Wetting Behavior and Evolution of Microstructure of Sn–3.5Ag Solder Alloy on Electroplated 304 Stainless Steel Substrates

In the present study, wetting characteristics and evolution of microstructure of Sn?C3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag₃Sn, Ni?CSn, FeSn₂ and lesser percentage of Fe?CCr?CSn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn₂ and Fe?CCr?CSn IMCs. Presence of higher amount of Fe?CCr?CSn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.     

Effect of sintering parameters on the dynamic hysteresis scaling behavior of Ba0.85Sr0.15Zr0.1Ti0.9O3 ceramics

This article presents the effect of processing parameters on the ferroelectric hysteresis behavior of Ba_0.85Sr_0.15Zr_0.1Ti_0.9O₃ (BSZT) ceramics. The ferroelectric hysteresis scaling relations for coercive field (E_c) and remnant polarization (P_r) as a function of temperature have been proposed. The power law temperature exponents based on scaling were systematically established for all the hysteresis parameters. The temperature dependent scaling of E_c and P_r at sintering temperature of 1400, 1425, 1450 and 1475°C yields E_cαT^0.43, E_cαT^0.84, E_cαT^0.50, E_cαT^0.37 and P_rαT^?1.73, P_rαT^?1.55, P_rαT^?1.73, P_rαT^?1.69 respectively. Additionally, the scaling relations for the samples sintered at 1450°C at different time intervals of 3, 4, 5 and 6 hrs were also established. Finally, to understand the domain dynamics, back switching polarization (P_bc) as a function of temperature (T) was also estimated by Arrhenius law and the average activation energy was evaluated.     

Assembly reliability assessment and life estimation for a stacked area array device

Memory module manufacturers face an ongoing challenge to incorporate more functionality and superior performance with each new generation of product offering. The growth in demand for memory capacity is surpassing the pace at which memory component manufacturers are able to cost-effectively produce the next-generation of monolithic memory devices. Stacking components helps in the transition to higher-density memory while the design and production capability for the next-generation of memory devices is being developed. However, on the other hand, the complex nature of stacked Chip Scale Package (CSP) components mandates a thorough review of the assembly processes and a detailed reliability assessment for these packages.The research objective was to study the assembly reliability of stacked CSP components assembled on a densely populated lead-free memory module utilizing mirror imaged component placements. The assessment was carried out using thermal cycling and mechanical shock tests. The data collected from thermal cycling was also used for failure modeling and life estimation. The methodology for estimating field life was established and the field life was estimated for a server application. The results proved that stacked CSP components can be reliably assembled. The module using stacked CSP components surpassed the life expectancy for server applications, which is 10 years.     

Resonant Terahertz InSb Waveguide Device for Sensing Polymers

We have demonstrated the possibility of employing a device, designed to operate at terahertz (THz) frequencies, for sensing materials. The device consists of a waveguide section with a pair of stubs located at the middle and oriented transversely to the waveguide axis. The two stubs function as a resonator and, hence, the device would behave as a filter in the THz domain. The device was fabricated by laser micromachining of InSb pellets and was characterized by THz time-domain transmission spectroscopy. For a waveguide width of 740 μm and stub length of 990 μm, a transmission minimum is seen to occur at 0.265 THz. We investigated the capability of the device to sense polystyrene, dissolved in toluene, loaded into the stubs. The consequent change in the refractive index in the stubs alters the transmitted signal intensity. Our results show that, a change in concentration of polystyrene even by 1 mol/L, leads to measurable change in the transmission coefficient close to the resonant frequency of the device. Thus, our device operating at THz frequencies shows promising potential as chemical and bio sensors.     

Interaction Characteristics and Thermodynamic Behaviour of Gatifloxacin by Aluminium Hydroxide

ABSTRACT

The interaction pattern of gatifloxacin was temperature-dependent Langmuir isotherm, and the Langmuir coefficients increased as the temperature was raised. The perturbation experiment conducted on this system showed that the nature of interaction was irreversible. The enthalpy change is a positive value, indicating the existence of increased activation energy as the temperature is raised. The entropy value, 24.21 e.u. obtained in this system, indicated that the hydration shells of the ions were rather tightly bound. Intestinal permeation study also revealed the decreased bioavailability of gatifloxacin relatively to the presence of aluminium hydroxide. The strong adsorption of gatifloxacin by aluminium hydroxide is due to formation of complexes with cations of aluminium hydroxide through carboxyl and carbonyl groups of gatifloxacin.     

