bluuebunny/crossref_metadata_2025 huggingface dataset:
Scrotal involvement in childhood Henoch‐Schönlein purpura
Authors: Ha Tae‐Sun , Lee Jin‐Seok
Published: April 2008

Aim: Henoch‐Schönlein purpura (HSP) is a common childhood systemic vasculitis involving the skin, gastrointestinal tract, joint, kidneys and even scrotum.

Methods: We retrospectively reviewed the clinical and laboratory data of 120 male patients with HSP and also evaluated the risk factors for scrotal involvement and the relation between scrotal involvement and other clinical features. Twenty‐six out of 120 boys (21.7%) diagnosed with HSP had scrotal involvement.

Results: Scrotal symptoms manifested as swelling in 88.5% and pain (or tenderness) in 69.2% of HSP patients with scrotal involvement. Neurologic symptoms, mainly headache and localized edema among various manifestations and high serum C3 level of laboratory profiles were more frequently observed in scrotal‐involved group than in those of non‐involved group. However, there was no difference in the outcomes of scrotal symptoms according to therapeutic modalities and the occurrence of scrotal involvement had no correlation with renal involvement from acute to chronic phase.

Conclusions: We found that neurologic symptoms, localized edema and high serum C3 level show a significant relation with scrotal involvement in male HSP patients. Because scrotal involvement in male HSP patients is not rare, the accurate early diagnosis of HSP is mandatory by the early notification of purpura and imaging evaluations in order to avoid unnecessary procedures.
Identification of a novel compound heterozygote SCO2 mutation in cytochrome c oxidase deficient fatal infantile cardioencephalomyopathy
Authors: Knuf M , Faber J , Huth R G , Freisinger P , Zepp F , Kampmann C
Published: April 2008

Fatal infantile cardioencephalomyopathy (OMIM No. 604377) is a disorder of the mitochondrial respiratory chain and is characterised by neonatal progressive muscular hypotonia and cardiomyopathy because of severe Cytochrome c oxidase deficiency. Here we report a novel mutation in the Cytochrome c oxidase assembly gene SCO2 in an infant with fatal infantile cardioencephalomyopathy despite normal initial metabolic screening.

Conclusion: In newborns with unexplained muscular hypotonia and cardiomyopathy genetic testing of mitochondrial respiratory chain disorders might be helpful to establish a final diagnosis and guide treatment decisions.
Geographic variations in outcome of very low birth weight infants in Italy
Authors: Corchia Carlo , Orzalesi Marcello
Published: April 2008

Aim: A number of social and health aspects in Italy show remarkable geographic dishomogeneity. We investigated if this phenomenon involves the outcome of very low birth‐weight infants (VLBWI).

Methods: This is a multi‐centre nation‐based survey among all Italian NICUs. The number of VLBWI admitted to each NICU in 2001 by birth‐weight classes of 250 g, their inborn/outborn status and survival at discharge were registered through ad hoc questionnaires. The data were analysed for the whole country and for three geographic areas (North, Centre and South).

Results: A total of 4679 VLBWI in 125 units were surveyed (0.88% of live births in Italy in 2001). The median number of infants admitted was 34 per NICU (interquartile range 16,52), without significant differences among the three geographic areas. The inborn rate was 80.7% (86.5% in the North, 83.7% in the Centre and 74.6% in the South). The mortality rate was 19.6% (15.6% in the North, 19.3% in the Centre and 23.4% in the South). Adjusted relative risk of death between Southern and Northern regions was 1.48 (95% CI 1.30–1.68), and that between outborn and inborn infants was 1.20 (95% CI 1.04–1.37).

Conclusions: The differences in mortality among geographic areas suggest a state of socio‐sanitary deprivation in the Southern regions, as well as different models of organisation and quality of perinatal care.
Noninvasive treatment of bronchomalacia, successful ventilation of a severely ill infant
Authors: Aaseboe K , Berstad A K H , Skadberg B T
Published: April 2008

Noninvasive treatment of bronchomalacia. Successful ventilation of a severely ill infant.

Aim: To describe an effective treatment of a boy with bronchomalacia by noninvasive mechanical ventilation support.

Methods: We describe a case of a severely ill patient with bronchomalacia from the time he was born and until the age of five. Bi‐level positive airway pressure given through a specially adapted full face mask was used to treat his respiratory condition.

Result: Our patient responded well to the noninvasive treatment of bronchomalacia.

Conclusion: We found that noninvasive mechanical ventilation support is a low risk and highly effective treatment of infants and children with respiratory distress caused by bronchomalacia.
Resuscitation and ventilation strategies for extremely preterm infants: a comparison study between two neonatal centers in Boston and Stockholm
Authors: Vanpée Mireille , Walfridsson‐Schultz Ulrika , Katz‐Salamon Miriam , Zupancic John A.F. , Pursley DeWayne , Jónsson Baldvin
Published: April 2008

Aim: To evaluate if different resuscitation and ventilatory styles exist between two neonatal units, and if the less aggressive approach has a beneficiary effect on BPD outcome.

