Добірка наукової літератури з теми "Multi-layered Stack Assemblies"

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

The main aim of this paper is to provide the feasibility of non-destructive testing (NDT) method, such as scanning acoustic microscopy (SAM), for damage detection in ultrasound (US) probes for medical imaging during the manufacturing process. In a highly competitive and demanding electronics and biomedical market, reliable non-destructive methods for quality control and failure analysis of electronic components within multi-layered structures are strongly required. Any robust non-destructive method should be capable of dealing with the complexity of miniaturized assemblies, such as the acoustic stack of ultrasonic transducers. In this work, the application of SAM in an industrial scenario was studied for 24 samples of a phased array probe, in order to investigate potential internal integrity, to detect damages, and to assess the compliance of high-demanding quality requirements. Delamination, non-homogeneous layers with micron-thickness, and entrapped air bubbles (blisters) in the bulk of US probe acoustic stacks were detected and studied. Analysis of 2D images and defects visualization by means of ultrasound-based NDT method were compared with electroacoustic characterization (also following as pulse-echo test) of the US probe through an ad-hoc measurement system. SAM becomes very useful for defect detection in multilayered structures with a thickness of some microns by assuring low time-consuming (a limit for other NDT techniques) and quantitative analyses based on measurements. The study provides a tangible contribution and identifies an advantage for manufacturers of ultrasound probes that are oriented toward continuous improvement devoted to the process capability, product quality, and in-process inspection.

Recent advances in the manipulation and control of layered, two-dimensional materials has given way to the construction of heterostructures with new functionality and unprecedented electronic properties. In this study, we present a simple technique to assemble and transfer van der Waals heterostructures using common nail polish. Commercially available nail polish acts as a resilient sticky polymer, allowing for the fabrication of complex multi-material stacks without noticeable fatigue. Directly comparing four commercially available brands of nail polish, we find that one stands out in terms of stability and stacking characteristics. Using this method, we fabricate two top-gated devices and report their electrical properties. Our technique reduces the complexity in assembling van der Waals heterostructures based on the proven van der Waals pick up method.

ABSTRACTThe metal nanocrystal (NC) based carbon nanotube (CNT) memory device has been probed with tunneling rate measurements. Firstly, tunneling behavior at two temperatures (300K and 10K) is reported here to demonstrate the distinct charge tunneling behavior for traps versus NCs and understand their relative contributions to program operations. Low temperature measurements show clear differentiation for two regimes of quantum transport. The FN tunneling regime exhibits strong bias dependence and dominates at high electric fields producing larger tunneling rates than the direct tunneling regime. In comparison to traps, the metal NCs repel potential contours and hence produce higher electric fields that enhance tunneling. The FN tunneling diminishes when the charging of the nanocrystal or traps decreases (relaxes) the electric field in the tunnel dielectric (TD) enough for the low field direct tunneling to dominate. The direct tunneling occurs at low fields, and is less sensitive to electric fields. The NCs demonstrate faster tunneling which can be ascribed to their large tunneling cross-section compared to traps. This is despite the relative proximity of traps to the channel in our structure. Secondly, the tunneling rates for two different TDs of similar EOT (under linear approximation) have been characterized and compared. They are a homogenous evaporated SiO2 and layered dielectric consisting of an evaporated SiO2 and ALD Al2O3 stack. While the evaporated SiO2 based TD demonstrates the distinct NC versus trap tunnel rate performance, the layered TD demonstrates stronger resistance to tunneling to the NCs. This result is consistent with the low tunneling rates demonstrated in Al2O3 elsewhere. Finally, the program performance of the NC-CNT memory device is evaluated as 0.5 V threshold voltage (VT) shift for a charging pulse of 9V and 100 μs. Combining with previous results, this indicates that NC-CNT memory is a promising candidate for low voltage, fast, multi-level cell (MLC) operation with sub-lithographic (self-assembled) features for sub 30 nm FLASH memory node. From the device physics perspective, these measurements may serve as the calibration and validation for advanced tunneling calculations and device modeling for promising nanoscale charge-based non-volatile memories.

