| 311. |
- Peng, Wangli, et al.
(författare)
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Mechanical properties of a novel Nano-Thermal Interface Material
- 2013
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Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781479906758 ; , s. 942-945
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Konferensbidrag (refereegranskat)abstract
- Continued miniaturization in combination with increased performance in microelectronics has generated an urgent need for improved thermal management techniques in order to maintain reliability in systems and devices. Thermal interface materials play a key role in the development of solutions for thermal management in microelectronics. In this paper, mechanical properties of a nanotechnology enhanced thermal interface material (Nano-TIM) were studied. The material is based on Sn-Ag-Cu based alloy reinforced with nano scale fiber matrix. Tensile tests were used to investigate and compare the elastic modulus at room temperature and mechanical strength between 20 to 100°C. Scanning Electron Microscopy (SEM) analysis techniques were used to investigate the morphology of the fracture section after tensile tests as well as the internal structure of the samples. The results show that the Nano-TIM can have a significantly lower elastic modulus compared to the pure alloy phase of SnAgCu due to its fiber phase. A lower elastic modulus of the solder joint can be important since it will reduce the stress transfer across the interface. This is particular important when the joint substrates have mismatching coefficients of thermal expansion. The findings of this study thus indicate that the Nano-TIM may provide a useful alternative to improve the thermomechanical reliability compared to pure solder joints. © 2013 IEEE.
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| 312. |
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| 313. |
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| 314. |
- Puschmann, Till B., et al.
(författare)
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A Novel Method for Three-Dimensional Culture of Central Nervous System Neurons.
- 2014
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Ingår i: Tissue engineering. Part C, Methods. - 1937-3392 .- 1937-3384. ; 20:6, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- Neuronal signal transduction and communication in vivo is based on highly complex and dynamic networks among neurons expanding in a three-dimensional (3D) manner. Studies of cell-cell communication, synaptogenesis, and neural network plasticity constitute major research areas for understanding the involvement of neurons in neurodegenerative diseases, such as Huntington's, Alzheimer's, and Parkinson's disease, and in regenerative neural plasticity responses in situations, such as neurotrauma or stroke. Various cell culture systems constitute important experimental platforms to study neuronal functions in health and disease. A major downside of the existing cell culture systems is that the alienating planar cell environment leads to aberrant cell-cell contacts and network formation and increased reactivity of cell culture-contaminating glial cells. To mimic a suitable 3D environment for the growth and investigation of neuronal networks in vitro has posed an insurmountable challenge. Here, we report the development of a novel electrospun, polyurethane nanofiber-based 3D cell culture system for the in vitro support of neuronal networks, in which neurons can grow freely in all directions and form network structures more complex than any culture system has so far been able to support. In this 3D system, neurons extend processes from their cell bodies as a function of the nanofiber diameter. The nanofiber scaffold also minimizes the reactive state of contaminating glial cells.
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| 315. |
- Puschmann, Till B., et al.
(författare)
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Bioactive 3D cell culture system minimizes cellular stress and maintains the in vivo-like morphological complexity of astroglial cells
- 2013
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Ingår i: Glia. - : Wiley. - 0894-1491 .- 1098-1136. ; 61:3, s. 432-440
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Tidskriftsartikel (refereegranskat)abstract
- We tested the hypothesis that astrocytes grown in a suitable three-dimensional (3D) cell culture system exhibit morphological and biochemical features of in vivo astrocytes that are otherwise lost upon transfer from the in vivo to a two-dimensional (2D) culture environment. First, we report development of a novel bioactively coated nanofiber-based 3D culture system (Bioactive3D) that supports cultures of primary mouse astrocytes. Second, we show that Bioactive3D culture system maintains the in vivo-like morphological complexity of cultured cells, allows movement of astrocyte filopodia in a way that resembles the in vivo situation, and also minimizes the cellular stress, an inherent feature of standard 2D cell culture systems. Third, we demonstrate that the expression of gap junctions is reduced in astrocytes cultured in a 3D system that supports well-organized cell-cell communication, in contrast to the enforced planar tiling of cells in a standard 2D system. Finally, we show that astrocytes cultured in the Bioactive3D system do not show the undesired baseline activation but are fully responsive to activation-inducing stimuli. Thus, astrocytes cultured in the Bioactive3D appear to more closely resemble astrocytes in vivo and represent a superior in vitro system for assessing (patho)physiological and pharmacological responses of these cells and potentially also in co-cultures of astrocytes and other cell types.
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| 316. |
- Puschmann, Till B., et al.
(författare)
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HB-EGF affects astrocyte morphology, proliferation, differentiation, and the expression of intermediate filament proteins
- 2014
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Ingår i: Journal of Neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 128:6, s. 878-889
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Tidskriftsartikel (refereegranskat)abstract
- Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a vascular-derived trophic factor, belongs to the epidermal growth factor (EGF) family of neuroprotective, hypoxia-inducible proteins released by astrocytes in CNS injuries. It was suggested that HB–EGF can replace fetal calf serum (FCS) in astrocyte cultures. We previously demonstrated that in contrast to standard 2D cell culture systems, Bioactive3D culture system, when used with FCS, minimizes the baseline activation of astrocytes and preserves their complex morphology. Here, we show that HB-EGF induced EGF receptor (EGFR) activation by Y1068 phosphorylation, Mapk/Erk pathway activation, and led to an increase in cell proliferation, more prominent in Bioactive3D than in 2D cultures. HB-EGF changed morphology of 2D and Bioactive3D cultured astrocytes toward a radial glia-like phenotype and induced the expression of intermediate filament and progenitor cell marker protein nestin. Glial fibrillary acidic protein (GFAP) and vimentin protein expression was unaffected. RT-qPCR analysis demonstrated that HB-EGF affected the expression of Notch signaling pathway genes, implying a role for the Notch signaling in HB-EGF-mediated astrocyte response. HB-EGF can be used as a FCS replacement for astrocyte expansion and in vitro experimentation both in 2D and Bioactive3D culture systems; however, caution should be exercised since it appears to induce partial de-differentiation of astrocytes.HB-EGF (heparin-binding EGF-like growth factor) was previously suggested to replace serum, a common and undefined component in primary astrocyte cultures. We show that both in standard 2D and in our newly developed Bioactive3D culture system, HB-EGF affects astrocyte morphology, proliferation, gene/protein expression and leads to partial de-differentiation of astrocytes. Thus, HB-EGF should only be used with caution as a serum replacement in astrocyte cultures.
