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The study of the impact of junction temperature swings ("Tj) on degradation mechanisms during power cycling tests (PCTs) requires both a control of the applied thermal stress and a separation of degradation modes. The first requirement can be obtained by using a "constant "Tj" power cycling strategy that allows to minimize the cross-interactions between the influencing factors. The second one is made by using a dedicated power module well-suited for targeting only the chips top-side degradations (metallization and bond wire contacts). In this paper, a constant "Tj strategy by gate voltage regulation is performed for power cycling tests in DC-mode. The tested modules are ideally designed for top-metal and bond-wire contacts degradation investigations. From ageing indicator on the collector-emitter voltage (VCE), the results clearly show that three regimes of degradation occur systematically at the IGBT chips top-side, whatever the stress conditions. Moreover, comparative results in 'constant "Tj' and conventional 'constant "I' PCT strategies have shown that the feedback between stresses and damages encountered in the second strategy is more important for low "Tj values than for high "Tj values. In addition, results show that in case of high stresses, the 'constant "Tj' strategy with Vge regulation, gives values close to a 'constant "I' strategy but that the extrapolation towards low values of "Tj can be questionable for the 'constant "Tj' strategy.

Unintentional impurities like oxygen introduced into the undoped AlGaN barrier may present an important traps source for these devices besides Al2O3/AlGaN interface traps. Here, we present a theoretical study of the charges weight between oxygen traps in barrier layer and Al2O3/AlGaN interface traps on the 2DEG density for different gate bias. In order to conduct this study, a semi-analytical 1D charge model has been developed and used based on the nonlinear Poisson and Schrödinger coupled equations. The model is based on a new analytical expression of the electric field distribution under the gate including the ionized oxygen profile into the AlGaN barrier. A secondary ion mass spectrometry and deep-level transient spectroscopy measurements on a fabricated device were performed. A mean density of oxygen up to 2×1018 cm3 was measured into the AlGaN barrier, associated with an activation energy of 0.44eV and a cross section of 1.4 ×1014 cm2. Using these values as the model inputs, the theoretical results showed that even with changing the balance between the interface states density and the barrier traps density, there is no an absolute traps domination either from the barrier or the interface traps and their impact weight on the 2DEG density changes with the gate bias.

PCIM Europe 2017, Nuremberg, ALLEMAGNE, 16-/05/2017 - 18/05/2017; In this paper, we develop an analytical electro-thermal model for a power module with multiple heat sources. This model is applied on a motor drive power converter mounted on its air-cooled heatsink. It offers fast calculations of the junction temperature, taking into account the self-heating and the cross coupling effect. The calculations are based on averaged power losses obtained from the expression of the duty cycle, and analytical expressions of the system thermal impedances, which are measured by fast optical fiber temperature sensors. The model results are finally validated based on experimental measurements, which are carried out on a motor test set up at one operating point of the power converter, when the THI-PWM switching technique is used.

International audience; This study aims to assess the reliability of smart converters for applications using 24 V batteries. It compares degradation effects and lifetime durations for similar dissipated energies when these smart power switches are subjected to normal and extreme protection test conditions. Three experimental ageing tests have been performed: (i) ageing tests under normal protection mode, (ii) ageing tests under repetitive inductive avalanche switching and (iii) ageing tests under repetitive short-circuit. Evolution of several electrical parameters such as on-state resistance; threshold voltage and saturation current have been monitored. Tested devices under normal condition and under repetitive inductive avalanche have failed after about the same number of cycles with the same dissipated energy. However, several results show a significant decrease of the lifetime under repetitive short-circuit tests for a similar dissipated energy.

EPE 13 - European Conference on Power Electronics and Applications, Lille, FRANCE, 03-/09/2013 - 05/09/2013; The reliability of power electronic modules is of utmost importance all the more so since they would be exposed to high ambient temperatures and frequent power cycling. Aging tests at 200°C have been done using power cycling in order to study some packaging materials for high temperature power electronics. Junction temperature swings were performed between 196°C and 245°C and tests have concerned the die attach, wire bond and die metallization materials. Experimental results have shown that AuGe solder material is highly resistant comparatively to a high leaded material. Furthermore, for die top-metal/wire couple, gold material exhibits a better performance compared to Aluminum.

The reliability of power electronic modules is of utmost importance all the more so since they would be exposed to high ambient temperatures and frequent power cycling. Aging tests at 200°C have been done using power cycling in order to study some packaging materials for high temperature power electronics. Junction temperature swings were performed between 196°C and 245°C and tests have concerned the die attach, wire bond and die metallization materials. Experimental results have shown that AuGe solder material is highly resistant comparatively to a high leaded material. Furthermore, for die top-metal/wire couple, gold material exhibits a better performance compared to Aluminum.

