Planar inductor with ferrite layers for DC-DC converter

We fabricated planar inductors with ferrite layers by a screen printing, photolithography, and electroplating process. The screen printing method made it possible to obtain a coil spacing filled with ferrite. In this structure, the perpendicular leakage magnetic flux preferentially passes through the coil spacing and bypasses the copper conductor line, a path that is expected to reduce eddy current loss. Trial samples of a planar inductor with ferrite layers achieved a high-quality Q factor of 40-70 at 5 MHz. Magnetic field analysis revealed that the eddy current loss of the conductor line was only 2.4% of total loss.