To design a cow fork PCB, you only need to do these seven points
Summary of content: PCB was born in 1936, and the United States used this 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 into almost all terminal areas of the electronics industry, including computers, communications, consumer electronics, industrial control, medical instruments, defense industry, aerospace and many other fields.
PCB has developed from single layer to double-sided, multi-layer and flexible, and still maintains its own development trend. 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.
So how is the PCB designed? After reading the following seven steps, you will understand:
1, preliminary preparation
Includes preparation of component libraries and schematics. Before designing a PCB, you must first prepare a schematic SCH component library 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 high requirements, which directly affects the installation of the PCB; the schematic diagram of the SCH component library requires relatively loose, but pay attention to define the pin properties and the corresponding relationship with the PCB component package library.
2, PCB structure design
Draw the PCB frame in the PCB design environment according to the determined circuit board size and various mechanical positioning, 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
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 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 board, the better the layout can directly affect the difficulty of the later wiring.
Layout design relies on the circuit foundation skills and design experience of circuit board designers, 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 cloth, which is the most basic entry requirement for PCB design;
Second is the satisfaction of electrical performance, which is a standard to measure 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, will bring great inconvenience to the later board optimization and testing and maintenance. The wiring requirements are neat and uniform.
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 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.
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 silk screen logo on the PCB board surface. When designing, the bottom silk screen characters need to be mirrored to avoid confusion with the top silk screen.
6. Network DRC inspection and structure 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.
General 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 is formally processed, 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.
This includes, but is 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.
The above is the entire process of PCB design.