M. S. Abdul Aziz

Influence of solder bump arrangements on molded IC encapsulation

Abstract This paper presents a fluid–structure interaction (FSI) analysis of ball grid array (BGA) package encapsulation. Real-time and simultaneous FSI analysis is conducted by using finite volume code (FLUENT) and finite element code (ABAQUS), which are coupled with MpCCI. A BGA integrated circuit (IC) package with different solder bump arrangements is considered in this study. In the FSI analysis, effects of solder bump arrangements on pressure distribution, void, deformation, and stress imposed on the IC structures are investigated. The maximum deformation and maximum stress on the silicon chip and solder bumps are evaluated. The findings indicate that the full-array solder bump package encounters lower stress and deformation during encapsulation. The void formation of each solder bump arrangement is examined. Scaled-up encapsulation is performed and the predicted flow front advancements are substantiated by experimental results. Results demonstrate the excellent capability of the proposed modeling tools for predictive trends of IC encapsulation. Thus, better understanding of IC encapsulation is provided to engineers and package designers in the microelectronics industry.

Thermal Fluid-Structure Interaction in the Effects of Pin-Through-Hole Diameter during Wave Soldering

An effective simulation approach is introduced in this paper to study the thermal fluid-structure interaction (thermal FSI) on the effect of pin-through-hole (PTH) diameter on the wave soldering zone. A 3D single PTH connector and a printed circuit board model were constructed to investigate the capillary flow behavior when passing through molten solder (63SnPb37). In the analysis, the fluid solver FLUENT was used to solve and track the molten solder advancement using the volume of fluid technique. The structural solver ABAQUS was used to examine the von Mises stress and displacement of the PTH connector in the wave soldering process. Both solvers were coupled by MpCCI software. The effects of six different diameter ratios (0.1 < d/D < 0.97) were studied through a simulation modeling. The use of ratio d/D = 0.2 yielded a balanced filling profile and low thermal stress. Results revealed that filling level, temperature, and displacement exhibited polynomial behavior to d/D. Stress of pin varied quadratically with the d/D. The predicted molten solder profile was validated by experimental results. The simulation results are expected to provide better visualization and understanding of the wave soldering process by considering the aspects of thermal FSI.

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.

Effect of Wing Deformation on the Aerodynamic Performance of Flapping Wings: Fluid-Structure Interaction Approach

Wing stiffness is very crucial in augmenting aerodynamic forces in flapping wing flyers. In this work, the effect of wing deformation was studied using three-dimensional numerical analysis (two-way fluid structure interaction), coupling the flow solver (FLUENT) and the structural (ABAQUS) solver via the MpCCI platform. Three different degrees of bending stiffness corresponding to rigid, flexible, and highly flexible case wings were investigated. Moreover, the wings were tested for both low Reynolds number (R=9,000) and high Reynolds number (R=40,000), at a flapping frequency of 9 Hz corresponding to an angle of attack (AoA) ranging from α=0 to 50°. The results of mean aerodynamic lift and drag coefficients showed good agreement between numerical and experimental findings. Also, the time-averaged lift-to-drag ratio reveals that the highly flexible wing exhibited the best overall aerodynamic performance when compared to the rigid and flexible wing.

Effects of Solder Temperature on Pin Through-Hole during Wave Soldering: Thermal-Fluid Structure Interaction Analysis

An efficient simulation technique was proposed to examine the thermal-fluid structure interaction in the effects of solder temperature on pin through-hole during wave soldering. This study investigated the capillary flow behavior as well as the displacement, temperature distribution, and von Mises stress of a pin passed through a solder material. A single pin through-hole connector mounted on a printed circuit board (PCB) was simulated using a 3D model solved by FLUENT. The ABAQUS solver was employed to analyze the pin structure at solder temperatures of 456.15 K (183°C) < T < 643.15 K (370°C). Both solvers were coupled by the real time coupling software and mesh-based parallel code coupling interface during analysis. In addition, an experiment was conducted to measure the temperature difference (ΔT) between the top and the bottom of the pin. Analysis results showed that an increase in temperature increased the structural displacement and the von Mises stress. Filling time exhibited a quadratic relationship to the increment of temperature. The deformation of pin showed a linear correlation to the temperature. The ΔT obtained from the simulation and the experimental method were validated. This study elucidates and clearly illustrates wave soldering for engineers in the PCB assembly industry.

