Rheological characterisation of solder pastes and isotropic conductive adhesives used for flip-chip assembly

Durairaj, R.; Mallik, Sabuj; Seman, Anasyida Abu; Marks, A.E.; Ekere, N.N.

doi:10.1016/j.jmatprotec.2008.09.013

Cited by 54 publications

(33 citation statements)

References 6 publications

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“…The cross‐over point was reached for a modulus equal to ≈398 Pa. This value of stress at G ′ = G ″ is comparable with the silver flake‐based ink which has a much higher solid contents (>60%) . As described above, the larger aspect ratio and unique network structure of AgNWs play a critical role to contribute in the rheological behavior of the AgNW ink.…”

Section: Viscosity Of Various Agnw Inks At Different Shear Rates Corrsupporting

confidence: 55%

“…This region is related to the beginning of the weakening and gradual breakdown of the AgNW ink structure; although the ink still has an elastic‐dominated behavior ( G ′ > G ″), the ink exhibits a more liquid‐like behavior as shear stress increased . Region III started at the shear stress when the storage modulus is equal to the loss modulus ( G ″ = G ′), and extends to the higher shear stresses when G ″ became larger than G ′ and the ink behavior crossed over from solid‐like to liquid‐like behavior . The cross‐over point was reached for a modulus equal to ≈398 Pa.…”

Section: Viscosity Of Various Agnw Inks At Different Shear Rates Corrmentioning

confidence: 99%

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A Water‐Based Silver‐Nanowire Screen‐Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin‐Film Transistors

2016

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A water-based silver-nanowire (AgNW) ink is formulated for screen printing. Screen-printed AgNW patterns have uniform sharp edges, ≈50 μm resolution, and electrical conductivity as high as 4.67 × 10(4) S cm(-1) . The screen-printed AgNW patterns are used to fabricate a stretchable composite conductor, and a fully printed and intrinsically stretchable thin-film transistor array is also realized.

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Section: Viscosity Of Various Agnw Inks At Different Shear Rates Corrsupporting

confidence: 55%

Section: Viscosity Of Various Agnw Inks At Different Shear Rates Corrmentioning

confidence: 99%

A Water‐Based Silver‐Nanowire Screen‐Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin‐Film Transistors

2016

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“…It has been reported that a higher metal content will increase the viscosity of solder pastes. 12,14) This correlation could be confirmed to higher shear rate value for Paste 4 and Paste 3. For example, Paste 3 has a metal content of 90.0 %, and showed a higher viscosity than Paste 4 with a metal content of 89.5 %.…”

Section: Viscosity Test Resultssupporting

confidence: 60%

Printing Morphology and Rheological Characteristics of Lead-Free Sn-3Ag-0.5Cu (SAC) Solder Pastes

Sharma¹,

Mallik²,

Ekere³

et al. 2014

Journal of the Microelectronics and Packaging Society

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Solder paste plays a crucial role as the widely used joining material in surface mount technology (SMT). The understanding of its behaviour and properties is essential to ensure the proper functioning of the electronic assemblies. The composition of the solder paste is known to be directly related to its rheological behaviour. This paper provides a brief overview of the solder paste behaviour of four different solder paste formulations, stencil printing processes, and techniques to characterize solder paste behaviour adequately. The solder pastes are based on the Sn-3.0Ag-0.5Cu alloy, are different in their particle size, metal content and flux system. The solder pastes are characterized in terms of solder particle size and shape as well as the rheological characterizations such as oscillatory sweep tests, viscosity, and creep recovery behaviour of pastes.

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“…Shear... Non-structured of solder paste IlII"" state of solder paste (1) where the rate constant, k, is a function of shear rate to de determined experimentally, and n is the order of the breakdown reaction. Initially, at the fully structured state, t =0 : A = ,10 and at equilibrium state, t~00 : A =A e • Integration of equation (3) can only be achieved in certain special cases.…”

Section: Structured Statementioning

confidence: 99%

“…Solder paste can be categorised as a homogeneous and dense suspension of solder alloy particles suspended in a flux medium. For a typical solder paste the typical metal content (solder alloy particles) lies between 88 -91% by weight, and about 30 -70% by volume [1]. The main constituent of flux medium is a naturally occurring rosin or resin.…”

Section: Introductionmentioning

confidence: 99%

Modelling of the time-dependent flow behaviour of lead-free solder pastes used for flip-chip assembly applications

Mallik

Ekere

Marks

et al. 2008

2008 2nd Electronics Systemintegration Technology Conference

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The market for solder paste materials in the electronic manufacturing and assembly sector is very large and consists of material and equipment suppliers and end users. These materials are used to bond electronic components (such as flip-chip, CSP and BGA) to printed circuit boards (PCB's) across a range of dimensions where the solder interconnects can be in the order of 0.05mm to 5mm in size. The non-Newtonian flow properties exhibited by solder pastes during its manufacture and printing/deposition phases have been of practical concern to surface mount engineers and researchers for many years. The printing of paste materials through very small-sized stencil apertures is known to lead to increased stencil clogging and incomplete transfer of paste to the substrate pads. At these very narrow aperture sizes the paste rheology and particle-wall interactions become crucial for consistent paste withdrawal. These non-Newtonian effects must be understood so that the new paste formulations can be optimised for consistent printing. The focus of the study reported in this paper is the characterisation of the rheological properties of solder pastes and flux mediums, and the evaluation of the effect of these properties on the pastes' printing performance at the flip-chip assembly application level.Solder pastes are known to exhibit a thixotropic behaviour, which is recognised by the decrease in apparent viscosity of paste material with time when subjected to a constant shear rate. The proper characterisation of this time-dependent rheological behaviour of solder pastes is crucial for establishing the relationships between the pastes' structure and flow behaviour; and for correlating the physical parameters with paste printing performance. In this paper, we present a number of methods which have been developed for characterising the time-dependent and non-Newtonian rheological behaviour of solder pastes and flux mediums as a function of shear rates. We also present results of the study of the rheology of the solder pastes and flux mediums using the structural kinetic modelling approach, which postulates that the network structure of solder pastes breaks down irreversibly under shear, leading to time and shear dependent changes in the flow properties. Our results show that for the solder pastes used in the study, the rate and extent of thixotropy was generally found to increase with increasing shear rate. The technique demonstrated in this study has wide utility for R&D personnel involved in new paste formulation, for implementing quality control procedures used in solder paste manufacture and packaging; and for qualifying new flip-chip assembly lines.

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Rheological characterisation of solder pastes and isotropic conductive adhesives used for flip-chip assembly

Cited by 54 publications

References 6 publications

A Water‐Based Silver‐Nanowire Screen‐Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin‐Film Transistors

A Water‐Based Silver‐Nanowire Screen‐Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin‐Film Transistors

Printing Morphology and Rheological Characteristics of Lead-Free Sn-3Ag-0.5Cu (SAC) Solder Pastes

Modelling of the time-dependent flow behaviour of lead-free solder pastes used for flip-chip assembly applications

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