A New Way To Create Structures

Quickly fan out the most complex of component interfaces with reusable blocks of routing.


Let’s focus today on an established routing technology with a new twist! All of you are doubtless familiar with the concept of structures – formerly called via structures, renamed to structures because of their growing flexibility and application across many flows. These handy, reusable blocks of routing allow you to quickly fan out the most complex of component interfaces. And, after that, saving the structure to the library will save you more time with every similar substrate you design. Time not spent developing structures and building escape routing is time you can devote to the unique aspects of each design you work on.

A familiar interface

The UI for creating structures today, whether they be high-speed and L Comp structures with the SiP Layout option license or standard structures in the base tool suite, is shown below:

Here, for the high-speed and standard structures, you will first route out a single pin from the component in question. Then, you’ll come into this command and select that routing (and any surrounding reference elements such as return path vias) to form into a new structure definition.

As soon as you’ve accomplished this, moving to the place structure command allows for placement of the structures to escape out many pins in seconds. Or, if you have already started with a simple via escape pattern, maybe you will opt for the replace via with structure command and swap the placeholder vias for the final structure fanout.

These are invaluable tools in a world where fanout reaches new levels of complexity every year. They do require that you perform some tasks ahead of time. What does one do if one wants a structure that is defined based on specific values and for a specific purpose? Is there anything available in the tool to make this quicker?

A new way to create structures

In Allegro Package Designer, under the ‘Route – Unsupported Prototypes’ menu, you will find the ‘Create Structure…’ command when you have the ‘SiP Layout’ option active.

Upon launching, this new tool provides you with access to create structures parametrically for multiple uses including serpentines, combs, single-ended structures, or diff pair structures with return path vias.

To allow you to work more efficiently, you might want to dock this form with the options and visibility tabs, or you can move it to another screen in a dual-monitor setup. The noticeable difference between the standard structure definition flow here is that you do NOT need to route things first in order to use your example to derive the definition.

Select via padstacks, pad entry/exit patterns, return path via layouts, and the layers on which you need voids to help with signal integrity shielding above and below the vias. As you continue to refine the definition, helpful pictures will guide you by showing the exact relationship between parameters. Various patterns available to choose from:

Pad Entry/Exit Trace Patterns

Return Path Via Patterns

When you have completed parameterizing your structure and naming it, just one press of a button will commit changes and move you straight to placing it into the design!

Have you used these new structures?

If you have, we’d be honored to hear your thoughts. Do you have different entry, exit, or return path setups that you want to see in the pull-down? Perhaps a dynamic preview on the form would speed you to final success by catching errors in the form fields sooner? Whatever it is, be sure to let us know so we can evolve the tool along with you to continue to meet your most demanding requirements. The IC package design space is fortunate to have many interesting, sometimes unique, challenges. Cadence is here to help you overcome each and every one of those!

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