Experimental In Situ Characterization and Creep Modeling of Tin-Based Solder Joints on Commercial Area Array Packages at −40 °C , 23 °C , and 125 °C

2004 ◽  
Vol 127 (4) ◽  
pp. 430-439 ◽  
Author(s):  
Ahmad Abu Obaid ◽  
Jay G. Sloan ◽  
Mark A. Lamontia ◽  
Antonio Paesano ◽  
Subhotosh Khan ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Constitutive Model ◽  
Solder Ball ◽  
Solder Joints ◽  
Shear Loading ◽  
Area Array ◽  
Commercial Area ◽  
Wide Range ◽  
Solder Balls

The objective of this work was to experimentally determine the in situ creep behavior and constitutive model equations for a commercial area array package and printed wiring board assembly at −40, 23, and 125 °C through shear loading. The chip is connected to the printed circuit board by means of solder joints made of 62%Sn–36%Pb–2%Ag alloy. It was shown that the creep rate of solder ball arrays could be investigated using a stress relaxation method. Under the shear relaxation mode, the creep strain increases with temperature and can be described by a power law model with coefficients determined by finite element modeling (FEM). An analytical model was developed to describe the stress relaxation of an array with an arbitrary number of solder balls by defining an equivalent solder ball shear area as a fitting parameter. The resulting constitutive model is in excellent agreement with both FEM and experimental results at all test temperatures. A parametric study is conducted to investigate the creep response as a function of temperature for arrays consisting of a wide range of solder balls.

Test Method Development to Quantify the In Situ Elastic and Plastic Behavior of 62%Sn–36%Pb–2%Ag Solder Ball Arrays in Commercial Area Array Packages at −40 °C , 23 °C, and 125 °C

2005 ◽  
Vol 127 (4) ◽  
pp. 483-495 ◽  
Author(s):  
Ahmad Abu Obaid ◽  
Jay G. Sloan ◽  
Mark A. Lamontia ◽  
Antonio Paesano ◽  
Subhotosh Khan ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Solder Ball ◽  
Method Development ◽  
Failure Modes ◽  
Test Methods ◽  
Shear Loading ◽  
Test Method ◽  
Plastic Behavior ◽  
Area Array

The objective of this study is to describe and evaluate test methods developed to experimentally characterize the in situ mechanical behavior of solder ball arrays connecting printed wiring boards to area array packages under tensile, compressive, and shear loading at −40, 23, and 125 °C. The solder ball arrays tested were composed of 62%Sn–36%Pb–2%Ag solder alloy. Finite element modeling was performed. The results indicated that the test fixture should be geometrically equivalent to the projected shape of the ball grid array to achieve uniform loading. Tension, compression, and shear tests were conducted. For tensile loading the interfaces and the solder balls are loaded in series resulting in a large apparent strain (13%). Various interfacial failure modes are observed. Under compression and shear loading the effect of the interfaces are negligible and therefore a significant deformation and a remarkable yielding behavior of solder ball arrays can be observed. Furthermore, the specimens tested under shear loading showed different failure modes such as cohesive or adhesive failure modes depending on the test temperature. From the overall results, it has been determined that shear loading is the most representative test to measure the actual mechanical behavior of solder in ball grid arrays.

Thermal Shock and Drop Test Behaviour of Area Array Packages in Forward and Backward Compatible Assemblies

2009 ◽  
Author(s):  
Bankeem V. Chheda ◽  
Sathishkumar Sakthivelan ◽  
S. Manian Ramkumar ◽  
Reza Ghaffarian
Keyword(s):  
Solder Ball ◽  
Lead Free ◽  
Lead Free Solder ◽  
Mechanical Shock ◽  
Lead Frame ◽  
Shock Test ◽  
Area Array ◽  
Snpb Solder ◽  
Solder Balls ◽  
Free Solder

