| 1. |
- Mark, Andreas, 1980, et al.
(författare)
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Simulation of a Non-Newtonian Dense Granular Suspension in a Microfluidic Contraction
- 2013
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Ingår i: 8th International Conference on Multiphase Flow.
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Konferensbidrag (refereegranskat)abstract
- The success of a solder paste jet printer is based on an uninterrupted flow of fluid, specifically dense fluid suspensions, through a series of ducts inside the printing head. It is well known that the flow of dense suspensions is prone to jamming and sedimentation effects, both of which could entail detrimental failure modes in the printing heads. A thorough understanding of the fluid dynamics of suspensions as they flow through ducts and connections is of utmost importance. The purpose of this study is to propose a novel simulation framework and to show that it captures the main effects such as mass flow and partial jamming in a cylindrical duct test configuration. The granular suspension is a generic solder paste with solder particlesimmersed in a flux. The simulations are performed in the multi-phase flow solver IBOFlow. A two fluid model is used for the granular suspension and the discretization is done an Euler-Euler framework. The averaged momentum equations from Enwald et al. (1996) are solved together with the common continuity equation generating a shared pressure field. Explicit constitutive equations for the interfacial momentum transfer and particle pressure are employed. To capture the shear thinning effects of the non-Newtonian suspensions the standard Carreau rheology model is used. To study how the fluid flow affects the local volume fraction and partial jamming in the duct, simulations are performed for different applied pressure drops ranging from one to five bars. For both particle pressure models, the resulting mean bulk velocities are compared with experiments with good agreement, and partial jamming is observed. Hence, it is concluded that the proposed framework is suitable to model and simulate the granular suspension in a micro fluid contraction.
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| 2. |
- Svensson, Martin, 1987, et al.
(författare)
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Simulation of Droplet Jetting of a Non-Newtonian Mixed Suspension
- 2016
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Ingår i: ICMF-2016 – 9th International Conference on Multiphase Flow May 22nd – 27th 2016, Firenze, Italy.
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Konferensbidrag (refereegranskat)abstract
- The jet printing of a dense mixed non-Newtonian suspension is based on the rapid displacement of fluid through a nozzle, the forming of a droplet and eventually the break-off of the filament. The ability to model this process would facilitate the development of future jetting devices. The purpose of this study is to propose a novel simulation framework and to show that it captures the main effects such as droplet shape, volume and speed. In the framework, the time dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two phase system with the surrounding air being one phase and the dense suspension the other. Hence, the non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver and LaStFEM, a large strain FEM solver. Jetting behaviour was shown to be affected not only by piston motion and fluid rheology, but also by the energy loss in the jetting head. The simulation results were compared to experimental data obtained from an industrial jetting head.
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| 3. |
- Andersson, Martin, et al.
(författare)
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Flowing and pressurizing a solid-liquid two phase monodispersed fluid with high solid content in a transparent microfluidic high-pressure chip
- 2017
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Ingår i: 28TH MICROMECHANICS AND MICROSYSTEMS EUROPE WORKSHOP. - : IOP PUBLISHING LTD. ; 922:1
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Konferensbidrag (refereegranskat)abstract
- Handling highly concentrated solid-liquid two-phase fluids in microfluidics is challenging. In this paper, we present the first studies of flowing solder paste with a high solid content in a transparent high-pressure tolerant glass chip, thereby increasing the understanding of how multiphase liquids with high density difference between the phases behave in small channels (840 mu m in diameter). The system, including a custom made high-pressure, low resistance, interface, was continuously operated at pressures up to of 6 MPa and devices where shown to have pressure tolerance up to 17 MPa. During flow through the chip, the packing density of the solder balls displayed inhomogeneity over the channel where chains of solder balls in contact with each other were formed together with voids. These in-homogeneities persisted along the channel during flow. The flow rate of the paste through the chip oscillated between 63 to 350 mu m/s when pumping at constant volume rate of 30 mu l/min. When a pressure of 2 MPa was applied, the volume of the solder paste particle segment decreased 1.6%, and 0.1% was elastically recovered when the pressure was released. It is concluded that this transparent microfluidic high-pressure glass chip with the special developed interface is suitable for flow studies of solder paste with a high solid content.
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| 4. |
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| 5. |
- Hu, Zhili, 1983, et al.
