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When it comes to IC Package substrates, Gerber is still one of the most common, most popular formats used to send the design for manufacturing. Being a strictly 2D format, however, how do you best fit bond wires into your artwork films if you want to be able to see them?
The same wire profile can connect pins from multiple dies to the substrate, to each other, or can even connect one die pad on the top and another on the bottom to their respecting fingers. Because of this, mapping by profile name does not work well, as is ideal for a typical layer in the cross section. Nor does a grouping that looks at, for instance, the layer that the starting or ending pad is located on. Wires that go between two dies in neighboring die stacks could break this model easily, as could jumper wires between two fingers on the substrate.
What, then, is a poor designer to do in order to get their ideally organized artwork films without creating dozens of duplicate wire profiles with different names based on their relative start and end points? With Cadence's Allegro Package Designer and SiP Layout tools, you can quickly and easily establish manufacturing reference layers that concisely group your bond wires however you want them in your documentation—without compromising your design’s complexity or the flexibility of the 3D wire profile definitions.
Read on to learn just how this is done, and how you can apply this to your GDSII, DXF, and PDF outputs as well!
Depending on your design, you may have a very complex organization of bond wires, which could involve multiple passes of bonding different sets of wires. It could even require that certain wires be added, then more dies stacked, and another pass of wire bonding be performed.
Naturally, the goal is to minimize the number of passes, as this helps reduce the per unit package cost. The Cadence 3D Viewer, with its detailed 3D wire DRC engine, can help you (along with your expert bonding engineer!) find the minimum spacing between bond wires and locations where sequencing is crucial.
Once you have this information, however, it is time to actually define the bond wire groupings. And, as changes are made to the bond shell, whether for an ECO of the die, a new revision of the substrate, or even the design of an alternate design variant, you want to be able to keep these groupings up to date with the design so that you ensure the final design is manufactured accurately.
The command that is designed specifically to help you achieve this is the bond wire doc prep tool. This can be found with the bond finger text labeling tool (Display Pin Text) in the Manufacturing menu, ether in SiP Layout or Allegro Package Designer:
There are two commands here. The first, the actual doc prep tool, allows you to generate the different wire sets. Running it, you will be presented with this user interface:
Here, you can add as many layers as you like. As you can see, you can control what wires go on that layer by wire profile, by the starting layer or die, and/or the ending layer or die. As you tweak the combination of filters for each layer, you will see how many wires map to that layer. And, at the top of the form, you can see how many wires are not yet mapped to any layer. If you want a bond wire to be shown on multiple layers for documentation reasons, you are welcome to do so, as well! Or, if you just want an initial mapping, press the auto-generate button to pre-populate the chart with the different combinations.
Once the mapped layers are defined, you can press the generate button. What happens at this point is that all the bond wires are copied to the appropriate layer(s). The individual layers can be added to your artwork films (which will also allow you to export these to a PDF document), but can also be referenced in your DXF or GDSII conversion files.
From this point on, unless you add new profiles or dies, you should never need to bring this form up again. Instead, you can just run the other menu command, the batch update tool. This will regenerate the contents of all the defined bond wire manufacturing layers based on the exact bond wires setup in the design.
Do you have a different way that you organize your bond wires that isn’t easily defined with the tools shown above? Perhaps you have an idea for other objects and relationships that would benefit from an automatically generated and maintained documentation layer. Whatever the case may be, share your ideas with your Cadence customer support representative. We’re here to help you bring your most difficult and cutting-edge projects to market, just as we are here for all your traditional and volume substrate designs!