High Power Density Devices Research Articles

A High Temperature, High Power Density Package for SiC and GaN Power Devices

In this work, a compact 600 – 1700 V high current power package housing either silicon carbide (SiC) or gallium nitride (GaN) power die was designed and developed. Several notable configurations of the package include diode half-bridges, co-packed MOSFET-diode pairs, and cascode configured GaN devices. In order to avoid a significant redesign effort for each new application or improvement in device technology, a device-neutral design strategy enables the use of a variety of die types from any manufacturer depending on the end-use application's requirements. The basic SOT-227 is a widely used package type found in everything from electronic welders and power supplies to motor controls and inverters. This module is a variant of that style of package which also addresses some issues that a standard SOT-227 package has when used in higher voltage applications; it has increased creepage and clearance distances which meet IPC, UL, and IEC standards up to 1700 volts while retaining an isolated substrate. It also has low parasitic values in comparison to the SOT-227. One of the key elements of this design is the removal of the baseplate. This allows for far lower weight, volume, and cost as well as reduced manufacturing complexity. The wide bandgap power package is composed of high temperature capable materials, which allow for the high junction temperatures inherent in these high power density devices. This paves the way for the design of a small, low-profile package with low parasitic inductances and a small junction-to-case thermal resistance. This paper will discuss the mechanical design of the power package as well as the three-dimensional finite-element modeling and analysis of the thermal, electrical, and mechanical characteristics. In addition, the electrical characteristics as a function of temperature of the power module up to 225 °C will be presented.

3D Nanostructured Binder Free Electrodes for Novel Energy Storage Devices

Energy-storage technologies, including supercapacitors with high power density and rechargeable batteries with high energy density, have attracted significant attention for applications in electric vehicles, power line conditioners, and load leveling of solar energy and wind power. However, for such applications, the demand for both high power density and energy density devices is becoming increasingly important. Thus, novel hybrid energy storage devices combining the advantages of supercapacitors and batteries is becoming a hotstopic in the energy storage research field. In previous work, the 3D nanostructured binder free electrodes have been shown to deliver high discharge capacity and excellent rate capability, which were assessed using Li-ion half cells [1-4], indicating that energy storage devices with high energy and power density may be achieved using such kinds of 3D electrodes. In this work, novel Li-ion full cells and supercapacitors were designed and fabricated using MnOx-based 3D electrodes, a manganese oxides based Li-ion full cell is shown in Figure 1a-c. The electrochemical performances of the different energy storage devices were assessed using a 3-electrode cell, as shown in Figure 1 d-f. The maximum energy density of the manganese oxides based Li-ion full cell is 223 Wh/kg at 146 W/kg. The Sn and Si based 3D anodes were also prepared and assessed using both Li-ion half cells and Li-ion full cells. Figure 1 (a)Figure 1 (b)Figure 1 (c)Figure 1 (d)Figure 1 (e) Figure 1: (a) Scheme of the manganese oxides based Li-ion full cell. S(T)EM images of the nanostructured LiMn2O4 cathode material (b) and the 3D C/MnOy/ACNTs anode materials (c). Two- and three-electrode charge (d) and discharge (e) voltage profiles of the manganese oxides based Li-ion full cell utilizing Li metal reference.

Energy Analysis of Hybrid Power Source During Vehicle Motion

This paper proposes a perfect energy source provided by a polymer electrolyte membrane fuel cell (PEMFC) as the main power source and a storage device, battery and super-capacitor, for a modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid systems is balanced by the DC bus regulation in dependence to the drive cycle. A super-capacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a DC bus. A battery module, as a high energy density device, operates to supply energy to the super-capacitor bank in order to keep it charged. The control strategy is used to determine the real-time optimal power distribution by simple minimization.

Ball Grid Array Solder Joint Reliability Under System-Level Compressive Load

Heatsinks have been widely used in the electronics industry as a thermal solution for high-performance and highpower-density devices. The thermal efficiency of heatsink solutions may be improved by increasing the compressive load applied on the interface between the electronic package and heatsink. Typical approaches for heatsink retention, however, would also lead to high levels of compressive load on the package ball grid array (BGA) solder joints. In this paper, the effect of compressive load on SnPbAg solder joint reliability is investigated by using both experimental and numerical approaches. Accelerated system-level solder joint reliability tests under temperature cycling and isothermal aging conditions, with the presence of compressive loads, are first performed to identify and characterize the critical reliability failure mode. Creep constitutive behavior under compression is then characterized and implemented in numerical finite-element simulations for developing a phenomenological model of the BGA solder joint failure under compressive loading. A life prediction formula for SnPbAg solder joint subject to constant compressive load is also proposed.

