Multi-layer Flexible Circuit Board Using PTFE Substrate
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Solution Overview
Problem
Conventional multi-layer flexible circuit boards face challenges in adapting to high-frequency and high-speed trends due to high dielectric constant, loss factor, moisture absorption, and poor reliability, leading to signal transmission loss and copper ion migration issues, which are not adequately addressed by existing manufacturing processes.
Innovation Solution
A method for manufacturing a multi-layer flexible circuit board involving the use of novel material layers with semi-cured high-frequency materials and copper ion migration resistant adhesives, integrated through a thermoforming process, which simplifies the manufacturing process, reduces thickness, and enhances high-frequency signal transmission while preventing copper ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PI substrate is used for soft board manufacturing, then the soft board can be produced with conventional processes, but the high-frequency transmission loss is serious due to larger dielectric constant and loss factor
Solution Approach 1:
The patent changes the material parameters by replacing PI substrate with PTFE substrate, which has different dielectric constant and loss factor parameters optimized for high-frequency applications. This material substitution directly addresses the high-frequency transmission loss problem while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs composite material structure by combining PTFE substrate with specific copper foil layers and protective coatings. This composite approach creates a multi-layer structure that optimizes both signal transmission characteristics and mechanical properties for high-frequency applications
2Reliability
If PI substrate is used, then conventional manufacturing processes can be applied, but moisture absorption is high leading to poor reliability
Solution Approach 1:
The patent changes the substrate material from PI to PTFE, which has fundamentally different moisture absorption parameters. PTFE exhibits extremely low moisture absorption characteristics, directly improving structural reliability in humid environments while maintaining compatibility with conventional manufacturing processes
3Ease of manufacture
If conventional multi-layer structure is used, then the circuit board can be manufactured with standard processes, but the overall thickness is large and manufacturing complexity is high
Solution Approach 1:
The patent extracts and eliminates unnecessary intermediate layers from the conventional multi-layer structure. By using PTFE substrate with integrated copper circuits and simplified protective layers, the design removes redundant insulation layers and adhesive layers, thereby reducing overall thickness while simplifying the manufacturing process
Solution Approach 2:
The PTFE substrate serves multiple functions simultaneously: it provides mechanical support, electrical insulation, and high-frequency signal transmission properties. This multi-functionality eliminates the need for separate specialized layers, reducing both thickness and manufacturing complexity
4Reliability
If copper foil is used as conductor circuit material, then electrical conductivity is achieved, but copper ion migration occurs between lines causing circuit failure
Solution Approach 1:
The patent introduces an intermediary barrier layer between copper foil conductors. This intermediate layer prevents direct interaction between copper ions and the substrate, blocking ion migration pathways while maintaining electrical conductivity of the copper circuits and structural integrity of the board
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 method improves manufacturing efficiency, reduces power consumption, and ensures safe operation by enabling high-speed, low-loss signal transmission and preventing copper ion migration, thus adapting to the demands of 5G technology products.
Implementation Method 1
thermoforming: hot-pressing at least one group of novel material layer structures on the circuits of the upper surface and/or the lower surface of the double-sided FPC flexible board; in the hot-pressing process, firstly, gradually increasing the hot-pressing temperature from 50℃-100℃ to 380℃-400℃
Implementation Method 2
applying a copper layer on upper and lower surfaces of a base film respectively, and forming a circuit on the copper layer
Data Source
AI summary
The present invention discloses a method for manufacturing a multi-layer flexible circuit board, comprising the steps of: (1) manufacturing a double-sided FPC flexible board; (2) manufacturing a novel material layer structure; (3) hot pressing at least one group of upeer novel material layer structures on the circuits on the upper and/or lower surfaces of the double-sided FPC flexible board; forming a protective layer on the circuits of an outermost novel material layer structure and/or on exposed circuits of the double-sided FPC flexible board so as to obtain a multi-layer flexible circuit board. The present invention also discloses a multi-layer flexible circuit board manufactured by performing the above-mentioned method. The manufacturing process of the present invention is simplified, convenient and efficient; the multi-layer flexible circuit board not only greatly simplifies the novel material layer structure and reduces the overall thickness, but also has the function of high-speed transmission of high-frequency signals, especially suitable for new 5G technology products. It can protect and resist the migration of copper ions when it is energized between circuits so as to ensure the safety and normal operation of circuits.