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Purpose This paper aims to study the interfacial delamination found in the boundary of the copper/copper-epoxy layers of a multi-layer ceramic capacitor. Design/methodology/approach The thermal reflow process of the capacitor assembly and the crack propagation from the initial micro voids presented in the boundary, and later manifested into delamination, were numerically simulated. Besides, the cross section of the capacitor assembly was inspected for delamination cracks and voids using a scanning electronic microscope. Findings Interfacial delamination in the boundary of copper/copper-epoxy layers was caused by the thermal mismatch and growth of micro voids during the thermal reflow process. The maximum deformation on the capacitor during reflow was 2.370 µm. It was found that a larger void would induce higher vicinity stress, mode I stress intensity factor, and crack elongation rate. Moreover, the crack extension increased with the exerted deformation until 0.3 µm, before saturating at the peak crack extension of around 0.078 µm. Practical implications The root cause of interfacial delamination issues in capacitors due to thermal reflow has been identified, and viable solutions proposed. These can eliminate the additional manufacturing cost and lead time incurred in identifying and tackling the issues; as well as benefit end-users, by promoting the electronic device reliability and performance. Originality/value To the best of the authors’ knowledge, the mechanism of delamination occurrence in a capacitor during has not been reported to date. The parametric variation analysis of the void size and deformation on the crack growth has never been conducted.

The increasing demands in the miniaturization of microelectronic products promotes the automation of electronic assembly and manufacturing process such as laser soldering to deliver high quality and flexibility of solder joints. This paper investigates possibility of using computational fluid dynamics (CFD) to create simulation of laser soldering process. Heating process of solder phase was simulated Using finite volume method (FVM) and energy equation enabled. Results of the simulation was compared with experiment for validation. Generally, it is found that the solder formation is identical for both simulation and experimental process. Moreover, the temperature distribution shows that heating process of laser soldering has great heating distribution along the solder region.

Dam failure is undeniably catastrophic and one of its major causes is the soil erosion near the dam structure. In this paper, the characteristics and compositions of soil sediment in dam spillway structure were investigated to determine its impact on the occurrence of erosion. Four suspended samples were taken from the vicinity of Ogee dam spillway. Sediment analysis using scanning electron microscope revealed that the soils consist of relative high metal contents of aluminium, iron and magnesium. These metals will attribute to the erosion of dam wall, which subsequently reduce the durability of wall against high hydrostatic pressure exerted by the reservoir. Nonetheless, as the average sizing of suspended particles at each sampling location were capped at 4.55 μm, the damages incurred to the dam were minimal. Additionally, the suspended particles around the dam spillway was numerically simulated with the inclusion of discrete phase model. The numerical data were in great consensus with the corresponding finding attained from the particle image velocimetry experimental of a scaled-down dam model, with the discrepancy not more than 4.89 %. The movement of suspended particles due to the water flow can be tracked numerically and it is found the sediment prone to accumulate at the vicinity of dam spillway.

Purpose This paper aims to study the filling progression of underfill flow and void formation during the flip-chip encapsulation process. Design/methodology/approach A new parameter of filling progression that relates volume fraction filled to filling displacement was formulated analytically. Another indicative parameter of filling efficiency was also introduced to quantify the voiding fraction in filling progression. Additionally, the underfill process on different flip-chips based on the past experiments was numerically simulated. Findings All findings were well-validated with reference to the past experimental results, in terms of quantitative filling progression and qualitative flow profiles. The volume fraction filled increases monotonically with the filling displacement and thus the filling time. As the underfill fluid advances, the size of the void decreases while the filling efficiency increases. Furthermore, the void formed during the underfilling flow stage was caused by the accelerated contact line jump at the bump entrance. Practical implications The filling progression enabled manufacturers to forecast the underfill flow front, as it advances through the flip-chip. Moreover, filling progression and filling efficiency could provide quantitative insights for the determination of void formations at any filling stages. The voiding formation mechanism enables the prompt formulation of countermeasures. Originality/value Both the filling progression and filling efficiency are new indicative parameters in quantifying the performance of the filling process while considering the reliability defects such as incomplete filling and voiding.

One of foremost issue arise in the dam management and dam reliability assessment is the sedimentation of suspended particles. Sedimentation affected the energy production and efficiency, storage, discharge capacity, and flood attenuation capabilities. In this paper, the sediment transport and scouring in the dam spillway structure was modelled using finite volume method (FVM) based software, ANSYS. The trajectory of suspended particles in the water flow was formulated based on the discrete phase model (DPM). To access the simulation model, particle image velocimetry (PIV) experiment using scaled-down dam spillway model was conducted. The discrepancy between the findings attained from simulation and PIV experiment is less than 4.89%, inferred the numerical model was acceptable. It was found that the maximum scouring rate and maximum deposition rate are respectively 4.20×10−9 kg/s and 2.00×10−6 kg/s. As such, it was empirically approximated the dam maintenance should be scheduled once every 8.9 years, based on sole consideration on resolving the scouring and deposition of suspended particles. This work demonstrated the viability of DPM based numerical simulation in study the fluid-particle interaction of sediment transport problem, particularly for the application of dam reliability.

