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54 The PCB Design Magazine • June 2015 Figure 6 and areas subject to bending are high- lighted, which can assist in planning for com- ponent placement regions known as "rooms" later on. This sheet metal model can be exported to the PCB design software (ECAD) as either IDF or DXF in its simplest form. The PCB editor im- ports this board shape or outline from which the PCB shape is actually created. Components are placed in the PCB editor and then an IDF file is generated to transmit the PCB shape and component locations back to the MCAD database, where the mechanical designer can re-fold the board substrate. However in most cases this is an unwieldy task, with some manual effort involved in maintaining the placement as - sociations of the components on the rigid board sections in their folded positions. The overall process involving both MCAD and ECAD domains is illustrated in Figure 7. The advantage of this method is that both me- chanical and PCB design specialists get to work in their native software environments, focusing on what they do best. Direct ECAD 3D Model As the name suggests, in this new method the PCB layout design, rigid-flex folding design, and mechanical assembly are all modeled to- gether directly within the ECAD software. Ad- vancements in most modern PCB design tools enable proper 3D visualization at a minimum, supported largely by the use of 3D STEP models of the components and mechanical enclosure or parts thereof. ECAD software with 3D functionality is not intended to replace dedicated mechanical CAD systems. At least, not until engineering affords such a multi-disciplinary approach. Meanwhile, it is a major step forward in terms of improved workflow, and reduced waste of time and mate- rials. High-end PCB design tools allow for Native 3D PCB design: this includes not only 3D visual- ization of the PCBA, but also full 3D modeling of the PCB including dielectrics and copper. Such 3D models can also be exported for thorough thermal and electromagnetic investigations. With additional tools for native 3D model- ing of the board materials, components, and mechanical object such as the enclosure, proper clearance checking and animation of flexible circuit elements is possible, offering some guar- antee that the final rigid-flex design will fit in the designed enclosure and function according to specifications. It is still beneficial for the MCAD designer to generate a 3D model of the rigid-flex board without components, and import this as a 2D outline into the ECAD software. The overall ex- tents of the PCB are generated from this. Alter- natively, this step is performed directly within the PCB design tool. Once the PCB outline has been generated, the layer stacks for each region of the PCB de- article RIGID-FLEx PCB RIGHT THE FIRST TIME – WITHOuT PAPER DOLLS continues Figure 5: stepper motor model and rigid-flex. Figure 6: here's the flattened 2D sheet metal shape to be exported to ECAD.