Embedded planar power inductor technology for package-level DC power grid

Abstract

Two types of embedded planar power inductors in an organic interposer were developed to establish the package-level DC power grid with tens MHz switching CMOS switch “Point-of-Load” DC-DC converter. One was the Zn-Fe ferrite core planar spiral inductor, and the other had the hybrid core with Zn-Fe ferrite and Carbonyl-iron/epoxy composite core. Zn-Fe ferrite core was made by spin-spray method through low temperature of 90 degrees-C. Carbonyl-iron/epoxy composite core was made by metal mask printing using composite paste and then 140 degrees-C curing. Their low temperature magnetic core fabrication was necessarily to embed the inductor in the organic interposer. The fabricated inductors with a footprint of 1mm-square and a height of about 70 µm exhibited 5.6 – 6.6 nH inductance, Q-factor of 12 – 16 at around 50 MHz and 1 A over rating superimposed DC current.