Introduction of FPC impedance board

FPC impedance board is also called impedance bar. When the current that needs to pass through the line is greater than the maximum value that the line can bear, we need to use impedance to control the more current. This is the principle of impedance control. So how to control the value of impedance line? Every aspect will affect the resistance of the impedance line

1. Different base materials lead to different impedance values

The difference of the base material has a great influence on the soft board. The resistance value of each material is different, and even if it is the same material, the resistance value of each part will not be exactly the same, just as there are no two leaves of the same kind in the world. Generally, the impedance circuit on the impedance board uses the substrate with good material stability. If the material with poor stability is used, the material resistance value will change greatly. Once it exceeds the required impedance value, the impedance line can not be used to control the circuit.

2. The different thickness of material leads to the change of impedance

This reason has a lot in common with the above material.

3. Line width spacing

The difference of line width spacing between impedance lines will lead to the change of resistance value. Impedance line is used as resistance, so the width of line is the size of resistance value. What's the relationship between the distance between absorbing lines? The current between lines will produce magnetic field, and the magnetic field can also produce current (generator principle, which is the reason for shielding). At this time, the current will change, which indirectly leads to inaccurate impedance control data.

4. Etching tolerance will cause impedance change

Etching is a kind of corrosion to the circuit, which will affect the thickness and width of the circuit, so we have to go back to the content mentioned above. Etching can only be maintained in a range, or there are deviations, these deviations are the reason for the change of resistance.

5. Tolerance of copper plating

The impact of this depends on the process. In some processes, because the electroplating is before the time, the impedance will not be affected at this time. However, most of FPC soft boards have been etched when they are electroplated. At this time, there will be copper attached to the impedance circuit, which will lead to the change of the resistance value of the impedance circuit.