Improved Burn-In Stress Methodology for Stress Uniformity

2018 ◽  
Author(s):  
Jungsuk Ko ◽  
Hoonchang yang ◽  
Hyungchae Jeon ◽  
Gyuyoung Nam ◽  
Youngseok Ryu ◽  
...  
Keyword(s):  
Temperature Stress ◽  
Stress Condition ◽  
Temperature Deviation ◽  
Stress Effects ◽  
Hot Temperature ◽  
Production Environments ◽  
Stress Environment ◽  
The Stability ◽  
Stress Uniformity ◽  
Stress Voltage

Abstract The necessity of hot temperature stress is widely recognized as the initial stress methodology to maintain the stability of products from infant defects in device [1, 2]. However, hot temperature stress has a disadvantage in terms of stress uniformity because temperature variation according to stress environment such as chamber, board, and tester accelerates different stress effects per chips. In addition, this stress condition can cause serious reliability problem in the mass production environments. Therefore, the stress temperature should be lowered to minimize the temperature deviation due to the production environments. The reduction of stress temperature cause the lack of stress amount, so optimized stress voltage and time to maintain the stress condition is required. In this study, various stress voltage and time with decreasing temperature were evaluated in consideration of lifetime that unit elements such transistors and capacitors did not degrade by any stress conditions. In addition, it was confirmed that stress uniformity can be improved in the stress condition obtained by the evaluation. Furthermore, the enhanced initial failure screen ability was proven with mass evaluations.

Bias-Temperature-Stress Response of Commercially-Available SiC Power MOSFETs

2015 ◽  
Vol 821-823 ◽  
pp. 677-680 ◽  
Author(s):  
Ronald Green ◽  
Aivars J. Lelis ◽  
Mooro El ◽  
Daniel B. Habersat
Keyword(s):  
Stress Response ◽  
Temperature Stress ◽  
Threshold Voltage ◽  
Stress Condition ◽  
Negative Bias ◽  
Gate Bias ◽  
Strong Function ◽  
Power Mosfets ◽  
Bias Temperature Stress ◽  
The Stability

The stability of the threshold voltage of commercial SiC MOSFETs from two device manufactures has been evaluated and compared when subject to positive and negative bias-temperature-stress conditions. For both device groupings, the worse-case stress occurred under negative bias temperature conditions with VGS = –15 V and a stress temperature of 200 °C. Devices in the Vendor A grouping exhibited acceleration in their bias-temperature-stress response that occurred earlier in time as a strong function of stress-temperature and to a lesser degree on gate-bias magnitude. Devices in the Vendor B grouping showed some evidence of acceleration, but only for the worse-case stress condition. Threshold voltage shifts for this device group were very low and extremely stable, with recorded values below 0.4 V for most conditions.

Stability Prediction of Surrounding Rocks and Optimum Design of Roof-Bolt Parameters in Deep Roadway

2013 ◽  
Vol 353-356 ◽  
pp. 436-439
Author(s):  
De Sen Kong ◽  
Yong Po Chen
Keyword(s):  
Prediction Method ◽  
Simulation Method ◽  
Complex Stress ◽  
Roof Bolt ◽  
Deformation And Failure ◽  
Long Run ◽  
Research Findings ◽  
Stress Environment ◽  
Classification Prediction ◽  
The Stability

In order to forecast the stability of deep roadway and optimize the parameters of bolts, the complex stress environment and the multivariate surrounding rocks characteristics of deep roadway were analyzed. Then the classification prediction method and the numerical simulation method were simultaneously used to analysis the stability of surrounding rocks. Furthermore, the supporting parameters of bolts were also designed optimally. It was shown that the characteristics of stress distribution, deformation and failure zone of surrounding rocks are not ideal. So it is necessary to optimize the supporting parameters of deep roadway. All these research findings will provide the theory basis for bolts of deep roadway and will ensure the optimization of bolts and the stability of deep roadway in the long run.

Stability of Viscoelastic Channel Flow

2007 ◽  
Author(s):  
Nariman Ashrafi
Keyword(s):  
Reynolds Number ◽  
Viscosity Ratio ◽  
Weissenberg Number ◽  
Base Flow ◽  
Galerkin Projection ◽  
Large Reynolds Number ◽  
One Dimensional ◽  
Stress Effects ◽  
The Stability ◽  
The One

The nonlinear stability and bifurcation of the one-dimensional channel (Poiseuille) flow is examined for a Johnson-Segalman fluid. The velocity and stress are represented by orthonormal functions in the transverse direction to the flow. The flow field is obtained from the conservation and constitutive equations using the Galerkin projection method. Both inertia and normal stress effects are included. The stability picture is dramatically influenced by the viscosity ratio. The range of shear rate or Weissenberg number for which the base flow is unstable increases from zero as the fluid deviates from the Newtonian limit as decreases. Typically, two turning points are observed near the critical Weissenberg numbers. The transient response is heavily influenced by the level of inertia. It is found that the flow responds oscillatorily. When the Reynolds number is small, and monotonically at large Reynolds number when elastic effects are dominated by inertia.

