C. Y. Khor

Investigation of the fluid/structure interaction phenomenon in IC packaging

Abstract In the present study, experiment and simulation studies were conducted on the fluid/structure interaction (FSI) analysis of integrated circuit (IC) packaging. The visualisation of FSI phenomenon in the actual package is difficult due to limitations of package size, available equipment, and the high cost of the experimental setup. However, the experimental data are necessary to validate the simulation results in the FSI analysis of IC packaging. Scaled-up package size was fabricated to emulate the encapsulation of IC packaging and to study the effects of FSI phenomenon in the moulded package. The interaction between the fluid and the structure was observed. The deformation of the imitated chip was studied experimentally. The air-trap mechanism that occurred during the experiment is also presented in this paper. Simulation technique was utilised to validate the experimental result and to describe the physics of FSI. The predicted flow front was validated well by the experiment. Hence, the virtual modelling technique was proven to be excellent in handling this problem. The study also extends FSI modelling in actual-size packaging.

Finite volume based CFD simulation of pressurized flip-chip underfill encapsulation process

This paper presents the simulation of pressurized underfill encapsulation process for high I/O flip chip package. 3D model of flip chip packages is built using GAMBIT and simulated using FLUENT software. Injection methods such as central point, one line, L-type and U-type are studied. Cross-viscosity model and volume of fluid (VOF) technique are applied for melt front tracking of the encapsulant. The melt front profiles and pressure field for all injection types are analyzed and presented. The pressure distribution within the flip-chip, fill volume versus filling time and viscosity versus shear rate are also plotted. The U-type injection is found to be faster in filling. The numerical results are compared with the previous experimental results and found in good conformity. The strength of CFD software in handling underfill encapsulation problems is proved to be excellent.

Application of flexible printed circuit board (FPCB) in personal computer motherboards: Focusing on mechanical performance

Flexible printed circuit boards (FPCBs) are being used extensively in current electronics devices because of their excellent flexibility, light weight, and reduced thickness. In the present study, a proposed novel approach that utilizes FPCB as a substrate for motherboards is investigated. Deflection and stress are the key factors that determine the feasibility of FPCB motherboards. As flow velocity increases, flow-induced deflection and stress also become more prominent. The present study also explores several configurations of the motherboard, such as different fastening options and component layouts. This fluid–structure interaction (FSI) study is performed using the fluid solver FLUENT and the structural solver ABAQUS, coupled online using the Mesh-based Parallel Code Coupling Interface (MpCCI). A simple experiment was also conducted to substantiate the FSI simulation technique utilized in the present study. Although the present study on FPCB primarily focuses on the motherboard, the findings could also provide information for other FPCB applications.

Optimization of IC encapsulation considering fluid/structure interaction using response surface methodology

Abstract Optimized design of the integrated circuit (IC) package gives better IC encapsulation process and minimizes the stress concentration and deformation of the IC structures. The physical and process parameters (i.e., pressure inlet, solder bump standoff height, chip thickness, gap-wise between chips, and mould and filled time) were optimized via response surface methodology using central composite design (CCD) to minimize the stress concentration of chip and solder bump, chip deformation, and void in package during the IC encapsulation process. The optimization of the moulded IC encapsulation is carried out by considering the fluid/structure interaction (FSI) aspects. The optimum empirical models were tested and well confirmed with the simulation results. The optimum design of the IC package (20xa0mmxa0×xa020xa0mm) with perimeter solder bump arrangement for both physical and process parameters was characterized by 150xa0μm of solder bump standoff height, 250xa0μm of chip thickness, and 50.43xa0μm of gap-wise at the inlet condition of 3.43xa0MPa.

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.

Analysis of fluid/structure interaction: Influence of silicon chip thickness in moulded packaging

Abstract Experimental and simulation studies of the three-dimensional (3D) analysis of fluid/structure interaction (FSI) in moulded packaging are presented in the current paper. The miniature size of integrated circuit package and the high cost of experimental setup make FSI visualization in actual packaging difficult. In the present study, a scaled-up moulded package was fabricated to observe the FSI phenomenon in package encapsulation by experiments. Virtual modelling using the Mesh-based parallel Code Coupling Interface method was employed to describe the physics of FSI and validate the experimental results. The FSI analysis was extended to the effects of different silicon chip thicknesses (50, 100, 150, 200, and 250xa0μm) on actual-size packaging. The silicon chip and solder bump structures were evaluated in relative to stress and deformation. The mechanisms of flow-front filling and air traps were also experimentally investigated. The FSI phenomenon of scaled-up packaging was observed. The predicted flow front and chip deformation were well validated by the experiments. Hence, the virtual modelling presented in the current study was proven excellent in handling packaging problems.

Optimization of flexible printed circuit board electronics in the flow environment using response surface methodology

Abstract A flexible printed circuit board (FPCB) is flexible, thin and lightweight; however, FPCBs experience more deflection and stress in the flow environment because of fluid–structure interaction (FSI), which affects their performance. Therefore, the present study focuses to optimize a typical FPCB electronic in order to minimize the deflection and stress induced in the system. In this study, numeric parameters (i.e., flow velocity, component size, component thickness, misalignment angle, as well as the length and width of the FPCB) were optimized using response surface methodology (RSM) with the central composite design technique. The separate effects of the independent variables and their interactions were investigated. The optimized condition was also examined to substantiate the empirical models generated using RSM. At a flow velocity of 5xa0m/s, the optimum values of the component size, component thickness, misalignment angle, as well as the length and width of the FPCB were determined at 11.69xa0mm, 12.37xa0mm, −0.73°, as well as 180xa0mm and 180xa0mm, respectively. This optimized condition resulted in a maximum deflection of 0.402xa0mm and a maximum stress of 0.582xa0MPa. The findings conveyed can contribute to the development of FPCB industries.

Recent fluid–structure interaction modeling challenges in IC encapsulation – A review

The rapid development of computing software has facilitated multifarious research in integrated circuit (IC) packaging. Complicated and complex processes can be visualized via simulation modeling with this software. The applications of aided software enhance the fundamental physicochemical understanding and visualization of the IC encapsulation process. In this article, fluid–structure interaction (FSI) during IC encapsulation through computer-aided simulation is reviewed based on the amount of substantial work conducted from the past decades to the present. FSI phenomena in various IC encapsulations, such as wire sweep, paddle shift, lead frame deformation, IC chip, and through-silicon via (TSV) deformation, is considered in the review. The significance and challenges of FSI analysis are also highlighted in this article.

Finite volume-based simulation of the wave soldering process: Influence of the conveyor angle on pin-through-hole capillary flow

ABSTRACT This study aims to investigate the influence of a conveyor angle on capillary flow during the wave soldering process. Finite volume-based simulation is utilized to study the capillary flow of molten solder. Molten solder filling through capillary action of a pin-through-hole (PTH) is considered at different conveyor angles (i.e., 0–10°). Two PTH positions, namely, center (r/R = 0.2) and offset (r/R = 0.6), are investigated. The effects of a conveyor angle on molten solder filling volume, time, pressure profile, and velocity vector are numerically analyzed.