bluuebunny/crossref_metadata_2025 huggingface dataset:
Jamaican Mothers’ Influences of Adolescent Girls’ Sexual Beliefs and Behaviors
Authors: Katherine Hutchinson M. , Kahwa Eulalia , Waldron Norman , Hepburn Brown Cerese , Hamilton Pansy I. , Hewitt Hermi H. , Aiken Joyette , Cederbaum Julie , Alter Emily , Sweet Jemmott Loretta
Published: February 2012

Purpose: The purpose of this study was to identify the ways in which urban Jamaican mothers influence their adolescent daughters’ sexual beliefs and behaviors in order to incorporate them into the design of a family‐based human immunodeficiency virus (HIV) risk reduction intervention program.

Design: Focus groups were conducted with 46 14‐ to 18‐year‐old adolescent girls and 30 mothers or female guardians of adolescent girls recruited from community‐based organizations in and around Kingston and St. Andrew, Jamaica. Separate focus groups were held with mothers and daughters; each included 6 to 10 participants. Focus group sessions were scripted, led by teams that included trained Jamaican and American facilitators and note‐takers, and audio‐taped to ensure data accuracy. Data were analyzed using qualitative content analysis.

Findings: Four major maternal influences were identified: mother‐daughter relationship quality, mother‐daughter sexual communication, monitoring or supervision, and maternal sexual role modeling. Mothers’ and daughters’ reports were consistent; both groups identified positive and negative influences within each category.

Conclusions: Some maternal influences were positive and health promoting; others were negative and promoted unsafe sexual activity and risk for HIV and other sexually transmitted infections. These influences were incorporated into the design of a culture‐specific family‐based HIV risk reduction intervention tailored to the needs of urban Jamaican adolescent girls and their mothers.

Clinical Relevance: In order to be effective, family‐based HIV risk reduction interventions should be theory based and tailored to the target audience. The four maternal influences identified in this formative study were incorporated into the subsequent intervention design.

Journal of Nursing Scholarship, 2011; XX:X, XXX–XXX. ©2011 Sigma Theta Tau International.
Feeding behaviour of the Asiatic citrus psyllid, Diaphorina citri, on healthy and huanglongbing‐infected citrus
Authors: Cen Yijing , Yang Chengliang , Holford Paul , Beattie G. Andrew C. , Spooner‐Hart Robert N. , Liang Guangwen , Deng Xiaoling
Published: February 2012

Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Psyllidae) is a vector of huanglongbing, a disease of citrus that in Asia is caused by ‘Candidatus Liberibacter asiaticus’ (α‐Proteobacteria) (Las). Acquisition of Las by D. citri appears to be variable, and this variability may be due to the suitability of the host plants and their tissues for acquisition. Therefore, this study aimed to determine the effect of symptom severity of the disease on the feeding behaviour of D. citri. Use of an electrical penetration graph showed that the pathway phase of D. citri consisted of four waveforms, A, B, C, and D; waveforms A and B have not been reported for D. citri before. The remaining waveforms, E1, E2, and G, conform to those described before for D. citri. The duration of the non‐penetration period did not differ between healthy or infected plants. However, in moderately and severely symptomatic plants, the duration of the pathway phase increased, whereas the phloem phase was shorter. In all diseased plants, the times to first and sustained salivation in the phloem were longer than those in control plants, with the times being related to symptom severity. As symptom expression increased, the percentage of time spent by psyllids salivating during the phloem phase increased; however, the percentage of time spent in phloem activities reduced gradually from ca. 74% in the control plants to ca. 8% in the severely symptomatic plants. In contrast, the percentage of time spent on xylem activities increased, as did the proportion of psyllids feeding from xylem. The differences in the durations of the E waveforms on plants showing different levels of symptom expression may account for differences in acquisition found amongst studies; therefore, future work on the acquisition and transmission of Las needs to carefully document symptom expression.
Osteogenesis at implants without primary bone contact – An experimental study in dogs
Authors: Sivolella Stefano , Bressan Eriberto , Salata Luiz A. , Urrutia Zoraya A. , Lang Niklaus P. , Botticelli Daniele
Published: February 2012

Aim

To evaluate the healing at implants with a moderately rough surface placed and stabilized in recipient sites of dimensions deeper and larger than that of the implants to avoid any contact between parent bone and the implant.

Material & methods

In six Labrador dogs, premolars and first molars were extracted bilaterally in the mandible. After 3 months of healing, mucoperiosteal full‐thickness flaps were elevated and the premolar area of the alveolar bony crest was selected. Three recipient sites were prepared to place three implants. One implant was used as control. The other two were placed in recipient sites which left a circumferentially and periapical prepared defect of 0.7 mm (small) and 1.2 mm (large), respectively. All implants were stabilized with passive fixation plates to maintain the implants stable and without any contact with the implant bed. After 3 months of submerged healing, the animals were sacrificed. Ground sections were prepared and analyzed histomorphometrically.