The formation of vortex and swirling in any flow structures of the hydropower dam is undesirable, as it reduced the performance of turbine as well as lowered the efficiency of hydroelectric power generation. Furthermore, it could lead to the hydraulic losses at the entrance of power intakes, the blockage at the trash racks due to entrain debris and the reduction of the working life of turbines. This paper studied penstocks flows in the dam intake section numerically. The dynamics of penstocks flows at different operating conditions were analyzed to determine the vortex formation. To access the veracity of the current proposed numerical model, a validating study based on the particle image velocimetry (PIV) experiment was conducted. It was found the discrepancy between both numerical and experimental flow velocities is 12%, implying the numerical model is well-validated and the corresponding findings are acceptable. It was found that the vortex was formed in the penstock that located at the lowest level relative to other penstocks. Furthermore, the highest pressure of 4 MPa was recorded at the bottom section of the penstock which observed vortex. This numerical work provided useful insights for the future dam reliability analysis, particularly involving penstocks and intake section.

Purpose This paper aims to present new analytical model for the filling times prediction in flip-chip underfill encapsulation process that is based on the surface energetic for post-bump flow. Design/methodology/approach The current model was formulated based on the modified regional segregation approach that consists of bump and post-bump regions. Both the expansion flow and the subsequent bumpless flow as integrated in the post-bump region were modelled considering the surface energy–work balance. Findings Upon validated with the past underfill experiment, the current model has the lowest root mean square deviation of 4.94 s and maximum individual deviation of 26.07%, upon compared to the six other past analytical models. Additionally, the current analytically predicted flow isolines at post-bump region are in line with the experimental observation. Furthermore, the current analytical filling times in post-bump region are in better consensus with the experimental times as compared to the previous model. Therefore, this model is regarded as an improvised version of the past filling time models. Practical implications The proposed analytical model enables the filling time determination for flip-chip underfill process at higher accuracy, while providing more precise and realistic post-bump flow visualization. This model could benefit the future underfill process enhancement and package design optimization works, to resolve the productivity issue of prolonged filling process. Originality/value The analytical underfill studies are scarce, with only seven independent analytical filling time models being developed to date. In particular, the expansion flow of detachment jump was being considered in only two previous works. Nonetheless, to the best of the authors’ knowledge, there is no analytical model that considered the surface energies during the underfill flow or based on its energy–work balance. Instead, the previous modelling on post-bump flow was based on either kinematic or geometrical that is coupled with major assumptions.

Dam reliability analysis is performed to determine the structural integrity of dams and, hence, to prevent dam failure. The Chenderoh Dam structure is divided into five parts: the left bank, right bank, spillway, intake section, and bottom outlet, with each element performing standalone functions to maintain the overall Dam’s continuous operation. This study presents a numerical reliability analysis of water dam reservoir banks using fluid–structure interaction (FSI) simulation of the bottom outlet structures operated at different discharge conditions. Three-dimensional computer-aided drawings were used to view the overall Chenderoh Dam. Next, a two-way fluid–structure interaction (FSI) model was developed to explore the influence of fluid flow and structural deformation on dam systems. The FSI modeling consists of Ansys Fluent and Ansys Structural modules to consider the boundary conditions separately. The reliability and performance of the reservoir bottom outlet structure was effectively simulated and recognised using FSI. The maximum stress on the bottom outlet section is 18.4 MPa, which is lower than the yield stress of mild steel of 370 MPa. Therefore, there will be no structural failure being observed on the bottom outlet section when the butterfly valve is fully closed. With a few exceptions, the FSI models projected that bottom outlet structures would be able to run under specified conditions without structural collapse or requiring interventions due to having lower stress than the material’s yield strength.

Purpose This paper aims to determine the optimum set of temperatures through correlation study to attain the most effective capillary flow of underfill in a multi-stack ball grid array (BGA) chip device. Design/methodology/approach Finite volume method is implemented in the simulation. A three-layer multi-stack BGA is modeled to simulate the underfill flow. The simulated models were well validated with the previous experimental work on underfill process. Findings The completion filling time shows high regression R-squared value of up to 0.9918, which indicates a substantial acceleration on the underfill process because of incorporation of thermal delta. An introduction of 11 °C thermal delta to the multi-stacks BGA managed to reduce the filling time by up to 16.4%. Practical implications Temperature-induced capillary flow is a relatively new type of driven underfill designed specifically for package on package BGA components. Its simple implementation can further improve the productivity of existing underfill process in the industry that is desirable in reducing the process lead time. Originality/value The effect of temperature-induced capillary flow in underfill encapsulation on multi-stacks BGA by means of statistical correlation study is a relatively new topic, which has never been reported in any other research according to the authors’ knowledge.

Laser soldering is becoming more popular for soldering pin through-hole (PTH) components onto printed circuit boards (PCBs). Solder volume influences soldering joint reliability. However, it is difficult to accurately measure the effect of solder volume during the laser soldering process. The finite volume method (FVM) is used to simulate the molten solder flow in laser soldering to connect the through-hole capacitor onto the PCB in ansysfluent software. The simulation results reveal the effects of different SAC305 solder volumes on joining quality in terms of fillet shape formation, pressure, and velocity. The preferred solder volume is 1.517 mm3 with a filling time of 1.7 s, a temperature of 642 K, a hole diameter of 1.0 mm, a lead diameter of 0.5 mm and a PCB thickness of 1.20 mm, produces a fillet shape similar to a real sample of PTH laser soldering joint from the industry. This ideal volume was chosen with a suitable pressure and velocity to create a nice concave fillet shape and minimize voids during soldering. The pressure and velocity increase when the solder volume increases causing solidified solder to melt. The discrepancy between numerical and experimental values of fillet height is comparable, which inferred that the numerical model was well-validated. The good consistency between both results proves that the finite volume model will effectively predict the optimum solder volume. This opens up new opportunities for the optimization of the laser soldering parameters in the application of electronic manufacturing.

