Flexible Printed Circuit Design for USB 3.0 Signal Integrity
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Solution Overview
Problem
Conventional interconnection methods for integrated circuit (IC) devices in mobile devices face challenges with increased complexity due to high-frequency signaling, leading to electromagnetic interference (EMI) issues and significant insertion loss, which often require costly re-drivers to compensate for signal attenuation.
Innovation Solution
A flexible printed circuit (FPC) design that omits EMI shielding layers, using a multi-layer structure with a first signal layer for high-frequency signals and a second signal layer for lower-frequency signals, both separated by copper ground planes and non-conductive layers, to minimize insertion loss and allow unamplified signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If EMI shielding layers are added to protect high-frequency signals, then electromagnetic interference is reduced, but insertion loss increases significantly
Solution Approach 1:
The patent removes the EMI shielding layer from the flexible printed circuit board, extracting the harmful element that was causing excessive signal attenuation. By eliminating this layer entirely, the design accepts that EMI protection is not necessary for the intended application, thereby eliminating the associated insertion loss and avoiding the need for costly re-driver circuits.
Solution Approach 2:
The patent replaces the expensive EMI shielding solution with a simpler, cheaper alternative - no shielding at all. This approach trades off EMI protection for significantly reduced signal loss, making the overall system more cost-effective by eliminating both the shielding layer and the expensive re-driver amplifiers that would be needed to compensate for shielding-induced attenuation.
2Reliability
If conventional FPC design with EMI shielding is used, then signal protection is improved, but transmission distance is limited due to high insertion loss
Solution Approach 1:
By removing the EMI shielding layer that was limiting transmission distance, the patent enables signals to travel much farther without degradation. The extraction of this harmful element transforms the FPC from a short-range interconnect into a viable solution for longer-distance communications within mobile devices.
Solution Approach 2:
The patent changes the key parameter of the FPC structure by eliminating the EMI shielding layer, which fundamentally alters the signal transmission characteristics. This parameter change reduces insertion loss from excessive levels to acceptable levels, thereby extending the usable transmission distance of the interconnect.
3Reliability
If EMI shielding is implemented to handle high-frequency signals, then signal integrity is maintained, but system cost increases due to additional components
Solution Approach 1:
The patent extracts and removes the EMI shielding layer, simplifying the FPC structure to just the essential signal and ground layers. This extraction eliminates the need for additional expensive components like re-driver amplifiers, thereby reducing overall system cost while maintaining adequate signal integrity for the application.
Solution Approach 2:
The patent replaces the expensive EMI shielding approach with a cheap, simplified structure that uses only the necessary signal and ground layers. This approach trades off comprehensive EMI protection for significant cost savings, making the system more economically viable without requiring additional expensive components.
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 FPC design significantly reduces insertion loss, enabling the transmission of high-frequency signals without the need for re-drivers, thus improving interconnection efficiency and reducing costs in mobile devices.
Implementation Method 1
a first copper ground plane disposed in a plane above the first non-conductive layer, a second copper ground plane disposed in a plane below the second non-conductive layer... The flexible printed circuit is adapted to shield signals in the second signal layer from electromagnetic interference produced by higher frequency components of signals carried in the first signal layer
Data Source
AI summary
Systems, apparatus, methods for manufacturing and techniques for interconnecting integrated circuit devices are disclosed. A flexible printed circuit (FPC) provides EMI shielding with reduced insertion loss. The FPC includes a first signal layer fabricated from a planar conductive material and having traces configured to carry signals between a circuit boards. The FPC may include a first non-conductive layer disposed in a plane above the first signal layer, a second non-conductive layer disposed in a plane below the first signal layer, a first copper ground plane disposed in a plane above the first non-conductive layer, a second copper ground plane disposed in a plane below the second non-conductive layer, and a second signal layer provided in a plane above the first copper ground plane or below the second copper ground plane. Signals carried in the first signal layer may have a higher frequency than signals carried in the second signal layer.