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Seven steps to design a PCB

2020-03-28

Printed circuit board {PCB circuit board}, also known as printed circuit board, is a provider of electrical connections for electronic components. Its development has a history of more than 100 years; its design is mainly layout design; the main advantages of using circuit boards are to greatly reduce errors in wiring and assembly, and to improve automation and production labor rates.

Since printed circuit boards are not general end products, the definition of the names is a bit confusing. For example, the motherboard for personal computers is called the motherboard, and it cannot be called directly as a circuit board. They are not the same, so they cannot be said to be the same when evaluating industries. Another example: because there are integrated circuit parts loaded on the circuit board, the news media calls him an IC board, but in fact he is not equivalent to a printed circuit board. The printed circuit board we usually refer to is the bare board-that is, a circuit board without components on it.

PCB circuit boards have developed from single-sided to double-sided, multi-layered, flexible and flexible, 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 will still maintain a strong vitality in the future development of electronic equipment.

So how is the PCB circuit board designed? After reading the following seven steps, you will understand

1. Preliminary preparation

Including preparing components and schematics. Before designing a PCB, you must first prepare a schematic SCH component and a PCB component package library.

The PCB component package library is best established by engineers based on the standard size data of the selected device. In principle, the component packaging library of the PC is first established, and then the schematic SCH component library is established.

The PCB component package library has higher requirements, which directly affects the installation of the PCB; the schematic diagram of the SCH component library requirements is relatively loose, but pay attention to define the pin properties and the corresponding relationship with the PCB component package library.

2.PCB structure design

According to the determined size of the PCB circuit board and various mechanical positioning, draw the PCB board frame in the PCB design environment, and place the required connectors, buttons / switches, positioning 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 positioning hole belongs to the non-wiring area).

3.PCB layout design

The layout design is to place the devices in the PCB board 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 imported successfully, it will exist in the software background. Through Placement operation, all devices can be called out, 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 complex the PCB board, the better the layout can directly affect the implementation difficulty of the later wiring.

Layout design relies on the circuit foundation skills and design experience of PCB circuit board designers, and it is a higher level requirement for PCB 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 layout, which is the most basic entry requirement for PCB design;

The second is the satisfaction of electrical performance. This is a standard for measuring whether a PCB board is qualified. After wiring, carefully adjust the wiring so that it can 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 later board optimization and testing and maintenance.

5. Wiring optimization and silk screen placement

“PCB design is not the best, only better”, “PCB design is an art of defects”, this is mainly because PCB design needs to realize the design requirements of all aspects of hardware, and individual requirements may be conflicting. Bear palms do not have both.

6. Network DRC inspection and structural inspection

Quality control is an important part of the PCB design process. General quality control measures 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 structural element diagram, respectively.

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

7, PCB board

Before the PCB is formally processed, the PCB designer needs to communicate with the PE from the PCB supplier and answer the manufacturer’s confirmation question about the PCB processing.

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