Fabrication of Planar Power Inductor for Embedded Passives in LSI Package for Hundreds Megahertz Switching DC–DC Buck Converter

Recently, research and development of integrated low-voltage dc-dc converter to LSIs has been active. In order to realize such integrated dc power supply, power magnetic devices must be integrated in it. The authors have fabricated planar power inductor embedded in LSI package for hundreds megahertz switching dc-dc buck converter. In this study, two types of planar power inductors have been fabricated: one was spin-sprayed Zn-ferrite thick film magnetic core inductor, and the other was composite magnetic core (Fe-based amorphous/polyimide) inductor. Footprint of the fabricated inductors was 850×850 μm², their inductance was about 10 nH, and the quality factor Q was about 20 at 100 MHz. The rating current which depends on the superimposed dc characteristic was at least up to 2 A.