Method: Inborn infants delivered at a gestational age <28 weeks were retrospectively studied (Boston = 70 and Stockholm = 102). Data were collected from birth to discharge or to 40 weeks.

Results: The study groups were similar with regard to gestational age, birth weight, gender and CRIB score, whereas SNAPPE‐II score was greater in Stockholm and prenatal steroids were given less frequently in Boston. In Stockholm, continuous positive airway pressure (CPAP) was applied in the delivery room for 56% of the infants and the prevalence of infants not requiring intubation or mechanical ventilation (MV) during the first week of life was 22%. In Boston all infants were initially intubated. Subsequently, CPAP was used less often, and higher mean airway pressures (MAWPs) were applied during the first 4 weeks of life. Mortality and moderate/severe BPD at 36 weeks were similar; however, at 40 weeks oxygen supplementation was more frequent in Boston. Site was a predictor for moderate/severe BPD or death at 40 weeks.

Conclusion: Practice style differences exist and the less aggressive approach with more CPAP administration was successful. It did not decrease the risk for BPD at 36 weeks; however, at 40 weeks, fewer infants were on oxygen support, and a strong association was found between site, MAWP or MV with pulmonary morbidity indicating that CPAP could have a beneficiary role in outcome.
Iron status at 1 and 6 years versus developmental scores at 6 years in a well‐nourished affluent population
Authors: Gunnarsson B. S. , Thorsdottir I. , Palsson G. , Gretarsson S. J.
Published: April 2008

Aim: To examine the association between iron status at 1 and 6 years with development at 6 years.

Methods: In a longitudinal study of children (n = 77), iron status was measured at 1 and 6 years and the Icelandic Developmental Inventory, which evaluates children's motor and verbal development, was filled in by mothers near the children's sixth birthday.

Results: Children, iron‐deficient at 1 year (n = 10), had lower fine motor development scores at 6 years than non–iron‐deficient (n = 56) (46.7 ± 4.1 vs. 49.3 ± 2.0; p = 0.011). Fine motor scores were also lower in children with depleted iron stores at 1 year (n = 26) than non–iron‐depleted children (n = 40) (48.0 ± 3.3 vs. 49.5 ± 1.8; p = 0.045). Multiple regression analyses, with iron status indices at 6 years, showed that mean corpuscular volume along with male gender predicted significantly positively for expression (adj. R2= 0.15; p = 0.018; n = 73), while regression analyses, including iron status at 1 and 6 years, showed that haemoglobin at 6 years was positively associated with gross motor (adj. R2= 0.05; p = 0.038; n = 63).

Conclusions: In an affluent society, iron deficiency and depleted iron stores at 1 year may contribute to worse fine motor developmental scores at 6 years, while low mean corpuscular volume and haemoglobin at 6 years might affect subsequent expression and gross motor scores negatively.

Sponsorship: The Icelandic Research Council.
Swedish pre‐school children eat too much junk food and sucrose
Authors: Garemo M. , Lenner R. Arvidsson , Strandvik B.
Published: April 2008

Aim: To analyze dietary intake in healthy 4‐year‐old children.

Methods: Families from three Paediatric Health Care Centres in different socio‐economic areas in Göteborg completed 7‐day food records and questionnaires about socio‐economy.

Results: One hundred thirty two/153 completed the study, 49% of parents were university educated. Eighteen percent of children were overweight/obese. Energy intake was high; 67% had sucrose intake exceeding Nordic Nutrition Recommendations (NNR) but 36% had n‐3 fatty acid intake <0.5 energy percent. Significant negative correlations were found between sucrose and fat and between BMI and fat intake. Junk food supplied 24% of energy. Ninety‐two percent had low vitamin D intake, 70% low iron and 21% low calcium intake. Gruel, which was consumed by 28%, had a positive impact on micronutrient intake. Child care and mother's origin seemed to influence dietary intake.

Conclusion: In 4‐year olds from well‐educated urban families, 18% was overweight/obese. Total energy intake was above present NNR but lower than 20 years ago, when overweight was rare. Fat energy intake was negatively associated with BMI, and low n‐3 fatty acid intake was associated with higher body weight. In several aspects dietary intake was not optimal in the children.
The effects of smoking in pregnancy on factors influencing fetal growth
Authors: Ingvarsson Ragnar F , Bjarnason Anton O , Dagbjartsson Atli , Hardardottir Hildur , Haraldsson Asgeir , Thorkelsson Thordur
Published: April 2008

Aim: To evaluate the influence of maternal smoking during pregnancy on factors influencing fetal growth.

Methods: Thirty newborns of smoking mothers were prospectively compared with 60 newborns of non‐smoking mothers. Pre‐albumin, albumin, triglycerides, glucose, insulin, insulin‐like growth factor I, IGF binding protein 3, pH, lactic acid, erythropoietin and hemoglobin concentrations were measured in umbilical cord blood.

