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Article
Publication date: 27 June 2008

R. Durairaj, S. Mallik and N.N. Ekere

The purpose of this paper is to develop a quality control tool based on rheological test methods for solder paste and flux media.

Abstract

Purpose

The purpose of this paper is to develop a quality control tool based on rheological test methods for solder paste and flux media.

Design/methodology/approach

The rheological characterisation of solder pastes and flux media was carried out through the creep‐recovery, thixotropy and viscosity test methods. A rheometer with a parallel plate measuring geometry of 40 mm diameter and a gap height of 1 mm was used to characterise the paste and associated flux media.

Findings

The results from the study showed that the creep‐recovery test can be used to study the deformation and recovery of the pastes, which can be used to understand the slump behaviour in solder pastes. In addition, the results from the thixotropic and viscosity test were unsuccessful in determining the differences in the rheological flow behaviour in the solder pastes and the flux medium samples.

Research limitations/implications

More extensive rheological and printing testing is needed in order to correlate the findings from this study with the printing performance of the pastes.

Practical implications

The rheological test method presented in the paper will provide important information for research and development, quality control and production staff to facilitate the manufacture of solder pastes and flux media.

Originality/value

The paper explains how the rheological test can be used as a quality control tool to identify the suitability of a developmental solder paste and flux media used for the printing process.

Details

Soldering & Surface Mount Technology, vol. 20 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 August 2001

R. Durairaj, T.A. Nguty and N.N. Ekere

The paste printing process accounts for the majority of assembly defects, and most defects originate from poor understanding of the effect of printing process parameters…

Abstract

The paste printing process accounts for the majority of assembly defects, and most defects originate from poor understanding of the effect of printing process parameters on the printing performance. As the current product miniaturisation trend continues, area array type package solutions are now being designed into products. The assembly of these devices requires the printing of very small solder paste deposits. The printing of solder pastes through small stencil apertures typically results in stencil clogging and incomplete transfer of paste to the PCB pads. At the very narrow aperture sizes required for flip‐chip applications, the paste rheology becomes crucial for consistent paste withdrawal. This is because, for smaller paste volumes, surface tension effects become dominant over viscous flow. Proper understanding of the effect of the key material, equipment and process parameters, and their interactions, is crucial for achieving high print yields. During the aperture filling and emptying sub‐process, the solder paste experiences forces/stresses as it interacts with the stencil aperture walls and the pad surfaces, which directly impact the paste flow within the apertures. As the substrate and stencil separate, the frictional/adhesive force on the stencil walls competes directly with the adhesives/pull force on the PCB pads, often resulting in incomplete paste transfer or skipping/clogged apertures. In this paper, we investigate the effect of stencil design on the printing process and in particular the effect on paste transfer efficiency.

Details

Soldering & Surface Mount Technology, vol. 13 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 6 July 2015

Lijun Chen, Zhongbin Bao, Zhengrong Fu and Wen Li

The purpose of this research is to prepare a dispersion resin with good dispersity and a colour paste with good stability. At present, the colour paste is being prepared…

Abstract

Purpose

The purpose of this research is to prepare a dispersion resin with good dispersity and a colour paste with good stability. At present, the colour paste is being prepared using the pigment dispersion resin which has the group quaternary ammonium. The dispersion resin prepared has good dispersity of pigment and extender. However, the stability of storage and construction of the colour paste is relatively poor, which has a negative influence on the application of cathodic electrodeposited (CED) coatings. However, the detailed investigation on the dispersion resin and the stable colour paste has not been reported.

Design/methodology/approach

Three steps are adopted to prepare the dispersion resin, that is blocking toluene diisocyanate (TDI), quaternary ammoniation of blocked TDI and ring opening of epoxy resin. The resultant dispersion is used to prepare the colour paste. The factors, which have an influence on the dispersity of the dispersion resin and stability of the colour paste, are optimised.

Findings

The typical recipes of preparing the dispersion resin and the resultant colour paste are obtained. The dispersity of the dispersion resin and stability of the colour paste are good based on the typical recipe. In addition, the film of the CED coating is smooth, dense and hard when the colour paste is used in the CED coating.

Practical implications

The dispersion resin can be used to prepare a colour paste, which can be used in the CED coatings. In addition, it also can be applied as a binder of coatings and adhesions.

Originality/value

The factors, which have an influence on the dispersity of the dispersion resin and stability of the colour paste, are studied in detail. The typical recipes of preparing the dispersion resin and the resultant colour paste are obtained. Based on the typical recipe, the dispersity of the dispersion resin and stability of the colour paste are good.

Details

Pigment & Resin Technology, vol. 44 no. 4
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 January 1994

N. Geren and N.N. Ekere

Although rework is labour intensive and conflicts with most modern manufacturing/assembly philosophies, realistic defect levels in surface mount technology (SMT) printed…

Abstract

Although rework is labour intensive and conflicts with most modern manufacturing/assembly philosophies, realistic defect levels in surface mount technology (SMT) printed circuit board (PCB) assembly render rework indispensable on the shop floor. Most commercially available rework tools are manual or require very skilled operators for their efficient operation. The challenges of automating SMD rework are significant because the tools, their specifications and rework processes required are not fully understood, and the impact of rework processes on assembly quality and reliability are hotly debated. This paper describes an automated robotic rework cell for SMD and TH boards, and the method used for process characterisation of the solder paste dispensing system. The paper also describes equipment selection, the integration and interfacing of the dispensing equipment to the cell controller and the process characterisation experiments.