Stimulation of piezoelectric devices through bidirectional wireless energy transfer

A bidirectional energy transfer method is proposed and investigated for wireless excitation of piezoelectric devices. In the proposed bidirectional system, two receiving coils are deployed on both sides of a transmitting coil so as to capture the generated magnetic fields based on magnetic resonance coupling. The piezoelectric devices connected across each receiving coils get energized wirelessly because of the mechanism of electromagnetic resonance as well as piezoelectric resonance. It is found that the power across driven piezoelectric devices arrive at maximum for operating resonant frequency. The optimum power received by piezoelectric devices wirelessly through the bidirectional energy transfer system is significantly higher than that of the single‐sided receiver system. By implementing the proposed bidirectional energy transfer method, two piezoelectric devices can be energized simultaneously instead of a single piezoelectric device through the usual single‐side receiver system without affecting the maximum power transfer efficiency. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of GWQI to Assess Effect of Land Use Change on Groundwater Quality in Lower Shiwaliks of Punjab: Remote Sensing and GIS Based Approach

The groundwater resource is a multidimensional concept; it is defined by its location, its occurrence over time, its size, properties, conditions of accessibility, the effort required to mobilize it and therefore, all of which are to be considered in the context of demand. Groundwater, a renewable and finite natural resource, vital for man’s life, social and economic development and a valuable component of the ecosystem, is vulnerable to natural and human impacts. There is a great need for the assessment and monitoring of quality and quantity of groundwater resource required at local level to develop an exact scenario of watershed. In this study qualitative assessment of groundwater was done and a ground water quality index criterion was used to understand the suitability of groundwater for irrigation and drinking purpose in the study area. A GIS based multicriteria analysis was done by assigning weight to different water quality parameters. The water quality was grouped into six classes from very good to unfit for drinking. It was found that the in most part of the study area the water quality varied from moderate to good except in some areas where it is poor to unfit. An assessment of change in landuse and landcover was done from the year 1989 using Landsat data to year 2006 using LISS III satellite data. The change in LULC was correlated with water quality data and it was found that the areas around which rapid urbanisation as well as industrialisation is taking place showed poor to unfit groundwater in terms of quality.     

Simulation of ultrasonic phased array technique for imaging and sizing of defects using longitudinal waves

Phased array ultrasonics can be used as a rapid tool for imaging and sizing crack-like defects. This paper reports the simulation of phased array ultrasonic wave interaction with the defects using the finite-difference time domain (FDTD) method. Experiments were conducted to validate modeling results for pulse–echo simulations of the phased array transducer on a mild-steel (MS) pipe sample with circumferential internal surface notches of three different sizes. Experiments were carried out on the MS pipe specimen using a conventional ultrasonic technique with a 5 MHz transducer at 45° refracted angle within the specimen and the defects were imaged and sized using the relative arrival time technique (RATT). The experimental B-scans obtained using the conventional ultrasonic techniques were compared with the experimental B-scans obtained using the phased array instrument. Simulation studies were also carried out by steering the beam to the requisite angles by the phased array transducer to study the effect of various angles of incidence on the defect definition, i.e., with respect to imaging and sizing, using the RATT.     

Supercritical CO2 extraction of fatty oil from flaxseed and comparison with screw press expression and solvent extraction processes

Flax oil is commonly used in food due to high percentage of omega-3-fatty acid and omega-6-fatty acid. In the present work the flax seed was extracted using green solvent viz. supercritical CO₂ and compared with soxhlet and mechanical screw press methods. The chemical compositions of the oils were determined by CHNS analyser, GC-FID, GC/MS and ¹H NMR. The supercritical CO₂ process selectively extracted the fatty oils with high percentage of omega-3-fatty acid and omega-6-fatty acids. The chemical composition of screw press oil is close to that of supercritical CO₂ extracted oil, whereas the yield is nearly 27% less in comparison to the supercritical CO₂ method.