Results

The BIC% was 5.3% and 0.3% for implants placed in small and large defect sites, respectively, whereas it was 46.1% for control implants. The differences were statistically significant. The width of the residual defects was 0.4 and 0.5 mm at the small and large defects, respectively. An approximately 0.09 mm layer of dense connective tissue (DCT) rich in fibers and fibroblast‐like cells was observed adherent to the implant surfaces. The percentage of implant surface covered by DCT was 92.8% and 95.6% at the small and large defects, respectively.

Conclusion

Osseointegration was observed at the test sites, and the dimensions of the defects influenced the outcomes. However, the degree of osseointegration at both small and large defects was very low compared with the control sites.
Suspension and Air Plasma‐Sprayed Ceramic Thermal Barrier Coatings with High Infrared Reflectance
Authors: Stuke A. , Kassner H. , Marqués J.‐L. , Vassen, R. , Stöver D. , Carius R.
Published: February 2012

Yttria partially stabilized zirconia (YSZ) coatings are widely used for thermal barrier coatings (TBCs) to increase operating temperature of gas turbines. In the wavelength range where most of the radiation by walls and combustion gas is emitted within the gas turbine YSZ is semitransparent leading to increasing radiation heat flows into the components at increasing service temperatures. The objective of this work is to optimize the diffuse reflectance of plasma‐sprayed TBCs by improving the coating microstructure such that the reflectance of radiation is increased. As a result, a more efficient thermal screening of the underlying metallic substrate is achieved. In this work, air plasma‐sprayed and suspension plasma‐sprayed (SPS) coatings of 7% YSZ using powder of different grain size distributions and different spray parameters were deposited. The reflectance and transmittance has been investigated in the wavelength range from 0.3 to 2.5 μm. The SPS‐coatings showed the highest reflectance up to 94% at 1.5 μm wavelength. In addition, the scattering and absorption coefficients of the sprayed TBCs calculated with the Kubelka–Munk two flux model showed strong correlation with the measured porosity. By improving the microstructure, we were able to reduce thermal conductivity while increasing scattering of radiation, resulting in lower heat flow and lower temperature at the metallic substrate. These results are strengthened by numerical calculations.
Laser Machining and Functional Applications of Glass‐Ceramic Materials
Authors: Sola Daniel , Peña Jose I.
Published: February 2012

In this work a study of glass‐ceramic laser machining and some functional applications are presented. Firstly, both the effect produced by the machining method as well as how the modification of the reference position influence the machining results have been studied. Secondly, blind holes and special shape cross‐section blind holes have been created for functional purposes. A Q‐switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse‐widths in the nanosecond range has been used. Morphology, depth, and volume obtained by machining grooves have been studied. The variation in the ablation yield when the position of the surface to be machined is modified has also been studied. The composition and microstructure of the machined areas have been described and discussed and thermal tests have been performed to check if the objectives of the functional applications have been achieved.
Molecular Docking Studies of Novel Palmitoyl‐ligands for Cyclooxygenase‐2
Authors: Bhagavat Raghu , Saqib Asma , Karigar Chandrakant
Published: February 2012

An in silico approach was adopted to identify potential cyclooxygenase‐2 inhibitors through molecular docking studies. The in vivo studies indicated that synthetic palmitoyl derivatives of salicylic acid, para amino phenol, para amino benzoic acid, and anthranilic acid possessed significant pharmacological activities like anti‐inflammatory, analgesic, and antipyretic activities. None of the tested substances produced any significant gastric lesions in experimental animals. In an attempt to understand the ligand–protein interactions in terms of the binding affinity, the above synthetic molecules were subjected to docking analysis using AutoDock. The palmitoyl derivatives palmitoyl anthranilic acid, palmitoyl para amino benzoic acid, palmitoyl para amino phenol, and palmitoyl salicylic acid showed better binding energy than the known inhibitor diclofenac bound to 1PXX. All the palmitoyl derivatives made similar interactions with the binding site residues of cyclooxygenase‐2 as compared to that of the known inhibitor. Thus, structure‐based drug discovery approach was successfully employed to identify some promising pro‐drugs for the treatment of pain and inflammation.
Chemical Components in Extracts from Plastrum Testudinis with Proliferation‐Promoting Effects on Rat Mesenchymal Stem Cells
Authors: Wang Ting‐Ting , Chen Wei , Zeng He‐Ping , Chen Dong‐Feng
Published: February 2012

Plastrum Testudinis (PT) is often used as an important traditional Chinese medicine to treat bone diseases in China for centuries. To identify active components of PT involved in promoting proliferation of MSCs, PT was extracted with ethyl acetate and separated by silica gel column chromatography with gradient elution. Sixteen (Ts‐1 ∼ 16) components were obtained, which were biologically evaluated by MTT assay and flow cytometry on the proliferation of rat marrow‐derived mesenchymal stem cells (rMSCs). Results indicated that Ts‐12 could induce the proliferation compared with control group (p < 0.05), while Ts‐4 exhibited inhibitive effect. The chemical components of PT which regulated the proliferation of rMSCs were investigated by Gas Chromatography‐Mass Spectrometry (GC‐MS), HPLC, and nine standard compounds. The experimental results suggested that palmitic acid methyl ester and cholesterol myristate, which identified from Ts‐12, possessed proliferative activity while stearic acid found in Ts‐4 showed inhibition.
The contribution of plant species with a steady‐state flowering phenology to native bee conservation and bee pollination services
Authors: PETERS VALERIE E. , CARROLL C. RONALD , COOPER ROBERT J. , GREENBERG RUSSELL , SOLIS MANUEL
Published: February 2012

Abstract.  1. Neotropical organisms have evolved in an environment of relatively low temporal variation in food availability, but when neotropical forests are converted to agriculture, the temporal patchiness of food resources is increased. Plant species with a continuous (i.e. steady‐state) flowering/fruiting phenology are unique to the tropics and may more evenly distribute food resources temporally in agroecosystems.

