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1 – 10 of 221
Article
Publication date: 18 December 2018

Flavia V. Barbosa, José C.F. Teixeira, Senhorinha F.C.F. Teixeira, Rui A.M.M. Lima, Delfim F. Soares and Diana M.D. Pinho

The aim of this paper is to characterize the rheological properties of the flux media exposed to different levels of solicitation and to determine its influence on the…

Abstract

Purpose

The aim of this paper is to characterize the rheological properties of the flux media exposed to different levels of solicitation and to determine its influence on the rheology of the solder paste. The data obtained experimentally are fundamental for the development of numerical models that allow the simulation of the printing process of printed circuit boards (PCB).

Design/methodology/approach

Rheological tests were performed using the Malvern rheometer Bohlin CVO. These experiments consist of the analysis of the viscosity, yield stress, thixotropy, elastic and viscous properties through oscillatory tests and the capacity to recover using a creep-recovery experiment. The results obtained from this rheological analysis are compared with the rheological properties of the solder paste F620.

Findings

The results have shown that the flux is viscoelastic in nature and shear thinning. The viscosity does not decrease with increasing solicitations, except in the case where the flow is withdrawn directly from the bottle. Even if the solder paste shows a thixotropic behavior, this is not the case of the flux, meaning that this property is given by the metal particles. Furthermore, the oscillatory tests proved that the flux presents a dominant solid-like behavior, higher than the solder paste, meaning that the cohesive/tacky behavior of the solder paste is given by the flux.

Research limitations/implications

To complement this work, printing tests are required.

Originality/value

This work demonstrates the importance of the rheological characterization of the flux in order to understand its influence in the solder paste performance during the stencil printing process.

Details

Soldering & Surface Mount Technology, vol. 31 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 21 September 2010

S. Mallik, M. Schmidt, R. Bauer and N.N. Ekere

The purpose of this paper is to study the rheological behaviours of lead‐free solder pastes used for flip‐chip assembly applications and to correlate rheological…

Abstract

Purpose

The purpose of this paper is to study the rheological behaviours of lead‐free solder pastes used for flip‐chip assembly applications and to correlate rheological behaviours with the printing performance.

Design/methodology/approach

A range of rheological characterization techniques including viscosity, yield stress, oscillatory and creep‐recovery tests were carried out to investigate the rheological properties and behaviours of four different solder paste formulations based on no‐clean flux composition, with different alloy composition, metal content and particle size. A series of printing tests were also conducted to correlate printing performance.

Findings

The results show that in the viscosity test, all solder pastes exhibited a shear thinning behaviour in nature with different highest maximum viscosity. The yield stress test has been used to study the effect of temperature on the flow behaviour of solder pastes. A decrease in yield stress value with temperature was observed. The results from the oscillatory test were used to study the solid‐ and liquid‐like behaviours of solder pastes. Creep‐recovery testing showed that the solder paste with smaller particle size exhibited less recovery.

Research limitations/implications

More extensive research is needed to simulate the paste‐roll, aperture‐filling and aperture‐emptying stages of the stencil printing process using rheological test methods.

Practical implications

Implementation of these rheological characterization procedures in product development, process optimization and quality control can contribute significantly to reducing defects in the assembly of flip‐chip devices and subsequently increasing the production yield.

Originality/value

The paper shows how the viscosity, yield stress, oscillatory and creep‐recovery test methods can be successfully used to characterize the flow behaviour of solder pastes and also to predict their performance during the stencil printing process.

Details

Soldering & Surface Mount Technology, vol. 22 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 6 February 2017

Oliver Krammer, Benjámin Gyarmati, András Szilágyi, Richárd Storcz, László Jakab, Balázs Illés, Attila Géczy and Karel Dušek

A measurement method has been developed to reveal the viscosity change of solder pastes during stencil printing. This paper aimed to investigate thixotropic behaviour, the…

Abstract

Purpose

A measurement method has been developed to reveal the viscosity change of solder pastes during stencil printing. This paper aimed to investigate thixotropic behaviour, the viscosity change of a lead-free solder paste (Type 4).

