Dragan Dinulovic

Integrated Electromagnetic Second Stage Microactuator for a Hard Disk Recording Head

A slider with an integrated microactuator (SLIM) allows actuating a read-write element of a hard disk drive (HDD) in both the vertical direction allowing a flying height adjustment as well as in the lateral direction allowing a second stage actuation. The microactuator system consists of a pair of electromagnetic variable reluctance (VR) micro actuators. The microactuator system is fabricated using thin-film technology. Each actuator has a permalloy C-core carrying a two-layer spiral Cu coil with a total of 16 turns. The insulation materials are SU-8 (in the lateral direction) and Si3N4 (in the vertical direction). The total size of one magnetic VR microactuator is 460 mum times 300 mum times 61 mum. This paper discusses design considerations, presents the FEM simulation conducted, describes the fabrication technology, and provides experimental results.

Microfabricated Inductive Micropositioning Sensor for Measurement of a Linear Movement

An inductive device with a moving core will change its inductance as a function of the core position. By extending this principle to a microtransformer with multiple evenly spaced cores, a measurement system combining features of analog (variable reluctance) and incremental positioning may be devised. For detecting the direction of motion system (to know in which direction to count), an incremental length-measurement system not only requires one, but two output signals, which have to be offset by 90deg. This paper presents a microtransformer-based positioning system fulfilling these requirements. It presents the fabrication technology employed and discusses experimental test results

Microtransformer with closed Fe-Co magnetic core for high frequency power applications

This paper presents a development of a microtransformer device fabricated using MEMS technology. The device is designed for higher switching frequencies beyond to 50 MHz power applications. The microtransformer features a closed magnetic core and six identity coils (three coils on primary and three coils on secondary side). Depending on connecting technique, this design allows a wide flexibility to set different values of inductance and of transformer winding ratio. As a magnetic core material Fe-Co alloy is applied, this device shows a significant improvement compared to the first fabricated prototypes with Ni-Fe magnetic core.

An approach for simulating magnetic microactuators

Micro electro-mechanical systems (MEMS) are fabricated by combining deposition and etching techniques in conjunction with photo lithography for patterning. Due to this complex fabrication approach it is nearly impossible to easily fabricate prototypes. As a result modeling and simulation techniques are applied in the design process for such devices. This paper pinpoints an approach for modeling and simulating an electromagnetic microactuator. Establishing analytical model allows coming up with a cursory design, while a finite element method (FEM) analysis allows furthering optimum design features.

Concept for a Wafer Level Test System for Measuring Magnetic Film Properties

Achieving the specified magnetic properties of magnetic thin- films is a precondition for a successful wafer fabrication of magnetic thin-film devices. In many cases, these films are anisotropic, with two main axes (hard and easy) perpendicular to each other. For a wafer level measurement along these axes, a new test approach is suggested: employing two micro sensors, each one measuring along one of the two desired axes and engaging them alternatively by means of a micro actuator. This paper discusses the suggested approach and presents a design for the micro sensors and the micro actuator.

On-chip high performance magnetics for point-of-load high-frequency DC-DC converters

This paper presents the design, fabrication, and characterization of on silicon integrated micro-transformers for high frequency power applications. The microtransformer device is used and tested in DC-DC converter application at high switching frequency. This device has stable L vs. f characteristic up to 50 MHz. The design is improved regarding to the electrical resistance and current capability. The microtransformer shows an inductivity of about 60 nH, resistance of 350 mΩ and can be applied for current up to 1.5 A.

Evaluation of an electromagnetic microactuator using scanning Hall probe microscopy measurements

Scanning Hall probe microscopy (SHPM) was used to evaluate integrated magnetic microactuators designed for hard disk drives. The Hall probe measurements of the generated magnetic field strength as a function of the applied current or distance were compared to results of a finite element method simulation. The SHPM measurements and simulation results are in good agreement, confirming that simulations supported by SHPM measurements can be used successfully to predict the performance of microactuators.

Operating Range Optimization of a Slider With an Integrated Microactuator (SLIM) for Hard Disk Drives

The paper describes the tests performed to determine the characteristics of four various leaf springs, as well as the evaluation of the mounting platform/chiplet motion as a function of the excitation current. For the leaf spring evaluation, a nanoindenter (Hysitron Tribo Indenter) was used. To determine the variation of the air gap as a function of the excitation current, optical microscopy as well as laser Doppler vibrometry (LDV) was applied.

IMPROVED FABRICATION OF AN INTEGRATED ELECTROMAGNETIC SECOND STAGE MICROACTUATOR FOR A HARD DISK RECORDING HEAD

A slider with an integrated microactuator (SLIM) allows actuating a read-write element of a hard disk drive (HDD) in both the vertical direction allowing a flying height adjustment as well as in the lateral direction allowing a second stage actuation. The microactuator system consists of a pair of electromagnetic variable reluctance (VR) micro actuators. The microactuator system is fabricated using thin-film technology. Each actuator has a permalloy C-core carrying a two-layer spiral Cu coil with a total of 16 turns. The insulation materials are SU-8 (in the lateral direction) and Si3N4 (in the vertical direction). The total size of one magnetic VR microactuator is 460 mum times 300 mum times 61 mum. This paper discusses design considerations, presents the FEM simulation conducted, describes the fabrication technology, and provides experimental results.

An iterative approach to simulate magnetic micro systems by changing the magnetic properties

Magnetic shape memory (MSM) metals are new ferromagnetic materials attractive for actuators applications. Applying an external magnetic field, the domains in the ferromagnetic MSM material align along the magnetic field direction. This not only results in a change in length (and with five to ten percent a quite substantial one), but also in an increase of the relative magnetic permeability mur of the MSM material. Therefore, modeling a device including MSM material is challenging. For such a case, a quasi-static approach is no longer feasible. Therefore, an iterative procedure had to be developed to dynamically simulate the magnetic properties of MSM devices. Design, modeling, and simulation of a magnetic system including MSM material were conducted by Finite Element Method (FEM) analysis. The simulations were executed using the software tool ANSYStrade.