Virtuoso Meets Maxwell: Defining Standard Library Components

'Virtuoso Meets Maxwell' is a blog series aimed at exploring the capabilities and potential of Virtuoso RF Solution and Virtuoso MultiTech. So, how does Virtuoso meets Maxwell? Now, the Virtuoso platform supports RF designs, and the RF designers measure the physical and radiation effects by using the Maxwell's equations. In addition to providing insights into the useful software enhancements, this series broadcasts the voices of different bloggers and experts about their knowledge and experience of various tools in the Virtuoso IC-Packaging world along with the nuances of RF, microwave, and high frequency designs. Watch out for our posts on Mondays.

After discussing the library import process in the last blog, it’s time for a closer look at standard library parts in the Allegro platform. Within a typical package design flow, components are added from die text files, for example, Ball Grid Array (BGA) might come from a ball map spreadsheet or BGA text file, while JEDEC standard parts may be rapidly built directly with the BGA generator. All these standard components might be imported into your OpenAccess library of parts from the package database allowing you to retain all existing parts with ease while also bringing in new parts for your next design start. The Allegro Package Designer Plus product line offers everything needed to take an IC package from an idea to a manufactured part, and this is where the journey takes us today.

The Allegro Package Designer Plus is available from your Virtuoso environment through Virtuoso MultiTech Framework. Let's take a look at some of the standard library parts.

Die and BGA Text Files

These delimited files use a simple, but highly flexible, format. All your IC team needs provide are the physical pin numbers and XY locations of all pins plus the overall body size of the chip. The more information shared, the better off you are.

Turning text files into fully modeled parts is done from either the Add – Standard Die or Add – Standard Package wizard. The wizards function similarly and after browsing to the source text file, you will see the screen below:

Column order is flexible. My die component has physical pin numbers, logical pin names, net names, and XY coordinates. A hint: ask your IC designer to include the column header row at the top of the file, so that the contents of each column is pre-configured for you when reading things.

Because the most common source of these files is from the IC design, XY coordinates are assumed to be in a chip-up orientation for the definition of the die. For a flip-chip, coordinates will be mirrored through the X-axis during placement. It is important that you not attempt to pre-flip the pin coordinates to ensure proper definition of the symbol!

There is no padstack column in the above-mentioned die. The IC designer will not normally know what size and shape of landing pad should be used in the package or even what the pillar/bump looks like. Knowing this, you can assign or define custom padstacks for your pins directly in the wizard.

Finally, you define the placement of the part instance and its attachment type:

This information may be modified later, but values are needed so the part can be placed onto the substrate layout. Perhaps the most important fields here are found under the advanced options. If optical shrink or scribes have not already been applied to the source text file, you want to set these up here, as they affect the very basic properties of the physical part. This information can be provided in the header section of the text file. If you don’t find it there, be sure to ask the IC design team for any values you need to apply.

BGA Ball Map Spreadsheets

Ball maps have been in use for a long time, just like text files. Their main advantage is that the grid (depicted below) lets you see, even in something like a spreadsheet, what the pattern of pins and assignments is.

You can see pin numbers, nets, even colors assigned to nets that allow you to visually group together things like bus nets or differential pairs. This is one thing that a die text file, with its simple, compact format, is unable to offer.

Most imports of ball maps are done for ECO updates, not for initial part definitions. An initial definition is possible, though! What you will need to do first is create the empty BGA “container” to add the pattern of pins. Do this through the symbol edit application mode and specify the size, pad layer, and other data points not published in the spreadsheet’s cell contents. Once complete, a right mouse button pick of the Add Pin option will let you convert the ball map into a pin pattern in a few clicks.

Should your BGA go through revisions (and whose don’t?), you can use the File – Import – Symbol Spreadsheet to quickly update everything from a new ball map provided by your architect or team lead.

BGA Generator and JEDEC Components

Finally, we turn our sights on JEDEC parts. The most common standards defining the size, shape, and base characteristics of BGA components out there, the JEDEC specifications are handled through Allegro Package Designer Plus’s generator tool. As you pick the desired size for your component, the available JEDEC pitch and row/column counts (and more) are filtered to the legal values.

This is designed to ensure that whatever part you define through the wizard will be JEDEC compliant. And since there are thousands of parts that could come out of all the different parameters to the standard, using the wizard removes any need to store huge numbers of parts in your library. Generate the part when and where you need it. Why maintain something that you can generate in 20 seconds?

Being a wizard, the command will walk you through all the information it needs to create your part. From the reference designator and part name to the size and matrix of pins, over the course of five simple steps you’ll provide everything. A quick preview confirming the part properties and you’re done!

Assemble Parts List

Mix and match any of the above to pull together all the components for your next package design. Once the parts are gathered, bring them together into your OpenAccess part library using libImport and get the jump start you need to tape out ahead of schedule!

Tyler Lockman

Related Resources

For more information on Cadence circuit design products and services, visit www.cadence.com.

About Virtuoso Meets Maxwell

Virtuoso Meets Maxwell series includes posts about the next-generation die, package, and board design flow with a focus on reinventing and optimizing the design process to ensure that the designer remains a designer! Keep watching!

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