When to remove via stubs and non-functional pads?

New Blog: When to Remove Via Stubs & Non-functional Pads? Can a design still work....by Zhen Mu - #pcbdesign #eda

The actual consideration here should be the channel budget. An interface specification usually requires the insertion loss (in dB) of an entire channel within a pre-defined margin at or below certain frequency points. This is the allowed noise budget of the channel. (Note that the important concept here is not data rates in time domain, but frequencies in frequency domain.) As an interconnect component of a channel, via response generates noise, therefore, consumes the budget. If an existing channel carrying the signals with certain data rates has the overall loss within the required margin, the design will work and it is likely that a designer does not need to modify via designs, such as removing NFPs and stubs of vias. This is an important aspect for designers to understand: vias on a channel may have bad behavior but the effects may be out of the range that channel budg...

Full article: http://www.mentor.com/products/pcb-system-design/blog/pos...