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The B1C8 protein is in the dense assemblies of the nuclear matrix and relocates to the spindle and pericentriolar filaments at mitosis.

Wan, K M; Nickerson, J A; Krockmalnic, G; Penman, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 18/01/1994 EN
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26.26%
The B1C8 monoclonal antibody detects a 180-kDa nuclear matrix-specific protein. The protein is a component of the dense, metabolically active bodies or assemblies revealed by resinless section electron microscopy of the nuclear matrix. These assemblies are scattered through the nuclear interior, enmeshed in a complex network of 11-nm filaments. Resinless section electron microscopy of immunogold-stained nuclear matrix preparations shows B1C8 located in many but apparently not all the assemblies. In this regard, the B1C8 antigen resembles previously studied nuclear matrix proteins such as the H1B2 protein. The speckled pattern of nuclear immunofluorescence by B1C8 reflects this labeling of the dense assemblies in the nuclear matrix. Somewhat unusual is the faint staining of cytoplasmic microtubules by B1C8, which appears to be due to a weakly cross-reacting protein. During cell division, the B1C8 antigen redistributed drastically, showing the dispersion of nuclear matrix assemblies at mitosis. Speckles of B1C8 fluorescence first coalesced at prophase within the nuclear interior and then scattered into numerous cytoplasmic speckles by prometaphase. At metaphase, the B1C8 speckled cytoplasmic staining had become even more widely distributed and finely grained. Also...

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

Sreenivasachary, Nampally; Lehn, Jean-Marie
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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26.22%
The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven self-organization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel self-assembly involving three dynamic processes...

Structure of beta-crystallite assemblies formed by Alzheimer beta-amyloid protein analogues: analysis by x-ray diffraction.

Inouye, H.; Fraser, P. E.; Kirschner, D. A.
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em /02/1993 EN
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26.23%
To elucidate the relation between amyloid fibril formation in Alzheimer disease and the primary structure of the beta/A4 protein, which is the major component of the amyloid, we have been investigating the ability of peptides sharing sequences with beta/A4 to form fibrils in vitro. In previous studies we focused on the macroscopic morphology of the assemblies formed by synthetic peptides corresponding in sequence to different regions of this protein. In the present study we analyze the x-ray diffraction patterns obtained from these assemblies. All specimens showed wide angle reflections that could be indexed by an orthogonal lattice of beta-crystallites having unit cell dimensions a = 9.4 A, b = 7 A, and c = 10 A, where a refers to hydrogen bonding direction, b to polypeptide chain direction, and c to intersheet direction. Given the amino acid sequence of beta/A4 as NH2-DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIAT-COOH, we found that, based on their orientation and assembly, the analogues could be classified into three groups: Group A, residues 19-28, 13-28, 12-28, 11-28, 9-28, 1-28, 1-38, 1-40, 6-25, 11-25 and 34-42; Group B, residues 18-28, 17-28, and 15-28; and Group C, residues 22-35 and 26-33. For Groups A and C, the sharpest reflections were (h00)...

Integration of small angle X-ray scattering data into structural modeling of proteins and their assemblies

Förster, Friedrich; Webb, Benjamin; Krukenberg, Kristin A.; Tsuruta, Hiro; Agard, David A.; Sali, Andrej
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.26%
A major challenge in structural biology is to determine the configuration of domains and proteins in multi-domain proteins and assemblies, respectively. To maximize the accuracy and precision of these models, all available data should be considered. Small angle x-ray scattering (SAXS) efficiently provides low-resolution experimental data about the shapes of proteins and their assemblies. Thus, we integrated SAXS profiles into our software for modeling proteins and their assemblies by satisfaction of spatial restraints. Specifically, we model the quaternary structures of multidomain proteins with structurally defined rigid domains as well as quaternary structures of binary complexes of structurally defined rigid proteins. In addition to SAXS profiles and the component structures, we employ stereochemical restraints and an atomic distance-dependent statistical potential. The scoring function is optimized by a biased Monte Carlo protocol, including quasi-Newton and simulated annealing schemes. The final prediction corresponds to the best scoring solution in the largest cluster of many independently calculated solutions. To quantify how well the quaternary structures are determined based on their SAXS profiles, we used a benchmark of 12 simulated examples as well as an experimental SAXS profile of the homo-tetramer D-xylose isomerase. Optimization of the SAXS-dependent scoring function generally results in accurate models...

