Flexible Conductive Printed Circuits with TPU Overcoat
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Solution Overview
Problem
Current digitally printable conductive inks are not flexible, have low scratch resistance, and poor adhesion to substrates, limiting their application in areas requiring robust circuitry, such as smart packaging that needs to withstand shipping and handling.
Innovation Solution
A method and apparatus for producing flexible conductive printed circuits with a printed overcoat using a mixture of thermoplastic polyurethane (TPU) and a solvent with a viscosity of 1 to 2,000 centipoise, allowing precise digital printing over conductive lines on flexible substrates, enhancing flexibility, adhesion, and scratch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If digitally printable conductive inks are used, then low cost and ease of printing are achieved, but flexibility, scratch resistance, and adhesion deteriorate
Solution Approach 1:
The patent applies composite materials by combining conductive ink with polymer overcoats (such as polyurethane, polyethylene, or polypropylene) to create a multi-layer structure. This composite approach maintains the ease of digital printing while significantly improving flexibility, scratch resistance, and adhesion properties, resolving the contradiction between manufacturing ease and reliability.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the conductive ink formulation and overcoat materials to optimize both printability and mechanical properties. By adjusting viscosity, composition ratios, and curing parameters, the system achieves high reliability (flexibility and scratch resistance) while maintaining ease of digital printing production.
2Reliability
If conventional conductive inks are used on rigid substrates, then good conductivity is achieved, but flexibility and adaptability to flexible substrates deteriorate
Solution Approach 1:
The patent uses flexible polymer overcoats (thin films) that conform to flexible substrates while encapsulating the conductive ink. These flexible shells maintain electrical conductivity through the conductive ink layers while providing the necessary flexibility and adaptability to curved or bent surfaces, resolving the contradiction between conductivity and flexibility.
Solution Approach 2:
The polymer overcoat acts as an intermediary layer between the rigid conductive ink and the flexible substrate. This intermediary maintains good conductivity by preserving the conductive ink's structural integrity while simultaneously providing flexibility and adaptability to the substrate, resolving the contradiction between conductivity and flexibility.
3Strength
If thick overcoats are applied to protect conductive lines, then scratch resistance improves, but printing precision and adhesion to specific locations deteriorate
Solution Approach 1:
The patent segments the protective overcoat into multiple thin layers applied sequentially rather than one thick layer. This segmentation allows each layer to be printed with high precision at specific locations while collectively providing sufficient thickness for scratch resistance. The multi-layer approach maintains printing precision while achieving the required protective strength.
Solution Approach 2:
The patent applies preliminary thin overcoat layers before finalizing the complete protective structure. These preliminary layers are printed with high precision at specific locations, and subsequent layers build upon them to achieve the required thickness for scratch resistance. This preliminary action ensures printing precision is maintained while still achieving adequate protection.
Data Source
AI summary
A method for producing flexible conductive printed circuit with a printed overcoat is disclosed. For example, the method includes forming conductive printed circuit lines on a flexible substrate, detecting locations on the flexible substrate where the conductive printed circuit lines are formed, and printing an overcoat over the conductive printed circuit lines at the locations that are detected on the flexible substrate, wherein the overcoat comprises a mixture of thermoplastic polyurethane (TPU) and a solvent having a viscosity of 1 centipoise to 2,000 centipoise to allow the mixture to be printed.