Accuracy and consistency: 5G products have increased the data signal transmission rate from 25Gbps to 56Gbps, and have put forward stricter requirements for product impedance, loss, etc. The product impedance requirement has been increased from 10% to 5%, and the line width tolerance has been increased from 20% to 10%. The impact of line flatness on the signal is also significant.

　　From the perspective of the influencing factors of impedance control, the size of impedance tolerance is influenced by the dielectric thickness tolerance, copper thickness tolerance, and current control accuracy. As shown in the following figure, the inner layer impedance tolerance has been reduced from 10% to 5%, the dielectric thickness tolerance should be controlled at ± 7%, the copper thickness tolerance should be controlled at ± 3%, the line width tolerance should be controlled at ± 8%, and the outer layer impedance should also be controlled. This is closely related to sheet metal, PCB engineering design, process technology, and process control.