Principal component analysis of ensemble recordings reveals cell assemblies at high temporal resolution

Peyrache, Adrien; Benchenane, Karim; Khamassi, Mehdi; Wiener, Sidney I.; Battaglia, Francesco P.
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.23%
Simultaneous recordings of many single neurons reveals unique insights into network processing spanning the timescale from single spikes to global oscillations. Neurons dynamically self-organize in subgroups of coactivated elements referred to as cell assemblies. Furthermore, these cell assemblies are reactivated, or replayed, preferentially during subsequent rest or sleep episodes, a proposed mechanism for memory trace consolidation. Here we employ Principal Component Analysis to isolate such patterns of neural activity. In addition, a measure is developed to quantify the similarity of instantaneous activity with a template pattern, and we derive theoretical distributions for the null hypothesis of no correlation between spike trains, allowing one to evaluate the statistical significance of instantaneous coactivations. Hence, when applied in an epoch different from the one where the patterns were identified, (e.g. subsequent sleep) this measure allows to identify times and intensities of reactivation. The distribution of this measure provides information on the dynamics of reactivation events: in sleep these occur as transients rather than as a continuous process.

Dynamic Multi-Component Covalent Assembly for the Reversible Binding of Secondary Alcohols and Chirality Sensing

You, Lei; Berman, Jeffrey S.; Anslyn, Eric V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 13/11/2011 EN
Relevância na Pesquisa
35.99%
Reversible covalent bonding is often employed for the creation of novel supramolecular structures, multi-component assemblies, and sensing ensembles. In spite of remarkable success of dynamic covalent systems, the reversible binding of a mono-alcohol with high strength is challenging. Here we show that a strategy of carbonyl activation and hemiaminal ether stabilization can be embodied in a four-component reversible assembly that creates a tetradentate ligand and incorporates secondary alcohols with exceptionally high affinity. Evidence is presented that the intermediate leading to binding and exchange of alcohols is an iminium ion. Further, to demonstrate the use of this assembly process we explored chirality sensing and enantiomeric excess determinations. An induced twist in the ligand by a chiral mono-ol results in large Cotton effects in the circular dichroism spectra indicative of the alcohol’s handedness. The strategy revealed in this study should prove broadly applicable for the incorporation of alcohols into supramolecular architecture construction.

Dynamic Multi-Component Hemiaminal Assembly

You, Lei; Long, S. Reid; Lynch, Vincent M.; Anslyn, Eric V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.13%
A simple approach to generating in situ metal templated tris-(2-picolyl)amine-like multi-component assemblies with potential applications in molecular recognition and sensing is reported. The assembly is based on the reversible covalent association between di-(2-picolyl)amine and aldehydes. Zinc ion is the best for inducing assembly among the metal salts investigated, while 2-picolinaldehyde is the best among the heterocyclic aldehydes studied. Although an equilibrium constant of 6.6 * 103 M-1 was measured for the assembly formed by 2-picolinaldehdye, di-(2-picolyl)amine, and zinc triflate, the equilibrium constants for other systems are in the 102 M-1 range. X-ray structural analysis revealed that zinc adopts a trigonal bipyramidal geometry within the assembled ligand. The diversity and equilibrium of the assemblies are readily altered by simply changing concentrations, varying components, or adding counter anions.

Probing Structure and Dynamics of Protein Assemblies by Magic Angle Spinning NMR Spectroscopy

Yan, Si; Suiter, Christopher L.; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.23%
In living organisms, biological molecules often organize into multi-component complexes. Such assemblies consist of various proteins and carry out essential functions, ranging from cell division, transport, and energy transduction to catalysis, signaling, and viral infectivity. To understand the biological functions of these assemblies, in both healthy and disease states, researchers need to study their three-dimensional architecture and molecular dynamics. To date, the large size, the lack of inherent long-range order, and insolubility have made atomic-resolution studies of many protein assemblies challenging or impractical using traditional structural biology methods such as X-ray diffraction and solution NMR spectroscopy. In the past ten years, we have focused our work on the development and application of magic angle spinning solid-state NMR (MAS NMR) methods to characterize large protein assemblies at atomic-level resolution.

