Development of Stretch Solder Interconnections for Wafer Level Packaging

A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps.     

Disaster recovery planning in an automated manufacturingenvironment

Disasters may strike at any moment in any location. When they do, no distinction is made about the type of firm that is being affected, whether it is a bank or a manufacturing plant. Most firms do not plan for possible disasters, and those that do have typically focused on computer and data contingency planning. In this paper, the focus is shifted to incorporate disaster recovery planning for manufacturing enterprises, especially those that are automated. Automated manufacturing enterprises have characteristics that put them at an increased risk to disasters. The methodological framework proposed in this paper will aid manufacturing organizations and their managers in reducing the risks associated with unanticipated disasters. The framework is termed the “Manufacturing Operations Recovery and Resumption” model. Recommended activities and tools for effective management of this methodology are identified     

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.     

Fabrication and characteristics of tapes and test magnets made from Ag-Clad Bi-2223 superconductors

Pb_0.4Bi_1.8Sr₂Ca_2.2Cu₃O_x (Bi-2223) precursor powder was prepared by a solid-state reaction of carbonates and oxides of lead, bismuth, strontium, calcium, and copper, and the powder was then used to fabricate silver-clad tapes by the powder-in-tube technique. Transport critical current density (J_c) values>4×10⁴ A/cm² at 77K and 2×10⁵ A/cm² at 4.2 and 27K have been achieved in short tape samples. Long lengths of tape were tested by winding them into pancake coils. Recently, we fabricated a test magnet by stacking ten pancake coils, each containing three 16m lengths of rolled tape, and tested it at 4.2, 27 and 77K. A maximum generated field of 2.6 T was measured in zero applied field at 4.2K and the test magnet generated significant self-field in background fields up to 20 T. The results are discussed in this paper.     

Distribution of the lifetime of consecutive k-within-m-out-of-n:F systems

The distribution of the lifetime (MTTF) of any consecutive k -within-m-out-of-n:F system, with independent exponentially distributed component lifetimes, is shown to be a convex combination of the distributions (MTTFs) of several convolutions of independent random variables, where each convolution represents a distinct path in the evolution of the system's history, and where in each convolution all but the last random variable is exponential. The last random variable in each convolution is either a zero lifetime or the lifetime of several disjoint consecutive k_i within m_i-out-of-n:F systems in series with each k_i<k, each m_i<m, and each n_i<n. This enables the calculations to proceed recursively. Calculations are facilitated by the symmetric nature of the convex combination     

DARYN-a distributed decision-making algorithm for railway networks:modeling and simulation

The state of the art in scheduling “point-to-point” trains in a railway network utilizes the principles of centralized decision-making. The major difficulty of this approach is that the execution time and the memory requirements increase nonlinearly as the system grows in size. The present paper introduces a new approach, “DARYN”, wherein the overall decision process is analyzed and distributed onto every natural entity of the system. In DARYN, the decision process for every train is executed by an on-board processor that negotiates, dynamically and progressively, for temporary ownership of the tracks with the respective station controlling the tracks, through explicit processor to processor communication primitives. This processor then computes its own route utilizing the results of its negotiation, its knowledge of the track layout of the entire system, and its evaluation of the cost function. Every station's decision process is also executed by a dedicated processor that, in addition, maintains absolute control over a given set of tracks and participates in the negotiation with the trains. Presently, DARYN utilizes a simple cost function. However, if one chooses to increase the complexity of the cost function, DARYN's advantage over the traditional approach increases due to its enormous available computational power. Given that the current microprocessors such as MC68030, MC88000, Intel 486, and Intel 860 are powerful yet relatively inexpensive, a network of concurrently executing processors may offer superior price-performance quotient over a single high performance computer     

Synthetic,spectroscopic, and structural Studies on Lanthanide Complexes of Diphosphazane Dioxide Ligands

Lanthanide nitrate complexes of diphosphazane dioxides Ph₂P(O)N(Prⁱ)P(O)Ph₂ ( 1 ) and (PhO)₂P(O)N(Me)P(O)(OPh)₂ ( 2 ) have been synthesised and studied by conductometry, IR, multinuclear NMR spectroscopic methods and X-ray diffraction. Ligand 2 is accessible by two different methods, viz., by direct oxidation of the phosp(III)azane ligand or by starting from phosph(V)azane chloro precursor. The structure of 2 is confirmed by X-ray diffraction. Crystallographic data for 2 : Triclinic, Space group P1 , a = 10.078(1), b = 10.575(3), c = 12.364(4) Å, α = 75.70(2)°, α = 75.56(1)°, γ = 77.68(1)°, Z = 2, V = 1 220 ų; structure refined to R_F = 0.0459 on 3 495 data with F > 3σ(F). The diphosphazane dioxide ligand exhibits trans geometry in the solid state. The structure of a lanthanide complex, [Pr(NO₃)₃( 2 )₂] ( 14 ) is also determined by X-ray diffraction. Crystallographic data for 14 : Trigonal, Space group P3₂, a = b = 15.710(2), c = 40.067(2) Å, Z = 6, V = 8 564 ų; structure refined to R_F = 0.0430 on 8 077 data with F > 5σ(F). The two diphosphazane dioxide ligands and the nitrate groups are coordinated to praseodymium in a bidentate chelate fashion. The geometry around the ten coordinated metal is distorted bicapped square antiprism.     

Application of gamma-ray spectrometry for the assay of uranium in crude UF4—An input material used for producing nuclear grade U-metal at the natural uranium conversion plants

A -spectrometric method has been developed for the assay of uranium in crude UF₄, which is used as a secondary source of input material for producing nuclear grade U-metal at natural uranium conversion plants. The method makes use of a NaI (Tl) detector coupled with a multichannel analyzer. The 1 MeV -ray of²³⁸U is used for calibration. A method for the fabrication of uniform -assay calibration standards is also suggested, based on the results of this investigation. The calibration standards were prepared by soaking the matrix in uranium solution and then drying the whole material. The amount of²³⁸U in the crude UF₄ sample was directly estimated by comparing the areas under the 1 MeV -ray peak of known calibration standards with the corresponding areas of the samples to be measured. 100 g each of the standard and the sample were counted. 5 crude UF₄ samples were analyzed by this method. The uranium contents in these samples were found to be in the range of 12.2–28.7 g. To compare the -ray spectrometry results with a completely independent method, chemical analysis by potentiometry of all the samples was also done. The -spectrometric results were found to agree within ±18% with the chemical analysis results.