2. Here, we test the effects of an experimentally planted supplemental steady‐state floral resource, Hamelia patens Jacq., on bee diversity and pollination services in coffee agroforests. In addition, we evaluate effects of the steady‐state resource during low‐density and mass coffee blooms.

3. Malaise trap data indicated that bee species density was significantly higher in coffee agroforests with the supplemental steady‐state floral resources [11.89 ± 1.62 (SE)] compared to those without (8.88 ± 1.10).

4. The steady‐state floral resource had a negative impact on native bee visits to coffee flowers and a positive impact on Apis mellifera visits to coffee flowers (e.g. during low‐density blooms agroforests with steady‐state resources had 76% fewer native bee and 130% more A. mellifera visits to coffee flowers). Although coffee initial fruit set rates were higher across all agroforests during low‐density blooms (0.74 ± 0.03) compared to the mass bloom (0.59 ± 0.03), steady‐state floral resources did not affect initial fruit set rates (Z = −1.05, P = 0.29).

5. Our results suggest that plants with a steady‐state phenology can provide more reliable resources for bees, supporting the conservation of wild bees in agroforests. However, steady‐state flowering may draw native bees away from the focal crop, especially during low‐density flowering.
Homeopaths attempt to salvage a positive result from treatment failure in an underpowered trial
Authors: Vagg M
Published: February 2012

Brien S, Lachance L, Prescott P, McDermott C, Lewith G.

Homeopathy has clinical benefits in rheumatoid arthritis patients that are attributable to the consultation process but not the homeopathic remedy: a randomized controlled clinical trial.

Rheumatology 2011; 50: 1070–82.
Homeopathic Plumbum metallicum is ineffective for lead toxicity in a fair trial
Authors: Vagg M
Published: February 2012

Padilha RQ, Riera R, Atallah AN.

Homeopathic Plumbum metallicum for lead poisoning: a randomized clinical trial.

Homeopathy 2011; 100: 116–21.
Acupuncture for osteoarthritis of the knee
Authors: Marcus DM
Published: February 2012

Miller E, Maimon Y, Rosenblatt Y et al.

Delayed effect of acupuncture treatment in OA of the knee: a blinded, randomized, controlled trial.

Evid Based Complement Altern Med 2011; Article ID 792975. doi:10.1093/ecam/nen080
Ear acupuncture for migraine
Authors: Yeung K Simon , Cassileth BR
Published: February 2012

Allais G, Romoli M, Rolando S, Airola G, Castagnoli Gabellari I, Allais R, Benedetto C.

Ear acupuncture in the treatment of migraine attacks: a randomized trial on the efficacy of appropriate versus inappropriate acupoints.

Neurol Sci 2011; 32: S173–S5.
A Procedure to Include the Additional Fatigue Effects of Thermal Gradients in a B31.1 Butt Weld of Dissimilar Metals and Welding End Transition of Similar Metals for Design and Plant Life Extension
Authors: Creates David H.
Published: February 2012

Fatigue evaluation in B31.1-2007 is currently done in accordance with para. 102.3.2 and generally considers only the stresses due to displacement load ranges and other cyclic loads. Yet fatigue damage is also occurring due to thermal gradients which are not considered. To exacerbate and complicate this additional type of fatigue damage, power plant design pressures and temperatures are rising, new materials are being introduced, pipes and attached components are becoming increasingly thick, and owners are requiring power plants to heat-up and cool-down at faster rates. Also, power plant owners are more and more interested in extending the life of power plants beyond their original design life. Although the fatigue design of ASME nuclear Class 1 piping components has long required thermal gradients to be considered, no attempt has been made to incorporate this knowledge into the B31.1 Power Piping Code (other than Creates, D. H., 2009, “A Procedure to Evaluate a B31.1 Welding End Transition Joint to Include the Fatigue Effects of Thermal Gradients for Design and Plant Life Extension,” PVP2009-77148, Proceedings of the ASME 2009 Pressure Vessels and Piping Conference, Volume 3, Design and Analysis, A. Segall, ed., ASME, New York, PVP-Vol. 3, pp. 101–110). To address this pressing need in today’s power plant environment this paper now provides a fully comprehensive methodology for assessing an “as-welded” Butt weld of dissimilar metals and a Welding End Transition (B31.1-2007, Fig. 127.4.2) of similar metals to include the additional fatigue effects of thermal gradients calculated in accordance with ASME Section III-2007 Subarticle NB-3600. The disadvantage of this approach is that the conservatism in these calculations may produce unacceptable results. In that case, this assessment is a warning that something else needs to be done by way of monitoring, modifying the design or the thermal operation, or performing a more rigorous evaluation. The advantage of this methodology is that it maintains the traditional B31.1 approach to fatigue with the same limit of SA except that there is now an additional term, STG, to account for the fatigue contribution due to thermal gradients. Considering the effects of thermal gradients in this way will further help to preserve the integrity of the piping pressure boundary and consequently, the safety of personnel in today’s power plants and into the future.
Robust Thermal Management for Embedded CPU and GPUs in Displays
Authors: Kim Sung Ki , Kan Woo Young , Kim Sang Hak , Tan Vincent , Refai-Ahmed Gamal , Merrikh Ali Akbar
Published: February 2012

