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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.

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.

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%.

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.

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.

This paper focuses on the reliability of the solder joint after the self-alignment phenomenon during reflow soldering. The aim of this study is to analyse the joint quality of the self-alignment assemblies of SnAg alloy solder joints with varying silver content.

The shear strength assessment was conducted in accordance with the JIS Z3 198-7 standard. The standard visual inspection of IPC-A-610G was also performed to inspect the self-alignment features of the solder joint samples. Statistical analysis was conducted to determine the probabilistic relationship of shear strength of the misalignment components.

The results from the mechanical reliability study indicate that there were decreasing trends in the shear strength value as misalignment offset increased. For shift mode configuration in the range of 0-300 µm, the resulting chip assembly inspection after the reflow process was in line with the IPC-A-610G standard. The statistical analysis shows that the solder type variation was insignificant to the shear strength of the chip resistor. The study concluded that the fracture occurred partially in the termination metallization at the lower part of the chip resistor. The copper content of the joint on that area shows that the crack occurred in the solder joint, and high silver content on the selected zone indicated that the fracture happened partially in the termination structure, as the termination structure of the lead-free chip resistor consists of an inner layer of silver and an outer layer of tin.

This study’s findings provide valuable guidelines and references to engineers and integrated circuit designers during the reflow soldering process in the microelectronics industry.

Studies on the effect of component misalignment on joint mechanical reliability are still limited, and studies on solder joint reliability involving the effect of differing contents of silver on varying chip component offset are rarely reported. Thus, this study is important to effectively bridge the research gap and yield appropriate guidelines in the potential industry.

The purpose of this paper is to present the experimental and simulation studies on the influence of copper pillar bump structure on flip chip packaging during reflow soldering.

In this work, solidification/melting modelling and volume of fluid modelling were used. Reflow soldering process of Cu pillar type FC was modelled using computational fluid dynamic software (FLUENT). The experimental results have been validated with the simulation results to prove the accuracy of the numerical method.

The findings of this study reveal that solder volume is the most important element influencing reflow soldering. The solder cap volume reduces as the Cu pillar bump diameter lowers, making the reflow process more difficult to establish a good solder union, as less solder is allowed to flow. Last but not least, the solder cap height for the reflow process must be optimized to enable proper solder joint formation.

This study provides a basis and insights into the impact of copper pillar bump structure on flip chip packaging during reflow soldering that will be advancing the future design of 3D stack package. This study also provides a superior visualization and knowledge of the melting and solidification phenomenon during the reflow soldering process.

The computational fluid dynamics analysis of copper pillar bump structure on flip chip packaging during reflow soldering is scant. To the authors’ best knowledge, no research has been concentrated on copper pillar bump size configurations in a thorough manner. Without the in-depth study, copper pillar bump size might have the impact of copper pillar bump structure on flip chip packaging during reflow soldering. Five design of parameter of flip chip IC package model was proposed for the investigation of copper pillar bump structure on flip chip packaging during reflow soldering.

The purpose of this study is to investigate the effect of the adhesive force and density ratio using lattice Boltzmann method (LBM) during underfill process.

To deal with complex flow in underfill process, a framework is proposed to improve the lattice Boltzmann equation. The fluid flows with different density ratio and bump arrangement in underfill are simulated by the incorporated Carnahan–Starling (CS) equation of state (EOS). The numerical study conducted by finite volume method (FVM) and experimental results are also presented in each case at the different filling percentage for verification and validation purpose.

The numerical result is compared well with those acquired experimentally. Small discrepancy is detected in their flow profile. It was found that the adhesive force between fluid and solid was affected by the density ratio of the fluids and solder bump configuration. LBM has shown better adhesive force effect phenomenon on underfill process compared to FVM. LBM also demonstrated as a better tool to study the fluid flow in the underfill process.

This study provides a basis and insights into the impact of adhesive force and density ratio to the underfill process that will be advancing the future design of flip chip package. This study also provides superior guidelines, and the knowledge of how adhesive force is affected by flip chip package structure.

This study proposes the method to predict the adhesive force and density ratio effect for underfill flow in flip chip package. In addition, the proposed method has a good performance in representing the adhesive force during the underfill simulation for its natural physical basic. This study develops understanding of flow problems to attain high reliability for electronic assemblies.

The purpose of this study is to investigate heat transfer and deformation of flexible printed circuit board (FPCB) under thermal and flow effects by using fluid structure interaction. This study simulate the electronic cooling process when electronic devices are generating heat during operation at FPCB under force convection.