Vehicle hybridization with fuel cell, supercapacitors and batteries by sliding mode control

This paper treats the design and control of two hybrid source using supercapacitors, fuel cell, with and without batteries on the DC link. A fuel cell, as a slowest dynamic source in these systems (because of its auxiliaries) acts to supply the permanent energy. The supercapacitors, as a high dynamic and high power density device, compensate the intrinsic limitations in embedded sources and shave transient power peaks. The batteries module, as a high energy density device, operates for supplying energy if limitations of the power and energy sources occur. The load is a single phase DC machine connected directly in the DC bus. Our interest is focused on the comparison of the two structures and on the principles of control of this two hybrid power sources. Some results are presented and discussed.

Modeling and Control of Fuel Cell/Supercapacitor Hybrid Source Based on Differential Flatness Control

Fuel-cell vehicles (FCVs) with energy storage (ES) device(s) could result in improved lifetime, performance, fuel economy, and reduced cost. This paper presents the utilization of an ES device consisting of a supercapacitor bank for future electric vehicles with a hydrogen fuel cell (FC) as the main power source. The study mainly focuses on the innovative control law based on the flatness properties for a FC/supercapacitor hybrid power source. Utilizing the flatness principle, we propose simple solutions to the hybrid energy-management and stabilization problems. A supercapacitor module, as a high dynamic and high-power density device, functions to supply energy to regulate the dc-bus energy. The FC, as a slower dynamic source in this system, functions by supplying energy to keep the supercapacitor module charged. To ensure energy-efficient operation of the FC stack, the output current ripple of the FC stack is minimized by parallel boost converters with an interleaving switching technique for a high-frequency ripple by the supercapacitor for a low-frequency ripple. To authenticate the proposed control laws, a test bench is realized in the laboratory. The control algorithm (energy and current control loops) is digitally implemented by dSPACE controller DS1103. Experimental results with small-scale devices (a proton exchange membrane FC (PEMFC) of 500 W, 50 A, and 10 V and a supercapacitor bank of 250 F, 32 V, and 500 A) substantiate the excellent performance during load cycles.

Energy management of fuel cell/battery/supercapacitor hybrid power source for vehicle applications

This paper proposes a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. A supercapacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a dc bus voltage. A battery module, as a high energy density device, operates for supplying energy to a supercapacitor bank to keep it charged. A FC, as a slowest dynamic source in this system, functions to supply energy to a battery bank in order to keep it charged. Therefore, there are three voltage control loops: dc bus voltage regulated by a supercapacitor bank, supercapacitor voltage regulated by a battery bank, and battery voltage regulated by a FC. To authenticate the proposed control algorithm, a hardware system in our laboratory is realized by analog circuits and numerical calculation by dSPACE. Experimental results with small-scale devices (a PEMFC: 500-W, 50-A; a battery bank: 68-Ah, 24-V; and a supercapacitor bank: 292-F, 30-V, 500-A) corroborate the excellent control principle during motor drive cycle.

Fabrication of biomolecule–copolymer hybrid nanovesicles as energy conversionsystems

This work demonstrates the integration of the energy-transducing proteinsbacteriorhodopsin (BR) from Halobacterium halobium and cytochromec oxidase (COX) from Rhodobacter sphaeroides into block copolymeric vesicles towards thedemonstration of coupled protein functionality. An ABA triblock copolymer-basedbiomimetic membrane possessing UV-curable acrylate endgroups was synthesized to serveas a robust matrix for protein reconstitution. BR-functionalized polymers were shown togenerate light-driven transmembrane pH gradients while pH gradient-induced electronrelease was observed from COX-functionalized polymers. Cooperative behaviour observedfrom composite membrane functionalized by both proteins revealed the generation ofmicroamp-range currents with no applied voltage. As such, it has been shown thatthe fruition of technologies based upon bio-functionalizing abiotic materials maycontribute to the realization of high power density devices inspired by nature.

Substrate removal of AlGaN/GaN HEMTs using laser lift‐off

AlGaN/GaN high electron mobility transistors are very promising for microwave power applications. Integration and packaging of those high power density devices requires specific attention to thermal management, especially when the AlGaN/GaN heterostructures are grown on sapphire substrates. Indeed, the low thermal conductivity of sapphire is limiting the power performance of the devices. To improve the thermal management, we propose to remove the sapphire substrate after the HEMT processing. In this paper we show that the sapphire substrate can be removed using laser lift-off, without any substantial degradation of the HEMT properties. This is a first important step towards a system-in-a-package integration of AlGaN/GaN HEMTs for RF power applications. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

X–Ray Surface and Volumetric Heat Deposition and Tritium Breeding Issues in Liquid-Protected FW in High Power Density Devices