Recently, the addition of new materials into the conventional solder pastes provides a viable solution to optimize the material characteristics and properties of the nano-particle filled solder paste. Addition of titanium oxide (TiO2) nanoparticles shown that it can enable better performance of the solder. However, actual industry experiment in terms of its optimum thermal profile for improved strength through good spread of nano-particles in the solder is very costly and lengthy to set up. Hence, this paper presents a preliminary study of the interaction between two models of numerical simulation namely volume of fluid (VOF) and discrete phase model (DPM) then compare with previous experimental data. This paper aims to analyse the effect of peak temperature towards the fillet height of ultra-fine Sn-Ag-Cu (SAC) solder joints doped with TiO2 nanoparticles in an electronic assembly. For the purpose of this research, the weight percentage of the nanoparticles TiO2 with the SAC305 lead-free reinforced solder is varied at different peak temperature and investigated in terms of particles distribution, fillet height and thermal strain. This paper presents a 3D numerical simulation of nano-reinforced lead (Pb)-free solder at the ultra-fine joint component for 01005 capacitor with dimension of 0.2 x 0.2 x 0.4 mm³. The results obtained are confirmed by conducting an experiment using a field emission scanning electron microscope (SEM) joined with an EDS and X-ray diffraction machine. This study concludes that the best fillet height would be obtained at 250°C. The distributions of nanoparticles with 0.01 wt%, 0.05 wt%, and 0.15 wt% of weighted percentage are effectively observed by using the HRTEM analysis. Based on the study, higher temperature of the wetting region that range between 240°C and 255°C results in better particle distributions, and fillet height of the solder by using temperature in that range meets the requirement of IPC standards.

Purpose The purpose of the study is to investigate the spatial aspects of underfill flow during the flip-chip encapsulation process, for instance, meniscus evolution and contact line jump (CLJ). Furthermore, a spatial-based void formation mechanism during the underfill flow was formulated. Design/methodology/approach The meniscus evolution of underfill fluid subtended between the bump array and the CLJ phenomenon were visualized numerically using the micro-mesh unit cell approach. Additionally, the meniscus evolution and CLJ phenomenon were modelled analytically based on the formulation of capillary physics. Meanwhile, the mechanism of void formation was explained numerically and analytically. Findings Both the proposed analytical and current numerical findings achieved great consensus and were well-validated experimentally. The variation effects of bump pitch on the spatial aspects were analyzed and found that the meniscus arc radius and filling distance increase with the pitch, while the subtended angle of meniscus arc is invariant with the pitch size. For larger pitch, the jump occurs further away from the bump entrance and takes longer time to attain the equilibrium meniscus. This inferred that the concavity of meniscus arc was influenced by the bump pitch. On the voiding mechanism, air void was formed from the air entrapment because of the fluid-bump interaction. Smaller voids tend to merge into a bigger void through necking and, subsequently, propagate along the underfill flow. Practical implications The microscopic spatial analysis of underfill flow would explain fundamentally how the bump design will affect the macroscopic filling time. This not only provides alternative visualization tool to analyze flow pattern in the industry but also enables the development of accurate analytical filling time model. Moreover, the void formation mechanism gave substantial insights to understand the root causes of void defects and allow possible solutions to be formulated to tackle this issue. Additionally, the microfluidics sector could also benefit from these spatial analysis insights. Originality/value Spatial analysis on underfill flow is scarcely conducted, as the past research studies mainly emphasized on the temporal aspects. Additionally, this work presented a new mechanism on the void formation based on the fluid-bump interaction, in which the formation and propagation of micro-voids were numerically visualized for the first time. The findings from current work provided fundamental information on the flow interaction between underfill fluid and solder bump to the package designers for optimization work and process enhancement.

Renal arteries are the arteries that supply blood to the kidneys. Renal arteries are the arteries that supply blood to the kidneys. Renal artery aneurysm (RAA) is the second most common visceral aneurysm to occur, which accounts for 22% of the visceral aneurysm. In general population, RAA rate of occurrence was only 0.1%. However, due to the extensive used of angiography technique, RAA has been discovered more frequently. Some claimed that the previous rate of incidence should be higher now because of the capability of angiography. The rupture of this aneurysm could result in haemorrhage, kidney lost and mortality. The size of the renal artery which is different compared to other types of arteries such as the abdominal aorta could produce different flow condition when the artery is inflicted with RAA condition. Thus, a thorough analysis is desired as RAA studies are very limited compared to other aneurysm conditions. In this study, the efficiency of the stent porosity was investigated in treating the RAA. Fluid-structure interaction (FSI) simulations and particle image velocimetry (PIV) experiments were the approaches taken to investigate the flow patterns of the blood when the stent of different porosities was placed in the aneurysm entrance. The effect of wall shear stress (WSS), the deformation of the artery and von Mises stress were also observed in determining the possibility of aneurysm rupture. The study found that the placement of stent of different porosities succeeds in providing an obstruction to the blood from circulating inside the aneurysm sac. This in turns reduced the WSS experienced by the aneurysm sac up a significant value of 96%. This reduction is crucial in order to prevent the aneurysm from rupture. Moreover, the placement of the stent provided support to the renal artery and preventing it from experiencing buckling failure. The maximum deformation of the artery reduced by 42% with stent was placed in the renal artery. In fact, the von Mises stress decreased below the threshold limit of 0.5 MPa with the presence of the stent. In addition, the study found that the stent of porosity 80% has a similar impact to the stent of lower porosity in the case of RAA at main renal artery.