Results: Infants of smoking mothers had a significantly lower birth weight (3418 ± 533 vs. 3863 ± 503 g; p < 0.001), length (50.5 ± 2,6 vs. 52.3 ± 1.9 cm; p < 0.001) and head circumference (34.6 ± 1.8 vs. 35.8 ± 1.1 cm; p < 0.001) than controls. They also had significantly lower insulin (3.2 (2.0–4.9) vs. 5.8 (4.6–7.1) mU/L; p = 0.008), insulin‐like growth factor I (54.4 ± 32.5 vs. 93.8 ± 54.5 μg/L; p = 0.001) and IGF binding protein 3 (1664 ± 432 vs. 1943 ± 421 μg/L; p = 0.01) concentrations, than controls. Infants of smoking mothers also had significantly higher hemoglobin (167 ± 14 vs. 157 ± 13 g/L; p = 0.002) and erythropoietin (42.3 (25.1–72.4) vs. 26.3 (21.9–30.9) U/L; p = 0.03) than controls, but not pH or lactate concentrations. There was no significant difference in pre‐albumin, albumin, triglycerides and glucose concentrations.

Conclusions: Smoking during pregnancy causes symmetrical fetal growth impairment, possibly due to decreased oxygen transport to the fetus and decreased concentrations of fetal insulin, insulin‐like growth factor I and IGF binding protein 3.
Genetic association studies in VLBW infants exemplifying susceptibility to sepsis—recent findings and implications for future research
Authors: Härtel Christoph , Schultz Christian , Herting Egbert , Göpel Wolfgang
Published: April 2008

Context: In recent years, tremendous effort has been carried out to study the genetic basis of susceptibility to development, progression and severity of complex diseases and response to therapy. The ultimate goal of these investigations is to find new tools for prevention and treatment of these complex diseases, such as sepsis in very‐low‐birth‐weight (VLBW) infants. VLBW cohorts have a restricted clinical risk profile for the development of sepsis including immaturity of immune functions and antenatal/perinatal risk factors but also a significant event rate of sepsis within a short period of observational time. Therefore, prospective VLBW cohorts are advantageous for the investigation of candidate genetic risk factors of sepsis compared to adult cohorts. Furthermore, environmental factors are much better documented and highly controlled for VLBW infants in a standardized NICU setting compared to adult cohorts which are influenced by a variety of environmental risk factors, e.g. habits and comorbidities.

Objective: The aim of this review is to discuss the value and limitations of genetic association studies in VLBW infant cohorts exemplifying recent findings for genetic susceptibility to neonatal sepsis.

Data source: Published Medline articles reporting on studies of associations between genetic polymorphisms, neonatal sepsis and septic shock in VLBW infants.

Conclusions: Up‐to‐date, the classical approach to investigate the genetic component of susceptibility to sepsis in VLBW infants by means of twin and concordance studies has not been implemented yet. Regarding the interpretation of data from current genetic association studies, one should be aware of significant differences in cohort size, study design and definition of cases, controls and clinical end points. Furthermore, the contribution of genetic variants to susceptibility to sepsis may be specifically influenced by the immaturity of the immune response in VLBW infants, the selectivity of responsiveness to certain pathogens and the genotopyic/phenotypic variability of pathogens. We provide implications for the conduct and evaluation of future association studies with particular reference to methodological quality standards.
Haemolysis alters plasma flecainide levels in newborn infants
Authors: Vento M , Tudela B Fernández , Escrig R , Sáenz P , Sánchez A , Cano A
Published: April 2008

Refractory neonatal supra‐ventricular tachycardia may require the use of flecainide as anti‐arrhythmic. Close control of plasma levels is mandatory due to pro‐arrhythmic complications. However, inadvertent hemolysis during blood sampling may cause an increase in measured plasma flecainide concentrations. We conclude, therefore, that dosing of the drug should be always done with caution, and in case of suspected haemolysis plasma levels should be repeated with a new blood sample.
Nasal CPAP has become an indispensable part of the primary treatment of newborns with respiratory distress syndrome
Authors: Verder Henrik
Published: April 2008

Prenatal steroids, early nasal CPAP combined with early surfactant treatment followed by extubation to nasal CPAP, and if necessary mechanical ventilation is a very effective treatment of respiratory distress syndrome. This treatment package is part of the ‘Scandinavian model’ for treatment of very‐low‐birthweight infants which also comprises gentle ventilation at birth; minimal handling; ‘neonatal individualized development care and assessment program’; high priority of breast feeding; and use of kangaroo method and which facilitates observation and nursing of sick premature infants and optimizes the possibility for early mother–child contact.

The incidence of bronchopulmonary dysplasia seems to be less of a problem in centres preferring nasal CPAP as the primary treatment for respiratory distress syndrome.
The Question of Socialist Writing and Sylvia Townsend Warner in the Thirties
Authors: Ewins Kristin
Published: April 2008

This essay was runner‐up in the 2007

Literature Compass

Graduate Essay Prize, Twentieth Century & Contemporary Section.

