Design and Demonstration of Dual-Core Spiral Package-Embedded Inductors for Integrated Voltage Regulators

Abstract

Novel package-embedded inductors utilizing a dual-core spiral topology, designed for improved performance in integrated power delivery systems, are presented in this article. The proposed inductor features a simple fabrication process, gapped magnetic cores for stable performance across varying operating conditions, and overlapping spiral windings in adjacent layers, achieving high inductance density. The proposed topology consists of a spiral-shaped conductor winding layer sandwiched between two magnetic core layers. The conductor and insulating dielectric layers separate the cores and act as an air gap for the magnetic flux of the spiral inductor. The air gap causes an increase in the saturation current performance of the inductor. In addition to the single spiral winding, two advanced spiral inductor configurations, namely, two spiral windings in series and parallel, are explored. To enable design, a physical model and analytical monomial expressions are provided for inductance calculation. To evaluate the performance of these designs, three inductor samples are fabricated with two different magnetic core materials and air gaps. Overall, package-embedded dual-core spiral inductors with a performance of 115-nH inductance with 5-A saturation current and 330-nH inductance with 3.5A saturation current, occupying a 9- $\text {mm}^{2}$ area and having efficiencies ranging from 75% to 80%, are demonstrated.