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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 behaviours

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

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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

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Article
Publication date: 11 April 2008

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

The purpose of this paper is to investigate the rheological behaviour of three different lead‐free solder pastes used for surface mount applications in the electronic industry.

Abstract

Purpose

The purpose of this paper is to investigate the rheological behaviour of three different lead‐free solder pastes used for surface mount applications in the electronic industry.

Design/methodology/approach

This study concerns the rheological measurements of solder paste samples and is made up of three parts. The first part deals with the measurement of rhelogical properties with three different measuring geometries, the second part looks into the effect of frequencies on oscillatory stress sweep measurements and the final part reports on the characterisation and comparison of three different types of Pb‐free solder pastes.

Findings

Among the three geometries, the serrated parallel plate was found effective in minimising the wall‐slip effect. From the oscillatory stress‐sweep data with different frequencies; it was observed that the linear visco‐elastic region is independent of frequency for all the solder paste samples. To understand the shear thinning behaviour of solder paste, the well known Cross and Carreau models were fitted to the viscosity data. Moreover, creep‐recovery and dynamic frequency‐sweep tests were also carried out without destroying the sample's structure and have yielded useful information on the pastes behaviour.

Research limitations/implications

More extensive research is needed to fully characterise the wall‐slip behaviour during the rheological measurements of solder pastes.

Practical implications

The rheological test results presented in this paper will be of important value for research and development, quality control and facilitation of the manufacturing of solder pastes and flux mediums.

Originality/value

This paper shows how wall‐slip effects can be effectively avoided during rheological measurements of solder pastes. The paper also outlines how different rheological test methods can be used to characterise solder paste behaviours.

Details

Soldering & Surface Mount Technology, vol. 20 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 30 July 2019

Jianzhong Shang, Xin Li, Zhuo Wang, Rong Wang and Hong Zhu

This study aims to investigate rheological and extrusion behavior of thermosetting epoxy resins, which to find the universal property and printing parameters for…

Abstract

Purpose

This study aims to investigate rheological and extrusion behavior of thermosetting epoxy resins, which to find the universal property and printing parameters for extrusion-based rapid prototyping applications.

Design/methodology/approach

The thickener proportion greatly influences its viscosity and rheological behavior and therefore plays an important role in the shape of the cross-section of the extrudate.

Findings

A pseudoplastic (shear-thinning) is a basic requirement for obtaining extruded lines with plump cross-sections. In addition to the effects of the rheological behavior of the composite, shape maintenance and its wettability on the substrate, the cross-sectional geometry of the extrudate is also strongly affected by printing process parameters including the extrusion nozzle height, nozzle moving speed, extrusion rate and critical nozzle height. Proper combinations of these process parameters are necessary to obtain single-line extrudates with plump cross-sections and 3-D objects with dimensional accuracy, uniform wall thickness, good wall uprightness and no wall slumping. Formulas and procedures for determining these extrusion parameters are proposed and demonstrated in experiments.

Originality/value

The results obtained have been explained in terms of the interactions among the rheological properties of the composite, the shear rate imposed on the composite during extrusion, the wettability of the composite on the substrate and the shape maintenance of the composite during extrusion.

Details

Rapid Prototyping Journal, vol. 25 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 25 October 2018

Hongjuan Zheng and Weiqiang Song

Hyperbranched poly(ester-amide)s (HPEAs) have been synthesized from diethanolamine and maleic anhydride with ethylene glycol as a core monomer by using a two-step method…

Abstract

Purpose

Hyperbranched poly(ester-amide)s (HPEAs) have been synthesized from diethanolamine and maleic anhydride with ethylene glycol as a core monomer by using a two-step method, which are marked as Hupea polymers, and dehydration was carried out in xylene under reflux.

Design/methodology/approach

In comparison with Hupea polymers was synthesized by one-pot method, Hupea polymers synthesized by two-step method has different structure and rheological properties. The intermediate monomer and the resulting polymer are characterized by FTIR and NMR spectroscopies.

Findings

All of Mw, Mn and Mw/Mn of the hyperbranch polymers decrease with the core/monomer molar ratio increasing. The intrinsic viscosity ([η]) of the polymers decreases with Mw increasing in the investigated range of Mw and scales as [η]∼Mw-0.82, which implies that the molecular weight grew faster with core/monomer molar ratio decreasing than the volume in the investigated range of core/monomer molar ratio.