(författare)
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Detecting single molecules inside a carbon nanotube to control molecular sequences using inertia trapping phenomenon
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:13, s. Art. no. 133105-
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Tidskriftsartikel (refereegranskat)abstract
- Here we show the detection of single gas molecules inside a carbon nanotube based on the change inresonance frequency and amplitude associated with the inertia trapping phenomenon. As its directimplication, a method for controlling the sequence of small molecule is then proposed to realize theconcept of manoeuvring of matter atom by atom in one dimension. The detection as well as theimplication is demonstrated numerically with the molecular dynamics method. It is theoreticallyassessed that it is possible for a physical model to be fabricated in the very near future.
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| 6. |
- Hu, Z. L., et al.
(författare)
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Molecular dynamics simulation of inertial trapping-induced atomic scale mass transport inside single walled carbon nanotubes
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:8
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Tidskriftsartikel (refereegranskat)abstract
- The forced transverse vibration of a single-walled carbon nanotube (SWNT) embedded with atomic-size particles was investigated using molecular dynamic simulations. The particles inside the cylindrical cantilever can be trapped near the antinodes or at the vicinity of the SWNT tip. The trapping phenomenon is highly sensitive to the external driving frequencies such that even very small changes in driving frequency can have a strong influence on the probability of the location of the particle inside the SWNT. The trapping effect could potentially be employed to realize the atomic scale control of particle position inside an SWNT via the finite adjustment of the external driving frequency. It may also be suggested that the trapping phenomenon could be utilized to develop high-sensitive mass detectors based on a SWNT resonator.
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| 7. |
- Khorramdel, Behnam, et al.
(författare)
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Inkjet printing technology for increasing the I/O density of 3D TSV interposers
- 2017
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Ingår i: Microsystems & Nanoengineering. - : Nature Publishing Group. - 2055-7434. ; 3, s. 17002-
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Tidskriftsartikel (refereegranskat)abstract
- Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (-40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.
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| 8. |
- Mårtensson, Gustaf, 1972-
(författare)
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Analysis of laminar and turbulent flows with turbomachinery, biotechnology and biomechanical applications
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The goal of this study was initially to gain a better understanding of the effects of rotation on turbulent flow in ducts. Knowledge concerning the influence of rotation on the structures of turbulence is of fundamental importance in many applications, e.g. centrifugal separators, turbines or cooling channels in rotating machinery, as well as meteorology and oceanography. Rapidly rotating duct flow is studied experimentally with rotation numbers in the interval [ 0, 1] . To achieve this, in combination with relatively high Reynolds numbers (5000 – 30000 based on the hydraulic radius), water was used as the working medium. The influence of the rotation on the pressure drop in the duct was investigated and suitable scalings of this quantity were studied. Due to questions that arose in the experimental study, two numerical studies were initiated. The first study probed the effect of rotation and geometrical configuration on the development length for turbulent flow, while the second comprised a direct numerical simulation of turbulent flow in a rotating duct. It is shown that while system rotation does not have a marked effect on the development length in a plane channel, the development length is substantially shortened in a duct. Additional systems subject to rotation or curvature effects were studied. The laminar flow of fluid in a rotating PCR-cone was analysed analytically and numerically to understand the increased mixing and temperature homogenization. The flow field in the cone was described and the increased mixing was due to a strong boundary layer flow incited by Coriolis and buoyancy effects. Comparisons of the numerical simulations with experiments yielded good results. A study to quantify the flow of blood in cerebral malformations using three-dimensional videodensitometry was performed. Data from experiments with an idealized flow phantom, as well clinical pathologies, showed that the proposed methodology in conjunction with clinical injection protocols can yield mean flux data with an error less than 20%. Protocol improvements are proposed.
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| 9. |
- Mårtensson, Gustaf, 1972
(författare)
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Jet Printing of low temperature solder paste
- 2013
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Ingår i: IPC APEX EXPO Conference and Exhibition 2013, APEX EXPO 2013. - 9781627485456 ; 1, s. 296-313
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Konferensbidrag (refereegranskat)abstract
- Low temperature paste offers a production solution for advanced applications • Jet printing furthers these opportunities.
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| 10. |
- Mårtensson, Gustaf, 1972, et al.
(författare)
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Simulation of jet printing of solder paste for surface mounted technology
- 2021
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed. Design/methodology/approach In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry. Findings Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%. Research limitations/implications The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension. Practical implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration. Social implications The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print. Originality/value While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.
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