S.C.O. Mathuna

Magnetics on silicon: an enabling technology for power supply on chip

Data from the ITRS2003 roadmap for 2010 predicts voltages for microprocessors in hand-held electronics will decrease to 0.8V with current and power increasing to 4A and 3W, respectively. Consequently, low power converters will move to multimegahertz frequencies with a resulting reduction in capacitor and inductor values by factors of 5 and 20, respectively. Values required at 10 MHz, for a low power buck converter, are estimated at 130 nH and 0.6 uF, compatible with the integration of magnetics onto silicon and the concept of power supply-on-chip (PSOC). A review of magnetics-on-silicon shows that inductance values of 20 to 40nH/mm/sup 2/ can be achieved for winding resistances less than 1/spl Omega/. A 1-/spl mu/H inductance can be achieved at 5 MHz with dc resistance of 1/spl Omega/ and a Q of four. Thin film magnetic materials, compatible with semiconductor processing, offer power loss density that is lower than ferrite by a factor of 5 at 10 MHz. Other data reported includes, lowest dc resistance values of 120 m/spl Omega/ for an inductance of 120 nH; highest Q of 15 for an inductance of 350 nH and a current of 1 A for a 1- /spl mu/H inductor. Future technology challenges include reducing losses using high resistivity, laminated magnetic materials, and increasing current carrying capability using high aspect-ratio, electroplated copper conductors. Compatible technologies are available in the power switch, control, and packaging space. Integrated capacitor technology is still a long-term challenge with maximum reported values of 400 nF/cm/sup 2/.

PCB integrated inductors for low power DC/DC converter

This paper discusses the use of printed circuit board (PCB) integrated inductors for low power DC/DC buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 /spl times/ 10 mm/sup 2/. The magnetic layers consist of electroplated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional magnetic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 /spl mu/H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 /spl times/ 10 mm/sup 2/ and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and compact converter solutions.

Thick photoresist development for the fabrication of high aspect ratio magnetic coils

This paper reports the fabrication of coils for micro-magnetic devices on silicon using thick photoresists commonly used in the manufacture of microelectromechanical systems. A comparison of three photoresists, EPON SU-8, AZ 4562 and AZ 9260, is presented for the fabrication of high aspect ratio conductors. With a thickness of 81 μm, aspect ratios of 6:1 are obtained using the AZ 9260 photoresist. RF inductors and micro-transformers for power conversion applications are fabricated using this technology. The quality factor of the RF inductors shows maximum values of 23 at 0.4 GHz. Very good measurement is also obtained with the micro-transformers: the resistance of the electroplated copper windings is 0.3 Ω up to 2 MHz.

Modelling and analysis of a magnetic microactuator

This paper describes the operation of a magnetic microactuator. A prototype device consisting of a Nd-Fe-B permanent magnet, a silicon membrane and an electroplated copper coil is used to verify models and to predict the deflection of the magnetic microactuator. The analysis of this device involves the investigation of its electromagnetic and mechanical behaviour using analytical methods and finite . element analysis FEA . A design procedure for a magnetic microactuator is also outlined. The prototype device was characterised and the measured results compared to the theoretical data. Results show that the deflection of the device may be predicted to an accuracy of 20%. q 2000 Elsevier Science S.A. All rights reserved. .

Technology Roadmapping for Power Supply in Package (PSiP) and Power Supply on Chip (PwrSoC)

This paper presents a review and summary of the PSMA “PSiP2PwrSoC” special project that investigated the technology and performance underpinning recent commercial developments in Power Supply in Package and Power Supply on Chip. The results of this study are based on the identification of more than 28 commercial products, six of which were analyzed in detail, both physically and electrically. The methodology of the project is described and some of the salient results of this benchmarking effort are presented. In this study, a representative subset of the available commercial products was selected and a comprehensive physical, electrical and thermal performance analysis was carried out. The objectives were to identify the components, materials and assembly technologies used, and to determine if the drive toward greater integration and higher power density affected the performance of newer devices. The results of the analysis were then used to determine the current state of the technology in this application space, to show how it has developed to date and to predict how it might progress in the future. These results are presented in a generic format that does not identify individual products. This project was co-sponsored by the PSMA and member companies. The final report of the project, which includes more detailed information on the reviews described here as well as considerable trending analysis, is now available.

