Flexible Circuit Board Bending Durability via Segmented Ground Lines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional flexible circuit boards are prone to fractures and impedance deviations when bent, especially in wireless terminals, due to their design limitations and the need for impedance matching with other components, which restricts their installation locations and increases the risk of signal line and ground line damage.
Innovation Solution
A flexible circuit board design featuring a first substrate part with a sequential thickness variation, including a three-layer dielectric and four-layer ground structure, and a via hole for electrical connection, allowing for enhanced bending durability and reduced stress concentration, enabling installation without locational restrictions and preventing signal and ground line damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the flexible circuit board is placed close to other components to save space, then the inner space utilization is improved, but the characteristic impedance deviates from 50Ω causing signal transmission efficiency to deteriorate
Solution Approach 1:
The patent applies local quality by creating different structural configurations in different regions of the flexible circuit board. Specifically, the signal line and ground line are positioned at different distances from adjacent components depending on the location, with greater spacing provided near components that would cause impedance deviation. This allows the board to be placed close to components overall while maintaining proper impedance characteristics in critical areas.
2Adaptability or versatility
If the flexible circuit board is bent to accommodate folding terminal design, then the adaptability to terminal shape is improved, but the signal line and ground line are prone to fractures
Solution Approach 1:
The patent applies segmentation by dividing the flexible circuit board into multiple layers with signal lines and ground lines arranged in specific patterns. The ground lines are positioned to provide shielding and mechanical support to the signal lines during bending. This segmented structure distributes stress more evenly and prevents fracture of individual conductive traces.
Solution Approach 2:
The patent implements beforehand cushioning by positioning ground lines adjacent to signal lines in the flexible circuit board structure. These ground lines act as a protective cushion that shields signal lines from mechanical stress and electrical interference during bending operations, preventing fractures before they occur.
3Loss of energy
If the signal line is thickened to decrease line loss, then the signal transmission quality is improved, but the characteristic impedance control becomes more difficult
Solution Approach 1:
The patent introduces ground lines as intermediary elements between signal lines and adjacent components. These ground lines serve as a reference plane that stabilizes the characteristic impedance of signal lines. By controlling the spacing and configuration of ground lines, the patent achieves both low line loss (through optimized signal line dimensions) and precise impedance control (through ground line positioning), resolving the contradiction between these two requirements.
Data Source
AI summary
The present invention provides a flexible circuit board having enhanced bending durability. The flexible circuit board comprises: a first board part; a second board part which extends from one side of the first board part and is thinner than the first board part so as to be bendable; and a third board part which extends from one side of the second board part and is thinner than the second board part so as to be bendable.