Analyse thermique à haute résolution spatiale par thermoréflectance de composants de puissance

The technological evolution of IGBT components requires a strong increase in power density. This increase in power density leads to very high temperature fields and gradients in the components and makes it necessary to know the thermal constraints. The temperature is thus one of the dimensioning elements of the converters and is at the centre of the concerns of the designers.To characterize these components, we used thermoreflectance during this thesis. The work presented in this thesis consists of three main parts. First, we highlight the problem of registration in the thermoreflectance domain. We study two subpixel shift methods in order to choose the most adequate method to obtain an accurate reflectivity measurement. The results show that subpixel cross-correlation registration with a precise step size gives better results and that this step size is directly correlated with the noise level of the images.In the second part, we present a measurement methodology on an IGBT chip packaged in a power module. This methodology aims to determine several experimental parameters (optimal wavelength, minimum excitation frequency and influence of image accumulation on noise) and to choose the most suitable calibration method for this type of device. Then, we perform a detailed thermal study on the metallization of IGBT emitter.Finally, we perform thermal measurements through the silicone gel and study the influence of aging on the thermal mapping. The results obtained perfectly reflect the reality of the thermal behaviour of IGBTs in power modules.The thermal measurements performed in this thesis have shown the ability of thermoreflectance to have a high spatial resolution of the temperature and thus to trace the individual behaviour of the IGBT cells.