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INNOVATION 3D-MID – an alternative to PCBs I

n industrial manufacting, more and more are turning to an alternative technology to classic PCBs. 3-D MID (Moulded Interconnect Devices

or Mechatronic Integrated Devices) are injection-moulded plastic parts with conductive traces integrated by using laser direct structuring (LDS). This technique adds power to the trend towards miniaturisation in the electronics industry and provides product developers with new design opportunities. The projects which Multiple Dimensions, one of the world’s foremost suppliers in this field, has undertaken illustrate the diversity of possible applications for 3D-MID. They simplify the operation of household appliances, improve driver experience in power steering systems and open up new ways of saving space – for example in sensing and industrial electronics. Johannes Schmid, Managing Director of Swiss company Multiple Dimensions explains how these fine, golden traces on formed plastic are transforming industrial production. “The basis of all 3D-MID applications is a thermoplastic material,” he says. “Using injection moulding, we first manufacture the part to fit the application. We use different types of thermoplastic, which contain an additive that can be activated by laser.” A laser ray then engraves the surface of the plastic and activates the additive. A

❱ ❱ Multiple Dimensions (above) use Integrated conductive traces which can replace wired mechanical components (below)

copper bath then follows, which lets the conductive traces form directly on the thermoplastic. Depending on the type of application, the MID parts may have to be extremely robust or temperature- resistant. “Some even have to be acid or sweat-resistant, for example applications

for hearing aids or headphones,” says Schmid. In a final step, a barrier layer of nickel is applied and then conditioned with a thin layer of gold to ensure good solderability. What differentiates the company from the competition is that it produces traces in almost microscopically small dimensions. “Most suppliers are currently working with 300 to 400µm spacing between traces, but our technological limit for trace width is 80µm. These fine structures are now often used in Point of Sales (POS) terminals as a protection from hacking attacks. The fine traces allow attacks on the data in the payment cards to be detected.” Trace width and spacing is the main factor affecting the degree of miniaturisation and it is decisive in terms of the number of functions that can be integrated in a component. “Rotary switches for programme selection in washing machines are normally made of a whole kit of small mechanical parts - with 3D-MID technology none of these are now needed,” Schmid says. “The washing programme is selected using a capacitive switch - virtually touch-free. This has far-reaching consequences: Unlike a mechanical switch, there is no friction to wear out the parts. Our operator control device has a much simpler design, costs less to produce and on top of that, it has a longer service life.” Multiple Dimensions manufactures sensors for the automotive industry which are used to measure the torque and position of steering wheels. “Depending on the position and the measured value, the drive of the power steering is increased or decreased. The more accurate the measurement, then the more directly the vehicle response is felt,” Schmid says. “Just as in the washing-machine, the conventional device contains numerous mechanical parts. When all these parts work together, deviations and tolerances cumulate and impair the driving experience. We are able to eliminate an entire chain of tolerances.” EE

Electronics Testing 2018 /// 9

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