Creep and fatigue behaviors of the lead-free Sn–Ag–Cu–Bi and Sn60Pb40 solder interconnections at elevated temperatures

Creep and fatigue behaviors of the interconnections soldered by the lead-free Sn–Ag–Cu–Bi solder were investigated at different elevated temperatures (with the homologue temperature in the range of 0.71– 0.82), with a comparison to that of a traditional Sn60Pb40 solder. The results show that the lead-free Sn–Ag–Cu–Bi solder shows a superior anti-creep performance over the Sn60Pb40 solder, in terms of a much lower creep strain rate and a vastly elongated creep fracture lifetime; in the secondary creep regime, the calculated creep-activation energy for two solders is reasonably close to other published data. In addition, it has also been shown that the joints soldered by the lead-free Sn–Ag–Cu–Bi solder exhibits a superb fatigue property.     

Determination of the thermodynamic properties of liquid <Emphasis Type="Italic">n</Emphasis>-hexadecane from the measurements of the velocity of sound

The density, the isobaric expansion coefficient, the specific heats at constant pressure and constant volume, and the isothermal compressibility coefficient of liquid n-hexadecane have been calculated in the range of temperatures 298–433 K and pressures 0.1–140 MPa from the data on the velocity of sound. The coefficients of the Tate equation in the above parametric range have been determined. The table of the thermodynamic properties of n-hexadecane has been presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 150–156, January–February, 2009.     

Temperature dependent growth and optical properties of SnO<Subscript>2</Subscript> nanowires and nanobelts

SnO₂ nanowires and nanobelts have been grown by the thermal evaporation of Sn powders. The growth of nanowires and nanobelts has been investigated at different temperatures (750–1000°C). The field emission scanning electron microscopic and transmission electron microscopic studies revealed the growth of nanowires and nano-belts at different growth temperatures. The growth mechanisms of the formation of the nanostructures have also been discussed. X-ray diffraction patterns showed that the nanowires and nanobelts are highly crystalline with tetragonal rutile phase. UV-visible absorption spectrum showed the bulk bandgap value (∼ 3–6 eV) of SnO₂. Photoluminescence spectra demonstrated a Stokes-shifted emission in the wavelength range 558–588 nm. The Raman and Fourier transform infrared spectra revealed the formation of stoichiometric SnO₂ at different growth temperatures.     

Embrittlement and fracture toughness of highly irradiated austenitic steels for vessel internals of WWER type reactors. Part 1. Relation between irradiation swelling and irradiation embrittlement. Experimental results

For the assessment of the effect of irradiation-induced swelling on mechanical properties of an irradiated austenitic steel, investigations have been performed on 08Kh18N10T steel – base metal and weld – exposed to damaging dozes close in magnitude, within two different temperature ranges: (a) 330–340°C, where there occurs almost no swelling, and (b) 400–450°C, where a significant level of swelling (3–13%) is observed. Based on the investigation results, the temperature dependence of short-term mechanical properties is plotted for the irradiated metal. A comparative study of magnetization of the metal irradiated at various temperatures has been carried out. Fractographic examination of the tested specimens has been performed.     

Observation of a negative characteristic temperature for the threshold current of diode lasers for the 2.8 /gmm spectral range

A decrease in the lasing threshold with increasing temperature has been observed in InAs/InAsSbP laser heterostructures for the 2.7–2.9 μm spectral range at cryogenic temperatures (T=32–85 K). At temperatures below 50 K a negative characteristic temperature, T ₀=−70 K, was obtained for the threshold current. Characteristics of the temperature dependence of the threshold current and the laser output power were investigated. Pis#x2019;ma Zh. Tekh. Fiz. 23, 72–79 (November 26, 1997)     

Influence of the temperature and oversouring of blood on its hemorheological properties

The influence of the change in the temperature and the acidity of blood on its hemorheological properties has been analyzed. It is shown that, at temperatures lower than 45°C, the temperature dependence of the apparent viscosity of blood at a rate of shear ranging from 0.3 to 50 sec⁻¹ is adequately defined by the Arrhenius model with a viscous-flow activation energy of 13–17 kJ/mole. In the range of pH 6.3–7.6, the oversouring of blood mainly influences the critical shear stress, and the Caisson viscosity depends only weakly on the acid-base equilibrium. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 180–185, September–October, 2005.     

