Flexible PCB RF Cable Ground Mesh for Bend Crack Reduction
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Solution Overview
Problem
Conventional flexible PCB RF cables suffer from cracks during bending and increased insertion loss due to the formation of rhombic-shaped holes in the ground pattern.
Innovation Solution
The flexible PCB RF cable features a ground pattern composed of a mesh structure with circular holes and is divided into two ground patterns connected through a connection pattern overlapping with the signal line pattern, minimizing crack occurrence and insertion loss during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ground pattern with rhombic-shaped holes is used, then the cable structure is simple, but cracks occur during bending and insertion loss increases
Solution Approach 1:
The ground pattern is divided into multiple separate ground patterns (first ground pattern and second ground pattern) that are spaced apart from each other. This segmentation prevents stress concentration in a single continuous structure, thereby reducing crack formation during bending while maintaining effective ground coverage
Solution Approach 2:
The ground patterns are arranged in multiple layers (first and second dielectric sheets) with vertical spacing, creating a three-dimensional ground structure. This multi-layer arrangement provides mechanical flexibility to accommodate bending stresses while maintaining electromagnetic shielding effectiveness
2Reliability
If the ground pattern is formed as a continuous mesh, then shielding effectiveness is high, but cracks occur during bending tests
Solution Approach 1:
The continuous ground mesh is segmented into discrete ground patterns with spacing between them. This segmentation allows the structure to flex during bending without creating stress concentrations that lead to cracks, while the multiple layers maintain shielding effectiveness
Solution Approach 2:
The ground patterns are formed on flexible dielectric sheets that can bend without cracking the conductive patterns. The thin film structure accommodates bending stresses while maintaining electrical continuity and shielding performance
3Reliability
If ground patterns are spaced apart to prevent cracks, then bending performance improves, but ground coverage area decreases
Solution Approach 1:
The ground structure extends into the third dimension with multiple layers spaced vertically apart. This multi-layer configuration provides adequate ground coverage area and shielding effectiveness while the vertical spacing allows each layer to flex independently during bending
Solution Approach 2:
Multiple ground patterns across different layers work together to provide combined shielding effectiveness. The cumulative effect of multiple spaced-apart ground patterns compensates for the reduced area of individual patterns, maintaining overall ground coverage
Data Source
AI summary
Disclosed is a flexible PCB RF cable having a ground pattern that is divided into two ground patterns, which are connected through a connection pattern arranged in an area overlapped with a signal line pattern, and thus cracks are minimized during bending. The disclosed flexible PCB RF cable comprises: a signal line pattern interposed between a first dielectric sheet and a second dielectric sheet; first and second lower ground patterns, which are mesh patterns arranged to be spaced from each other below the first dielectric sheet; a lower connection pattern connected to the first and second lower ground patterns; first and second upper ground patterns, which are mesh patterns arranged to be spaced from each other above the second dielectric sheet; and an upper connection pattern connected to the first and second ground patterns.