Digital signage systems are large format displays that are typically installed in public areas for advertisement and informative publications. This emerging technology is considered as a major category in the large format display market. In general, a digital signage system consists of a flat panel display consisting of high brightness screen and operation circuits. Also, special features of high performance embedded computing system exist in very small form factors. Such products, however, are accompanied with high heat dissipation of the internal components and are usually exposed to very harsh environments for more frequent exposure to customers. Also the installation schemes of the products vary for different objectives, and a robust thermal design is required to guarantee the system reliability considering corner scenarios within the design space. The objective of the present study is to investigate the effect of installation environment on the thermal performance of a display assembly resembling a digital signage system. Design criteria for a proper thermal management scheme are proposed. The thermal characteristics of a digital signage system are presented in various operation conditions and each thermal design parameter is discussed thoroughly to ensure the reliability requirements of the digital signage system are met.
Erosion Behavior of Plasma Nitriding Stainless Steel by Molten Sn-Ag-Cu Lead-Free Solder
Authors: Matsubara Naoya , Shohji Ikuo , Kuwahara Hideyuki
Published: February 2012

The erosion behavior of plasma nitriding SUS304 stainless steel by molten lead-free solder was examined. Plasma nitriding treatment was conducted to the surface of SUS304 steel. The thickness of the nitriding layer was approximately 17 μm. The layer mainly consists of Fe4N, CrN and Cr2N. Erosion of nitriding SUS304 stainless steel was observed after erosion test with molten Sn-3Ag-0.5Cu (mass%) solder at 450°C for 100 h. On the basis of the result of microstructure observation, it was found that Sn diffusion into the nitrided layer occurred in non eroded area. The result shows that Sn diffusion into the nitrided layer induces erosion of plasma nitriding stainless steel.
Study of the Thermomechanical Inelastic Energy Response of Backward Compatible Solder Joints Made With Sn-3.8Ag-0.7Cu versus Reballed Sn37.0Pb Components
Authors: Renta Lorraine M. , Valentin Ricky , Quintero Pedro , Ma David , Hovland Alan
Published: February 2012

Conflicting results in reliability tests for backward compatible and Pb-free soldered assemblies has motivated RoHS-exempted industries to practice reballing. Reballing is the name given to the process of removing Pb-free solder balls from the copper (Cu) pads of the Ball Grid Array (BGA) components received through the supply chain and replacing them with SnPb solder balls. Recent studies on the subject of reballing have shown the possibility that the removed Pb-free solder ball leaves behind some intermetallic remnants of the Pb-free solder alloy and the Cu from the pads. A modeling approach based on physics of failure (PoF) is presented that quantifies the interactions between different thermal cycles applied to reballed Ball Grid Arrays (BGA) with remnants of the Pb-free solder alloy on the Cu pads. These resulting interactions are compared to backward compatible Sn-3.8 Ag-0.7Cu (SAC) balls soldered with eutectic SnPb paste for the same thermal cycles. For the latter, the risk of having improper mixing during the assembly process is also studied. The approach is formulated at the microscale, incorporating physical mechanisms of the intermetallics created with Cu, and at the macroscale, capturing the creep phenomenon of the bulk solder as dominant failure driver. Simulation results show that the reballed cases have higher inelastic energy density per cycle averaged over damage volume near the copper pads and that the inelastic energy density is higher across the bulk of the improperly mixed backward compatible solder balls when compared to properly mixed backward compatible solder balls. The results of this study permit extrapolation of laboratory results to field life predictions and to explore the design of accelerated re-balled or backward compatible BGA tests that relate better to application-specific usage environments.
High Temperature Die Attach by Low Temperature Solid-Liquid Interdiffusion
Authors: Rodriguez Rogie I. , Ibitayo Dimeji , Quintero Pedro O.
Published: February 2012

