Printed circuit board (PCB) design refers to the design of schematic drawings, circuit layout, and production of circuit boards at the lowest possible cost. In the past, this usually required the help of expensive special tools to complete, but now, with the increasing availability of free high-performance software tools and design models, the board designer's design speed is greatly accelerated.
Even though engineers know that a perfect design is the best way to avoid problems, this is a waste of time and money, and a solution to the symptoms rather than the root cause. For example, if a problem is found during the electromagnetic compatibility (EMC) testing phase, it will cause a lot of cost investment, and even need to adjust and remake the original design plan, which will take several months.
Layout is one of the first issues designers face. This question depends on what is part of the drawing, some equipment needs to be set together based on logical considerations. It should be noted, however, that temperature-sensitive components, such as sensors, should be located separately from heat-generating components, including power converters. For designs with multiple power supply settings, the 12 volt and 15 volt power converters can be placed in different places on the board, as the heat and electrical noise they generate can affect other components as well as the reliability and performance of the board .
The above components will also affect the electromagnetic performance of the circuit design, which is not only very important for the performance and energy consumption of the circuit board, but also has a great impact on the economy of the circuit board, so all circuit board equipment sold in Europe must obtain the CE mark to prove that it will not cause interference to other systems. However, this is usually only from the power supply side, there are many devices that emit noise, such as DC-DC converters, and high-speed data converters. Due to flaws in the board design, this noise can be picked up by the channel and radiated as a small antenna, creating spurious noise and areas of frequency anomaly.
Far-field electromagnetic interference (EMI) problems can be addressed by adding filters at noisy points or using metal enclosures to shield signals. However, paying sufficient attention to the devices on the circuit board that can emit electromagnetic interference (EMI) allows the circuit board to use a cheaper housing, thereby effectively reducing the cost of the entire system.
In the design process of the circuit board, electromagnetic interference (EMI) is indeed a factor that has to be paid attention to. Electromagnetic crosstalk can couple to the channel, scrambling the signal into noise and affecting the overall performance of the board. If the coupling noise is too high, the signal may be completely covered, so a more expensive signal amplifier must be added to restore normal. However, if the signal line layout can be fully considered at the beginning of the circuit board design, the above problems can be avoided. Since the design of the circuit board will vary according to different devices, different places of use, different heat dissipation requirements, and different electromagnetic interference (EMI) conditions, then the design template will come in handy.
Capacitance is also an important issue that cannot be ignored in circuit board design, because capacitance will affect the propagation speed of signals and increase power consumption. Channels can couple to adjacent lines or cross two circuit layers vertically, creating a capacitor inadvertently. These problems can be solved relatively easily by reducing the length of the parallel lines, adding a kink to one of the lines to break the coupling, etc. However, this also requires engineering designers to fully consider production design principles to ensure that the design is easy to manufacture while avoiding any noise radiation caused by excessively large line bending angles. It is also possible for the lines to be too close together, which will create short loops between the lines, especially at line bends, and over time, metallic "whiskers" will appear. Design rule checking can often flag areas where loop risk is higher than normal.
This problem is particularly prominent in the design of the ground plane. A metal circuit layer that has the potential to couple to all traces above and below it. Although the metal layer can effectively block noise, the metal layer will also generate associated capacitance, which will affect the running speed of the circuit and increase power consumption.
As far as the design of multi-layer circuit boards is concerned, the design of through holes between different circuit board layers is probably the most controversial issue, because the design of through holes will bring many problems to the production and manufacture of circuit boards. The through holes between the board layers will affect the performance of the signal and reduce the reliability of the board design, so it should be given full attention.
solution:
During the design process of a printed circuit board (PCB), many different approaches can be taken to solve various problems. Among them are the adjustment of the design plan itself, such as adjusting the circuit layout to reduce noise; there are also methods for the layout of the printed circuit board. Design components can be automatically placed by layout tools, but the ability to manually adjust the automatic layout will help improve the quality of the board design. Through this measure, the design rule check will make sure that the design of the circuit board can meet the requirements of the circuit board manufacturer with the help of the technical file.
Separating different board layers can reduce the associated capacitance, but this will increase the number of board layers, which will increase the cost and cause more via problems. Although the design of the orthogonal grid power supply system and the ground line may increase the physical size of the circuit board, it can effectively play the role of the ground plane in the double-layer circuit board, reduce the capacitance and the complexity of the circuit board manufacturing.
Many PCB design tools can help engineers solve many problems at the beginning of design, but engineers still need to have a full understanding of the design requirements of printed circuit boards (PCBs). For example, if the editor of the printed circuit board (PCB proofing) needs to know the number of layers of the circuit board at the beginning of the design, for example, a double-layer circuit board needs to have a ground layer and a The power layer is composed of two independent board layers. Component automatic layout technology is very useful and can help designers spend more time designing the layout area of the device. For example, if the power supply device is too close to sensitive signal lines or areas with high temperature, Many problems will arise. Similarly, signal lines can be routed automatically, avoiding most problems, however, analysis and manual operation of high-risk areas will help greatly improve the quality of printed circuit board (PCB) designs , Increase revenue and reduce overall cost.
Design rule checking is also a very powerful tool for checking lines to ensure that lines are not too close together, resulting in short loops. However, the overall design still has a high economic value. Design planning inspection tools can also be used to inspect and adjust power and ground planes to avoid large parasitic capacitance areas.
The above-mentioned tools will also be of great help to Gerber and Excellon, which will help them to carry out wiring and circuit board printing, and through-hole drilling in order to produce the final design. In this way, the technical file is closely linked with the board manufacturer.
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