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This article mainly explains "what is the seven-step method of PCB layout and wiring". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn "what is the seven-step method of PCB layout and wiring"?

Seven-step method of PCB layout and wiring

Guide reading

At present, with the smaller and smaller size requirements of PCB and higher device density requirements, the difficulty of PCB design is gradually increasing. How to shorten the design time while ensuring the quality? This requires engineers to have excellent technical knowledge and some design skills.

1. Determine the number of layers of PCB

The size of the circuit board and the number of wiring layers need to be determined at the beginning of the design. The number of wiring layers and the STack-up method directly affect the wiring and impedance of the printed line. The size of the board helps to determine the cascading mode and the width of the printed line to achieve the desired design effect. At present, the cost difference between multilayer plates is very small, so it is better to use more circuit layers and distribute copper evenly at the beginning of the design.

II. Design rules and restrictions

To successfully complete the cabling task, the cabling tool needs to work under the correct rules and constraints. To classify all signal lines with special requirements, each signal class should have a priority, and the higher the priority, the stricter the rules.

The rules relate to the width of printed lines, the maximum number of via, parallelism, the interaction between signal lines and the limitation of layers. these rules have a great impact on the performance of routing tools. Careful consideration of design requirements is an important step in successful cabling.

Third, the layout of components

In the process of optimal assembly, manufacturability design (DFM) rules restrict the layout of components. If the assembly department allows the components to move, the circuit can be properly optimized to facilitate automatic routing.

For example, for the layout of the power cord:

In the PCB layout of ①, the power decoupling circuit should be designed near each related circuit, and should not be placed in the power supply part, otherwise it will not only affect the bypass effect, but also flow pulsating current on the power line and ground wire, causing disturbance.

For the direction of the power supply within the circuit, ② should supply power from the last stage to the front stage, and arrange the power filter capacitance of this part near the last stage.

③ for some major current channels, such as disconnecting or measuring current during debugging and testing, the current gap should be arranged on the printed wire during layout.

In addition, we should pay attention to the layout of the stabilized power supply, as far as possible arranged on a separate PCB. When the power supply and the circuit share the printed board, in the layout, the mixed layout of the voltage-stabilized power supply and the circuit components or the use of the ground wire between the power supply and the circuit should be avoided. Because this kind of wiring is not only easy to cause interference, but also can not disconnect the load during maintenance, so it can only cut part of the printed wire, thus damaging the printed board.

4. Fan out design

In the fan-out design phase, each pin of the surface mount device should have at least one through hole so that the circuit board can perform inner connection, on-line testing and circuit reprocessing when more connections are needed.

Manual wiring and processing of key signals

Manual cabling is an important process of printed circuit board design now and in the future. the use of manual cabling helps automatic routing tools to complete the routing work. By manually routing and fixing the selected network (net), the path that can be used for automatic routing can be formed.

First of all, the key signals can be routed manually or combined with automatic routing tools. After the wiring is completed, the relevant engineers and technicians will check the wiring of these signals, pass the inspection, fix these lines, and then begin to route the rest of the signals automatically. Due to the existence of impedance in the ground wire, it will bring common impedance interference to the circuit.

VI. Automatic wiring

For the routing of key signals, it is necessary to control some electrical parameters during routing, such as reducing the distributed inductance. After understanding the input parameters of the automatic routing tool and the influence of the input parameters on the routing, the quality of automatic routing can be guaranteed to a certain extent. General rules should be used for automatic routing of signals.

By setting restrictions and no routing areas to limit the layers used by a given signal and the number of via holes used, the routing tool can automatically route according to the design ideas of the engineer. After setting the constraints and applying the created rules, automatic routing will achieve similar results as expected, and after part of the design is completed, it will be fixed to prevent it from being affected by the later routing process.

The number of wiring depends on the complexity of the circuit and the number of general rules defined. Today's automatic routing tools are very powerful and usually complete 100% routing. However, when the automatic routing tool does not complete all the signal routing, it is necessary to manually route the remaining signals.

VII. Arrangement of wiring

For some signals with few constraints, the wiring length is very long, at this time, we can first judge which wiring is reasonable and which is unreasonable, and then shorten the signal wiring length and reduce the number of through holes by manual editing.

At this point, I believe you have a deeper understanding of "what is the seven-step method of PCB layout and wiring". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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