Optical Transceiver FPC Layout for High-Speed DSP Module Links
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Solution Overview
Problem
Existing optical transceivers face challenges in achieving ultra-high speed operation due to high frequency loss and heat dissipation issues, particularly in co-package structures where the digital signal processor (DSP) and optical modules are closely mounted, leading to thermal runaway risks and propagation losses.
Innovation Solution
The optical transceiver design includes a flexible wiring board (FPC) connecting the DSP and optical modules with specific PAD configurations on both surfaces, aligning heat dissipation directions, and minimizing high-frequency signal paths through Vias and BGAs, ensuring a common heat dissipation mechanism and reduced impedance mismatching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a co-package structure is used to reduce propagation loss, then high-speed operation is improved, but heat dissipation problems and thermal runaway risks worsen
Solution Approach 1:
The patent divides the optical transceiver into separate packages: the optical module (containing optical modulator/receiver chips) and the DSP module (containing digital signal processor) are packaged separately and mounted on different locations of the PCB. This segmentation isolates the heat-generating DSP from the optical modules, solving the thermal runaway risk while maintaining high-speed operation through optimized signal paths.
Solution Approach 2:
The patent introduces a flexible wiring board (FWB) as an intermediary component to connect the optical module and DSP module. The FWB serves as a thermal and electrical buffer, allowing high-speed signal transmission while preventing direct thermal coupling between the DSP and optical modules, thus resolving the contradiction between speed and heat dissipation.
2Ease of manufacture
If surface mount technology is used for mounting optical modules, then ease of manufacture is improved, but high-frequency signal loss worsens
Solution Approach 1:
The flexible wiring board acts as an intermediary transmission medium that provides low-loss high-frequency signal paths between the optical module and DSP. The FWB's flexible nature allows for optimized signal routing with minimal vias and impedance discontinuities, reducing high-frequency loss while maintaining ease of assembly through flexible routing capabilities.
Solution Approach 2:
The patent transitions from planar PCB mounting to three-dimensional spatial arrangement using the flexible wiring board. The FWB can be routed in multiple dimensions and folded to achieve optimal signal paths, reducing the number of vias and connections required compared to traditional surface mount technology, thereby reducing high-frequency signal loss.
3Ease of operation
If via structures are used in surface mount packages, then connectivity is improved, but high-frequency characteristics deteriorate
Solution Approach 1:
The flexible wiring board serves as an intermediary that reduces the number of via structures required for signal transmission. By providing dedicated signal paths on the FWB itself, the patent minimizes the need for vias in the signal path, thereby maintaining connectivity while preserving high-frequency characteristics.
Solution Approach 2:
Instead of using vias to achieve connectivity through the PCB, the patent inverts the approach by using the flexible wiring board's inherent conductive layers and traces to provide connectivity. This reversal eliminates or reduces the need for via structures in the critical signal path, maintaining connectivity while improving high-frequency performance.
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
This configuration reduces high-frequency signal degradation and enables broadband, high-speed operation by minimizing heat dissipation challenges and high-frequency losses, facilitating efficient thermal management and improved connectivity.
Implementation Method 1
the FPC includes a first connection PAD of a first surface solder-connected to a PAD of a terrace surface of the optical module and a second connection PAD of a second surface solder-connected to a PAD of an upper surface of the DSP circuit board
Implementation Method 2
a first connection PAD of a first surface solder-connected to a PAD of a terrace surface of the optical module and a second connection PAD of a second surface solder-connected to a PAD of an upper surface of the DSP circuit board
Data Source
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AI summary
An optical transceiver is disclosed that implements smooth high frequency connection between a DSP and an optical module. The optical module may include an optical receiver module and an optical modulator module. The optical transceiver may include a single optical module in which functions of both the optical receiver and the optical modulator are integrated. The high frequency connection is implemented by a flexible circuit board (FPC), and the FPC electrically connects between a PAD on the upper surface of a DSP circuit board and a PAD of a package of the optical module. A connection PAD on one surface of the FPC is connected to the DSP circuit board side, and a connection PAD on the other surface is connected to the optical module side. A DSP chip may be mounted on the DSP circuit board, and the entire DSP may be covered with a lid except for a region of the DSP circuit board connected to the FPC.