P-6.1: Asymmetric Effects of Gate-Bias Stress Voltage on the Stability under Positive and Negative Gate-Bias Stress of a-IGZO TFTs

2018 ◽  
Vol 49 ◽  
pp. 597-600
Author(s):  
Xiaoliang Zhou ◽  
Xiaodong Zhang ◽  
Yang Shao ◽  
Letao Zhang ◽  
Hongyu He ◽  
...  
Keyword(s):  
Gate Bias ◽  
Asymmetric Effects ◽  
Bias Stress ◽  
The Stability ◽  
Stress Voltage ◽  
Gate Bias Stress

scholarly journals Stabilization Mechanism and Safety Control Strategy of the Deep Roadway with Complex Stress

2020 ◽  
Vol 2020 ◽  
pp. 1-18 ◽  
Author(s):  
Yang Yu ◽  
Dingchao Chen ◽  
Xiangqian Zhao ◽  
Xiangyu Wang ◽  
Lianying Zhang ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Control Strategies ◽  
Pressure Coefficient ◽  
Horizontal Stress ◽  
Complex Stress ◽  
Rock Stratum ◽  
Safety Control ◽  
Coal Resources ◽  
Stress Environment ◽  
The Stability

With the increase of mining intensity of coal resources, some coal mines in China have gradually entered the deep mining stage. The complexity of the stress environment of the deep rock stratum leads to the difficulty of coal mining. Among them, the control of the deep roadway is one of the bottlenecks restricting the safety mining of the deep coal resources in China. By means of statistical analysis, the factors affecting the stability of the deep roadway were summed up: roadway occurrence environment, driving disturbance, and support means. The mechanical model of the deep roadway was established with the theory of elastic-plastic mechanics, the distribution characteristics of the plastic zone of the roadway were revealed, and the influence laws of lateral pressure coefficient, vertical stress, and support strength on the stability of the roadway were analyzed. Through numerical simulation, the law of stress, displacement and the plastic zone distribution evolution of the deep roadway, the mechanism of horizontal stress, and the mechanism of bolt support on the roadway were studied. On this basis, the safety control strategies to ensure the stability of the deep roadway were put forward: improving the strength of the roof and floor, especially the bearing part of the top angle and the side angle, enhancing the stability of the two sides of the roadway and controlling the floor heave, and making the surrounding rock of the deep roadway release pressure moderately, so as to make the roadway easy to be maintained under the low stress environment. These meaningful references were provided for the exploitation of deep coal resources in China.

High temperature stress effects on pollens of rice (Oryza sativa L.) genotypes

2014 ◽  
Vol 101 ◽  
pp. 36-46 ◽  
Author(s):  
S. Das ◽  
P. Krishnan ◽  
Monalisa Nayak ◽  
B. Ramakrishnan
Keyword(s):  
Oryza Sativa ◽  
High Temperature ◽  
Temperature Stress ◽  
Oryza Sativa L ◽  
High Temperature Stress ◽  
Stress Effects

A New Method for Predicting the Critical Taylor Number in Rotating Cylindrical Flows

1987 ◽  
Vol 54 (3) ◽  
pp. 713-719 ◽  
Author(s):  
J. O. Cruickshank
Keyword(s):  
Dynamic Stability ◽  
Critical Stress ◽  
Stress Condition ◽  
Flow Instability ◽  
Fluid System ◽  
Fluid Systems ◽  
Concentric Cylinders ◽  
Elastic Systems ◽  
Subsequent Motion ◽  
The Stability

A method for determining the boundaries of dynamic stability of a fluid system, as distinct from the prediction of the subsequent motion, is presented. The method is based on well-known approaches to the problem of instability in elastic systems. The extension of these methods to fluid systems, specifically, to the stability of flow between concentric cylinders, confirms that it may be possible in some cases to determine the boundaries of stability of fluid systems without recourse to an Orr-Sommerfeld type treatment. The results also suggest that the concept of apparent (virtual) viscosity may have implications for fluid stability outside the current realm of turbulence modelling. Finally, it is also shown that flow instability may be preceded by the onset of a critical stress condition in analogy with elastic systems.

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