5 common PCB design problems you encounter.
1. What is the 20H principle in PCB design problems?
The 20H principle is the shrinking distance of the power layer from the ground.
It is also used to suppress the edge radiation effect. The board’s edge will emit electromagnetic interference outside. The EMC is improved by shrinking the power layers inward. The electric field is confined to the edge of the ground by a 20H shrinkage; a 100H shrunkage encloses the electric field at 98%.
In general, the PCB design for the power supply layer is smaller than the ground layer by 1mm to comply with the 20H principle.
2. PCB design problems: How can PCBs reflect the 3W and 20H principles?
It is simple to apply the 3W principle to the PCB design. The center of the lines and the spacing between the lines can be 3 times as wide as the line, for example, the 6 mil line width.
In Allegro, you can set the line-to-line rule to 12mil and then calculate the edge-to edge spacing using the software.
In order to reflect this 20H principle in PCB design, we generally divide the PCB into the plane layer and the power layer. The ground layer is then shrunk by 1mm. Then, in the 1mm band of shrinkage to play over the shielding layer above the hole, one 150mil.
3. PCB design Problems: What is the difference between PCB signal lines?
The PCB signal lines are divided into two types, the first is a Microstrip Line, and the second is a Tape Line.
As shown in the following figure, the top part of the blue block represents a microstrip (microstrip) line. The microstrip (microstrip) line of one side can be formed by radiation interference or the surrounding radiation, while the other PCB side attached to the dielectric forms part of an electric field in the air. The signal transmission speed of a microstrip is much faster than a stripline. This is its main advantage.
Stripline: As shown in the image below, stripline/double-stripline is buried within the PCB. The blue part of the board is the conductor and the green part of the board is the dielectric insulator. Stripline is embedded between two layers of conductors.
Stripline: Because it is embedded between two layers of conductors and its electric field distribution will be in both packages, the stripline will not emit energy or be affected by external radiation interference. The stripline transmits signals slower than the microstrip because it’s surrounded by dielectrics.
4.What is EMC and what does it do?
EMC is an abbreviation for Electro Magnetic Compatibility. Translated as electromagnetic compatibility it refers to equipment or systems that can operate normally in their electromagnetic environment and do not cause any unacceptable electromagnetic harassment.
Sensor electromagnetic compatibility is the ability of the sensor to adapt to an electromagnetic environment and maintain its inherent performance. It also refers to its ability to perform the specified function. It has two requirements: the sensor must not exceed certain limits in normal operation, and it must be placed in an environment with certain levels of electromagnetic interference.
5.How can I differentiate between digital and analog ground in PCB design design?
The following are the general handling methods for analog ground and digital ground:
The schematic diagram shows the analog and digital areas of the PCB’s ground plane, which are connected directly to DGND and AGND respectively.
A magnetic bead connects the digital ground to the analog ground;
The analog ground is connected with the digital ground using a capacitor and the capacitive isolation principle through the cross.
Inductance values from tens to hundreds of uH for digital ground and analog ground;
Connecting digital ground to analogue ground is done with a zero-ohm resistance;
In summary, capacitors do not connect to DC. This results in a floating earth. The capacitors do not pass DC. This will cause static build-up and pressure differences. Touching the chassis can also numb your fingers.
You will only make the problem worse if you connect the capacitor parallel to the bead. The bead will pass straight through the capacitor and it’ll fail. It would be unorthodox to connect them in series.
Inductors have large sizes, a large number of spurious parameters and unstable characteristics. They also do not control discrete distribution parameters well. Inductors can also be LC resonant, have a large amount of spurious parameters and are effective at reducing noise.
The magnetic bead’s equivalent circuit is the same as a band resistive trap. However, you cannot predict the noise. How do you choose the model? Besides, noise frequency isn’t always fixed.
The 0 Ohm Resistor is equivalent with a very narrow path of current, which can limit the loop current effectively and suppress noise. Resistors are stronger than magnetic beads because they have a lower attenuation across all frequency bands.
The key is to connect the analog and digital ground at the same point. The 0-ohm resistance is used to connect different types of grounds. Beads are used with high-frequency devices, small capacitors for signal coupling at high frequencies and inductors for low-power high-frequency.
FAQ:
1. What are the most common pcb design problems?
2. How can I avoid signal integrity issues while designing a PCB?
3. What is the best way to minimize EMI/EMC pcb design problems?
4. How can I troubleshoot a short circuit on my PCB?
5. What is the best way to prevent overheating in PCB components?
6. What are the common causes of PCB layout errors, and how can I avoid them?
7. How can I identify and fix issues with pad misalignment during PCB design?
8. What is the best way to ensure proper grounding in PCB design?
9. How can I avoid component placement issues in my PCB design?
10. What are the best practices for PCB design to ensure manufacturability and reliability?
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