Rigid-Flex PCB Ground Layout for Stable RF Impedance
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Solution Overview
Problem
Multi-layered rigid-flex PCBs experience impedance variations and signal loss due to reverse bending in the flexible PCB region, which is not adequately addressed by existing technologies.
Innovation Solution
A rigid-flex circuit board design with signal lines and ground regions on both sides and under the signal lines on conductive layers, reducing impedance variations by maintaining electrical connectivity and stability during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple layers are stacked over one another without being bonded together in the flexible PCB region, then the circuit board achieves integration and flexibility, but the layers may reversely bend when the flexible PCB region is bent or deformed, increasing loss due to impedance variations
Solution Approach 1:
The patent applies preliminary bonding between the flexible PCB and rigid PCB before the flexible region undergoes bending deformation. By pre-establishing adhesive bonds between layers and between flexible and rigid sections, the structure prevents reverse bending of layers during operation, thereby maintaining impedance stability and reducing signal loss while preserving flexibility.
2Volume of moving object
If the flexible circuit board region is bent or deformed, then the device achieves compact integration, but impedance variations increase causing signal loss
Solution Approach 1:
The patent implements local bonding in critical regions where the flexible PCB connects to rigid PCBs and where signal lines traverse the flexible region. By applying adhesive material selectively at these locations rather than uniformly across the entire flexible region, the design maintains impedance control and prevents layer separation at critical interfaces while preserving overall flexibility and compactness.
Solution Approach 2:
The patent creates a composite structure combining flexible PCB material with rigid PCB sections, bonded together through adhesive layers. This composite construction allows the flexible region to bend for compact integration while the rigid sections and bonding interfaces maintain structural stability and impedance control, reducing signal loss during deformation.
3Device complexity
If layers are not bonded together in the flexible protection cover region, then the structure remains flexible and integratable, but reverse bending occurs increasing loss
Solution Approach 1:
The patent applies adhesive material in advance to bond layers together in the flexible protection cover region before the device undergoes bending operations. This preliminary bonding prevents reverse bending of layers during use, thereby reducing impedance variations and signal loss while maintaining the integrated structure.
Data Source
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AI summary
An electronic device includes first printed circuit board (PCB) structure including a first layer (513) including a first conductive strip (513c), a second conductive strip (513a) electrically separated from the first conductive strip (513c) and extending at least partially in parallel with the first conductive strip (513c), and a third conductive strip (513b) electrically separated from the first conductive strip (513c) and extending at least partially in parallel with the first conductive strip (513c), such that the first conductive strip (513c) is between the second conductive strip (513a) and the third conductive strip (513b), and a second layer including a first conductive layer (515), a first insulating layer (572) interposed between and in contact with a first region (510) of the first layer (513) and a first region (510) of the second layer (515) facing the first region (510) of the first layer (513), a second insulating layer (575a) interposed between a second region (530) of the first layer (513) abutting the first region (510) of the first layer (513) and a second region (530) of the second layer (515) abutting the first region (510) of the second layer (515) while contacting the first layer (513), and a third insulating layer (575b) interposed between the second insulating layer (575a) and the second region (530) of the second layer (515), while contacting the second layer (515), and being separated from the second insulating layer (575a) by an air gap (575c), and a wireless communication circuit electrically connected to the first conductive strip (513c) and configured to transmit and/or receive radio frequency (RF) signal.