Layer Layout Research Articles

LLDPE-based mono- and multilayer blown films: Property enhancement through coextrusion

In this study we investigated the performance of multilayer coextruded linear low-density polyethylene (LLDPE) blown films. Five-layer films were compared with monolayer dry-blended films, and the effects of layer composition and layout on the end-use properties of the coextruded films were highlighted. Three different LLDPEs were used: a conventional Ziegler-Natta LLDPE gas phase butene copolymer, an advanced Ziegler-Natta LLDPE solution octene copolymer, and a single-site LLDPE solution octene copolymer. Numerous five-layer coextruded structures comprising the single-site resin and the other two Ziegler-Natta resins were produced. The coextruded structures composed of the LLDPE butene and the single-site resin yielded improved end-use properties relative to the monolayer-blended films. This result was ascribed to the presence of interfacial transcrystalline layers. Also, blends of the single-site LLDPE and the advanced Ziegler-Natta LLDPE octene resins within selected layers of coextruded films showed slightly enhanced tear resistance. Finally, it was found that haze was significantly reduced when the outside layers were composed of the single-site resin. POLYM. ENG. SCI., 45:1222–1230, 2005. © 2005 Society of Plastics Engineers

Electrical characterization of the copper cmp process and derivation of metal layout rules

Design rules were developed for the layout of copper Damascene interconnect layers to minimize the within-die resistance variation. The impact of various layout configurations on the metal sheet resistance was characterized using two different test vehicles. An increase in resistance was observed on wide lines and high pattern densities due to dishing and dielectric erosion, respectively. In addition to the above, narrow lines were severely impacted by the presence of wide adjacent features in close proximity. The pattern interaction distance for copper chemical-mechanical planarization (CMP) was calculated by analyzing the resistance variation at the edge of a density or width transition. In this work, the interaction distance was found to be on the order of 25 /spl mu/m (as opposed to a few millimeters for oxide CMP). From these results, a window of about 50 to 60 /spl mu/m was found to be necessary to obtain the effective pattern density for copper CMP. The resistance of the upper metal level was a strong function of the underlying layer density. Hence, multilevel pattern dependencies have to be considered when modeling and predicting the line resistance on a real design. However, unlike oxide polish, pattern density alone is insufficient to predict the final copper thickness. Width-dependent spacing rules are necessary to prevent clustering of features (narrow lines very close to wide buses) and avoid regions of very low density.

Polymer microlayer structures with anisotropic conductivity

Continuous layer-multiplying coextrusion offers a new approach for processing metal-filled polymers into conducting structures. In this process, filled and unfilled polymers are combined into unique structures with many alternating layers of two or more components. The total number of layers can range from tens to thousands. The ability of microlayering to “organize” anisotropic particles was used to obtain metal-filled polypropylene tape with highly anisotropic electrical properties. Orientation of metal flakes by microlayering increased the anisotropy in resistivity by two orders of magnitude over compression molding. Isolation of individual filled layers by alternating filled and unfilled layers resulted in materials with many independent conducting pathways. Filled layers with 10% (v/v) copper flakes or 15% (v/v) nickel flakes were conductive only if the filled layers were thick compared to the thickness of the flake particles. When the thickness of the filled layers approached the particle thickness, the conductive properties were lost. This behavior was understood by comparing the three-dimensional arrangement of flakes in thick conductive layers with the two-dimensional particle layout of thin non-conductive layers.

Simulating Performance of GRS-RW by Finite-Element Procedure

This paper outlines the finite-element (FE) procedure for simulating the performance of geosynthetic-reinforced soil retaining walls (GRS-RWs). Analyses were performed using a modified version of CANDE Code, in which the material properties of the wall (backfill, foundation, geosynthetic, and wall face) were expressed using nonlinear elastic models. The analytical procedure was validated against the loading test results of a full-scale model comprising silty clay backfill soil and a permeable geotextile. A series of parametric studies was conducted to identify the effects of the geosynthetic length and the facing and geosynthetic stiffness on the performance. The layout of geosynthetic layers affects greatly the performance according to the point of the load application. Increased wall facing and geosynthetic stiffness improve the performance by restraining the lateral deformations. Deformation limits at the service conditions can be suggested as an alternative criterion for designing important GRS-RW with the aid of the FE procedure.

A systematic approach for the three-dimensional palletization problem

Abstract We discuss the factors influencing palletization. A heuristic has been developed to cope with the three-dimensional palletization problem in which boxes have different base dimensions and can be grouped by same height. The layered-pallet-loading technique has been applied to the proposed heuristic. Brown's Linear Equation Approach has been modified and incorporated in the proposed heuristic to determine the optimal layout for each layer. Then a stability analysis is conducted to determine the optimum layer order and layout. The application of the proposed heuristic is illustrated by an example.