222 research outputs found
The manufacture and characterisation of microscale magnetic components.
Abstract unavailable please refer to PD
Radio Frequency Microelectromechanical Systems in Defence and Aerospace
For all onboard systems applications, it is important to have very low-loss characteristics and low power consumption coupled with size reduction. The controls and instrumentation in defence and aerospace continually calls for newer technologies and developments. One such technology showing remarkable potential over the years is radio frequency microelectromechanical systems (RF MEMS) which have already made their presence felt prominently by offering replacement in radar and communication systems with high quality factors and precise tunability. The RF MEMS components have emerged as potential candidates for defence and aerospace applications. The core theme of this paper is to drive home the fact that the limitations faced by the current RF devices can be overcome by the flexibility and better device performance characteristics of RF MEMS components, which ultimately propagate the device level benefits to the final system to attain the unprecedented levels of performance.Defence Science Journal, 2009, 59(6), pp.568-567, DOI:http://dx.doi.org/10.14429/dsj.59.156
Characterisation and integration of materials and processes for planar spiral microinductors with permalloy cores
The increasing density of electronics within portable electronic devices provides the
motivation to develop more compact power electronics, such as DC-DC converters.
Typically, integrated circuits and each passive component, such as inductors, are
discreetly packaged and mounted on printed circuit board (PCB), to implement the
converter. Hence for further size reduction there has been growing interest for
integration schemes such as Power supply in package (PwrSiP). However, the ultimate
goal is the monolithic integration of the power supply solution, in an integration
scheme known as Power Supply on Chip (PwrSoC).
The economic effectiveness of the converter will be determined by the device footprint
and number of processing steps required to fabricate the inductor. Hence, the
motivation behind this thesis is the need for microinductors with large inductance
density (inductance per device footprint) while maintaining low losses, which can be
integrated with silicon IC. Furthermore, the need for thick layers will result in issues
with yield and reliability of the fabricated device. Hence there is a need to identify,
characterise and integrate materials with low residual stress into the microinductor
fabrication process.
A typical choice of inter-coil dielectric is the photo-definable epoxy SU-8. However,
SU-8 suffers from intrinsic issues with high residual stress and adhesion. One possible
replacement for SU-8 as a structural and dielectric layer is Parylene-C. The first
objective of this thesis proposes a test-bed inductor process, which incorporates
Parylene as a structural and dielectric layer and has a short turnaround time of one
week. This fabrication process involves the filling of high aspect ratio gaps between
copper structures with Parylene and subsequent chemical mechanical planarisation,
and a test chip has been designed to characterise these processes. Additionally, Scotch-tape
testing has been used to confirm suitable Parylene adhesion to patterned and
unpatterned films used in this process. Subsequently, complete microinductors, with
magnetic cores, have been fabricated, characterised and benchmarked against other
inductor technologies and architectures reported in the literature.
Parylene is expected to produce films with low residual stress due to its room
temperature deposition process. However, the test-bed inductor process requires
thermal treatments up to 140°C. Hence it was necessary to characterise the stress in
Parylene films as a result of processing temperature and compare this to stress levels
in SU-8 5 and 3005 films. This study has determined the spatial variation of residual
stress in Parylene-C and SU-8 films, by combining automated measurements of strain
indicator test structures and local nanoindentation measurements of Youngâs modulus.
These measurements have been used to wafer map strain, Youngâs modulus, and
subsequently residual stress in these films, as a result of processing parameter
variation.
It is well known that placing ferromagnetic material in close proximity to current
carrying coils can further enhance the measured inductance value. However, the
conductive magnetic core is also a source of loss for the microinductor. Hence,
magnetic permeability, electrical resistivity and mechanical stress in the magnetic core
influence the inductance value, eddy current losses and reliability of the fabricated
microinductor, respectively. The ability to characterise these properties on wafer is
essential for process control and verification measurements. This thesis details a test
chip capable of routine measurements on NiFe films to characterise the spatial
variation of these properties. Furthermore, wafer mapping measurements are reported
to identify the correlation between high frequency permeability, electrical resistivity,
mechanical strain and the chemical composition of two-component Permalloy film
(NixFe(100-x)) electroplated on the surface of 100mm silicon wafers.
