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70 DESIGN007 MAGAZINE I MARCH 2021 in a fabrication drawing. It uses the design data to explicitly define the multiple aspects of a rigid-flex design. How? Let's look at how some of the details are sent digitally. First, let's look at stackup and general board structure. In the design tool, the different stackup details are created, with one or more rigid stackup definitions (8-layer vs. 4-layer, etc.) as well as several flex stackup structures (1 or 2 copper layers, etc.). In my design database a boundary is defined and the stackup data is assigned to those boundaries. is data is then placed into the IPC-2581C format contain- ing the links of each stackup to each bound- ary association. ese are known in IPC-2581 terms as stackup groups assigned to stackup zones. A by-product of these connections is the ability to define the outline profile for each copper and dielectric layer, a key tool for the fabricator. ese links within the IPC-2581C data take the guesswork out of calculating the differ- ent boundaries for each stackup definition to stackup zone connection and the edges for each layer. is reduces time spent on calcula- tion and errors in interpretations for the fabri- cator. Other factors related to flex information include details of each bend. e details attached to bend lines and bend areas are also preserved in the IPC-2581C data. e bend line, drawn across the apex of the bend in the CAD tool, area of the flex affected by the bend extents, or bending area, and bend definition (direction, bend type, radius, bend angle) are passed into IPC-2581C. ese details can be leveraged though the manufacturing process into the final assembly. Conclusion Simply put, we now have a better way to get design intent for rigid-flex designs with less reliance on complex drawings and manual documentation. Passing the rigid-flex build Figure 1: Stackup groups assigned to stackup zones and layer profiles are provided in IPC-2581 Revision C.

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