Thermal fluid-structure interaction of PCB configurations during the wave soldering process

Purpose – This paper aims to investigate the thermal fluid–structure interactions (FSIs) of printed circuit boards (PCBs) at different component configurations during the wave soldering process and experimental validation. Design/methodology/approach – The thermally induced displacement and stress on the PCB and its components are the foci of this study. Finite volume solver FLUENT and finite element solver ABAQUS, coupled with a mesh-based parallel code coupling interface, were utilized to perform the analysis. A sound card PCB (138 × 85 × 1.5 mm3), consisting of a transistor, diode, capacitor, connector and integrated circuit package, was built and meshed by using computational fluid dynamics pre-processing software. The volume of fluid technique with the second-order upwind scheme was applied to track the molten solder. C language was utilized to write the user-defined functions of the thermal profile. The structural solver analyzed the temperature distribution, displacement and stress of the PCB and i...

Experimental and numerical investigation of flow and thermal effects on flexible printed circuit board

Abstract The desire of flexibility, compact, lightweight and low cost in current electronic device increases the application of flexible printed circuit board (FPCB). However, FPCB would encounter significant deflection and stress under operating condition (thermal factor) with air flow cooling system as compared to rigid printed circuit board (RPCB). Therefore, present study aims to investigate the effects of airflow rate and heat on FPCB attached with a ball grid array (BGA) package using experimental and numerical method. In this present study, the simulation was carried out by using FLUENT and ABAQUS, coupled in real time by Mesh-based Parallel Code Coupling Interface (MpCCI) where flow and thermal effects were coupled simultaneously. The experiments were conducted in a wind tunnel with the BGA package on the FPCB. Low discrepancy between simulation and experimental results indicated that the proposed numerical simulation method is proven to be reliable and sufficient to study the FPCB with thermal and flow effects which has not been established by previous researchers. The findings also showed that the Reynolds number and heat have significant effects on FPCBs deflection and stress. Therefore, it is important to include thermal effect when dealing with FPCB under flow environment. The outcomes of this paper can be a guideline to the FPCB industries.

Numerical Investigations of Membrane Surface Effects on NACA 643- 218 Airfoil

This paper presents two dimensional fluid structure interaction (FSI) CFD analysis on the effect of skin thickness and Reynolds number on the aerodynamic performance of NACA 643-218 airfoil. Numerical investigations were performed using FLUENT 6.3 fluid flow solver and ABAQUS 6.8-1 structural solver. Coupling of both solvers in real time mode was accomplished with the Mesh based parallel Code Coupling Interface (MpCCI 3.1). The predicted and experimental results were found to be in excellent match. Generally, the results showed that the aerodynamic lift increases while drag decreases with the decrease of membrane thickness.

Effect of gold concentration through a single dynamic wave soldering process

Gold possesses a unique combination of properties of particular value in the construction and operation of electrical and electronic equipment. These properties include low electrical resistivity and contact resistance, ease of thermal compression and high resistance to mechanical wear. Most efficient use is by employing gold, usually in the electroplated form, either as an intermediate layer in certain microelectronic devices, or as a finishing on such components as connectors, terminations, and printed circuits. This paper presents a study of interaction between tin-lead solder and pin, which are associated with intermetallic compound (IMC) after undergoing dynamic wave soldering. The aim of the study was to determine the effect of IMC formation to joint reliability by verifying the gold concentration as IPC J-Standards guidelines of a minimum of 3 wt% [1] [2] In our case study, the gold pins (without pre-tinned) are actually inserted directly into PCB and passed through dynamic wave soldering using wave pallet. The surface scanning electron microscopy and energy dispersive x-ray were used to reveal the concentration of gold present in the IMC microstructure after undergoing wave soldering (inserted into PCB). It was found that no gold presence for a thin PCB (thickness: 0.0596in or 1.514mm) and small percentage of gold presence (less than a minimum of 3 wt %) for a thick PCB (thickness: 0.30in or 7.62mm). Therefore, a double hot dip process is not required prior to assembly process.

Influence of solder joint length to the mechanical aspect during the thermal stress analysis

Solder joint is an important interconnector in surface mount technology (SMT) assembly process. The real time stress, strain and displacement of the solder joint is difficult to observe and assess the experiment. To tackle these problems, simulation analysis was employed to study the von Mises stress, strain and displacement in the thermal stress analysis by using Finite element based software. In this study, a model of leadless electronic package was considered. The thermal stress analysis was performed to investigate the effect of the solder length to those mechanical aspects. The simulation results revealed that solder length gives significant effect to the maximum von Mises stress to the solder joint. Besides, changes in solder length also influence the displacement of the solder joint in the thermal environment. The increment of the solder length significantly reduces the von Mises stress and strain on the solder joint. Thus, the understanding of the physical parameter for solder joint is important f...