PCB Tech - What factors are related to the impedance of the circuit board

What factors are related to the impedance of the circuit board

In short: the impedance circuit board refers to the circuit board that needs impedance control. Impedance control means that under a high-frequency signal, the "resistance" of a certain circuit layer to its reference layer 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/line width between lines increases and the impedance decreases, and the distance increases the impedance increases;

H-Insulation thickness increases and impedance increases;

T-The copper thickness increases and the impedance decreases;

H1-The thickness of green oil increases and the impedance decreases;

Er-The DK value of the dielectric constant reference layer increases, and the impedance decreases;

Undercut-W1-Wundercut increases, and the impedance becomes larger.

Note: In fact, solder mask also has an impact on the impedance of the circuit board, but because the solder mask is attached to the dielectric, the dielectric constant increases. This is attributed to the influence of the dielectric constant, and the impedance value will be reduced by approximately 4%.

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