Électronique haute température -- Contraintes sur la puce et le packaging

Doctora

Silver sintering for power electronics integration

Silver sintering is an attractive alternative to soldering in power electronics, as it offers higher electrical and thermal performance. Furthermore, sintered attaches can operate at a higher temperature. In this paper, we investigate the use of silver sintering for the bonding of passive components, and for the manufacturing of so-called 3D-modules. It is shown that this technique is well suited, as it makes it possible to operate at very high temperature (up to 310 °C demonstrated), and as it simplifies the assembly process (several identical sintering steps can be performed successively without problem

Le Packaging en électronique de puissance

Le packaging, qui regroupe toutes les fonctions d’isolation, de connexion, de gestion thermique et de protection physique des puces à semiconducteur, a des effets majeurs sur leurs performances. Les éléments constitutifs d’un boîtier sont présentés dans le premier chapitre de ce mémoire, qui constitue un état de l’art du packaging de puissance. Les limites des solutions existantes sont exposées, que ce soit au niveau de leurs performances électriques, de leur fiabilité, ou de leur température maximale de fonctionnement.Dans le second chapitre, nous nous intéressons à des structures innovantes, destinées à dépasser les limites des solutions actuelles. En particulier, les solutions permettant de refroidir les puces de façon plus efficace (refroi-dissement « double face ») sont présentées en détails, en s’appuyant sur des prototypes réalisés au laboratoire.Le troisième chapitre présente les développements autour du packaging pour la haute température (température ambiante supérieure à 200 °C), qui a constitué le pricipal axe de mes travaux au laboratoire Ampère. Il débutepar une étude du comportement électro-thermique de composants en carbure de silicium, qui se révèlent adaptés au fonctionnement en haute température, mais nécessitent néanmoins une gestion thermique performante. La suite du chapitre est consacrée à l’étude de méthodes d’attache de puce alternatives aux brasures et permettant le fonctionnement à haute température. Deux méthodes sont identifiées (soudure en phase liquide transitoireet frittage d’argent), mais seule la seconde se révèle applicable aux puces actuelles.En plus des applications en haute température, la partie prospective du mémoire présente des possibilités de développement vers l’intégration en électronique de puissance, et vers le packaging pour la haute tension

Highly integrated power electronic converters using active devices embedded in printed-circuit board

International audienceIn this paper, we present a short overview of the power dies interconnects based on PCB technology, then we focus on embedding of power dies in the PCB material. In the second part of the article, we present in details the technology we developed to embed dies in PCB. Results show that the electrical performance of the die remains satisfying after embedding, but that dies with a copper topside metal layer are required for this process

Thermal Considerations of a Power Converter with Components Embedded in Printed Circuit Boards

International audiencePrinted-Circuit-Board (PCB) technology is attractive for power electronic systems as it offers a low manufacturing cost for mass production. Integration technologies such as device embedding have been developed to take advantage of the inter-layer space in multi-layer PCBs and to increase the performances (Electrical, Thermal). However, the PCB technology offers limited power dissipation due to the low thermal conductivity (≈0.3 W/(m·K)) of its composite substrate. In this paper, we consider PCB embedding for a 3.3 kW AC/DC bidirectional converter. We describe the integration of not only the power dies, but also the gate drive circuits and the power inductor, with a special focus on the thermal management. The manufacturing processes of the boards are presented. Two thermal models based on finite elements (FE) of this converter stage are introduced. The accuracy of these models is validated against experiments. The results show that a simplified FE model offers satisfying accuracy and fast simulation, even considering the relatively complex structure and layout of the PCBs

Evaluation of the PCB-embedding technology for a 3.3 kW converter

International audienceThis paper presents a converter fully made using PCB embedding technology (including the semiconductor devices , but also their gate driver circuits as well as the passive components). This converter is rated at a high-power (3.3 kW) considering the PCB technology. Here, the focus is given to the experimental validation of the embedding process, with the characterization of many of the embedded devices (SiC MOS-FETs, diodes, capacitors). These results show that most of the components were unaffected by the process, with the noticeable exception of the large inductors which exhibit variations in the inductance values as well as a large ac resistance. Finally, the converter is successfully assembled an tested at low power