Purpose In line with the recent development of flip-chip reliability and underfill process, this paper aims to comprehensively investigate the effect of different hourglass shape solder joint on underfill encapsulation process by mean of experimental and numerical method. Design/methodology/approach Lattice Boltzmann method (LBM) numerical was used for the three-dimensional simulation of underfill process. The effects of ball grid arrays (BGA) encapsulation process in terms of filling time of the fluid were investigated. Experiments were then carried out to validate the simulation results. Findings Hourglass shape solder joint has shown the shortest filling time for underfill process compared to truncated sphere. The underfill flow obtained from both simulation and experimental results are found to be in good agreement for the BGA model studied. The findings have also shown that the filling time of Hourglass 2 with parabolic shape gives faster filling time compared to the Hourglass 1 with hemisphere angle due to bigger cross-sectional area of void between the solder joints. Practical implications This paper provides reliable insights to the effect of hourglass shape BGA on the encapsulation process that will benefit future development of BGA packages. Originality/value LBM numerical method was implemented in this research to study the flow behaviour of an encapsulation process in term of filling time of hourglass shape BGA. To date, no research has been found to simulate the hourglass shape BGA using LBM.

Three-dimensional stepped spillway problems are simulated numerically using smoothed particle hydrodynamics (SPH) to visualize the flow of water along the steps and its flow dynamics. In particular, two distinct scaled-down stepped spillway models were studied with each having barrier heights of 10 mm and 25 mm, respectively. The impact of varying the height of the barrier in the design of the stepped spillway is studied in terms of it flow pattern, flow dynamics, aeration efficiency and oxygenation performances. State-of-the-art particle image velocimetry (PIV) experiment was carried out to affirm the validity of SPH findings and it turns out that both the water flow patterns attained in the SPH and PIV are quantitatively comparable. Further quantitative analysis revealed that the flow velocities in both methodologies are in great consensus. Conclusively, this has demonstrated that the capability and reliability of SPH to precisely approximate the water using finite set of particles to model the flow along the stepped spillway. Both stepped spillway configurations show nappe flow regime as the water descends down the steps. Nonetheless, vigorous hydraulic jump phenomena that is associates with the formation of turbulence and vortices is prominently observed in the configuration with larger barrier height. Decisive SPH data obtained concluded that as the barrier height increases from 10 mm to 25 mm, the water flows down the steps faster at lower pressure value and the overall aeration efficiency is improved from 1.1% to 1.2%. The usage of the higher barrier would promote the occurrence of substantial air entrainment during water swirling that will increase the power dissipation in flow. Subsequently, this while lower the power drawn to achieve the desired aeration effect. Ultimately, this study has justified the critical influence of barrier height dimension on the stepped spillway flow behavior and aeration performance.

Recent advances in the micro-electronics industry have increased the demand for smaller and more compact package devices with higher performance. This paper presents an analytical multiparametric design optimization approach for the miniaturization of flip-chip package, while considering the filling time of the subsequent underfill encapsulation process. The design optimization approach was based on the latest regional segregation-based analytical filling time model. Numerical simulation was conducted to verify the governed analytical model. The discrepancies in the filling times are less than 9.9%, and the predicted critical bump pitch has a low deviation of 4.1%, affirming that both the analytical and numerical models were in great consensus. The variation effects of bump pitch, gap height, and contact angle on the filling time were analyzed and discussed thoroughly. Both the critical bump pitch and the critical gap height were computed and fitted into respective empirical equations. Subsequently, a new multiparametric design optimization approach based on the thresholding and criticality of underfill parameters was proposed to determine the optimum parameters that yield to the most compact flip-chip package with acceptable low filling time during the encapsulation process. Lastly, this proposed optimization technique was tested on the four flip-chips used in a previously published underfill experiment.

The conventional method of selective soldering has been practiced using wave soldering, convection reflow, and hand soldering. However, due to industry automation and high demand for quality, repeatability and flexibility, laser soldering process has been developed to meet these demands. This article investigates the effect of different temperature of laser soldering process on lead-free solder (SAC305) by means of numerical method that is validated by experiment. Finite volume method (FVM) was used for the three-dimensional simulation to simulate the filling flow of the lead-free solder. Experiments were carried out to complement simulation validity and the results of both methods show good agreement. The findings show that a better result can be achieved when the angle of component lead (θle) approaches 90 deg. Using optimized lead angle, five different temperature simulations were set in the range of 550 K

This work detailed the particle image velocimetry (PIV) experimental approach used for the flow visualization on costal problem, based on the simple case study of liquid-sediment model. The current PIV experiment involved the use of laser illumination system, high speed camera, filler particles and wave-motion generator. Furthermore, the investigated simple small-scaled liquid-sediment model was constructed using a pile of sands in an aquarium tank. The subsequent image processing and analysis were conducted using PIVlab software. From the present PIV work, the velocity contours of the water flow near the sediment profile can be obtained.

