Product Details

Impedance control in PCB refers to the need to control the impedance of the traces on the circuit board. Impedance control is the practice of maintaining the "resistance" encountered by a signal as it is transmitted between a particular layer and its reference layer within the circuit board, within a specified range, to ensure distortion-free signal transmission. Essentially, impedance control aims to achieve impedance matching, where every component in the system has the same impedance value.

 

Because high-speed digital signals and high-frequency analog signals are very sensitive to variations in impedance throughout the signal route, PCBs require impedance management. Impedance is a circuit's resistance to alternating current flow, and changes in impedance can cause signal reflection, distortion, and attenuation. These consequences can include signal deterioration, data loss, and lower system performance.

 

PCB designers must carefully regulate impedance along the signal route to ensure signal integrity and dependable transmission. This includes calculating and maintaining transmission line characteristic impedance, guaranteeing consistent dielectric material qualities, managing trace width and spacing, and minimizing signal path length and vias. To minimize noise and interference, impedance regulating also entails selecting acceptable termination methods and creating proper grounding and power planes. Overall, impedance management is critical for designing high-speed, high-frequency, and high-performance PCBs.

 

The main factors in PCB factory that affect impedance are as follows:

Trace width (w): Increasing the width reduces the impedance.

Trace spacing (s): Increasing the spacing increases the impedance.

Copper thickness (t): Increasing the thickness reduces the impedance.

Dielectric thickness (h): The greater the thickness, the higher the impedance.

Dielectric constant (Dk): A higher dielectric constant leads to lower impedance.

Note: Solder mask also affects impedance during produce process, but since it is applied on the dielectric, it increases the dielectric constant. This effect is attributed to the influence of the dielectric constant, resulting in a decrease in impedance by approximately 4%.

 

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