There is a need for electromechanical devices capable of operating in high temperature environments (>200°C) for a wide variety of applications. Today’s wide-bandgap semiconductor based power electronics have demonstrated a potential of operating above 400°C, however they are still limited by packaging. Our group has been conducting research in novel interconnect technologies to develop reliable electronic packaging for high temperature environments. Among the most promising alternative is the Au-Sn eutectic solder (80 wt.% Au - 20 wt.% Sn), which have been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this metallurgical system is still limited to ∼250°C owing to its melting temperature of 280°C. Therefore, a higher temperature resistant system is much needed, but without affecting the current processing temperature of ∼325°C typically exhibited in most high temperature Pb-Free solders. This paper presents the development and characterization of a fluxless die attach soldering process based on gold enriched solid liquid inter-diffusion (SLID). A low melting point eutectic Au-Sn was deposited in the faces of two substrates, followed by the deposition of a subsequent layer of high melting point material, gold in this instance, in one of the substrates. Deposition of all materials was performed using Jet Vapor Deposition (JVD) equipment where thicknesses were controlled to achieve specific compositions in the mixture. Sandwiched coupons where isothermally processed in a vacuum reflow furnace. Scanning electron microscopy (SEM) was employed to reveal the microstructural evolution of the samples in order to study the interfacial reactions of this fluxless bonding process. EDS analysis was used to identify the intermetallic formation and to characterize the joint in an attempt to study the kinetics of this diffusion couple. Post-processed samples confirmed the inter-diffusion mechanism evidenced by the formation of sound joints between the two substrates. As expected, it was observed that the Au was dissolved into the eutectic Au-Sn as the reflow time and temperature were increased.
Non-Contact and Remote Measurement Method of the Change of the Electrical Conductivity of Carbon Nanotubes-Dispersed Resin Under Strain
Authors: Ohashi Yusuke , Suzuki Yusuke , Ohnishi Masato , Suzuki Ken , Miura Hideo
Published: February 2012

A novel noncontact stress/strain measurement method has been developed for monitoring dynamic strain on the surface of various structures under operation. The change of electrical properties of carbon nanotubes (CNT)-dispersed resin was investigated to evaluate the possibility of its application to a highly sensitive and remote strain sensor without interconnections. It was validated that the electrical impedance of the CNT-dispersed resin changes drastically at frequencies higher than 500 kHz under strain. Application of microwave showed the possibility of the non-contact measurement of the change of electrical impedance of the resin under dynamic load by measuring the change of its reflectivity obtained from the surface of the resin. A theoretical method to estimate the change of the intensity of the microwave reflected from the resin was discussed based on the microwave theory. The change of the reflectance under tensile strain of 20% was calculated by the method using the measured change of the impedance of the resin under the frequency range between 1Hz and 10MHz. As a result, the maximum change of the reflectance was estimated as 1.2% at 630 kHz. Therefore, it is possible to realize remote monitoring of the strain field on the surface of various products under operation by applying the CNT-dispersed resin.
Design and Implementation of a Multiple-Beam Tuning-Fork Gyroscope
Authors: Wang Ren , Cheng Peng , Xie Fei , Hao Zhili , Young Darrin
Published: February 2012

This paper presents the design, fabrication, and experimental results of a multiple-beam tuning-fork gyroscope (MB-TFG). Based on a numerical model of thermoelastic damping, a multiple-beam tuning-fork structure is designed with high Quality factors (Qs) in its two operation modes. A simple mask that defines the device through trenches is employed to implement this MB-TFG design on silicon-on-insulator wafers. The highest measured Qs of the fabricated MB-TFGs in vacuum are 255,000 in the drive-mode and 103,000 in the sense-mode, at a frequency of 15.7kHz. Under a frequency difference of 4Hz between the two modes (operation frequency is 16.8kHz) and a drive-mode vibration amplitude of 3.0μm, the measured rate sensitivity is 80μVPP/°/s with an equivalent impedance of 2.5MΩ. The calculated overall rate resolution of this device is 0.377hr°/√Hz.
Effect of Design Parameters on Drop Test Performance of Wafer Level Chip Scale Packages (WLCSP)
Authors: Tumne Pushkraj , Venkatadri Vikram , Kudtarkar Santosh , Delaus Michael , Santos Daryl , Havens Ross , Srihari Krishnaswami
Published: February 2012

Today’s consumer market demands electronics that are smaller, faster and cheaper. To cater to these demands, novel materials, new designs, and new packaging technologies are introduced frequently. Wafer Level Chip Scale Package (WLCSP) is one of the emerging package technologies that have the key advantages of reduced cost and smaller footprint. The portable consumer electronics are frequently dropped; hence the emphasis of reliability is shifting towards study of effects of mechanical shock loading increasingly. Mechanical loading typically induces brittle fractures (also known as intermetallic failures) between the solder bumps and bond pads at the silicon die side. This type of failure mechanism is typically characterized by the board level drop test. WLCSP is a variant of the flip-chip interconnection technique. In WLCSPs, the active side of the die is inverted and connected to the PCB by solder balls. The size of these solder balls is typically large enough (300μm pre-reflow for 0.5mm pitch and 250μm pre-reflow for 0.4mm pitch) to avoid use of underfill that is required for the flip-chip interconnects. Several variations are incorporated in the package design parameters to meet the performance, reliability, and footprint requirements of the package assembly. The design parameters investigated in this effort are solder ball compositions with different Silver (Ag) content, backside lamination with different thickness, WLCSP type –Direct and Re-Distribution Layer (RDL), bond pad thickness, and sputtered versus electroplated Under Bump Metallurgy (UBM) deposition methods for 8×8, 9×9, and 10×10 array sizes. The test vehicles built using these design parameters were drop tested using JEDEC recommended test boards and conditions as per JESD22-B11. Cross sectional analysis was used to identify, confirm, and classify the intermetallic, and bulk solder failures. The objective of this research was to quantify the effects and interactions of WLCSP design parameters through drop test. The drop test data was collected and treated as a right censored data. Further, it was analyzed by fitting empirical distributions using the grouped and un-grouped data approach. Data analysis showed that design parameters had a significant effect on the drop performance and played a vital role in influencing the package reliability.
An Investigation of Power Migration Policies for Many-Core Processors to Manage On-Chip Thermal Profile
Authors: Gupta Man Prakash , Cho Minki , Mukhopadhyay Saibal , Kumar Satish
Published: February 2012