The thermal and flow effects on FPCB with attached ball grid array (BGA) packages have been investigated in the simulation. Effects of Reynolds number (Re), number of BGA packages attached, power supplied to the BGA packages and size of FPCB were studied. The responses in the present study are the deflection/length of FPCB (δ/L) and Nusselt number (Nu).

It is important to consider both thermal and flow effects at the same time for understanding the characteristic of FPCB attached with BGA under operating condition. Empirical correlation equations of Re, Prandtl number (Pr), δ/L and Nu have been established, in which the highest effect is of Re, followed by Pr and δ/L. The δ/L and Nu¯ were found to be significantly affected by most of the parametric factors.

This study provides a better understanding of the process control in FPCB assembly.

This study provides fundamental guidelines and references for the thermal coupling modelling to address reliability issues in FPCB design. It also increases the understanding of FPCB and BGA joint issues to achieve high reliability in microelectronic design.

This paper aims to improve the generalization capability of feature extraction scheme by introducing a micro-cracks detection method based on self-learning features. Micro-cracks detection of multicrystalline solar cell surface based on machine vision is fast, economical, intelligent and easier for on-line detection. However, the generalization capability of feature extraction scheme adopted by existed methods is limited, which has become an obstacle for further improving the detection accuracy.

A novel micro-cracks detection method based on self-learning features and low-rank matrix recovery is proposed in this paper. First, the input image is preprocessed to suppress the noises and remove the busbars and fingers. Second, a self-learning feature extraction scheme in which the feature extraction templates are changed along with the input image is introduced. Third, the low-rank matrix recovery is applied to the decomposition of self-learning feature matrix for obtaining the preliminary detection result. Fourth, the preliminary detection result is optimized by incorporating the superpixel segmentation. Finally, the optimized result is further fine-tuned by morphological postprocessing.

Comprehensive evaluations are implemented on a data set which includes 120 testing images and corresponding human-annotated ground truth. Specifically, subjective evaluations show that the shape of detected micro-cracks is similar to the ground truth, and objective evaluations demonstrate that the proposed method has a high detection accuracy.

First, a self-learning feature extraction method which has good generalization capability is proposed. Second, the low-rank matrix recovery is combined with superpixel segmentation for locating the defective regions.

Sustainability issues have become crucial to mitigate urban heat islands (UHIs) and reduce the global warming effect. The climate change news is frequently heard lately due to the extreme weather to the extent that the increasing earth’s temperature often causes disaster and loss of property and life. New adaptation needs to new climate context and limits the on-going effects. One of the ways is adopting green roofs on buildings. Implementing sustainable practices such as green roofs will help mitigate this adverse effect in urban areas. Green roofs provide many benefits such as enhancing the aesthetical quality of the built environment, reduce UHIs, reduce energy consumption, improve storm-water attenuation, roof longevity, and reduce noise pollution. However, only a few buildings in Malaysia have considering green roofs as a main green feature element. There is barely number of buildings that have green roof design even though it offers benefits to the community and environment. This chapter has emphasised the types of green roof systems that are potentially suitable in Malaysia climate and obstacles associated with the green roof system. The study found the barriers to implementing green roofs in Malaysia, especially during the stage of building operation in maintaining the green roof system. The survey has been done, which revealed nine factors that hinder the green roof application. This study also highlights the challenges to overcome the barriers of implementing green roofs in Malaysia.

The purpose of the present study was to review the thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components (SMCs). The topics of the review include challenges in modelling of the reflow soldering process, optimization and the future challenges in the reflow soldering process. Besides, the numerical approach of lead-free solder reliability is also discussed.

Lead-free reflow soldering is one of the most significant processes in the development of surface mount technology, especially toward the miniaturization of the advanced SMCs package. The challenges lead to more complex thermal responses when the PCB assembly passes through the reflow oven. The virtual modelling tools facilitate the modelling and simulation of the lead-free reflow process, which provide more data and clear visualization on the particular process.

With the growing trend of computer power and software capability, the multidisciplinary simulation, such as the temperature and thermal stress of lead-free SMCs, under the influenced of a specific process atmosphere can be provided. A simulation modelling technique for the thermal response and flow field prediction of a reflow process is cost-effective and has greatly helped the engineer to eliminate guesswork. Besides, simulated-based optimization methods of the reflow process have gained popularity because of them being economical and have reduced time-consumption, and these provide more information compared to the experimental hardware. The advantages and disadvantages of the simulation modelling in the reflow soldering process are also briefly discussed.