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| 317. |
- Qin, Yiheng, 1987, et al.
(författare)
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Organic Thin-Film Transistors with Anodized Gate Dielectric Patterned by Self-Aligned Embossing on Flexible Substrates
- 2012
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 22:6, s. 1209-1214
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Tidskriftsartikel (refereegranskat)abstract
- An upscalable, self-aligned patterning technique for manufacturing high- performance, flexible organic thin-film transistors is presented. The structures are self-aligned using a single-step, multi-level hot embossing process. In combination with defect-free anodized aluminum oxide as a gate dielectric, transistors on foil with channel lengths down to 5 mu m are realized with high reproducibility. Resulting on-off ratios of 4 x 106 and mobilities as high as 0.5 cm2 V-1 s-1 are achieved, indicating a stable process with potential to large-area production with even much smaller structures.
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| 318. |
- Raugi, Fabien, et al.
(författare)
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Flow Behaviour of Anisotropic Conductive Adhesive Film during COG Bonding Process in Flat Panel Display Assembly
- 2006
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Ingår i: 1st Electronics Systemintegration Technology Conference; Dresden, Saxony; Germany; 5 September 2006 through 7 September 2006. - 1424405521 ; , s. 828-833
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Konferensbidrag (refereegranskat)abstract
- Anisotropic conductive adhesives have emerged as an important joining technology in a number of significant application areas, such as fine pitched driver IC for flat panel display assembly and smart cards. In the past research work in this field, it has been shown that the pressure distribution and adhesive compression flow predicted using the Newtonian and non-Newtonian FV models both agree closely with those from the previously developed analytical model. This gives confidence in the FV modelling approach and therefore the results predicted more complex situations which the analytical model cannot address. These results further confirm that a more sophisticated modelling approach is required in order to allow a full understanding about the effects of the assembly process on its final properties when the adhesive flows. An analytical model has been proposed in this paper which takes into account more complex bump geometry and can be used to predict the velocity and pressure drop distribution through the entire chip during the COG bonding process. The analytical solution is followed by the finite element modelling, which agrees well with the analytically predicted solution.
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| 319. |
- Rui, Manman, et al.
(författare)
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TiO2 Nanoparticles Functionalized Sn/3.0Ag/0.5Cu Lead-free Solder
- 2012
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Ingår i: Proceedings of IEEE CPMT 2012 International Conference on Electronic Packaging Technology & High Density Packaging. - 9781467316804 ; , s. 203-207
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Konferensbidrag (refereegranskat)abstract
- As the development of micro-systems moves towards higher speed and miniaturization, the requirement for interconnection density increases significantly. However, the use of conventional solders will be limited as the increasing I/O density lowers the pitches to very small size. Recently, there have been great developments in nano-composite solders. This paper investigated the influence of nano-titanium dioxide (TiO 2 ) of 99.9% purity on the wettability, micro-structural, melting and mechanical properties of Sn/3.0Ag/0.5Cu. The composite solder was prepared by mechanically mixing solder paste with TiO 2 nanoparticles for 30 minutes. The TiO 2 nanoparticles, with average diameter of 10 nm, were manufactured by precipitation. The solder paste was SAC305 Type 4. After reflow soldering the wetting angle was measured. The microstructure of the composite solders and TiO 2 was studied by means of scanning electron microscope (SEM). An optical microscope (OM) was employed to observe the fracture mode after shear test. A pull test was performed to investigate the shear strength of all samples with composite solders between two PCBs with Sn coating, both before and after thermal cycling (TC) with range between -40°C and 85°C. Differential scanning caborimetry (DSC) was adopted to analyze the melting point of composite solders. The results indicate that when the TiO 2 content increased from 0.5% to 2%, the wettability of the solder improved, which resulted in higher shear strength and better mechanical behavior. © 2012 IEEE.
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| 320. |
- Satwara, Maulik, 1990, et al.
(författare)
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Finite element analysis of bond line thickness and fiber distribution in solder based thermal interface materials
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 167-171
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Konferensbidrag (refereegranskat)abstract
- As microelectronic devices continue to decrease in size, failure of these devices is commonly attributed to ineffectual thermal management. Hence, increased thermal failures at elevated temperature has accounted for some of their reliability concerns and expected to be a major bottleneck for future development of microelectronics. For the thermal management, solder based materials give a better performance as thermal interface materials (TIM). However, these materials have a marginal reliability due to their higher Young's modulus. Therefore new type of solder based nano polymer composite (SMNPC) material is introduced. The SMNPC is composed of Sn-Ag-Cu (SAC) infiltrated through a silver coated PA6, 6 polymer fiber mesh to address electrical, thermal and mechanical challenges. In this work, finite element modeling was employed to investigate the thermal and mechanical properties of the composite material by varying polymer distribution, total volume of polymer and bond fine thickness (BLT). The composite is demonstrated to possess high heat transfer capability and lower elastic modulus as shown in Figure 1. All the results demonstrate that the developed SMNPC is proved a good alternative for conventional TIMs to improve thermal and mechanical properties.
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