Factors affecting the resistance of FPC soft board impedance control circuits

Everyone in Xuedi Anu knows the FPC soft board impedance control circuit, so what is its function? We also call the FPC soft board impedance control circuit an impedance strip. The principle of impedance control is that when the current that needs to pass through the line is greater than the line can When it reaches the maximum value, it is necessary to use impedance to control the excess current. So how to control the value of the impedance line? The following five aspects will affect the resistance of the impedance line.

1. Different substrate materials lead to different impedance values.

The difference in base material has a great impact 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 like there are no two identical leaves in the world. kind of truth. The impedance lines on the impedance board generally use base materials with good material stability. If materials with poor stability are used, the material resistance will change greatly. Once the required impedance value is exceeded, the impedance line cannot be used. control lines.

2. Impedance changes due to different material thicknesses

This reason has many similarities with the reasons for the above materials.

3. Line width and spacing

The difference in line width and spacing between impedance lines will cause changes in resistance. Impedance lines are used as resistors, so the width of the line is the resistance value. What does it have to do with absorbing the spacing between lines? The current passing between the lines will generate a magnetic field, and the magnetic field can also generate current (generator principle, which is why shielding is required). At this time, the current will change, which indirectly causes the impedance control data to be inconsistent. precise.

4. Etching tolerances can cause impedance changes

Etching is a kind of corrosion to the circuit, which will affect the thickness and width of the circuit, so we go back to the content mentioned above. Etching can only be maintained within a range, and there are still deviations. These deviations are the cause of resistance changes.

5. Electroplated copper tolerances

The impact of this depends on the process flow. In some processes, electroplating occurs before the moment, so it will not affect the impedance at this time. However, when most FPC soft boards are produced, the etched circuits have been completed during electroplating. At this time, copper will also be attached to the impedance circuits, resulting in changes in the resistance of the impedance circuits. The above is the knowledge about FPC soft board impedance control circuit. I hope everyone can discuss and exchange it together.