Effect of strain rate and environment on the mechanical properties of the Ni–19Si–3Nb–0.15B–0.1C intermetallic alloy at high temperatures

The effect of strain rate and environment on the mechanical behavior at different temperatures of the Ni–19Si–3Nb–0.15B–0.1C alloy is investigated by atmosphere-controlled tensile testing under various conditions at different strain rates and different temperatures). The results reveal that the Ni–19Si–3Nb–0.15B–0.1C alloy exhibits ductile mechanical behavior (UTS ∼ 1250 MPa, ε ~ 14%) at temperatures below 873 K under different atmosphere conditions. However, the alloy without boron and carbon addition shows ductile mechanical behavior only when the sample is tested in vacuum. This indicates that the microalloying of boron and carbon does overcome the environmental embrittlement from water vapor at test temperatures below 873 K for the Ni–19Si–3Nb base alloy. However, the boron and carbon doped alloy still suffers from embrittlement associated with oxygen at a medium high temperature (i.e. 973 K). In parallel, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 873 K. However, the ultimate tensile strength exhibits high dependence on the strain rate in air at temperatures above 873 K, decreasing the ultimate tensile strength with decreasing strain rate.     

Microstructures and high temperature oxidation resistance of alloys from Nb–Cr–Si system

Oxidation behavior of Nb–30Si–(10,20)Cr alloys have been evaluated in air from 700 to 1400 °C by heating for 24 h and furnace cooling them. The lower weight gain per unit area has been observed for 20Cr alloy at 1200, 1300, and 1400 °C. Pesting has been observed at lower temperatures (700, 800, 900 °C). Analysis indicates that the powder formation at 900, 100, 1100 °C may be associated with β form of Nb₂O₅ (base centered monoclinic form). However the m-monoclinic form of Nb₂O₅ evolves at temperatures above 900 °C while o-orthorhombic Nb₂O₅ forms at below this temperature. The phases in the alloys have been calculated using the Pandat^TM software program at different temperatures using calculated Nb–Cr–Si phase diagrams.     

Realization of high pressures and temperatures in the gas phase of a bubble liquid flowing through a nozzle

A steady flow of a bubble gas-liquid mixture in a nozzle having a circular cross section has been investigated. The possibility of realization of superhigh temperatures and pressures in the gas phase of the mixture in the region near the smallest cross section of the nozzle has been analyzed. The influence of the initial radius of the flow and the volume content of bubbles, determining the volumetric rate of flow of the liquid supplied to the nozzle, on the pattern of the flow has been considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 134–137, November–December, 2007.     

Speed of sound in <Emphasis Type="Italic">n</Emphasis>-hexane, <Emphasis Type="Italic">n</Emphasis>-octane, <Emphasis Type="Italic">n</Emphasis>-decane,and <Emphasis Type="Italic">n</Emphasis>-hexadecane in the liquid state

This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433 K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values of the speed of sound are in good agreement with the literature data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008.     

Density of states effective mass of SnBi<Subscript>4</Subscript>Se<Subscript>7</Subscript> deduced from the temperature dependence of electrical conductivity in the activation regime

Current–voltage (I–V) measurements on polycrystalline samples of Bi₂Se₃ and stoichiometric ternary compound in the quasi-binary system of SnSe–Bi₂Se₃ at different temperatures in the vicinity of room temperature have been performed. Also, temperature dependence of electrical conductivity has been measured. From the analysis of the temperature dependence of electron concentration in the activation regime above room temperature, the density of states effective mass, m*, has been determined. Some intrinsic and contact properties such as barrier heights, ideality factors, and carriers concentrations have been investigated using I–V characteristics. It has been found that all samples exhibit ohmic and space charge limited conduction at low and high fields, respectively.     

Role of Ti diffusion on the formation of phases in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> brazed interface

Diffusivities of Ti, Cu, Al and Ag in the interface of Al₂O₃–Al₂O₃ braze joints using Ag–Cu–Ti active filler alloy, have been calculated by Matano–Boltzman method. The Matano plane has been identified for each elemental diffusion at various brazing temperatures. The diffusivities of Ag, Cu and Al are almost insignificant on formation of interface during brazing, whereas the diffusivity of Ti changes significantly with the brazing temperature and controls the formation of different reaction product in the interface. Presence of TiO and Ti₃Cu₃O phases in the interface has been confirmed by transmission electron microscopy (TEM).     