Finally, MEMS-based inductor fabrication processes typically require a number of
electrodeposition steps, which require conductive seed layers for the deposition of the
coils and magnetic core material. A typical choice of seed layer is copper. However,
due to copperâs paramagnetic behaviour (ÎŒ = 1) and low electrical resistivity
(Ï=6.69ΌΩ.cm) this layer contributes to eddy current losses, while acting as a thin
âscreening layerâ. It is very likely that using a magnetic seed layer, within the magnetic
core, will noticeably reduce eddy current related losses. However, detailed systematic
experimental studies on any such improvement have not been documented in the
literature. This study involves compositional, structural, electrical and magnetic
characterisation of Ni80Fe20 films electro-deposited on non-magnetic and magnetic
seed layers (i.e. copper and nickel respectively). Mechanical strain test structures and
X-ray analysis have been used to characterise the stress levels and structural properties
of Ni80Fe20 films electro-deposited on both copper and nickel seed layers. In addition,
planar spiral micro-inductors, both with and without patterned magnetic cores, have
been fabricated to determine the effect of patterning on their performance. This is in
addition to quantifying the improvement in the electrical performance resulting from the enhanced magnetic and resistive contribution provided by magnetic seed layers
Design and characterisation of a high energy-density inductor
Power electronics is an enabler for the low-carbon economy, delivering flexible and efficient control and conversion of electrical energy in support of renewable energy technologies, transport electrification and smart grids. Reduced costs, increased efficiency and high power densities are the main drivers for future power electronic systems, demanding innovation in materials, component technologies, converter architectures and control. Power electronic systems utilise semiconductor switches and energy storage devices, such as capacitors and inductors to realise their primary function of energy conversion. Presently, roughly 50% of the volume of a typical power electronic converter is taken up by the energy storage components, so reducing their weight and volume can help to reduce overall costs and increase power densities. In addition, the energy storage densities of inductors are typically much lower than those of capacitors, providing a compelling incentive to investigate techniques for improvement.
The main goal of this research was to improve the design of an inductor in order to achieve higher energy densities by combining significantly increased current densities in the inductor windings with the ability to limit the temperature increase of the inductor through a highly effective cooling system. Through careful optimisation of the magnetic, electrical and thermal design a current density of 46 A/mm2 was shown to be sustainable, yielding an energy storage density of 0.537 J/ kg. A principal target for this enhanced inductor technology was to achieve a high enough energy density to enable it to be readily integrated within a power module and so take a step towards a fully-integrated âconverter in packageâ concept. The research included the influence of the operating dc current, current ripple, airgap location and operating frequency on the inductor design and its resulting characteristics. High frequency analysis was performed using an improved equivalent circuit, allowing the physical structure of the inductor to be directly related to the circuit parameters. These studies were validated by detailed small-signal ac measurements. The large signal characteristics of the inductor were determined under conditions of triangular, high-frequency current as a function of frequency, current (flux) ripple amplitude and dc bias current (flux) and a model developed allowing the inductor losses to be predicted under typical power electronic operating conditions
Design and characterisation of a high energy-density inductor
Power electronics is an enabler for the low-carbon economy, delivering flexible and efficient control and conversion of electrical energy in support of renewable energy technologies, transport electrification and smart grids. Reduced costs, increased efficiency and high power densities are the main drivers for future power electronic systems, demanding innovation in materials, component technologies, converter architectures and control. Power electronic systems utilise semiconductor switches and energy storage devices, such as capacitors and inductors to realise their primary function of energy conversion. Presently, roughly 50% of the volume of a typical power electronic converter is taken up by the energy storage components, so reducing their weight and volume can help to reduce overall costs and increase power densities. In addition, the energy storage densities of inductors are typically much lower than those of capacitors, providing a compelling incentive to investigate techniques for improvement.
The main goal of this research was to improve the design of an inductor in order to achieve higher energy densities by combining significantly increased current densities in the inductor windings with the ability to limit the temperature increase of the inductor through a highly effective cooling system. Through careful optimisation of the magnetic, electrical and thermal design a current density of 46 A/mm2 was shown to be sustainable, yielding an energy storage density of 0.537 J/ kg. A principal target for this enhanced inductor technology was to achieve a high enough energy density to enable it to be readily integrated within a power module and so take a step towards a fully-integrated âconverter in packageâ concept. The research included the influence of the operating dc current, current ripple, airgap location and operating frequency on the inductor design and its resulting characteristics. High frequency analysis was performed using an improved equivalent circuit, allowing the physical structure of the inductor to be directly related to the circuit parameters. These studies were validated by detailed small-signal ac measurements. The large signal characteristics of the inductor were determined under conditions of triangular, high-frequency current as a function of frequency, current (flux) ripple amplitude and dc bias current (flux) and a model developed allowing the inductor losses to be predicted under typical power electronic operating conditions
Integrated thin film magnetics in advanced organic substrates
This thesis investigates the challenges of integrating thin film magnetics into advanced organic substrates for Power Supply in Package (PwrSiP) applications. The surface conditions of the substrate on which the thin films were deposited was found to play a critical role in terms of the magnetic performance and efficacy of the material used as the magnetic passive component. Whence, planarization of the underlying substrate, or a release process with which the magnetic core could be deposited, and later liberated from a polymer layer spun on smooth Si were developed in order to address the issue of surface roughness of the underlying substrate.
\newline\newline
The released magnetic thin films were incorporated into advanced organic substrates by three methods, as follows: 1) the integration of the released magnetic core using wirebonds; 2) the embedding of the released magnetic material using a Flip-Chip approach; 3) fully embedding the released magnetic material between the prepreg layers in the PCB stack.
