According to the number of circuit layers: divided into single layer, double layer and multilayer board. The common multi-layer boards are generally four-layer boards or six-layer boards, and complex multi-layer boards can reach several tens of layers. PCB board has the following three main...
According to the number of circuit layers: divided into single layer, double layer and multilayer board. The common multi-layer boards are generally four-layer boards or six-layer boards, and complex multi-layer boards can reach several tens of layers.
PCB board has the following three main types of division:
Single-Sided Boards On the most basic PCB, the parts are concentrated on one side and the wires are concentrated on the other side (there is a patch element with the same side as the wire, and the plug-in device has another side). Because the wires only appear on one side, this kind of PCB is called Single-sided. Because single-board has many strict restrictions on the design circuit (because there is only one side, the wiring can not cross and must be routed alone), only the earlier circuit uses this kind of board.
To use two wires, you must have a proper circuit connection between the two sides. This "bridge" between circuits is called a via. The via hole is on the PCB, filled with or coated with a metal hole, and it can be connected to the wires on both sides. Because the area of the dual panel is double that of the single panel, the dual panel solves the difficulty of wiring in a single panel (via conduction through the hole to the other side), which is more suitable for use in more complex circuits than a single panel.
The board uses more single or double sided wiring boards. Uses a double-sided inner layer, two single-sided outer layers or two double-sided inner layers, and two single-sided printed wiring boards, alternating with a positioning system and insulating bonding material and conductive patterns The printed circuit board that is interconnected according to design requirements becomes a four-layer, six-layer printed circuit board, also called a multilayer printed circuit board. The number of layers on the board does not mean that there are several layers of independent wiring layers. In special cases, empty layers are added to control the board thickness. Usually, the number of layers is even, and the outermost two layers are included. Most of the motherboards are 4- to 8-layer structures, but it is technically possible to implement nearly 100-layer PCB boards. Most large-scale supercomputers use quite a few layers of motherboards, but since such computers can already be replaced by clusters of many ordinary computers, super-multi-layer boards have gradually become unused. Because the layers in the PCB are tightly integrated, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can still see it.
PCB can be applied more and more widely because it has many unique advantages, as outlined below.
Density can be increased. For decades, the high density of PCBs has grown as integrated circuits have become more integrated and installation technology has advanced.
High reliability. Through a series of inspections, tests, and aging tests, the PCB can be reliably operated for a long period of time (usually 20 years).
Designability. For PCB performance (electrical, physical, chemical, mechanical, etc.) requirements, PCB design can be achieved through design standardization, standardization, etc., with short time and high efficiency.
Productivity. With modern management, we can conduct standardization, scale (quantity), automation and other production, and ensure the consistency of product quality.
Testability. Established a relatively complete test method, test standards, a variety of test equipment and instruments to detect and identify the qualification and service life of PCB products.
Assemblability. PCB products not only facilitate the standard assembly of various components, but also can be automated, large-scale mass production. At the same time, PCBs and various component assembly parts can also be assembled to form larger parts and systems up to the complete machine.
Maintainability. Since PCB products and various component assembly parts are produced with standardized design and scale, these components are also standardized. Therefore, once the system fails, it can be quickly, easily, and flexibly replaced, quickly recovering the system. Of course, you can also give more examples. For example, the system is miniaturized, lightweight, and the signal transmission speed is increased.
Hard and soft classification
Divided into rigid circuit boards and flexible circuit boards, soft and hard boards. The PCB shown in the first figure below is generally called a Rigid PCB, and the yellow line in the second figure is called a Flexible (or Flexible) PCB. The intuitive difference between a rigid PCB and a flexible PCB is that the flexible PCB is bendable. The common thicknesses of rigid PCBs are 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm, etc. The common thickness of the flexible PCB is 0.2mm. The place where the parts are to be welded will be thickened at the back, and the thickness of the thickened layer is 0.2mm and 0.4mm. The purpose of understanding these is to provide a spatial reference for structural engineers when designing them. Rigid PCB materials commonly include: phenolic paper laminates, epoxy paper laminates, polyester glass felt laminates, epoxy glass cloth laminates; flexible PCB material common include: polyester film, polyimide Amine film, fluorinated ethylene propylene film.
Copper clad laminates are the substrate material used to make printed circuit boards. It is used to support various components and to achieve electrical or electrical insulation between them.
PCB aluminum substrates (metal-based heat sinks include aluminum, copper, and iron substrates) are low-alloy Al-Mg-Si based high-plasticity alloy plates (structures shown below), which have good thermal and electrical insulation properties. And machining performance, now mainstream aluminum substrate Forslet
Rigid and flex PCB
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