PCB Fabrication

PCB ( Printed Circuit Board), Printed circuit board, also known as printed circuit board

by:A-TECH      2020-05-02
After the electronic equipment adopts printed boards, due to the consistency of similar printed boards, errors in manual wiring are avoided, and automatic insertion or mounting of electronic components, automatic soldering and automatic detection can be realized, ensure the quality of electronic equipment, improve labor productivity, reduce costs, and facilitate maintenance. According to the number of circuit layers, it is divided into single panel, double panel and multilayer board. Common multi-layer boards are generally 4-layer boards or 6-layer boards, and complex multi-layer boards can reach dozens of layers. Rigid circuit board and flexible circuit board, soft and hard combination board. 1mil = 25. 4um 0. 1MM = 100um = 4mil1OZ = 35um Hoz = 18um 1, single panel (Single-Sided Boards) We just mentioned that on the most basic PCB, parts are concentrated on one side and wires are concentrated on the other side. Because wires only appear on one side, we call this PCB a single panel (Single-sided). Because the single panel has many strict restrictions on the design line ( Because there is only one side, the wiring can not cross and must be around a separate path) , So only early circuits use such boards. Second, the double panel (Double-Sided Boards)This kind of circuit board has wiring on both sides. However, to use wires on both sides, there must be appropriate circuit connections between the two sides. The 'bridge' between this kind of circuit is called the guide hole (via). The guide hole is a small hole on the PCB filled with or coated with metal, which can be connected with wires on both sides. Because the area of the double-panel is twice as large as that of the single-panel, and because the wiring can interlace with each other (Can go around to the other side) It is more suitable for circuits that are more complex than single-panel. Third, multi-layer board (Multi-Layer Boards) In order to increase the area that can be routed, the multi-layer board uses more single or double-sided wiring boards. The multi-layer board uses several double-sided boards and sticks them firmly after putting a layer of insulating layer between each layer of boards (Pressing). The number of layers of the Board represents several independent wiring layers. Usually, the number of layers is even and contains the outermost two layers. Most motherboards are 4 to 8 layers of structure, but technically it can achieve nearly 100 layers of PCB boards. Large supercomputers mostly use quite a few layers of motherboards, but because such computers can already be replaced by clusters of many ordinary computers, super-layers have gradually become unused. Because the layers in the PCB are tightly combined, it is generally not easy to see the actual number, but if you look closely at the motherboard, you may be able to see it. The guide hole we just mentioned (via) If it is applied on a double-sided board, it must be through the entire board. However, in the multi-layer board, if you only want to connect some of the lines, the guide hole may waste some line space in other layers. Buried hole (Buried vias)And blind holes (Blind vias) Technology can avoid this problem because they only penetrate a few layers. The blind hole is to connect several layers of internal PCB with the surface PCB without penetrating the whole board. Buried holes are only connected to the internal PCB, so they cannot be seen from the surface alone. In the multi-layer PCB, the whole layer is directly connected to the ground wire and power supply. So we classify each layer as a signal layer (Signal), Power layer (Power)Or the ground layer (Ground). If the parts on the PCB need different power supplies, usually this type of PCB will have more than two layers of power and wire layers.
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