Due to new applicative domains like embedded systems, power electronic converters are getting more and more compact, increasing their power densities and working in extreme environments with higher lifetime requirements in accordance with design to cost optimization. Power components packaging is thus involved in many research considerations such as thermal management, electromagnetic interference reduction and reliability. The thermal characterization of the die assembly is becoming a challenge in a power module due to the inaccessibility of the semiconductor parts in the module. This paper describes an innovative experimental method used to evaluate power chip interconnection solutions with the help of a transient thermal response of a power component. The experimental setup is designed to derive the thermal impedance of a power device in the microsecond scale in order to evaluate the thermal behaviour of the physical layers close to the chip. The method is then carried out with power diodes in order to compare the thermal impedance of two power modules having different solder voids repartitions. The results show that this method has a very good sensibility that can be used to compare the quality of the thermal behaviour of different die attaches.

The paper describes accelerated DC and PWM power cycling tests. It presents basic principle of such ageing tests. The required conditions for accelerated testing are discussed and the lifetime prediction method with the main usual difficulties for such ageing tests is detailed. It also focuses on problems caused by introduction of wide band gap power chips in power modules due to the higher operating temperature and power density that are allowed by these devices. Power cycling tests, wide band gap power modules, thermo sensitive electrical parameters

International audience; This paper deals with performances and reliability aspects of MOSFET and JFET power transistors devices based on silicon carbide technology. The purpose of this article is to evaluate the abilities and effects of each technology on the conception of power converter for avionic applications. Experimental measurements of steady-on-state resistance dependence and transient performances with temperature are presented and discussed. The second section focuses mainly on robustness aspects of the two types of power transistors in order to analyze their capability to withstand with aeronautic harsh environmental constrains

This paper deals with performances and reliability aspects of MOSFET and JFET power transistors devices based on silicon carbide technology. The purpose of this article is to evaluate the abilities and effects of each technology on the conception of power converter for avionic applications. Experimental measurements of steady-on-state resistance dependence and transient performances with temperature are presented and discussed. The second section focuses mainly on robustness aspects of the two types of power transistors in order to analyze their capability to withstand with aeronautic harsh environmental constrains.

ECCE 2011 - IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, PHOENIX, ETATS-UNIS, 17-/09/2011 - 22/09/2011; Electronic package try to be always more compact and cheaper leading to increase current and power densities into the module. These improvements are achieved throuhgh the development of new structures and new interconnection methods. Today there are no efficient experimental tools able to measure thermal and electrical resistance of all these structures. Facing theses difficulties, we propose to design and create an innovative vertical thermal test diode (VTTC) containing an array of 13 poly-silicon temperature and voltage sensors. These sensors are located inside the top metallization in order to better suite power chip purposes. Compared to existing thermal test chip (TTC), the device we are offering is a real power semi-conductor device that maps the surface temperature and voltage profiles during static usage. Thanks to its unique and wide front side surface adapted for soldering, bumping or bonding, the TTC described in the paper can also be implemented in 3D packages.

EPF 2010 - 10th European Power Electronics Conference, St Nazaire, FRANCE, 30-/06/2010 - 02/07/2010; Cet article présente des travaux de caractérisations thermiques statiques d'un ensemble d'interfaces thermiques. Ces dernières sont utilisées pour la gestion thermique en électronique de puissance. Ces caractérisations sont basées sur la norme ASTM D5470. L'objectif est d'extraire la conductivité thermique pour caractériser le vieillissement des interfaces. Des caractérisations transitoires complémentaires seront présentées en perspectives afin de voir si une analyse transitoire pourrait permettre de caractériser leur vieillissement à travers la capacité thermique volumique.

International audience; This paper presents results showing the robustness of different SiC JFET transistors from SiCED in current limitation regime or short-circuit operation. Crystal temperature during failure was estimated after different electrical characterizations and using appropriate models of saturation current which is used as a thermal indicator. This work shows the exceptional robustness of SiC JFET transistors in current limitation mode compared to Si devices (MOSFETS and IGBTs).

(ITCT 2006 - Journées internationales d'études Ingénieries des Technologies Communes aux Transports terrestres, maritimes, aériens et spatiaux, Paris, FRANCE, 20-/11/2006 - 23/11/2006; La thématique de recherche abordée dans cet article est motivée par l'utilisation croissante de l'électricité dans le domaine des transports, avec la recherche d'une réduction de la consommation d'énergie et de l'émission des gaz polluants. Cette mutation conduit au développement de systèmes complexes, assemblages de briques fonctionnelles permettant l'optimisation de la gestion de l'énergie électrique embarquée, avec des spécifications sévères en termes de fiabilité et de durée de vie. Avant de nous focaliser sur les difficultés liées à l'intégration des dispositifs de conversion d'énergie électrique dans des environnements de plus en plus sévères, nous tenterons de faire une présentation générale de la problématique posée. Finalement, et après avoir exposé les objectifs et la méthodologie employée, nous présenterons une étude cherchant à évaluer le comportement de différents substrats céramiques utilisés pour la réalisation de modules de puissance adaptés à la haute température et soumis à des cycles de température de grande amplitude. Cet article montre ainsi les principaux modes de défaillances rencontrés, et expose les principaux facteurs qui peuvent permettre une amélioration la durée de vie des assemblages de puissance dans des environnements thermiques extrêmement sévères.

