A review of interconnect materials used in emerging memory device packaging: first- and second-level interconnect materials

The main motivation of this review is to study the evolution of first and second level of interconnect materials used in memory device semiconductor packaging. Evolutions of bonding wires from gold (Au) to silver (Ag) or copper (Cu) have been reported and studied in previous literatures for low-cost solution, but Au wire still gives highest rating in terms of the performance of temperature humidity test, high temperature storage, and bond-ability, etc. However, a new bonding wire material, Au-coated Ag, is recently developed to be an alternative solution which gives comparable performance, but lower cost compared to Au wire. In the first section of the article, the influence of a variety of factors were reviewed, which includes reliability performance and interfacial reaction that determines the performance of Au-coated Ag to reach for developing high reliability of bonded devices. With respect to second-level interconnects, SAC305 and SAC302 solder alloys give a balance performance between temperature cycling testing and drop testing, which are widely used in many field applications, such as mobile, consumer and computer. SAC405 and LF35 are developed for specific requirements such as SAC405 owns better temperature cycling performance, whereas LF35 gives excellent drop performance compared to SAC305 or SAC302. However, with market demands on automotive electronics get strong in recent years, solder joint reliability is being reviewed and discussed, especially in temperature cycling performance. Typical solder alloys on Ni/Au surface finish were not designed for automotive application to fulfill the requirement of board level reliability. Hence, newly developed solder alloys with Sn/Ag/Cu/Bi/Ni elements and Cu-OSP substrate surface finishes will be reviewed in the second section of the article.

     

Performance improvement in an OFDM system with MBH combinational pulse shape

In this paper, the Modified Bartlett–Hanning (MBH) window family is used in an OFDM system to reduce the effect of frequency offset on both the parameters i.e., the inter-carrier interference (ICI) and bit error rate (BER). The performance metric of suggested OFDM model with several Nyquist pulse shapes, including rectangular, Bartlett, raised cosine (RC) and better than raised cosine (BTRC) pulse shapes are also evaluated. These pulse shapes are found as members of the MBH pulse shape family, exactly or equivalently. It is observed that the ICI, BER and signal to interference ratio (SIR) of the OFDM system with different MBH pulse shapes are better than BTRC, RC, Bartlett and rectangular pulse shapes. The MBH pulse shape family, where different pulses can be generated by taking numerous values of the pulse shape parameter ‘β’, is providing a consistent advantage over the BTRC pulse shape in terms of ICI and BER in the acceptable range of carrier frequency offset along with better spectral efficiency due to their improved side-lobe levels. The other pulse shapes e.g. second order continuous window (SOCW), phase modified sinc pulse (PMSP) and Frank?s window are also compared with proposed pulse shapes and found that the MBH family pulse shapes are equally comparable in terms of performance metric used.     

Optimization of Cottonseed Oil Ethanolysis to Produce Biodiesel High in Gossypol Content

Transesterification of cottonseed oil was carried out using ethanol and potassium hydroxide (KOH). A central composite design with six center and six axial points was used to study the effect of catalyst concentration, molar ratio of ethanol to cottonseed oil and reaction temperature for percentage yield (% yield) and percentage initial absorbance (%A _385nm) of the biodiesel. Catalyst concentration and molar ratio of ethanol to cottonseed oil were the most significant variables affecting percentage conversion and %A _385nm. Maximum predicted % yield of 98% was obtained at a catalyst concentration of 1.07% (wt/wt) and ethanol to cottonseed oil molar ratio of 20:1 at reaction temperature of 25 °C. Maximum predicted %A _385nm of more than 80% was obtained at 0.5% (wt/wt) catalyst concentration and molar ratio of 3:1 at 25 °C. The response surfaces that described % yield and %A _385nm were inversely related. Gossypol concentration (% wt), oxidative stability and %A _385nm of biodiesel were found to be highly correlated with each other. Hence, color %A _385nm is a measure of the amount of pigments present in biodiesel fuels that have not yet been subjected to autoxidation. High gossypol concentration also corresponds to a fuel with high oxidative stability. The fatty acid ethyl esters (FAEE) produced from cottonseed oil had superior oxidative stability to fatty acid methyl esters (FAME) produced from cottonseed oil.     

Effect of lactic acid on polymer crystallization chain conformation and fiber morphology in an electrospun nylon-6 mat

The role of lactic acid (LA) on the polymer crystallization chain conformation and the surface modification of the electrospun nylon-6 fibers were examined. The effect of different amounts of LA on the polymer crystallization chain conformation of nylon-6 mat was evaluated using XRD, FT-IR and Raman spectroscopy whereas the surface modification of the electrospun mats was examined by FE-SEM, contact angle and mechanical properties measurement. It was found that the transition of meta-stable γ-form into the thermodynamically stable α-form was achieved by increasing the amounts of LA in the blend mixture. The adhesive property of LA was found to be responsible for the transformation from non-bonded to the point-bonded structure of nanofibers in the electrospun nylon-6 mat. The resultant LA/nylon-6 hybrid mat with improved hydrophilicity and mechanical properties may be a potential candidate for tissue scaffold.     

