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For most IC package designers, the GDSII format is a part of daily life. You may receive stream data from your IC designers or partners which you must convert into die components for placement on a package substrate, or perhaps you export stream data as part of your manufacturing and documentation process.
Whatever the case, GDSII is a widely-used standard format for data exchange. Cadence has taken its stream interface to the next level with the introduction of the 16.6 release of its IC package layout tools, Allegro Package Designer (APD) and SiP Layout.
With the new tools for interactively creating layer conversion/mapping files, advanced export controls for merging overlapping metal on the same layer, and for configuring the number of segments in vectorized arcs, exporting stream is more powerful than ever. And when importing stream, tools to correct self-intersecting shape boundaries and to convert bare GDSII geometry data into die components make reconstruction of intelligent package substrates a simple matter.
To learn more about all these improvements and to see how they will improve your performance and your communication with colleagues and partners alike, read on!
Enhancements to the Stream Export Interface
Stream out allows you to generate manufacturing data as well as communicate with other designers who may be designing parts included in your package substrate or on which your finished package will be placed.
Shown in the picture below -- highlighted in red -- are two important new controls for how the geometries are exported to layers.
With the first, "Vectorized segments per circle," you can fine-tune the number of straight line segments used to approximate arcs in the resulting GDSII data. When you need a closer approximation of a true circle than the standard 32 segments provides, increase this value up to a maximum of 360 segments.
With the second control, "Merge overlapping polygons prior to export," the tool will combine overlapping polygons to create a single polygon. This option is only available when you are flattening geometry, as it will combine pins, vias, clines, shapes, and other objects to create a single outline.
Some tools, such as IC design tools, do not handle polygons that overlap on the same layer well. By using this option, the stream data you provide to your partners can be more easily processed. This saves time and, in some cases, the use of an intermediate tool to perform this merge operation.
Also shown in the above image, highlighted in blue, is the access to a new UI tool for creating and manipulating your layer conversion files. Pressing the edit button will bring up a secondary form, shown below. With this form, you can interactively manage your conversion files while letting the tool itself ensure the format of the file is correct.
Use class and subclass filters to quickly map multiple subclasses to stream layer and data type combinations. If you're leveraging the new ability to merge metal, for example, you may map all SOLDERMASK_TOP subclasses to the same stream layer, which will create a simplified layer representing all your soldermask openings for the top side of the substrate.
With the addition of this new user interface, even the conversion file format itself has been enhanced. It now supports subclass names with spaces in them. No longer will you need to replace spaces with underscores or some other character in order to include that layer in your stream output (or to import to that layer when importing stream data).
Enhancements to the Stream Import Interface
While the stream out command allows you to communicate your package design details with others, the stream in tool is used to bring data you receive from people into your current (or a new) package substrate design.
The stream in interface inherits some of the improvements from the stream out tool, most notably the support for the layer conversion file to have layer names with spaces in them. It also incorporates a key improvement for shape import. Since the GDSII format itself has no support for holes/voids in polygons, some tools try to work around this by creating a complex shape outline that intersects with itself to simulate a hole. In other cases, it may combine two shapes into one that touch but do not overlap (such as the two triangular "halves" of an hourglass shape).
With 16.6, when these types of polygon outlines are detected, the tool will automatically attempt to resolve the outline into one or more valid shapes -- with voids, where appropriate -- instead of converting the outline into a simple line representing the boundary exactly as specified in the stream data. This allows you to omit any steps involving using the compose shape and other tools to turn the complex outline into shapes. And, in cases where the tool cannot resolve the outline into valid shapes, the outline will still be imported into the design for manual manipulation (with a notice of this in the log file so you know just where any shapes needing reconstruction work are).
On top of these enhancements to the stream import tool is an entirely new command. It is needed because, In many cases, the stream data you get represents a die component: pins, outline, and even net names and pin names. Converting this raw geometry information into an intelligent die component was a cumbersome, difficult process in the past. You would need to import the data into a DRA file, manipulate the pad shape data into padstacks and therefore pins, and finally create a symbol which can be placed into the package design.
With 16.6, you can use the "compose die from geometry" command to automate the process of converting the GDSII data directly into a placed component in your package substrate design. The UI for this command is shown below. With one command, you can go from raw geometry data into a fully-defined die component, complete with net assignments, placed in the proper orientation for wire bonding or flip-chip mounting onto the package substrate.
Upgrade to 16.6 APD or SiP Layout today and start leveraging these enhancements and the many other improvements to the tools to increase your productivity and improve your communications with your colleagues, vendors, and partners.
Have a comment or suggestion for making the GDSII interface tool even better? Contact your Cadence support representative today. We'd love to hear from you!
To use the" Merge Overlapping Polygons prior to export" feature please go to:
User Preferences > Early Adopter > _stream_out_merge_polygons (select)
You will need to close and restart Allegro for this feature to take effect.
Now when you open the Stream Out tool and you will see the desired selections.
the Stream Out GUI shows an option 'Flatten Geometry > Merge Overlapping Polygons prior to export' , but I do not see that in my installed 16.6 stream out GUI, neither is it mentioned in the 'whats new in 16.6 SiP' documentation. How do we get that option to show up in the GUI ??