Kurian J. Vachaparambil, Gustaf Mårtensson and Lars Essén
The purpose of the paper is to develop a methodology to characterize the rheological behaviour of macroscopic non-Brownian suspensions, like solder paste, based on microstructural…
Abstract
Purpose
The purpose of the paper is to develop a methodology to characterize the rheological behaviour of macroscopic non-Brownian suspensions, like solder paste, based on microstructural evolution.
Design/methodology/approach
A structure-based kinetics model, whose parameters are derived analytically based on assumptions valid for any macroscopic suspension, is developed to describe the rheological behaviour of a given fluid. The values of the parameters are then determined based on experiments conducted at a constant shear rate. The parameter values, obtained from the model, are then adjusted using an optimization algorithm using the mean deviation from experiments as the cost function to replicate the measured rheology. A commercially available solder paste is used as the test fluid for the proposed method.
Findings
The initial parameter values obtained through the analytical model indicates a structural breakdown that is much slower than observations. But optimizing the parameter values, especially the ones associated with the structural breakdown, replicates the thixotropic behaviour of the solder paste reasonably well, but it fails to capture the structure build-up during the three interval thixotropy test.
Research limitations/implications
The structural kinetics model tends to under-predict the structure build-up rate.
Practical implications
This study details a more realistic prediction of the rheological behaviour of macroscopic suspensions like solder paste, thermal interface materials and other functional materials. The proposed model can be used to characterize different solder pastes and other functional fluids based on the structure build-up and breakdown rates. The model can also be used as the viscosity definitions in numerical simulations instead of simpler models like Carreau–Yasuda and cross-viscosity models.
Originality/value
The rheological description of the solder paste is critical in determining its validity for a given application. The methodology described in the paper provides a better description of thixotropy without relying on the existing rheological measurements or the behaviour predicted by a standard power-law model. The proposed model can also provide transient viscosity predictions when shear rates vary in time.
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Nowadays, most European welfare states have to face a crisis and to adapt themselves in the context of globalisation. This is true for most of the “original” European member…
Abstract
Nowadays, most European welfare states have to face a crisis and to adapt themselves in the context of globalisation. This is true for most of the “original” European member states, so what a challenge for the European central and eastern countries that had to reform deeply their social systems in order to fit the rules of the market economy and join the European Union. So the point is to know in which direction the national systems of social protection are going by now.
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Puts forward the limit to growth perspective, which is rarely mentioned in societies devoted to the increase of material living standards. Outlines the resources each individual…
Abstract
Puts forward the limit to growth perspective, which is rarely mentioned in societies devoted to the increase of material living standards. Outlines the resources each individual in rich countries uses and extrapolates those figures to cover the rest of the world’s population, proving that it is clearly impossible to sustain such living standards. Criticizes profit maximization, market forces and the pursuit of business opportunities as inappropriate to the needs of the world’s poor majority. Explores how society could reduce its per capita resource use and environmental impact, particularly through the development of small scale self‐sufficient economies. Points out that most of the real economy would be in non‐cash areas. Hastens to mention that a simpler, less material and closer‐to‐nature lifestyle does not exclude information technology. Indicates that access to communal property and service needs to replace income as the means to a satisfying life. Summarizes how community gardens can be set up and the roles that community workers could play in saving towns.
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It's been three years since my previous survey in RSR. Superb reference books in pop music have been appearing so frequently that I've been having trouble keeping up. Let's hope…
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It's been three years since my previous survey in RSR. Superb reference books in pop music have been appearing so frequently that I've been having trouble keeping up. Let's hope “next year's” survey will only be 12 months in the making and not 36.
Outlines the Libertarian framework of rights and obligations in abortion. Argues that abortion is homicide based upon the scientific and philosophic evidence available and…
Abstract
Outlines the Libertarian framework of rights and obligations in abortion. Argues that abortion is homicide based upon the scientific and philosophic evidence available and disputes further points believed by abortion proponents.
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Meckler Publishing has announced the acquisition of Micro Software Reports and Micro Software Evaluations from Nolan Information Management Services of Torrance, California. Alan…
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Meckler Publishing has announced the acquisition of Micro Software Reports and Micro Software Evaluations from Nolan Information Management Services of Torrance, California. Alan M. Meckler, President of Meckler Publishing, stated that “Micro Software Reports is the world's largest and most comprehensive index to microcomputer software with specific library applications”. He went on to say that “the publication indexes 110 library and computer oriented journals concentrating on information that includes pricing, installation locations and complete system descriptions”.