Titolo della tesi: Advanced Micro and Nano Characterization: from Leaded and Lead-free Solder Joints to 2D-Enhanced Materials for Cutting-Edge Space Applications
This thesis aims to study the behavior of materials for use in space and high-performance electronic applications with advanced micro and nano-characterization methods adopting extreme environmental conditions. The analysis of structural, morphological, and compositional changes in solder joints and 2D materials is done by employing Opto-Digital Microscopy (ODM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and high-resolution X-ray Microscopy (XRM). The research involved the analysis of traditional leaded alloys, such as InPb/Au and SnPb/PtAu, and lead-free alternatives, such as 96.5Sn/3.0Ag/0.5Cu (SAC305), under different ageing conditions at variable temperatures and pressures including high vacuum (HV). In the case of the solder joint InPb/Au, the growth of intermetallic compounds (IMCs), evidenced by a formation and propagation of silvery and black rings, combined with a pronounced volume shrinkage was observed. The activation energy (Ea) governing the shrinkage process was precisely determined within the narrow range 0.38–0.41 eV while for the growth of IMC Ea was about 0.45 eV for silvery rings and 0.21 eV for black rings. Acceleration factors (AFs) were quantified, enabling long-term behavior prediction. SAC305 as a lead-free solder was characterized by the maintenance of structural integrity, whereas SnPb/PtAu showed high chemical-physical stability. The present work of the thesis deals also with the integration of Few-Layer Graphene (FLG) and hexagonal Boron Nitride (h-BN) into polymers and coatings for the enhancement and reinforcement of their mechanical, thermal, and electrical properties. FLG-doped polymer matrices have been investigated and their application in 3D printing and coatings has been considered to evaluate the possibility of constituting replacement materials in weight-sensitive applications and extreme environments. The use of fused deposition modeling (FDM) for FLG-reinforced composites will offer the possibility of passing from lab-scale innovation of 2D material to industrial-scale applications. These results represent the power of state-of-the-art, non-destructive micro-nano characterization technologies in the study of advanced material systems for optimization in various applications. The research provides a solid base for the processes of materials qualification and supports the development of evaluation methodologies for future materials to employ in modern space engineering and next-generation electronics.