In short, an impedance circuit board refers to a circuit board that requires impedance control. Impedance control. Refers to a certain line layer under a high-frequency signal and its reference layer; the "resistance" generated by the signal during transmission must be controlled within the rated range to ensure that the signal is not distorted during transmission. Circuit board impedance control is actually to make every part of the system have the same impedance value, that is, impedance matching.
From the perspective of PCB circuit board manufacturing, the main factors affecting impedance and key factors are:
w——The line width/inter-line increases and the impedance decreases, and the distance increases and the impedance increases;
H——The thickness of the insulation increases and the impedance increases;
T——copper thick copper thickness increases and the impedance becomes smaller;
H1—green oil thickness increases and the impedance becomes smaller;
Er——The DK value of the dielectric constant reference layer increases, and the impedance decreases; Undercut——W1-Wundercut increases, and the impedance increases.
Note. In fact, the solder mask also affects the impedance of the circuit board, but because the solder mask layer is attached to the medium, the dielectric constant increases. This is attributed to the influence of the dielectric constant, and the impedance value will be reduced by about 4%.
