What should be paid attention to in the PCB design and wiring process?
In the PCB design process, the wiring is divided into three types:
The first is the cloth, the second is the satisfaction of the electrical performance, followed by the beauty.
The cabling CAM OEM board is mainly based on the following principles:
1. In general, the power and ground wires should be routed first to ensure the electrical performance of the board. Within the scope of the conditions, try to widen the power supply and ground line width. It is better to ground the ground line than the power line. Their relationship is: ground line > power line > signal line. Usually the signal line width is 0.2~0.3mm. The finest width can reach 0.05~0.07mm, and the power cord is generally 1.2~2.5mm. For the PCB of the digital circuit, a wide ground wire can be used to form a loop, that is, a ground net is used for use (the ground of the analog circuit cannot be used in this way)
2. Wires that require more stringent requirements (such as high-frequency lines) are pre-wired. The edges of the input and output ends should be avoided to avoid adjacent reflections to avoid reflection interference. If necessary, ground wire should be isolated. The wiring of two adjacent layers should be perpendicular to each other, and parasitic coupling is easy to occur in parallel.
3. The oscillator case is grounded and the clock line is as short as possible and cannot be pinned everywhere. Below the clock oscillating circuit, the special high-speed logic circuit part should increase the area of the ground, and should not take other signal lines, so that the surrounding electric field approaches zero;
4. Use 45o of polyline wiring as much as possible, and 90o fold lines should not be used to reduce the radiation of high frequency signals; (higher lines require double arcs)
5. Do not form a loop on any signal line. If it is unavoidable, the loop should be as small as possible; the number of vias of the signal line should be as small as possible;
6. The key lines are as short and thick as possible, with protective ground on both sides. [PS: Packing]
7. When transmitting a sensitive signal and a noise field band signal through a flat cable, it is extracted by means of "ground-signal-ground".
8. Key signals should be reserved for test points to facilitate production and maintenance testing.
9. After the schematic wiring is completed, the wiring should be optimized. At the same time, after the initial network inspection and the DRC inspection are correct, the grounding of the unwired area is performed, and the large-area copper layer is used as the grounding line, and the printed board is not used. The places used are connected to the ground as ground. Or make a multi-layer board, power supply, ground line each occupy a layer.
The wiring should be neat and uniform, and there should be no rules and regulations to facilitate testing and maintenance.