The scope of review of this paper focused on the precuring underfilling flow stage of encapsulation process. A total of 80 related works has been reviewed and being classified into process type, method employed, and objective attained. Statistically showed that the conventional capillary is the most studied underfill process, while the numerical simulation was mainly adopted. Generally, the analyses on the flow dynamic and distribution of underfill fluids in the bump array aimed for the filling time determination as well as the predictions of void occurrence. Parametric design optimization was subsequently conducted to resolve the productivity issue of long filling time and reliability issue of void occurrence. The bump pitch was found to the most investigated parameter, consistent to the miniaturization demand. To enrich the design versatility and flow visualization aspects, experimental test vehicle was innovated using imitated chip and replacement fluid, or even being scaled-up. Nonetheless, the analytical filling time models became more accurate and sophiscasted over the years, despite still being scarce in number. With the technological advancement on analysis tools and further development of analytic skills, it was believed that the future researches on underfill flow will become more comprehensive, thereby leading to the production of better packages in terms of manufacturing feasibility, performances, and reliability. Finally, few potential future works were recommended, for instance, microscopic analysis on the bump–fluid interaction, consideration of filler particles, and incorporation of artificial intelligence.

Underfill encapsulation process regularly encounters productivity issue of long filling time that incurs additional manufacturing costs. The package was optimized to attain least filling time while retaining the miniature package size. This paper presents a new analytical generalized filling time chart that was generated using the latest regional segregation-based analytical filling time model. The governing model was well-validated to the industrial underfill benchmark data with discrepancy of less than 10.42%. The filling time chart gives non-dimensionalized filling times at various combinations of bump pitch, gap height, and contact angle. Subsequently, another chart that gives the filling time coefficient was derived from the filling time chart to compute the instantaneous filling time directly. Interestingly, two variation trends of bump pitch were observed from the filling time chart that were distinguishable based on the critical contact angle. When the contact angle exceeds its critical value, there exists the critical bump pitch that restricted the miniature design of the package. On contrary, all past literatures only elucidated one variation trend of bump pitch without introduced the critical contact angle. Overall, the analytical filling time chart benefited the optimization study as it concisely composed all parametric variation trends of filling time as well as the criticality of underfill parameters. Thus, time and effort can be greatly reduced upon compared with the conventional numerical-based optimization work, without compromising the accuracy aspect.

Purpose This paper aims to introduce a new indicative parameter of filling efficiency to quantify the performance and productivity of the flip-chip underfill encapsulation process. Additionally, the variation effect of the bump pitch of flip-chip on the filling efficiency was demonstrated to provide insight for flip-chip design optimization. Design/methodology/approach The filling efficiency was formulated analytically based on the conceptual spatial and temporal perspectives. Subsequently, the effect of bump pitch on filling efficiency was studied based on the past actual-scaled and current scaled-up underfill experiments. The latter scaled-up experiment was validated with both the finite volume method-based numerical simulation and analytical filling time model. Moreover, the scaling validity of scaled-up experiment was justified based on the similarity analysis of dimensionless number. Findings Through the scaling analysis, the current scaled-up experimental system is justified to be valid since the adopted scaling factor 40 is less than the theoretical scaling limit of 270. Furthermore, the current experiment was qualitatively well validated with the numerical simulation and analytical filling time model. It is found that the filling efficiency increases with the bump pitch, such that doubling the bump pitch would triple the efficiency. Practical implications The new performance indicative index of filling efficiency enables the package designers to justify the variation effect of underfill parameter on the overall underfill process. Moreover, the upper limit of scaling factor for scaled-up package was derived to serve as the guideline for future scaled-up underfill experiments. Originality/value The performance of underfill process as highlighted in this paper was never being quantified before in the past literatures. Similarly, the scaling limit that is associated to the scaled-up underfill experiment was never being reported elsewhere too.

The wetting formation and nanoparticles dispersion on adding nanoparticles to the lead free solder Sn-3.0Ag-0.5Cu (SAC305) is methodically investigated using Discrete Phase Model (DPM) simulation and applied on a 01005 capacitor component. Different types of nanoparticles, namely titanium dioxide (TiO2), nickle oxide (NiO) and Iron (III) oxide (Fe2O3) with varying weight percentages, 0.01wt%, 0.05wt% and 0.15wt% that is doped in SAC305 are used. The study of two-way interactions between multiphase volume of fluid (VOF) and discrete phase model (DPM) shows excellent capability in tracking the dispersed nanoparticles immersed in the wetted molten solder. In this study, real reflow profile temperature setup will be used to mimic the conventional reflow process. Based on the findings, the fillet height managed to achieve the minimum required height set by IPC standards. As the concentration of the nanoparticles doped in the molten solder increases, higher time is required for the wetting process. In general, the doped NiO nanoparticles at 0.05wt% has the lowest wetting time compared to other cases. The study of the instantaneous nanoparticles trajectory tracking was also conducted on a 3D model and 2D cross sectional view to identify the exact movement of the particles. Additionally, it was also observed that the velocity and pressure distribution increases as the weight percentage of the nanoparticles increases.

