| 1. |
- Hansson, Josef, 1991, et al.
(författare)
-
Synthesis of a Graphene Carbon Nanotube Hybrid Film by Joule Self-heating CVD for Thermal Applications
- 2018
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2018-May
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Konferensbidrag (refereegranskat)abstract
- Hybrid films based on vertically aligned carbon nanotubes (CNTs) on graphene or graphite sheets have been proposed for application as thermal interface materials and micro heat sinks. However, the fabrication of these materials are limited to small scale, expensive and complicated chemical vapor deposition (CVD) for CNT synthesis. We present a new method for direct growth of CNTs on one or both sides of a thin graphene film (GF) using joule self-heating of the graphene film to provide the necessary heat for the thermal breakdown of carbon feedstock in a CVD process. The resulting CNT forests show good density and alignment consistent with regular CVD synthesis processes on silicon surfaces. The resulting double sided GF/CNT hybrid film is directly applicable as a thermal pad. The CNT forest has a thermal conductivity of 30 W/mK, measured by pulsed photothermal reflectance, and the total thermal interface resistance between aluminum blocks was measured to be 60 Kmm 2 /W using an ASTM D5470 compliant 1-D measurement setup. This method of directly synthesizing CNTs on graphene films is more energy efficient and capable of larger volume production compared to traditional CVD methods. It is also compatible with scaling up towards continuous roll-to-roll production for large scale commercial production, one of the major limitations preventing CVD-grown CNTs from commercial applications
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| 2. |
- Jiang, Di, 1983, et al.
(författare)
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Embedded Fin-Like Metal/CNT Hybrid Structures for Flexible and Transparent Conductors
- 2016
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 12:11, s. 1521-1526
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, an embedded fin-like metal-coated carbon nanotube (Fin-M/CNT) structure is demonstrated for flexible and transparent conductor wire applications. Embedded in a polydimethylsiloxane polymeric substrate, Fin-M/CNT wires with a minimum width of 5 μm and a minimum pitch of 10 μm have been achieved. Direct current resistances of single Fin-M/CNT wires, where the supporting CNT structures have been covered by Ti/Al/Au metal coatings of different thicknesses, have been measured. The high aspect ratio of the fin-like structures not only improves the adhesion between the wires and the polymeric substrate, but also yields a low resistance at a small surface footprint. In addition, transparent Fin-M/CNT grid lines with hexagonal patterns, with a sheet resistance of as low as 45 Ω sq−1, have been achieved at an optical transmittance of 88%. The robustness of the Fin-M/CNT structures has been demonstrated in bending tests up to 500 cycles and no significant changes in wire resistances are observed.
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| 3. |
- Nylander, Andreas, 1988, et al.
(författare)
-
RF properties of carbon nanotube / Copper composite through silicon via based CPW structure for 3D integrated circuits
- 2019
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Ingår i: 2019 IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019.
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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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| 4. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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High porosity and light weight graphene foam heat sink and phase change material container for thermal management
- 2020
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42
-
Tidskriftsartikel (refereegranskat)abstract
- During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m(-1)K(-1), while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.
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| 5. |
- Fazi, Andrea, 1992, et al.
(författare)
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Multiple growth of graphene from a pre-dissolved carbon source
- 2020
-
Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:34, s. 345601-
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Tidskriftsartikel (refereegranskat)abstract
- Mono- to few-layer graphene materials are successfully synthesized multiple times using Cu-Ni alloy as a catalyst after a single-chemical vapor deposition (CVD) process. The multiple synthesis is realized by extracting carbon source pre-dissolved in the catalyst substrate. Firstly, graphene is grown by the CVD method on Cu-Ni catalyst substrates. Secondly, the same Cu-Nicatalyst foils are annealed, in absence of any external carbon precursor, to grow graphene using the carbon atoms pre-dissolved in the catalyst during the CVD process. This annealing process is repeated to synthesize graphene successfully until carbon is exhausted in the Cu-Ni foils. After the CVD growth and each annealing growth process, the as-grown graphene is removed using a bubbling transfer method. A wide range of characterizations are performed to examine the quality of the obtained graphene material and to monitor the carbon concentration in the catalyst substrates. Results show that graphene from each annealing growth process possesses a similar quality, which confirmed the good reproducibility of the method. This technique brings great freedom to graphene growth and applications, and it could be also used for other 2D material synthesis.
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| 6. |
- Hansson, Josef, 1991, et al.
(författare)
-
Bipolar electrochemical capacitors using double-sided carbon nanotubes on graphite electrodes
- 2020
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 451
-
Tidskriftsartikel (refereegranskat)abstract
- The electrochemical capacitor (EC) is a key enabler for the miniaturized self-powered systems expected to become ubiquitous with the advent of the internet-of-things (IoT). Vertically aligned carbon nanotubes (VACNTs) on graphite holds promise as electrodes for compact and low-loss ECs. However, as with all ECs, the operating voltage is low, and miniaturization of higher voltage devices necessitates a bipolar design. In this paper, we demonstrate a bipolar EC using graphite/VACNTs electrodes fabricated using a joule heating chemical vapor deposition (CVD) setup. The constructed EC contains one layer of double-sided VACNTs on graphite as bipolar electrode. Compared to a series connection of two individual devices, the bipolar EC has 22% boost in volumetric energy density. More significant boost is envisaged for stacking more bipolar electrode layers. The energy enhancement is achieved without aggravating self-discharge (71.2% retention after 1 h), and at no sacrifice of cycling stability (96.7% over 50000 cycles) owing to uniform growth of VACNTs and thus eliminating cell imbalance problems.
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| 7. |
- Hansson, Josef, 1991, et al.
