| 1. |
- Abgrall, N., et al.
(författare)
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The large enriched germanium experiment for neutrinoless double beta decay (LEGEND)
- 2017
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Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 1894
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Konferensbidrag (refereegranskat)abstract
- The observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neu-trinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results.
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| 2. |
- Wang, Nan, et al.
(författare)
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Highly thermal conductive and electrically insulated graphene based thermal interface material with long-term reliability
- 2019
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2019-May, s. 1564-1568
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Konferensbidrag (refereegranskat)abstract
- High density packaging in combination with increased transistor integration inevitably leads to challenging power densities in terms of thermal management. The conventional TIMs that are widely used in the microelectronic industry today are experiencing more and more stress due to their limited thermal performance and poor reliability. Composed by particle laden polymer matrix, thermal conductivity (K) of conventional TIMs is generally limited to 5 W/mK, and such values can be even lower for electrically insulated TIMs. Conventional TIMs also suffer from severe pump-out and dry-out failures, which brought great threat to the performance and lifetime of the electronic devices. Here, we solve these problems by applying a novel highly thermal conductive, electrically insulated and reliable graphene based TIMs (I-GTs). Composed by vertical graphene structures, I-GTs provide a continuous heat pathway from top to bottom, which enables superfast heat dissipation at through-plane direction. The highest bulk through-plane thermal conductivity of the conductive body can reach up to 1000 W/mK, which is orders of magnitude higher than conventional TIMs, and even outperforms the pure indium TIMs by over ten times. The highly flexible and foldable nature of I-GT enables at least 100% compressibility upon small applied pressures. As excellent gap fillers, I-GT can provide complete physical contact between two surfaces and thereby minimize the contact resistance to heat flow. The measured minimum thermal resistance for I-GTs reaches about 30 Kmm2/W. Such values are significantly higher than the randomly dispersed composites presented above. To ensure fully electrical insulation, a smooth and soft adhesive layer with a thickness of few microns was coated on the surface of I-GT. The breakdown voltage of I-GT reaches up to 950 V. Thermal cycling test shows the highly stable nature of I-GT. The good compressibility and elasticity of I-GT ensures continued proper TIM contact with substrates, which counteracts the effect of internal stress induced by the mismatch of coefficient of thermal expansion (CTE) during temperature cycling. In addition, the I-GTs have the advantages of low density and good maintainability. The resulting I-GTs thus opens new opportunities for addressing large heat dissipation issues for form-factor driven electronics and other high power driven systems.
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| 3. |
- Zhang, Maomao, et al.
(författare)
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Effect of pressure during graphitization on mechanical properties of graphene films
- 2019
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Ingår i: 2019 20th International Conference on Electronic Packaging Technology, ICEPT 2019.
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Konferensbidrag (refereegranskat)abstract
- Graphene films (GFs) can be used in the field of electronics cooling, owing to many outstanding properties. In the present paper, GFs samples were graphitized at different pressures to study their effect on the mechanical properties. The elastic modulus and hardness of GFs were measured by nanoindentation and the tensile strength of GFs were obtained by stretching GFs in a tensile tester. Meanwhile, GFs were characterized by X-ray diffraction(XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. The results show that the modulus, hardness and tensile strength of GFs were strongly influenced by the defect and wrinkles among other things.
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| 4. |
- Chen, S., et al.
(författare)
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An overview of carbon nanotubes based interconnects for microelectronic packaging
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 113-119
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Konferensbidrag (refereegranskat)abstract
- Owing to the great demand in more functions and miniaturization in microelectronic packaging, the dimensions of interconnects has decreased extremely, which has resulted in electrical, thermal, and mechanical reliability issues. To address these issues, carbon nanotube (CNT) has been selected as a promising alternative material for the interconnects in packaging due to its large current density, high thermal conductivity, great flexibility, and low coefficient of thermal expansion (CTE). In this paper, the development of CNTs based vertical interconnects was reviewed. However, the resistivity of CNTs based interconnects was much higher than that of copper interconnects. Thus, this review focused on the resistivity of CNTs-based interconnects in different fabrication process and pointed out what improves the resistivity. In the future, CNTs-Cu nanocomposite with unique properties could be the suitable material for bumps to reduce the resistivity of CNTs based bumps further.
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| 5. |
- Huang, S., et al.
(författare)
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Improved reliability of electrically conductive adhesives joints on Cu-Plated PCB substrate enhanced by graphene protection barrier
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 143-146
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Konferensbidrag (refereegranskat)abstract
- Graphene protection barrier was introduced to the interface between the ECAs and Cu-plated wire to enhance the reliability of the ECAs joints on Cu-Plated PCB substrate due to its excellent properties of impermeability to all gases/salts as well as its thermal/chemical stability. The results of shear test indicated graphene protection barrier can improve the shear strength of the ECAs joints on Cu-plated PCB substrate by almost 22% after 500 hours high temperature and high humidity cyclic test. Characterizations by optical microscope and XPS were further performed to explain the mechanism. To sum up, it can be believed that the graphene protection barrier can dramatically enhance the reliability of the ECAs joints on Cu-Plated PCB substrate.
