PCB Impedance Control

PCB Impedance Control is the characteristic impedance of a transmission line formed by PCB conductors. It is relevant when high-frequency signals propagate on the PCB transmission lines. PCB Impedance Control is important for signal integrity: it is the propagation of signals without distortion.


pcb impedance control


The impedance of circuits board is determined by the physical dimensions ( line wide/space ) and materials of the circuit and is measured in Ohms ( Ω).

PCB Impedance Control has been one of the essential concerns and tough problems in high-speed PCB design, As a Impedance Control designer , You should know what affect PCB impedance and  how to calculate impedance :


1. The impedance of a PCB is largely determined by the following parameters:


1)  Distance of signal layer and potential
2)  Conductor geometry
3)  Trackwidth
4)   Copper thickness
5)   Permittivity εr


2. Impedance and Delay Calculation Formula of Transmission Lines on PCB


PCB Impedance calculator


Surface Microstrip pcb impedance control

Formula Restrictions:0.1 < w/h < 3.0

Coated Microstrip pcb impedance control

Formula Restrictions:0.1 < w/h < 3.0


Edge-Coupled Surface Microstrip pcb impedance control

Formula Restrictions:0.1 < w/h < 3.0
Formula Restrictions:0.1 < s/h < 3.0


Edge-Coupled Stripline (symmetrical) pcb impedance control

Formula Restrictions:0.1 < h/w < 3.0
Formula Restrictions:0.1 < s/h < 3.0


There are some free PCB software to provide impedance control calculator ,and some website provide online calculator as reference.


Selecting Foil-built or Core-built PCBs to support Impedance Control


RayMing Technology normally suggest impedance designer to choose Foil-Built PCBs in order make the most economical PCB. That being said, our PCB Assembly is very flexible, and we can use Core-Built PCBs as well. Foil-Built PCBs not only tend to be more economical than Core-Built PCBs, but they are also slightly easier to fabricate . The pictures below explanation the difference between the Foil-Built and Core-Built PCBs.


Foil-built PCB impedance control Core-built PCBs impedance control


Foil-Built PCB board use 1 less core than the Core-Built PCBS in the stack-up. The outside consists of Aluminum Foil. In addition, Foil in different copper weights is much easier to purchase. Since Foil-Built PCBs are made of aluminum, they can be used on any builds, regardless of the primary laminate material being used. PP (Pre-pregs) are also less costly than cores, especially if the core is 5 mil or thinner.


Core-Built PCB board have cores on the outside, so there is no need to use Aluminum Foil. Depending on material availability, at times it may be difficult to acquire a core with uneven copper weights. This forces the PCB manufacturer to etch down the cores, which is costly since a good deal of labor is involved. Except labor, the PCB factory must use a higher copper weight than what appears on the board, increasing material cost as well.


Nowadays PCB designs and components become smaller, faster – in other words, more complicated. PCB Impedance Control is becoming more critical , Rayming have 10 years PCB manufacturing experience , We can provide full support when you are designing a PCB impedance board .


RayMing's Stack-up Capabilities include:


1) Free Stack-up suggestion
2) Free Impedance Calculation
3) Hybrid Build
4) RF, Microwave, and other High Frequency PCB


RayMing Electronics keeps common materials in our in-house inventory at all times. The common materials include:


1) Higher copper weights: 2 oz, 3 oz; Heavy Copper PCBs ( With Lead Time)
2) Odd copper weights: H/1 oz, H/2 oz, 1/2 oz
3) Foil: 1/4 oz, H oz, 1 oz, 2 oz, 3 oz


If you have PCB Impedance design , Pls send PCB files to  sales@raypcb.com to get quote now !