MCM-L integrated transformers for low power applications

Designs for planar magnetic core structures fabricated in printed circuit board (PCB) technology have been developed by the authors. The technology is applied to producing integrated transformers for low power conversion in this paper. It involves using processes and materials which are compatible with existing PCB techniques, and structures are designed to be integrated with other circuitry in a typical PCB layer count. Structures are designed to support voltage levels of up to 18 V at 3 W power.

A 20-MHz 1.8-W DC–DC Converter With Parallel Microinductors and Improved Light-Load Efficiency

The purpose of this paper is to show that distributing microinductors in parallel can reduce light-load losses, while also maintaining the same overall footprint area and the same effective inductance as a single microinductor. The performance of parallel microinductors is compared in a number of configurations to demonstrate which configuration provides the best overall performance in terms of circuit size, conversion efficiency, and power handling. Light-load saving techniques are implemented demonstrating the potential of parallel inductors to improve efficiency at light-load. Measured and modeled results of efficiency versus load are presented for the prototype DC-DC converters explored, and a peak efficiency of 74% is predicted for a 1.8 W, 20-MHz DC-DC converter including microinductors.

Electrochemical process for the lamination of magnetic cores in thin-film magnetic components

The lamination of the core in thin film magnetic components is necessary to reduce the eddy current losses of the structure at high frequencies. The usual way to achieve lamination of the core is by physical vapor deposition (PVD) techniques. These methods are however costly and the deposition of layers is non selective. In this article, an almost entirely aqueous-based electrochemical process for the lamination of magnetic cores is presented. The process uses an electrodepositable photoresist Eagle 2100 ED codeposited with a catalyst (palladium). The Eagle layer is left as an insulator and the catalyst allows the activation of the layer for subsequent metallization. The process can be reproduced as many times as required for producing the multilayers. It is also selective: it does not require multiple photolithography steps. As a demonstration of the multilayer process, a core constituted of two layers of Ni/sub 80/Fe/sub 20/ (6 /spl mu/m each layer), separated by an Eagle insulating layer, electroplated over three-dimensional structures, was produced.

Integrated passives in advanced printed wiring boards

This paper will focus on the work which was carried out under the Brite‐EuRAM funded project, COMPRISE (BE 96‐3371), the objective of which was to develop new materials and manufacturing processes to embed passive components (resistors, inductors, capacitors) within printed wiring structures fabricated from laminate materials. For the realisation of integrated resistors, a commercially available planar resistor material is incorporated in different test structures. The technology consists of a copper foil of standard thickness on which a resistive layer is deposited by means of electroless plating. For the realisation of capacitors in multi‐layered PCB structures, significant progress was made in the development and fabrication of very thin laminates. Higher dielectric constants of these laminate materials enable the increase of the capacitance per unit area. For inductors, both aircore (no magnetic material) and magnetic core components have been investigated.

Analysis of the performance of integrated inductors (fabricated in MCM-L technology) in RF amplifier applications

Research in integrated passive components is becoming more widespread, as the advantages of increased reliability, reduced cost and improved performance are recognised. The subject of this paper is the integration of inductor components in MCM-L technology for RF applications. A detailed analysis of the sensitivity of an RF amplifier to components of parasitic impedance associated with MCM-L integrated inductors is presented. SPICE circuit models are used for this purpose. The performance of a range of integrated test devices is compared with specifications for equivalent commercial devices. Inductance values ranging from 4.5-27.4 nH are produced, with Q-values of up to 100. Such performance is shown to be perfectly suited for the application of integrated inductors in RF amplifier circuits.