Phd Thesis Proposal 3 Years M - F - Effects Of Humidity on Power Electronics Materials And Components H/F L'Industrie recrute

Détail du poste

Overall context

Mitsubishi Electric R&D Centre Europe is the European R&D centre from the Corporate R&D organisation of Mitsubishi Electric. Situated at the heart of Europe's leading R&D community, Mitsubishi Electric R&D Centre Europe includes two entities, one located in Rennes, France and another located in Livingston, UK. We conduct R&D into next generation communication and information systems, power electronic systems and environment and energy systems.

A power converter is an electrical device for converting electrical energy. IT can convert alternating current (AC) into direct current (DC) and vice versa; change the voltage, frequency and current wave form of the electrical power or do some combination of these. Power electronic modules are elementary electronic components to realize the power conversion functions in the converters. In these components silicon IGBT or SiC MOSFET power semiconductor chips are connected to a heat dissipating substrate and encapsulated in a dielectric material which functions are : 1/ to provide electrical isolation against high voltage in the blocking mode; 2/ to protect the semiconductor chips against humidity, vibrations, dusts etc.

PhD Thesis supervisors :

Mitsubishi Electric R&D Centre Europe [MERCE] : Pierre-Yves PICHON, Senior Research Staff

IMS laboratory in Bordeaux : Loïc THEOLIER, Maître de Conférences HDR/ Associate Professor, and Alexandrine Guédon-Gracia, Maître de Conférences HDR/ Associate Professor

Problem description

The dielectric encapsulation materials can BE classified under two types : soft silicongels and hard epoxy resin-based materials with ceramic fillers. Temperature-humidity failure modes associated with silicongel-based designs include the electrochemical dissolution-precipitation of the electrode metals at the high electric field region near the semiconductor chip edge, resulting in isolation failure. For voltage ratings under 3.3kV the utilization of hard epoxy materials has enabled to significantly improve the power module designs in terms of heat dissipation, reliability against thermomechanical cyclic stresses and manufacturing simplicity. However, little is known about the effects of humidity diffusion on the reliability of these packages. In fact, compared to silicongels, the humidity diffusion coefficient is about 5 orders of magnitudes smaller, and the moisture saturation level about 2 orders of magnitude higher. Thus, due to the slower diffusion kinetics IT becomes challenging to test, model and predict the reliability of these packages against humidity-temperature exposure.

Objectives, methods and outputs

The objective of this PhD is to characterize and model the effects of humidity diffusion on materials and interfaces in hard epoxy-based encapsulation materials and power electronics components, by :

1/ defining and generating relevant test vehicles, planning and executing the humidity-temperature tests

2/ analysing the material and interfacial properties before and after humidity-temperature exposure using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), thermal analysis methods (DSC, TMA, TGA...), mechanical testing methods, and electrical testing method.

3/ identifying the main material and interfacial aging mechanisms and providing a physical understanding of the mechanisms of humidity diffusion in these materials, test vehicles and components

The output of this work will BE methods and models that can BE applied to a power module component for :
- The diffusion of moisture in materials/interfaces
- The effect of moisture on materials/interfaces aging

Detailed objectives / organization

This PhD work will BE a collaboration between IMS laboratory in Bordeaux (Pessac, FR) and Mitsubishi Electric R&D centre Europe (Rennes, FR). The PhD student will BE a MERCE employee, and the working time will BE shared between IMS laboratory (80%) and MERCE (20%). Main location will BE Bordeaux and stays at Rennes will BE business trips paid by the company.

In addition to the different research steps described in the Objectives, methods and outputs section, the candidate will entail the following tasks :

· Redaction of quarterly reports

· Redaction and publication of scientific papers

· Redaction of the thesis manuscript

· PhD defence

Prerequisites

For this PhD MERCE is looking for a highly motivated student with master's degree or higher education levels in the field of material science, chemistry and/or electronic materials experience. The student shall demonstrate experience and/or strong interest in developing skills in the following fields :
- Experimental methods : Planning, executing and critically analysing experimental tests
- Physical analytical methods : (if required) training on the above-mentioned techniques, planning the measurements, executing the measurement and interpreting the results considering the existing literature and student's knowledge in material science and chemistry.
- Modelling methods : review the relevant model the literature models and basic physical phenomena (diffusion, thermodynamics, interfacial kinetics). Select the models based on a trade-off between predictive accuracy, simplicity/calculation time and available methods.
- Organizational skills : project planning, synthetic reporting, organizing the data and communicating the results scientific communications (peer-reviewed publications and conference presentations)
- Language skills : English spoken / written

Duration : 3 Years - Period : from September/October 2025

Application

Thanks for providing us an application letter and your CV mentioning the reference HMTFT043