BoardSurfers - Aerials and Bails: How to Split a Viastack

Today’s compact and powerful devices require small and high-density PCBs. Tight routing around densely packed components is thus indispensable, but cannot be achieved using conventional blind-buried and through-hole vias. Consequently, stacked vias have become an essential element of contemporary PCB designs. Stacked vias can be used in place of through-hole vias by placing multiple vias exactly over each other, taking less space, and ensuring reduced parasitic capacitance. 

It is often not easy to edit stacked vias since the vias are placed at the same location and handled as a single entity. You may want to move a single via without touching the entire stack and may be wondering how to do it. Or you wish to copy a via from the stack to reuse it in a design. However, it is no big deal doing this using Cadence Allegro platform tools.

Modifying Via Stack

To split a via stack during slide operation, a context-sensitive command Split Stack is available. In the Etch Edit application mode, set the Find filter to Vias and select a via stack. From the right-click menu options, choose the slide command. Then, right-click to choose Split Stack. It opens the Select Via of Stack form where you can choose a via or a via stack. The selected via/via stack will be separated from the master stack, which you can now slide independently.

The splitting of the viastack is also possible with the copy, move, and delete commands. You can disassociate a via from the stack and paste, move, or remove it from the design.

Splitting Via Stack in a Single Command

In a multi-layer board, where you have stacked vias that span across several layers of the design, splitting a stacked via calls for running the Split Stack command recurrently. Setting an environment variable can save this effort, and you can split the via stack in one go. In the command window, enter the following:

set stacked_via_multi_split

The Split Stack command starts showing additional buttons, All Above and All Below, in the Select Via of Stack form. Depending on the button chosen, the selected via and the vias above or below it are split.

Keep checking this page for more blogs on vias.