The 1930s was a time of crisis, ideological extremism and impending war. Few writers remained untouched by the political turmoil following the Great Depression in the West and Hitler's rise to power in 1933. The impulse of authors to involve themselves in politics at this time is suggested by the high number of radical and conservative periodicals flourishing in the 1930s. There also emerged divisive debate on the role of writers in shaping contemporary politics, battled out in a steady stream of international conferences. This article introduces one such controversy: the hostile debate between proponents of socialist writing and modernism culminating in the notorious Writers’ Congress in Moscow in 1934. I then look in more detail at how one Communist writer, Sylvia Townsend Warner, negotiated such debate in her journalism and literary writing: a regular contributor to the left‐wing journal Left Review, Warner provides an illustrative example of a writer who bridged the gulf between ideas of writing as a purely political or aesthetic form of expression.
The evolutionary relationship between the duplicated copies of the zebrafish fabp11 gene and the tetrapod FABP4, FABP5, FABP8 and FABP9 genes
Authors: Karanth Santhosh , Denovan‐Wright Eileen M. , Thisse Christine , Thisse Bernard , Wright Jonathan M.
Published: April 2008

We describe the structure of a fatty acid‐binding protein 11 (fabp11b) gene and its tissue‐specific expression in zebrafish. The 3.4 kb zebrafish fabp11b is the paralog of the previously described zebrafish fabp11a, with a deduced amino acid sequence for Fabp11B exhibiting 65% identity with that of Fabp11A. Whole mount in situ hybridization of a riboprobe to embryos and larvae showed that zebrafish fabp11b transcripts were restricted solely to the retina and were first detected at 24 h postfertilization. In situ hybridization revealed fabp11b transcripts along the spinal cord in adult zebrafish. However, the highly sensitive RT‐PCR assay detected fabp11b transcripts in the brain, heart, ovary and eye in adult tissues. By contrast, fabp11a transcripts had been previously detected in the liver, brain, heart, testis, muscle, ovary and skin of adult zebrafish. Using the LN54 radiation hybrid panel, we assigned zebrafish fabp11b to linkage group 16. Phylogenetic analysis and conserved gene synteny with tetrapod genes indicated that the emergence of two copies of fabp11 in the zebrafish genome may have resulted from a fish‐specific whole genome duplication event. Furthermore, we propose that the FABP4–FABP5–FABP8–FABP9 (PERF15) gene cluster on a single chromosome in the tetrapod genome and the fabp11 genes in the zebrafish genome originated from a common ancestral gene, which, following their divergence, gave rise to the fabp11 genes of zebrafish, and the progenitor of the FABP4, FABP5, FABP8 and FABP9 genes in tetrapods after the separation of the fish and tetrapod lineages.
Endovascular repair of an aortoiliac aneurysm with bilateral bifurcated branched iliac stent‐grafts
Authors: Teoh Anthony Yuen‐Bun , Fung Terrence Man‐Kit , Lam Yuk‐Hoi , Ho Simon Sze‐Ming , Yu Simon Chun‐Ho , Lau James Yun‐Wong
Published: April 2008

Extension of abdominal aortic aneurysms to involve one or both common iliac arteries occurs in 20–30% of patients. In treating aneurysmal diseases involving the common iliac arteries, preservation of blood flow to the pelvic circulation is desirable. The development of branched stent‐grafts has made this possible with the endovascular approach. We herein describe our technique of endovascular repair of an aortoiliac aneurysm with bilateral bifurcated branched iliac stent‐grafts.
Abdominal actinomycosis: Case report and review of the Chinese experience in the past 10 years
Authors: Lee Hencher Han‐Chih , Chan Kin‐Chun , Tang Lap‐Chiu
Published: April 2008

Actinomycosis is a rare infection caused by different species of actinomycosis. We report a case of intra‐abdominal actinomycosis that presented with abdominal mass. The diagnosis was only made after surgical excision where preoperative computed tomography scan could not distinguish this inflammatory mass from the tumour. The patient was successfully treated with surgery and antibiotics. A literature search on cases reported in Hong Kong and China in the past 10 years was reviewed.
Growing Economic Interdependence of China and the Gulf Cooperation Council
Authors: Thorpe Michael , Mitra Sumit
Published: April 2008

The six nations of the Gulf Cooperation Council (GCC) have approximately 40 percent of total proven oil reserves as well as 23 percent of the world's gas reserves. Although rising oil revenues have led to greater outward investment flows, there is also a growing need for significant expansion of the domestic energy sector's capacity. Meanwhile, China's sustained economic boom has resulted in China emerging as the world's second largest consumer and importer of oil, with close to 40 percent of its import demand presently sourced from the GCC. This share will grow significantly in the future. Commercial relations between the GCC and China have to date been dominated by energy‐related bilateral investment flows and China's oil imports. Although this will continue to be a central feature, trade and investment links in non‐energy areas will further broaden and deepen the relationship. China's relationship with the USA in terms of energy is also emerging as a major issue. Rather than being competitors, a mutual dependence on stable and secure supplies from the GCC highlights the need for a cooperative relationship.
Evolutionary consequences of fishing and their implications for salmon
Authors: Hard Jeffrey J. , Gross Mart R. , Heino Mikko , Hilborn Ray , Kope Robert G. , Law Richard , Reynolds John D.
Published: April 2008

We review the evidence for fisheries‐induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries‐induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long‐term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long‐term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done.
Fitness of hatchery‐reared salmonids in the wild
Authors: Araki Hitoshi , Berejikian Barry A. , Ford Michael J. , Blouin Michael S.
Published: April 2008