Architecture and roles of periplasmic adaptor proteins in tripartite efflux assemblies

Symmons, Martyn F.; Marshall, Robert L.; Bavro, Vassiliy N.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 28/05/2015 EN
Relevância na Pesquisa
26.19%
Recent years have seen major advances in the structural understanding of the different components of tripartite efflux assemblies, which encompass the multidrug efflux (MDR) pumps and type I secretion systems. The majority of these investigations have focused on the role played by the inner membrane transporters and the outer membrane factor (OMF), leaving the third component of the system – the Periplasmic Adaptor Proteins (PAPs) – relatively understudied. Here we review the current state of knowledge of these versatile proteins which, far from being passive linkers between the OMF and the transporter, emerge as active architects of tripartite assemblies, and play diverse roles in the transport process. Recognition between the PAPs and OMFs is essential for pump assembly and function, and targeting this interaction may provide a novel avenue for combating multidrug resistance. With the recent advances elucidating the drug efflux and energetics of the tripartite assemblies, the understanding of the interaction between the OMFs and PAPs is the last piece remaining in the complete structure of the tripartite pump assembly puzzle.

Neuronal Assembly Detection and Cell Membership Specification by Principal Component Analysis

Lopes-dos-Santos, Vítor; Conde-Ocazionez, Sergio; Nicolelis, Miguel A. L.; Ribeiro, Sidarta T.; Tort, Adriano B. L.
Fonte: Universidade Federal do Rio Grande do Norte Publicador: Universidade Federal do Rio Grande do Norte
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.43%
LOPES-DOS-SANTOS, V. , CONDE-OCAZIONEZ, S. ; NICOLELIS, M. A. L. , RIBEIRO, S. T. , TORT, A. B. L. . Neuronal assembly detection and cell membership specification by principal component analysis. Plos One, v. 6, p. e20996, 2011.; In 1949, Donald Hebb postulated that assemblies of synchronously activated neurons are the elementary units of information processing in the brain. Despite being one of the most influential theories in neuroscience, Hebb’s cell assembly hypothesis only started to become testable in the past two decades due to technological advances. However, while the technology for the simultaneous recording of large neuronal populations undergoes fast development, there is still a paucity of analytical methods that can properly detect and track the activity of cell assemblies. Here we describe a principal component-based method that is able to (1) identify all cell assemblies present in the neuronal population investigated, (2) determine the number of neurons involved in ensemble activity, (3) specify the precise identity of the neurons pertaining to each cell assembly, and (4) unravel the time course of the individual activity of multiple assemblies. Application of the method to multielectrode recordings of awake and behaving rats revealed that assemblies detected in the cerebral cortex and hippocampus typically contain overlapping neurons. The results indicate that the PCA method presented here is able to properly detect...

Detecting cell assemblies in large neuronal populations

Lopes-dos-Santos, Vitor; Ribeiro, Sidarta; Tort, Adriano
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.36%
Recent progress in the technology for single unit recordings has given the neuroscientific community theopportunity to record the spiking activity of large neuronal populations. At the same pace, statistical andmathematical tools were developed to deal with high-dimensional datasets typical of such recordings.A major line of research investigates the functional role of subsets of neurons with significant co-firingbehavior: the Hebbian cell assemblies. Here we review three linear methods for the detection of cellassemblies in large neuronal populations that rely on principal and independent component analysis.Based on their performance in spike train simulations, we propose a modified framework that incorpo-rates multiple features of these previous methods. We apply the new framework to actual single unitrecordings and show the existence of cell assemblies in the rat hippocampus, which typically oscillate attheta frequencies and couple to different phases of the underlying field rhythm