Transition from single core to multicore technology has brought daunting challenge for thermal management of microprocessor chips. The issue of power dissipation in next generation chip will be far more critical as further transition from multicore to many-core processors is soon to be expected. It is very important to obtain uniform on-chip thermal profile with low peak temperature for improved performance and reliability of many-core processors. In this paper, a proactive thermal management technique called ‘power multiplexing’ is explored for many-core processors. Power multiplexing involves redistribution of locations of power dissipating cores at regular time intervals to obtain uniform thermal profile with low peak temperature. Three different migration policies namely random, cyclic and global coolest replace have been employed for power multiplexing and their efficacy in reducing the peak temperature and thermal gradient on chip is investigated. A comparative study of these policies has been performed enlisting their limits and advantages from the thermal and implementation perspective considering important relevant parameters such as migration frequency. For a given migration frequency, global coolest replace policy is found to be the most effective among the three policies considered as this policy leads to 10 °C reduction in peak temperature and 20 °C reduction in maximum spatial temperature difference on a 256 core chip. Proximity of active cores or power configuration on chip is characterized by a parameter ‘proximity index’ which emerges as an important parameter to represent the spatial power distribution on a chip. Global coolest replace policy optimizes the power map on chip taking care of not only the proximity of active cores but also the finite-size effect of chip and the 3D system of electronic package leading to almost uniform thermal profile on chip with lower average temperature.
Improvement of Heat Transfer Performance of Loop Heat Pipe for Electronic Devices
Authors: Takamatsu Tomonao , Hisano Katsumi , Iwasaki Hideo
Published: February 2012

In this paper is presented the results on performance of the cooling model using Loop Heat Pipe (LHP) system. In recent years, ever-ending demand of high performance CPU led to a rapid increase in the amount of heat dissipation. Consequently, thermal designing of electronic devices need to consider some suitable approach to achieve high cooling performance in limited space. Heat Pipe concept is expected to serve as an effective cooling system for laptop PC, however, it suffered from some problems as follows. The heat transport capability of conventional Heat Pipe decreases with the reduction in its diameter or increase in its length. Therefore, in order to use it as cooling system for future electronic devices, the above-mentioned limitations need to be removed. Because of the operating principle, the LHP system is capable of transferring larger amount of heat than conventional heat pipes. However, most of the LHP systems suffered from some problems like the necessity of installing check valves and reservoirs to avoid occurrence of counter flow. Therefore, we developed a simple LHP system to install it on electronic devices. Under the present experimental condition (the working fluid was water), by keeping the inside diameter of liquid and vapor line equal to 2mm, and the distance between evaporator and condenser equal to 200mm, it was possible to transport more than 85W of thermal energy. The thickness of evaporator was about 5mm although it included a structure to serve the purpose of controlling vapor flow direction inside it. Successful operation of this system at inclined position and its restart capability are confirmed experimentally. In order to make the internal water location visible, the present LHP system is reconstructed using transparent material. In addition, to estimate the limit of heat transport capability of the present LHP system using this thin evaporator, the air cooling system is replaced by liquid cooling one for condensing device. Then this transparent LHP system could transport more than 100W of thermal energy. However, the growth of bubbles in the reserve area with the increase in heat load observed experimentally led to an understanding that in order to achieve stable operation of the LHP system under high heat load condition, it is very much essential to keep enough water in the reserve area and avoid blocking the inlet with bubbles formation.
Fatigue Life and Fracture Behavior of Micro Size Sn-Ag-Cu Solder Joint
Authors: Naoki Tashiro , Kariya Yoshiharu , Kanda Yoshihiko
Published: February 2012

The influence of the joint size on low cycle fatigue characteristic of Sn-Ag-Cu has been investigated by a micro size joint specimen fabricated using solder balls. Although the effect of joint size on crack initiation life is not obvious at 298K, the reduction of the joint size changes the cyclic strain hardening nature and the fracture behavior that induces the life reduction at 398K. With a decrease in size, the failure mechanism transforms from a transgranular fracture to an intergranular fracture at the high energy grain boundary that is formed by high angle boundary formation following dynamic recovery in whole of joint. Therefore, the failure life is greatly reduced as a complete failure occurs simultaneously with the crack initiation at the grain boundaries. This is more remarkable at higher temperatures.
Reliability Evaluation of Electronic Devices Under Considering the Actual Use Conditions
Authors: Liu Shilin , Yu Qiang , Pecht Michael
Published: February 2012