Design/methodology/approach

The viscosity change of the solder paste during stencil printing cycles was characterised in such a way that the time-gap between the printing cycles was modelled with a rest period between every rheological measurement. This period was set as 15, 30 and 60 s during the research. The Cross model was fitted to the measurement results, and the η0 parameter was used to characterise the viscosity change. The number of printing cycles necessary for reaching a stationary state in viscosity was determined for various rest periods.

Findings

It was found that the decrease in zero-shear viscosity is significant (25 per cent) in the first cycles, and it starts to become stationary at the sixth-seventh cycles. This means a printing process can provide the appropriate deposits only after the 7th cycle with the investigated Type 4 solder paste.

Originality/value

Time-dependent rheological behaviour of solder pastes was studied in the literature, but only the viscosity change over continuous time at constant shear rates was examined. The time-gap between stencil printing cycles was not considered, and thixotropic behaviour of solder pastes was also neglected. Therefore, the authors developed a measurement set which is able to model the effect of time-gap between printing cycles on the viscosity change of solder pastes.

Details

Soldering & Surface Mount Technology, vol. 29 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 12 April 2011

A.E. Marks, N.N. Ekere, S. Mallik and R. Bhatti

The purpose of this paper is to investigate how the formulation of a solder paste (with regards to the flux and particle size distribution (PSD)), can influence its creep…

Abstract

Purpose

The purpose of this paper is to investigate how the formulation of a solder paste (with regards to the flux and particle size distribution (PSD)), can influence its creep and recovery performance.

Design/methodology/approach

New lead‐free paste formulations were characterised utilising viscometry and oscillatory methods, after which creep/recovery investigations were conducted to determine the recovery performance. Measurements were recorded using a rheometer with a parallel plate geometry of 40 mm and a sample height of 1 mm.

Findings

Results from the study highlighted that the formulation of a solder paste can have a significant impact on the creep/recovery measurements. Variations in flux and PSD highlighted a considerable difference in the recoverability of the solder pastes, in one instance demonstrating more than a 20 per cent increase in structural recovery.

Research limitations/implications

More extensive research is needed relating to reduced PSDs, such as type 6 and 7 solder pastes, to fully understand their influence on the creep/recovery performance.

Practical implications

The results presented in this paper emphasise important information and investigational methods for research and development, and quality control.

Originality/value

The paper highlights how the composition of new paste formulations can influence the creep/recovery behaviour. It was found that the recoverability can be increased by careful selection of the flux and PSD, which in turn could reduce slumping influences in the print process. If used as a quality control tool, this paper may allow for the reduction in print defect occurrence.

Details

Soldering & Surface Mount Technology, vol. 23 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 21 June 2013

Won‐Sang Seo and Jong‐Bong Kim

The purpose of this paper is to suggest an analysis methodology for the stencil printing process and to obtain proper design parameters that guarantee the successful…

Abstract

Purpose

The purpose of this paper is to suggest an analysis methodology for the stencil printing process and to obtain proper design parameters that guarantee the successful filling using suggested finite element analyses.

Design/methodology/approach

Filling performance of solder paste in the stencil printing process is highly dependent on material properties such as viscosity and surface tension together with process parameters such as squeegee angle and squeegee speed. In order to investigate the effects of process parameters on the filling performance, the pressure built‐up under the squeegee and the filling procedure of the solder paste into an aperture were analysed. Due to the limitations of the computational memory and time, the analysis domain was simplified. The pressure development under the squeegee was investigated for various values of squeegee angle and speed; then, the filling behaviour with the pressure boundary condition was analysed for only one aperture. Finally, the two analysis results were integrated to obtain the successful filling condition. In this analysis method, process parameters that guarantee filling performance were decided on.

Findings

It was shown that higher squeezing pressure develops as the squeegee angle decreases and the squeegee speed increases. The filling performance, however, improves as the squeegee angle and the squeegee speed decrease. This is because the pressure duration time decreases as the squeegee speed increases.

