Build-up Structure Research Articles

Influence of vacuum and high-temperature on the evolution of mechanical strength and microstructure of alkali-activated lunar regolith simulant

Alkali-activated lunar regolith (AALR) has become one of the most promising lunar building materials, offering the potential to support the construction of large-scale lunar structures. This paper presents a comprehensive experimental investigation on the fresh properties, physical properties, mechanical performance and microstructural characteristics of alkali-activated lunar regolith simulant (AALRS) considering the effects of lunar environments (high-temperature, vacuum and coupled high-temperature and vacuum), alkaline activators (sodium hydroxide and sodium silicate) and curing age. The results show that AALRS under high-temperature environment exhibits higher strength while the strength development is limited. However, AALRS under vacuum environment exhibits lower strength but the strength increases as the curing time increases. In terms of pore structure, the volume fractions of macro voids for SH-V and SS-V account for up to 50.94 % and 63.64 %, respectively, which are 12.22 % and 7.95 % higher than those of SH-H and SS-H. Regarding the impact of coupled high-temperature and vacuum environment, the compressive strength of SH-HV-7 is reduced by 47.8 % compared to that of SH-H-7, while the compressive strength of SS-HV-7 exhibits a 57.2 % increase over that of SS-H-7. The sodium hydroxide-activated (SH-activated) system and sodium silicate-activated (SS-activated) system demonstrate fundamentally intrinsic differences in terms of reaction products, structure build-up and pore structure. The positive optimization mechanism and reverse degradation effect of vacuum environment on the performance of AALRS paste were revealed. Finally, the evolution of structural characteristics of AALRS paste under different environments was elucidated.

Advanced Glass Carriers for Buildup Structure Warp Control and Wafer Ultra-thinning

Tailorable CTE of glass carriers enables effective warp control of buildup structures such as fan-Out wafer level package and multi-layer laminates. Corning’s Advanced Packaging Carrier (APC) product family covers CTE from 4.9-12.6 ppm/C with fine granularity down to 0.2 ppm/C, and other glass types go down in CTE all the way to 0 ppm/C. We illustrate the benefits of having such CTE capabilities using several use cases. Carrier supported wafer thinning down to single digit microns is another emerging need. In addition to CTE matching, such ultra-thinning requires the carrier and the associated temporary bonding method to deliver very low total thickness variation (TTV), typically a small fraction of the final wafer thickness. We will introduce Corning’s recently announced ultra-low-TTV (ULTTV) glass carriers as well as near-zero-TTV temporary bonding methods that enable ultra-thinning of wafers of various types.

Approach Improves Vertical and Areal Sweep in Tengiz Platform Sour-Gas Injection

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203995, “Injection and Production Optimization for Tengiz Platform Sour-Gas Injection by Reactive and Proactive Conformance Completions Control,” by Shusei Tanaka, SPE, and Matthieu Rousset, SPE, Chevron, and Yousef Ghomian, SPE, Tengizchevoil, et al. The paper has not been peer reviewed. _ Sour-gas injection (SGI) operations have been implemented in the Tengiz field since 2008 and will be expanded in a future project. Because of limited gas-handling capacity, production at a high gas/oil ratio (GOR) has posed a challenge, resulting in potential well shutdowns. The objective of the study described in the complete paper was to establish an efficient optimization work flow to improve vertical and areal sweep, thereby maximizing recovery under operational constraints. This will be achieved through conformance-control completions that have been installed in many production and injection wells. Introduction The Tengiz field is in northwestern Kazakhstan on the northeast shore of the Caspian Sea. The reservoir extends 20 km2 with an oil column of approximately 1.6 km in a carbonate buildup structure at 3850 m subsea. Tengiz produced oil has a specific gravity of 47 °API with approximately 13% of hydrogen sulfide (H2S) and 3% CO2 in produced gas. At initial reservoir conditions, the GOR was 2,242 scf/STB and oil viscosity was 0.22 cp. At the time of writing, the production strategy follows gas-injection processes in the central to north platform area while depletion drive exists at the platform margin to the slope, where fractures appear to dominate flow dynamics. The production area is maintained above saturation pressure based on surveillance data for both the platform and slope zones. Tengiz SGI With Vertical Conformance Control The authors write that 20% of produced gas at Tengiz field is reinjected into the central platform area, which consists of the Bashkirian (Bash), Serpukhovian (Serp), and Visean A (VisA) formations. As the volume of injected gas increases, the neighboring producers observe gas breakthrough with increased GOR. The high-GOR wells need to be shut in to achieve maximum oil production in the plant. As the number of shut-in wells increases, however, it becomes challenging to meet plant capacity because of a lack of active producers, resulting in loss of production. To avoid production loss, zonal-production and injection-control capability were introduced through conformance-control completions and use of swell packers and sliding sleeves. With completions closed at a high-GOR interval, oil production is expected to be maintained while gas production from the well is reduced. With the extension of the SGI project, capability will exist to control vertical conformance with the planned completion strategy in 38 producers. In addition, 17 injectors also will have vertical conformance-control capability for selective zonal injections.