Accumulating data indicate that hatchery fish have lower fitness in natural environments than wild fish. This fitness decline can occur very quickly, sometimes following only one or two generations of captive rearing. In this review, we summarize existing data on the fitness of hatchery fish in the wild, and we investigate the conditions under which rapid fitness declines can occur. The summary of studies to date suggests: nonlocal hatchery stocks consistently reproduce very poorly in the wild; hatchery stocks that use wild, local fish for captive propagation generally perform better than nonlocal stocks, but often worse than wild fish. However, the data above are from a limited number of studies and species, and more studies are needed before one can generalize further. We used a simple quantitative genetic model to evaluate whether domestication selection is a sufficient explanation for some observed rapid fitness declines. We show that if selection acts on a single trait, such rapid effects can be explained only when selection is very strong, both in captivity and in the wild, and when the heritability of the trait under selection is high. If selection acts on multiple traits throughout the life cycle, rapid fitness declines are plausible.
Potential responses to climate change in organisms with complex life histories: evolution and plasticity in Pacific salmon
Authors: Crozier L. G. , Hendry A. P. , Lawson P. W. , Quinn T. P. , Mantua N. J. , Battin J. , Shaw R. G. , Huey R. B.
Published: April 2008

Salmon life histories are finely tuned to local environmental conditions, which are intimately linked to climate. We summarize the likely impacts of climate change on the physical environment of salmon in the Pacific Northwest and discuss the potential evolutionary consequences of these changes, with particular reference to Columbia River Basin spring/summer Chinook (Oncorhynchus tshawytscha) and sockeye (Oncorhynchus nerka) salmon. We discuss the possible evolutionary responses in migration and spawning date egg and juvenile growth and development rates, thermal tolerance, and disease resistance. We know little about ocean migration pathways, so cannot confidently suggest the potential changes in this life stage. Climate change might produce conflicting selection pressures in different life stages, which will interact with plastic (i.e. nongenetic) changes in various ways. To clarify these interactions, we present a conceptual model of how changing environmental conditions shift phenotypic optima and, through plastic responses, phenotype distributions, affecting the force of selection. Our predictions are tentative because we lack data on the strength of selection, heritability, and ecological and genetic linkages among many of the traits discussed here. Despite the challenges involved in experimental manipulation of species with complex life histories, such research is essential for full appreciation of the biological effects of climate change.
Deformation in Multilayer Stacked Assemblies
Authors: Pan Tsung-Yu , Pao Yi-Hsin
Published: April 2008

A linear-elastic analytical model has been developed to describe the deformed geometry of a multi-layered stack assembly subject to thermal loading. The model is based on Timoshenko’s bimetal thermostat analysis [1] and consists of a series of first-order polynomial equations. The radius of curvature, bending moment, force, horizontal and vertical displacements can be determined numerically. These quantities match well with finite element analysis. Calculations for silicon power transistor stacks are presented in order to demonstrate the model capability. The results from this analyitcal model have been found to correlate well with experimental measurements when an appropriate secant modulus is used to represent the nonlinear stress-strain behavior of solder.
Thermal Stress CAD Analysis of a Multi-Layer Composite of an Operating Transistor Package
Authors: Ghorieshi Agha J. , Nejib Umid R.
Published: April 2008

Thermal stress management is a major factor in the design of an electronic package. Thermal mismatch among the assembled components induces thermal stresses within the device. Finite element technique is utilized for three dimensional thermal stress analysis of a transistor with a free convection cooling system. Heat transfer analysis is used to determine the temperature distribution throughout the package for a given operating temperature. The data are then used to determine package stresses. The results show the shear stress concentration is higher at the corner of the chip. These values were found to be lower compared to those using temperature cycle analysis. An alternative method of lowering shear stresses in the chip is suggested.
Thermally Induced Failure of Microelectronic Structures
Authors: Cardenas-Garcia J. F. , Chyu M. C.
Published: April 2008

The purpose of this paper is to perform a theoretical evaluation to assess mechanical failure of an idealized two-dimensional, narrow, thin microelectronic structure, modelled as a plate, composed of a homogeneous, isotropic, linear-elastic material. The proposed steady-state model examines the effects of imposing a constant-uniform-uniaxial mechanical load, whose magnitude is a fraction of the yield strength of the material at room temperature, on a plate with an existing thermal stress profile generated by a gaussian temperature gradient across the plate width. The temperature dependence of the mechanical properties of the material requires that a new approach to failure evaluation be implemented. The model shows that failure can occur anywhere in the cross-section of the plate and at loads well below the yield strength of the material at room temperature, depending on the particular conditions which the plate experiences. These preliminary results may find applicability in the evaluation of microelectronic structures, e.g., a silicon chip mounted on a substrate and subjected to convective cooling due to fluid (gas or liquid) flow in a preferred direction. Resulting thermal gradients and stresses, in conjunction with mechanical loading generated from thermal expansion mismatch between the chip and the substrate, may cause component failure.
High and Low Temperature Strain-Life Behavior of a Pb Rich Solder
Authors: Solomon H. D.
Published: April 2008

