Ferromagnetic Composite Wire Inductors

Abstract

In enabling small size light-weight portable devices and wireless electronics, miniaturization of microelectronic components has become a very important aspect for many modern technologies. As a fundamental electronic component, inductor has been extensively used in various power electronics and wireless applications. The performances of these circuitries are greatly dependent on the quality of the inductors, and the miniaturization and the integration of inductor with electronic circuit are the key to realize the electronic products with high performance, small size and light weight. Therefore, it has attracted worldwide research interests to fabricate the high performance passive micro inductors, especially magnetic film inductors. However, the available designs today have limited inductance gain or small Q, which in turn leads to the demands of both theoretical guidance in choosing efficient inductor design and the experimentally verified optimizations on the various parameters. On the other hand, tunable inductors have been shown promising because of their ability to optimize the circuit performance. The discrete tunable inductors available today are often tuned manually, and are large in size. Recent research efforts on miniature tunable inductors still possess some limitations such as high fabrication cost, non-continuous tunability, or high power consumption for inductance tuning.

The objective of this thesis is to propose, develop, model, parametrically study and optimize the high efficiency, high quality, innovative ferromagnetic composite wire inductors, including non-tunable inductors and tunable inductors.

The research approach was proposed and implemented. The magnetic microwire (NiFe/Cu) based inductor, as a candidate miniature inductor with high efficiency, has been proposed, modeled, fabricated, and characterized in an applied magnetic field environment. With the advantages of high quality factor and low power consumption, novel electrically tunable magnetic inductors based on micro NiFe/Cu composite wires, whose tuning effect is achieved by modulating the permeability of the soft magnetic layer in a magnetic film inductor, have been designed, fabricated, tested and analyzed. A theoretical model for the working mechanism of the tunable magnetic inductor was also developed. The effect of magnetic layer thickness, as one of the most important geometric parameters of ferromagnetic composite wire, on the magnetic properties of the microwires and the performance of the tunable magnetic inductors based on such composite wires, has been thoroughly investigated. To optimize the tunability and quality factor of the tunable magnetic inductor, the effect of current density and the effect of an applied longitudinal magnetic field in the electrodeposition of the magnetic layer on the performance of tunable magnetic inductor have been studied. The thermal stability of ferromagnetic composite wire based tunable inductors has also been studied. Moreover, micro NiFe/insulation/Cu composite wires have been developed and the effect of insulation layer on magnetic properties, impedance, inductance and quality factor of tunable inductors based on NiFe/insulation/Cu composite wire has been investigated. Finally, it can be concluded that the innovative ferromagnetic composite wire inductors have been successfully proposed, developed, modeled, parametrically studied thoroughly and optimized.