Planar inductors for high frequency DC-DC converters using microwave magnetic material

Paper presents simulation and primary experimental results about the fabrication of planar inductances for monolithic DC/DC converters in System-In-Package environment. A microwave magnetic material (YIG) and electroplated copper winding are proposed. A low-cost manufacturing process is proposed that uses dry film instead of UV SU8 resin. Literature details similar manufacturing processes but the proposed magnetic material enables to operate in the 100 MHz range. Simulation results based on HFSS and Flux2D simulators present the sensitivity of the inductor to geometrical parameters. Samples have been fabricated for a 1 W, Vin = 3.6 V, Vout = 1 V converter and a switching frequency above 100 MHz. An optimized 25 nH inductor with expected 50 m Omega R_DC, 3 mm² has been designed. Primary results indicate that the nH/(m Omega.mm²) metric is promising and truly comparable to already published results.