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The core of PCB design and solutions

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The design of a printed circuit board (PCB) refers to the layout of the circuit through the design principle drawing to produce the circuit board at the lowest possible cost. In the past, this usually required expensive specialized tools to complete, but now, with the increasing popularity of free high-performance software tools, such as DesignSparkPCB, and design models, circuit board designers have greatly accelerated the design speed.

Although the engineering designer knows that a perfect design solution is the best way to avoid problems, it is still a way to waste time and money while simultaneously treating symptoms. For example, if problems are discovered during the EMC testing phase, significant costs will be incurred, and even the original design plan will need to be adjusted and re-created, which will take several months.

Challenge

Layout is a problem that designers must face first. This problem depends on part of the drawing, some devices need to be set together based on logical considerations. However, it should be noted that temperature-sensitive components, such as sensors, should be set separately from the heat-generating components including the power converter. For designs with multiple power settings, 12- and 15-volt power converters can be placed in different locations on the board, because the heat and electronic noise they generate can affect the reliability and performance of other components and boards. .

The above components will also affect the electromagnetic performance of the circuit design, which is not only important for the performance and energy consumption of the circuit board, but also has a great impact on the economics of the circuit board, so all the circuit board equipment sold in Europe All must obtain the CE mark to prove that it will not interfere with other systems. However, this is usually only in terms of power supply, and there are many devices that emit noise, such as DC-DC converters, and high-speed data converters. Due to the circuit board design flaws, these noises can be captured by the channel and radiated as small antennas, resulting in noise and frequency anomalies.

Far-field electromagnetic interference (EMI) problems can be solved by installing filters at noise points or by shielding the signal with a metal case. However, sufficient attention is paid to equipment that can release electromagnetic interference (EMI) on the circuit board, but it can make the circuit board use a cheaper housing, thereby effectively reducing the cost of the entire system.

In the circuit board design process, electromagnetic interference (EMI) is indeed a factor that must be taken seriously. Electromagnetic crosstalk can be coupled with the channel, thereby disorganizing the signal into noise, affecting the overall performance of the circuit board. If the coupling noise is too high, the signal may be completely covered. Therefore, a more expensive signal amplifier must be added in order to return to normal. However, if the layout of the signal line can be fully taken into account at the beginning of the circuit board design, the above problems can be avoided. Because the design of the circuit board will vary according to different equipment, different use locations, different heat dissipation requirements, and different electromagnetic interference (EMI) conditions, the design template will be deployed.

Capacitance is also an important issue in circuit board design because it can affect the speed of signal propagation and increase power consumption. The channel will couple with the next line or cross the two circuit layers vertically, creating a capacitor inadvertently. This problem can be solved relatively easily by reducing the length of the parallel lines, adding a kinks to one of the lines, and cutting off the coupling. However, this also requires the engineering designer to fully consider the principles of production design, to ensure that the design scheme is easy to manufacture, and to avoid any noise radiation due to the excessive bending angle of the line. The distance between the lines may also be too close, which will create a short circuit between the lines, especially at the bends of the lines. Metal whiskers will appear over time. Design rule testing can often indicate areas where the risk of the circuit is higher than normal.

This problem is particularly prominent in the design of ground planes. A metal circuit layer may form a coupling with all the lines above and below it. Although the metal layer does effectively block noise, the metal layer also generates associated capacitance, which affects the operating speed of the circuit and increases the power consumption.

For the design of multi-layer circuit boards, the design of via holes between different circuit board layers is probably the most controversial issue, because through-hole design will create many problems for the manufacture of circuit boards. The through holes between the circuit board layers will affect the signal performance and reduce the reliability of the circuit board design. Therefore, sufficient attention must be paid to it.

Solution

In the design process of a printed circuit board (PCB), many different methods can be taken to solve various problems. Among them are the adjustment of the design scheme itself, such as adjusting the layout of the circuit to reduce noise; there are also methods for the layout of printed circuit boards. Design elements can be automatically installed by the layout tool, but if you can manually adjust the automatic layout will help improve the quality of the board design. Through this measure, design rule detection will use technical documents to ensure that the design of the circuit board can meet the requirements of the circuit board manufacturer.

Separating the different circuit board layers can reduce the associated capacitance. However, this will increase the number of layers on the circuit board, which will increase the cost and lead to more problems with through-holes. Although the use of orthogonal grid power supply systems and grounding circuit designs may increase the physical size of the circuit board, it can effectively function as a ground plane in a double-layer circuit board, reducing the complexity of the capacitance and circuit board manufacturing.

Design tools, including DesignSpark PCB, can help engineering designers solve many problems at the beginning of design. However, engineering designers still need to have a thorough understanding of the design requirements for printed circuit boards (PCBs). For example, if an editor of a printed circuit board (PCB) needs to know the layer number of the circuit board at the beginning of the design, for example, a two-layer circuit board, it needs a ground plane and a power supply. The layer consists of two mutually independent layers.

The usefulness of automatic component placement technology can help designers spend more time designing the device's layout area. For example, if the power supply equipment is too close to a sensitive signal line or a high temperature area, There will be many problems. In the same way, signal lines can also be automatically routed while avoiding most problems. However, analyzing and manually manipulating high-risk areas will greatly improve the quality of printed circuit board (PCB) designs. , increase revenue, reduce overall costs.

Design rule detection is also a very powerful tool that can detect the line and ensure that the distance between the lines is not too close, resulting in a short circuit. However, the overall design still has high economic value. The design planning inspection tool can also be used to detect and adjust the power and ground planes to avoid creating large areas of associated capacitance.

The above tools will also be of great help to Gerber and Excellon, which will help them in the production of final design products, such as circuit and board printing, and through-hole drilling. As a result, the technical documents are closely linked with the circuit board manufacturers.

In conclusion

Many issues need to be considered in the design process of a printed circuit board (PCB), and tools including DesignSparkPCB can effectively handle most of them. By adopting some best-practice guidelines, engineering designers can effectively reduce costs, increase the reliability of the board, meet the requirements of the system specifications, bend the system certification at a lower cost, and avoid more problems.

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