Analytical and experimental motion analysis of finger follower type cam-valve system with a hydraulic tappet

In this paper, the motion of a finger-follower type cam valve system with a hydraulic tappet was analytically and experimentally studied. First, the exact contact point between cam and follower for each corresponding cam angle was searched by kinematic analysis. Then a 6 degree of freedom lumped spring-damper-mass model was constructed to simulate the valve motion analytically. When constructing the model, most of the parameters were experimentally determined. But several values which are difficult to derive experimentally such as damping coefficients were determined with engineering intuition. In order to show the effectiveness of the analytical model, the predicted cam-valve motion was directly compared with the measured valve and tappet motions.     

Reliability improvement by the suppression of keyhole generation in W-plug vias

This paper describes a mechanism of failures in W-plug vias due to the keyhole generation, and presents the process conditions which enhance the reliability of W-plug vias. For a high aspect ratio via-hole, one of the limiting factors in the reliability of the W-plug is the generation of the keyholes. We have investigated the sensitivities of corresponding technologies and conditions to the generation of the keyholes during the plug process. They include deposition technologies of TiN and deposition conditions of W. Based on the SEM observation and the electromigration failure test, the process conditions of TiN and W have been optimized.     

An enhanced channel-quality indication (CQI) reporting scheme for HSDPA systems

A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.     

Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

A comparison of LII analysis results from numerical model and experiment at elevated surrounding pressures

With environmental concerns over emitted particulate matters(PM) from combustion systems, various researches have been conducted on reduction and measurement techniques of particulate matters. The LII analysis results from numerical models and experiments in an ethylene/air laminar diffusion flame at elevated pressure up to 2.0 MPa with laser fluence 0.07 J/cm², detection wavelength 400 nm were compared to validate a modified LII numerical model. The lifetime of the LII signal decreased as the elevated pressure increased, so that LII decay time also decreased in both results. In the aspect of heat transfer mechanism, it becomes earlier that dominant conduction starts. This shows that the results matched well under the pressure conditions. It is concluded that the LII numerical model could be applied to decide particle size in TIRE-LII at the high-pressure condition.     

Origin of bistability in polyfluorene-based organic bistable devices

This study examined the origin of bistability in polyfluorene (PFO)-based organic bistable memory devices (OBDs) by changing the bulk properties of PFO and metal electrodes. Two different PFOs with and without internal trap sites and two Al and Au electrodes were used. Bistability was induced in all devices when Al was deposited on PFO. On the other hand, bistable switching was observed only in the PFO device with internal trap sites when Au was deposited on PFO. Therefore, both the formation of internal trap sites and an organic–metal interface are essential for bistability in PFO-based OBDs.     

Analysis of the reservoir effect on electromigration reliability

The reservoir effect on electromigration reliability is analyzed using the normalized vacancy concentration distribution in the reservoir region of multi-level Al–0.5%Cu interconnect structure. With the assumption of steady state for the vacancy concentration and the fact that no current flow conducts in the reservoir region during electromigration test, a simple equation for calculation of the vacancy concentration is induced. Then direct calculation of the equation is carried out utilizing the hydrostatic stress distribution computed from finite element method to estimate the probability of initial void formation in the reservoir region. Finally, three multi-level Al–0.5%Cu interconnect structures with different reservoir lengths are constructed and electromigration lifetime for the structures is measured to clarify these computational results. From the results of this study, we conclude that the normalized vacancy concentration under the assumption of steady state can be regarded as a quantitative parameter to analyze the reservoir effect on electromigration reliability.     

Influence of interfacial reaction layer on reliability of chip-scale package joint from using Sn-37Pb and Sn-8Zn-3Bi solder

The microstructure of Sn-37Pb and Sn-8Zn-3Bi solders and the full strength of these solders with an Au/Ni/Cu pad under isothermal aging conditions were investigated. The full strengths tended to decrease as the aging temperature and time increased, regardless of the properties of the solders. The Sn-8Zn-3Bi had higher full strength than Sn-37Pb. In the Sn-37Pb solder, Ni₃Sn₄ compounds and irregular-shaped Pb-rich phase were embedded in a β-Sn matrix. The Ni₃Sn₄ compounds were observed at the interface between the solder and pad. The microstructure of the as-reflowed Sn-8Zn-3Bi solder mainly consists of the β-Sn matrix scattered with Zn-rich phase. Zinc first reacted with Au and then was transformed to the AuZn compound. With aging, Ni₅Zn₂₁ compounds were formed at the Ni layer. Finally, a Ni₅Zn₂₁ phase, divided into three layers, was formed with column-shaped grains, and the thicknesses of the layers were changed.     

Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.