Originality/value

This study suggests a new design approach to obtain proper process design parameters for successful filling of solder paste into an aperture. The direct analysis of filling with squeegee movement is impossible due to limitations of computer memory and computation time. To overcome these limitations, a two steps analysis approach is proposed and can be effectively applied in the design of stencil screen printing.

Details

Soldering & Surface Mount Technology, vol. 25 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 14 February 2022

Erdem Ilten

In recent years, use of sensorless control methods for electrical motor-based variable speed drive systems has been increasing rapidly to compensate the increasing costs…

Abstract

Purpose

In recent years, use of sensorless control methods for electrical motor-based variable speed drive systems has been increasing rapidly to compensate the increasing costs in industrial systems. Also, use of induction motors is popular for a long time to decrease the cost of these industrial systems. This study aims to design an effective controller to improve the sensorless speed control performance of induction motor. To achieve this, a conformable fractional order proportional integral (CFOPI) controller is designed.

Design/methodology/approach

The system is modeled based on small signal analysis by using the input–output data, experimentally. To do this, system identification toolbox of Matlab is used. The proposed controller is established on conformable fractional integral approach proposed by Khalil et al. (2014). CFOPI controller coefficients are optimized using particle swarm optimization method on the created small signal-based simulation model of the system to minimize the integral time absolute error. To prove the success of the proposed method, a traditional fractional order proportional integral (TFOPI) controller is tested under the same experimental system with the CFOPI controller.

Findings

TFOPI and CFOPI controllers are tested with the optimum parameters. Reference and actual speed trends are obtained for both methods. In induction motor start-up test, settling-times are measured as 8.73 and 8.44 s and steady-state oscillations are 2.66% and 0% (almost) for TFOPI and CFOPI controllers, respectively. In variable referenced speed tracking test, CFOPI performs well at all speed levels, while TFOPI fails to reach the reference speed at most speed levels.

Practical implications

Proposed CFOPI control method can be easily implemented in industrial systems, thanks to its simple algorithm. digital signal peripheral interface controller (dsPIC) based driver circuit with designed CFOPI controller used in this study can be applied directly to industrial systems such as elevators, conveyors, cranes and drills. Moreover, it can improve the performance of induction motor-based variable speed drive systems.

Originality/value

The proposed method provides robust performance for induction motor used in control systems. Additionally, it does this by using less complex algorithm written on the processors according to the traditional fractional order controllers.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 41 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 31 May 2019

Tareq I. Al-Ma’aiteh and Oliver Krammer

The purpose of this paper is to present the establishment of a computational fluid dynamics model for investigating different non-Newtonian rheological models of solder…

Abstract

Purpose

The purpose of this paper is to present the establishment of a computational fluid dynamics model for investigating different non-Newtonian rheological models of solder pastes by simulating solder paste viscosity measurement. A combined material model was established which can follow the measured, apparent viscosity values with lower error.

Design/methodology/approach

The model included a parallel plate arrangement of rheometers. The diameter of the plate was 50 mm, whereas the gap between the plates was 0.5 mm. Only one quarter of the plate was modelled to enable using fine enough mesh, while keeping the calculation time low. Non-Newtonian properties were set using user defined function in Ansys, based on the Cross and Carreau–Yasuda material models. The viscosity values predicted by the mathematical models were compared to measured viscosity values of different types of solder pastes.

Findings

It was found that the Cross model predicts the apparent viscosity with a relatively high error (even approximately 50 per cent) at lower shear rates, whereas the Carerau–Yasuda model has higher errors at higher shear rates. The application of the proposed, combined model can result in a much lower error in the apparent viscosity between the calculated and measured viscosity values.

Originality/value

The error of Cross and Carreau–Yasuda material models has not been investigated yet in details. The proposed, combined material model can be applied for subsequent simulations via the described UDF, e.g. in the numerical modelling of the stencil printing. This can result in a more accurate modelling of the stencil printing process, which is inevitable considering the printing of solder paste for today fine-pitch, small size components.

