Shape-controlled crystal growth of Sr3NbGa3Si2O14 and Sr3TaGa3Si2O14 piezoelectric single crystal by micro-pulling-down method
We have grown the shape-controlled Sr<inf>3</inf>NbGa<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (SNGS) and Sr<inf>3</inf>TaGa<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (STGS) langasite-type crystals by the μ-PD method. Columnar-shaped SNGS and STGS crystals were grown using the Pt-Rh crucible with a columnar die in 3 mm diameter. Grown crystals indicated high transparency and approximately 3 mm diameter. Chemical phases of grown crystals were identified as a single phase of langasite-type structure. The lattice parameters of grown crystals were almost consistent with those of crystals grown by Czochralski (Cz) method. In the X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by Cz method.
Crystal Growth of Ca3Nb(Ga1−xAlx)3Si2O14 Piezoelectric Single Crystals with Various Al Concentrations
Ca3Nb(Ga1−xAlx)3Si2O14 (CNGAS) single crystals with various Al concentrations were grown by a micro-pulling-down (µ-PD) method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction.
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.