Exact solution of the problem of nonstationary heat conduction for two semispaces in nonideal contact

An exact solution of the nonideal-contact problem of nonstationary heat conduction for two semispaces with constant initial temperatures has been obtained. It is shown that the problem at hand is similar in thermal action to the third boundary-value problem for a semispace bordering on a medium of constant temperature that has a certain value. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 86–87, September–October, 2006.     

Effect of heat treatment in air on the thermal properties of SiC fibre-reinforced composite. Part 1: a barium osumilite (BMAS) matrix glass ceramic composite

The thermal properties have been studied on a glass ceramic composite comprised of a barium osumilite (BMAS) matrix reinforced with SiC (Tyranno) fibres which has been subjected to a heat treatment in air in the range of 700–1,200 °C. Microstructural studies were carried out especially on of the interface between fibre and matrix. The presence of a carbon thin layer in the interface is a typical observation in SiC fibre-reinforced glass ceramic matrix composite systems. The microstructural evaluation and thermal properties showed a degradation of interfacial layer occurred at low heat treatment temperatures, (700–800 °C) this was attributed to the fact that, at those heat treatment temperatures the carbon rich layer formed during processing was oxidised away leaving voids between fibre and matrix, which were linked by isolated silicon-rich bridges. After heat treatment at higher temperatures of 1,000–1,200 °C, the thermal properties were retained or even enhanced by leaving a thick interfacial layer.     

Deformation behavior and mechanisms of a nanocrystalline multi-phase aluminum alloy

A nanocrystalline (nc) Al–Fe–Cr–Ti alloy containing 30 vol.% nc intermetallic particles has been used to investigate deformation behavior and mechanisms of nc multi-phase alloys. High compressive strengths at room and elevated temperatures have been demonstrated. However, tensile fracture strengths below 300 °C are lower than the corresponding maximum strengths in compression. Creep flow of the nc fcc-Al grains is suppressed even though rapid dynamic recovery has occurred. It is argued that the compressive strength at ambient temperature is controlled by propagation of dislocations into nc fcc-Al grains, whereas the compressive strength at elevated temperature is determined by dislocation propagation as well as dynamic recovery. The low tensile fracture strengths and lack of ductility at temperatures below 300 °C are attributed to the limited dislocation storage capacity of nanoscale grains. Since the deformation of the nc Al-alloy is controlled by dislocation propagation into nc fcc-Al grains, the smaller the grain size, the higher the strength. This new microstructural design methodology coupled with ductility-improving approaches could present opportunities for exploiting nc materials in structural applications at both ambient and elevated temperatures.     

Thick-film nitrogen-monoxide sensors for analysis of the combustion products of organic fuels at heat-and-power plants

The method of metal-screen printing is used to obtain thick films of WO₃ that are highly selective to NO. The films are then used to make nitrogen monoxide sensors that can detect concentrations of (5–1000)·10⁻⁶ while operating at temperatures within the range 175–300°C. A prototype of a system for continuously monitoring NO in power-plant emissions has been designed and built. Translated from Izmeritel'naya Tekhnika, No. 1, pp. 34–36, January, 1997.     

Temperature dependence of vickers microhardness and creep of InBi single crystals

Variation of Vickers microhardness of InBi single crystals with temperature has been studied. Loading time dependence of the microhardness at different temperatures has been used for the creep study in the temperature range 30° – 85°C. The activation energy for creep has been evaluated and the results are discussed.     

Correlation between microstructure and mechanical behaviour at high temperatures of a SiC fibre with a low oxygen content (Hi–Nicalon)

An oxygen free Si–C fibre has been studied in terms of the chemical, structural and mechanical properties produced as a function of annealing treatments. In spite of its high thermal stability with regard to a Si–C–O fibre the Si–C fibre was subject to moderate SiC grain growth, organization of the free carbon phase and densification within the temperature range 1200–1400°C. The strength reduction at ambient for temperatures ≤1600°C could possibly be due to SiC coarsening or superficial degradation. Bend stress relaxation (BSR) and tensile creep tests show that the as-received fibre undergoes a viscous flow from 1000°C. The thermal dependance of the creep strain rate strongly increases at temperatures ≥1300°C. This feature might be partly explained by the structural evolution of the fibre occurring above this temperature. Heat treated fibres (1400–1600°C) exhibit a much better creep strength, probably due to their improved structural organization. This revised version was published online in November 2006 with corrections to the Cover Date.