Flex-to-Fit, Flexible Circuits Solve Space Constraints

The “Flex-to-Fit” concept reminds us that creativity and engineering go hand-in-hand.  Click HERE for the video recording of our Fit-to-Flex discussion.

Imagine this scenario: As an engineer, you have been tasked with the challenge of adding sensors to the front spoiler lip of the new 2015 Porsche Cayman. There is limited space available and the cavity is thin enough that running even a small wire bundle would be difficult.

What do you do? Let’s take a look at the Flex-to Fit concept.

When there is not ample space for a conventional approach, this process, which is the convergence of the mechanical world and the electronics world, results in the ability to design a flexible circuit along the contour of an existing, irregularly shaped structure. By taking the mechanical part, extruding the surface and then conforming to that surface, a flex circuit can be created that will fit perfectly within the confines of a limited space or cavity. After talking with Mike Brown of Interconnect Design Solutions, he helped to clarify this process, discussed several exciting applications and explained the benefits to the flexible circuit design process.

Most electronic systems require an enclosure to support a rigid printed circuit board. Looking beyond the constraints of an enclosure and incorporating flexible circuits within the contours of other existing structures, opens up endless possibilities. In the example above, imagine 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 flattened into a mechanical piece and translated to the ECAD environment to layout the flexible circuit.   The flexible circuit is then designed to conform to the exact contour of this irregular shape.   Sensors running along the flex circuit solve this challenge of limited space with the added benefit 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 commonly 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 existing structures available with a creative eye, it can be both exciting and a bit daunting. Imagination and analytics often compete and the combination 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. Thinking “outside the box” can save space, weight, cost and promote ease of assembly. The applications for this approach are endless. For any product in the automotive, aerospace, 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 extrude 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 contour 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, monitoring or enhanced functionality.

One last example is a product that is hot in today’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 product. 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, flattening it, and transferring this to the ECAD design tools, the designer is able to accurately analyze the flexible circuit design in the ECAD model.   Often when using a flexible circuit in an unusually shaped area, the added length required and bend areas are difficult to determine. This approach allows 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. Because 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 and this can potentially reduce the number of revisions during the design cycle.

To identify a structure that is not being utilized, 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 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 creativity and imagination. It is an exciting time to be involved in the world of flexible circuit design and manufacturing.

Please contact us for additional information!

Tara Dunn, Omni PCB   and  Mike Brown, IDS

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