With lead-free implementation it is important to examine the behaviour of the solder joint at the component level and at the board level. Assembly related issues along with component reliability are the main focus of this experimental research. This experimental study aims to evaluate the mechanical integrity of solder joints comprising of both lead-free and SnPb alloys. Lead-free and SnPb solder pastes were used to assemble the components. This will allow us to check the forward and the backward compatibility of the solder alloys. The test vehicle considered for this study contained a variety of components such as ultra chip scale package (UCSP192), package on package (PoP), plastic ball grid array (PBGA-676 & 1156), very thin chip array BGA (CVBGA432), thin small outline package (TSOP-40 & 48), dual row micro-lead frame (DRMLF), micro-lead frame (MLF-36 & 72), and chip resistors (0201, 0402, 0603). The scope of this paper is limited to the performance evaluation for area array packages only. Solder ball alloy for the area array packages included SAC 305, SAC405, SAC105, SnAg and SnPb. Three different PCB surface finishes, electroless nickel immersion gold (ENIG), SnPb hot air solder level (HASL), and immersion silver (ImAg) were used. Different solder ball alloys and surface finish combinations provided good comparison data for investigating the assembly performance. The PCB assemblies were subjected to mechanical shock test in the as-soldered condition and also after 200 and 500 thermal shock cycles at −55 to 125°C. For the mechanical shock test, the assemblies were subjected to 30 drops from a height of 3 ft, generating an average G force of 485N. After each drop the components were checked for the continuity of the total daisy chain. The number of drops for the first failure was used in analyzing the performance of the components for various combinations. Since each component had many independent daisy chains, the failure of the individual daisy chains was later used in determining the location of the failure and how it progressed. Two sets of test vehicles were assembled. One set comprised of components with lead-free solder balls of different composition (SAC305, SAC405, SAC105, SnAg) and the other set comprised of components with lead-free solder balls and SnPb solder balls (SAC305, SAC405, SnPb). This mix of alloy composition provided adequate data for comparison. It was critical to optimize the process in order to enable the melting of the mix of alloys. The area array package performance was evaluated when assembled with lead-free and SnPb solder paste. Some of the assemblies were cross-sectioned after the tests and the microstructure of the solder joint was analyzed to study the possible cause for assembly failure.

Damage Initiation and Propagation in Voided Joints: Modeling and Experiment

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Leila Jannesari Ladani ◽  
Abhijit Dasgupta
Keyword(s):  
Thermal Cycling ◽  
Solder Ball ◽  
Solder Joints ◽  
Thermal Cycling Test ◽  
Damage Initiation ◽  
Damage Propagation ◽  
Cycling Test ◽  
Initiation And Propagation ◽  
Solder Balls ◽  
Accelerated Thermal Cycling

This study examines damage initiation and propagation in solder joints with voids, under thermomechanical cyclic loading. An accelerated thermal cycling test is conducted on printed wiring assemblies (PWAs) containing 256 input/output (I/O) plastic ball grid arrays (PBGAs) with voided solder joints. Destructive and nondestructive failure analyses of the solder balls are used to detect the presence of voids and to relate the extent of damage propagation to the number of thermal cycles. Particular cases of voided and damaged joints are selected from these tests, to guide the development of a strategy for modeling damage propagation, using a three dimensional global-local finite element analysis (FEA). The displacement results of the global FEA at the top and bottom of the selected solder balls are used as the boundary conditions in a local FEA model, which focuses on the details of damage initiation and propagation in the individual solder ball. The local model is error seeded with voids based on cases selected in experiment. The damage propagation rate is monitored for all the cases. The technique used to quantify cyclic creep-fatigue damage is a continuum model based on energy partitioning. A method of successive initiation is used to model the growth and propagation of damage in the selected case studies. The modeling approach is qualitatively verified using the results of the accelerated thermal cycling test. The verified modeling technique described above is then used for parametric study of the durability of voided solder balls in a ChipArray Thin Core BGA with 132 I/O (CTBGA132) assemblies, under thermal cycling. The critical solder ball in the package is selected and is error seeded with voids with different sizes and various distances from damage initiation site. The results show that voids in general are not detrimental to thermal cycling durability of the CTBGA132 assembly, except when a large portion of the damage propagation path is covered with voids. Small voids can arrest the damage propagation, but generally do not provide a significant increase in durability because the damage zone deflects around the void and also continues to propagate from other critical regions in the solder ball.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Site specific agricultural soil management with the use of new technologies