Semiconductor component manufacturers supply to different product manufacturers in a wide range of market segments, for different end use applications. The goal of electronic component qualification is to demonstrate component reliability under operating conditions in the end product configuration. While a manufacturer may have successfully qualified an individual component, operating stresses due to surrounding components or the system can decrease individual component reliability. Not accounting for these operating stresses resulting from other components or the system will lead to lower life than anticipated. Using a case study, the authors demonstrate how the fatigue life of a chip component mounted on a PCB is affected by powered components on the board in close proximity.
Thermal Characterization of Non-Isolated DC to DC Convertor
Authors: Chakravorty Shiladitya , Sammakia Bahgat , Calmidi Varaprasad
Published: February 2012

Improved performance of semiconductor devices in recent years has resulted in consequent increase in power dissipation. Hence thermal characterization of components becomes important from an overall thermal design perspective of the system. This study looks at a high performance non-isolated point of load power module (a DC to DC converter) meant for advanced computing and server applications. Thermal characteristics of the module were experimentally analyzed by placing the power module on a bare test board (with no insulation) inside a wind tunnel with thermocouples attached to it. There were three devices on this module that dissipate power. There were two FETs (Field Effect Transistors) and an inductor which can be considered as sources. The consolidated power dissipation from the module was calculated by measuring the input voltage and input current while keeping the output voltage and current constant. Temperatures at various points on the module and the test card were recorded for different air flow velocities and overall power dissipation. Subsequently this set up was numerically analyzed using a commercially available computational fluid dynamics (CFD) code with the objective of comparing the results with experimental data previously obtained.
Potential-Flow Modeling for Data Center Applications
Authors: Healey Christopher M. , VanGilder James W. , Sheffer Zachary R. , Zhang Xuanhang Simon
Published: February 2012

Potential-flow-based airflow and heat transfer models have been proposed as a computationally efficient alternative to the Navier-Stokes Equations for predicting the three-dimensional flow field in data center applications. These models are simple, solve quickly, and capture much of the fluid flow physics, but ignore buoyancy and frictional effects, i.e., rotationality, turbulence, and wall friction. However, a comprehensive comparison of the efficiency and accuracy of these methods versus more sophisticated tools, like CFD, is lacking. The main contribution of this paper is a study of the performance of potential-flow methods compared to CFD in eight layouts inspired by actual data center configurations. We demonstrate that potential-flow methods can be helpful in data center design and management applications.
Single-Phase Microchannel Cooling for Stacked Single Core Chip and DRAM
Authors: Chauhan Anjali , Sammakia Bahgat , Ghose Kanad , Refai-Ahmed Gamal , Agonafer Dereje
Published: February 2012

The stacking of processing and memory components in a three-dimensional (3D) configuration enables the implementation of processing systems with small form factors. Such stacking shortens the interconnection length between processing and memory components to dramatically lower the memory access latencies, and contributes to significant improvements in the memory access bandwidth. Both of these factors elevate overall system performance to levels that are not realizable with prevailing and other proposed solutions. The shorter interconnection lengths in stacked architectures also enable the use of smaller drivers for the interconnections, which in turn reduces interconnection-level energy dissipations. On the down side, stacking of processing and memory components introduces a significant thermal management challenge that is rooted in the high thermal resistance of stacked designs. This paper examines and evaluates three distinct solutions that address thermal management challenges in a system that stacks DRAM components onto a processing core. We primarily focus on three different configurations of a microchannel-based single-phase liquid cooling system with a traditional air-cooled heat sink. Our evaluations, which are intended to study the limits of each solution, assume a uniform power dissipation model for the processor and accounts for the thermal resistance offered by the thermal interface material (TIM), the interconnect layer, and through-silicon vias (TSVs). The liquid-cooled microchannel heat sink shows more promising results when integrated into the package than when added to the microprocessor package from outside.
Thermo-Mechanical Fatigue Life Prediction of Orthotropic Composite Pin Fin Heat Sinks for Electronic Packaging
Authors: Pashah Sulaman , Arif Abul Fazal M.
Published: February 2012

Heat sinks are used in modern electronic packaging system to enhance and sustain system thermal performance by dissipating heat away from IC components. Pin fins are commonly used in heat sink applications. Conventional metallic pins fins are efficient in low Biot number range whereas high thermal performance can be achieved in high Biot number regions with orthotropic composite pin fins due to their adjustable thermal properties. However, several challenges related to performance as well as manufacturing need to be addressed before they can be successfully implemented in a heat sink design. A heat sink assembly with metallic base plate and polymer composite pin fins is a solution to address manufacturing constraints. During the service life of an electronic packaging, the heat sink assembly is subjected to power cycles. Cyclic thermal stresses will be important at the pin-fin and base-plate interface due to thermal mismatch. The cyclic nature of stresses can lead to fatigue failure that will affect the reliability of the heat sink and electronic packaging. A finite element model of the heat sink is used to investigate the thermal stress cyclic effect on thermo-mechanical reliability performance. The aim is to assess the reliability performance of the epoxy bond at the polymer composite pin fins and metallic base plate interface in a heat-sink assembly.
Combined Temperature and Humidity Effects on MEMS Vibratory Gyroscope Sensor
Authors: Patel Chandradip , McCluskey Patrick
Published: February 2012