Renal artery aneurysm (RAA) is a condition that affects approximately 0.1% of the general population. The rate of incidence is minimal compared to other type of aneurysm but a high number of ruptures have been reported in pregnancy, especially at the third trimester. The concerning issue is that the maternal mortality rate stretches up to 50% and the fetal mortality rate approaching 85% with a universal loss of the affected kidney. This study aimed at investigating the effectiveness of stent in treatment of RAA using the fluid-structure interaction (FSI) approach. The flow pattern, wall shear stress (WSS), deformation and von Mises stress experienced are compared between RAA model without stent and with Abbott RX Herculink stent. A simple PIV experiment, observing the flow profile was conducted as a validation steps in ensuring the simulation results are reliable and accurate. The findings show that the simulation and PIV data are in good agreement in terms of the flow profile. The presence of stent managed to reduce the blood flow maximum velocity down to 46% and minimized the circulation of blood in the aneurysm dome. As for the WSS, the used of stent succeeded in decreasing the WSS experienced by the wall of aneurysm by 71% and below the baseline level of WSS that could induced rupture. The deformation of RAA and maximum von Mises stress reduced by 58% and 73% respectively when stent is used. In addition, the maximum von Mises stress after the stent placement is lower than the threshold value for the ultimate tensile strength of the tissue. This study concluded that the stent placement is effective in reducing the risk of aneurysm rupture in renal artery it can be one of the baseline for the further study regarding the RAA.

This paper studies the three-dimensional simulation of pressurized underfill process for I-type dispensing method on a ten-by-ten, middle empty ball grid array (BGA) using lattice Boltzmann method. Pressurized underfill process is introduced to overcome the drawbacks of capillary underfill process that includes incomplete filling, void formation and extended filling time. The effects of capillary and pressurized underfill methods of BGA encapsulation process on the flow front, filling time and pressure of the fluid are investigated. Four different pressure values are used as the input pressure in the lattice Boltzmann simulation. Experiments are carried out as well to validate the simulation results. In general, pressurized underfill method results in a dramatically shorter filling time compared to capillary underfill. The flow front obtained from both simulation and experimental results is quite similar for the BGA model studied. The pressure inside the flow domain is significantly higher than its inlet pressure and thus, caution needs to be taken by the design engineer such that the printed circuit board (PCB) and flip chip are capable to withstand this pressure to prevent from the occurrence of breakage.

Binary biofuel has a relatively higher viscosity compared to conventional diesel, which affects the spray injection and restricts the maximum evaporation. In this paper, the discrete phase model (D...

The stress concentration and deformation of the 3D stacked IC structures can be minimized with an optimal design of the integrated circuit (IC) using a response surface methodology. The geometrical and process parameters (i.e., A = inlet pressure, B = solder bump standoff height, C = chip thickness, and D = aspect ratio) were optimized via a central composite design (CCD) for the molded encapsulation process. The fluid/structure interaction (FSI) aspects were considered in the optimization of the molded encapsulation process. The separate effects of the independent variables and their interactions were studied. The calculated empirical models were carried out and well validated with the simulation results. The optimum geometrical and process parameters of the 3D stacked IC package with perimeter solder bump arrangement were characterized as follows: inlet condition of 3.65 MPa, 150 μm of solder bump standoff height, 250 μm of chip thickness, and 2.1 of aspect ratio. The outcomes herein may significantly contribute to the advancement of microelectronic industries.

Purpose This study aims to investigate the NiO nano-reinforced solder joint characteristics of ultra-fine electronic package. Design/methodology/approach Lead-free Sn-Ag-Cu (SAC) solder paste was mixed with various percentages of NiO nanoparticles to prepare the new form of nano-reinforced solder paste. The solder paste was applied to assemble the ultra-fine capacitor using the reflow soldering process. A focussed ion beam, high resolution transmission electron microscopy system equipped with energy dispersive X-ray spectroscopy (EDS) was used in this study. In addition, X-ray inspection system, field emission scanning electron microscopy coupled with EDS, X-ray photoelectron spectroscopy (XPS) and nanoindenter were used to analyse the solder void, microstructure, hardness and fillet height of the solder joint. Findings The experimental results revealed that the highest fillet height was obtained with the content of 0.01 Wt.% of nano-reinforced NiO, which fulfilled the reliability requirements of the international IPC standard. However, the presence of the NiO in the lead-free solder paste only slightly influenced the changes of the intermetallic layer with the increment of weighted percentage. Moreover, the simulation method was applied to observe the distribution of NiO nanoparticles in the solder joint. Originality/value The findings are expected to provide a profound understanding of nano-reinforced solder joint’s characteristics of the ultra-fine package.

This study presents experimental and numerical works on porous media burner. The influence of ultra-low vegetable oil droplets on burner performance was investigated. A unique dual-layer microporous media burner was fabricated to generate surface and submerged flames under lean conditions. Optimum equivalence ratio under lean conditions for surface and submerged flames was recorded at 0.7 and 0.5, respectively. The performance of the burner was examined by adding vegetable oil droplets of 20, 40, 60, or 80 $$\upmu \hbox {L}$$ externally on the surface of reaction layer. At 80 $$\upmu \hbox {L}$$ , the burner was at its best performance, while $$>80 ~\upmu \hbox {L}$$ leads to unstable flames. The maximum thermal efficiency of the burner under surface flame without droplets was found out to be 90%, which was enhanced to 94% by enabling 80 $$\upmu \hbox {L}$$ of vegetable oil. Similarly, with submerged flame maximum thermal efficiency progressively improved from 38 to 45%. The impact of vegetable oil at the microscopic level was determined by performing scanning electron microscopy and X-ray diffraction analysis. Digital thermal images were captured at critical ER to ensure a stable combustion. The emitted combustion gases were monitored continuously to detect the emissions (NOx and CO). These emissions were within controlled limits. Finally, three-dimensional numerical study was performed to effectively comprehend the experimental data for both temperature and emissions.

