INTERFACIAL DEGRADATION OF COPPER WIRE BONDS IN THERMAL AGING AND CYCLING CONDITION

Copper (Cu) wire bonds have become the dominant wire material used in microelectronic packages, having replaced gold (Au) in the majority of applications. Cost saving has been the key factor to drive this transition in wire bond material, although there are other advantages to Cu such as better electrical and thermal conductivity, reduced wire sweep during transfer molding and most importantly slower intermetallic compound (IMC) formation with Al (bond pad). Although IMC layers are much thinner than for Au-Al bonded joints, growth of second phase, Cu9Al4, due to exposure to high temperature leads to interfacial separation, which is exacerbated under thermal cycling condition ultimately leading to failure of the joint. Part I of this dissertation aims at addressing the effect of combined loading (thermal aging and cycling) on the reliability of Cu wire bonded devices using a unique long dwell thermal cycling profile that accelerates growth of different IMC phases (CuAl2 and Cu9Al4) and accelerates failure due to CTE mismatch between epoxy mold compound, die and Cu wire bond. Unlike many of the studies presented in literature, the test vehicle in this study are made of commercial off-the-shelf (COTS) parts, where a multitude of factors vary from one another, such as wire diameter, wire bond and bond pad characteristics, etc., the combination of which play a significant role in the life time of these devices and is not fully captured by first-principal models. Hence, a data-based life estimation method is developed, to aid in part selection based on initial bond characteristics. Critical parameters of wire bond that contribute to reliability are identified, the most significant of which is Al bond pad thickness, which controls the growth of IMC and influences time for Cu9Al4 IMC phase formation. Second part of this work is focused entirely on the Al bond pad thickness. Part II-A focuses on the qualitative comparison of pad thickness effect on the quality of initially formed bond through use of bond shear analysis and the effect of bond interface aging on bond shear analysis. Test vehicle consists of three pad thicknesses namely, 0.5 µm, 1 µm and 4 µm, over which Cu wirebonds with four different thermosonic bond recipes are made. Results from Part II-A provide guidelines for bond comparison using bond shear analysis. Part II-B focuses on the effect of bond pad thickness on the reliability of Cu wire bonds under isothermal aging at 175°C and 200°C for 1000 hours and 650 hours respectively. Test vehicle in this study consists of 0.675 µm and 3 µm pad thickness on silicon die in 20 leaded 5x5 QFN package. Wire bonds with one thermosonic bonding recipe are made on all the 90 packages used in the study. Electrical resistance and cross-sectional analysis are used to derive failure times, which is in turn used to build empirical relationship between pad thickness and time to failure. Result from this study shows longer time to failure for wire bonds on 3 µm pad compared to 0.675 µm pad due to delay in Cu9Al4 formation

Vibration Analysis of Carbon Fiber Reinforced Laminated Composite Skin with Glass Honeycomb Sandwich Beam Using HSDT

In this paper, the vibration analysis of uniform laminated composite sandwich beam with a viscoelastic core was studied. The governing equation of motion of the laminated composite sandwich beam has been derived based on higher order shear deformation theory (HSDT) in finite element model (FEM). The developed finite element model has been validated in terms of natural frequencies with the experimental values and the available literature. Various parametric studies have been performed to examine the impact of the core thickness, ply orientation and aspect ratio of the uniform laminated composite sandwich beam in response to free vibration for various boundary conditions. From the results it was concluded that that natural frequencies could be increased with increasing the core thickness and decreased with increasing the aspect ratio

A-TOS SYMPTOMS AND MOBILITY: A CASE STUDY ON UNCOMPLICATED ARTERIAL THORACIC OUTLET SYNDROME INVOLVING CONSERVATIVE MANAGEMENT

Background: Thoracic outlet syndrome (TOS) is a complex condition characterised by a group of conditions that compress on the neurovascular bundle that enter and leaves the thoracic inlet, interscalene triangle, costoclavicular space and above the pectoris minor that occur above the clavicle. 1-2% is associated with arterial obstruction among the other type of TOS. Symptoms usually annoy extremely by movement of cervical spine and head or by raising upper limb. The main aim of this case report is to reduce the gap in evidence based research and to describe the process and outcomes of conservative management. Methods: As there is no specific test for TOS, the patient was initially assessed with Adson and Roos test. All these test were positive along with MR angiogram and Doppler to confirm A-TOS. Physiotherapy intervention of 6 weeks with following procedure such as massage, warm up, passive stretching, active stretching, hand grip strengthening and cool down. Pain was assessed using VAS scale, strength was assessed using hand dynamometer. Patient was also taught to palpate her own pulse (radial) before intervention. Result: After 6 weeks of intervention patients pain intensity according to the VAS scale was 3, and pulse grade was 3+ that shows pain and pulse in the hand and wrist area were improved significantly. Patients hand grip strength is slightly improved compared to pre intervention using TuKey’s multiple comparison test and it is statistically significant in p<0.001, p<0.01 and p<0.05 respectively. Our results have convinced us that particular approach to the treatment of A-TOS. Conclusion: We concluded that the massage, stretching and hap grip strengthening will improve patient’s condition in Arterial TOS. We also suggested that future research should also focus on arterial TOS due to bony abnormalities and patient’s with arterial luminal defect

