Here’s another Tip from Yan Killy, Technical Marketing Engineer:
It is a common practice to use vias to shielding high noise traces. It involves using multiple vias connected to a ground net around the entire high noise trace.
The designer can use “Add Via” command after selecting Ground Net and add them one by one. Doing this manually is time consuming, especially when the trace has a lot of corners and arcs. At the same time the designer needs to make sure that spacing from trace to via, and from via to via is constant.
To automate this process PADS has a command, in “Options Via Patterns” setup that control all of the parameters I have outlined above. All the designer needs to do is select a trace that needs shielding, and RMB (Right Mouse Button) select ‘Add Via Shield’ and all of the vias will be added around the trace at once. This can be done to a single trace or multiple traces, for example, a differential pair.
For more information on via stiching and via shielding, see the video on SupportNet at http://supportnet.mentor.com/reference/tutorials/index.cfm?product=C115%2DS153%2DG192%2DP10548