Planar, double-layer magnetic inductors for low power, high frequency DC-DC converters

Inhalt:
This paper presents the design and fabrication of micro-planar inductors with magnetic layers, as well as the corresponding experimental results. These spiral inductors are suitable for low power (1W) DC-DC monolithic converters. Sufficiently high switching frequency (>100MHz) enables a System-In-Package assembly with the micro-planar inductors underneath the active chip. Thick magnetic layers serve as a mechanical carrier and also present a double purpose of increasing the inductance value and suppressing electromagnetic interferences (EMI). Geometrical parameters are studied using an electromagnetic simulator for optimization purposes. A 500 nH spiral inductor with expected 140 mO RDC, 9 mm² footprint area is designed for operating at 100 MHz. A lab-scale technology has been developed. Samples are tested using a LCR meter in the 10 kHz to 100 MHz frequency range. The performances of the micro-inductors are compared to the predicted response of simulated equivalent model with good agreement.