Research limitations/implications

The hydrodynamic radius was calculated by using Einstein’s equation and scales as Rh ∼ Mw0.061, and the lower exponent reveals the slow growth in the volume of Hupea molecule. In addition, the viscosity of Hupea polymer in concentrated aqueous solution is independent of shear rate and slightly dependent on molecular weight.

Practical implications

Hyperbranched poly(ester-amide)s (HPEAs) were synthesized by using a two-step method, which had different structure and rheological properties.

Originality/value

Hupea polymers show different features from Hupea polymers in structure and rheological properties, which revealed that the synthesis process of HPEA has effect on its performance.

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Article
Publication date: 8 May 2017

Mimi Azlina Abu Bakar, Siti Norazlini Abd Aziz and Muhammad Hussain Ismail

This paper aims to investigate the vital characteristic of an innovative ceramic injection molding (CIM) process for orthopedic application with controlled porosity and…

Abstract

Purpose

This paper aims to investigate the vital characteristic of an innovative ceramic injection molding (CIM) process for orthopedic application with controlled porosity and improved tribological and mechanical properties which were affected by complex tribological interactions, whether lubricated like hip implants and other artificial prostheses. The main objective is to maximize the usage of palm stearin as a single based binder as the function of flow properties during injection molding process.

Design/methodology/approach

The binder used in this present study consists of 100 per cent palm stearin manufactured by Kempas Oil Sdn Bhd and supplied by Vistec Technology Sdn Bhd. The feedstock was prepared by using a Z-blade mixer (Thermo Haake Rheomix OS) and Brabender mixer model R2400. The feedstock prepared was injection molded using a manually operated vertical benchtop machine with an average pressure of about 5-7 bars. The firing step included the temporary holds at intermediate temperatures to burn out organic binders. At this stage, the green molded specimen was de-bound using a single-step wick-debinding method.

Findings

The maximum content of ceramic material is applied to investigate the efficiencies of net formulation that can be achieved by ceramic materials. The longer the viscosity will change with shear rate, the higher the value of n obtained instead. From the slope of the curves obtained in Figure 3, the value of n for the feedstock was determined to be less than 1, which indicates a pseudoplastic behavior and suitability for the molding process. Moreover, high shear sensitivity is important in producing complex and intrinsic specimens which are leading products in the CIM industry.

Originality/value

The feedstock containing HAp powder and palm stearin binder was successfully prepared at very low temperature of 70°C, which promoting a required pseudo-plastic behavior during rheological test. The single binder palm stearin should be optimized in other research works carried out, as palm stearin is most preferred compared to other polymeric materials that provided high energy consumption when subjected to the sintering process. Besides the binder is widely available in Malaysia, low cost and harmless effect during debinding process.

Details

Industrial Lubrication and Tribology, vol. 69 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 6 September 2011

Ting‐Jin Lim, Azhar‐Mat Easa, Abdul‐Alias Karim, Rajeev Bhat and Min‐Tze Liong

The aim of this study is to develop a soy‐based cream cheese (SCC) with textural characteristics comparable to that of commercial dairy cream cheese (DCC) via the addition…

Abstract

Purpose

The aim of this study is to develop a soy‐based cream cheese (SCC) with textural characteristics comparable to that of commercial dairy cream cheese (DCC) via the addition of microbial transglutaminase (MTG), soy protein isolate (SPI) and maltodextrin (MD).

Design/methodology/approach

Response surface methodology (RSM) was employed in this study to determine the effects of MTG, MD and SPI on firmness of SCC.

Findings

The second‐order model generated via RSM was significant with only a 9.76 per cent variation not explained by the model. The coefficient of regression revealed that MTG, MD and SPI showed significant linear effects (P<0.0001) on the firmness of SCC, while MTG and SPI showed significant quadratic effects. The model successfully predicted and developed a SCC model with similar firmness as that of DCC; via the combination of 2.57 per cent (w/w) of MTG, 19.69 per cent (w/w) of SPI and 19.69 per cent (w/w) of MD. Physicochemical analyses revealed that SCC possessed lower fat content, reduced saturated fatty acid and zero trans fat. Further rheological measurements revealed that SCC was more solid‐like at room temperature, but less elastic at refrigerated temperature compared to DCC. SEM and SDS‐PAGE analyses affirmed that the textural changes of SCC were attributed to MTG‐induced cross‐linking.