IMPORTANCE OF PHYSICAL ACTIVITY IN OBESE CHILDREN IN RELATION TO MOTOR SKILLS A SYSTEMATIC REVIEW

Background: Childhood obesity has reached epidemic proportions worldwide and is associated with increased cardio vascular mortality and morbidity in adult life. In children, obesity correlates strongly with a progressive reduction in the level of physical activity and changes in food habits. Methods: This study is a qualitative research study. A secondary data collection technique was utilized and conducted through a search of articles published between 2005 and 2014 in PubMed and Google scholar databases. The objective of the present study is to provide a systemic review of the available literature and outline the factors in early life that are associated with an increased risk of obesity in children there by leading to poor gross motor skill performance with the help of Anthropometric assessment, Body composition and Motor skills proficiency. Results: Importantly recent studies have demonstrated that exercise training improves vascular endothelial function and stimulation of pressure receptors leading to increased vagal activity in obese children. The current literature highlights the importance of adding exercise programs to clinics, schools and families for the physical and psychological wellbeing of children. Conclusion: Overall findings from the present review showed that normal children with physical exercise are more superior in motor skills compared to other peers. Results of the previous studies indicated that normal children’s are more efficient in bilateral coordination in greater balancing, efficient upper limb coordination and greater strength

Understanding the binding interaction mechanism of i-motif with fluorophores: A biophysical approach

DNA exists in many canonical and non-canonical forms. i-motif: a non-canonical, tetraplex, antiparallel strand rich in cytosine, formed by hemi protonated cytosine- cytosine+ base pairs under slightly acidic pH levels, i-motifs are utilised in the study of numerous fields of applications. These i-motif tend to exhibit the property of switching the fluorescent nature of ligands such as thiazole orange, crystal violet and berberine upon interaction. This work is focussed on a basic overview of i-motif and its interactions with ligands to form fluorescence probes which could be useful in bio imaging. Herein, we are trying to find the electronic properties of small molecules upon interacting with i-motif. In order to find the active binding site in i-motif, Molecular Docking simulation was performed. The best docked pose obtained from the docking studies were subjected to molecular dynamics simulations. Further, DFT studies, optimization and single point energy calculations were carried out for freeligands and those bounded with the secondary DNA structures to understand the intermolecular interaction and to study their electronic properties

Robust Facial Expression Recognition Using an Evolutionary Algorithm with a Deep Learning Model

The most important component that can express a person’s mental condition is facial expressions. A human can communicate around 55% of information non-verbally and the remaining 45% audibly. Automatic facial expression recognition (FER) has now become a challenging task in the surveying of computers. Applications of FER include understanding the behavior of humans and monitoring moods and psychological states. It even penetrates other domains—namely, robotics, criminology, smart healthcare systems, entertainment, security systems, holographic images, stress detection, and education. This study introduces a novel Robust Facial Expression Recognition using an Evolutionary Algorithm with Deep Learning (RFER-EADL) model. RFER-EADL aims to determine various kinds of emotions using computer vision and DL models. Primarily, RFER-EADL performs histogram equalization to normalize the intensity and contrast levels of the images of identical persons and expressions. Next, the deep convolutional neural network-based densely connected network (DenseNet-169) model is exploited with the chimp optimization algorithm (COA) as a hyperparameter-tuning approach. Finally, teaching and learning-based optimization (TLBO) with a long short-term memory (LSTM) model is employed for expression recognition and classification. The designs of COA and TLBO algorithms aided in the optimal parameter selection of the DenseNet and LSTM models, respectively. A brief simulation analysis of the benchmark dataset portrays the greater performance of the RFER-EADL model compared to other approaches

Molecular and Functional Characterization of FLOWERING LOCUS T Homologs in Allium cepa

Onion bulbing is an important agricultural trait affecting economic value and is regulated by flowering-related genes. FLOWERING LOCUS T (FT)-like gene function is crucial for the initiation of flowering in various plant species and also in asexual reproduction in tuber plants. By employing various computational analysis using RNA-Seq data, we identified eight FT-like genes (AcFT) encoding PEBP (phosphatidylethanolamine-binding protein) domains in Allium cepa. Sequence and phylogenetic analyses of FT-like proteins revealed six proteins that were identical to previously reported AcFT1-6 proteins, as well as one (AcFT7) with a highly conserved region shared with AcFT6 and another (comp106231) with low similarity to MFT protein, but containing a PEBP domain. Homology modelling of AcFT7 proteins showed similar structures and conservation of amino acids crucial for function in AtFT (Arabidopsis) and Hd3a (rice), with variation in the C-terminal region. Further, we analyzed AcFT expression patterns in different transitional stages, as well as under SD (short-day), LD (long-day), and drought treatment in two contrasting genotypic lines EM (early maturation, 36101) and LM (late maturation, 36122). The FT transcript levels were greatly affected by various environmental factors such as photoperiod, temperature and drought. Our results suggest that AcFT7 is a member of the FT-like genes in Allium cepa and may be involved in regulation of onion bulbing, similar to other FT genes. In addition, AcFT4 and AcFT7 could be involved in establishing the difference in timing of bulb maturity between the two contrasting onion lines

FORMULATION AND EVALUATION OF NATURAL ULTRASOUND GEL FOR PHYSIOTHERAPY TREATMENT

Commercially available ultrasound gel contains lot of chemicals like carbapol R 940 polymer and phenoxyethanol which are allergenic to skin, expensive and not available in enormous quantities. The demand for ultrasound gel is due to its wide range of applications medical and paramedical fields. Hence, our objective was to formulate and evaluate the ultrasound gel made from natural starch powder. The gel was made by heating water with corn starch. The formulated gel was used for physiotherapy ultrasound treatment with the addition of Aloe vera gel to get fast pain relief in the affected area. The results showed that the formulated ultrasound gel and its ingredients were consistent in quality and can be easily used. The formulated ultrasound gel was found to be superior to commercially available gel in part of pain management score. It is concluded that the formulated ultrasound gel can be used for ultrasound physiotherapy treatment. However, further studies are warranted to confirm its effectiveness and also to develop into commercial standards. Keywords: Physiotherapy; Ultrasound Gel; Aloe vera; Analgesic; Pain Managemen