Background information Sandscript was programmed with the web application « Tchat-scene », created by Carol-Ann Braun and the computer services company Timsoft (). It organizes a data-base of raw material into compositions and sequences allowing to build larger episodes. Multimedia resources are thus attributed to frames surrounding the chat space or to the chat space itself, thus “augmented” to include pre-written texts and graphics. Sandscript works best on a PC, with Internet Explorer. On Mac, use 0S9 and Internet Explorer. You will have to download a chat application for the site to function. Coded conversation General opinion would have it that chat space is a conversational space, facilitating rather than complicating communication. Writing in a chat space is very much influenced by the current ideological stance which sees collaborative spaces as places to make friends, speak freely, flip from one “channel” to another, link with a simple click into related themes, etc. Moreover, chat users tend to think of the chat screen in terms of a white page, an essentially neutral environment. A quick analysis of chat practices reveals a different scenario: chat spaces are highly coded typographical writing spaces, quick to exclude those who don’t abide by the technical and procedural constraints associated with computer reading/writing tools (Despret-Lonné, Gentès). Chatters seek to belong to a “community;” conversely, every chat has “codes” which restrict its membership to the like-minded. The patterns of exchange characteristic of chats are phatic (Jakobson), and their primary purpose is to get and maintain a social link. It is no surprise then that chatters should emphasize two skills: one related to rhetorical ingenuity, the other to dexterity and speed of writing. To belong, one first has to grasp the banter, then manage very quickly the rules and rituals of the group, then answer by mastering the intricacies of the keyboard and its shortcuts. Speed is compulsory if your answers are to follow the communal chat; as a result, sentences tend to be very short, truncated bits, dispatched in a continuous flow. Sandscript attempts to play with the limits of this often hermetic writing process (and the underlying questions of affinity, participation and reciprocity). It opens up a social space to an artistic and fictional space, each with rules of its own. Hyper-linked dialogue Sandscript is not just about people chatting, it is also about influencing the course of these exchanges. The site weaves pre-scripted poetic content into the spontaneous, real-time dialogue of chatters. Smileys and the plethora of abbreviations, punctuations and icons characteristic of chat rooms are mixed in with typographical games that develop the idea of text as image and text as sound — using Morse Code to make text resonate, CB code to evoke its spoken use, and graphic elements within the chat space itself to oppose keyboard text and handwritten graffiti. The web site encourages chatters to broaden the scope of their “net-speak,” and take a playfully conscious stance towards their own familiar practices. Actually, most of the writing in this web-site is buried in the database. Two hundred or so “key words” — expressions typical of phatic exchanges, in addition to other words linked to the idea of sandstorms and archeology — lie dormant, inactive and unseen until a chatter inadvertently types one in. These keywords bridge the gap between spontaneous exchange and multimedia content: if someone types in “hi,” an image of a face, half buried in sand, pops up in a floating window and welcomes you, silently; if someone types in the word “wind,” a typewritten “wind” floats out into the graphic environment and oscillates between the left and right edges of the frames; typing the word “no” “magically” triggers the intervention of an anarchist who says something provocative*. *Sandscript works like a game of ping-pong among chatters who are intermittently surprised by a comment “out of nowhere.” The chat space, augmented by a database, forms an ever-evolving, fluid “back-bone” around which artistic content is articulated. Present in the form of programs who participate in their stead, artists share the spot light, adding another level of mediation to a collective writing process. Individual and collective identities Not only does Sandscript accentuate the multimedia aspects of typed chat dialogues, it also seeks to give a “ shape” to the community of assembled chatters. This shape is musical: along with typing in a nickname of her choice, each chatter is attributed a sound. Like crickets in a field, each sound adds to the next to create a collective presence, modified with every new arrival and departure. For example, if your nick is “yoyo-mama,” your presence will be associated with a low, electronic purr. When “pillX” shows up, his nick will be associated with a sharp violin chord. When “mojo” pitches in, she adds her sound profile to the lot, and the overall environment changes again. Chatters can’t hear the clatter of each other’s