The design of the printed circuit board starts from determining the size of the board. The size of the printed circuit board is limited by the size of the chassis shell, so it is appropriate to fit it into the shell. Secondly, the connection mode between the printed circuit board and external components (mainly Potentiometer, socket or other printed circuit board) should be considered. Printed circuit boards are generally connected to external components through plastic wires or metal isolation wires. But sometimes it is also designed in the form of a socket. Namely, when installing a plug-in printed circuit board in the device, a contact position that serves as a socket should be reserved. For larger components installed on printed circuit boards, metal accessories should be added for fixation to improve vibration and impact resistance.
2. The basic method of wiring diagram design requires a complete understanding of the specifications, dimensions, and areas of the selected components and various sockets; Reasonable and careful consideration should be given to the arrangement of the positions of each component, mainly from the perspective of electromagnetic compatibility, anti-interference, short wiring, less crossing, power supply, ground path, and decoupling. After the location of each component is determined, it is the connection of each component. Connect the relevant pins according to the circuit diagram. There are many ways to complete the connection. The design of the printed circuit diagram includes Computer-aided design and manual design.
The most primitive method is to arrange the layout manually. This is quite cumbersome and often requires several iterations before the final completion, which can also be achieved without other drawing equipment. This manual arrangement method of layout is also very helpful for designers who are just learning printing board drawings. Computer assisted drawing, there are various drawing software available with different functions, but overall, drawing and modification are more convenient, and can be saved, stored, and printed.
Next, determine the required size of the printed circuit board and preliminarily determine the position of each component according to the schematic diagram. After continuous adjustment, the layout is more reasonable. The wiring arrangement between each component in the printed circuit board is as follows:
(1) Cross circuits are not allowed in printed circuits. For lines that may cross, two methods can be used: "drilling" and "winding". That is, to allow a certain lead to "drill" through the gap at the foot of other resistors, capacitors, or transistors, or to "wind" through one end of a possible cross lead. In special cases, the circuit is very complex, and to simplify the design, wire bridging is also allowed to solve the problem of cross circuits.
(2) There are two installation methods for components such as resistors, diodes, and tubular capacitors: "vertical" and "horizontal". Vertical refers to the installation and welding of component bodies perpendicular to the circuit board, which has the advantage of saving space. Horizontal refers to the installation and welding of component bodies parallel and tightly attached to the circuit board, which has the advantage of good mechanical strength during component installation. The hole spacing of these two different installation components on the printed circuit board is different.
(3) The grounding point of the same level circuit should be as close as possible, and the power filter capacitor of the current level circuit should also be connected to the grounding point of that level. Especially, the grounding points of the base and emitter of this level transistor should not be too far away, otherwise the copper foil between the two grounding points is too long, which can cause interference and self-excitation. Using this "one point grounding method" in the circuit is more stable and less prone to self-excitation.
Printed circuit boards are structural components formed by insulating materials supplemented by conductor wiring. When making the final product, integrated circuits, transistors, diodes, passive components (such as resistors, capacitors, connectors, etc.), and various other electronic components are installed on it. By connecting wires, electronic signal connections and functions can be formed. Therefore, printed circuit boards are a platform that provides component connections, serving as the foundation for connecting components.
Due to the fact that printed circuit boards are not general end products, the definition of their names is somewhat confusing. For example, motherboards used in personal computers are called motherboards and cannot be directly referred to as circuit boards. Although there are circuit boards in motherboards, they are not the same. Therefore, when evaluating the industry, it cannot be said that the two are related but cannot be said to be the same. For example, because there are integrated circuit parts loaded on the circuit board, the news media refers to it as an IC board, but in essence, it is not equivalent to a printed circuit board.
In the context of the trend towards multifunctional and complex electronic products, the contact distance of integrated circuit components is reduced, and the speed of signal transmission is relatively increased. This is followed by an increase in the number of connections and a localized reduction in the length of inter point wiring. These require the application of high-density wire configuration and micropore technology to achieve the goal. Wiring and bridging are basically difficult to achieve for single and double-sided boards, resulting in circuit boards becoming more multi-layer. Additionally, due to the continuous increase of signal lines, more power and ground layers are necessary means of design, which has made multilayer printed circuit boards more common.
For the electrical requirements of high-speed signals, circuit boards must provide impedance control with AC characteristics, high-frequency transmission capability, and reduce unnecessary radiation (EMI). Adopting the structure of Stripline and Microstrip, multi-layer design becomes necessary. In order to reduce the quality problem of signal transmission, insulating materials with low Dielectric coefficient and low attenuation rate will be used. In order to meet the miniaturization and array of electronic components, the density of circuit boards will also be continuously increased to meet the demand. The emergence of component assembly methods such as BGA (Ball Grid Array), CSP (Chip Scale Package), DCA (Direct Chip Attachment) has further promoted printed circuit boards to unprecedented high-density levels.
Holes with a diameter less than 150um are referred to as micropores (Microvia) in the industry. Circuits made using the geometric structure technology of these micropores can improve the efficiency of assembly, space utilization, and other aspects. At the same time, it is also necessary for miniaturization of electronic products.
