Printed Circuit Board Wiring Principles
Generally, PCB design flow is as follows: preliminary preparation, PCB structure design, PCB layout, PCB wiring, wiring optimization and silkscreen, network and DRC inspection and structure check, PCB fabrication.
The carrier of the PCB wiring is the PCB board. Generally, the distance from reference ground to PCB board edge or signal line is about 1mm. This can constrain the signals to the PCB board and reduce EMC emissions.
PCB wiring should be uniform and tidy. EPCB summarizes some useful principles for better PCB wiring.
1.The key lines should be as short and thick as possible.
2.Test points should be reserved for critical points so as to facilitate production and maintenance testing.
3.Do not form a loop on any signal line. If it is unavoidable, the loop should be as small as possible; the vias number of the signal line should be as little as possible.
4.When the sensitive signal and noise field signal are transmitted through the flat cable, they should be led out using the "ground-signal-ground" method.
5.Pre-arrange the line (such as high-frequency lines) which has relatively strict requirements; the input and output side edges should avoid adjacent parallel, so as to avoid reflection interference. If necessary, ground isolation should be added. The wirings of two adjacent layers should be perpendicular to each other, because parallelism is likely to cause parasitic coupling.
6.The oscillator case is grounded, and the clock line should be as short as possible.
7.Use a 45° polyline as much as possible. Do not use a 90° polyline so as to reduce high-frequency signal emissions.
8.After the schematic wiring is completed, the cabling should be optimized. At the same time, if both the initial network inspection and DRC inspection are correct, you should add grounding in the unwired area.
9.Under normal circumstances, the power line and ground should be wired to ensure the electrical performance of the circuit board. If conditions allowed, try to widen the width of the power and ground lines. It is better that the ground line is wider than the power line. Their relationship is: ground width> power line width> signal line width. Generally, the signal line width is 0.2-0.3mm, the thinnest width is 0.05-0.07mm, and the power line is generally 1.2-2.5mm.