keyboards, but they hear the different rhythms of their musical identities. The repeated pings of people present in the same “scape” reinforce the idea of community in a world where everything typed is swept away by the next bit of text, soon to be pushed off-screen in turn. The nature of this orchestrated collective presence is determined by the artists and their programs, not by the chatters themselves, whose freedom is limited to switching from one nick to another to test the various sounds associated with each. Here, identity is both given and built, both individual and collective, both a matter of choice and pre-defined rules. (Goffman) Real or fictitious characters The authors introduce simulated bits of dialogue within the flow of written conversation. Some of these fake dialogues simply echo whatever keywords chatters might type. Others, however, point else where, suggesting a hyper-link to a more elaborate fictionalized drama among “characters.” Sandscript also hides a plot. Once chatters realize that there are strange goings on in their midst, they become caught in the shifting sands of this web site’s inherent duality. They can completely lose their footing: not only do they have to position themselves in relation to other, real people (however disguised…) but they also have to find their bearings in the midst of a database of fake interlocutors. Not only are they expected to “write” in order to belong, they are also expected to unearth content in order to be “in the know.” A hybridized writing is required to maintain this ambivalence in place. Sandscript’s fake dialogue straddles two worlds: it melds in with the real-time small talk of chatters all while pointing to elements in a fictional narrative. For example, “mojo” will say: “silting up here ”, and “zano” will answer “10-4, what now? ” These two characters could be banal chatters, inviting others to join in their sarcastic banter… But they are also specifically referring to incidents in their fictional world. The “chat code” not only addresses its audience, it implies that something else is going on that merits a “click” or a question. “Clicking” at this juncture means more than just quickly responding to what another chatter might have typed. It implies stopping the banter and delving into the details of a character developed at greater length elsewhere. Indeed, in Sandscript, each fictional dialogue is linked to a blog that reinforces each character’s personality traits and provides insights into the web-site’s wind-swept, self-erasing world. Interestingly enough, Sandscript then reverses this movement towards a closed fictional space by having each character not only write about himself, but relate her immediate preoccupations to the larger world. Each blog entry mentions a character’s favorite URL at that particular moment. One character might evoke a web site about romantic poetry, another one on anarchist political theory, a third a web-site on Morse code, etc… Chatters click on the URL and open up an entirely new web-site, directly related to the questions being discussed in Sandscript. Thus, each character represents himself as well as a point of view on the larger world of the web. Fiction opens onto a “real” slice of cyber-space and the work of other authors and programmers. Sandscript mixes up different types of on-line identities, emphasizing that representations of people on the web are neither “true” nor “false.” They are simply artificial and staged, simple facets of identities which shift in style and rhetoric depending on the platform available to them. Again, identity is both closed by our social integration and opened to singular “play.” Conclusion: looking at and looking through One could argue that since the futurists staged their “electrical theater” in the streets of Turin close to a hundred years ago, artists have worked on the blurry edge between recognizable formal structures and their dissolution into life itself. And after a century of avant-gardes, self-referential appropriations of mass media are also second nature. Juxtaposing one “use” along another reveals how different frames of reference include or exclude each other in unexpected ways. For the past twenty years much artwork has which fallen in between genres, and most recently in the realm of what Nicolas Bourriaud calls “relational aesthetics.” Such work is designed not only to draw attention to itself but also to the spectator’s relation to it and the broader artistic context which infuses the work with additional meaning. By having dialogue serve as a hyper-link to multimedia content, Sandscript, however, does more. Even though some changes in the web site are pre-programmed to occur automatically, not much happens without the chatters, who occupy center-stage and trigger the appearance of a latent content. Chatters are the driving force, they are the ones who make text appear and flow off-screen, who explore links, who exchange information, and who decide what pops up and doesn’t. Here, the art “object” reveals its different facets around