Impedance matching check rules: The wiring width of the same network should be consistent. The change of the line width will cause uneven line characteristic impedance. When the transmission speed is high, reflection will occur. This situation should be avoided as much as possible in the design. Under certain conditions, such as the lead-out line of the connector, when the lead-out line of the BGA package has a similar structure, the change of the line width may not be avoided, and the effective length of the inconsistent part in the middle should be minimized.