What is the impedance of the board?

Simply put: an impedance board is a board impedance control that requires impedance control. It refers to the reference layer of the circuit layer under high frequency signals. The “resistance” generated by the transmitted signal must be controlled within the rated range to ensure that the signal is not distorted during transmission. In fact, board impedance control is such that each part of the system has the same impedance value, ie impedance matching.
From the perspective of PCB manufacturing, the main factors and key factors affecting impedance are:
Width/line width increases impedance and distance increases impedance.
The H - impedance increases as the thickness of the insulation increases.
The thickness of T - copper decreases as the thickness of copper increases.
The impedance decreases as the thickness of the H1-green oil increases.
The Er dielectric constant reference layer DK value increases and the impedance decreases.
As the tool undercut increases - W1 - Wundercut, the impedance increases.
Note: In fact, the soldering resistance also affects the board's impedance, but because the solder resistive layer is attached to the dielectric, the dielectric constant increases, which is due to the dielectric constant, which reduces the impedance by about 4%.