Details

Soldering & Surface Mount Technology, vol. 31 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 31 January 2022

Sarat Kumar Jena

Many e-commerce firms suffer from high returns because of inaccurate and incomplete product information. Omnichannel and bundling settings can help firms improve…

Abstract

Purpose

Many e-commerce firms suffer from high returns because of inaccurate and incomplete product information. Omnichannel and bundling settings can help firms improve operational efficiency and lower returns costs. However, no studies have been conducted on omnichannel supply chains considering bundling strategies. The purpose of this study is to examine the comparison between test-in-store-and-buy-online (TSBO) and online retail, comparing manufacturers’ bundling with retailers’ bundling.

Design/methodology/approach

The supply chain discussed here consists of two competitive manufacturers and one retailer. The retailer sells both manufacturers' products online and displays one manufacturer's product in a showroom who bears the display cost. Stackelberg game theory is used to develop mathematical models that help manufacturers and retailers make the most effective decisions. Here, the manufacturer is the Stackelberg leader, while the retailer is the follower. Using the backward induction approach, the authors determined the optimal values for selling price, wholesale price and service effort level.

Findings

The results show that the total TSBO retailing profit under manufacturer bundling is highest when the second manufacturer integrates with the online retailer. The result additionally establishes that when the bundling cost exceeds a certain threshold (1.5), the total profit is higher for the non-integrated type of supply chain channel as compared to the integrated retailer bundling-based configuration.

Practical implications

The operations and logistics manager will likely undertake the TSBO omnichannel strategy during manufacturers bundling and retailer bundling under the integrated strategy.

Originality/value

The main contribution of the study is to examine the effect of TSBO retailing on supply chains profit and individual decision-making under different bundling strategies. The authors developed different mathematical models in the TSBO retailing and bundling context and extended the earlier work in the area of integration frame.

Details

Journal of Business & Industrial Marketing, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0885-8624

Keywords

Article
Publication date: 25 March 2022

Kamlesh Singh, Gaurav Saxena and Mandeep Mahendru

This study aims to examine the lay notions of happiness and determine the factors that influence one’s experience of happiness.

Abstract

Purpose

This study aims to examine the lay notions of happiness and determine the factors that influence one’s experience of happiness.

Design/methodology/approach

This study used a qualitative technique to understand better how happiness is conceptualised. This study uses a purposive sample to select a diverse and representative sample (N = 357). Participants responded to an open-ended questionnaire designed to elucidate their understanding of happiness. The data is analysed using grounded theory and a bottom-up approach.

Findings

Happiness is defined as a harmonious state where the individual’s physiological and psychological needs are satisfied in the past, present and future, leading them to live a meaningful and contented life. However, several factors may affect an individual’s level of happiness. Family and friends; health and wellness; personal and professional successes; recreation and personal traits all contributed to the feeling of happiness. On the other hand, factors impeding happiness include unfavourable surroundings, work and play impediments, strained relationships and undesirable behavioural characteristics. The authors compare and contrast these findings to the current empirical literature and hypotheses.

Originality/value

Despite the substantial study, no uniform definition of happiness exists. The existing body of knowledge is dominated by western viewpoints, which are not necessarily congruent with their eastern counterparts. This study presents a thorough and culturally unique understanding of happiness. This understanding would enable academics, policymakers and educators to develop successful policies that promote happiness. Additionally, this study aid future researchers to develop new measures that enable cross-regional and cross-national comparisons of happiness dynamics

Details

International Journal of Ethics and Systems, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2514-9369

Keywords

Article
Publication date: 4 April 2016

Chun Sean Lau, C.Y. Khor, D. Soares, J.C. Teixeira and M.Z. Abdullah

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Practical implications

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.

Originality/value

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.

Details

Soldering & Surface Mount Technology, vol. 28 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

1 – 10 of 221