The wiring technology of double layer pcb board
The use of automatic router to design pcb is attractive. In most cases, automatic routing of pure digital circuits (especially low-frequency signals and low-density circuits) will not be a problem. However, double layer pcb when attempting to use the automatic routing tool provided by the cabling software to do the wiring of analog, mixed-signal or high-speed circuits, there may be some problems and may cause extremely serious circuit performance problems. There are many things to consider about wiring, but the more troublesome problem is grounding. double layer pcb If the ground path is started by the upper layer, the grounding of each device is connected to the ground via the cable on the layer. For each device in the lower layer, a ground circuit is formed by connecting the upper hole on the right side of the circuit board to the upper layer. The immediate red flag that the user sees when checking the routing mode indicates that there are multiple ground loops.
In addition, the lower ground circuit is at a level. Can reduce the digital switching δi / δt on the impact of analog circuits. It should be noted, however, double layer pcb that the two sheets have a ground plane in the lower layer of the circuit board. double layer pcb This is designed so that engineers can quickly see wiring when doing troubleshooting, often in the device manufacturer's demonstration and evaluation board. But it is more typical to lay the ground plane on the upper side of the board to reduce the electromagnetic interference (emi).