Environmental and Cost impact Analysis of Materials and Assemblies in Building Construction

Nirmal, Deepika
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
46.26%
One of the new trends in the building construction industry is designing for environmental-friendly buildings, a.k.a. Green Buildings. Planners and designers are therefore trying to accommodate these new environmental practices into existing design criteria. Selection of building materials is one of the key decisions need to be made by building designers. However, due to the strong influence of costs on the building industry, making material-selection decisions solely based on their environmental impacts could be both inadequate and impractical. These factors therefore complicate the building design process, especially pertaining to material selection. Accordingly, the present study is aimed at providing much needed support to the decision-making process of residential building design. To this end, the study evaluates and analyzes the environmental and cost impacts of several building assemblies and material alternatives for the building exterior walls. The Technique of Order Preference Similar to Ideal Solution (TOPSIS) is used to evaluate and rank different material alternatives used in walls based on their environmental impacts. In addition, the environmental data used in this study were extracted from commonly used databases that considered the lifecycle impacts of different residential building materials and assemblies. The environmental and cost impacts of several exterior wall assemblies are then aggregated for different building material alternatives to allow for an objective comparison of these assemblies and facilitate proper building design decision- making. The study results show that wood and exterior insulation finishing system (EIFS) provided the best environmental performance of wall structural and wall finishing materials...

Design oriented simulation of contact-friction instabilities in application to realistic brake assemblies

VERMOT DES ROCHES, Guillaume; BALMES, Etienne; LEMAIRE, Rémi; PASQUET, Thierry
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN_US
Relevância na Pesquisa
35.99%
This paper presents advances in non-linear simulations for systems with contact-friction, with an application to brake squeal. A method is proposed to orient component structural modifications from brake assembly simulations in the frequency and time domains. A reduction method implementing explicitly component-wise degrees of freedom at the system level allows quick parametric analyses giving modification clues. The effect of the modification is then validated in the time domain where non-linearities can be fully considered. A reduction method adapted for models showing local non-linearities is purposely presented along with an optimization of a modified non linear Newmark scheme to make such computation possible for industrial models. The paper then illustrates the importance of structural effects in brake squeal, and suggests solutions.

Neuronal Assembly Detection and Cell Membership Specification by Principal Component Analysis

Lopes-dos-Santos, Vítor; Conde-Ocazionez, Sergio; Nicolelis, Miguel A. L.; Ribeiro, Sidarta T.; Tort, Adriano B. L.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 15/06/2011 EN
Relevância na Pesquisa
26.37%
In 1949, Donald Hebb postulated that assemblies of synchronously activated neurons are the elementary units of information processing in the brain. Despite being one of the most influential theories in neuroscience, Hebb's cell assembly hypothesis only started to become testable in the past two decades due to technological advances. However, while the technology for the simultaneous recording of large neuronal populations undergoes fast development, there is still a paucity of analytical methods that can properly detect and track the activity of cell assemblies. Here we describe a principal component-based method that is able to (1) identify all cell assemblies present in the neuronal population investigated, (2) determine the number of neurons involved in ensemble activity, (3) specify the precise identity of the neurons pertaining to each cell assembly, and (4) unravel the time course of the individual activity of multiple assemblies. Application of the method to multielectrode recordings of awake and behaving rats revealed that assemblies detected in the cerebral cortex and hippocampus typically contain overlapping neurons. The results indicate that the PCA method presented here is able to properly detect, track and specify neuronal assemblies...

