Understanding PCB Impedance control When Doing Layer Stack up

Impedance control PCB

Impedance control PCB


PCB Impedance control  helps us ensure that signals are not degraded as they route around a PCB In high frequency applications.

Four matters to be paid attention to when calculating Impedance control by stackup in PCB Design


In the high-speed PCB design process, the stack design and impedance calculation are the first step to the top. Impedance calculation method is very mature, the calculation of different software is not different. Some "trade-offs" between impedance calculation and process are relatively cumbersome. The main purpose is to achieve our impedance control purposes, but also to ensure processing convenience, and to minimize processing costs.


Below we summarize some of the considerations for impedance calculating when design PCB layer stack up to help you improve your computational efficiency.


  1. Line width is rather wide, not fine.


Because there is a thin limit in the process, there is no limit to the width, so if you hit the limit later in order to adjust the line width for impedance tuning, it would be troublesome, either to increase the cost or to relax the impedance control. So the relative width of the calculation means that the target impedance is slightly lower, for example, the single-line impedance is 50ohm. we can calculate to 49ohm, and try not to calculate to 51ohm.


impedance calculator



  1. The whole presents a trend


The whole presents a trend. We may have multiple impedance control objectives in our design, so the whole is too large or small, so do not appear similar to the 100ohm too big, the 90ohm is too small to be large and small.


  1. Consider the residual copper rate and the amount of glue