Problems easily encountered in PCB design

The design of printed circuit board (PCB) is a key link in the development of electronic products, and its quality directly affects the performance and reliability of products. The following will share some common problems in PCB design and provide their solutions, hoping to help our friends.

First, the problem of plate selection

Problem: When designing high-speed PCB (frequency greater than GHz), improper material selection leads to signal attenuation.

Solution:
Choose plates with appropriate dielectric constant and dielectric loss, such as avoiding using FR-4 material in high frequency band.

Second, the problem of high frequency interference

Problem: There is serious interference between high-speed signal and analog signal.

Solution:
Enlarge the distance between high-speed signal and analog signal.

Add ground guard/shunt traces beside the analog signal.

Third, the signal integrity problem

Problem: Impedance mismatch leads to signal reflection and crosstalk.

Solution:
The topology of termination and adjustment wiring is adopted.
Make sure that the two lines of the differential pair have the same length and the spacing remains the same.

Fourth, the complexity of wiring

Problem: Multi-layer PCB wiring space is limited and wiring is difficult.

Solution:
Plan the layout in advance, and focus on placing devices with strong correlation according to functional modules.
Adjust wiring rules and line width settings to make room for wiring.

V. Power supply integrity issues

Problem: Voltage fluctuation and noise appear on the power plane.

Solution:
Reasonably plan the power supply layer and stratum, and try to be adjacent.
Increase decoupling capacitance and select appropriate capacitance.

Sixth, the heat dissipation problem

Problem: High-power devices have poor heat dissipation, resulting in high temperature.

Solution:
Heat dissipation holes or heat dissipation grooves are added below or around the high-power device.
Laying a large area of radiating copper foil or installing suitable radiating fins.

Seven, electromagnetic compatibility (EMC) problem

Problem: PCB board radiates too much electromagnetic interference and is vulnerable to external interference.

Solution:
Use stratum as shielding layer to reduce external radiation.
Control the area of signal loop and shorten the length of signal line.
Add a filter circuit at the input and output interface.

Eight, PCB board short circuit problem

Problem: improper design of welding pad and wrong direction of parts lead to short circuit.

Solution:
Change the circular pad into an oval shape to increase the distance between points.
Modify the direction of the part so that it is perpendicular to the tin wave.
Make sure that the solder joint is more than 2mm away from the line.

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