Test point for 100 MHz digital signal ?

[gsensor]

Hello everyone,

I'm new to PCB design. I'm currently designing my first 2-layer board. I have digital output signals having a frequency ranging from 50 to 100 MHz that I would like to probe. What is the best test point strategy to not loose the shape of my signal ?
Are surface mount test point good for that ? (for example: https://www.keyelco.com/products/prod43.asp?SubCategoryID=113)
Is it better to use a via without solder mask on it and solder a wire to probe on it ?

Thanks a lot for your help !

 

[kubeek]

If you need precision in the signals, I would use a 50ohm resistor and a U.FL connector (like on a notebook wifi card) like this one https://cz.farnell.com/hrs-hirose/u-fl-r-smt-1-10/receptacle-smt-u-fl-50ohm/dp/1688077
Then just make a few pigtail cables and straight into a scope with 50ohm termination.

 

[crutschow]

If you need precision in the signals, I would use a 50ohm resistor and a U.FL connector (like on a notebook wifi card) like this one https://cz.farnell.com/hrs-hirose/u-fl-r-smt-1-10/receptacle-smt-u-fl-50ohm/dp/1688077
Then just make a few pigtail cables and straight into a scope with 50ohm termination.

That will only work if the signal source can drive a 50 ohm load and most digital ICs can't.

Using a surface mount test point as the OP's reference shows should be fine. You need two test points, with the first directly on the trace with the signal (no significant trace length to the test point, and the other to the ground plane (I trust you have a ground plane on the board). If you can probe the signal with a good 10X oscilloscope probe with a short (as possible) probe ground connection to the ground plane, then the signal integrity should be well maintained.