Ball Grid Array Thermomechanical Response During Reflow Assembly

1996 ◽  
Vol 118 (4) ◽  
pp. 214-222 ◽  
Author(s):  
T. E. Voth ◽  
T. L. Bergman
Keyword(s):  
Process Model ◽  
Experimental Studies ◽  
Ball Grid Array ◽  
Mechanical Processing ◽  
Processing Conditions ◽  
System Behavior ◽  
Reflow Soldering ◽  
Thermomechanical Response ◽  
Model Predictions ◽  
Representative System

The thermomechanical response of ball-grid array assemblies during reflow soldering is considered here. Experiments are performed to investigate the thermomechanical response of a representative system and the results are used to validate a numerical model of system behavior. The conclusions drawn from the experimental studies are used to guide development of a process model capable of describing more realistic BGA soldering scenarios. Process model predictions illustrate the system’s thermomechanical response to thermal and mechanical processing conditions, as well as component properties. High thermal conductivity assemblies show the greatest sensitivity to mechanical loading conditions.

scholarly journals Research of a contact impact of a root crop with a screw auger

2020 ◽  
Vol 66 (No. 1) ◽  
pp. 33-42
Author(s):  
Viktor Baranovsky ◽  
Olena Truchanska ◽  
Maria Pankiv ◽  
Valentina Bandura
Keyword(s):  
Process Model ◽  
Empirical Process ◽  
Experimental Studies ◽  
Kinematic Parameters ◽  
Fodder Beet ◽  
Root Crop ◽  
Cleaning System ◽  
Screw Diameter ◽  
Contact Impact ◽  
Further Development

The purpose of this research is the further development of the methodology and methods of optimising the parameters of root pile  combined cleaners of a root crop harvesting machine. We have conducted theoretical and experimental studies of the combined  cleaning system’s functioning process. By executing the analysis, we found the motion of the fodder beet through the working surfaces of the feeding conveyor and the auger installed above it. We have got an analytical and empirical process model for the fodder beet’s oblique sub-hit on the auger turn. It characterises the dependence of the total rate of the sub-hit coefficient of the technological  interaction of the roots and the depth of the root damage, which depend on the main parameters of the combined cleaning system. We found out the rational limits of the basic structural and kinematic parameters of the combined cleaning system by the provided minimum fodder beet damage. It is theoretically justified that the minimum damage to roots of the beet roots will be at a contact angle of zero (γ ≅ 0) or close to it. This condition is protected with the following combinations of parameters: a screw diameter of D = 0.4, 0.6, 0.8 m and a screw speed of n = 99, 72, 50 rpm, respectively.

Experimental Studies on Attenuation of Rotor-Stator Dynamics: Effects of High-Frequency Inclusion and Annular Fluid

2018 ◽  
Author(s):  
Meryem Kanzari ◽  
Mohammed AlQaradawi ◽  
Balakumar Balachandran
Keyword(s):  
High Frequency ◽  
Complex Dynamics ◽  
Experimental Studies ◽  
Flexible Rotor ◽  
Flexible Rotors ◽  
Speed Modulation ◽  
Model Predictions ◽  
Drive Speed ◽  
The Stability ◽  
Three Degree Of Freedom

Flexible, rotating structures can experience complex dynamics, when torsional and lateral motions are involved. Oilwell drill strings form one example of such structures. In the present study, the authors investigate the influence of sinusoidal drive speed modulation on whirling motions of flexible rotors with contact interactions. For two types of drilling-like operations, one with drill mud and another without drill mud, the stability of motions is studied. A laboratory-scale drill rig is used to study the dynamics of a flexible rotor, which is driven at one end and housed within a stator at the other end. Experimental results are presented and discussed for different drive speeds. The findings suggest that the addition of drill mud in the annular space between the rotor and stator along with high-frequency modulation in the drive input helps attenuate lateral motions. The torsional motions appear to be influenced more by the high-frequency drive speed modulation. A three-degree-of-freedom model has been constructed to study lateraltorsional dynamics of a rotor-stator system. The model predictions are compared with the experimental data. The findings of this work have relevance for constructing practical solutions to control whirl dynamics of flexible rotors such as drill strings.

