Why printed circuit board need impedance control?
In the transmission signal line of an electronic device, the resistance encountered when the high-frequency signal or electromagnetic wave propagates is called impedance. Why do PCB boards have to be impedance during the manufacturing process of the circuit board factory? Let us analyze from the following 4 reasons:
1. The PCB circuit board of the circuit board factory should consider plugging and installing electronic components, and the later SMT patch connection also needs to consider issues such as conductivity and signal transmission performance, so the lower the impedance, the better.
2. The PCB circuit board undergoes copper sinking, electroplating tin (or chemical plating, thermal spray tin), connector soldering and other processes during the production process. The materials used must require low resistivity to ensure the overall impedance value of the circuit board The normal operation can only be achieved when the product quality requirements are met.
3. The tin plating of pcb circuit boards is the most prone to problems in the production of the whole circuit board, and it is the key link that affects the impedance; its biggest defect is easy oxidation or deliquescence, poor solderability, making the circuit board difficult to solder and excessive impedance. High, resulting in poor conductivity or instability of the overall board performance.
4. The conductors in the PCB circuit board of the circuit board factory will transmit various signals. The circuit itself will change the impedance value due to the etching, stack thickness, wire width and other factors, which will cause the signal to be distorted and lead to the circuit board. Performance drops, so you need to control the impedance value within a certain range
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