly when forming complex shapes like domes or other 3D structures.
Innovation Solution
Utilizing aggregated silver particles with specific properties (0.1 to 3 µm primary particle diameter, 2 to 5 g/cm³ tap density, and 0.5 to 2.0 m²/g specific surface area) in an electrically conductive paste, which maintains electrical conductivity and adhesion to the substrate even under significant deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrically conductive paste with silver flakes is used for forming circuit patterns on resin substrates, then the circuit can be formed initially, but disconnection or detachment of wires occurs during thermal stretching when forming three-dimensional shapes
Solution Approach 1:
The invention changes the particle morphology parameter of the conductive filler from flaky to aggregated spherical shape, and optimizes the size parameter to 0.1-3 µm. This parameter change enables the conductive paste to maintain wire integrity during thermal stretching up to 135% deformation, resolving the disconnection problem while maintaining electrical conductivity
Solution Approach 2:
The invention creates a composite material system combining aggregated silver particles with specific binder resins and curing agents. This composite structure provides both mechanical adhesion to prevent detachment and electrical conductivity, solving the reliability issue during three-dimensional molding
2Ease of manufacture
If silver powder in flakes is used in electrically conductive paste for three-dimensional molding, then the paste can be applied to resin substrates, but thermal stretching causes disconnection or detachment of wires in complex shapes like dome shapes
Solution Approach 1:
The invention changes the particle shape parameter from flaky to aggregated spherical form with controlled size (0.1-3 µm) and optimized packing characteristics (tap density 2-5 g/cm³). This enables the paste to maintain manufacturing ease while achieving wire integrity during thermal molding up to 135% deformation
Solution Approach 2:
The conductive paste is applied and cured on the flat substrate before thermal molding, establishing a stable conductive network in advance. This preliminary action ensures that the wire pattern is already formed and adhered before the three-dimensional shaping process begins
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 solution prevents disconnection during thermal stretching, ensuring excellent adhesion and conductivity, allowing for deformation rates up to 135% without failure, suitable for substrates like PET, PEN, polycarbonate, and polystyrene.
Implementation Method 1
the paste which does not cause any disconnection of the circuit pattern even in the thermal stretching during molding
Implementation Method 2
a circuit pattern is formed on a substrate made of synthetic resin and is processed into a three-dimensional shape by thermal molding such as vacuum molding or press molding
Data Source
AI summary
To provide an electrically conductive paste which can prevent disconnection of a conductive part upon thermal stretch during molding. An electrically conductive paste for molding processing is prepared by mixing and dispersing aggregated silver particles, a resin having glass transition temperature of 80°C or lower, a curing agent and a solvent. Preferably, tap density of the aggregated silver particles is 2 to 5 g/cm3 , specific surface area of the aggregated silver particles is 0.5 to 2 . 0 m2/g, the aggregated silver particles contain aggregated silver particles consisting of the primary particles having an average particle diameter of 0.1 to 3 µm measured by a scanning electron microscope, the glass transition temperature of the resin is 60°C or lower, and number-average molecular weight of the resin is 5000 to 40000. The electrically conductive paste is suitable for use applications wherein the whole body of a substrate is thermally deformed to form a three-dimensional circuit after the formation of a printed circuit, and is particularly suitable for the formation of a fine wire for a touch sensor.