Charles Joubert

Bio: Charles Joubert is an academic researcher from University of Lyon. The author has contributed to research in topics: Electronics & Power electronics. The author has an hindex of 4, co-authored 9 publications receiving 319 citations.

State of the art of high temperature power electronics

Abstract: High temperature power electronics has become possible with the recent availability of silicon carbide devices. This material, as other wide-bandgap semiconductors, can operate at temperatures above 500 °C, whereas silicon is limited to 150-200 °C. Applications such as transportation or a deep oil and gas wells drilling can benefit. A few converters operating above 200 °C have been demonstrated, but work is still ongoing to design and build a power system able to operate in harsh environment (high temperature and deep thermal cycling).

Gate Oxide Degradation of SiC MOSFET in Switching Conditions

Abstract: Under realistic switching conditions, SiC MOSFETs reliability issues remain as a challenge that requires further investigation. In this letter, a specific aging test has been developed to monitor and characterize the electrical parameters of the SiC MOSFET. This allows estimations of the health state and predictions of the remaining lifetime prior to its failure. The gate leakage current seems to be a relevant runaway parameter just before failure. This leakage indicates deterioration of the gate structure. This hypothesis has been validated through analysis of scanning electron microscopy pictures, with a focused ion beam cut showing cracks within the polysilicon.

State of the art of High Temperature Power Electronics

Abstract: High temperature power electronics has become possible with the recent availability of siliconcarbide devices. This material, as other wide-bandgap semiconductors, can operate at tempera-turesabove500°C,whereassiliconislimitedto150-200°C.Applicationssuchastransportationor a deep oil and gas wells drilling can benet. A few converters operating above 200°C havebeen demonstrated, but work is still ongoing to design and build a power system able to operatein harsh environment (high temperature and deep thermal cycling). 1 Introduction The rst part of this paper will describe some of the most prominent applications for hightemperature power electronics. This is where high temperature-capable converters are enablerfor new solutions, such as electrical actuators for jet engine.The second part will give a short explanation on why wide-bandgap semiconductors areneeded for high-temperature electronics, and why, among them, silicon carbide has been cho-sen.Finally, we will see that a lot of work is still required to design a complete power converter(this include passive components, packaging, control circuits in addition to the active powerdevices).

Micro-Fabrication of Planar Inductors for High Frequency DC-DC Power Converters

Abstract: The inductors are essential elements for radiofrequency (RF) integrated circuits. A large number of communication devices functioning in RF such as mobile phones or wireless ethernet require transceivers, filters and power amplifiers in which inductors are critical components. Recently, the push toward miniaturisation of electronic components enabled to embark more and more portable equipments and accessories of high energy consumption. Embedded systems used in these devices are facing energy shortage that leads designers to spread power electronic converters to achieve dynamic voltage and frequency scaling [Zhao]. Wherever it is possible, the linear low-drop converter is replaced by inductive DCDC converters and/or capacitive DC-DC converters in order to improve the whole efficiency of the system. Since then the demand on power converters for portable electronic devices has attracted great interest [Sugawara]. Efficiency and footprint (or volume) are the main design criteria to ensure respectively a large operating range and a smaller device. These applications use switching mode power supply (SMPS) or inductive DC-DC converter which typically require the following characteristics: 1 W, VIN=3.6 V, VOUT=1 V, IOUT=1 A. Passive components fill a significant part of the chip area occupied by power converters, even when the components are optimized for minimum area. Thus, for this power range, System-In-Package (Fig. 1) is more appropriate than monolithic integration (also named System-On-Chip).

Electrolytic capacitor: Properties and operation

Abstract: Due to their high specific volumetric capacitance, electrolytic capacitors are used in many fields of power electronics, mainly for filtering and energy storage functions. Their characteristics change strongly with frequency, temperature and aging time. Electrolytic capacitors are among the components whose lifetime has the greatest influence on the reliability of electrical systems. Over the past three decades, many efforts in academic research have been devoted to improving reliability capacitor. Industrial applications require more reliable power electronic products. It is in this context that the different electrolytic capacitors and their characteristics are discussed. The aging process of aluminum electrolytic capacitors is explained. Finally, this paper reviews existing methods of failure prognosis of electrolytic capacitors.

