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  • Resultat 341-350 av 543
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341.
  • Nkansah, Amos, et al. (författare)
  • Reliability study on high thermally conductive graphene film as heat spreader in electronics cooling applications
  • 2018
  • Ingår i: IMAPS Nordic Annual Conference, NordPack 2018. ; 2018, s. 126-130
  • Konferensbidrag (refereegranskat)abstract
    • ―Graphene films (GFs) were fabricated and can be applied for dissipating heat from electronics such as portable electronics, laptops, light emitting diodes (LEDs) and other power electronics. These GFs are capable of transporting heat from electronic components. Due to its high thermal conductivity, these GFs are capable to transfer the heat efficiently from electronic component to the heat spreader or heat sink. The cooling failure of the GFs may lead to irreversible damage to the electronic system, hence it is necessary to investigate the long-term reliability of the film under certain harsh conditions. To evaluate the reliability of the GFs, the thermal cycles and moisture test are performed. The effect of temperature cycling (500 cycle) is tested by using an environmental oven with extreme temperatures. The effect of moisture penetration of the GFs is tested for 1024 hours. The thermal conductivity after these two test conditions does not change too much comparing to material before subjecting to test. The electrical conductivity value under the temperature cycling declined by 30% after 500 cycles and that of moisture test was improved by 20%. The result shows that the thermal conductivity of the GFs is quite stable under temperature cycle (500 cycles) and moisture test (1024 hours).
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342.
  • Nylander, Andreas, 1988, et al. (författare)
  • Covalent anchoring of carbon nanotube-based thermal interface materials using epoxy-silane monolayers
  • 2019
  • Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 9:3, s. 427-433
  • Tidskriftsartikel (refereegranskat)abstract
    • With the ever increasing demand for improved thermal management solutions in modern electronic devices, carbon nanotubes (CNTs) have been suggested as a candidate material for thermal interface materials (TIMs). However, the interfacial resistance between CNTs and matching substrate is huge due to poor interaction at the interface. With the help of chemical functionalization, these materials can be exploited to their full potential in TIM applications. By utilizing the epoxy-silane-based monolayers, covalent anchoring can be obtained between the CNTs and target substrate in order to bridge the interface, where high resistances, otherwise, would arise. To adapt CNT arrays to the epoxy chemistry, the CNTs have subsequently been subjected to nitrogen plasma in order to activate them with amino groups. The thermal interfaces were measured, and the thermal resistance was found to be decreased by 5% in comparison with the reference samples.
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343.
  • NYLANDER, ANDREAS, 1988, et al. (författare)
  • Current status and progress of organic functionalization of CNT based thermal interface materials for electronics cooling applications
  • 2017
  • Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging (NordPac). - 9781538630556 ; , s. 175-181
  • Konferensbidrag (refereegranskat)abstract
    • The development of integrated circuitry has resulted in cheaper and more efficient computers being available every year. Unfortunately, this development comes at the expense of an exponential increase of power density that scales with miniaturisation of transistors. To counteract the hot spot issue that arises and results in poor reliability and reduced lifetime of microsystems, thermal interface materials (TIMs) can be used. TIMs play a key role in thermal management of microsystems by providing efficient thermal pathways between surfaces. Vertically aligned carbon nanotubes (CNT) have been suggested as a potential material for such TIM applications due to the combination of their high thermal conductivity, which has been reported to reach over 3000 W/mK, and unique mechanical properties. However, due to the poor interaction between individual CNT strands and the contact surface, large contact resistances are commonly measured in these interfaces. One solution to this issue is to anchor the CNT by covalent bonding using chemical functionalization which allows phonon propagation through the interface. In this paper various chemical functionalization solutions from recent literature for CNT in TIM applications will be summarized. By comparing the results from these studies to other TIM systems, CNT array based TIM hold some promise with thermal interface resistance values reaching as low as 0.6mm2K/W. However, experimental results regarding the reliability of these solutions are still uncommon and should be a suitable area for further investigations.
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344.
  • Nylander, Andreas, 1988, et al. (författare)
  • Degradation of Carbon Nanotube Array Thermal Interface Materials through Thermal Aging: Effects of Bonding, Array Height, and Catalyst Oxidation
  • 2021
  • Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 13:26, s. 30992-31000
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbon nanotube (CNT) array thermal interface materials (TIMs) are promising candidates for high-performance applications in terms of thermal performance. However, in order to be useful in commercial applications, the reliability of the interfaces is an equally important parameter, which so far has not been thoroughly investigated. In this study, the reliability of CNT array TIMs is investigated through accelerated aging. The roles of CNT array height and substrate configuration are studied for their relative impact on thermal resistance degradation. After aging, the CNT catalyst is analyzed using X-ray photoelectron spectroscopy to evaluate chemical changes. The CNT-catalyst bond appears to degrade during aging but not to the extent that the TIM performance is compromised. On the other hand, coefficient of thermal expansion mismatch between surfaces creates strain that needs to be absorbed, which requires CNT arrays with sufficient height. Transfer and bonding of both CNT roots and tips also create more reliable interfaces. Crucially, we find that the CNT array height of most previously reported CNT array TIMs is not enough to prevent significant reliability problems.
