Tips for high-speed (> 100MHz) high-density PCB design?
When the size of the circuit board is fixed, if you need to accommodate more functions in the design, it is often necessary to increase the trace density of the PCB. ,
When designing high-speed and high-density PCBs, crosstalk interference does need special attention, because it has a great impact on timing and signal integrity.
Here are a few things to note:
1. Control the continuity and matching of the characteristic impedance of the trace.
2. The size of the line spacing. It is commonly seen that the spacing is twice the line width. You can use simulation to understand the effect of trace pitch on timing and signal integrity, and find the minimum tolerable pitch. The results of different chip signals may be different.
3. Select the appropriate termination method.
4. Avoid that the directions of the two adjacent layers on the top and bottom are the same, and there are even traces that overlap on top and bottom, because this kind of crosstalk is larger than that of the adjacent layers on the same layer.
5. Use blind / buried via to increase the trace area. However, the manufacturing cost of the PCB will increase. It is really difficult to achieve complete parallelism and equal length in actual implementation, but it is still necessary to do it as far as possible.
In addition, differential termination and common mode termination can be reserved to mitigate the impact on timing and signal integrity