Improving carbonate reservoir characterization by applying rock typing methods: a case study from the Nam Con Son Basin, offshore Vietnam

Understanding the permeability-porosity relationships is the key to improving reservoir prediction and exploitation especially in carbonate reservoirs, which are known for their complex textural and diagenetic variation. Rock type classifications have long been proven to be an effective technique for establishing permeability- porosity relationships, enhance the capability to capture the various reservoir flow behavior and prediction for uncored reservoir zones. This study highlights some of those practical and theoretically-correct methods, such as Hydraulic Flow Unit (HFU); Global hydraulic element (GHE), Winland’s R35 method, Pittman method, Lucia method. They are proposed and tested for identification and characterization of the rock types using a database of 555 core plugs from the Miocene carbonate reservoir in the Nam Con Son basin. It is a large isolated carbonate build-up structure which were deposited within a shallow marine platform interior and are dominated by coral, red algal and foraminiferal packstones, wackestones and grainstones. Hydrocarbons in this reservoir have been found in the upper most part of the late Miocene formation. Conventional core data were first used to define and display the cross plot of permeability and porosity. Different charts and cutoff thresholds were used to classified, defined number of rock type and the linear and non-linear equations were established. The predicted core permeability was calculated using different methods and compared with the actual core permeability for each rock type. The predicted reservoir rock type and permeability predictions of HFU method was recognized to give better matching of measured core permeability with coefficient of more than 89%.

New insights on carbon black suspension rheology—Anisotropic thixotropy and antithixotropy

We report a detailed experimental study of peculiar thixotropic dynamics of carbon black (CB, Vulcan XC-72) suspensions in mineral oil, specifically the observation of sequential stress increase then decrease at a fixed shear rate in a step-down test. We verify that such dynamics, though peculiar, come from a true material response rather than experimental artifacts. We also reveal how this long-time stress decay is associated with antithixotropic structural change rather than viscoelastic stress relaxation by using orthogonal superposition (OSP) rheometry to probe viscoelastic moduli during the step-down tests. The orthogonal storage and loss moduli are present, showing this two-timescale recovery then decay response, which demonstrates that this response is antithixotropic, and it involves shear-induced structuring. We further show a mechanical anisotropy in the CB suspension under shear using OSP. Based on the rheological results, a microstructural schematic is proposed, considering qualitatively thixotropic structure build-up, antithixotropic densification, and anisotropic structure evolution. Our observation for these CB suspensions is outside the standard paradigm of thixotropic structure-parameter models, and the elastic response provides us with new insight into the transient dynamics of CB suspensions.

Computer Generated Realistic Interstellar Icy Grain Models: Physicochemical Properties and Interaction with NH3.

