The design and manufacture of microelectronic devices requires perfect mastery of cutting-edge technologies. Our team is particularly interested in the problems of strain and reliability that need to be controlled at every stage of the device's design and manufacture. We developed an analytical model able to predict the strains and stresses in each of the layers and at each stage of manufacture. This model requires knowledge of realistic mechanical properties of the materials making up the device. Nano-indentation AFM, colored picosecond acoustics and temperature-dependent ellipsometry, can be used to characterize the thermo-mechanical properties materials (Young's modulus E and coefficient of thermal expansion CTE) but these techniques have major limitations: the measurements are local and/or perform to the extreme surface of the materials. We have therefore developed a more comprehensive and global characterization method, based on measurements of wafer curvature. First, this method is particularly effective for highlighting cross-linking problems in polymers. We used the method to characterize the thermomechanical properties of the various materials used in an imaging device and studied the mechanical integrity of a representative structure using our analytical model and finite element simulations. Finally, in order to understand all the potential problems, we worked on the effects linked to the ageing of materials.