2013 ◽  
Vol 16 (1) ◽  
pp. 59-67
Keyword(s):  
New Technologies ◽  
Digital Interface ◽  
Appropriate Treatment ◽  
Wide Range ◽  
Soil Variation ◽  
Soil Information ◽  
Remote Sensing Techniques ◽  
Agricultural Areas

<p>The Soil Science Institute of Thessaloniki produces new digitized Soil Maps that provide a useful electronic database for the spatial representation of the soil variation within a region, based on in situ soil sampling, laboratory analyses, GIS techniques and plant nutrition mathematical models, coupled with the local land cadastre. The novelty of these studies is that local agronomists have immediate access to a wide range of soil information by clicking on a field parcel shown in this digital interface and, therefore, can suggest an appropriate treatment (e.g. liming, manure incorporation, desalination, application of proper type and quantity of fertilizer) depending on the field conditions and cultivated crops. A specific case study is presented in the current work with regards to the construction of the digitized Soil Map of the regional unit of Kastoria. The potential of this map can easily be realized by the fact that the mapping of the physicochemical properties of the soils in this region provided delineation zones for differential fertilization management. An experiment was also conducted using remote sensing techniques for the enhancement of the fertilization advisory software database, which is a component of the digitized map, and the optimization of nitrogen management in agricultural areas.</p>

Indium Bromide-catalyzed Unprecedented Hydrogenolysis: A Novel One-Pot Synthesis of Per-O-Acetylated β-carboxymethyl O and S-glycosides

2020 ◽  
Vol 24 (8) ◽  
pp. 900-908
Author(s):  
Ram Naresh Yadav ◽  
Amrendra K Singh ◽  
Bimal Banik
Keyword(s):  
Asymmetric Synthesis ◽  
Chiral Auxiliary ◽  
Bioactive Molecules ◽  
One Pot ◽  
Enantiomerically Pure ◽  
Stereoselective Glycosylation ◽  
One Pot Synthesis ◽  
Wide Range

Numerous O (oxa)- and S (thia)-glycosyl esters and their analogous glycosyl acids have been accomplished through stereoselective glycosylation of various peracetylated bromo sugar with benzyl glycolate using InBr3 as a glycosyl promotor followed by in situ hydrogenolysis of resulting glycosyl ester. A tandem glycosylating and hydrogenolytic activity of InBr3 has been successfully investigated in a one-pot procedure. The resulting synthetically valuable and virtually unexplored class of β-CMGL (glycosyl acids) could serve as an excellent potential chiral auxiliary in the asymmetric synthesis of a wide range of enantiomerically pure medicinally prevalent β-lactams and other bioactive molecules of diverse medicinal interest.

scholarly journals A Generalization Performance Study Using Deep Learning Networks in Embedded Systems

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1031
Author(s):  
Joseba Gorospe ◽  
Rubén Mulero ◽  
Olatz Arbelaitz ◽  
Javier Muguerza ◽  
Miguel Ángel Antón
Keyword(s):  
Deep Learning ◽  
Embedded Systems ◽  
Embedded System ◽  
General Purpose ◽  
Learning Networks ◽  
Performance Study ◽  
Learning Techniques ◽  
Wide Range ◽  
Learning Architectures

Deep learning techniques are being increasingly used in the scientific community as a consequence of the high computational capacity of current systems and the increase in the amount of data available as a result of the digitalisation of society in general and the industrial world in particular. In addition, the immersion of the field of edge computing, which focuses on integrating artificial intelligence as close as possible to the client, makes it possible to implement systems that act in real time without the need to transfer all of the data to centralised servers. The combination of these two concepts can lead to systems with the capacity to make correct decisions and act based on them immediately and in situ. Despite this, the low capacity of embedded systems greatly hinders this integration, so the possibility of being able to integrate them into a wide range of micro-controllers can be a great advantage. This paper contributes with the generation of an environment based on Mbed OS and TensorFlow Lite to be embedded in any general purpose embedded system, allowing the introduction of deep learning architectures. The experiments herein prove that the proposed system is competitive if compared to other commercial systems.