Interstellar grains are composed by a rocky core (usually amorphous silicates) covered by an icy mantle, the most abundant molecule being H2O followed by CO, CO2, NH3, and also radicals in minor quantities. In dense molecular clouds, gas-phase chemical species freeze onto the grain surface, making it an important reservoir of molecular diversity/complexity whose evolution leads to interstellar complex organic molecules (iCOMs). Many different models of water clusters have appeared in the literature, but without a systematic study on the properties of the grain (such as the H-bonds features, the oxygen radial distribution function, the dangling species present on the mantle surface, the surface electrostatic potential, etc.). In this work, we present a computer procedure (ACO-FROST) grounded on the newly developed semiempirical GFN2 tight-binding quantum mechanical method and the GFN-FF force field method to build-up structures of amorphous ice of large size. These methods show a very favorable accuracy/cost ratio as they are ideally designed to take noncovalent interactions into account. ACO-FROST program can be tuned to build grains of different composition mimicking dirty icy grains. These icy grain models allow studying the adsorption features (structure, binding energy, vibrational frequencies, etc.) of relevant species on a large variety of adsorption sites so to obtain a statistically meaningful distribution of the physicochemical properties of interest to be transferred in numerical models. As a test case, we computed the binding energy of ammonia adsorbed at the different sites of the icy grain surface, showing a broad distribution not easily accounted for by other more size limited icy grain models. Our method is also the base for further refinements, adopting the present grain in a more rigorous QM:MM treatment, capable of giving binding energies within the chemical accuracy.

Numerical simulation of the experimental behavior of RC beams at elevated temperatures

The danger of fire is present always and everywhere. The imminent danger depends upon the actual type and length of fire exposure. Reinforced concrete structural members are loadbearing components in buildup structures and are therefore at high risk, since the entire structure might potentially collapse upon their failure. Thus, it is imperative to comprehend the behavior of reinforced concrete members at high temperatures in case of fire. In this study, the mechanical properties of concrete exposed to high temperatures were experimentally determined through the testing of 27 concrete cylinder starting at room temperature and increasing up to 260 °C. The concrete material behavior was implemented into the ABAQUS software and a finite simulation of reinforced concrete beams exposed to actual fire conditions were conducted. The finite element models compared favorably with the available experimental results. Thus, providing a valuable tool that allows for the prediction of failure in case of a fire event.

Heteroditopic Calix[6]arene Based Intervowen and Interlocked Molecular Devices.

Since the dawn of supramolecular chemistry, calixarenes have been employed as platforms onto which functional groups and binding sites can be loaded in a regio- and stereocontrolled manner for the recognition of charged and neutral species. Despite their wider annulus, potentially suitable to bind larger guests, the larger members of the calixarene series have been relatively less employed, mainly because of the synthetic difficulties to control their conformational flexibility and their regioselective functionalization. In this account, we will present the achievements gained during the last two decades on the use of the calix[6]arene as a platform to build-up structures in which the macrocycle acts as a wheel for the synthesis of oriented (pseudo)rotaxanes. We also account on how these calix[6]arene hosts affect the reactivity or spectroscopic properties of their bound guests.

Weakly-supervised domain adaptation for built-up region segmentation in aerial and satellite imagery