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345.
  • NYLANDER, ANDREAS, 1988, et al. (författare)
  • Development of bulk-nanostructuring methods for BiSbTe Thermoelectric
  • 2016
  • Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226
  • Konferensbidrag (refereegranskat)abstract
    • Devices based upon the thermoelectric effect are sought after as a technology with the potential of miniaturizing power generation equipment and heat pumps. By the dawn of the 21th century and the advent of nanoengineering, these materials have gotten an upswing in attention from the scientific community with the methods and instruments that now are available to improve the materials figure of merit. In this paper three methods were investigated from their performance enhancing effects on BiSbTe: powder purification, mixed grains and electron filtering. By varying the parameters of each method, a performance improvement of 17% in respect to figure of merit was achieved by electron filtering.
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346.
  • Nylander, Andreas, 1988, et al. (författare)
  • Reliability investigation of a carbon nanotube array thermal interface material
  • 2019
  • Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 12:11
  • Tidskriftsartikel (refereegranskat)abstract
    • As feature density increases within microelectronics, so does the dissipated power density, which puts an increased demand on thermal management. Thermal interface materials (TIMs) are used at the interface between contacting surfaces to reduce the thermal resistance, and is a critical component within many electronics systems. Arrays of carbon nanotubes (CNTs) have gained significant interest for application as TIMs, due to the high thermal conductivity, no internal thermal contact resistances and an excellent conformability. While studies show excellent thermal performance, there has to date been no investigation into the reliability of CNT array TIMs. In this study, CNT array TIMs bonded with polymer to close a Si-Cu interface were subjected to thermal cycling. Thermal interface resistance measurements showed a large degradation of the thermal performance of the interface within the first 100 cycles. More detailed thermal investigation of the interface components showed that the connection between CNTs and catalyst substrate degrades during thermal cycling even in the absence of thermal expansion mismatch, and the nature of this degradation was further analyzed using X-ray photoelectron spectroscopy. This study indicates that the reliability will be an important consideration for further development and commercialization of CNT array TIMs.
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347.
  • Nylander, Andreas, 1988, et al. (författare)
  • RF properties of carbon nanotube / Copper composite through silicon via based CPW structure for 3D integrated circuits
  • 2019
  • Ingår i: 2019 IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019.
  • Konferensbidrag (refereegranskat)abstract
    • The development of integrated circuits (ICs) has seen exponential growth in performance over the last couple of decades and has pushed the boundaries for how we use our electronics in our daily lives. The scaling of ICs, and therefore also the performance development, is now starting to slow down when the physical designs are reaching critical dimensions where quantum effects starts to become noticeable. One proposed route to circumvent these issues for a continued scaling is based on the implementation of 3D integration by chip stacking for an increased miniaturization potential. Miniaturisation will soon also result in interconnect dimensions that surpass the mean free path (MFP) in Cu, the commonly used material for interconnects today, with a sharp increase in resistivity as a result. By changing the through silicon via (TSV) interconnect material from Cu to a carbon nanotube (CNT)/Cu composite, continued scaling can be ensured both in terms of electrical conductivity, ampacity and signal delays. Furthermore, a reduced skin effect can be achieved ensuring lower signal losses at higher RF frequencies making the CNT/Cu composite an ideal candidate to replace tranditional Cu interconnects. In this paper, we are demonstrating a coplanar waveguide (CPW) test structure using CNT/Cu filled TSVs connected to Au transmission lines on SiO2-passivated high resistivity Si substrates. The parasitic losses of the CNT/Cu TSV based CPW test structure were measured using a Sparameters test setup. The results showed that the CNT/Cu TSVs with affiliated contacts increased the signal losses up to S21 = -5.5 dB compared to Au reference transmission lines. These results are in line with previous results using CNT based TSVs and will serve as a basis for future improvements of CNT based interconnect technology for 3D integration.
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348.
  • Nylander, Andreas, 1988, et al. (författare)
  • Thermal Reliability Study of Polymer Bonded Carbon Nanotube Array Thermal Interface Materials
  • 2018
  • Ingår i: THERMINIC 2018 - 24th International Workshop on Thermal Investigations of ICs and Systems, Proceedings.
  • Konferensbidrag (refereegranskat)abstract
    • Following Moores law, the development of electronics has led to an exponential increase of transistor density over the last couple of decades. Unfortunately, this trend also gives an increased heat power density in active components. Thermal interface materials (TIMs) are used to decrease the thermal resistance in thermal packages by filling out air gaps that naturally form there. TIMs are at the same time identified as a bottleneck due to their relatively low thermal conductivity. Carbon nanotubes (CNTs) are proposed as a future material for TIMs due to their high thermal conductivity and conformable nature. However, no reliability studies for CNT array TIMs can be found in literature that would demonstrate how these types of interfaces would perform. This is to the authors best knowledge the first reported study on thermal reliability for a CNT array TIM, which will be an important step towards a market realisation.
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  • Resultat 341-350 av 543
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