Flexible Cable Air Gap EMI Shielding Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible printed circuit boards (FPCBs) used in electronic devices face signal loss due to electromagnetic interference (EMI) between high-speed and low-speed signals, particularly when using microstrip structures, which are not suitable for high-speed signals like 5G, and require improved EMI shielding efficiency.
Innovation Solution
A flexible cable design featuring a shielding layer formed under at least one signal transmission line, including an air gap and ground shielding layers, to minimize signal loss and shield electromagnetic interference with other electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a microstrip structure is used with the signal transmission line at the outermost portion, then the FPCB becomes thinner and more versatile, but electromagnetic waves are directly emitted to nearby electronic components causing noise problems and signal loss
Solution Approach 1:
The patent divides the FPCB structure into multiple layers with distinct functions: signal transmission layers, ground layers, and insulation layers. By segmenting the structure into these functional zones, the patent achieves both thinness and EMI shielding capability, resolving the contradiction between versatility and electromagnetic interference protection.
Solution Approach 2:
The patent implements a nested layer structure where ground parts and insulation parts are positioned between signal transmission lines and the outer environment. This nesting approach allows the FPCB to maintain a compact, thin profile while incorporating EMI shielding functionality within the same structure, thus resolving the contradiction between thinness and noise protection.
2Adaptability or versatility
If high speed signals are transmitted simultaneously with low speed signals, then the FPCB supports more versatile communication, but signal loss increases due to electromagnetic interference between signals
Solution Approach 1:
The patent applies different material properties and structural characteristics to different regions of the FPCB. Insulation parts with specific dielectric properties are positioned between high-speed and low-speed signal lines to reduce electromagnetic coupling. This local differentiation allows simultaneous support for multiple signal speeds while minimizing interference-induced signal loss.
Solution Approach 2:
The patent introduces insulation parts and ground parts as intermediary elements between high-speed and low-speed signal transmission lines. These intermediaries act as electromagnetic barriers that prevent direct coupling between signals of different speeds, enabling versatile multi-speed communication while reducing signal loss from interference.
3Reliability
If EMI shielding is enhanced to protect high speed signals, then signal loss is reduced, but the device complexity increases
Solution Approach 1:
The patent designs ground parts and insulation parts to serve multiple functions simultaneously: they provide EMI shielding, maintain mechanical structure integrity, enable flexible bending, and support both high-speed and low-speed signals. This multi-functionality reduces the need for additional dedicated shielding components, thereby limiting the increase in device complexity while improving signal transmission reliability.
Solution Approach 2:
The patent merges the EMI shielding function with the structural layers of the FPCB. Ground layers and insulation layers are integrated into the same manufacturing process and structural framework, rather than being added as separate shielding components. This merging approach enhances signal reliability through EMI protection while avoiding significant increases in device complexity.
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 flexible cable effectively reduces signal loss and enhances EMI shielding, improving the shielding ratio by 7-8 dB across various frequencies, making it suitable for high-speed signals while protecting adjacent components from electromagnetic noise.
Implementation Method 1
the air gap may be configured to act as a shield thereby preventing signals emitted from the at least one signal transmission line from propagating in the direction of the air gap
Data Source
AI summary
A flexible cable is provided. The flexible cable includes a first insulation part, a second insulation part disposed on the first insulation part, a first group of ground parts disposed at regular intervals under the first insulation part, at least one transmission line disposed at regular intervals under the first insulation part and alternately arranged with the first group of ground parts, an air gap formed under the first insulation part, a prepreg layer disposed under the first insulation part, and a third insulation part disposed under the air gap and the prepreg layer. The air gap is configured to prevent signals emitted from the at least one transmission line from propagating in a direction of the air gap. Hence, it is possible to shield electromagnetic interference with other electronic components while minimizing the signal loss.