SAAEI-EPF 2004 - Annual seminar on automatic control, industrial electronics and instrumentation, Electronique de puissance du futur, Toulouse, FRANCE, 15-/09/2004 - 17/09/2004; Cet article présente la réalisation d'un véhicule de test (module de puissance) développé pour étudier la faisabilité d'un convertisseur dédié à des températures de fonctionnement élevées pour des applications avioniques. Le module, réalisé par la société APT Europe, sera présenté en détail. Le choix des matériaux d'assemblage ainsi que celui des composants actifs sont présentés et discutés. En particulier, l'utilisation de diodes Schottky sic et transistors coolmos est justifiée à travers les caractérisations électriques et leurs comportements jusqu'à des températures de 200°c.

PCIM 2004 - International conference power electronics, intelligent motion, power quality, Nuremberg, ALLEMAGNE, 25-/05/2004 - 27/05/2004; In avionic applications, a growing demand for devices being capable of operating at high temperatures is developing. In these applications, semiconductor devices are placed on the engine, in very harsh operating conditions with an ambient temperature which could reach about 200°c. The paper will present the realisation of test vehicles (power modules) dedicated to avionic applications in high temperature applications. The paper will also present electrical characterisation of semiconductor devices in high temperature operations in order to justify the choice of silicon carbibe schottky diodes and coolmos tansistors. The high temperature power module realised by apt europe will be presented in detail.

This article discusses a high-temperature active cycling bench developed for aging the joint between the DCB substrate and the IGBT component base. It outlines the protocol used for indirect measurement of average junction temperature, and gives details on temperature regulation, electrical signal acquisition and test circuit performance. We also set out initial results from long-duration active cycling under harsh operating conditions, with a base temperature of 90°C and power injection of 300 W/cm 2., Cet article donnera une présentation détaillée d'un banc de cyclage actif à haute température développé pour vieillir la brasure située entre le substrat DCB et la semelle de composants IGBTs. Le protocole de mesure indirecte de la température moyenne de la jonction, la régulation de la température de la semelle, l'acquisition de l'ensemble des signaux électriques et les performances du circuit de test seront présentés et discutés. Le document décrit également les premiers résultats issus d'un cyclage actif de longue durée. Les conditions de fonctionnement sévères sont définies par une température de semelle de 90°C et une injection de puissance de 300W/cm².

This work is part of the research for lead-free die-attach solutions for power modules to offer a solution to the European directive RoHS, which banishes lead in electrical and electronic equipments. The intrinsic silver properties and the previous work published helped us choose silver sintering as the die-attach technology to be tested and evaluated in our work. After a state of the art on power module structure, on different die-attach technologies and on power module reliability, various works have been carried out in collaboration with the FIDEA and ASPEEC projects. Through experimental tests and finite element modeling analysis (FEM), die-attach processes have been defined, thermal and mechanical characterizations and reliability assessment of silver sintered power modules have been done. Finally, a silver sintered rectifier bridge double side assembly with higher thermomechanical properties than a lead-solder die-attach assembly was developed as final prototype., Ces travaux s'intègrent dans la recherche de solutions alternatives aux alliages de brasure pour les assemblages de puissance. De par les propriétés intrinsèques de l'argent et les premiers travaux publiés, le frittage de pâte d'argent a été sélectionné comme technique d'assemblage pour être étudiée et évaluée. Après avoir effectué un état de l'art sur la structure d'un module de puissance, sur les différentes techniques d'assemblage, la fiabilité des assemblages et le frittage, différents essais ont été menés en partenariat avec les projets FIDEA et ASPEEC. Ils nous ont permis de définir des procédés d'assemblages, de caractériser thermiquement et mécaniquement les assemblages frittés et d'évaluer la fiabilité de ces assemblages par des essais expérimentaux et des simulations numériques. Ces travaux nous ont permis au final de réaliser un prototype d'assemblage double face fonctionnel aux propriétés thermomécaniques supérieures à celles d'un assemblage brasé.

