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Which factor will affect the impedance value for the PCB fabrication?

Date:2019-05-28 00:00:00

Which factor will affect the impedance value for the PCB fabrication?


Key worlds: PCB impedance controlling, related factor to the impedance, impedance type in PCB, single end trace impedance, differential pairs impedance, coplanar


In the current PCB design, engineers usually need the impedance control for the chips, in the industry, it includes 3 types impedance : single end impedance (usually 45 ohm or 50 ohm), differential pairs impedance(usually 90 ohm or 100 ohm) , coplanar(usually 50 ohm or 90/100 ohm)
So which factor will affect the impedance value in the PCB fabrication?

Per the formula and experience, below factors will affect the impedance:

1) Dielectric thickness (The important and main factor)

2)Dielectric Er

3)Impedance trace width, trace spacing(for differential pairs)

4)Finished copper on the trace

5)Soldermask thickness and Er


Do you know which items is the main and biggest factor to affect the impedance?
It is the Dielectric thickness, it will affect the impedance with big value change, so when you design the layer stackup,
please consider the dielectric thickness firstly.

The second factor is Er, it is the fixing factor because it is the material physical characteristics, you can not do
anything  on it, unless you change the material.

the next is the trace width/spacing, it is also the big factor to the impedance, when we check the gerber,
we will use the POLAR9000 to calculate it for you, once impedance don't match your target , we will release
the technical questions to you.

For above points, we have knew the factors to impedance well, when we manufacture the PCB in the process,
we will strictly to follow the points to control. Further, we will make the coupons to measure if the actual value can
meet customers requirement or not.

If you have impedance PCB need to manufacture, please send email to sales02@kingtontech.com

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