Effect of soldering condition on formation of intermetallic phases developed between Sn-0.3Ag-0.7Cu low-silver lead-free solder and Cu substrate

In this paper, effect of soldering time and temperature on formation of intermetallic compounds developed between Sn-0.3Ag-0.7Cu lead-free solder and copper substrate was investigated. Dip soldering was performed at 250, 270, and 290 °C with soldering time of 5, 10, 15, and 20 s. Either ?-Cu₃Sn or η-Cu₆Sn₅ intermetallic phase was found at the interface between the solder and the substrate depending on the soldering condition, i.e., soldering time and soldering temperature. ?-Cu₃Sn was found only when the substrate was soldered at 250 °C for 5 and 10 s. At other soldering conditions, only η-Cu₆Sn₅ was found at the interfacial zone. Crystal structure of ?-Cu₃Sn intermetallic phase was orthorhombic, and it was hexagonal structure for η-Cu₆Sn₅. Transformation of the intermetallic phases was also discussed.     

Determination of Cd,Cu, and Zn in fish and mussel by AAS after ultrasound-assisted acid leaching extraction

An ultrasound-assisted solid–liquid extraction procedure by using diluted mixed acid solution was developed for determination of cadmium, copper and zinc in fish and mussel samples. The effects of several parameters such as nitric acid concentration, hydrochloric acid concentration, hydrogen peroxide concentration, leaching solution volume, and sonication time have been investigated. A 30-min sonication, 56 °C operating temperature and 6 mL of 1:1:1 HNO₃(4 M):HCl(4 M):H₂O₂(0.5 M) were used for 0.5 g of dried sample. Cadmium and copper were determined by graphite furnace atomic absorption spectrometry, and zinc was determined by flame atomic absorption spectrometry. The results obtained from the proposed procedure were evaluated by comparison with the results obtained by microwave-assisted digestion. Ratio (%) of metal amount obtained from leaching technique to amount obtained from digestion technique for cadmium, copper and zinc ranged from 92% to 114% for fish and from 88% to 103% for mussel samples. The MDL were 0.02, 0.13 and 0.63 mg kg⁻¹ for cadmium, copper and zinc, respectively. The accuracy of the developed method was investigated by analyzing a dogfish muscle certified reference material (DORM-2). Recoveries were obtained in the order of 80.9 ± 0.3 and 87.2 ± 0.6%.     

Evolution of Intermetallic Compounds between Sn-0.3Ag-0.7Cu Low-silver Lead-free Solder and Cu Substrate during Thermal Aging

The growth, transformation, and lattice structure of intermetallic compounds formed between Sn–0.3Ag–0.7Cu lead-free solder and copper substrate were investigated. Dip soldering was used to initiate the reaction between the solder and substrate. An η-Cu6Sn5 intermetallic phase possessing a hexagonal lattice structure was found at the as-soldered interface. Thermal aging at a number of conditions resulted in the formation of a Cu3 Sn intermetallic phase between the Cu6Sn5 layer and the copper substrate. ε-Cu3 Sn with an orthorhombic lattice structure was found together with hexagonal Cu3 Sn. Subsequently, the activation energies of the intermetallic phases were calculated and compared to results obtained from the literature. The comparison showed that good agreement existed between the findings from this study and literature data within a similar temperature range.     

Effects of drying methods and enzyme aided on the fatty acid profiles and lipid oxidation of rice by-products

We investigated the influence of hot air drying, far infrared radiation (FIR), and cellulase aided on the fatty acid composition and primary lipid oxidation of rice bran, rice husk, and ground rice husk. The lipid content was significantly reduced in the sample dried by hot air and FIR but remained unchanged in the cellulase-aided rice bran and husk. We found that oleic acid (18:1n ? 7) and linoleic acid (18:2n ? 6) increased in hot air- and FIR-dried rice bran. On the other hand, PUFA content was significantly reduced in the samples dried by hot air and FIR but remained unchanged in the cellulase-aided rice bran and husk. Cellulase aided gave significantly higher concentrations of SFA, MUFA, and PUFA in all samples than did hot air and FIR drying. However, the rice by-products dried with hot air and FIR had the lowest PV and TBA values during 30 days of storage. Our findings provide useful information for the pretreatment of rice by-products; consequently, more utilization of rice by-products will be extended for uses such as oil production.     

Energy‐efficient human probes for high‐resolution sensing in urban environments

Portable sensory devices carried by humans—which are referred to as Human Probes—facilitate easy‐to‐use sensing and monitoring of urban areas. However, when each Human Probe individually senses and transmits information, the sensing activity is inefficient in terms of energy consumption. In this paper, we propose Aquiba protocol in which the sensing activities carried out by the Human Probes are adjusted autonomously under different conditions. Aquiba involves cooperative sensing that helps in efficiently maintaining the desired sensing resolution, while minimizing overall energy consumption. To validate Aquiba protocol, we have conducted comprehensive simulations by including small‐scale and large‐scale scenarios along with applying three movement patterns of human. The simulation results demonstrate that Aquiba protocol is capable of providing high sensing resolution and reducing energy consumption substantially. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.