This paper proposes a novel domain adaptation algorithm to handle the challenges posed by the satellite and aerial imagery, and demonstrates its effectiveness on the built-up region segmentation problem. Built-up area estimation is an important component in understanding the human impact on the environment, effect of public policy and in general urban population analysis. The diverse nature of aerial and satellite imagery (capturing different geographical locations, terrains and weather conditions) and lack of labeled data covering this diversity makes machine learning algorithms difficult to generalize for such tasks, especially across multiple domains. Re-training for new domain is both computationally and labor expansive mainly due to the cost of collecting pixel level labels required for the segmentation task. Domain adaptation algorithms have been proposed to enable algorithms trained on images of one domain (source) to work on images from other dataset (target). Unsupervised domain adaptation is a popular choice since it allows the trained model to adapt without requiring any ground-truth information of the target domain. On the other hand, due to the lack of strong spatial context and structure, in comparison to the ground imagery, application of existing unsupervised domain adaptation methods results in the sub-optimal adaptation. We thoroughly study limitations of existing domain adaptation methods and propose a weakly-supervised adaptation strategy where we assume image level labels are available for the target domain. More specifically, we design a built-up area segmentation network (as encoder-decoder), with image classification head added to guide the adaptation. The devised system is able to address the problem of visual differences in multiple satellite and aerial imagery datasets, ranging from high resolution (HR) to very high resolution (VHR), by investigating the latent space as well as the structured output space.A realistic and challenging HR dataset is created by hand-tagging the 73.4 sq-km of Rwanda, capturing a variety of build-up structures over different terrain. The developed dataset is spatially rich compared to existing datasets and covers diverse built-up scenarios including built-up areas in forests and deserts, mud houses, tin and colored rooftops. Extensive experiments are performed by adapting from the single-source domain datasets, such as Massachusetts Buildings Dataset, to segment out the target domain. We achieve high gains ranging 11.6–52% in IoU over the existing state-of-the-art methods.

Cold Cracking Resistance of Butt Joints in High-Strength Steels with Different Welding Techniques

Investigation results are presented to improve the structural strength (cold crocking resistance) of weld joints in high-strength steels with the yield limit over 600 MPa. The effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and diffusion hydrogen saturation of build-up and fused base metals was experimentally studied. The diffusion hydrogen saturation of build-up (arc and hybrid welding) and fused (laser welding) metals was chromatographically examined. In gas-shielded arc welding, the diffusion hydrogen content in the fused base metal was shown to be limited to the concentration that does not exceed 0.4 ml/100 g due to an increase in the welding speed from 18 to 50 m/h. In laser and hybrid laser-arc welding of high-strength steels with the yield limit over 600 MPa, the diffusion hydrogen content in the fused metal makes up 0.07 and 0.2–0.3 ml/100 g, respectively, regardless of the welding speed. The cold cracking resistance was evaluated by a commonly accepted procedure of special reference butt samples. Optical and transmission microscopic studies permitted of revealing the effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and gaining detailed information on the dislocation density distribution. The relation between the level of local internal stresses and the structural factors of dislocation density distribution in the weld metal was established. In arc and laser welding, local internal stresses were shown to be reduced to the values that do not exceed 0.22 of the theoretical metal strength if the welding speed would make up 50 m/h. In hybrid laser-arc welding at 72–110 m/h, maximum local internal stresses are also less than 0.22 of the theoretical metal strength. An increase in the cold cracking resistance in butt weld joints of high-strength 14KhGN2MD and N-A-XTRA-70 steels was established to be reached due to a low concentration of diffusion hydrogen in fused metal and formation of the fine-grained structure of lower bainite with the uniform dislocation density distribution.

Into the well—A close look at the complex structures of a microtiter biofilm and the crystal violet assay

The microtiter assay is one of the most widely used methods for assessing biofilm formation. Though it has high throughput, this assay is known for its substantial deviation from experiment to experiment, and even from well to well. Since the assay constitutes one of the pillars of biofilm research, it was decided to examine the wells of a microtiter plate directly during growth, treatment, and the steps involved in crystal violet (CV) measurements.An inverted Zeiss LSM 880 confocal laser scanning microscope was used to visualize and quantify biomass directly in the wells of the microtiter plate. Green fluorescent protein-tagged Pseudomonas aeruginosa, PAO1, and live/dead stains were used to assess the structure, state, and position of biomass build-up. Microscopic observations were compared with colony-forming unit (CFU) and CV measurements.The development and the structured architecture of biomass was observed in real-time in the wells. Three-dimensional images of biomass were obtained from all of the microtiter wells; these showed variations from well to well. CV staining showed large variations in remaining biomass, depending on the method selected to remove the supernatant prior to CV staining (i.e. pipetting or manually discarding the fluid by inversion, washed or unwashed wells). Colony-forming unit counts or live/dead staining used to evaluate biomass with or without antibiotic treatment proved imprecise due to aggregation, limited removal of biomass, and overestimation of dead staining.The highly structured microenvironment of biomass in microtiter wells needs to be considered when designing and analyzing experiments. When using microtiter plates, stochastic variation due to growth and handling may lead to flawed conclusions. It is therefore recommended that this assay be used as a screening tool rather than as a stand-alone experimental tool.

