PCB News - What is the reason why the impedance cannot be missing in the PCB multi-layer circuit board

What is the reason why the impedance cannot be missing in the PCB multi-layer circuit board

PCB multilayer circuit board Impedance refers to the resistance and the parameters of reactance, which hinder the alternating current. In the production of PCB multilayer circuit boards, impedance processing is essential. Why do PCB multilayer circuit boards need impedance?
1. In the production process of PCB multi-layer circuit boards, they have to go through processes such as copper sinking, tin electroplating (or chemical plating, or thermal spray tin), connector soldering, etc., and the materials used in these links must ensure that the resistivity is low. In order to ensure that the overall impedance of the circuit board is low and meets the product quality requirements, it can operate normally.
2. Tinning of PCB multi-layer circuit boards is the most prone to problems in the production of multi-layer circuit boards, and it is a key link that affects impedance. The biggest defect of the electroless tin coating is easy discoloration (easy to be oxidized or deliquescent) and poor solderability, which will lead to difficult soldering of the circuit board, high impedance, poor electrical conductivity, or instability of the overall board performance.

3. The PCB circuit board (bottom of the board) should consider plugging and installing electronic components. After the later SMT patch is plugged in, it is also necessary to consider issues such as conductivity and signal transmission performance, so the lower the impedance is required. Good, especially for microwave signal equipment, the required resistivity is: less than 1&TImes;10-6 per square centimeter.
4. There are various signal transmissions in the conductors in the PCB multi-layer circuit board. When it is necessary to increase its frequency in order to increase its transmission rate, the circuit itself will cause impedance due to factors such as etching, laminate thickness, and wire width. It is worth changing to distort the signal and cause the performance of the circuit board to decrease. Therefore, it is necessary to control the impedance value within a certain range.