Effects of Co/Sm Composition on the Ordered Phase Formation in Sm-Co Thin Films Grown on Cu(111) Single-Crystal Underlayers
Sm-Co thin films were prepared on Cu(111) single-crystal underlayers by changing the Sm composition from 12 to 35 at.% and the effects of Co/Sm composition on the ordered phase formation were investigated. The epitaxial SmCo5 thin films were obtained for all samples. The SmCo5 epitaxial layer grown on Cu underlayer has two different types of domains whose orientations are rotated around film normal by 30 degrees to each other. Cu atoms substitute a part of the Co sites in the SmCo5 structure, and an alloy compound of Sm(Co,Cu) 5 phase was formed for all samples. The Sm(Co,Cu)5 phase was more Cu enriched with increasing the Sm composition. The Cu atom diffusion into Sm-Co layer plays an important role in assisting the formation of Sm(Co,Cu)5 ordered phase.
Epitaxial growth of hcp/fcc Co bilayer films on Al2O3(0001) substrates
Co magnetic bilayer films with different stacking structures of fcc/hcp and hcp/fcc were successfully prepared on Al2O3(0001) substrates employing Au and Cu underlayers. The structure and the magnetic properties of these bilayer films were investigated. The crystal structure and the strain of Co layers are influenced by the underlayer. Q-band ferromagnetic resonance analysis has shown that the Co bilayer films consist magnetically of fcc and hcp phases. It has been shown possible to prepare hcp/fcc Co epitaxial magnetic bilayer films that can be used for patterned media applications.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.