Build-up Structure Research Articles

Advanced damage tolerance and risk analysis methodologies and tools for aircraft structures containing multiple-site and multiple-element fatigue damages

This article presents the results obtained from the development of advanced damage tolerance analysis (DTA) and risk analysis methodologies and tools for aircraft structures, including build-up structures containing multiple-site fatigue damage (MSD) and multiple-element damage, to support the Canadian Forces aircraft structural life cycle management. The DTA methods developed include new closed-form solutions and generic finite element (FE) based tools to calculate the stress intensity factors and the β-solutions for build-up structural configurations. To facilitate the risk assessment, an in-house crack growth analysis program, CanGROW, was developed to simultaneously grow multiple cracks. Guidelines were established to calculate the residual strength of structures with MSD and multiple-element damage using global and/or local FE models, considering load redistribution among adjacent components. For the MSD risk analysis, an efficient Monte Carlo simulation technique was developed to determine the crack size distributions at different inspection intervals, which were then used in National Research Council Canada’s risk analysis code probabilistic damage tolerance analysis to calculate the single flight hour probability of failure. Case studies on critical locations of the CC-130 centre wing structure are presented to demonstrate the capability of the developed methods and tools.

PHP34 Pricing Insights Across Therapy Areas and European Countries - A Discussion of International Price References and Implications for Parallel Trade and Prescription Patterns of Pharmaceutical Products

This analysis compares pricing levels across 15 European countries and 10 therapy areas in 2010. The differences in the price levels are related to parallel imports and the innovativeness of prescriptions. From IMS PRICING INSIGHTS pricing information for pharmaceutical products is accessed at the pack level from 15 countries (EU5-Austria-Ireland-Sweden-Norway-Denmark-Portugal-Greece-Poland-Hungary-Romania) for 2010. Currency rates are fixed at 2010 levels. For the ten therapy areas, product baskets are constructed for the comparisons: The therapy areas are defined as Anatomic-Therapeutic-Chemical (ATC) classes at level 2. The top 100 products by sales in the EU5 in these classes enter the comparisons. Prices are compared at the manufacturer and the public sales levels. IMS MIDAS identifies imports related to the products in the baskets. The innovativeness of products is operationalized as the number of months between the overall first introduction and the introduction in the countries. The first result is that international drug price comparisons are extremely sensitive to methodological issues, e.g. sample selection, exchange rates. Differences in price build-up structures between countries would dominate cross-country price differences, if not accounted for. Differences between countries exist at the ex-manufacturer-level, differences between public sales levels tend to be larger. Price level differences between countries are not consistent across all analyzed therapy areas. Higher price levels are related to parallel trade rates across countries and to an earlier access to new pharmaceutical products. The analysis shows price differences across countries related to manufacture pricing and regulation structuring the price build-up and taxes. Higher price levels are linked to an earlier access to innovative products. Parallel trade flows into countries with higher price levels, usually from countries with lower price levels, causing scarcities. Differences in economic development and purchasing powers need to be analyzed to evaluate these differences in pricing levels.

The use of the marasha ard plough for conservation agriculture in Northern Ethiopia

Indigenous tillage systems are often undervalued in conservation agriculture (CA). In Ethiopia, since the 1970s there have been several attempts to develop and implement often major modifications to the marasha, the traditional ox-drawn ard plough, with the main aim of creating various types of surface depressions. The establishment of furrows and ridges increases soil moisture and grain yield and reduces soil loss. Dissemination of the modified tools, however, remains limited. Recent tendencies are towards testing relatively simple conservation agriculture tools. Major challenges remain, however; the need for capacity building and problems in marketing the tools. From experimental plots, often worked with exotic tools, there is a long road to real adoption by farmers. Rather than developing yet another CA tool, we investigate whether CA-based resource-conserving technologies might be achieved successfully with simple changes to the use of the marasha. On-farm observations on traditional conservation techniques were carried out throughout the northern Ethiopian highlands, and experiments were conducted involving resource-conserving technologies. Farmers traditionally use the marasha ard plough for various types of in situ soil and water conservation by creating surface depressions, either at the moment of sowing (terwah, derdero) or after crop emergence (shilshalo). Building upon this indigenous knowledge, we further developed resource-conserving technologies into a system named derdero+, whereby the traditional ard plough was found suitable for a bed-and-furrow system. From the socio-economic point of view, implementation of permanent beds and retention of stubble leads to decreased oxen (and straw) requirements, but also to an increased need for weeding in the first years. To overcome that problem, we introduced glyphosate herbicide into the tillage system. The decreased runoff (-51%) and soil loss (-81%) allow protection of the downslope areas from flooding, but soil nutrient build-up and soil structure improvement are slow processes, and hence the full benefit of the permanent bed system can only be expected after some years. Overall, this type of resource-conserving technology can be part of the ongoing intensification process which includes physical soil and water conservation, slope reforestation and irrigation development. It has, however, its own niche: the cropped land sensu stricto, i.e. the most important part of the land, both for the farmer and for a nation that is striving for long-term food security.

