Effects of neutron irradiation on failure behavior analysis of high-density bumps under thermo-coupling conditions

As the space environment has conditions such as high vacuum, strong irradiation, and large temperature difference, spacecraft will face a series of challenges such as high-energy particles and extreme temperatures during on-orbit operation, especially neutron irradiation, which has a larger mean free range and a deeper depth of penetration, and which will cause serious damage to the electronic devices. Solder joints, the most failure-prone part of electronic devices, have received extensive attention from related researchers. In this study, the evolution of the microstructure of bumps under neutron irradiation and thermal field coupling conditions is analyzed utilizing scanning electron microscopy (SEM)\electron backscatter diffraction (EBSD), and the changes in the mechanical properties of the bumps are also analyzed by nanoindentation tests and push-ball experiments. The results show that the incidence of high-energy neutrons generates a large number of atomic vacancies, which exacerbates the Kirkendall effect. The point defects caused by neutrons gather together to form defect clusters. These microscopic defects impede the movement of slip dislocations, leading to the hardening of the material and an increase in elastic modulus. In contrast, the accumulation of a large number of defects leads to the failure of the bump.