Details

Soldering & Surface Mount Technology, vol. 6 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 2003

Ling Chunxian Zou, Milos Dusek, Martin Wickham and Christopher Hunt

Enclosed print heads have recently been developed as an improvement on the traditional squeegee methods for solder paste printing. They offer the opportunity of widening…

Abstract

Enclosed print heads have recently been developed as an improvement on the traditional squeegee methods for solder paste printing. They offer the opportunity of widening the printing process window and reducing process waste. Consequently, this work was undertaken to evaluate some aspects of enclosed print head printing, and it has been shown to be a robust process. A number of performance factors were established: with increased humidity the paste degradation was limited due to its sealed paste reservoir; the system also permitted successful intermittent printing over a 5 day period; printing is much more tolerant to distorted substrates than some squeegee blades, and hence improves printing on non‐planar surfaces; significant reduction in paste wastage occurs, since paste ageing is reduced.

Details

Soldering & Surface Mount Technology, vol. 15 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 December 1997

M. Warwick and I. Harpley

‘Fine Pitch’and ‘High speed printing’ are relative terms but many solder paste users seecapability in meeting these two requirements as their major goals for process…

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Abstract

‘Fine Pitch’ and ‘High speed printing’ are relative terms but many solder paste users see capability in meeting these two requirements as their major goals for process improvements. Not surprisingly, solder paste rheology governs both, and this paper describes how the complex relationship between resins and solvent can lead to solder pastes with optimised performance. Work on the physical behaviour of resin solutions and how this relates to solder paste rheology is reported. These results are related to user experience on volume production processes.

Details

Soldering & Surface Mount Technology, vol. 9 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: 1 December 2004

Janusz Sitek, Dubravka Ročak, Krystyna Bukat, Janeta Fajfar‐Plut and Darko Belavič

The European Commission has decided that from the second half of 2006 only lead‐free solder pastes will be permitted for use in the electronics industry. Earlier results…

Abstract

The European Commission has decided that from the second half of 2006 only lead‐free solder pastes will be permitted for use in the electronics industry. Earlier results of testing showed that lead‐free solder pastes may not be appropriate for both printed‐circuit‐board (PCB) and hybrid‐circuit applications, because of the materials' compatibility with the soldering process and with the solder pads. The basic properties of the investigated pastes show which of the tested solder pastes can be used for both applications. After selection of the appropriate solder pastes, reliability tests were conducted. The surface insulation resistance was tested for both the hybrid circuits and PCBs, whereas the mechanical strength of the soldered joints of components was only tested for the PCBs.

Details

Soldering & Surface Mount Technology, vol. 16 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 March 1986

M. Budweit

In various publications noble steel is mentioned as a possibility for use as a substrate in thick film technology processing. The possibility to cut, stencil and drill…

Abstract

In various publications noble steel is mentioned as a possibility for use as a substrate in thick film technology processing. The possibility to cut, stencil and drill steel sheets to desired shapes and the attractive price difference compared with alumina as well as PC board materials justified an investigation. A variety of steel sheets in various formulations from various vendors is offered on the market as well as ceramic pastes for thick film applications. This investigation aims to find out the most suitable ceramic paste for coating steel substrates in a common thick film process.

Details

Microelectronics International, vol. 3 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 April 2002

R. Durairaj, G.J. Jackson, N.N. Ekere, G. Glinski and C. Bailey

Soldering technologies continue to evolve to meet the demands of the continuous miniaturisation of electronic products, particularly in the area of solder paste

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1096

Abstract

Soldering technologies continue to evolve to meet the demands of the continuous miniaturisation of electronic products, particularly in the area of solder paste formulations used in the reflow soldering of surface mount devices. Stencil printing continues to be a leading process used for the deposition of solder paste onto printed circuit boards (PCBs) in the volume production of electronic assemblies, despite problems in achieving a consistent print quality at an ultra‐fine pitch. In order to eliminate these defects a good understanding of the processes involved in printing is important. Computational simulations may complement experimental print trials and paste characterisation studies, and provide an extra dimension to the understanding of the process. The characteristics and flow properties of solder pastes depend primarily on their chemical and physical composition and good material property data is essential for meaningful results to be obtained by computational simulation.This paper describes paste characterisation and computational simulation studies that have been undertaken through the collaboration of the School of Aeronautical, Mechanical and Manufacturing Engineering at Salford University and the Centre for Numerical Modelling and Process Analysis at the University of Greenwich. The rheological profile of two different paste formulations (lead and lead‐free) for sub 100 micron flip‐chip devices are tested and applied to computational simulations of their flow behaviour during the printing process.

Details

Soldering & Surface Mount Technology, vol. 14 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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