Rheological characterization of a time dependent fresh cement paste

Combining equilibrium and non-equilibrium rheological tests, the yield stress and the plastic viscosity corresponding to the completely build-up structure of a fresh cement paste have been determined. This experimental method is proposed to characterize time-dependent fluids because the values of these parameters are not dependent on the particular structural state of the system and, consequently, are not affected by the particular way in which the rheological test has been designed.

Estimation of Welding Distortion Using Neural Network

Recently, the prediction of welding distortion of steel structure has been carried out widely. Though the thermal elastic-plasticity finite element method (FEM) analysis is usually required to ensure the accuracy of the estimation, technical knowledge is required, and long computing time is necessary. In this study, simplification of the prediction was done using a neural network model, in which the calculation result of the FEM analysis was incorporated in teacher data, for the fillet welding of T-type buildup structure, etc. This program would be able to estimate the welding distortion of the joint with different dimensions and welding conditions in a simple manner.

A Novel Package-on-Package Technology Using Coreless Substrate with Cu Posts

We have successfully developed a novel Package-on-Package (PoP) technology for achieving small package thickness and low package warpage. The novel package structure is based on an ultra-thin coreless substrate, called a Multi-Layer Thin Substrate (MLTS) . The MLTS is fabricated by completely removing the Cu base plate after forming a high-density buildup structure on the base plate. In this paper, however, the Cu posts are formed by selective wet etching of the Cu base plate. Since the novel package has built-in Cu posts as external terminals, the overall substrate can be molded for the peripheral area as well as the chip mounting area. This paper also describes how two types of novel wet etching processes have been developed for obtaining narrower pitch and higher aspect ratio. Through the novel wet etching process, we achieve Cu posts of 0.5 mm pitch and high aspect ratio of 6.0, which cannot be realized by wet etching. A prototype package has 361 pads arranged in 5 rows with 0.5 mm pitch, and the thickness is only 0.23 mm.

Novel Ceramic Composite Substrates for High-Density and High Reliability Packaging

This paper presents the development and evaluation of a large-area carbon-silicon carbide (C-SiC) based composite board material that has the advantages of organic boards in terms of large-area processability and machinability at potentially low-cost while retaining the high stiffness (> 200 GPa) and Si-matched coefficient of thermal expansion (CTE) (~ 2.5 ppm/degC) of ceramics. Test vehicles were fabricated using C-SiC boards for assessing ultra-fine pitch solder joint reliability without underfill as well as the reliability of high-density wiring with microvias on the board. Finite element reliability models were developed to simulate the thermomechanical behavior of test vehicles. From the finite-element simulations as well as accelerated reliability tests, the high stiffness low-CTE C-SiC boards did not show any premature solder joint fatigue failure or dielectric cracking. Furthermore, the C-SiC boards show minimal via-pad misalignment and support the multilayer buildup structure required to achieve very high wiring density. The modeling and experimental results suggest that the low-cost large-area ceramic matrix composite (C-SiC) has superior thermomechanical properties, and is, therefore, a promising candidate substrate material for the emerging microelectronic systems.

Structure assembling by stochastic topology optimization

Topology optimization is of significant importance to the design of truss- and grillage-like structures. Conventional topology optimization procedures are usually based on the ground structure approach. Starting from highly connected structures the uneconomical links are eliminated during the course of optimization. In this paper we show that, additionally, stochastic methods offer the possibility to build-up structures starting from simple initial configurations with few elements. Stochastic optimization methods (simulated annealing, evolutionary algorithms, random cost) are applied to the topology design problem on the basis of appropriate local structure variations. Results and performance comparisons are given.