scholarly journals Global soil moisture data derived through machine learning trained with in-situ measurements

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sungmin O. ◽  
Rene Orth
Keyword(s):  
Machine Learning ◽  
Soil Moisture ◽  
Large Scale ◽  
Short Term Memory ◽  
Temporal Dynamics ◽  
Soil Moisture Data ◽  
Wide Range ◽  
Global Soil

AbstractWhile soil moisture information is essential for a wide range of hydrologic and climate applications, spatially-continuous soil moisture data is only available from satellite observations or model simulations. Here we present a global, long-term dataset of soil moisture derived through machine learning trained with in-situ measurements, SoMo.ml. We train a Long Short-Term Memory (LSTM) model to extrapolate daily soil moisture dynamics in space and in time, based on in-situ data collected from more than 1,000 stations across the globe. SoMo.ml provides multi-layer soil moisture data (0–10 cm, 10–30 cm, and 30–50 cm) at 0.25° spatial and daily temporal resolution over the period 2000–2019. The performance of the resulting dataset is evaluated through cross validation and inter-comparison with existing soil moisture datasets. SoMo.ml performs especially well in terms of temporal dynamics, making it particularly useful for applications requiring time-varying soil moisture, such as anomaly detection and memory analyses. SoMo.ml complements the existing suite of modelled and satellite-based datasets given its distinct derivation, to support large-scale hydrological, meteorological, and ecological analyses.

scholarly journals Quantification of assembly forces during creation of head-neck taper junction considering soft tissue bearing: a biomechanical study

Arthroplasty ◽  
2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Toni Wendler ◽  
Torsten Prietzel ◽  
Robert Möbius ◽  
Jean-Pierre Fischer ◽  
Andreas Roth ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Work Experience ◽  
Soft Tissues ◽  
Force Sensor ◽  
Biomechanical Study ◽  
Measuring System ◽  
Wide Range ◽  
Head Neck

Abstract Background All current total hip arthroplasty (THA) systems are modular in design. Only during the operation femoral head and stem get connected by a Morse taper junction. The junction is realized by hammer blows from the surgeon. Decisive for the junction strength is the maximum force acting once in the direction of the neck axis, which is mainly influenced by the applied impulse and surrounding soft tissues. This leads to large differences in assembly forces between the surgeries. This study aimed to quantify the assembly forces of different surgeons under influence of surrounding soft tissue. Methods First, a measuring system, consisting of a prosthesis and a hammer, was developed. Both components are equipped with a piezoelectric force sensor. Initially, in situ experiments on human cadavers were carried out using this system in order to determine the actual assembly forces and to characterize the influence of human soft tissues. Afterwards, an in vitro model in the form of an artificial femur (Sawbones Europe AB, Malmo, Sweden) with implanted measuring stem embedded in gelatine was developed. The gelatine mixture was chosen in such a way that assembly forces applied to the model corresponded to those in situ. A study involving 31 surgeons was carried out on the aforementioned in vitro model, in which the assembly forces were determined. Results A model was developed, with the influence of human soft tissues being taken into account. The assembly forces measured on the in vitro model were, on average, 2037.2 N ± 724.9 N, ranging from 822.5 N to 3835.2 N. The comparison among the surgeons showed no significant differences in sex (P = 0.09), work experience (P = 0.71) and number of THAs performed per year (P = 0.69). Conclusions All measured assembly forces were below 4 kN, which is recommended in the literature. This could lead to increased corrosion following fretting in the head-neck interface. In addition, there was a very wide range of assembly forces among the surgeons, although other influencing factors such as different implant sizes or materials were not taken into account. To ensure optimal assembly force, the impaction should be standardized, e.g., by using an appropriate surgical instrument.

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