Synthesis,characterization, and photocatalytic properties of ZnO nano-flower containing TiO2 NPs

In this study, TiO₂-impregnated ZnO nano-flowers were synthesized by one-pot hydrothermal process. Aqueous suspension containing ZnO precursor and commercial TiO₂ NPs (P25) is heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), which revealed that TiO₂ NPs were attached on the surface of ZnO flower. It was observed that the presence of TiO₂ NPs in the hydrothermal solution could sufficiently decrease the size of ZnO flower. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to be effective photocatalyst under UV-irradiation.     

ICI Reduction in OFDM System Using IMBH Pulse Shapes

In this paper, the Improved Modified Bartlett-Hanning (IMBH) window family is used in an OFDM system to reduce the ICI. It is found that the IMBH pulse shape gives better results than the PMSP, ISP, BTRC, RC, Bartlett and rectangular pulse shapes in terms of both ICI and BER. The optimization of SIR in terms of window parameters has also been obtained. This analysis provides a better insight to control ICI or BER with proposed pulse shape. The IMBH pulse shapes give an improvement of 2–3 dB in ICI with different frequency offsets and roll-off factors. Similarly, with proposed pulse shapes the BER level can be obtained at lower SNR of approximately 5 dB. Therefore, the IMBH pulse shapes outperform other reported pulse shapes in both the dimensions, i.e., ICI and BER.     

Sequestration of nickel from aqueous solution onto activated carbon prepared from Parthenium hysterophorus L

In the present study, nickel removal efficiency of sulphuric acid-treated Parthenium carbon (SWC) from simulated wastewater has been investigated. Batch mode adsorption experiments have been conducted by varying pH, nickel concentration, adsorbent dose and contact time. Ni(II) removal was pH-dependent and found to be maximum at pH 5.0. The maximum removal of Ni(II) was achieved within 4h after the start of every experiment. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models to evaluate the model parameters. Both models represented the experimental data satisfactorily. The monolayer adsorption capacities of SWC as obtained from Langmuir isotherm was found to be 17.24 mg/g. The Lagergren first-order model was less applicable than pseudo-second-order reaction model. The adsorbent was also characterized including infrared spectroscopy and scanning electron microscopy. The FT-IR study indicated the presence of OH, CH, CO and CO groups in the adsorbent.     

Fabrication of polymeric microfibers containing rice-like oligomeric hydrogel nanoparticles on their surface: A novel strategy in the electrospinning process

In this work, nonwoven fiber mats of poly(ε-caprolacton) (PCL) and PCL blended with methoxy poly(ethylene glycol) (MPEG) oligomer were generated by electrospinning. The electrospinning was carried out in two different conditions depending upon the collector medium i.e. with and without water bath. It was found that the addition of MPEG increased the diameter of PCL microfibers when the electrospun mat was collected without water bath. However, the collection of microfibers into the water bath produced rice-like nanoparticles (NPs) of MPEG on the surface of PCL microfibers. The formation of hybrid mat containing hydrophobic PCL microfibers with hydrophilic MPEG hydrogel NPs is not only beneficial in future drug and gene delivery system but also useful in tissue engineering.     

Venous thromboembolism in connection with physical restraint

A 29-year old man was admitted to an emergency psychiatric ward because of exacerbation of a chronic paranoid schizophrenia. He was restrained after arrival, and seven days later a deep venous thrombosis and a pulmonary embolism were diagnosed. No haematological predisposing factors (coagulation inhibitor deficiency, activated protein C resistance, or antiphospholipid antibodies) were identified, except for a questionable borderline increase of the fibrinolysis inhibitor PAI-1, and combined type II hyperlipidaemia. During the last 15-20 years, there has been a considerable reduction in the use of restraint and seclusion in Norway. The use of seclusion and restraint may be effective in preventing injury and reducing agitation, but these procedures may also have harmful physical, and in particular psychological side-effects. To our knowledge, this is the first report to demonstrate an association between venous thromboembolism and physical restraint. Immobilisation is a well-known risk factor for thrombophlebitis, and special attention should be paid to this problem on psychiatric wards. However, until more is known about thrombosis in relation to restraint, it is not advisable to recommend prophylactic treatment of thrombosis.     

Effect of Precipitation Temperature, pH and Agitation on the Acid Reactivity of Aluminum Hydroxycarbonate Gel

A completely randomized 2³-factorial design study of the precipitation of aluminum hydroxycarbonate gel by the reaction of aluminum chloride with sodium carbonate and sodium bicarbonate showed that the precipitation temperature and end-point pH were significant in terms of the rate of acid neutralization at the 0.01 level and that stirring speed was significant at the 0.05 level. No significant interactions occurred between the parameters. The most reactive gels were precipitated at 25°, pH 6.5 and either 15 or 500 rpm. After aging for 105 days at 25° these gels exhibited a twelvefold greater rate of acid neutralization than the least reactive gel which was precipitated at 4°, pH 5.8 and 15 rpm. The results are analyzed in terms of the effect of each parameter on the particle size and structure of aluminum hydroxycarbonate gel