Innovative concepts are being explored and evaluated in the Advanced Power Extraction (APEX) study to enhance the capability of removing high power density and surface wall load while satisfying all other blanket functional requirements. The minimum surface and neutron wall load considered is ∼1.5 MW/m2 and 7 MW/m2, respectively, with account taken for peaking factors. Liquid first wall is among the concepts considered in which a flowing layer is introduced from the top of the Tokamak. Liquid lithium, Flibe, and Li17Pb83 are among the candidate materials considered. The objectives of the present work are: (a) determination of the spatial range over which X-ray from the plasma deposits its energy across the protective liquid layer under a realistic spectrum, (b) evaluation of the impact of difference in the neutron moderation among the liquid studied on the volumetric heat deposition rate across the layer as well the structured blanket behind it, and (c) assessment of the percentage of tritium bred only in the liquid layer relative to the total tritium bred in the entire system. In this paper, it is shown that X-ray deposits its energy over a finite depth in the layer; contrary to what have been assumed in previous studies. This assessment gives the correct input source for the thermal hydraulic analysis and leads to a large decrease in the liquid surface temperature. It is shown that: (a) still high heat deposition rate is attainable at the layer surface due to the fraction of the Bremsstrahlung spectrum below ∼80 eV (Li) and ∼200 eV (Flibe) which constitutes only ∼0.4% of the incident spectrum, (b) Flibe is more powerful in moderating neutrons than Li, leading to a factor of 2–9 reduction in the volumetric heating rate (and thermal stresses) across the structured blanket, and (c) the fraction of the total breeding ratio, TBR, attributed only to the convective layer is ∼25% although the liquid layer is only ∼9% of the layer/blanket length.

Mechanical properties of Cu [sbnd]Cr [sbnd]Zr alloy and SS316 joints fabricated by friction welding method

Copper alloys with high-strength and high-conductivity are being considered for several magnetic fusion energy applications such as the first wall in high power-density devices, resistive magnetic coils, and high-heat flux components. For example, the stainless steel is a structural material while Cu-alloy acts as a heat sink material for the surface heat flux in the first wall. Therefore, development of reliable joints between Cu-alloys and stainless steel (SS316) is required. In the present work, joining tests on Cu—1%Cr—1%Zr/SS316 by friction welding were performed, and optimum fabricating conditions of the Cu-alloy/SS316 joint were determined. Additionally, the characteristics of tensile strength, hardness, metallographical observation and SEM/EPMA analyses on Cu—1%Cr—1%Zr/SS316 fabricated by friction welding were evaluated.

Advances in Electrode Materials Research

The technologies of primary (non-rechargeable) and secondary (rechargeable) lithium batteries have been developed in parallel to the developments in the microelectronics industry for about 20 years. The lithium batteries can be the lightest and most compact power sources when they are intended for portable equipment such as watches, calculators, cameras, cordless telephones, computers, and so on. During the past 10 years, the worldwide green revolution has requested a new, clear, and noiseless system of energy storage for replacing petrol. Rechargeable lithium batteries as high power and high energy density devices can also meet the requirements of clear and noiseless energy source, especially in the development of electric vehicles. Consequently, rechargeable lithium batteries with high power and long-life cycles have been very attractive to research groups all over the world. Thermodynamically, an electrochemical e.m.f, system is generated if an dectrolyte is sandwiched between two electrode materials with different chemical potentials. Electrodynamically, if a constant supply of ions can be maintained and transported through the electrolyte, this system will deliver current when connected across a load circuit. In the beginning of the research on rechargeable lithium batteries, a simple effect system has been studied. As a Li intercalation compound consists of a host (H) matrix into/from which x guest ions Li + may be inserted/extracted reversibly without a rearrangement of the host structure, a simple lithium battery may be represented as:

Characterization of laser-ablated boron nitride thin films on silicon

The ability to grow heteroepitaxial cubic boron nitride (cBN) films is the first step in the development of a process to grow electronic-grade, doped cBN films. This will eventually facilitate the development of cBN-based, high speed integrated circuits. Such a capability is critical to the development of ultra fast and high power density devices. Recent work is reported here on the characterization of BN thin films grown on 1 cm2 (100)Si substrates using a newly developed reactive laser ablation technique. The exact nature of the resulting films is highly process dependent and can yield any of the common BN crystal structures, i.e. cubic, hexagonal or wBN. This paper presents the results of Fourier transform IR spectroscopy, channelling and thermal wave analysis on various BN films resulting from that reactive laser ablation process. The results presented from channelling experiments on the cBN films show the heteroepitaxy of the cBN films. In those films, the (100) plane of the resulting heteroepitaxial cBN layer is parallel to the (100) plane of Si, with the (011) plane of the film parallel to the (001) plane of the Si substrate, i.e. a 45° rotation of the cBN lattice relative to the Si lattice. It is believed that the thermal diffusivity value reported here for the cBN thin film is the highest value measured for such films to date.