Interfacial Reaction between Zn-Al-Based High-Temperature Solders and Ni Substrate

The Zn-Al(-Cu) eutectic alloys (melting point 381°C) are candidates for use as Pb-free high-temperature solders as a substitute for Pb-based solders, which are suitable for severe working environments such as the engine room of hybrid vehicles equipped with an inverter system as well as a heat engine. In this study, the interfacial reaction between Zn-Al(-Cu) alloys and the Ni substrate during soldering, aging, and thermal cycling was investigated. Semiconductor chips and Ni substrates were soldered with Zn-Al(-Cu) alloys at various temperatures under a nitrogen atmosphere. The soldered assemblies were then heat-treated at 200°C and 300°C to examine the microstructural evolution at the soldered interface. The effect of severe thermal cycles between −40°C and 250°C in air on the microstructure and fracture behavior at the solder joint was investigated. Even after a 1000-cycle test, the thickness of the Al₃Ni₂ layer formed at the interface between the Zn-Al-based solder and the Ni substrate, which is responsible for the damage of the soldered assemblies, was quite small.     

Advanced Dicing Technology for Semiconductor Wafer—Stealth Dicing

ldquoStealth dicing (SD)rdquo was developed to solve inherent problems of a dicing process such as debris contaminants and unnecessary thermal damages on a work wafer. A completely dry process is another big advantage over other dicing methods. In SD, the laser beam power of transmissible wavelength is absorbed only around focal point in the wafer by utilizing the temperature dependence of the absorption coefficient of the wafer. The absorbed power forms a modified layer in the wafer, which functions as the origin of separation in the separation process. In this paper, we applied this method for an ultra-thin wafer. The reliability of devices that is diced by SD was confirmed.     

Comparison of the structural characteristics of chromosome VI in Saccharomyces sensu stricto: The divergence,species-dependent features and uniqueness of saké yeasts

Previous studies have revealed that chromosome VI of saké yeasts is much larger than that of the other strains of Saccharomyces cerevisiae. Southern analysis using segments of chromosome VI of a laboratory strain as probes suggested that the nucleotide sequence of a major portion of this chromosome is conserved, but considerable diversity was found in the distal parts in the other strains. Physical maps also indicated that differences in length of chromosome VI were mainly due to differences in its ends. NotI was found to generate 9 kb and/or 16 kb fragments from the left telomere of chromosome VI in most saké yeasts, but no fragment in the case of AB972. SfiI produced one or two 30–50 kb fragments from the right end of this chromosome in all saké yeasts tested, but produced a 20 kb fragment in the case of AB972. All S. cerevisiae strains not employed in saké brewing were the same as AB972 in these respects. S. paradoxus had one NotI site in chromosome VI, while S. bayanus had two, one of which is possibly common to both species. The SfiI site mentioned above was present in chromosome VI of all species, while that of S. bayanus and S. paradoxus each had a second site distinct from the other. Chromosome VI of S. pastorianus was not distinguishable from that of S. bayanus. © 1998 John Wiley & Sons, Ltd.     

Interface reactions between SiO2-PbO glass and Ni-Zn ferrite

The interface reactions between SiO₂-PbO melt and Ni-Zn ferrite were studied using electron probe microanalysis and X-ray diffraction. The mechanisms of interface reaction were investigated in relation to the glass-forming region. No intermediate layers were produced at the interface between SiO₂-PbO glass and Ni-Zn ferrite because of the small amount of dissolution of Ni²⁺ ion from the ferrite. A model of the interface reaction mechanism between SiO₂-PbO melt and Ni-Zn ferrite is proposed.     

Open reduction and varus-detorsion osteotomy with femoral shortening in treatment of congenital dislocation of the hip

In this study, we clinically and radiographically evaluated open reduction with shortening of the femur in children more than 1 year old with refractory congenital dislocation of the hip. In 19 children (aged 1-4 years), 22 joints were operated on. The patients were followed-up for an average of 8.7 years (range, 2-13 years). Functional results were satisfactory in all joints, and differences in limb length were not significant. Radiographically, good results (grades I and II) were obtained in 16 of the 22 joints, according to Severin's criteria. This surgical procedure may be indispensable for treating refractory congenital dislocation of the hip in children over 1 year old.     

Distribution of a novel angiotensin I-converting enzyme inhibitory substance (2″-hydroxynicotianamine) in the flour,plant parts,and processed products of buckwheat

2″-Hydroxynicotianamine (HNA) is a recently discovered angiotensin I-converting enzyme inhibitory compound present in buckwheat which displays hypotensive activity. Here, HNA levels in buckwheat flour, plants, and products were quantified to examine the potential functionality of this food. The HNA content of buckwheat flour ranged from 16–28 mg per 100 g dry weight. When the content was evaluated by the milling stage, common buckwheat contained 24.3, 24.1, and 34.1 mg in the inner, middle, and outer layers, respectively, whereas tartary buckwheat contained 16.8, 30.5, and 51.8 mg of HNA, respectively. Comparison of the distribution of HNA within buckwheat plants revealed that HNA was predominantly localised in seeds (buckwheat flour). The residual HNA levels after cooking ranged from 21% to 41% in dried buckwheat noodles. This study clarified that buckwheat flour contains high levels of HNA and is a readily available source of HNA if incorporated into one’s diet, which may help reduce hypertension.