Heterogeneity of a Fluorescent Tegument Component in Single Pseudorabies Virus Virions and Enveloped Axonal Assemblies

del Rio, T.; Ch'ng, T. H.; Flood, E. A.; Gross, S. P.; Enquist, L. W.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2005 EN
Relevância na Pesquisa
26.13%
The molecular mechanisms responsible for long-distance, directional spread of alphaherpesvirus infections via axons of infected neurons are poorly understood. We describe the use of red and green fluorescent protein (GFP) fusions to capsid and tegument components, respectively, to visualize purified, single extracellular virions and axonal assemblies after pseudorabies virus (PRV) infection of cultured neurons. We observed heterogeneity in GFP fluorescence when GFP was fused to the tegument component VP22 in both single extracellular virions and discrete puncta in infected axons. This heterogeneity was observed in the presence or absence of a capsid structure detected by a fusion of monomeric red fluorescent protein to VP26. The similarity of the heterogeneous distribution of these fluorescent protein fusions in both purified virions and in axons suggested that tegument-capsid assembly and axonal targeting of viral components are linked. One possibility was that the assembly of extracellular and axonal particles containing the dually fluorescent fusion proteins occurred by the same process in the cell body. We tested this hypothesis by treating infected cultured neurons with brefeldin A, a potent inhibitor of herpesvirus maturation and secretion. Brefeldin A treatment disrupted the neuronal secretory pathway...

Landscape of kinetically trapped binary assemblies

Mannige, Ranjan V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/11/2015
Relevância na Pesquisa
36.33%
For two-component assemblies, an inherent structure diagram (ISD) is the relationship between set inter-subunit energies and the types of kinetic traps (inherent structures) one may obtain from those energies. It has recently been shown that two-component ISDs are apportioned into regions or plateaux within which inherent structures display uniform features (e.g., stoichometries and morphologies). Interestingly, structures from one of the plateaux were also found to be robust outcomes of one type of non-equilibrium growth, which indicates the usefulness of the two-component ISD in predicting outcomes of some types of far-from-equilibrium growth. However, little is known as to how the ISD is apportioned into distinct plateaux. Also, while each plateau displays classes of structures that are morphologically distinct, little is known about the source of these distinct morphologies. This article outlines an analytic treatment of the two-component ISD, and shows that the manner in which any ISD is apportioned arises from a single unitless order parameter. Additionally, the analytical framework allows for the characterization of local properties of the trapped structures within each ISD plateau. This work may prove to be useful in the design of novel classes of robust nonequilibrium assemblies.; Comment: Upcoming in the Journal of Chemical Physics

Controlling Plasmon Coupling in Biomolecule-Linked Nanoparticle Assemblies

Sebba, David S
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 13397979 bytes; application/pdf
Publicado em 30/07/2008 EN_US
Relevância na Pesquisa
26.36%

Molecular control of plasmon coupling is investigated in biomolecule-linked nanoparticle assemblies in two-particle, small cluster, and extended network formats. The relationship between structure and optical properties is explored through comparison of measured spectra with simulated spectra calculated using structural models based upon measured structural parameters. A variety of techniques are used to characterize nanoparticle assemblies, including ensemble extinction and elastic scattering spectroscopy, single-assembly scattering spectroscopy, transmission electron microscopy, and dynamic light scattering. Initially, molecular control of plasmon coupling is investigated in ~100 nm assemblies composed of 13 nm gold "satellite" particles tethered by duplex DNA to a 50 nm gold "core" particle. Comparison of core-satellite assemblies formed with duplex DNA tethers of varying length demonstrates that, while core-satellite separation is controlled by the number of base pairs in the DNA tether, structural properties such as core:satellite ratio and yield are independent of DNA tether length. Thus, plasmon coupling within these assemblies is determined by the number of base pairs in the duplex DNA tether; compact assemblies in which tethers are composed of fewer base pairs exhibit plasmon bands that are red-shifted relative to the bands of extended assemblies...

Influence of process parameters on component assembly and drop test performance using a novel Anisotropic Conductive Adhesive for lead-free surface mount assembly

