What are the important techniques for PCB wiring?

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What are the important techniques for PCB wiring? [Copy link]

What are the important skills for PCB wiring? In PCB design, wiring is an important step in completing product design. The quality of PCB wiring will directly affect the performance of the circuit. Below, we have summarized six important skills for PCB wiring, hoping to help you. Six important skills for PCB wiring I. Number of layers and design of PCB (1) The size of the circuit board and the number of wiring layers need to be determined at the beginning of the design. If the design requires the use of high-density ball grid array (BGA) components, the minimum number of wiring layers required for wiring these devices must be considered. The number of wiring layers and the stack-up method will directly affect the wiring and impedance of the printed lines. The size of the board helps determine the stack-up method and the width of the printed lines to achieve the desired design effect. (2) When designing high-speed multi-layer PCBs, the most important thing to pay attention to is your layer design, that is, how you divide the signal lines, power lines, ground, and control lines on each layer. The general principle is that analog signals and analog signal grounds should be guaranteed to have at least one separate layer. It is also recommended that the power supply use a separate layer. II. Order of component placement (1) Place components that are fixed in a tight fit with the structure, such as power sockets, indicator lights, switches, connectors, etc. After these components are placed, use the software's LOCK function to lock them so that they will not be moved by mistake in the future; (2) Place special components and large components on the circuit, such as heating components, transformers, ICs, etc.; (3) Place small components. Distance of components from the edge of the board: If possible, all components should be placed within 3mm from the edge of the board or at least greater than the thickness of the board. This is because during mass production of assembly line plug-ins and wave soldering, guide rails should be provided for use. At the same time, it is also to prevent the edge from being damaged due to shape processing. If there are too many components on the printed circuit board and it is necessary to exceed the 3mm range, a 3mm auxiliary edge can be added to the edge of the board. The auxiliary edge has a V-shaped groove and can be broken by hand during production. 3. Routing of printed circuit boards The layout of printed conductors should be as short as possible, especially in high-frequency circuits; the bends of printed conductors should be rounded, while right angles or sharp angles will affect electrical performance in high-frequency circuits and high wiring density. When wiring two panels, the conductors on both sides should be perpendicular, oblique, or curved to avoid parallelism to reduce parasitic coupling; the printed conductors used as input and output of the circuit should be avoided as much as possible to avoid adjacent parallelism to avoid feedback. It is best to add a ground wire between these conductors. 4. Layout with good heat dissipation There are three main sources of heat in PCB: (1) heat generated by electronic components; (2) heat generated by the PCB itself; (3) heat transmitted from other parts. Among these three heat sources, the heat generated by components is the largest and is the main heat source, followed by the heat generated by the PCB board. The heat transmitted from the outside depends on the overall thermal design of the system and is not considered for the time being. The purpose of thermal design is to take appropriate measures and methods to reduce the temperature of components and PCB boards so that the system can work normally at a suitable temperature. This is mainly achieved by reducing heat generation and accelerating heat dissipation. V. Design Rule Check (DRC) After the wiring design is completed, it is necessary to carefully check whether the wiring design complies with the rules set by the designer. At the same time, it is also necessary to confirm whether the rules set meet the requirements of the printed circuit board production process. The general inspection includes the following aspects: (1) Whether the distance between lines, lines and component pads, lines and through holes, component pads and through holes, and through holes are reasonable and meet production requirements. (2) Whether the width of the power line and the ground line is appropriate, and whether the power and ground lines are tightly coupled (low wave impedance)? Is there any place in the PCB where the ground line can be widened? (3) Whether the best measures have been taken for key signal lines, such as the shortest length, adding protection lines, and clearly separating input and output lines. (4) Whether the analog circuit and digital circuit parts have their own independent ground lines. (5) Whether the graphics added to the PCB later (such as icons, annotations) will cause signal short circuits. (6) Modify some undesirable line shapes. (7) Are process lines added to the PCB? Does the solder mask meet the requirements of the production process? Is the size of the solder mask appropriate? Is the character mark pressed on the device pad to avoid affecting the quality of the electrical equipment? (8) Is the outer frame edge of the power layer in the multilayer board reduced? If the copper foil of the power layer is exposed outside the board, it is easy to cause a short circuit. Sixth, check whether there are sharp angles, impedance discontinuities, etc. (1) For high-frequency current, when the bend of the wire is a right angle or even a sharp angle, the magnetic flux density and electric field strength are relatively high near the bend, which will radiate strong electromagnetic waves, and the inductance here will be relatively large, and the inductive reactance will be larger than that of an obtuse angle or a rounded angle. (2) For the bus wiring of digital circuits, the wiring bend is an obtuse angle or a rounded angle, and the area occupied by the wiring is relatively small. Under the same line spacing conditions, the width occupied by the total line spacing is 0.3 times less than that of a right-angle bend. (The above content is compiled from the Internet, the copyright belongs to the original author, if there is any infringement, please contact and delete.) 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