This paper describes the fatigue behavior of a Pb rich solder, 92.5Pb, 2.5Ag, 5.0Sn (Indalloy 151), tested at −50°C and +150°C. The results are compared to previously reported studies of 60Sn/40Pb solder and to tests of Indalloy 151 performed at 35° C. The Coffin-Manson exponent is larger at all temperatures for the Indalloy 151 compared to the 60Sn/40Pb, but this effect is especially pronounced at +150° C where the exponent is 0.85 for the Indalloy 151 and only 0.35 for the 60Sn/40Pb. This gives rise to a crossover in the behavior of the two solders with the Indalloy 151 exhibiting a longer fatigue life at high strains and the 60Sn/40Pb exhibiting superior behavior at low strains.
Determination of Stress Intensity Factors for Interfacial Cracks in Bimaterial Systems
Authors: Pao Yi-Hsin , Pan Tsung-Yu
Published: April 2008

A relatively simple numerical method was developed to determine the stress intensity factors of interfacial cracks in bimaterial systems. The method is based on the evaluation of crack tip stress components using a p-version finite element method. Numerical experiments on a number of specimen geometries covering a wide range of material combination were performed. The geometries tested include a center-cracked panel (CCP), a single-lap shear joint (SLS) having two anti-symmetric cracks at the edges, a four-point bend specimen, and a bonded double-cantileverbeam (DCB) specimen. The numerical results agreed well with the analytical solutions and the experimental data of certain geometries. The range of integration distance over which accurate stress intensity factors can be determined was found to be within 10−5 and 10−3 of crack length and seems to be geometry independent.
Micromechanical Method to Predict Fatigue Life of Solder
Authors: Zubelewicz A. , Guo Q. , Cutiongco E. C. , Fine M. E. , Keer L. M.
Published: April 2008

Fatigue lifetimes of low-tin high-lead and tin-lead eutectic solders under total strain controlled tension-tension tests were studied in this paper. Based on the stress and strain micro-macro correlations, a modified Coffin-Manson law is obtained. The modified lifetime prediction formulas which had been used to predict the fatigue lifetime for low-tin high-lead solder, exhibiting cyclic hardening and then saturation, was found to apply to the eutectic solder, where substantial cyclic softening has been observed. This micromechanically based approach allows one to model the known physical phenomena in solders by modifying the appropriate parameters in the predictive micromechanically based constitutive equations.
A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks
Authors: Lehmann G. L. , Kosteva S. J.
Published: April 2008

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.
A Zonal Decomposition Methodology for Detailed Temperature Field Evaluation
Authors: Tan Cha-Hsiang , Pecht Michael
Published: April 2008

A zonal decomposition technique is developed for temperature field and flux determination at both aligned and nonaligned grid interface boundaries. The method facilitates heat transfer problems commonly encountered in electronics including PWBs with multiple irregular boundaries in which numerical generation of boundary-fitted coordinates is required. To demonstrate the applicability and performance of the method, a 2-D heat conduction problem in Cartesian coordinates, a 2-D heat conduction problem in curvilinear coordinates, and a 3-D heat conduction problem in curvilinear coordinates are solved. Comparisons between numerical and analytical results are shown to be in excellent agreement.
Thermal Strain Measurements in Electronic Packages Through Fractional Fringe Moire´ Interferometry
Authors: Bastawros A. F. , Voloshin A. S.
Published: April 2008

Fractional Fringe Moire´ Interferometry (FFMI)—a new experimental methodology to measure accurately deformations and consequently strains—has been successfully implemented to determine thermally induced strains in a specimen made from an AT&T 1MB DRAM device. The specimen was heated uniformly from room temperature to 90° C. Resulting moire´ fringe patterns were recorded, analyzed using digital-image-processing and in plane displacements in the device were determined. Strain components were computed by simple differentiation of the displacement fields. The technique proved to be successful in detecting full displacement fields with submicron resolution. Contour maps showing actual thermo/mechanical strain components in the specimen were constructed. Those maps can provide an excellent tool realistic for strain analysis of microelectronic devices regardless of the structural and material complexity.
Mechanical Behavior of Flip-Chip Encapsulants
Authors: Suhir E. , Segelken J. M.
Published: April 2008

Requirements for the mechanical properties of the encapsulation material in a flip-chip design to prevent the solder and the encapsulation material itself from failure are presented on the basis of the developed analytical stress models, enabling one to predict the stresses caused by the expansion (contraction) mismatch of these materials. We evaluate and discuss the mechanical behavior of encapsulants for two encapsulation technologies: 1) encapsulant fills in the entire underchip space (silicone gels, epoxies); 2) encapsulant conformably coats the underchip surfaces (polyxylylene, polyimide). The calculations are carried out for an Advanced VLSI Package Design. The calculated data have indicated that low modulus silicone gel results in the lowest stresses. Polyxylylene should be considered as the second preference. Polyimide is also acceptable. Epoxies, however, could result in significant stresses in solder joints and therefore are less attractive. The final selection of the most feasible encapsulant should be done, of course, with consideration of all the electrical, chemical, and technological requirements.
Forced Convection Air Cooling of Simulated Low Profile Electronic Components: Part 1—Base Case
Authors: Lehmann G. L. , Pembroke J.
Published: April 2008

