Wiring is the most important process in the entire PCB design. This will directly affect the performance of the PCB board is good or bad. In the PCB design process, the wiring is generally divided into three realms: the first is the cloth, then the PCB design of the most basic requirements. If the line did not spread, and made it is flying line, it will be a substandard board, you can say no entry. Followed by electrical performance to meet.
This is a measure of whether a printed circuit board is qualified. This is after the cloth, carefully adjust the wiring, so that it can achieve the best electrical performance. Then it is beautiful. If your wiring cloth, and there is no impact on electrical performance of the place, but a look at the past chaotic, plus colorful, colorful, then how good your electrical performance, in the eyes of others or a piece of garbage. This brings great inconvenience to testing and maintenance. Wiring should be uniform, not criss-cross no rules. These are to ensure that the electrical performance and meet other individual requirements to achieve the case, otherwise it is the capital.
Five lines when the main principles
Under normal circumstances, the first power cord and ground should be wired to ensure the electrical performance of the circuit board. In the range of conditions allowed, as far as possible to widen the power, ground width, preferably ground than the power line width, their relationship is: ground> power line> signal line, usually signal line width: 0.2 ~ 0.3mm , The smallest width of up to 0.05 ~ 0.07mm, the power cord is generally 1.2 ~ 2.5mm. The PCB of the digital circuit can use a wide wire to form a loop, that is, to form a ground network to use (analog circuit of the ground can not be used)
Pre-wiring requires more stringent lines (such as high-frequency lines), the input and output side of the line should avoid parallel parallel, in order to avoid reflection interference. If necessary, should be added to ground isolation, two adjacent layers of wiring to each other perpendicular to the parallel prone to parasitic coupling.
Oscillator shell ground, the clock line to be as short as possible, and can not lead everywhere. Clock oscillation circuit, the special high-speed logic circuit part to increase the area, and should not take other signal lines, so that the surrounding electric field approaches zero;
As far as possible with 45o polyline wiring, can not use 90o fold line to reduce the high-frequency signal radiation; (requires a high line but also with a double arc)
Any signal lines do not form a loop, such as unavoidable, the loop should be as small as possible; signal line through the hole to minimize;
The key lines are as short and thick as possible and are protected on both sides.
Through the flat cable transmission of sensitive signals and noise field signal, use the "ground - signal - ground" way to lead.
The key signal should be set aside to facilitate the production and maintenance of test points. Schematic wiring is completed, the wiring should be optimized;
At the same time, after the initial network check and DRC check is correct, the non-wiring area to fill the ground, with a large area of copper for the ground, the printed circuit board has not been used on the ground are connected with the ground Line with. Or made of multi-layer board, power, ground each occupied a layer.