Sintered-silver bonding of high-temperature piezoelectric ceramic sensors

Silver sintering is used to bond five components together, in order to form a piezoelectric sensor. A description is provided of the preparation of these components, and of the manufacturing steps, which are carried out at a low temperature (280 °C). The resulting sensor assemblies are then characterized: cross-sectional views show that the silver layer has a very dense struc-ture, with less than 1 % porosity, although further focused-ion beam investigations show that this porosity is closer to 15 %. The shear strength is approximately 30 MPa. The Young's modulus of the silver bondline is measured using nanoindentation, and is found to be comparable with that of bulk silver (56.6 GPa). Finally, a silver-sintered sensor is compared with a sensor bonded using conventional techniques, showing that an improvement in sensitivity by a factor of more than 3 is achieved

Modeling, Fabrication, and Characterization of Planar Inductors on YIG Substrates

International audienceThis paper presents the design, fabrication, and characterization of micro planar inductors on a microwave magnetic material (YIG). Planar spiral inductors were designed for monolithic DC-DC converters in System-In-Package with 100 MHz switching frequency (1 W, Vin= 3.6 V, Vout= 1 V). A microwave magnetic substrate (YIG) serves as mechanical support, and also presents a double purpose by increasing inductance value and reducing electromagnetic interferences (EMI). This last point is critical to improve the behavior of a switching mode power supply (SMPS). In order to obtain an optimal design for the inductor, geometrical parameters were studied using Flux2D simulator and an optimized 30 to 40 nH spiral inductor with expected 25 mΩ RDC, 3 mm2 footprint area was designed. Subsequently, samples have been fabricated by electroplating technique, and tested using a vector network analyzer in the 10 MHz to 100 MHz frequency range. Results were then compared to the predicted response of simulated equivalent model

Design of a Low-Capacitance Planar Transformer for a 4 kW/500 kHz DAB Converter

International audienceIncreasing electrification in transport sectors, from automotive to aerospace, highlights the need for low size and high power density components. The recent advent of planar technology theoretically allows to reduce considerably the size of the magnetic components. This article focuses on the design of a high frequency planar transformer intended to be used in a 4 kW 500 kHz DAB converter. In particular, the inter-winding capacitances are assessed, as they have a strong influence on the behaviour of the DAB, and in some extreme cases may impede operation entirely. Analytical and finite element models are used to evaluate the stray elements of the transformer (resistance of the conductors, inter-winding capacitance and leakage inductance), and the resulting circuit model is compared with experimental measurements. This work focuses on influences of design parameters on the transformer stray elements

Bonding strength of multiple SiC die attachment prepared by sintering of Ag nanoparticles

3 mm × 3 mm dummy SiC dies with 100\200\200 nm thick Ti\W\Au metallization have simultaneously been attached using sintering of Ag nanoparticle paste on AlN-based direct bonded copper substrates with 5\0.1 μm thick NiP\Au finish. The effect of preparation and sintering parameters including time of drying the printed paste, sintering temperature and time, and pressure, on the average shear strength for multiple die attachments was investigated. The surfaces of the die attachments after the shear tests were observed and the individual shear strength values correlated with the “apparent” porosity and thicknesses of the corresponding die attachments (sintered layer). The results obtained are further discussed and compared with typical data reported in existing literature. Main conclusions include: (i) the present shear strength values and their variations are comparable with those reported for single die attachment samples, (ii) the effects of sintering parameters can be ascribed to the effectiveness of the organic content burnout and appropriate rate of growth and coalescence of the Ag nanoparticles during the sintering process, and (iii) thickness values of the sintered Ag die attachments may be taken as non-destructive measurements to monitor/evaluate the quality of die attachment during power electronic module manufacturing/assembly process