Juding circuit PCB circuit board manufacturers, why PCB boards need to do impedance

2019-09-29 18:41:35

PCB board impedance refers to the resistance and reactance parameters that block AC power.

The reasons are as follows:

1: When installing electronic components, consider using PCB lines (bottom of the board). After insertion, please consider the conductivity and signal transmission performance, so the lower the impedance, the smaller the resistivity should be, preferably less than 10-5 per square centimeter.

2: PCB circuit board in the production process through the process of sinking copper, electroplating tin (or electroless plating or thermal spraying tin), soldering of connectors, etc., and the materials used in these links must ensure the resistivity of the bottom. In order to ensure that the overall impedance of the board is low, it can meet the product quality requirements and can work normally.

3: Tin plating of PCB boards is the most prone problem in the entire circuit board production, and is the key link affecting the impedance. The biggest drawback of the electroless tin plating layer is that it is easily discolored (easy to oxidize or deliquesce) and has poor brazability, which may cause the board to be difficult to solder and the impedance to be too large. High, resulting in poor conductivity or unstable performance of the entire board.

4: There are various signal transmissions in the conductors of the PCB board. As the transmission rate increases, the frequency must increase. If the line itself differs due to etching, laminate thickness, wire width, etc., the impedance value will change. Signal distortion causes board performance to degrade, so it is necessary to control the impedance value within a certain range.

The above impedance is expected to help friends in all areas of PCB board!

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