The design steps and circuit layout principles of the PCB circuit board

A complete PCB circuit board is composed of pads, perforated, installed holes, wires, components, plug -in plug -ins, filling, electrical boundaries, etc. Through the combination processing into a complete PCB, do you know the problems of a fast circuit board from design, wiring, assembly, processing, precautions, etc. Today, Leadsintec will take everyone to study.

Composition of PCB circuit board:

1. Line and graphics: The line is a tool for turning between the original. In the design, the large copper noodles will be designed as the ground and power layer. The lines and the diagram are made at the same time.
2. The dielectric layer: It is used to maintain the insulation between the line and the layers, commonly known as the substrate.
3. Pole: The guide hole can turn the lines above two levels of lines, and the larger guide holes are used as parts plug -in. use.
4. Anti -welded ink: Not all copper noodles must eat tin parts, so the areas of non -eating tin will printed a layer of substances to eat tin (usually epoxy resin) to avoid non -eating tin lines. Short -circuit. According to different processes, it is divided into green oil, red oil, and blue oil.
5. Silk printing: This is a non -necessary composition. The main function is to mark the names and position boxes of each part on the circuit board to facilitate the repair and identification after assembly.
6. Surface treatment: Because the copper surface is easily oxidized in the general environment, it can not be able to go to the tin (poor welding), so it will be protected on the copper surface of the tin. The protection methods include tin spray, gold, silver, tin, and organic welds. The methods have their own advantages and disadvantages, which are collectively referred to as surface treatment.

Design steps of PCB circuit board:

(1) Design of circuit schematic diagrams: The design of the circuit schematic diagram is mainly to use the Protel DXP schematic graph editor to draw the schematic diagram.
(2) Generating network reports: The network report is a report that displays the link between the circuit principle and the links of the components of the components. Find the connection between the components, so as to provide convenience for the latter PCB design.
Heatheating, electromagnetic compatibility, etc. To finally complete this step, it is often necessary to modify the circuit principle diagram countless times.
(4) PCBA control board production; after purchasing components, after the PCB board is obtained, according to the schematic diagram, through SMT upper parts, various components on welding, and DIP plug -in process, so that our control board is completed.

Component placement principle

First, components that are closely coordinated with the structure, such as power sockets, indicators, switches, connectors, interfaces, etc.; Second, place special components, such as large components, heavy components, heating components, ICs, ICs, ICs Finally, place small components; consider the line when the component layout, and try to choose the layout design that facilitates the wiring;
1. The crystal should be placed close to the IC;
2. The layout of IC decoupled capacitors should be as close to the power pipe foot of the IC as much as possible, and the shortest circuit formed between the power supply and the land;
3. The heating components should generally be evenly distributed in order to facilitate the heat dissipation of the single board and the whole machine. The temperature sensitive devices except the temperature detection element should stay away from the component with large heat capacity;

Wiring principle

1. High -speed signal wiring is as short as possible, and the key signal wiring is as short as possible;
2. Do not play too much perforated in a wiring, do not exceed two holes;
3. The corner of the wiring should be as greater than 90 degrees as possible to eliminate the corner of less than 90 degrees, and try to use the corner of 90 degrees as little as possible;
4. When the double -panel wiring, the wires on both sides should be vertically, obliquely, or bending the wiring to avoid parallel to each other to reduce parasitic coupling;
5. The audio input cable should be waited for a long, two lines are close, and the audio cable outsourcing ground wire;
6. The power amplifier IC cannot be moved under.
7. There is no ground layer in the double panel. The crystal capacitor ground wire should be connected to the closest GND pins on the crystal of the device as much as possible, and the pores should be reduced as much as possible;
8. Power line, USB charging input to take a thick line (“= 1mm), pave the copper on both sides of the holes, and then make a few more holes on the copper place;
Under normal circumstances, first of all, the power line and ground wire are performed to ensure the electrical performance of the circuit board. In the range of conditions permit, try to widen the power and ground width. It is best to wider the ground line than the power line. Their relationship is: ground line> power cord> signal line, usually the signal line width is 0.2 ～ 0.3mm The finest width can reach 0.05 to 0.07mm, and the power cord is generally 1.2 to 2.5mm.

Precautions for the production process of PCB circuit board

1. Set the outer shape of the circuit board to draw-out layer layer drawing line;
2. The distance between the line and the line, the distance between the line and the perforated, and the copper -cover spacing must meet the requirements of the version of the version. Generally, 10mil can be achieved;
3. Create the rules before casting the board, the key to check the short circuit and the opening of the road;
4. At least 2mm distance from the board when the component layout.