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76 The PCB Magazine • June 2015 this solution: The valence of the front spoiler lip is mechanically digitized and recreated in a 3D MCAD model. The surface is then lifted and flat- tened into a mechanical piece and translated to the ECAD environment to layout the flexible cir- cuit. The flexible circuit is then designed to con- form to the exact contour of this irregular shape. Sensors running along the flex circuit solve this challenge of limited space with the added ben- efit of reducing the weight. We are in a time of amazing developments in our electronics products. Today's electronics are increasingly smaller, faster, lower power, lighter weight and feature rich. Flexible circuits are com- monly used to replace wire bundles to reduce size, weight and power (SWaP). It is also common to use a flexible circuit when space is confined and circuitry is needed to be folded around corners and into tighter packaging. When traditional solutions no longer meet design constraints, the flex-to-fit model allows us an alternative path forward. As we step back and look at the exist - ing structures available with a creative eye, it can be both exciting and a bit daunting. Imagination and analytics often compete and the combina- tion of both is needed to determine how a space can be best utilized. Extruding the surface of irregular shapes and creating a perfectly fit flexible circuit to integrate into the contour of that structure opens up so many possibilities. Creative thinking can save space, weight, cost and promote ease of assem - bly. The applications for this approach are end- less. For any product in the automotive, aero- space, military and commercial sectors, where restricted weight and space are major factors, flex-to-fit offers excellent solutions. Imagine another example: If you were to ex- trude the internal surface structure of a wing or fuselage of a drone or autonomous vehicle, the flex circuit could be modeled to fit the exact con- tour of the area it is to occupy. The cavity that would otherwise be consumed by bulky wiring cables could be made free to accommodate more features, whether it be additional sensors, moni- toring or enhanced functionality. One last example is a product that is hot in to- day's market—wearable electronics. Rather than run a bunch of wires and all of the sensors in a shirt, which can be a bit bulky, one possibility is to sew in flex circuits that have been modeled or molded around the human body. The flex can be sewn between the layers of material resulting in a smoother surface more closely resembling regular clothing. While talking with Mike, it was easy to see the possibilities and the benefits to the end prod - uct. It is also important to discuss the benefits of this process to the flexible circuit design itself. By extracting the exact contour of the part, flatten- ing it, and transferring this to the ECAD design tools, the designer is able to accurately analyze the flexible circuit design in the ECAD model. Of- ten when using a flexible circuit in an unusually shaped area, the added length required and bend areas are difficult to determine. This approach al- lows the designer to perfectly fit the flex to the structure it will be aligned with. The designer is also able to accurately analyze the proper bend radius and make adjustments to remove copper layers or adhesive layers to meet standard design rules. Stiffeners and cut-out areas are also able to be analyzed directly in the ECAD system. Be - cause all of these items can be reviewed to the exact fit of the piece, the end result is a more accurate design. There will be no surprises as the piece is assembled in the unit, which can poten- tially reduce the number of revisions during the design cycle. To identify a structure that is not being uti- lized, digitally scribe that structure to create a MCAD model, flatten the surface of that model, and transfer that to the ECAD system for flex circuit design; this clearly demonstrates the convergence of the mechanical world with the electrical world. The convergence of these two disciplines brings so many new opportunities for today's electronics. Applications for the flex-to- fit concept are really only limited by our creativ - ity and imagination. It is an exciting time to be involved in the world of flexible circuit design and manufacturing. PCB Tara Dunn is the president of Omni Pcb. THE FLEx-TO-FIT APPROACH continues Flex tAlk

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