Hybrid integration

This research activity was born in the 90s following the rapid development of IGBT power modules. This development necessitated to study tools for better implementation of semiconductor devices, taking into account the impact of parasitic elements, thermal management and voltage withstand. With the development of SiC and GaN wide-band-gap components, which switch faster and have a smaller surface area, needs have increased still further.
The research group is currently involved in various projects concerning the impact of power modules on EMC issues, voltage withstand and thermal management. It also works on new concepts about modular packaging.
The persons involved in this research topic are Rachelle Hanna, Pierre-Olivier Jeannin, Jean-Luc Schanen and Yvan Avenas, accompanied by their PhD students, post-docs and interns. .

This topic was born in the laboratory in the 90s. It was first applied to silicon IGBT and MOSFET modules. It benefited greatly from the contribution of the InCa software. This led to the development of original concepts such as PCoC (Power Chip on Chip), as well as optimization methods for the placement of power components in more conventional (2D) modules. Since the middle of the 2000-2010 decade, the advent of wide-band-gap components (GaN, SiC and diamond) in power electronics has greatly increased the design constraints on power assemblies, with the aim of limiting overvoltages across power devices and keeping common-mode currents to a minimum, while exploiting wide-band-gap components to the maximum of their switching speed.
This has led to original packaging aspects to reduce parasitic inductances (in the power and in the gate circuits) and control parasitic capacitors. Controlling parasitic capacitors is essential to limit the common-mode currents generated by high dv/dt.
This work has been carried out in collaboration with industrial groups as part of CIFRE theses (Thales, Mitsubishi, Alstom, Vedecom) and also as part of academic cooperation projects (ANR, PEPR) or academic and industrial projects (MeGaN Program, IRT PowerGan).
This work is currently being pursued through the use of vertical GaN components as part of the VERTIGO project of the PEPR Electronics program.
To carry out this work, we have an EMC measurement platform and a platform with electronic component assembly facilities (CEDMS).

Above, an example of a power module integrating eight SiC MOSFETs (bare chips) and decoupling capacitors in a multilayer printed circuit, designed at G2Elab.

Research works on thermal management of power modules began in the 90s, initially involving single-phase liquid cooling with microchannels. Together with Alstom and CEA-LETI, G2Elab was a pioneer in double-sided cooling power modules. Subsequently, through numerous collaborations, the laboratory took a particular interest in the integration of miniature heat pipes and the use of unconventional cooling fluids, particularly liquid metals and ferrofluids.
We have also been very active in works related to the use of thermosensitive parameters for thermal characterization of power modules. We now have extensive know-how in this field, enabling us to choose the right thermosensitive parameter for the right application. This has enabled us, for example, to characterize thermo-compressed die attaches during the ANR CopperPack project, or to evaluate cooling solutions incorporating PCMs (Phase Change Materials) as part of the NEPTUNE project funded by France Relance.
Several  projects are currently underway in this area. As part of a CIFRE thesis with SAFRAN-Tech, we are studying how to improve the module's internal thermal resistance by using materials with high thermal conductivity. We are also studying two-phase immersion cooling of power semiconductor components in collaboration with the SIMaP laboratory (MOSAIC project of the Institut Carnot Energies du Futur, CDP PowerAlps project).
To carry out this work, we have a platform including several thermal-hydraulic loops and an instrumented enclosure for characterizing two-phase immersion cooling. For junction temperature measurement, we have an industrial measurement system (Analysis Tech's Phase12B) and in-house devices.

The proposed modular packaging is based on the use of an elementary system consisting of a semiconductor device cooled on their both sides (see figure below). This element can be connected in series or in parallel with other elements to create a converter structure. The figure shows, for example, how to build a switching cell with low parasitic inductance including a decoupling capacitor. The concept was developed during a technology maturation project funded by SATT Linksium.
The development of modularity not only simplifies the design of converters, but also makes it possible to manufacture power modules that can be disassembled more easily, offering attractive thermal performances and parasitic elements adapted to high-switching-speed devices. The management of voltage withstand is an important issue that needs to be studied.
Several projects are currently underway in this topic. In a thesis in collaboration with the CEA, we are studying the implementation of modular, dismountable packaging based on the use of vertical switching cells. Cooling is provided by an insulating liquid. At the same time, we are working on air-cooled modular and dismountable packaging based on lateral switching cells as part of the TAPIR (Pack Ambition Recherche funded by the Auvergne-Rhône-Alpes region) and DESTINI (ANR, collaboration with the Ampère, SATIE and Laplace laboratories) projects.
 

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