How does the PCB manufacturing process achieve a 4-layer board doing 50 ohm pcb impedance?

PCB impedance is the impedance formed by the capacitance and inductance of the insulation and wires around the signal lines on the PCB board. The size of the impedance depends on the frequency of the signal and the design of the PCB board, and it has an important impact on the quality and stability of the signal transmission of the board. PCB impedance is a very important parameter in high frequency signal transmission.

Calculation of PCB Impedance

The formula for PCB impedance is: ρ = sqrt((L/C)), where L is the inductance around the signal line and C is the capacitance around the signal line. The values of capacitance and inductance constituted by insulation and wires can be calculated by circuit simulation software.

PCB impedance matching

During signal transmission, if the impedance of the signal line is not matched, problems such as reflection, crosstalk, and timing instability will occur. Therefore, in the design of the PCB board, the impedance of the signal line needs to be controlled within an appropriate range to ensure stable signal transmission. The method of adding terminating resistors or capacitors to the signal lines is usually used to achieve impedance matching.

Measurement of PCB Impedance

In order to verify whether the impedance of the PCB board is within the design range, impedance measurement is required. Commonly used impedance measurement methods include the bridge method, capacitance inductance meter method and network analyzer method. Among them, the network analyzer method is the most commonly used method, which can measure the impedance of different points on the signal line and analyze the change of impedance.

In conclusion, PCB impedance is one of the important parameters to measure the signal transmission quality of PCB board. In the design and manufacturing process of PCB boards, special attention needs to be paid to the calculation, matching and measurement of impedance to ensure the stability and reliability of the board.

How to realize a 4-layer board doing 50 ohm impedance?

First, determine the impedance value that needs to be matched. In this example, we need to do 50 ohm impedance matching.

Next, calculate the required line width and spacing according to the formula. In this example, we use the formula: Z0 = √(L/C), where L is the inductance and C is the capacitance. By doing this calculation, we can get the desired line width and spacing.

Then, the wiring is done based on the calculated line width and spacing. In this example, we use a 4-layer board for wiring, and the line width and spacing of each layer need to be consistent to ensure impedance matching.

Finally, the impedance match is verified through testing. In this example, we use a network analyzer to conduct the test, and if the test result meets the requirements, it means that the impedance matching is successful.

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