Originality/value

The research demonstrated that a non‐dairy cream cheese could be developed using soy. In addition, the SCC also contained better nutritional properties compared to its dairy counterpart.

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Article
Publication date: 18 December 2020

Thameem Basha Hayath, Sivaraj Ramachandran, Ramachandra Prasad Vallampati and O. Anwar Bég

Generally, in computational thermofluid dynamics, the thermophysical properties of fluids (e.g. viscosity and thermal conductivity) are considered as constant. However, in…

Abstract

Purpose

Generally, in computational thermofluid dynamics, the thermophysical properties of fluids (e.g. viscosity and thermal conductivity) are considered as constant. However, in many applications, the variability of these properties plays a significant role in modifying transport characteristics while the temperature difference in the boundary layer is notable. These include drag reduction in heavy oil transport systems, petroleum purification and coating manufacturing. The purpose of this study is to develop, a comprehensive mathematical model, motivated by the last of these applications, to explore the impact of variable viscosity and variable thermal conductivity characteristics in magnetohydrodynamic non-Newtonian nanofluid enrobing boundary layer flow over a horizontal circular cylinder in the presence of cross-diffusion (Soret and Dufour effects) and appreciable thermal radiative heat transfer under a static radial magnetic field.

Design/methodology/approach

The Williamson pseudoplastic model is deployed for rheology of the nanofluid. Buongiorno’s two-component model is used for nanoscale effects. The dimensionless nonlinear partial differential equations have been solved by using an implicit finite difference Keller box scheme. Extensive validation with earlier studies in the absence of nanoscale and variable property effects is included.

Findings

The influence of notable parameters such as Weissenberg number, variable viscosity, variable thermal conductivity, Soret and Dufour numbers on heat, mass and momentum characteristics are scrutinized and visualized via graphs and tables.

Research limitations/implications

Buongiorno (two-phase) nanofluid model is used to express the momentum, energy and concentration equations with the following assumptions. The laminar, steady, incompressible, free convective flow of Williamson nanofluid is considered. The body force is implemented in the momentum equation. The induced magnetic field strength is smaller than the external magnetic field and hence it is neglected. The Soret and Dufour effects are taken into consideration.

Practical implications

The variable viscosity and thermal conductivity are considered to investigate the fluid characteristic of Williamson nanofluid because of viscosity and thermal conductivity have a prime role in many industries such as petroleum refinement, food and beverages, petrochemical, coating manufacturing, power and environment.

Social implications

This fluid model displays exact rheological characteristics of bio-fluids and industrial fluids, for instance, blood, polymer melts/solutions, nail polish, paint, ketchup and whipped cream.

Originality/value

The outcomes disclose that the Williamson nanofluid velocity declines by enhancing the Lorentz hydromagnetic force in the radial direction. Thermal and nanoparticle concentration boundary layer thickness is enhanced with greater streamwise coordinate values. An increase in Dufour number or a decrease in Soret number slightly enhances the nanofluid temperature and thickens the thermal boundary layer. Flow deceleration is induced with greater viscosity parameter. Nanofluid temperature is elevated with greater Weissenberg number and thermophoresis nanoscale parameter.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 February 1998

Y. Chastel, C. Magny and F. Bay

A finite element model for multimaterial configurations is presented. The material behavior of each body within a composite material is given by an elastic‐viscoplastic…

Abstract

A finite element model for multimaterial configurations is presented. The material behavior of each body within a composite material is given by an elastic‐viscoplastic constitutive law. Automatic remeshing techniques which preserve the topology of the different bodies of material are used to simulate large deformations of the multiphasic system. An experimental set‐up has been designed in order to simulate the compaction of multilayer composite materials. Plasticine was chosen as a model material. Experimental results are used to validate the finite element model for consolidation of multilayer composites.

Details

Engineering Computations, vol. 15 no. 1
Type: Research Article
ISSN: 0264-4401

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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

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