Contribution à l'étude de la durée de vie des assemblages de puissance dans des environnements haute température et avec des cycles thermiques de grande amplitude

In avionic applications, semiconductor devices can be placed on the engine with an ambient temperature about 200°C and thermal cycling from -55°C to 200°C in the worst case. The first part of this study presents the electric characterizations of semiconductor components, in order to justify the choice of SiC Schottky diodes and Si CoolMOS transistor for high temperature applications. Then, these components are integrated in a test vehicle (power module) adapted to its localization on the engine. The objective is to evaluate the electrical performances of the active elements at high temperature, and the brazing assembly technology with the ceramic substrates on an AlSiC baseplate. In complement of an experimental campaign with a thermal cycling of great amplitude, numerical thermo-mechanical simulations of the assembly allow to understand the origin of the failures and to improve the lifetime of power module under such severe operating conditions. In order to find solution of integration, the last part of this study presents experimental results, carried out under such severe conditions, for new test vehicles without active element, including different technological ceramic substrates. They include various ceramic materials soldered on AlSiC base plate, DCB with AlN and Al2O3 ceramic substrates with and without dimples and different copper thickness, and AMB substrates with Si3N4 and DAB in order to identify the main factors that could increase the lifetime expectancy of power modules in such harsh environments. Finally, a new numerical study is carried out under ANSYS with an aim of evaluating the ceramic influence of the substrates over the lifespan of the assembly. In conclusion we will try to propose rules of design allowing to increase the lifespan of the assembly of the modules of power.