Abu Zayed Mohammad Saliqur Rahman

Synchrotron VUV-UV and positron lifetime spectroscopy study of vacancy-type defects in reactor neutron-irradiated MgO·nAl2O3 (n = 2)

We investigated neutron-irradiation-induced point defects in spinel single crystals using a synchrotron VUV-UV source and positron lifetime spectroscopy. Photoexcitation (PE) spectra near 230 nm and their corresponding photoluminescence (PL) spectra at 475 nm were attributed to F-centers. With increasing irradiation temperature and fluence, PE efficiency and PL intensity decreased dramatically. Positron lifetimes (PLT) of neutron-irradiated and non-irradiated samples were measured to identify the cation vacancies. A PLT measurement of 250 ps was obtained in a neutron-irradiated (20 K) sample which is tentatively attributed to an aluminum monovacancy. Decreasing PLT with higher irradiation indicates the formation of oxygen-vacancy complex centers.

Nanomechanical properties of intermetallic compounds formed in electrodeposited Cu/Sn and Cu/Ni/Sn multilayer interconnects

Nanomechanical properties of intermetallic compounds (IMCs) formed in electrodeposited Cu/Sn and Cu/Ni/Sn multilayer interconnects were investigated in this study. The layers of Cu, Sn and Ni were formed by electrodeposition technique using copper pyrophosphate, tin methanesulfonic and nickel Watts bath, respectively. Deposition current density was set at 10 mA/cm2 for the copper bath and 20 mA/cm2 for tin and nickel baths. The interconnects were subjected to high temperature aging at 150 C for 168 h. A Hysitron Triboindenter 750 Ubi system was used for the nanoindentation experiments at ambient temperature. Elastic modulus and hardness of the IMCs were measured with good accuracy. Average Creep displacement under constant load was obtained for all the IMCs formed in Cu/Sn and Cu/Ni/Sn multilayer ultra small interconnects.

Effect of Ni nanoparticles on intermetallic compounds formation in SAC305 solder joint under high current density

Characteristics of intermetallic compounds (IMCs) can have serious impacts on reliability of solder joint. In the current study, Ni nanoparticles (NPs) have been added to SAC305 solder / Cu substrate interface by flux mixing and their effects on electromigration (EM) under high current density have been investigated. Electromigration (EM) tests were operated under a current density of 1×104 A/cm2, at 80°C with different time variation for samples prepared using 0 wt% and 2 wt% Ni NPs doped flux. It is found that 2 wt% Ni NPs doped flux influenced positively the reliability of SAC305 solder joint under high current density. Ni NPs addition depressed the polarity effect and reduced the voids, cracks and damages in solder joint.