Flexible Connection Member Impedance Control via Bonding Layer
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Solution Overview
Problem
Flexible circuit boards in electronic devices experience impedance variations and signal degradation due to bending, especially when used in high-frequency applications like 5G communication systems, as they lack inter-layer bonding, leading to reverse bending and increased loss in RF signal lines.
Innovation Solution
A flexible connection member is designed with conductive layers including ground regions on both sides and under the signal line, featuring a bonding sheet layer between the conductive layers to stabilize the structure and reduce impedance variations, and includes vias for electrical conduction between layers, thereby maintaining signal integrity and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-layered substrates are stacked without bonding to maintain flexibility, then the flexible circuit board can be bent, but reverse bending occurs causing impedance variations and signal loss
Solution Approach 1:
The circuit board is divided into rigid and flexible regions, with the rigid region providing structural support and the flexible region enabling bending. This segmentation allows the board to maintain flexibility while preventing reverse bending of the entire structure, thus maintaining signal integrity in the RF line.
Solution Approach 2:
A rigid region acts as an intermediary between the flexible circuit board and the external environment, providing structural support and preventing reverse bending. This intermediary structure allows the flexible region to bend without causing impedance variations in the RF signal line.
2Adaptability or versatility
If the flexible circuit board is bent, then adaptability is improved, but impedance variations increase causing signal degradation
Solution Approach 1:
Different regions of the circuit board are designed with different properties: the rigid region provides structural stability while the flexible region enables bending. The RF line is specifically positioned in the rigid region where impedance can be precisely controlled, while the logic lines are in the flexible region where bending occurs.
Solution Approach 2:
The circuit board uses a multi-layer structure with conductive layers positioned at different heights and locations. Ground regions are placed on both sides and under the RF line to maintain consistent impedance characteristics even when the board is bent, effectively managing electromagnetic fields in three-dimensional space.
3Reliability
If ground regions are added on both sides and under the signal line to reduce impedance variations, then signal integrity is improved, but device complexity increases
Solution Approach 1:
The rigid region serves multiple functions: it provides structural support, prevents reverse bending, and houses the RF line with its ground regions for impedance control. This multi-functional design improves signal integrity without proportionally increasing complexity, as one structural element accomplishes multiple objectives.
Data Source
AI summary
Various embodiments disclosed in the disclosure relate to a flexible connection member and an electronic device comprising same, the flexible connection member having an RF line for signal transmission formed therein, wherein an impedance of the RF line is prevented from being changed even when a flexible printed circuit board is bent. According to one embodiment, a connection member may be provided, the connection member comprising, a first conductive layer including a first logic line, and a second conductive layer in contact with the first conductive layer and including a bonding sheet layer, wherein the second conductive layer includes, a second logic line formed on part of the second conductive layer, and an RF line formed on other part of the second conductive layer, the bonding sheet layer includes, the second conductive layer adhered over the second logic line and the RF line, a first insulating layer formed between the first conductive layer and the second conductive layer, and pins formed on one side of the first conductive layer and the second conductive layer and configured to be electrically connected to connection pins of an external module, and the second conductive layer includes at least one via formed between the second logic line and the RF line so as to energize between the layers included in the second conductive layer. Such a flexible connection member may vary according to embodiments, and an electronic device comprising the flexible connection member may be provided according to various other embodiments.