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| 6. |
- Wang, Nan, et al.
(författare)
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Light-weight Compressible and Highly Thermal Conductive Graphene-based Thermal Interface Material
- 2018
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Ingår i: 2018 7th Electronic System-Integration Technology Conference (ESTC). - 9781538668146
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Konferensbidrag (refereegranskat)abstract
- High density packaging in combination with increased transistor integration inevitably leads to challenging power densities in terms of thermal management. Thermal interface materials (TIMs) play a key role in thermal management by transferring heat from the surface of power devices. The conventional TIMs used in the microelectronics industry today basically are particle laden polymer matrix composites, which have the advantages of good reliability and ease of use. However, the thermal conductivity (K) of these composites is generally limited to 10 W/mK, which is hard to meet the goal for efficient thermal management in power devices. Here, we solve the problem by applying a novel highly thermal conductive and compressible graphene based TIMs (GTs). Composed by vertical graphene structures, GTs provide a continuous high thermal conductivity phase along the path of thermal transport, which lead to outstanding thermal properties. By tailoring ratios of graphene in the polymer binder, bulk thermal conductivity of GTs can be varied from 50 to 1000 W/mK. This result isorders of magnitude higher than conventional TIMs, and even outperforms the pure indium TIMs by over ten times. Meanwhile, the highly flexible and foldable nature of vertical graphene enables at least 20% compressibility of the GTs upon small applied pressures (≤ 400 KPa). As excellent gap fillers, GT can provide complete physical contact between two surfaces and thereby minimize the contact resistance to heat flow. The measured minimum thermal resistance and maximum effective thermal conductivity for GTs reaches to ∼ Kmm2/W and ∼ W/mK, respectively. Such values are significantly higher than the randomly dispersed composites presented above, and show almost comparable thermal performance as pure indium bonding. In addition, the GTs has more advantages than indium/solder bonding, including low weight (density <2g/cm3), low complexity during assembly and maintainability. The resulting GTs thus opens new opportunities for addressing large heat dissipation issues both in through-plane and in-plane directions for form-factor driven electronics and other high power driven systems.
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| 7. |
- Wang, Nan, 1988, et al.
(författare)
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Tailoring the Thermal and Mechanical Properties of Graphene Film by Structural Engineering
- 2018
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 14:29
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Tidskriftsartikel (refereegranskat)abstract
- Due to substantial phonon scattering induced by various structural defects, the in-plane thermal conductivity (K) of graphene films (GFs) is still inferior to the commercial pyrolytic graphite sheet (PGS). Here, the problem is solved by engineering the structures of GFs in the aspects of grain size, film alignment, and thickness, and interlayer binding energy. The maximum K of GFs reaches to 3200 W m−1K−1and outperforms PGS by 60%. The superior K of GFs is strongly related to its large and intact grains, which are over four times larger than the best PGS. The large smooth features about 11 µm and good layer alignment of GFs also benefit on reducing phonon scattering induced by wrinkles/defects. In addition, the presence of substantial turbostratic-stacking graphene is found up to 37% in thin GFs. The lacking of order in turbostratic-stacking graphene leads to very weak interlayer binding energy, which can significantly decrease the phonon interfacial scattering. The GFs also demonstrate excellent flexibility and high tensile strength, which is about three times higher than PGS. Therefore, GFs with optimized structures and properties show great potentials in thermal management of form-factor-driven electronics and other high-power-driven systems.
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| 8. |
- Yuan, G., et al.
(författare)
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Graphene-based heat spreading materials for electronics packaging applications
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 172-174
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Konferensbidrag (refereegranskat)abstract
- Graphene-based heat spreading materials, including graphene-based film (GBF) and graphene-based electrically conductive adhesive (G-CA), were applied to electronics packaging. The thermal performances of GBF and G-CA were analyzed by resistance temperature detector (RTD) and thermal infrared imager. When the chip was covered by GBF and G-CA, the temperature of hotspot could be reduced by 3.1°C, at heat flux of 580 W/cm2. To analyze the thermal performances of G-CA and GBF in 3D electronics packaging, the distribution of temperature and temperature profiles on the top surface of chip were analyzed by COMSOL. Both of GBF and G-CA could obviously reduce the temperature of hotspot on the top surface of chip, compared with that on the bare chip. With G-CA and GBF, the temperature of hotspot could be reduced by 8°C. It suggests that both of G-CA and GBF are good heat spreading materials for electronics packaging application.
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