Influence of build-up structure on the output of force transducer build-up system

As the primary force standard in the super large force range, force transducer build-up system played an important role to calibrate the build-up force standard with a capacity over 20 MN. To enhance the accuracy of the build-up system, the influence of build-up structure on the output of the build-up system was investigated. The parasitic components, including the side force and the additional moment, in three different build-up structures were analysed, and compared by the finite element simulation. The experiments of three 300 kN build-up systems of the three structures and a 60 MN build-up system were carried out. The experiment showed that the side force and the additional moment applied to the transducer had significant influences on the output of the transducer. The larger side force and additional moment, the larger the position error and the indication error of the BUS were. The side force and the additional moment should be minimized during the build-up structure design. The pendulum used in the build-up system could significantly reduce the additional moment generating on the transducer, especially after the pendulums were fixed on the balanced platen. The special build-up structure with the pendulum fixed on a balanced platen was verified as a proper build-up structure.

Rotation effects of force transducer on the output of the build-up system

To investigate the Rotation effects of the force transducer on the output of the build-up system, a common model about the output of the column type force transducer affected by the parasitic components, including the side force and additional moment, was proposed. Based on the model, the indication error and position error of the build-up system, which was calibrated following different procedures with and without rotating the position of the force transducer, were discussed. The verification experiments were carried out using three 300 kN build-up systems of common build-up structure with various thicknesses of the upper platen as well as a 300 kN and a 60 MN build-up system of a special build-up structure. The results showed that the force transducer loaded in a build-up system had strong rotation effects especially when the stiffness of the build-up structure was low. The rotation effects would cause large uncertainty to the output of the build-up system. The build-up system should be calibrated with testing the force transducers in three uniformly distributed positions over 360° to eliminate the effect and reduce the indication error of the build-up system. The rotation effects of the force transducer had little effect on the position error of the build-up system, which verified that the position error of the build-up system was often much smaller than that of single force transducer. Besides, the stiffness of the build-up structure should be enhanced in the design of the build-up system. The special build-up structure was a proper design to eliminate the rotation effects.

The microstructures and anti-corrosion behavior of the thermal sprayed Hastelloy C276 coating on substrate of Q235 steel

Hastelloy C276 coating was prepared on the substrate of Q235 steel by arc thermal spraying process. The microstructure, microhardness, thermal shock resistance and anti-corrosion of the coating were investigated. The coating exhibits a layered buildup structure with some pores and unmelted particles appearing. There is a distinct and rough interface between the coating and the substrate which increases the contact area between the coating and the substrate. The coating and the substrate were meshed to each other in the boundary, showing a strong bonding. The coating exhibited a strong thermal shock resistance with the substrate of Q235 steel at 600 °C. The microhardness of the surface of the coating is much higher than the microhardness of the surface of the substrate. Uniform corrosion method of laboratory semi-immersion test was used to test the corrosion resistance of C276 coating. The coating exhibited good corrosion resistance in concentrated HCl with a concentration of 36.5%.