Reliability and long term stability are the greatest challenges for commercialization of MEMS gyroscopes. Their vast use in different applications that required MEMS gyroscopes to function from medium to harsh environments make necessary to evaluate the performance of MEMS gyroscope under those conditions. This paper focuses on the combined long term effects of temperature and humidity on the performance of MEMS vibratory gyroscope. Performance of the MEMS gyroscope was evaluated over time by conducting temperature humidity bias (THB) test on a COTS (commercial off-the-shelf) single axis MEMS vibratory gyroscope having an operating temperature range from −40°C to +85°C. The gyroscope sensors were exposed to 60°C and 90%RH (Relative Humidity) for 500 hours. Six single axis gyroscopes were tested, three with in-situ device calibration and three without in-situ device calibration. Out of three MEMS vibratory gyroscopes tested without in-situ device calibration, it was observed that samples had minimum and maximum in-situ zero rate output (ZRO) drift of 1.3°/s and 2.2°/s respectively over 500 hours. These drifts were disappeared when gyroscope sensors were tested after six months by keeping at room condition. Other three single axis gyroscopes were tested in the same chamber with in-situ device calibration which didn’t show any major performance ZRO drift.
Ridge Regression Based Development of Norris-Landzberg Acceleration Factors and Goldmann Constants for Leadfree Electronics
Authors: Lall Pradeep , Arunachalam Dinesh , Suhling Jeff
Published: February 2012

Goldmann Constants and Norris-Landzberg acceleration factors for lead-free solders have been developed based on ridge regression models (RR) for reliability prediction and part selection of area-array packaging architectures under thermo-mechanical loads. Ridge regression adds a small positive bias to the diagonal of the covariance matrix to prevent high sensitivity to variables that are correlated. The proposed procedure proves to be a better tool for prediction than multiple-linear regression models. Models have been developed in conjunction with Stepwise Regression Methods for identification of the main effects. Package architectures studied include, BGA packages mounted on copper-core and no-core printed circuit assemblies in harsh environments. The models have been developed based on thermo-mechanical reliability data acquired on copper-core and no-core assemblies in four different thermal cycling conditions. Packages with Sn3Ag0.5Cu solder alloy interconnects have been examined. The models have been developed based on perturbation of accelerated test thermo-mechanical failure data. Data has been gathered on nine different thermal cycle conditions with SAC305 alloys. The thermal cycle conditions differ in temperature range, dwell times, maximum temperature and minimum temperature to enable development of constants needed for the life prediction and assessment of acceleration factors. Norris-Landzberg acceleration factors have been benchmarked against previously published values. In addition, model predictions have been validated against validation datasets which have not been used for model development. Convergence of statistical models with experimental data has been demonstrated using a single factor design of experiment study for individual factors including temperature cycle magnitude, relative coefficient of thermal expansion, and diagonal length of the chip. The predicted and measured acceleration factors have also been computed and correlated. Good correlations have been achieved for parameters examined.
KL Transform and Neural-Net Based Framework for Failure Modes Classification in Electronics Subjected to Mechanical-Shock
Authors: Lall Pradeep , Gupta Prashant , Goebel Kai
Published: February 2012

Electronic systems under extreme shock and vibration environments including shock and vibration may sustain several failure modes simultaneously. Previous experience of the authors indicates that the dominant failure modes experienced by packages in a drop and shock frame work are in the solder interconnects including cracks at the package and the board interface, pad cratering, copper trace fatigue, and bulk-failure in the solder joint. In this paper, a method has been presented for failure mode classification using a combination of Karhunen Loe´ve transform with parity-based stepwise supervised training of a perceptrons. Early classification of multiple failure modes in the pre-failure space using supervised neural networks in conjunction with Karhunen Loe´ve transform is new. Feature space has been formed by joint time frequency analysis. Since the cumulative damage may be accrued under repetitive loading with exposure to multiple shock events, the area array assemblies have been exposed to shock and feature vectors constructed to track damage initiation and progression. Error Back propagation learning algorithm has been used for stepwise parity of each particular failure mode. The classified failure modes and failure regions belonging to each particular failure modes in the feature space are also validated by simulation of the designed neural network used for parity of feature space. Statistical similarity and validation of different classified dominant failure modes is performed by multivariate analysis of variance and Hoteling’s T-square. The results of different classified dominant failure modes are also correlated with the experimental cross sections of the failed test assemblies. The methodology adopted in this paper can perform real-time fault monitoring with identification of specific dominant failure mode and is scalable to system level reliability.