Ultra-thin high-density LSI packaging substrate for advanced CSPs and SiPs

An ultra-thin high-density LSI packaging substrate, called multi-layer thin substrate (MLTS), is described. It meets the demand for chip scale packages (CSPs) and systems in a package (SiPs) for use in recently developed small portable applications with multiple functions. A high-density build-up structure is fabricated on a Cu plate, which is then removed, leaving only an ultra-thin, high-density multi-layer substrate. MLTS has (1) excellent registration accuracy, which enables higher density and finer pitch patterning due to the use of a rigid, excellent-flatness Cu base plate; (2) a thinner multi-layer structure due to the use of a core-less multi-layer structure; (3) excellent reliability, supported by the use of an aramid-reinforced epoxy resin dielectric layer; and (4) a cost-effective design due to the use of fewer layers fabricated using a conventional build-up process. A prototype high-density CSP (0.4-mm pitch/288 pins/4 rows/10 mm 2) was fabricated using a 90-μm-thick MLTS (with a solder resist layer). Testing demonstrated that it had excellent long-term reliability. A prototype ultra-thin, high-density SiP (0.5-mm pitch/225 pins/11 mm 2/0.93 mm thick) was also fabricated based on MLTS. MLTS consists of only two conductor layers (total thickness: 90 μm) while an identical-function build-up printed wiring board needs four conductor layers (total thickness: 300 μm). With its thinner core-less multi-layer structure, MLTS enables the fabrication of ultra-thin, high-density SiPs.

Explicit calculations of homoclinic tangles in tokamaks

Explicit numerical calculations of homoclinic tangles are presented for a physically realistic model of a resonantly perturbed magnetic field in a tokamak. The structure of these tangles is consistent with that expected from the general theory of near-integrable Hamiltonian systems commonly studied with simple algebraic twist map models. In addition, understanding the structure of homoclinic tangles corresponding to the primary separatrix of a poloidally diverted tokamak allows one to make predictions of the locations and structure of magnetic footprints and heat buildup on the tokamak wall. These separatrix tangles undergo an interesting bifurcation sequence as the current through a set of error field correction coils is increased. Since this model of the magnetic field is very realistic, these features are expected to be experimentally verifiable.

Buildup of Exponentially Growing Multilayer Polypeptide Films with Internal Secondary Structure

The buildup and secondary structure of poly(l-glutamic acid)/poly(allylamine) (PGA/PAH) multilayer films were investigated by means of optical waveguide lightmode spectroscopy, quartz crystal microbalance, and Fourier transform infrared spectroscopy in attenuated total reflection mode. The thickness and the mass of these films grow exponentially with the number of deposited bilayers. Moreover, PGA undergoes a random/α-helix transition when interacting with PAH during the film buildup process. This structural transition leads to (PGA/PAH)i films with an α-helix content (contribution of the α-helices to the amide I band) that switches regularly between 30% and 40% during the film buildup, when the multilayer is alternatively brought into contact with the PAH and PGA solutions. The secondary structure of the film is thus entirely driven by the last deposited layer. The independence of the α-helix content with the number of deposited bilayers also strongly suggests that the film is structurally homogeneous over its whole thickness.

The effect of sputtered interface metallic layers on reinforced core laminate making build-up structures

In conventional printed circuit board manufacturing, pressure and heat are used to attach the copper layer to the laminate. To achieve narrow lines the additive method is used instead. To produce the seed metal, a palladium bath is quite often used. This method is used in conventional PCB production. In our paper we suggest a new method of arriving at a very thin and even surface by sputtering. The sputtering process is done in a simple chamber with an argon atmosphere. The process is rapid (only few tens of seconds) and inexpensive, since the produced layer is very thin. This sputtered metal acts as an adhesion layer, and copper can be grown on this layer either through electrolysis or by electroless means. In the adhesion test, the sputtered and copper-coated specimens were subjected to a peel strength test. It has been noted that the adhesion of sputtered metal to the epoxies differs greatly depending on the metal used. The effects of heating after sputtering have also been identified. It has also been noted that the treatment of the surface has a significant effect on adhesion. In this paper we describe the sputtering method, the results of the peel strength tests and the treatments, which act on the adhesion of the metal to the base laminates.

