Design for Test Questions : Probing a Test point

What are the pros and cons between probing directly at a via and probing a dedicated test pin?
How does the design for testability need to change as signal frequencies are in the higher ranges (> 100Mhz)? (ie: Probe types, reduction of overshoot, ringing, etc...)

Thank you for any advise!
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wrote:

Vias can be pretty small. Test pads can be sized for the test equipment.

Generally, one doesn't test high frequency signals directly. Either test indirectly or measure device parametrics.

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