Survey of High-Temperature Reliability of Power Electronics Packaging Components

Abstract: In order to take the full advantage of the high-temperature SiC and GaN operating devices, package materials able to withstand high-temperature storage and large thermal cycles have been investigated. The temperature under consideration here are higher than 200 °C. Such temperatures are required for several potential applications such as down-hole oil and gas industry for well logging, aircrafts, automotive, and space exploration. This review focuses on the reliability of a selection of potential components or materials used in the package assembly as the substrates, the die attaches, the interconnections, and the encapsulation materials. It reveals that, substrates with low coefficient of thermal expansion (CTE) conductors or with higher fracture resistant ceramics are potential candidates for high temperatures. Die attaches and interconnections reliable solutions are also available with the use of compatible metallization schemes. At this level, the reliability can also be improved by reducing the CTE mismatch between assembled materials. The encapsulation remains the most limiting packaging component since hard materials present thermomechanical reliability issues, while soft materials have low degradation temperatures. The review allows identifying reliable components and materials for high-temperature wide bandgap semiconductors and is expected to be very useful for researchers working for the development on high-temperature electronics.

Are Sintered Silver Joints Ready for Use as Interconnect Material in Microelectronic Packaging

Abstract: Silver (Ag) has been under development for use as interconnect material for power electronics packaging since the late 1980s. Despite its long development history, high thermal and electrical conductivities, and lead-free composition, sintered Ag technology has limited market penetration. This review sets out to explore what is required to make this technology more viable. This review also covers the origin of sintered Ag, the different types and application methods of sintered Ag pastes and laminates, and the long-term reliability of sintered Ag joints. Sintered Ag pastes are classified according to whether pressure is required for sintering and further classified according to their filler sizes. This review discusses the main methods of applying Ag pastes/laminates as die-attach materials and the related processing conditions. The long-term reliability of sintered Ag joints depends on the density of the sintered joint, selection of metallization or plating schemes, types of substrates, substrate roughness, formulation of Ag pastes/laminates, joint configurations (i.e., joint thicknesses and die sizes), and testing conditions. This paper identifies four challenges that must be overcome for the proliferation of sintered Ag technology: changes in materials formulation, the successful navigation of the complex patent landscape, the availability of production and inspection equipment, and the health concerns of Ag nanoparticles. This paper is expected to be useful to materials suppliers and semiconductor companies that are considering this technology for their future packages.

Wide-bandgap semiconductor materials: For their full bloom†

Abstract: Wide-bandgap semiconductors are expected to be applied to solid-state lighting and power devices, supporting a future energy-saving society. While GaN-based white LEDs have rapidly become widespread in the lighting industry, SiC- and GaN-based power devices have not yet achieved their popular use, like GaN-based white LEDs for lighting, despite having reached the practical phase. What are the issues to be addressed for such power devices? In addition, other wide-bandgap semiconductors such as diamond and oxides are attracting focusing interest due to their promising functions especially for power-device applications. There, however, should be many unknown phenomena and problems in their defect, surface, and interface properties, which must be addressed to fully exploit their functions. In this review, issues of wide-bandgap semiconductors to be addressed in their basic properties are examined toward their ?full bloom?.

High temperature electrical energy storage: advances, challenges, and frontiers

Abstract: With the ongoing global effort to reduce greenhouse gas emission and dependence on oil, electrical energy storage (EES) devices such as Li-ion batteries and supercapacitors have become ubiquitous. Today, EES devices are entering the broader energy use arena and playing key roles in energy storage, transfer, and delivery within, for example, electric vehicles, large-scale grid storage, and sensors located in harsh environmental conditions, where performance at temperatures greater than 25 °C are required. The safety and high temperature durability are as critical or more so than other essential characteristics (e.g., capacity, energy and power density) for safe power output and long lifespan. Consequently, significant efforts are underway to design, fabricate, and evaluate EES devices along with characterization of device performance limitations such as thermal runaway and aging. Energy storage under extreme conditions is limited by the material properties of electrolytes, electrodes, and their synergetic interactions, and thus significant opportunities exist for chemical advancements and technological improvements. In this review, we present a comprehensive analysis of different applications associated with high temperature use (40–200 °C), recent advances in the development of reformulated or novel materials (including ionic liquids, solid polymer electrolytes, ceramics, and Si, LiFePO4, and LiMn2O4 electrodes) with high thermal stability, and their demonstrative use in EES devices. Finally, we present a critical overview of the limitations of current high temperature systems and evaluate the future outlook of high temperature batteries with well-controlled safety, high energy/power density, and operation over a wide temperature range.