PCB design is a very complicated job, and there are many rules. However, there are some commonly used design rules. If you master it, you can do the job well. Let the engineer explain to you the following, commonly used PCB circuit board design rules:
1. 3W rule
The 3W rule is that the distance between lines must be kept 3 times the line width, which is the usual 3H; H refers to the width of lines. Theoretically, when the center-to-line distance is 3 times the line width, 70% of the electric field between the lines can be kept undisturbed, which is often called the 3W rule.
2. Rules for component layout
The layout of components is very important and directly affects the performance of the product. The sorting must be paid attention to. The specific points are as follows:
First, the schematic diagram is the foundation. The schematic diagram must repeatedly consider the optimal design, follow the rule of "first big and then small, first difficult and then easy". Important units and core electronic components must be limited in layout.
Second, it is necessary to reserve debugging positions for small components, and circuits with the same structure and similar structures should be distributed symmetrically and evenly as much as possible.
Third, attention should be paid to the direction. Electronic components of the same type should be designed and arranged in the X-axis or Y-direction. For special components, especially heating elements, they should be finely distributed and evenly arranged.
Fourth, the layout should be done. Keep the wires as short as possible. The key signal line is the shortest.
3. Wiring rules
Key signals such as high-speed signals, analo small signals, synchronization signals, and clock signals must be routed first. To start wiring from the most densely connected area on the board, it also follows the rule of "first big and then small, first difficult and then easy".
4. 20H rule
It refers to the distance that the power layer is retracted by 20H relative to the ground layer, that is, it is necessary to ensure that the edge of the power plane is at least 20 times the distance between the two planes than the edge of the 0V plane. This is to suppress the radiation effect at the edge.
