Embedded inductor using Ni-Zn ferrite film in polymer substrate

It has been reported that the spin sprayed ferrite film shows better magnetic properties at high frequency than the ferrite by co-firing over 800 °C . Besides, there is no limitation to select the substrate materials because it can be processed with low temperature below 100 °C. Therefore, we fabricated a film inductor as a passive device for DC-DC converter by a use of spin sprayed Ni-Zn ferrite film on the polyimide layer without insulating layer. After, cover-lay film was laminated on the top of that. Finally, embedded form was completed by via hole process of pad opening. The magnetic properties of Ni-Zn ferrite were 6.0 k gauss of saturation magnetization and 110 of effective permeability. And 1,6 micro H of L, 25 of Q at 5 MHz were measured with spiral 16 turn inductor. The rated current of inductor was measured 897 mA.