Validating Structural Metrics for BPEL Process Models

2020 ◽  
Author(s):  
Geoffrey Muchiri Muketha ◽  
Abdul Azim Abd Ghani ◽  
Rodziah Atan 
Keyword(s):  
Business Process ◽  
Process Model ◽  
Experimental Studies ◽  
Process Models ◽  
Business Process Execution Language ◽  
Regression Test ◽  
Correlation Tests ◽  
Business Process Execution ◽  
Structural Metrics ◽  
Model Understandability

Business process models tend to get more and more complex with age, which hurts the ease with which designers can understand and modify them. Few metrics have been proposed to measure this complexity, and even fewer have been tested in the Business Process Execution Language (BPEL) context. In this paper, we present three related experimental studies whose aim was to analyse the ability of four selected structural metrics to predict BPEL process model understandability and modifiability. We used Spearman’s rho and regression analysis in all three experiments. All metrics passed the correlation tests meaning that they can serve as understandability and modifiability indicators. Further, four of the metrics passed the regression test for understanding time implying that they can serve as understandability predictors. Finally, only one metric passed the regression test for modification time implying that it can serve as a modifiability predictor.

Smeared-Property Models for Shock-Impact Reliability of Area-Array Packages

2007 ◽  
Vol 129 (4) ◽  
pp. 373-381 ◽  
Author(s):  
Pradeep Lall ◽  
Dhananjay Panchagade ◽  
Yueli Liu ◽  
Wayne Johnson ◽  
Jeff Suhling
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Printed Circuit Boards ◽  
Ball Grid Array ◽  
Drop Impact ◽  
Transient Dynamics ◽  
Valuable Insight ◽  
Cost Constraints ◽  
Plastic Ball ◽  
Model Predictions

Portable electronics is subjected to extreme accelerations in shock and drop impact. Product development cycle times and the cost constraints often restrict the number of design variations tested for drop robustness prior to identification of the final configuration. Simulation models capable of predicting transient dynamics can provide valuable insight into the design reliability under shock environments. In this study, explicit finite-element models have been used to study the transient dynamics of printed circuit boards during drop from 6ft. Methodologies for modeling components using smeared-property formulations have been investigated. Reduced integration element formulations examined include shell and solid elements. Model predictions have been validated with experimental data. Results show that models with smeared properties can predict transient-dynamic response of board assemblies in drop impact fairly accurately. High-speed data acquisition system has been used to capture in situ strain, continuity, and acceleration data in excess of 1×106samples∕s. Ultra-high-speed video at 40,000fps has been used to capture the deformation kinematics. Component types examined include plastic ball-grid arrays, tape-array ball-grid array, quad-flat-no-lead package, and conduction-cooled ball-grid array. Model predictions have been correlated with experimental data. Impact of experimental error sources on model correlation with experiments has been also investigated

scholarly journals A Bayesian joint probability post-processor for reducing errors and quantifying uncertainty in monthly streamflow predictions

2012 ◽  
Vol 9 (10) ◽  
pp. 11199-11225
Author(s):  
P. Pokhrel ◽  
D. E. Robertson ◽  
Q. J. Wang
Keyword(s):  
Time Scales ◽  
Process Model ◽  
Joint Probability ◽  
Prediction Errors ◽  
Streamflow Forecasting ◽  
Post Process ◽  
Eastern Australia ◽  
Monthly Streamflow ◽  
Model Predictions ◽  
Seasonal Streamflow

Abstract. Hydrological post-processors refer here to statistical models that are applied to hydrological model predictions to further reduce prediction errors and to quantify remaining uncertainty. For streamflow predictions, post-processors are generally applied to daily or sub-daily time scales. For many applications such as seasonal streamflow forecasting and water resources assessment, monthly volumes of streamflows are of primary interest. While it is possible to aggregate post-processed daily or sub-daily predictions to monthly time scales, the monthly volumes so produced may not have the least errors achievable and may not be reliable in uncertainty distributions. Post-processing directly at the monthly time scale is likely to be more effective. In this study, we investigate the use of a Bayesian joint probability modelling approach to directly post-process model predictions of monthly streamflow volumes. We apply the BJP post-processor to 18 catchments located in eastern Australia and demonstrate its effectiveness in reducing prediction errors and quantifying prediction uncertainty.

Sign in / Sign up

Export Citation Format

Share Document