Forced convection cooling of a simulated array of card-mounted electronic components has been investigated. An important feature of the simulated components is their relatively low profile (height/length = 0.058). Laboratory measurements of heat transfer rates resulting from convective air flow through a low aspect ratio channel are reported. The effect of variations in array position, channel spacing and flow rate is discussed. In the flow range considered laminar, transitional and turbulent heat transfer behavior have been observed. The behavior due to variations in flow rate and channel spacing is well correlated using a Reynolds number based on component length.
Design Factors With Realistic I/O Distributions
Authors: Koons John P.
Published: April 2008

This paper explores some design factors, including wireability, of packages in which the number of I/O per module to be interconnected varies widely. This is of interest because it is common for memory card designs and for work station and personal computer printed circuit designs. Memory cards often have a few relatively high pin count control logic modules supporting many low pin count array modules. Work station and personal computer cards often use low density “glue” logic modules with a few microprocessor modules and their high function supports. Printed circuit cost and performance factors are examined by example. Differences between area array and perimeter escape components and leverage possibilities of multi-chip modules are examined. A background tutorial on wireability analysis is given. The algorithm used was developed by Wadie Mikhail several years ago. Analyses are based on the length of wire paths available in a given design, the length of wire needed and the utilizations of the available paths. Utilization guidelines are suggested. Alternative wireability algorithms are identified and briefly discussed. Although the examples are given for cases of modules on cards, the methodologies and general conclusions are valid at other packaging levels; for example, for chips on multi-chip modules.
A Plate Contactor in a Mechanical Input/Output Connector Interface: How Small Can It Be?
Authors: Suhir E.
Published: April 2008

The purpose of this study is to find out if a contactor in a mechanical input/output connector interface, using elongated plates subjected to bending, can be made sufficiently small to be utilized in an advanced VLSI package to interconnect it to the “outside world”. A design with metallic plate contactors having both ends clamped and a design with cantilever contactors are examined and analyzed. It is shown that the size of the structure is restricted by the strength of the plate material and that cantilever plates result in almost three times smaller effective length of the contactor than both-ends-clamped plates. The obtained results can be used as a guidance in physical design of mechanical input/output connectors of the type in question.
Thermal Cycling Induced Plastic Deformation in Solder Joints—Part I: Accumulated Deformation in Surface Mount Joints
Authors: Pan Tsung-Yu
Published: April 2008

When an electronic package is subjected to thermal cycling, the solder joint interconnects are subjected to a complex stress system. If the stress is sufficiently large, the solder joint will show evidence of plastic flow along with microstructure coarsening and possible fatigue crack initiation and propagation. Plastic flow has not been studied as thoroughly as the later two phenomena although it is often observed at surface mount or through-hole solder joints. The thermal expansion mismatch between different materials in the package is responsible for the plastic deformation which accumulates with thermal cycling. In this study, the accumulated plastic deformation process is modelled with finite element (FE) methods and compared with experimental results. Lead-frame solder joints have been analyzed with a nonlinear FE program using temperature and time-dependent properties. Steady-state creep is considered using data for eutectic lead/tin solder which is described by a hyperbolic sine creep law: ε = A(sinh Bσ)ndmexp(−Q/RT). The analysis correctly simulates the large plastic flow found experimentally in a lead-frame solder joint. The resulting stress and strain distributions indicate possible failure modes which are not anticipated on the basis of uniform shear assumptions or predictable from an FE analysis of the initial geometry.
Superplastic Creep of Eutectic Tin-Lead Solder Joints
Authors: Mei Z. , Morris J. W. , Shine M. C.
Published: April 2008

The creep behavior of air-cooled and liquid nitrogen-quenched soldered joints of 60/40 Sn-Pb at 65°C has been studied. The stress exponent, n, in the power law, γ˙ (steady state strain rate) ∝σn (applied stress), changes from a value of about 6 to values of 2 to 3, as γ˙ decreases below 10−4 in/in per second. This result, combined with the authors’ previous stepped load creep test results, indicates a transition of the creep deformation mechanism from conventional dislocation climb to superplastic grain boundary sliding. The superplastic creep of the soldered joints is ascribed to their non-lamellar microstructure due to their fast cooling rate. During creep deformation, recrystallization of the soldered joints occurs, causing softening.
Fatigue Analysis of a Ceramic Pin Grid Array Soldered to an Orthotropic Epoxy Substrate
Authors: Lau J. , Subrahmanyan R. , Rice D. , Erasmus S. , Li C.
Published: April 2008

