Impedance control in PCB: You know, there are all kinds of signal transmission in the conductor of PCB. In order to improving its transmission speed, we have to increase its frequency. However, with the effect of these factors, such as etching, stack up thickness, line width and so on, the impedance value is changed and signal lacks distortion. Thus, the impedance value of conductor in the high speed PCB should be controlled in a certain range, which is called impedance control.

The factors that influences the impedance control: Line width and line distance, copper thickness, stack up order, dielectric constant, dielectric thickness, etc.