Method for the Enhancement of Buildability and Bending Resistance of 3D Printable Tailing Mortar

The innovative 3D printing has been successfully applied to layeredly build-up construction-scale structures through the extrusion of various cementitious materials. Favourable buildability of fresh cement mixture and the hardened properties of the printed structures are essential requirement for the application of 3D concrete printing. This paper firstly proposed a 3D printable cement mixture containing 40% mining tailings. The influence of paste age on the buildability of forty-layer structure was evaluated, as well as the bending resistance of prism specimen sawed from the printed structure. The bonding between layers is a critical factor that influences the structural capacity. In particular, the weak bonding interface formed in the layered extrusion process was identified through high-resolution X-ray CT scanning. It is necessary and desirable for the cement paste to perform both well buildability and mechanical performances. Thereafter, a proper amount of viscosity modify agent (VMA) was used to improve the structural integrity by increasing the contact behaviour between the adjacent extruded layers. Meanwhile, the impact of curing method on the hardened properties of 3D printed structures was accessed. Results indicated that the prepared tailing mortar achieved sufficient buildability to be used in an extrusion-typed 3D printer at the paste age of 45 min. The mould-cast specimens process flexural strength of 7.87 MPa. In contrast, the flexural strength of printed specimens values 5.22 MPa and 12.93 MPa, respectively, after the addition of 1.5% VMA and 90 °C steam curing.

On the effects of roughness on the nonlinear dynamics of a bolted joint: A multiscale analysis

Abstract Accurate prediction of the vibration response of friction joints is of great importance when estimating both the performance and the life of build-up structures. The contact conditions at the joint interface, including local normal load distribution and contact stiffness, play a critical role in the nonlinear dynamic response. These parameters strongly depend on the mating surfaces, where the surface roughness is well known to have a significant impact on the contact conditions in the static case. In contrast, its effects on the global and local nonlinear dynamic response of a build-up structure is not as well understood due to the complexity of the involved mechanisms. To obtain a better understanding of the dependence of the nonlinear dynamic response on surface roughness, a newly proposed multiscale approach has been developed. It links the surface roughness to the contact pressure and contact stiffness, and in combination with a multiharmonic balance solver, allows to compute the nonlinear dynamic response for different interface roughness. An application of the technique to a single bolted lap joint highlighted a strong impact of larger roughness values on the pressure distribution and local contact stiffness and in turn on the nonlinear dynamic response.

Numerical simulation and experimental calibration of additive manufacturing by blown powder technology. Part I: thermal analysis

PurposeThis paper aims to address the numerical simulation of additive manufacturing (AM) processes. The numerical results are compared with the experimental campaign carried out at State Key Laboratory of Solidification Processing laboratories, where a laser solid forming machine, also referred to as laser engineered net shaping, is used to fabricate metal parts directly from computer-aided design models. Ti-6Al-4V metal powder is injected into the molten pool created by a focused, high-energy laser beam and a layer of added material is sinterized according to the laser scanning pattern specified by the user.Design/methodology/approachThe numerical model adopts an apropos finite element (FE) activation technology, which reproduces the same scanning pattern set for the numerical control system of the AM machine. This consists of a complex sequence of polylines, used to define the contour of the component, and hatches patterns to fill the inner section. The full sequence is given through the common layer interface format, a standard format for different manufacturing processes such as rapid prototyping, shape metal deposition or machining processes, among others. The result is a layer-by-layer metal deposition which can be used to build-up complex structures for components such as turbine blades, aircraft stiffeners, cooling systems or medical implants, among others.FindingsAd hoc FE framework for the numerical simulation of the AM process by metal deposition is introduced. Description of the calibration procedure adopted is presented.Originality/valueThe objectives of this paper are twofold: firstly, this work is intended to calibrate the software for the numerical simulation of the AM process, to achieve high accuracy. Secondly, the sensitivity of the numerical model to the process parameters and modeling data is analyzed.

