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A three-dimensional numerical model is developed to simulate the mold filling behavior in the plastic encapsulation of microchips. The conventional Hele--Shaw approximation is inadequate to analyze a complex molding compound flow behavior with multiple microchips in a single cavity. The developed numerical algorithm is based on the finite difference method combined with the robustness of volume of fluid volume-tracking method to solve the two-phase flow field in complex mold and die geometries. Twelve dies are arranged in a matrix-array in a single mold cavity. Short-shot experimental data are used to validate the numerical results for the melt flow front at different flow times. Close agreement between the experimental data and the numerical results demonstrates the applicability of the present computational model for the simulation of practical epoxy molding compound encapsulation. [DOI: 10.1115/1.4000719] Keywords: epoxy molding compound, Kawamura and Kuwahara technique, Cross model, finite difference method (FDM)

This study presents experimental investigation and optimization of heat input and coolant velocity based on the effective thermal conductivity of vertically oriented U-shaped twin heat pipe equipped with cooling fins, employed for PC-CPU cooling. The experimental design and optimization is accomplished by the design of experiment tool, response surface methodology. The results show that the heat input and the cooling air velocity have significant effect on the effective thermal conductivity. When the heat input was increased up to 50 W, the thermal conductivity increased and began to get off with further increase of heat input. For a given heat input, the thermal conductivity was found to increase with the increase of the air velocity up to 3 m/s and thereafter decreased. The results were optimized with the objective of maximizing the effective thermal conductivity, using Design-Expert software, and the optimized heat input and air velocity are 49.03 W and 2.90 m/s, respectively, the maximum thermal conductivity being 23839 W/m K. [ABSTRACT FROM AUTHOR]

This paper presents the development of flexible wings, flapping mechanism, and integrated electronic control system (ECS) to emulate the bat wing flapping for the ongoing micro air vehicle (MAV) research. Three bat species having dimensions close to the design requirement of MAV, namely, Mormopterus Planiceps, Nytophilus Geoffroyi, and Scotorepens Balstoni were selected, and the average of their physical dimensions was chosen. The commercially available titanium alloy, Ti ± 6Al ± 4V, was used for the wing frame, and the membrane was made of latex. A four-bar slider-crank mechanism was designed and fabricated to facilitate the wing flapping; ECS controlled the flapping frequency in the real-time mode. The system was tested in open air wind tunnel at frequency 6 Hz, angle of attack (AOA) 0-50°, and velocity range 2-7 m s−1. The experimental flapping angle which is compared with the theoretical flapping angle was obtained from the analytical kinematic model. The mean lift and drag coefficients were also measured and the results were found to be excellent. Compared to the manual control and measurement of flapping frequency, the proposed ECS demonstrates efficient control and accurate measurement. Moreover, the tedious procedure involved in the repeated calibrations for the manual system is totally eliminated by ECS. [ABSTRACT FROM AUTHOR]

Abstract: Copper based composites having hard reinforcements such as silicon carbide, alumina and cerium oxide do possess higher strength, better wear resistance and higher coefficient of friction when compared to copper. However, they pose several challenges in machining such as higher tool wear and inferior surface finish. On the other hand, copper based composites having soft reinforcements such as graphite, molybdenum disulphide and calcium fluoride do possess lower coefficient of friction and better machinability characteristics. Against this background, an attempt is made to develop a new class of copper composite materials by dispersing both the hard and soft reinforcements in appropriate proportions to ensure optimization of mechanical properties and machinability characteristics. In this paper the development and testing of copper–TiO2–boric acid composites by liquid metallurgy method is presented. Metallographic study, micro hardness, tensile strength, friction and wear tests on these hybrid composites have been carried out. The results show that copper–TiO2–boric acid composites possess higher hardness, higher tensile strength, higher coefficient of friction and better wear resistance when compared with pure copper. [Copyright &y& Elsevier]