Study on the Electric Performances of Planar Inductor With Fe-System Magnetic Flake Composite Integrated for SiP DC-to-DC Converter Applications

This paper describes the design, fabrication, and electric performances of planar inductors with Fe_0.76B_0.12Si_0.04C_0.08 (Fe-B-Si-C) flakes composite. These inductors were designed with the help of an analytical magnetic circuit calculation, a finite-element method electromagnetic field simulator, and the Jiles-Atherton hysteresis model with the segmentation model so as to attain the desired inductance of 0.5 μH and dc resistance of 100 mΩ. To verify the simulation results, the planar inductors with Fe-B-Si-C flake composite were fabricated, and their electric performances were investigated. The inductance of the fabricated inductor is 4-4.5 times as high as that of the air-core inductor. The dc superimposed inductance at 1 MHz with output current of 1.4 A is ~0.58 μH, which is only 17% less than the no-load inductance. Therefore, the fabricated planar inductors meet all of the required electric performances. In addition, the maximum efficiency reached 91.7% for 4 V input and 3 V output of a system in package dc-to-dc converter integrated with the inductor and a CMOS IC.