Definite Guide: Tell You How To Do PCB Design

PCB was born in 1936, and the United States used the technology in military radios in 1943; since the mid-1950s, PCB technology has been widely used. At present, PCB has become the "mother of electronic products", and its applications have penetrated almost all terminal areas of the electronics industry, including computers, communications, consumer electronics, industrial control, medical instruments, defense industry, aerospace, and many other fields. As the first step in creating a PCB, PCB design is also crucial.

PCBs have evolved from single-layer PCB to double-sided PCB, multilayer PCB, and flexible PCB, and still maintain their respective development trends. Due to the continuous development of high precision, high density and high reliability, and continuous reduction in size, cost and performance, printed boards still maintain a strong vitality in the future development of electronic equipment.


How Is The PCB Designed

I summarize the PCB design process into 7 steps.


1. Preliminary Preparation

To make a good board, in addition to designing the principles, you must also draw well. Before designing the PCB, you must first prepare the component library of the schematic SCH and the component library of the PCB. The component library can use the library that comes with Peotel, but in general, it is difficult to find a suitable one. It is best to make the component library yourself according to the standard size data of the selected device. In principle, the component library of the PCB is made first, and then the component library of the SCH is made. The component library of the PCB has higher requirements, which directly affects the installation of the board; the component library requirements of the SCH are relatively loose, as long as you pay attention to defining the pin properties and PCB.


pcb components libraries

Set Up PCB Component Library

According to the types and packaging of components, the PCB component packaging library includes the following 11 libraries:

  1. Integrated circuit

  2. Integrated Circuit (SMD)

  3. Inductance

  4. Capacitor

  5. Resistance

  6. Diode rectifier

  7. Optoelectronic devices

  8. Connector

  9. Transistor

  10. Crystal Oscillator

  11. Other components

  12. Schematic Library

pcba components

Depending on the type of component, the schematic component library includes the following 16 libraries:

  1. Microcontroller

  2. Integrated circuit

  3. TTL74 series

  4. COMS series

  5. Diodes and rectifiers

  6. Transistors: including transistors, field-effect transistors, etc.

  7. Crystal

  8. Inductance and transformer parts

  9. Optoelectronic devices: including light-emitting diodes, digital tubes, etc.

  10. Connectors: including pin headers, strip connectors, waterproof plug sockets, etc.

  11. Electrolytic capacitor

  12. Tantalum capacitor

  13. Non-polar capacitor

  14. SMD resistor

  15. Other resistance: including carbon film resistance, cement resistance, photoresistor, varistor, etc.

  16. Other components: including buzzer, power module, relay, battery, etc.


2.PCB Structure Design

2 layer pcb,multilayer pcb,circuit board

According to the determined circuit board size and various mechanical positioning, draw the PCB board frame in the PCB design environment, and place the required connectors, buttons/switches, screw holes, mounting holes, etc. according to the positioning requirements.

Fully consider and determine the wiring area and non-wiring area (such as how much area around the screw hole belongs to the non-wiring area).


3.PCB Layout Design


pcb layout,circuit layout


The layout design is to place the devices in the PCB frame according to the design requirements. Generate the netlist (Design → Create Netlist) in the schematic tool, and then import the netlist (Design → Import Netlist) in the PCB software. After the netlist is successfully imported, it will exist in the software background. All devices can be called out through the Placement operation, and there are flying leads between the pins to connect. At this time, the device can be designed.

PCB layout design is the first important process in the entire PCB design process. The more complicated the PCB circuit board, the better the layout can directly affect the difficulty of the later wiring.

The layout design relies on the basic knowledge of circuit board designers and the rich experience in design, and it is a higher-level requirement for circuit board designers. The junior circuit board designer has little experience and is suitable for small module layout design or PCB layout design tasks with low difficulty on the whole board.


4.PCB Wiring Design

PCB wiring design is the process with the largest workload in the entire PCB design, which directly affects the performance of the PCB board.

In the PCB design process, there are generally three realms of wiring:

  • The first is the cloth pass, which is the most basic entry requirement for PCB design;

  • The second is the satisfaction of electrical performance. This is the standard for measuring whether a PCB board is qualified.

  • After wiring, carefully adjust the wiring to achieve the best electrical performance;

Once again, it is neat and beautiful, cluttered wiring, even if the electrical performance is too high, it will bring great inconvenience to the later board optimization and testing and maintenance. The wiring requirements are uniform and can not be crisscrossed without rules.


5. Wiring Optimization and Silkscreen Placement


"PCB design is not the best, only better", "PCB design is an art of defects", this is mainly because PCB design has to meet the design requirements of various aspects of hardware, and individual requirements may be conflicting. Bear palms do not have both.

For example, a PCB design project needs to be designed as a 6-layer board after the circuit board designer evaluates, but the product hardware must be designed as a 4-layer board due to cost considerations, then the signal shielding ground layer can only be sacrificed, resulting in adjacent wiring Signal crosstalk between layers increases and signal quality decreases.

The general design experience is that the time to optimize the wiring is twice that of the initial wiring. After the PCB wiring optimization is completed, post-processing is required. The first thing to deal with is the silkscreen logo on the PCB board surface. When designing, you need to mirror the bottom silkscreen characters to avoid confusion with the top silkscreen.


6. Network DRC Inspection and Structural Inspection


Quality control is an important part of the PCB design process. General quality control methods include design self-inspection, design mutual inspection, expert review meetings, and special inspections.

Schematic and structural element diagrams are the most basic design requirements. Network DRC inspection and structural inspection are to confirm that the PCB design meets the two input conditions of the schematic netlist and the structural element diagram.

Generally, circuit board designers will have their own accumulated design quality checklists, where entries are partly derived from the company or department's specifications and partly from their own experience. The special inspection includes Valor inspection and DFM inspection of the design. These two parts focus on the light drawing files of the PCB design output back-end processing.


7.PCB Board


Before the PCB formally procession, the board designer needs to communicate with the PE of the PCB supplier board manufacturer to answer the manufacturer's confirmation question about the PCB board processing.

These include, but are not limited to the choice of PCB board model, the adjustment of the line layer line width and line spacing, the adjustment of impedance control, the adjustment of the thickness of the PCB stack-up, the surface treatment process, the aperture tolerance control, and delivery standards, etc.


Conclusion

The above is the entire process of PCB design. If you think this article is helpful to you, or want to know the detailed process and tutorial about PCB design, welcome to leave a message.Your support is the biggest motivation for our creation~


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