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The core of PCB design - solving problems
Posted:01:48 PM August 27, 2018 writer: G

Although the engineering designer knows that a perfect design is the best way to avoid problems, it is still a way of wasting time and wasting money while not treating the problem. For example, if problems are discovered during the electromagnetic compatibility (EMC) testing phase, a large amount of cost will be incurred, and even the initial design will need to be adjusted and re-created, which will take several months.

Challenge

Layout is a problem that designers must first face. This problem depends on some of the parts of the drawing, and 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 placed separately from the heat generating components including the power converter. For designs with multiple power settings, 12-volt 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 also have an impact on the electromagnetic performance of the circuit design. This is not only important for the performance and energy consumption of the board, but also has a great impact on the economics of the board. Therefore, all the circuit board equipment sold in Europe. All must obtain the CE mark to prove that it will not cause interference to 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 defects in the board design, these noises can be captured by the channel and radiated as small antennas, producing aliased noise and frequency anomalies.

Far-field electromagnetic interference (EMI) problems can be solved by adding filters at noise points or by using metal enclosures to shield the signal. However, due attention is paid to devices that emit electromagnetic interference (EMI) on the board, but the board can be used with a cheaper housing, which effectively reduces 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 taken seriously. Electromagnetic crosstalk can couple with the channel, disrupting the signal to noise, 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 return to normal. However, if the signal line layout can be fully considered at the beginning of the board design, the above problems can be avoided. Since the design of the board will vary depending on the device, the location of use, the different cooling requirements, and the different electromagnetic interference (EMI) conditions, the design template will come in handy.

Capacitance is also an important issue in board design that cannot be ignored, because capacitance affects the speed of signal propagation and increases power consumption. The channel will couple with the adjacent line or vertically across the two circuit layers, thereby inadvertently forming a capacitor. The above problem can be solved relatively easily by reducing the length of the parallel lines, adding a kink on one of the lines to cut off the coupling, and the like. However, this also requires the engineering designer to fully consider the production design principles, to ensure that the design is easy to manufacture, and to avoid any noise radiation caused by excessive bending angle of the line. The distance between the lines may also be too close, which will create short loops between the lines, especially at the bends of the line, and metal "whiskers" will appear over time. Design rule detection can often identify areas where the loop risk is higher than normal.

This problem is particularly prominent in the design of the ground plane. A metal circuit layer may couple all of the lines above and below it. Although the metal layer can effectively block the noise, the metal layer also generates associated capacitance, which affects the running speed of the line and increases the power consumption.

In terms of the design of multilayer boards, the design of through-holes between different board layers is probably the most controversial issue, because the through-hole design can cause many problems in the manufacture of boards. Through-holes between the board layers can affect the performance of the signal and reduce the reliability of the board design, so it should be given full attention.

Solution

In the design of printed circuit boards (PCBs), many different methods can be used to solve various problems. There are adjustments to the design itself, such as adjusting the layout of the circuit to reduce noise; there are also ways to layout the printed circuit board. Design components can be automatically installed using layout tools, but manual adjustments to the automatic layout will help improve the quality of the board design. Through this measure, design rule detection will rely on technical documentation to ensure that the board is designed to meet the requirements of the board manufacturer.

Separating the different board layers reduces the associated capacitance, but this increases the number of layers in the board, which increases cost and leads to more via problems. Although the use of orthogonal grid power supply systems and grounding line designs may increase the physical size of the board, it can effectively exploit the effectiveness of the ground plane in a two-layer board, reducing the complexity of capacitance and board manufacturing.

Design tools, including DesignSpark PCB, can help engineers solve many problems at the beginning of the design process, but engineering designers still need to have a good understanding of the design requirements of printed circuit boards (PCBs). For example, if the editor of a printed circuit board (PCB) needs to know the number of layers of the board at the beginning of the design, for example, a two-layer board requires a ground plane and a power supply. The layer consists of two separate layers. Component auto-layout technology is very useful, helping designers spend more time designing the layout area of the device, for example, if the power supply is too close to sensitive signal lines or high temperature areas. There will be many problems. In the same way, signal lines can also be routed automatically, while avoiding most of the problems, but analysis and manual operation of high-risk areas will help to greatly improve the quality of printed circuit board (PCB) design. Increase revenue and reduce overall costs.

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

These tools will also be of great help to Gerber and Excellon, helping them to print circuit and board, and through-hole drilling in order to produce the final design. In this way, the technical documentation is closely linked to the board manufacturer.

In conclusion

There are a number of issues to consider in the design of a printed circuit board (PCB), and tools including DesignSpark PCB can handle most of these problems effectively. By adopting some best practice guidelines, engineers can effectively reduce costs and improve board reliability while meeting system specifications and cornering system certification at a lower cost to avoid further problems.

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