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Of all of the technical user presentations I attended at the AltiumLive design summit in Munich, the one I found most fascinating introduced an innovative technology that encouraged a bit of lateral thinking and appealed to my creative side. “IMSE: Creating Smart Surfaces with Electronic Functionality” was the title of the presentation by Sini Rytky, VP of product management, and Tuomas Heikkilä, senior hardware specialist, both from TactoTek in Finland.
Rytky explained that IMSE stood for injection-moulded structural electronics—a technique for integrating flexible printed circuitry and electronic components into three-dimensional moulded structures with touch-sensitive functional surfaces, using standard high-speed manufacturing methods and equipment.
The IMSE manufacturing process was logical and straightforward in concept. Starting with a flat thermoplastic film—typically a polyurethane or an in-mould labelling film—standard printed-electronics techniques were used to apply conductive features such as circuitry, touch controls, and antennas as well as decorative features and user-interface graphics. Surface-mounted components and LEDs were added by standard pick-and-place techniques while the substrate was still flat—presumably using conductive adhesive, although this was not disclosed. Then, the assembly was thermoformed into a three-dimensional shape and injection-moulded to form a thin, lightweight, functional unit with a smart, touch-sensitive surface and all of the electronics fully encapsulated and embedded. Of the numerous potential application areas, the most obvious was the integration of touch controls into automotive interior trim.
Designs could incorporate one or two films with electronics on one or both. Rytky showed an example of the stackup for a two-film structure. The top surface layer was an in-mould labelling film—although it could have been a natural material like leather or wood—printed with decorative inks. Next, came the first electronic layer, which was printed with conductive and dielectric inks and assembled with SMT components. At the centre of the stack was a layer of thermoplastic resin, polycarbonate, or polyurethane; then, the second electronic layer; and finally, an in-mould labelling film. Rytky stressed that the essence of IMSE design was to understand how these different materials and components would behave once they were put together, stretched to a three-dimensional form, and ultimately injection-moulded into a single unit.
Because IMSE enabled electronic functionality to be integrated into three-dimensional surfaces and in space-limited locations, there was enormous scope for innovative design, and decorative surfaces could be made functional without changing their mechanical structure. Further, conventional electronic assemblies could be substantially reduced in thickness, weight, and complexity.
An example demonstrated by Rytky and passed around the audience was a typical automotive overhead control panel. In its conventional form, it was a bulky structure, 45-mm thick, and weighing up to 1.4 kg with 64 individual mechanical parts, and its assembly required 30 separate operations. In terms of durability and reliability, the structure was fully encapsulated and protected from debris and moisture, and fully functional over a -40°C to +80°C temperature range. In another automotive example, touch-sensitive illuminated seat controls had been integrated within a real-wood door trim and the overall thickness was only 3 mm.
To read the full article, which appeared in the April 2019 issue of Flex007 Magazine, click here.