Manufacturing and Characterization of Planar Transformers as Molded Interconnect Device Technology Component for an Industrial Production

The increase in battery-powered handheld devices is driving the demand for faster charging converters. Gallium Nitride (GaN) converters allow frequencies of above 500 kHz, enabling a smaller footprint especially for magnetic components. In this paper molded interconnect device (MID) transformers with a height of 2.5 mm are produced via a two-step injection molding process using polyether ether ketone (PEEK) granulate. The two- step injection molding process encapsulates a water jet-cut ferrite core. Laser Direct Structuring (LDS) creates the coils around the core. This process produces multiple transformers in two designs with inductance values around 19 μH and 28 μH, each boasting a high coupling coefficient exceeding 95 %. CT images reveal cracks in the ferrite core after the second injection molding step, explaining discrepancies between measured and simulated results. Nevertheless, MID transformers can skip the complex process of winding and are already packed, which can lower the cost for an industrial production.