The conventional capillary underfill process has been a common practice in the industry, somehow the process is costly and time-consuming. Thus, no-flow underfill process is developed to increase the effective lead time production since it integrates the simultaneous reflow and cure of the solder interconnect and underfill. This paper investigates the effect of different dispense patterns of no-flow underfill process by mean of numerical and experimental method. Finite volume method (FVM) was used for the three-dimensional (3D) simulation to simulate the compression flow of the no-flow underfill. Experiments were carried out to complement the simulation validity and the results from both studies have reached a good agreement. The findings show that of all three types of dispense patterns, the combined shape dispense pattern shows better chip filling capability. The dot pattern has the highest velocity and pressure distribution with values of 0.0172 m/s and 813 Pa, respectively. The high-pressure region is concentrated at the center of the chip and decreases out toward the edge. Low in pressure and velocity flow factor somehow lead to issue associated with possibility of incomplete filling or void formation. Dot dispense pattern shows less void formation since it produces high-pressure underfill flow within the ball grid array (BGA). This paper provides reliable insight into the industry to choose the best dispense pattern of recently favorable no-flow underfill process.

This paper analyses the variation of water level height in scaled down physical model of Chenderoh spillway and velocity through the spillway is measured. As a part of the physical model design process, a 3D model drawing of 1:20 scaled of spillway has been drawn based on basic scale ratios. Froude number is used for scalling down method as it is more relevant in this study compared to Reynold number. Spillway physical model then been operated with five different water levels. It shows that the height of water level would affect the velocity proportional with the flow rate of water. The highest velocity in this study is 0.6667m/s with 0.11m water level height. Based on the results, the higher the water level, the higher the velocity of water through the spillway.

Frequency response function (FRF) and modal parameters including the natural frequency, damping ratio and mode shapes need to be studied in order to aid the monitoring process as well as to avoid the resonance to the structure. This is important since these measurements will be used as reference for any operational methods for the dam structure. This paper will discuss the structural dynamic analysis of one of the dam available in Malaysia which is Kenyir Dam (Sultan Mahmud Power Station) in Terengganu. The study has been conducted on the spillway section of the dam structure. The CAD model of the structure has been designed based on real size structure (1:1 scale) with the consideration of real build-in materials. A finite element (FE) model of the structure is then constructed in ANSYS Workbench software to run the analysis. Meshing sensitivity analysis has been conducted and the boundary condition has been set before performing the analysis. 30 natural frequencies have been determined and 6 most significant mode shapes are chosen to be discussed in this paper. For the FRF, all three axes, x, y and z-direction have the same dominant natural frequency value of 19.6 Hz, where the highest deflection occurred at z-direction with 6.795 x 10−4 m.

Understanding the nature of the vortex formation is important to research that needs to be cover in order to develop a mitigation plan to avoid or reduce its formation that may cause serious damage to the hydropower mechanical machines. This paper presents a review of significant cases of vortex formation in the hydraulic intake that has been adopted Particle Image Velocimetry (PIV) as a method of the research. The focus of this review is to provide a solid basis for the efficiency of the PIV measurement to study the vortex formation in the hydraulic intake. As a new innovative approach to the vortex study, it stated that PIV is a method that able to find a good agreement and can be validated together with another method.

This study assesses the structural analysis on the sector gate in dam spillway with 5 m gap opening. The parameters determined on this study are equivalent stress and total deformation. The structure analysis on the spillway structure is due to the impact of water discharge. Computational fluid dynamic (CFD) modelling is applied to assess the water flow that affect stress and deformation occurred using computational aided program using ANSYS. Result of the transient structure model show that the highest stress value is at the radial gate which is 29.69 MPa and the lowest stress value is at stilling basin which is 0.037 x 10−9 MPa. All the deformation values are relatively low especially at the stilling basin which is 1.021 x 10−9 m and the largest deformation value is at the radial gate which is 10.47 x 10-6 m. It can be concluded that the stress and deformation give different result due to different materials. Stress and deformation values at mild steel material parts are higher than concrete material parts due to the high impact of water pressure. Future mitigation measures have to take to ensure the sustainability of the structural integrity.

Water is the natural resources uses for multi-functional for human purpose. Water reservoir the main structure to supply and distribute water to the communities. According ICOLD world water storage decrease cause of sedimentation. Sedimentation also can damage the structure reservoir and dam. This study was develop to control sedimentation activities by remove away sediment before deposition occur. Siphon model was fabricated in scale 1:40 using 3D printing. Retention wall with dimension 0.49m x 0.46m was install using silicone inside the flume. Two trapping filter with dimension 0.49m x 0.46m had been install using silicone inside the flume in front of siphon outlet to protect the pump from damage. The siphon operation using different water level 0.41m to 0.40m, 0.40m to 0.39m, 0.39m to 0.38m and 0.38m to 0.37m. Sandy silt was use for sediment materials. The sandy silt fill into the rectangular made plywood block with two bar iron use with dimension 1m x 0.49m x 0.08m to block sediment distribute out from siphon inlet when the flume fill in with the water. The pressure manometer tube had been located at siphon in let. The ideal water level for highest siphon performance on water level 0.40m to 0.39m with the highest amount sediment suction 1185g. The lowest pressure 470pa. Type of topography contour at suction inlet of siphon had been observe and identified.

