Since 1998, 2E mechatronic has been a member in 3D-MID e.V., Nuremberg, and has been dealing with MID technology (Mechatronic IntegratedDevices). The target is miniaturisation of microsystem technical components and systems, as well as functional integration at concurrent reduction of the parts diversity. At the moment, there are three common methods to produce MIDs on the market. Two methods are to be only mentioned briefly here, since one procedure covers by far the greatest part of the serial applications now. The 2C method (2-component injection moulding) uses a metalisable and a non-metalisable plastic. After the injection processes, the resulting plastic compound goes through various metallisation baths without external current with the target of closed conductor structures having formed on the metalisable plastic at the end of this process. Afterwards, equipment with electrical parts usually takes place. The procedure is suitable particularly for very high piece numbers, since two injection moulding tools are needed and changes to the conductor pattern usually require investments in new tools. The minimum conductor width in this procedure is approx. 250µm.
Example: 2K demonstrator by PKT (red = non-metalisable plastic, gold = metalisable plastic after metallisation)
Another way of producing MID is the hot embossing process. Different thermoplastics can be used here. They do not have to be metalisable, i.e. doped with metal cores. This reduces the material costs for the circuit carrier. However, only two-dimensional parts can be produced in this method, since the conductors are produced by embossing of a copper film (with different surfaces) into the plastic body with an embossing stamp. The special film is available in different thicknesses from approx. 18µm-70µm by default. The metallisation process is dispensed with here, but hot-embossing stamps that determine the conductor layout must be produced for embossing. When embossing, the conductor layout is embossed in the plastic due to the structure shown raised in the upper embossing stamp and the film is at the same time sheared off at the conductor edges. The remaining foil is then removed and the circuit carrier (if desired) equipped with electrical components or contacts. The adhesive strength of the conductors corresponds about to that of FR4 PCBs. The minimum conductor width is approx. 300µm.
Example: Automotive seat adjustment switches
The most frequently used MID procedure at this time is the LDS (Laser Direct Structuring). The LDS procedure as well as the 2C procedure relies on plastics with a special doping of metal cores. In contrast to 2C injection moulding, however, the LDS procedure does not require two different plastics to be used. The 3D circuit carrier is sprayed from the metalisable plastic in one injection moulding process. Afterwards, the surface is written on with a special laser from LPKF that also holds the patent for this procedure. The laser roughens up the surface and exposes the crystallisation cores so that the copper atoms can dock in the subsequent metallisation process without external current and a closed conductor structure can be formed. The typical layer structure is: 4-8µm copper, 2-4µm nickel and finally 0.1µm gold. The minimum conductor width in the LDS procedure is approx. 150µm; by using a fine-focus laser, smaller widths are possible as well. After metallisation, the electrical or other parts are applied and contacted with any known AVT process, such as vapour-phase soldering or bonding. The only investment needed essentially is an injection moulding tool. If the conductor layout changes, it only needs adjustment of the software for the laser. Since the procedure as such has most benefits, it is now used in production of most serial parts. The most popular LDS-MID application is that of the smartphone antenna. The automotive industry also uses many LDS-MID now. Other exciting applications are found in the new development or redesign of medical technology or industrial products. Examples for this include LED light elements developed and produced by 2E or a miniaturised thermal flow sensor (photographs at the end of the article). In the scope of the BMBF-promoted research project MELAM 3D, a demo module was developed that points to the possibilities of LDS-MID technology. This module can be purchased free of charge from 2E.
True to the motto: A picture says more than 1000 words, a template says more than 1000 pictures, and 2E offers fast production of functional samples from the original materials using close-to-serial processes as well. Corrections to the layout can be made easily by adjusting the software where necessary.