What are the design requirements for PCB layout and wiring?

With PCB Size requirements are getting smaller , Device density requirements are higher and higher ,PCB Design is becoming more and more difficult , about PCB Higher requirements for layout and cabling . that ,PCB What are the design requirements for board layout and wiring ？

1、 determine PCB The layer number
The size of the circuit board and the number of layers of wiring need to be determined in the early stage of design . The number and stacking mode of wiring layers will directly affect the wiring and impedance of the circuit board ; At the beginning of the design, it is better to use more circuit layers and make copper evenly distributed .

2、 Design rules and restrictions
All signal lines with special requirements shall be classified , Every signal class should have priority , The higher the priority , The more strict the rules are . The rules relate to the width of the printed wire 、 Number of vias 、 Parallelism 、 The interaction between signal lines and the limitation of layers , It has a great impact on the performance of wiring tools .

3、 Layout of components
If the assembly department allows the components to move , The circuit can be optimized properly , More convenient for automatic wiring . The auto wiring tool only considers one signal at a time , By setting the constraints of the wiring and setting the layers of the distributable signal lines , It can make the wiring tool complete the wiring as the designer imagined .

4、 Fan out design
In the fan out design stage , Each pin of surface mount device shall have at least one through hole , So that when more connections are needed , The circuit board can carry out inner layer connection 、 Online testing and circuit reprocessing . In order to make the automatic wiring tool efficient , Be sure to use as large a via size and printed wiring as possible , The interval is set to 50mil Ideal .

5、 Manual wiring and key signal processing
First, the key signals are wired , Manual wiring or combination of automatic wiring tools . When wiring is complete , Then the relevant engineering and technical personnel shall check the signal wiring , After passing the inspection , Fix these wires , And then start automatically wiring the rest of the signals .

6、 Automatic wiring
The general rules should be used in the automatic wiring of signals . The layer used for a given signal and the number of vias used are limited by setting restrictions and forbidden wiring areas , The wiring tool can automatically wire according to the design idea of the engineer . After setting the constraints and applying the created rules , Automatic wiring will achieve similar results as expected .

7、 Arrangement of wiring
Some signals with few constraints , The length of the wiring is very long , At this time, we can first determine which wiring is reasonable , Which wiring is unreasonable , Then, the short message wiring length and the number of vias can be reduced through manual editing .

That's it PCB Ten design requirements for board layout and wiring , Have you learned ？
More content can be seen in official account. ：PCBA Information sharing