a multi-layered, on-going conversation, subjected to the “flux” of an un-formulated present. Secondly, Sandscript demands that we constantly vary our posture towards the work: getting involved in conversation to look through the device, all while taking some distance to consider the object and look at its content and artistic “mediations.” (Bolster and Grusin, Manovitch). This tension is at the heart of Sandscript, which insists on being both a communication device “transparent” to its user, and an artistic device that imposes an opaque and reflexive quality. The former is supposed to disappear behind its task; the latter attracts the viewer’s attention over and over again, ever open to new interpretations. This approach is not without pitfalls. One Sandscript chatter wondered if as the authors of the web-site were not disappointed when conversation took the upper hand, and chatters ignored the graphics. On the other hand, the web site’s explicit status as a chat space was quickly compromised when users stopped being interested in each other and turned to explore the different layers hidden within the interface. In the end, Sandscript chatters are not bound to any single one of these modes. They can experience one and then other, and —why not —both simultaneously. This hybrid posture brings to mind Herman’s metaphor of a door that cannot be closed entirely: “la porte joue” —the door “gives.” It is not perfectly fitted and closed — there is room for “play.” Such openness requires that the artistic device provide two seemingly contradictory ways of relating to it: a desire to communicate seamlessly all while being fascinated by every seam in the representational space projected on-screen. Sandscript is supposed to “run” and “not run” at the same time; it exemplifies the technico-semiotic logic of speed and resists it full stop. Here, openness is not ontological; it is experiential, shifting. About the Authors Carol-Ann Braun is multimedia artist, at the Ecole Nationale Superieure des Telecomunications, Paris, France. EmaiL: carol-ann.braun@wanadoo.fr Annie Gentes is media theorist and professor at the Ecole Nationale Superieure des Telecomunications, Paris, France. Email: Annie.Gentes@enst.fr Works Cited Adamowicz, Elza. Surrealist Collage in Text and Image, Dissecting the Exquisite Corpse. Cambridge: Cambridge University Press, 1998. Augé, Marc. Non-lieux, Introduction à une Anthropologie de la Surmodernité. Paris: Seuil, 1992. Bolter, Jay David and Richard Grusin. Remediation, Understanding New Media. Cambridge: MIT Press, 2000. Bourriaud, Nicholas. Esthétique Relationnelle. Paris: Les Presses du Réel, 1998. Despret-Lonnet, Marie and Annie Gentes, Lire, Ecrire, Réécrire. Paris: Bibliothèque Centre Pompidou, 2003. Goffman, Irving. Interaction Ritual. New York: Pantheon, 1967. Habermas, Jürgen. Théorie de l’Agir Communicationnel, Vol.1. Paris: Fayard, 1987. Herman, Jacques. “Jeux et Rationalité.” Encyclopedia Universalis, 1997. Jakobson, Roman.“Linguistics and Poetics: Closing statements,” in Thomas Sebeok. Style in Language. Cambridge: MIT Press, 1960. Latzko-Toth, Guillaume. “L’Internet Relay Chat, Un Cas Exemplaire de Dispositif Socio-technique,” in Composite. Montreal: Université du Québec à Montréal, 2001. Lyotard, Jean-François. La Condition Post-Moderne. Paris: les Editions de Minuit, 1979. Manovitch, Lev. The Language of New Media. Cambridge: MIT Press, 2001. Michaud, Yves. L’Art à l’Etat Gazeux. Essai sur le Triomphe de l’Esthétique, Les essais. Paris: Stock, 2003. Citation reference for this article MLA Style Braun, Carol-Ann & Gentes, Annie. "Dialogue: a hyper-link to multimedia content." M/C: A Journal of Media and Culture <http://www.media-culture.org.au/0406/05_Braun-Gentes.php>. APA Style Braun, C. & Gentes, A. (2004, Jul1). Dialogue: a hyper-link to multimedia content.. M/C: A Journal of Media and Culture, 7, <http://www.media-culture.org.au/0406/05_Braun-Gentes.php>

Large-scale integration at lower cost has led to the usage of multi-layered organic substrates in flip-chip assemblies. However, the warpage of substrate plays an important role in the reliability of back-end-of-line (BEOL) stack on a chip. In this work, we study the effect of substrate layer configuration, and thus the warpage of the substrate at reflow temperature on BEOL reliability. A plane-strain flip-chip on substrate assembly model is utilized to study the die and solder stresses for different substrate layer configurations. Apart from studying the die stresses, fracture mechanics based approach is used to study the effect of substrate configuration on energy available for a crack present in back-end-of-line (BEOL) stack. In this paper, we describe the methodology to model the substrate with initial warpage at reflow temperature, characterize the effect of the initial warpage at reflow temperature on die stresses at room temperature and further use fracture mechanics based approach to predict the change in risk for a crack present in BEOL stack for different substrate warpage configurations at reflow temperature.