Active Beam Cross-Sectional Modeling

A finite-element based analysis formodeling initially twisted and curved active composite beams with embedded anisotropic actuation is presented. It is derived from three-dimensional electroelasticity, where the original problem is reduced via the variational asymptotic method. The resulting cross-sectional analysis takes into consideration passive and active anisotropic and nonhomogeneous materials, and can model general (thin-walled, thick-walled, solid, build-up structure) cross-sectional geometries. The formulation requires neither the costly use of three-dimensional finite element discretization nor the loss of accuracy inherent to any simplified representation of the cross section. The developed formulation is numerically implemented in the Active Variational-Asymptotical Beam Section Analysis code (VABS-A), and several numerical and experimental tests cases are used to support validation of the proposed theory. Also, the effect of the presence of a foam core in originally hollow configurations is presented and counter-intuitive conclusions are discussed. The generality of the method and accuracy of the results increase confidence at the design stage that the active beam structure will perform as expected and, consequently, should lower costs from experimental tests and further adjustments.

Object-oriented approach to interactive analysis of structures

The paper presents a novel, object-oriented (O-O) approach to structural modeling and analysis to enable interactive, virtual prototyping in the next generation of the design environment. The interactivity of analysis of build-up structures can only be achieved by re-using results of component analyses, therefore, the applicability of data based analysis to the O-O approach is investigated in this paper. An object in the O-O approach is a neurocomputing model of a structural component developed for a given set of parameterized design variables, loading, and “smart” connectors. Such connectors define how the given component is connected to the assembly, and what is the validity of such a connection. Since component models can be subject to affine transformations, a family of similar structural components is available for modeling. Neurocomputing models are used to enable data based analysis, because they can relate any design variables and load conditions to the selected system response. The applicability of feed-forward and feature-sensitive neural nets is examined in this context. Object-oriented modeling is illustrated with a design of an assembly of beams using a single-point (SP) connector and an assembly of plates subject to a thermal load using a multi-point (MP) connector.

Very compact thin power amplifier module for gigahertz-bandcellular systems

A power amplifier module for gigahertz-band cellular phone systems, developed using a build-up structure based on MCM-D technology and all planar passive circuit components, is investigated. It is shown that the very compact thin module can be incorporated with a thickness of < 1 mm and a volume of < 0.1 cc.

Estimation Method of Residual Stress Distribution and Fatigue Life Takaing the Effect of Welding Procedure Sequence into Consideration in Welded Build-up Structures

It is known that fatigue strength is affected by stress concentration depended on local shape of weld toe and welding residual stress. Fatigue strength of welded build-up structures decreases considerably because there are large tensile residual stresses and stress concentration at the fatigue crack initiation part in these structures.Authors showed that fatigue strength of the corner boxing joints and continuous fillet weld joints with load carrying girder increases very much by turning the tensile residual stress to compressive ones. Flame line heating on appropriate part enables to change the residual stress distribution. These results show that residual stress has a considerable influence on fatigue strength of welded build-up structures.Residual stress at the fatigue crack initiation part depends on welding procedure sequence near this part. Because the change of welding sequence means the change of thermal cycle given into this part by welding.The purpose of this paper makes clear the effect of welding procedure sequence on residual stress distribution and fatigue strength. Two different welding sequence specimens which have continuous fillet weld joints with load carrying girder were used. One of fatigue crack initiation part is the toe of final welding. The other is different part from final welding.Residual stress and fatigue life was investigated by using these specimens. Moreover, the estimation of residual stress distribution taking the welding sequence into consideration was carried out by using elastic finite element analysis based on inherent stress method.As a result of these investigations and analyses, it is clear that welding sequence has a considerable influence on residual stress distribution and that fatigue strength can be enhanced considerably by changing of welding sequence.

特集 ＭＣＭ／ＬＳＩ実装技術 ＭＣＭ／ＬＳＩ実装用プリント配線板製造プロセス ビルドアップ法プリント配線板

特集 ＭＣＭ／ＬＳＩ実装技術 ＭＣＭ／ＬＳＩ実装用プリント配線板製造プロセス ビルドアップ法プリント配線板

Structure and properties of layers built up by CO2 laser radiation

1. The structure and properties of powder build-up depend on the ratio of the melting points of the substrate and the material for build-up, its chemical composition, and they can be varied by changing the build-up regimes and the particle size of the powder. 2. Build-up with powder materials makes it possible to increase the wear resistance and the corrosion resistance of Fe−C alloys without impairing the contact fatigue limit and the endurance limit of the material. 3. Powder build-up by laser makes it possible to combine the materials for build-up so as to obtain a layer with specified structure and properties.