Propagation Delay - ICD Stackup Planner

Example using ICD Stackup Planner to find Propagation Delay (Tpd).

Tpd is Transition Propagation Delay.  

And velocity is the reciprocal of Tpd. 

If Tpd = 139pS/inch then velocity = 1/139 = 0.00719 inches per pSec.
If Tpd = 170pS/inch then velocity = 1/170 = 0.00588 inches per pSec.

Rule of thumb: Typical FR4 material 6mils of trace is ~ 1 pSec.

Here is a 6 layer stackup designed by a popular fabricator which includes Tpd data.

click on images to view

Many fabricators do not include Tpd data in the stackup. 

Using ICD's Stackup Planner you can easily calculate Tpd.

Import or create your stackup in ICD's Stackup Planner.

Then on the main menu select Signal Flight Time

As shown below enter 1 inch for each signal layer.















The signal Propagation Delay (Tpd) in pSec/inch for each layer will be displayed in the Flight Time column.


That's It !