WEEqoo

 What is impedance control?

Impedance is the combined effect of resistance and reactance together in an electrical circuit, which is measured in Ohms. Since impedance changes with frequency, it also can be thought of as an AC characteristic. In this context, maintaining a controlled impedance is critical for preserving signal integrity within a PCB design, especially in high-frequency applications.

How to Achieve Impedance Control

Unless specific design measures are applied, a PCB normally doesn't have controlled impedance. Impedance control refers to the process of maintaining impedance variations within acceptable limits by making precise adjustments in circuit layout and manufacturing.

In practice, impedance control is achieved by two key aspects: a well-defined PCB stack-up and properly designed trace configurations. Factors such as trace width, dielectric thickness, and material employed go a long way in deciding impedance.

Why Impedance Control Matters in PCB Design

Every trace on the PCB is a transmission line, carrying signal from a source to a load. In a circuit where the impedance of the source and the load does not match, part of the signal reflects instead of being fully transmitted. This reflection weakens the quality of the signal and may result in performance issues.

For low-frequency or short traces, impedance control may not be critical. However, as the frequency of signals increases or trace length increases, impedance does become a concern. This is why controlled impedance design plays such an important role in today's high-speed and high-density circuit boards.

Impedance Control at Weeqoo

Accurate impedance control demands precision at every step, right from design to fabrication. In most cases, the designer will define a target impedance and tolerance while the PCB manufacturer will choose materials and construct the board to those values.

Our engineering team at Weeqoo ensures your impedance requirements are well-understood before production. Please indicate the target impedance and tolerance within your order so we can confirm stack-up and manufacturing parameters with you in advance.

Most controlled impedance boards are tested for compliance, although the calculation of impedance can be very complicated. If you require any support or want to understand more about impedance control or other particular PCB design techniques, feel free to consult us at Weeqoo.