Appropriate consideration of tolerances is critical to the design and manufacture of products that meet customer requirements and defined cost targets. Tolerance analysis is most commonly conducted at the individual part or sub-assembly level utilizing basic stack-up methods (worst-case analysis) to ensure the producibility of the assembled product. A worst-case analysis assumes that each dimension in the stack-up will be manufactured on the extreme end or limit of its assigned tolerance (max or min) in such a way that all tolerances become additive. This usually results in tighter than required drawing tolerances being assigned to guarantee the product can be assembled. Modern day manufacturing processes focus on targeting the nominal dimensional value, so it is safe to assume that a higher number of parts will be produced closer to the nominal value than parts produced at the extreme end of the tolerance range. When evaluating the tolerance stack-up of a larger assembly with many parts additional tolerance analysis methods apply (Root Sum Squared, RSS), and a worst-case analysis becomes more costly and less meaningful. The RSS method of tolerance analysis takes into consideration manufacturing targets and applies normal distribution methods to assess more likely tolerance results, allowing relaxed drawing tolerances to be assigned while still maintaining a high level of confidence in a successful assembly. For analysis of complex systems or installations, tolerance studies using more sophisticated approaches to deal with variation such as Monte Carlo statistical analysis is required. Variational Tolerance Analysis (VTA) tools available today allow a typical Monte Carlo tolerance simulation to be visualized by the designer through 3-dimensional real time manufacturing simulations and sensitivity analysis. This in turn simplifies the development process and allows better identification of tolerance drivers within a large system installation; analysis of the geometric effect of tolerances within the installation; and the ability to quickly iterate the analysis to optimize designs for producibility and lower cost. In this paper, the use of VTA is assessed and quantified to form a business case for further investment by Lockheed Martin. In the course of this work, VTA has been evaluated both before and after final designs were released to manufacturing. Before final designs are released VTA can be used for design optimization (i.e. build before you build simulations), part sequencing studies, or to gain insight into the assembly/installation process enabling advanced planning to take place up front. VTA can also address challenges discovered after final designs have been released to manufacturing and parts are on hand (i.e. during the build) such as: assembly issues, out of spec part disposition, and to inform manufacturing of any special tooling or part rework considerations aiding in corrective action or risk mitigation plans. Cost savings to the business due to the implementation of VTA has been demonstrated in 4 distinct ways: 1.Reduced design revisions – Design optimization up front reduces future revisions caused by producibility and tolerance related discoveries. 2.Manufacturing – Through tolerance optimization, nonimpactful tolerances can be relaxed while still ensuring a successful assembly. 3.Reduced build schedule – Increased assembly awareness and advanced planning allows a streamlined production process with risk mitigation strategies in place. 4.Reduced scrap, rework, repair (SRR) – Engineering labor to disposition out of spec parts is reduced by entering as-measured tolerances into the simulation model to assess the overall impact to installation success. The conclusion is VTA simulations provide measurable benefits to the business through robust design optimization, and multi-layered cost and risk reductions.