On board electric vehicles (EVs) and hybrid (HEV), the functions of traction is provided by power electronic converters. These consist of power modules (IGBT or MOSFET). During their operation, these modules are sometimes subjected to high electrical and thermal stresses that lead to failure or even destruction.The first objective will be to achieve experimental bench to study ageing IGBT modules under extreme operating conditions ( short circuit mode). Thus, we evaluate the various indicators of ageing to predict component failure. Topics will also follow the ageing or degradation initiated on IGBT components by infrared thermography. The second objective is to model and simulate by finite element different IGBT structures to validate the models in static and dynamic operation. The advantage of multicellular approach to the single cell approach will be highlighted., A bord des véhicules électriques (VE) et Hybrides (VEH), les fonctions de tractions sont assurées par des convertisseurs électroniques de puissances. Ces derniers sont constitués de module de puissance (IGBTs ou MOSFETs). Au cours de leur fonctionnement, ces modules sont parfois soumis à de fortes contraintes électriques et thermiques qui amènent à une défaillance ou même à une destruction. Le premier objectif sera de réaliser un banc expérimentale permettant d'étudier le vieillissement des modules IGBTs en régîmes extrêmes de fonctionnement (mode de court-circuit). Ainsi, nous évaluerons les différents indicateurs de vieillissements permettant de prédire la défaillance du composant. Il sera question aussi de suivre le vieillissement ou une dégradation initié sur les composants IGBTs par thermographie infrarouge. Le second objectif sera de modéliser et simuler par éléments finis différentes structures d'IGBTs, afin de valider les modèles en fonctionnement statique et dynamique. L'avantage de l'approche multicellulaire par rapport à l'approche unicellulaire sera mis en avant.

Today’s main challenge for aeronautical equipment manufacturers is to respond to the more electrical aircraft regulations. Moreover, there are many applications in aircraft area where high temperature technologies are needed. Nowadays, the replacement of hydraulic systems for electric ones leads to place the power inverters in a harsh environment, for example in the engine nacelle. The equipment is under high constraints such as high and low temperatures, wide temperature cycling, high humidity and low pressure. Combined to these environmental constraints, the new aircraft system is submitted to weight and operating cost reduction. As a consequence, efforts shall be done to reduce weight and volume of the power converter without losing its performance. To reach such a goal, the design of the converter must enable a high level of integration, efficiency and reliability. In particular, fatigue damage has a significant influence on such modules electrical power performance. And fatigue-related performance testing remains a costly endeavor for aeronautical equipment. A finite number of destructive tests can be carried out in specific facilities for a fairly low number of configurations. The purpose of these destructive tests is to investigate the failure modes appearing regarding this accelerated ageing. Therefore numerical simulations have been envisaged since non-destructive, easily evolving and usable for a high number of configurations, though needing data from experimental assays. In this study, we propose a method dealing with the main constraints for such equipment, i.e. electrical, thermal and mechanical simulation. Those three physical problems have different characteristic time and are strongly coupled with a non-trivial behavior. To optimize the resources usage and have a relevant representation of the problem, a 1D electrical / 3D thermal / 3D mechanical coupled method has been implemented over a co-simulation bus. Different time steps, different abstraction levels and different skills are used to provide predictions of the multiphysical fatigue behavior of power modules., Le principal défi auquel sont confrontés aujourd'hui les équipementiers aéronautiques est d'augmenter l'utilisation des systèmes électriques à bord de l'avion. De nos jours, le remplacement des systèmes hydrauliques par des actionneurs électriques conduit à placer les systèmes électriques dans un environnement hostile, par exemple dans la nacelle du moteur. L'équipement est soumis à des contraintes sévères telles que des températures élevées et basses, un cycle thermique étendu, une humidité élevée et une basse pression. En conséquence, des efforts doivent être faits pour réduire le poids et le volume du convertisseur de puissance sans perdre ses performances. Pour atteindre cet objectif, la conception de modules de puissance doit permettre un haut niveau d'intégration, d'efficacité et de fiabilité. On s’intéresse en particulier aux dommages causés par la fatigue qui ont une influence significative sur les performances électriques de ces modules. Les tests de performance liés à la fatigue restent des efforts coûteux pour l'équipement aéronautique. Un nombre fini de tests destructifs, par vieillissement accéléré, peut être effectué pour un nombre assez faible de configurations. Le but de ces tests est d'étudier les modes de défaillance apparaissant lors du vieillissement accéléré. Par conséquent, des simulations numériques ont été envisagées, facilement évolutives et utilisables pour un grand nombre de configurations, mais nécessitant des données d'essais expérimentaux. Dans ce manuscrit, quelques modes de défaillances sont étudiés. On propose une méthode numérique intégrant les contraintes principales dans les équipements, à savoir la simulation électrique, thermique et mécanique. Ces trois problèmes physiques ont des temps caractéristiques différents et sont fortement couplés avec un comportement non trivial. Pour optimiser l'utilisation des ressources et avoir une représentation pertinente du problème, un procédé couplé électrique 1D / thermique 3D / mécanique 3D a été implémenté sur un bus de cosimulation. Différents pas de temps, différents niveaux d'abstraction et différentes compétences sont utilisés pour fournir un modèle multiphysique de modules de puissance.