Rheological behaviour of hydraulic lime-based grouts. Shear-time and temperature dependence

This paper deals with the coupled effect of temperature and fly ash (FA) addition on rheological behaviour of natural hydraulic lime (NHL5) based grouts, currently used in masonry consolidation. The use of a grout injection technique for masonry consolidation may lead to an increase of hydrostatic pressure and lead to structural damage. This means that the thixotropic effects become self-evident in grout design. It was shown that there is a relation between the structuration rate of each grout and the pressure that occurs inside masonry during its consolidation. According to the results, it seems also that there is a grout threshold temperature (Tlimit) that separates a domain where the grout build-up structure area is almost constant, from another where flocculation area starts to increase significantly. We believe that in the first region the thixotropic effects are almost isolated from the irreversible effects (due to hydration). For the NHL5 based grout Tlimit = 20 °C and for the grout with NHL5 + 15 % of FA Tlimit = 15 °C. Grouts' characterization based on maximum resisting time, structuration rate and on the analysis of the hydraulic lime grout behaviour tested at different shear rates was performed using a shear thinning model and assuming that the structure is shear- and time-dependent. The goal is to use this methodology during mix proportioning and design for masonry injection purpose. The tested grout compositions were optimized compositions obtained in previous research using the design of experiments method.

Methodological approach to assess the socio-economic vulnerability to wildfires in Spain

The potential impacts of fire are spatially-dependent, according to the ecosystems, people and properties at risk. This study aimed to develop a methodology for the assessment of the socio-economic vulnerability to fire using Geographic Information Systems. We have conducted the vulnerability assessment by estimating the potential losses fire might cause during the time required for the recovery of the pre-fire environmental conditions.We have considered that vegetation recovery time depends on the vegetation’s structure, the reproductive strategy and the influence of constraining factors such as water availability, soil loss, fire frequency and fire intensity.Regarding the socioeconomic values at risk, three categories of impact have been assessed. The impact on properties consisting of the potential destruction of build-up structures situated in the wild land-urban interface. The impact on people, i.e.: the probability of wildfires causing victims. The third category of impact embraces losses of environmental services because of the potential interruption of the productive, ecologic and recreational function of the affected ecosystems. Conventional economic valuation methodologies (revealed or declared preference techniques) were applied.The application of the developed methodology to the case of continental Spain has resulted in several cartographic products (at a 1km2 resolution), thus presenting in a spatially explicit way the vulnerability of the territory to fire in different socio-economic aspects. According to the results, the average benefits derived from effective fire prevention measures because of avoided damages to properties, human life and ecosystems are 376,584 TEUR km−2, 9.17TEURkm−2 and 22.29TEURkm−2, respectively (TEUR=1000 EUR).

Control of Package Warpage by Package Substrate Design for Low Profile Package-on-Package Structure

In recent years, with increasing demand for high-density assembly in mobile electronics products, a package-on-package (PoP) structure has been standardized. The demand for lowering the PoP profile is getting stronger as consumers demand thinner mobile devices. To assemble a low profile PoP and mount it on a mother board, it is necessary to have a precise warpage control of PoP components, including its bottom package. It is expected that a flip-chip chip-scale-package (FCCSP) with thin mold cap will be used as the bottom package of the PoP in the next 2–3 years. In order to control the package warpage, it is necessary to optimize a large number of parameters related to the package substrate, silicon die and mold compound. Among them, equivalent coefficient of thermal expansion (CTE) of the package substrate is one of the most important factors. In this paper, control of the package warpage was studied by focusing on the glass-cloth content ratio in the package substrate. Glass-cloth has the lowest CTE among the constituent materials of the substrate, so it contributes to reduce the equivalent CTE of the substrate. To maximize the glass-cloth content, a substrate with a thick core and thin build-up structure was prepared, and the package with thin mold cap was subsequently formed. Compared with a similar package with a conventional substrate structure, its warpage, measured experimentally, was about 20% smaller. Consequently, it was concluded that the glass-cloth content ratio is a key factor to control package warpage behavior in the PoP assembly process.