Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

/pdf/light-emitting-diodes-ubzde6g9qc.pdf

Light-emitting diodes

Introduction to heat transfer

Light emitting diodes reliability review

A review of small heat pipes for electronics

Microelectronics technology Introduction A heart of silicon In a little black box Baseline CMOS Non-CMOS options Packaging Systems Conclusions References Nomenclature Reliability practices Introduction Reliability assessment Reliability statistics Acceleration factor models Failure mechanisms Conclusions References Exercises Thermal Management Introduction Heat transfer basics Thermal design of assemblies Thermal design for a SQFP Heatsink design choices Conclusions / final remarks References Introduction to Advanced Mechanics Introduction Stress and strain Failure criteria Fracture mechanics Finite element method References Exercises Thermo-Mechanics of Integrated Circuits and Packages Introduction IC Backend and packaging processes and testing Thermo-mechanics of IC backend processes Thermo-Mechanics of packaging processes Thermo-Mechanics of coupled IC backend and packaging processes Case studies References Exercises Characterization and Modeling of Moisture Behavior Introduction Moisture diffusion modeling Characterization of moisture diffusivity and saturation concentration Vapor pressure modeling Hygroscopic swelling characterization & modeling Single void Instability behavior Subjected to vapor pressure and thermal stress Interface strength characterization and modeling Case studies References Exercises Characterization and Modeling of Solder Joint Reliability Introduction Analytical-empirical prognosis of the reliability Thermo-mechanical characteristics of soft solders Data evaluation and LIFE-time estimation Case studies References Exercises Virtual thermo-mechanical prototyping Introduction The state-of-the-art of virtual prototyping Case studies Conclusions References Exercises Challenges and future perspectives Introduction Product and process inputs Tests and experiments Multi-scale mechanics Advanced simulation tools Multi-physics modeling Material and interface behavior Simulation-based optimization Conclusions

Mechanics of Microelectronics

Experimental investigations and model study of moisture behaviors in polymeric materials

This paper first examines the commonly-used thermal-moisture analogy approach in thermal-moisture analogy approach. We conclude that such an analogy using a normalized concentration approach does not exist in the case of soldering reflow, when the solubility of each diffusing material varies with temperature or the saturated moisture concentration is not a constant over an entire range of reflow temperatures. The whole field vapor pressure distribution of a flip chip BGA package at reflow is obtained based on a multiscale vapor pressure model. Results reveal that moisture diffusion and vapor pressure have different distributions and are not proportional. The vapor pressure in the package saturates much faster than the moisture diffusion during reflow. This implies that the vapor pressure reaches the saturated pressure level in an early stage of moisture absorption, even the package is far from moisture saturated. However, the interfacial adhesion degrades continuously with moisture absorption. Therefore, the package moisture sensitivity performance will largely reply on the adhesion strength at elevated temperature with moisture. A specially designed experiment with a selection of six different underfills for flip chip packages was conducted. Results confirm that there is no correlation between moisture absorption and the subsequent interface delamination at reflow. The adhesion at high temperature with moisture is the only key modulator that correlates well with test data. Such a parameter is a comprehensive indicator, which includes the effects of thermal mismatch, vapor pressure, temperature and moisture. In this paper, a micromechanics based mechanism analysis on interfacial delamination is also presented. With the implementation of interface properties into the model study, it shows that the critical stress, which results in the unstable void growth and delamination at interface, is significantly reduced when the effect of moisture on debonding is considered.

Xuejun Fan

Papers

A review of small heat pipes for electronics

Mechanics of Microelectronics

Experimental investigations and model study of moisture behaviors in polymeric materials

Interfacial Delamination Mechanisms During Soldering Reflow With Moisture Preconditioning

Convective heat transfer characteristics of China RP-3 aviation kerosene at supercritical pressure