Aizat Abas

Effect of thermocapillary action in the underfill encapsulation of multi-stack ball grid array

Abstract Recent trend in electronic industries are demanding smaller chip packaging process along with increase in performance and reliability of the package. The introduction of Multi-stack Ball Grid Array (BGA) to enhance the performance of the conventional BGA flip chip has frequently encountered several hitches such as extended filling time and incomplete filling at the upper layer of the multi-stacks BGA. It has been found that the encapsulant lacks energy to flow at the upper layer due to lower hydrostatics pressure. In this paper, a straightforward solution by incorporating additional thermal energy in the encapsulant to increases its flow ability is introduced. This additional thermal energy at the upper layer produces a distinct temperature difference between the upper and lower layers, or simply thermal delta. This research attempts to demonstrate the effectiveness of thermal delta in solving the aforementioned flow problem during encapsulation process of multi-stacks BGA, by means of experiment and numerical simulation. The findings have shown that the experimental data compares well with the simulation results. It was also found that the implementation of thermal delta substantially reduces the filling time across the multi-stack packages. This study reveals the potential of thermocapillary-driven underfill encapsulation being widely adopted in future industrial encapsulation of multi-stacks BGA packaging.

Assessment of porous media burner for surface/submerged flame during porous media combustion

The applications of porous media burners are of often keen interest to researchers because of many modern advantages, such as high thermal efficiency, stable flame and low emission rate. In this current experimental work, a microburner was made built to achieve both surface and submerged flame for three different thicknesses of reaction layers. A reaction layer of discrete alumina with a predefined thickness of preheat layer was used for combustion. Reaction layer was accordingly replaced with different thicknesses of 10mm, 20mm and 30mm. This work mainly aimed to show burner behavior with increase in thickness of reaction layer thus suggesting the optimum equivalence ratio from best burner performance. Interesting and unique behavior of the burner was encountered for each thickness of the reaction layer. Highest surface temperature was found out with 10mm of reaction layer, while highest wall temperature was incorporated with 20mm of reaction layer. Equivalence ratio of 0.3 is best suitable for optimum p...

Lattice Boltzmann Model of 3D Multiphase Flow in Artery Bifurcation Aneurysm Problem

This paper simulates and predicts the laminar flow inside the 3D aneurysm geometry, since the hemodynamic situation in the blood vessels is difficult to determine and visualize using standard imaging techniques, for example, magnetic resonance imaging (MRI). Three different types of Lattice Boltzmann (LB) models are computed, namely, single relaxation time (SRT), multiple relaxation time (MRT), and regularized BGK models. The results obtained using these different versions of the LB-based code will then be validated with ANSYS FLUENT, a commercially available finite volume- (FV-) based CFD solver. The simulated flow profiles that include velocity, pressure, and wall shear stress (WSS) are then compared between the two solvers. The predicted outcomes show that all the LB models are comparable and in good agreement with the FVM solver for complex blood flow simulation. The findings also show minor differences in their WSS profiles. The performance of the parallel implementation for each solver is also included and discussed in this paper. In terms of parallelization, it was shown that LBM-based code performed better in terms of the computation time required.

Particle image velocimetry experiment of blood flow through stent in artery bifurcation aneurysm problem

In this work, an idealized artery bifurcation aneurysm model is created and fabricated. A type of stent configurations namely half-Y (6mm) is constructed and deployed in the artery model. The effect of stent placement on the flow pattern, velocity and pressure are analyzed using particle image velocimetry (PIV) measurement. Aqueous glycerol solution is used as the working fluid to mimic properties of human blood. Based on the results, the use of half-y stent managed to reduce the blood velocity flowing into the aneurysm sac by more than half. This will reduce the size of the aneurysm gradually as the flow reduces.