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In an integrated power microinductor, the size and shape of the magnetic material will have a relationship to the permeability and inductance of the device. To demonstrate these effects, a set of inductors with closed Ni45Fe55 films were fabricated having similar structures but different footprint sizes and aspect ratios (ARs). Magnetic and electrical characterization was performed on the devices to determine magnetic properties, and in both measurements the same relationship between film shape and magnetic anisotropy is observed. Micromagnetic shape anisotropy simulations were used to predict this behavior and correlate with the experimentally determined parameters. The AR of the film is determined to have a strong influence on the anisotropy and permeability of the magnetic film via shape demagnetization effects which is shown to be a significant variation from the as-deposited magnetic material parameters. [ABSTRACT FROM AUTHOR]

Abstract: Micro-inductors, with an electrodeposited nickel–iron core have been fabricated on silicon substrates, and have been characterized in the frequency range up to 100MHz. The core consists of a nickel iron, 45:55 alloy which is deposited using pulse-reverse electroplating in the presence of a magnetic field to control anisotropy. The operation of the inductors with low loss at high-frequency critically depends on core thickness, which is used to control eddy-current loss as the frequency is increased. However, it is shown that the permeability of NiFe 45/55 has a dependency on thickness, and decreases with increasing thickness. For example, the permeability is measured to be approximately 1000 for a 1-μm-thick film, decreasing to approximately 400 for a 5-μm-thick film. In order to correctly design micro-inductors for operation up to 100MHz, it is important that this characteristic of the material is taken into account. [Copyright &y& Elsevier]

• A micro-inductor has been fabricated using a MEMS process. • The device has a single layer copper winding sandwiched between two layers of core. • The micro-inductor has a footprint area of 2.9 mm2. • The measured inductance is 204 nH at 21.7 MHz and DC resistance is 470 m Ω. • The peak quality factor of the micro-inductor is 9.23 at 9.2 MHz. • The micro-inductor has been applied in a buck converter. • The achieved maximum converter efficiency is 81.74% at 20 MHz. • The micro-inductor has also been compared with an air core inductor embedded in PCB. • The 220 nH air core inductor has a large footprint area of 32 mm2. • The maximum converter efficiency is 85.47% when the air core inductor is applied. A micro-inductor has been fabricated on silicon substrate using a Micro-Electromechanical Systems (MEMS) process. The micro-inductor has a single layer copper winding sandwiched between two layers of electroplated NiFe core. It has a footprint area of 2.9 mm2, an inductance of 204 nH at 21.7 MHz, a DC resistance of 470 m Ω , and a peak quality factor of 9.23 at 9.2 MHz. The micro-inductor has been applied in a buck converter and achieved a maximum converter efficiency of 81.74% at 20 MHz. The performance of the micro-inductor has also been compared with an air-core inductor embedded in PCB. The air core inductor has a similar inductance of 220 nH, but with a large footprint area of 32 mm2. The maximum buck converter efficiency is 85.47% when the air core inductor is applied. [ABSTRACT FROM AUTHOR]