differential trace impedance calculation

Hello!

I am confused about the correct PCB stack-up for 100 Ohm differential trace impedance.
Can you describe me the basic rules for this and advise relevant links?

For example, I have differential stripline signals, which should be 100 Ohm impedance.
Dielectric thickness may vary, but at the moment I have 4mils.
Trace thickness is 0.6mils.

So I need to choose the correct trace width/spacing, am I right?
Previously I was used 5mils width and 6mils spacing differential traces.
But when I put all these values to some calculator it gives me only 72 Ohm of differential impedance.
What could be wrong and what should I change in my values in order to have about 100 Ohm impedance?
Should I trust to such kind of calculators?

Thank you in advance!

Veronika

It depends on
trace width
trace thickness
trace to trace spacing
dielectric constant of the material
dielectric height from the signal to reference plane

use

https://www.saturnpcb.com/pcb_toolkit.htm

https://www.hughescircuits.com/index.php/en/support/impedance-calculator

How many layers is the board, and what is the allowable tolerance on the impedance figure as a percentage.

marce said:

How many layers is the board, and what is the allowable tolerance on the impedance figure as a percentage.

Click to expand...

The PCB will have 16 Layer in total.

About the tolerance I have read only this requirements:
"The data signal traces should be designed for controlled impedance. Single ended signals are 50 Ohm and LVDS signals are 100 Ohm differential."

Usually 10-20% depending on interface, to get 10% or lower you have to involve your PCb manufacturer