Thermal stresses and strains in the solder joints and plated-through-hole (PTH) copper pads/barrels of a pin-grid array (PGA) assembly under thermal cycling conditions have been determined in the present study. There are two major systems of thermal stresses/strains acting at the solder joint and copper. One is the transverse shear and vertical normal stress/strain due to the local thermal expansion mismatch between the pin, solder, copper, and FR-4. The other is the horizontal normal stress/strain due to the global thermal expansion mismatch between the ceramic PGA and the FR-4 printed circuit board (PCB). The effects of the local thermal expansion mismatch on the reliability of solder joint and PTH copper have been determined using a 3-D orthotropic-elastoplastic finite element method. The effects of the global thermal expansion mismatch on the reliability of solder joint and PTH copper have been determined by fatigue experiments. Fatigue life of the solder joint and PTH copper was then estimated based on the calculated strains and the fatigue data on solders and coppers.
Stress Relief in Solder Joints Due to the Application of a Flex
Circuit
Authors: Suhir E.
Published: April 2008

A stress analysis model is developed to assess the stresses in solder joints caused by thermal contraction mismatch between a low expansion flex-circuit (FC) and a high expansion rigid substrate. It is shown that application of low expansion FCs can result in significant stress relief for solder joints. This is due to the fact that the force acting on a joint cannot exceed the buckling force for the adjacent portion of the FC. It is shown that the strains in solder joints interconnecting FCs to rigid substrates can be made very small, thereby resulting in a substantially longer fatigue life of the interconnection. In the executed example these strains are about two orders of magnitude smaller, than in the case of a rigid board. The obtained results can be utilized as guidance in physical design of assemblies with FCs.
Heat Transfer and Thermal Stress Analysis of an Optoelectronic
Package
Authors: Stack J. G. , Acarlar M. S.
Published: April 2008

The reliability and life of an Optical Data Link transmitter are inversely related to the temperature of the LED. It is therefore critical to have efficient packaging from the point of view of thermal management. For the ODL® 200H devices, it is also necessary to ensure that all package seals remain hermetic throughout the stringent military temperature range requirements of −65 to +150°C. For these devices, finite element analysis was used to study both the thermal paths due to LED power dissipation and the thermally induced stresses in the hermetic joints due to ambient temperature changes
Influence of Discrete Heat Source Location on Natural Convection Heat
Transfer in a Vertical Square Enclosure
Authors: Refai Ahmed G. , Yovanovich M. M.
Published: April 2008

A numerical study is carried out to investigate the influence of discrete heat sources on natural convection heat transfer in a square enclosure filled with air. The enclosure has two vertical boundaries of height H; one of them is cooled at Tc and the other has discrete heat sources [isoflux (q = c) or isothermal (Th = c)]. The enclosure has two horizontal adiabatic boundaries of length L. Results are reported for 0 ≤ Ra ≤ 106, Pr = 0.72, A = 1, aspect ratio ε, the relative size of the heat source to the total height, lies in the range 0.25 ≤ ε ≤ 1 and the discrete heat sources are located at the top or the bottom of the enclosure. Verification of numerical results is obtained at Ra = 0 (conduction limit) with analytical conduction solutions. In addition, a comparison with experimental and numerical data is made which also shows good agreement. The relationships between both Nu, ΔNu (change of thermal conductance) and Ra based on scale length (the size of the heat source S divided by the aspect ratio A) are also investigated here. A relationship Nu and Ra, based on scale length obtained from analytical solutions is correlated as Nu = Nu(Ra, ε). In addition, extrapolation correlations of Nu over the very high range of Rayleigh numbers (Ra ≥ 108) are developed.
Heat Transfer Study of Staggered Thin Rectangular Blocks in a Channel
Flow
Authors: Chen Ching Jen , Bravo Ramiro H.
Published: April 2008

In this study, fluid flow and heat transfer in two-dimensional staggered thin rectangular blocks in a channel flow heat exchanger is analyzed by the Finite Analytic Numerical Method. The heat exchanger consists of four staggered thin rectangular blocks at temperature T1 placed inside a channel which is formed by two plates maintained at constant temperature T0. The fluid is considered to be incompressible and the flow laminar. Flow and heat transfer from the inlet of the heat exchanger to the outlet are simulated by solving Navier-Stokes and energy equations. Results were obtained for different block spacing and different size of the blocks. Computations were made for Reynolds numbers 100, 500, and 1,000, and Prandtl numbers 0.7 and 4.0. The results are presented in the form of velocity vector fields, isotherms, and local and global Nusselt numbers. The characteristics of the heat transfer and pressure drop in different block size and block separation are analyzed. The optimal length of separation between thin blocks and the optimal block length for maximum heat transfer are determined.
Mixed Convective Heat Transfer From a Simulated Microchip to Liquid
Flows in a Horizontal Rectangular Channel
Authors: Chin Y. , Ma C. F. , Gu X. Q. , Xu L.
Published: April 2008

Mixed convection from a small heater (5mm × 5mm) to liquid flows in a horizontal rectangular channel is investigated experimentally. The results of three cases in which the buoyancy is normal to the liquid flow directions — hot surface facing upward, facing downward and vertically attached to one wall of the channel — are presented. Correlations are also provided to predict the mixed convective effects in the range 100 < ReL < 4000. The results demonstrated that both the Reynolds number ReL and the modified Rayleigh number RaL* pronouncedly dominate the heat transfer process. In all of the above cases, heat transfer was enhanced over that of forced convection.