Printed circuit board (PCB), also known as printed circuit board, is the supplier of electrical connection of electronic components. Its development has a history of more than 100 years. Its design is mainly layout design. The main advantage of using circuit board is that it greatly reduces the wiring and assembly errors, and improves the automation level and production labor rate. According to the number of circuit board layers, it can be divided into single board, double board, four board, six board and other multilayer circuit boards.
In recent years, China's printed circuit board manufacturing industry has developed rapidly, and its total output value ranks first in the world. With its industrial layout, cost and market advantages, China has become an Zui important PCB production base in the world. Printed circuit boards have developed from single-layer to double-layer, multilayer and flexible boards, and continue to develop in the direction of high precision, high density and high reliability. The continuous reduction of volume, the reduction of cost and the improvement of performance make the printed circuit board still maintain strong vitality in the development of electronic products in the future. The development trend of printed circuit board manufacturing technology in the future is to be high-density, high-precision, fine aperture, fine wire, small spacing, high reliability, multi-layer, high-speed transmission, light weight and thin.
The current circuit board is mainly composed of the following parts
Circuit and drawing: a circuit is a tool for conducting electricity between original parts. In addition, large copper surfaces will be designed as grounding and power layers. The circuit and drawings shall be made at the same time.
Dielectric layer: used to maintain the insulation between lines and layers, commonly known as substrate.
Through hole: the through hole can make more than two-level lines open to each other. The larger through hole can be used as part plug-in. In addition, there are non-through holes (npth), which are usually used for surface installation and positioning and fixing screws during assembly.
Brazing ink: not all copper surfaces need tin, so a layer of material (usually epoxy resin) will be printed in the area without Tin, so that the copper surface does not eat tin and avoid short circuit between non tin wires. According to different processes, it is divided into green oil, red oil and blue oil.
Wire mesh: This is an unnecessary structure. The main function is to mark the name and position frame of each component on the circuit board for maintenance and identification after assembly.
Due to the repeatability (reproducibility) and consistency of graphics, the errors of wiring and assembly are reduced, and the maintenance, debugging and inspection time of equipment are saved.
The design can be standardized to facilitate interchangeability;
It is conducive to mechanized and automatic production, improve labor productivity and reduce the cost of electronic equipment.
In particular, the bending resistance and accuracy of FPC soft plate are better applied to high-precision instruments (such as cameras, mobile phones, etc.). Camera, etc.)
Layout is to place circuit components in the wiring area of the printed circuit board. Whether the layout is reasonable not only affects the subsequent wiring work, but also has an important impact on the performance of the whole circuit board. After ensuring the circuit function and performance index, in order to meet the requirements of processing performance, inspection and maintenance, the components shall be evenly, neatly and compactly placed on the PCB to Zui greatly shorten and shorten the leads and connections between the components, so as to obtain uniform packaging density.
Arrange the position of each functional circuit unit according to the circuit flow. For input and output signals, the high-level and low-level parts shall not intersect as much as possible, and the signal transmission line Zui shall be short.