Ramkumar, S. Manian; Srihari, K.
Fonte: IEEE: Proceedings of the 58th Electronic components & technology conference Publicador: IEEE: Proceedings of the 58th Electronic components & technology conference
Tipo: Proceedings
EN_US
Relevância na Pesquisa
26.22%
The novel Anisotropic Conductive Adhesive (ACA) investigated in this research uses a magnetic field to align the conductive particles in the Z-axis direction, during cure, thereby eliminating the need for pressure and the requirement to capture a monolayer of conductive particles. The formation of conductive columns within the adhesive matrix, during cure, provides a very high insulation resistance between adjacent conductors and also eliminates the need for precise printing or dispensing of adhesives onto individual fine pitch pads. The novel ACA can also be mass cured, eliminating the need for sequential component assembly. The formation of columns also alleviates the problems associated with coplanarity errors and varying lead/bump shapes in forming reliable interconnections using traditional ACAs. This research incorporated a variety of components, leaded, leadless and bumped, standard, fine and ultrafine pitch, coarse and fine particle filler formulations, different stencil thicknesses, different cure temperatures and times, and different magnetic flux densities. The print process was performed manually using metal stencils of different thicknesses and metal squeegee blades. The findings from this study, including drop tests of ‘as assembled’ and aged samples (100 hours of thermal and T&H aging) are provided. The filler particle size played a critical role in determining the continuity and the contact resistance of the adhesive joint. Standard pitch devices provided good continuity and contact resistance when assembled with larger diameter filler particles. Fine pitch devices required smaller diameter filler particles. Stencil thickness was found to be a statistically significant factor in determining the contact resistance of the adhesive joint...

Thermal cycle/aging reliability of lead free 0201 assemblies

Ghaffarian, Reza; Ramkumar, S. Manian; Varanasi, Arun
Fonte: IEEE: Proceedings of the 56th Electronic components & technology conference Publicador: IEEE: Proceedings of the 56th Electronic components & technology conference
Tipo: Proceedings
EN_US
Relevância na Pesquisa
26.19%
This paper presents the test results and comparative literature data on the influence of a few key manufacturing parameters and defects associated with the 0201 components using lead-free and tin-lead solder alloys. A large number of test vehicles assembled with 0201 components were subjected to isothermal aging at 150°C and thermal cycling in the range of -55° to 100°C in order to establish their reliability. The shear tests were carried out at various aging intervals up to 500 hours to determine the effects of aging damage on the solder joint strength and this data will be presented and compared to virgin assemblies. Weibull plots will be given for reliability to establish solder joint aging behavior for the lead free assemblies compared to lead based solder as well as data correlation for various sets of data. Optical inspection photos taken during thermal cycling to establish damage progress, scanning electron microscopy (SEM) photos to reveal details of damage at 1500 cycles, and cross-sectional photomicrographs showing interconnect microstructural changes and intermetallic formation will also be presented.; ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists...

Forward and backward compatibility of solder alloys with component and board finishes

Kannabiran, Anand; Pannerselvam, Elavarasan; Ramkumar, S. Manian
Fonte: IEEE: Transactions on Electronics Packaging Manufacturing Publicador: IEEE: Transactions on Electronics Packaging Manufacturing
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
26.4%
The primary objective of the research presented in this paper is to qualify the reliability of mixed assemblies by comparing them to the conventional Sn–Pb assembly and completely Pb-free assembly. The research investigates both forward and backward compatibility in electronic assemblies using a design of experiments (DOE) approach. The investigation utilized a test vehicle containing an area array component (BGA169) and chip components (0603 resistors). Hot air solder leveling (HASL) and organic solderability preservative (OSP) surface finishes were used on the test vehicles to represent Sn–Pb and Pb-free alternatives, respectively. The assembled test vehicles were cut into two panels—one containing a resistor section for isothermal aging and the other containing a BGA and another resistor section for thermal shock. The assemblies were subjected to isothermal aging and thermal shock tests as per Interconnecting and Packaging Electronic Circuits/Joint Electronic Device Engineering Council (IPC/JEDEC) standards. The resistors were sheared in the “as-soldered” condition, and at various isothermal aging intervals and thermal shock cycles. In order to simulate an intermetallic failure in isothermal aging, a reduced shear height (20 m) was used for the shear test. The performance of the resistor solder joints were quantified in terms of the shear force. The performance of the ball grid array (BGA) solder joint during thermal shock testing was quantified in terms of the number of cycles to failure. Experimental results from shear analysis of resistor solder joints show that Pb-free alloy assemblies’ performance is superior to those assembled using Sn–Pb alloy. Also...