\newline\newline
Finally, methods for the modelling and characterisation of the magnetisation dynamics of thin film magnetics were developed. The modelling of the magnetisation dynamics comprises two approaches: 1) development of software which enables large scale numeric modelling of the magnetic thin films using graphical processing units; 2) development of analytical models to characterise the magnetisation dynamics of magnetic thin films. Both the analytic and numeric methods were developed in order to characterise the issue of surface roughness in magnetic thin films, which was found to result in severely degraded magnetic performance. Furthermore, the thickness dependent multimodal behaviour of amorphous CZTB films spanning thickness 80nm â 500nm were investigated using Brownâs continuous diffusion model of magnetic spins. It was found that there is a critical film thickness whereat there is a breakdown in the induced uniaxial anisotropy within the film, and hence, that thickness should be considered the maximum useful thickness of the material in ultra-low loss PwRSiP applications
Aspects of magnetic pulse compression and pulse sharpening
Imperial Users onl
Development and Implementation of a Mouldable Soft Magnetic Composite
Electrical machines, chokes and induction heaters are found in most homes,offices and factories all over the world. They are used to create movement, filtrate the power or to generate heat. A typical unit consist of a coil and a flux conductor material. Some of the materials have been established for over 100 years, while others are only a couple of decades old.A new flux conductor material has been developed at the Division of Production and Materials Engineering at Lund University. The material is called soft magnetic mouldable composite (SM2C). This thesis is focused on investigating the potential of this material and lay a knowledge foundation, wherein the material properties and manufacturing process of the material is tested and further developed, as well as the material composition. In order to use the full potential of the material a holistic view of all the materials involved is necessary. Both coil and insulation suitable for the mouldable soft magnetic composite are therefore studied. Tests are performed both on the separate materials, but also together in applications. Several motors and induction heaters were built and tested in different projects.Results from the work show that by changing from solid copper tubes to litz wire and by using a flux conductor an increase of efficiency from 50-80 % to 98 % is possible. This is due to lower losses in the current conductor and higher flux linkage.The possibility to mould the soft magnetic composite has interesting potential. It is shown that sensors, current conductors and other soft magnetic materials can be integrated directly into the composite. Also, the technology will provide a good thermal contact between the materials. This is especially important for the current conductor, which is usually the main heat source. A good contact will help conduct away the heat if the device is designed properly.Other opportunities are opened with the new technology as well. The size of a moulded part has no limit, unlike for other soft magnetic composites that are usually pressed. It is possible to mould parts into almost any geometry, but it is also easy to machine the material if wanted
A Novel Variable Geometry based Planar Inductor Design for Wireless Charging Application
In this thesis, the performance, modelling and application of a planar electromagnetic
coil are discussed. Due to the small size profiles and their nonâcontact nature, planar
coils are widely used due to their simple and basic design. The uncertain parameters
have been identified and simulated using ANSYS that has been run utilising a newly
developed MATLAB code. This code has made it possible to run thousands of trials
without the need to manually input the various parameters for each run. This has
facilitated the process of obtaining all the probable solutions within the defined range
of properties. The optimum and robust design properties were then determined. The
thesis discusses the experimentation and the finite element modelling (FEM)
performed for developing the design of planar coils and used in wireless chargers. In
addition, the thesis investigates the performance of various topologies of planar coils
when they are used in wireless chargers. The ANSYS Maxwell FEM package has been
used to analyse the models while varying the topologies of the coils. For this purpose,
different models in FEM were constructed and then tested with topologies such as
circular, square and hexagon coil configurations. The described methodology is
considered as an effective way for obtaining maximum Power transfer efficiency (PTE)
with a certain distance on planar coils with better performance. The explored designs
studies are, namely: (1) Optimization of Planar Coil Using Multi-core, (2) planar coil
with an Orthogonal Flux Guide, (3) Using the Variable Geometry in a Planar coil for an
Optimised Performance by using the robust design method, (4) Design and Integration
of Planar coil on wireless charger. In the first design study, the aim is to present the
behaviour of a newly developed planar coil, built from a Mu-metal, via simulation. The
structure consists of an excitation coil, sensing coils and three ferromagnetic cores
2
located on the top, middle and bottom sections of the coil in order to concentrate the
field using the iterative optimisation technique. Magnetic materials have characteristics
which allows them to influence the magnetic field in its environment.
The second design study presents the optimal geometry and material selection for
the planar with an Orthogonal Flux Guide. The study demonstrates the optimising of
the materials and geometry of the coil that provides savings in terms of material usage
as well as the employed electric current to produce an equivalent magnetic field.
The third design study presents the variable geometry in a planar inductor to obtain
the optimised performance. The study has provided the optimum and robust design
parameters in terms of different topologies such as circular, square and hexagon coil
configurations and then tested, Once the best topology is chosen based on
performance. The originality of the work is evident through the randomisation of the
parameters using the developed MATLAB code and the optimisation of the joint
performance under defined conditions.
Finally, the fourth design study presents the development of the planar coil
applications. Three shapes of coils are designed and experimented to calculate the
inductance and the maximum power transfer efficiency (PTW) over various spacing
distances and frequency
- âŠ