| 361. |
- 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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| 362. |
- Wang, Nan, 1988, et al.
(författare)
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Reliability investigation of nano-enhanced thermal conductive adhesives
- 2012
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Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781467321983
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Konferensbidrag (refereegranskat)abstract
- This paper deals with silver (Ag) coated silicon carbide nanoparticles (SiC@Ag NPs) for thermal conductive interconnect and die attach applications.
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| 363. |
- Wang, Nan, 1988, et al.
(författare)
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Synthesis of highly conductive and mechanically strong silver coated silk bundles for flexible electronic applications
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226
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Konferensbidrag (refereegranskat)abstract
- Portable and wearable electronics that feature lightweight, highly compact and low cost can enable a wide variety of new applications, such as paper-like displays, smart clothing, stretchable solar cells, camera eyes and biomedical sensors. The applications for these types of system require conductive materials that are both highly conductive and mechanically robust enough to have large deformation stability. In this work, silver coated silk hybrid fibers were fabricated to meet the above requirements. As one of natural polymers used by human at the earliest stage, silk fiber has many advantages, such as light weight, good comfortability and mechanically robust. The chemical structure of silk fiber is composed of two main proteins, fibroin and sericin. Importantly, the sericin layer shows the special sol-gel property under temperature difference and therefore can be used for adhesion between the deposited silver nanoparticles and the surface of silk bundles. The silver coating layer on the surface of silk fiber can significantly improve the electrical conductivity of the hybrid structure to 1600 S/cm. Such a good conductivity is attributed to a complete silver shell structure. Importantly, the fabricated silver coated silk hybrid fibers demonstrated stable electro-mechanical properties under different structural deformations, including bending, compressing, and twisting. The observed stable and reliable electro-mechanical performance of silver coated silk hybrid fibers suggests the potential use of the material in future wearable and portable electronics.
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| 364. |
- 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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| 365. |
- Wang, Nan, et al.
(författare)
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Vertically Aligned Graphene-based Thermal Interface Material with High Thermal Conductivity
- 2018
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Ingår i: THERMINIC 2018 - 24th International Workshop on Thermal Investigations of ICs and Systems, Proceedings. - 9781538667590 ; , s. 285-288
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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. Here, a novel highly thermal conductive and lightweight graphene based thermal interface materials (GT) was developed for thermal management in power devices. Composed by vertically graphene structures, GTs provide a continuous high thermal conductivity phase along the path of thermal transport, which lead to outstanding thermal properties. The highest through-plane thermal conductivity GTs reaches to 1000 W/mK, which is orders of magnitude higher than conventional TIMs, and even outperforms the pure indium by over ten times. In addition, a thin layer of indium metal that coated on the surface of GTs can easily form alloys with many other metals at a relatively low reflow temperature. Therefore, GTs, as an excellent TIM, can provide complete physical contact between two surfaces with minimized the contact resistance. The measured total thermal resistance and effective thermal conductivity by using 300 mu m thick GTs as TIM between two copper blocks reaches to similar to 3.7 Kmm(2)/W and similar to 90 W/mK, respectively. Such values are significantly higher than the randomly dispersed composites presented above, and show even better thermal performance than pure indium bonding. In addition, GTs has more advantages than pure indium bonding, including low weight (density < 2 g/cm(3)), low complexity during assembly and maintainability. The resulting GTs thus opens new opportunities for addressing large heat dissipation issues in form-factor driven electronics and other high power driven systems.
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| 366. |
- Wang, Shun, et al.
(författare)
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MDS study on the adhesive heat transfer in micro-channel cooler
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5583859, s. 630-633
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Konferensbidrag (refereegranskat)abstract
- Carbon nanotube (CNT) can be used in micro-channel cooler construction due to its excellent thermal conductivity. When fabricating CNTs directly onto the chip, the chip could be damaged because of the high temperature required for CNT growth (about 750°C). As a solution, a transfer technique is developed where the desired carbon nanotube pattern can be obtained by taking off a pre-fabricated CNT forest with a designed adhesive, and the transfer process could make the chip or other components immune from the high temperature required for the CNT growth process. This process can also improve the bonding/adhesive strength. Nevertheless, the use of adhesive in the CNT-based micro-channel structure might affect the thermal conduction of the cooling system. In particular, the heat transfer between the heat generator and the CNT fin in the micro-channel cooler shall be evaluated. In this paper the thermal conductivity of the adhesive is studied by molecular dynamics simulation (MDS). The adhesive considered in the present MDS model consists of the epoxy and the curing agent. After the curing process, the epoxy molecules construct a network, which is established in the epoxy matrix generation before the simulation. Nonequilibrium Molecular Dynamics Method (NEMD) is adopted in the modeling and periodic boundary conditions are applied. Furthermore, the heat transfer through CNT and adhesive interface is simulated in this work based on the adhesive results, which can provide information for future macro-analysis of the thermal performance of the CNT microchannel cooler. © 2010 IEEE.
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| 367. |
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| 368. |
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| 369. |
- Wang, Teng, 1983, et al.
(författare)
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Carbon-Nanotube Through-Silicon Via Interconnects for Three-Dimensional Integration
- 2011
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:16, s. 2313-2317
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Tidskriftsartikel (refereegranskat)abstract
- Interconnection of carbon-nanotube (CNT)-filled through-silicon vias is demonstrated through an easy-to-implement process based on mechanical fastening. Direct CNT-to-CNT and CNT-to-Au contacts are realized at the microscale, and their specific contact resistances extracted from electrical measurements are approximately 1.2 × 10 -3 Ω cm 2 and 4.5 × 10 -4 Ω cm 2 , respectively. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 370. |
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