This literature review provides the engineers and researchers with a profound understanding of the thermo-mechanical challenges of reflowed lead-free solder joints in SMCs and the challenges of simulation modelling in the reflow process.

The unique challenges in solder joint reliability, and direction of future research in reflow process were identified to clarify the solutions to solve lead-free reliability issues in the electronics manufacturing industry.

The purpose of this paper is to present a three-dimensional finite volume-based analysis on the effects of propeller blades on fountain flow in a wave soldering process and performs an experimental validation.

Solder pot models with various numbers of propeller blades were developed and meshed by using hybrid elements and simulated by using the FLUENT fluid flow solver. The characteristics of the fountain, such as flow profile, velocity vector, filling time, and fountain advancement, were investigated. Molten solder (Sn63Pb37) material, a temperature of 250°C, and a propeller speed of 830 rpm were applied in the simulation. The predicted results were validated by the experimental fountain profile.

The use of a six-blade propeller in a solder pot increased the fountain thickness profile and reduced the filling time. Moreover, a six-blade propeller design resulted in a stable fountain profile and was considered the best choice for current wave soldering processes.

This study provides a better understanding of the effects of propeller blades on the fountain flow in the wave soldering process.

The study explores the fountain flow behavior and provides a reference to the engineers and designers in order to improve the fountain flow of the wave soldering.

The purpose of this research is to investigate the relationship between leadership and the party’s image and voters’ satisfaction and voters’ loyalty in the regional election of the North Konawe District, Indonesia.

The study design is quantitative methods (Creswell, 2010). It is an explanatory research, investigating the relationship between variables (Kothari, 2004). The study population was the voters who participated in the 2015 regional head election of North Konawe. The population in this study was 37,429 people spread over 12 districts and 135 villages, and the sample size of this study was 276 respondents, based on sample size formulation in (Bungin, 2008). The method used to analyze the data in this study is generalized structured component analysis (GSCA), which investigate comprehensively the inner model (hypothesis testing for the structural model) and the outer model (measurement model for unobservable variables). The Sobel test (under the GSCA model) was used to test whether a particular variable mediates the relationship between endogenous variables and exogenous variables.

The party’s image influences voters’ satisfaction. The party’s image will not directly influence voters’ loyalty, but it will influence voters’ loyalty with the mediating effect of voters’ satisfaction.

The findings of this study that makes the social security program as one of the themes in the competition reinforces previous studies such as in the Philippines, Thailand, Mexico and Brazil (2012). Various jargons are often thrown around to gain votes and support from the poor. For example, the term “populist economy”, where free public health and education services are often declared in various political campaigns, both in the legislative member and regional head elections.

The results of this research, i.e. the influence of the party’s image for electoral interests, would reinforce the results of previous studies. Sometimes the politicians use the poverty program, which is apparently neutral, but actually for the sake of political interests (Gallego, 2015). The results of this study show that the manipulation of government programs is often done to help the politicians in mobilizing the voters. However, in practices, the voters? satisfaction and loyalty are interpreted differently. The voters do not always sell their votes because of what they receive; it could be that the voters receive the assistance by considering it as a fortune or wage in return for helping the politicians. It was proved by the results of this study that the incumbent lost the election.

Using the party’s image in a political contest has created serious implications in the development of democracy in Indonesia. Indonesia, which has chosen democracy as a political route, is still highly vulnerable to clientelistic practices. Although procedurally Indonesia has paved the main democratic consolidation after the reform, ranging from the legislative election to the presidential election to the regional head election, the practice of money politics is still occurring widely. The problem of vote-buying is more difficult to solve because law enforcement mechanisms are not conducted properly. For example, only three days were given to prove the allegation of vote-buying. Of course, this short time makes it difficult to prove the practice of money politics at lower levels.

The originality of this research can be seen from the following explanation: based on the results of data processing, there are interesting things observed, with the party’s image as the exogenous variable, voters’ satisfaction as the intervening endogenous variable and voters’ loyalty as the pure endogenous variable. This means that more and more community empowerment will increase the desirability of a candidate. This is unique in itself, where with this result, it can be concluded that North Konawe communities are more affected by the nature of the aid empowerment, durable and sustainable/long-term rather than momentary relief (cash).