Designing and manufacturing high-speed circuit boards is not an easy task, but as long as the correct technology and practices are adopted, high-speed PCB design can be achieved. Some recommended practices are-
Correct material selection: For high-speed printed circuit boards below 2 GHz, FR-4 material is sufficient. If the wiring is short, the PCB does not require special materials. However, when it exceeds 2 GHz, it is recommended to use specialized high-speed materials. In theory, you can use the optimal PCB dielectric material with the lowest dielectric constant and dissipation factor, but cost is the limiting factor here. High speed PCB materials are often more expensive, and the better the quality, the higher the cost. The dielectric material only needs to be sufficient to handle the highest frequency signal on the PCB.
Correct selection of layer stack: The layer stack on high-speed printed circuit boards greatly affects the routing impedance and signal integrity. It is usually recommended to place all high-speed signals on the top or bottom layer, and to place a grounding plane below them, and the power plane should be isolated from high-speed signals as much as possible. Therefore, the ideal layer stack for a 6-layer PCB would be:
In this stack, each signal layer has a ground reference plane, and both high-speed signal layers are isolated using dielectric cells. Of course, you can use layer stacking based on your understanding of high-speed PCB requirements.
Control impedance: High speed signal routing requires impedance control routing. The impedance of the wiring must be calculated and carefully checked, as the impedance of the wiring is a sensitive parameter that maintains the integrity of the wiring signal. Failure to maintain appropriate impedance control may result in signal reflection, incompatibility with transceivers, and high signal attenuation.
Design rule checking and signal integrity tools: It is recommended to use many signal integrity and design rule checking tools on the designed PCB. Debugging hardware problems after PCB manufacturing is expensive and difficult. Therefore, it is recommended to conduct simulation testing on design files in software tools such as AnSys and HyperLynx, which can issue early warnings of errors and compromises in key factors such as signal integrity, dimensional tolerances, thermal management, and insulation before starting design and manufacturing.
High speed printed circuit board design is a tedious task, and both designers and manufacturers must be flawless in order to deliver high-speed PCB boards. Therefore, choosing a PCB supplier is crucial for PCB manufacturing and wise assembly.
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