The key feature of the bi-leaflet valve is the geometry of the two leaflets, which can be crucial in determining the flow field. In this paper, observations were made on the flow pattern of the blood through the use of bi-leaflet type mechanical prosthetic valve (MHV). Finite volume method (FVM) analysis was conducted using fluid-structure interaction (FSI) method that solved on a dynamic mesh. In terms of the validation, particle image velocimetry (PIV) was used to verify the findings obtained from FVM analysis. The results of velocity and vorticity were the main parameters to be compared. Based on the findings, the results computed for the leaflets motion and the flow field using FVM was found to be in agreement with PIV experimental data. The pressure obtained for the simulation is in the range of 10,666 – 16,000 Pa, which is an ideal and healthy blood pressure level of human. The vorticity was observed to be formed behind the valve with DVI value of 1.275 (simulation) and 1.457 (experiment), lower than the expected range for a normal DVI in mitral valve. The maximum shear stress achieved (22.5481 Pa) is in the range of platelets activation, which could lead to thrombus formation. The maximum Von Mises stress was found to be at the hinge region of the bi-leaflet valve. These results will serve as a basis for valve design to improve the hemodynamic properties of the heart valve.

Purpose This paper aims to investigate the characteristics of ultra-fine lead-free solder joints reinforced with TiO2 nanoparticles in an electronic assembly. Design/methodology/approach This study focused on the microstructure and quality of solder joints. Various percentages of TiO2 nanoparticles were mixed with a lead-free Sn-3.5Ag-0.7Cu solder paste. This new form of nano-reinforced lead-free solder paste was used to assemble a miniature package consisting of an ultra-fine capacitor on a printed circuit board by means of a reflow soldering process. The microstructure and the fillet height were investigated using a focused ion beam, a high-resolution transmission electron microscope system equipped with an energy dispersive X-ray spectrometer (EDS), and a field emission scanning electron microscope coupled with an EDS and X-ray diffraction machine. Findings The experimental results revealed that the intermetallic compound with the lowest thickness was produced by the nano-reinforced solder with a TiO2 content of 0.05 Wt.%. Increasing the TiO2 content to 0.15 Wt.% led to an improvement in the fillet height. The characteristics of the solder joint fulfilled the reliability requirements of the IPC standards. Practical implications This study provides engineers with a profound understanding of the characteristics of ultra-fine nano-reinforced solder joint packages in the microelectronics industry. Originality/value The findings are expected to provide proper guidelines and references with regard to the manufacture of miniaturized electronic packages. This study also explored the effects of TiO2 on the microstructure and the fillet height of ultra-fine capacitors.

Consistent with the recent trends in which the flip-chip reliability and performance being prominently prioritized, this paper is devoted to study the effects of solder bump shapes on the capillary underfill flows during the flip-chip encapsulation. A new experimental approach based on the particle image velocimetry (PIV) is set-up to visualize the underfill flow in the flip-chip. A more generalized analytical model for predicting the underfill filling time was developed to be applied for the triple-inlets dispensing (U-shape) underfill process with its application extended to a more generic bump shape. The theoretical analysis based on averaging method has been found viable for prediction of the underfill pressure, velocity and permeability. Findings from both finite volume method (FVM) simulation and PIV experiment achieved great consensus and are in line with the new theoretical estimates. These three distinct methodologies independently concluded the direct impact of different bump shapes design on the underfill flow. Altering the truncated spherical-shaped bump into a narrow-neck bump, for instance hourglass and concave shapes, would respectively reduce the filling times by 8.86% and 11.4% respectively; apart from having the increase in flow pressure and velocity. The mean permeability of the bump array computed is observed to be in an increasing order starting from spherical, cylindrical, hourglass and concave shapes. Generally, this comprehensive study had identified the geometrical parameters of solder bump that necessitated for faster underfill flow, being low sphericity and high pad-to-neck ratio.

This paper presents the influence of Fe2O3 nanoparticles on the microstructure and fillet height for the ultra-fine electronics assembly in the reflow soldering process. Lead-free SAC solder paste was reinforced with different weighted percentages of Fe2O3 nanoparticles (i.e., 0.01, 0.05, and 0.15 wt.%) using a mechanical solder paste mixer. A new form of nano-reinforced lead-free solder paste was applied to assemble the ultra-fine capacitor (i.e., 01005 size) onto the printed circuit board by applying the reflow soldering method. Focused ion beam (FIB), high-resolution transmission electron microscope (HRTEM) system equipped with energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS), and nanoindentation tester, were all used to examine the microstructure, hardness, and the fillet height of the solder joints. The experimental results revealed that nano-reinforced solder with the content of 0.01, 0.05, and 0.05 wt% yielded small changes in the intermetallic layers. Furthermore, applying an increment of Fe2O3 to 0.05 wt% also improved the fillet height. The mechanism of the agglomeration of Fe2O3 in the bulk solder is discussed in this study. Moreover, simulation analysis using the volume of fluid (VOF) and discrete phase method (DPM) was both employed to describe the mechanism of nanoparticle distribution in the solder and the reflow soldering process. The findings are expected to provide profound knowledge and further reference towards the reflow soldering process of the miniaturised electronic package.