Issue link: https://iconnect007.uberflip.com/i/1073397
16 FLEX007 MAGAZINE I JANUARY 2019 Modeling the rigid-flex PCB assembly in its full context is invaluable. The board shown in Figure 4 is shown mounted in its multi-board assembly context in Figure 6. By modeling the whole multi-board assembly, changes to the length and shapes of flex connectors can quickly be determined. This example is an inertial measurement unit from an autono- mous quad-rotor drone design. The flex cir- cuit was chosen to provide vibration isolation from the main board, which is mechanically mounted to the rotor arms, thereby using the flex circuit for physical low-pass filtering of the inertial measurements. In this assembly, with the enclosure models hidden, everything fits together nicely. How- ever, bringing in the enclosure models from their associated STEP files and running a clear- ance/collision check directly in the PCB design tool immediately shows where the top hous- ing model interferes with the folded flex cir- cuit. Note: STEP stands for "Standard for the Exchange of Product model data," from the ISO- 10303 standard, and is used for the interchange of 3D mechanical models (usually components) between mechanical design software and PCB design software. The collision highlight is shown with a cross-sectional view in Figure 7. Figure 6: Multi-board assembly including rigid-flex. Figure 7: Cross-section of clearance check with enclosures showing flex interference.