(författare)
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Effects of high temperature treatment of carbon nanotube arrays on graphite : Increased crystallinity, anchoring and inter-tube bonding
- 2020
-
Ingår i: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 31:45
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal treatment of carbon nanotubes (CNTs) can significantly improve their mechanical, electrical and thermal properties due to reduced defects and increased crystallinity. In this work we investigate the effect of annealing at 3000 degrees C of vertically aligned CNT arrays synthesized by chemical vapor deposition (CVD) on graphite. Raman measurements show a drastically reduced amount of defects and, together with transmission electron microscope (TEM) diffraction measurements, an increased average crystallite size of around 50%, which corresponds to a 124% increase in Young's modulus. We also find a tendency for CNTs to bond to each other with van der Waals (vdW) forces, which causes individual CNTs to closely align with each other. This bonding causes a densification effect on the entire CNT array, which appears at temperatures >1000 degrees C. The densification onset temperature corresponds to the thermal decomposition of oxygen containing functional groups, which otherwise prevents close enough contact for vdW bonding. Finally, the remaining CVD catalyst on the bottom of the CNT array is evaporated during annealing, enabling direct anchoring of the CNTs to the underlying graphite substrate.
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| 8. |
- Jing, Lin, et al.
(författare)
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Thermal Conductivity Enhancement of Coaxial Carbon@Boron Nitride Nanotube Arrays
- 2017
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:17, s. 14555-14560
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the thermal conductivity enhancement of the vertically aligned carbon nanotube (CNT) arrays (from ?15.5 to 29.5 W/mK, ?90% increase) by encapsulating outer boron nitride nanotube (BNNT, 0.97 nm-thick with ?3-4 walls). The heat transfer enhancement mechanism of the coaxial C@BNNT was further revealed by molecular dynamics simulations. Because of their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT. This work provides deep insights into tailoring the heat transfer of arbitrary CNT arrays and will enable their broader applications as thermal interface material.
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| 9. |
- Li, Hangxi, 1994, et al.
(författare)
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Experimentally Verified, Fast Analytic, and Numerical Design of Superconducting Resonators in Flip-Chip Architectures
- 2023
-
Ingår i: IEEE Transactions on Quantum Engineering. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- In superconducting quantum processors, the predictability of device parameters is of increasing importance as many laboratories scale up their systems to larger sizes in a 3-D-integrated architecture. In particular, the properties of superconducting resonators must be controlled well to ensure high-fidelity multiplexed readout of qubits. Here, we present a method, based on conformal mapping techniques, to predict a resonator's parameters directly from its 2-D cross-section, without computationally heavy and time-consuming 3-D simulation. We demonstrate the method's validity by comparing the calculated resonator frequency and coupling quality factor with those obtained through 3-D finite-element-method simulation and by measurement of 15 resonators in a flip-chip-integrated architecture. We achieve a discrepancy of less than 2% between designed and measured frequencies for 6-GHz resonators. We also propose a design method that reduces the sensitivity of the resonant frequency to variations in the interchip spacing.
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| 10. |
- Liu, Ya, 1991, et al.
(författare)
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Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader
- 2019
-
Ingår i: Proceedings - 2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019. ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- Thermally conductive materials with electrically insulating properties have been extensively investigated for thermal management of electronic devices. The combined properties of high thermal conductivity, structural stability, corrosion resistance and electric resistivity make hexagonal boron nitride (h-BN) a promising candidate for this purpose. Theoretical studies have revealed that h-BN has a high in-plane thermal conductivity up to 400-800 W m-1 K-1 at room temperature. However, it is still a big challenge to achieve high thermally conductive h-BN thick films that are commercially feasible due to its poor mechanical properties. On the other hand, many polymers exhibit advantages for flexibility. Thus, combining the merits of polymer and the high thermal conductivity of h-BN particles is considered as a promising solution for this issue. In this work, orientated PVP/h-BN films were prepared by electrospinning and a subsequent mechanical pressing process. With the optimized h-BN loading, a PVP/h-BN composite film with up to 22 W m-1 K-1 and 0.485 W m-1 K-1 for in-plane and through-plane thermal conductivity can be achieved, respectively. We believe this work can help accelerate the development of h-BN for thermal management applications.
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| 11. |
- Liu, Ya, 1991, et al.
(författare)
-
Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader
- 2019
-
Ingår i: Advancing Microelectronics. - 2222-8748. ; 2019:NOR, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Thermally conductive materials with electrically insulating properties have been extensively investigated for thermal management of electronic devices. The combined properties of high thermal conductivity, structural stability, corrosion resistance and electric resistivity make hexagonal boron nitride (h-BN) a promising candidate for this purpose. Theoretical studies have revealed that h-BN has a high in-plane thermal conductivity up to 400 - 800 W m−1 K−1 at room temperature. However, it is still a big challenge to achieve high thermally conductive h-BN thick films that are commercially feasible due to its poor mechanical properties. On the other hand, many polymers exhibit advantages for flexibility. Thus, combining the merits of polymer and the high thermal conductivity of h-BN particles is considered as a promising solution for this issue. In this work, orientated PVP/h-BN films were prepared by electrospinning and a subsequent mechanical pressing process. With the optimized h-BN loading, a PVP/h-BN composite film with up to 22 W m-1 K-1 and 0.485 W m-1 K-1 for in-plane and through-plane thermal conductivity can be achieved, respectively. We believe this work can help accelerate the development of h-BN for thermal management applications.
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| 12. |
- Nylander, Andreas, 1988, et al.
(författare)
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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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| 13. |
- 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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| 14. |
- 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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| 15. |
- NYLANDER, ANDREAS, 1988, et al.
(författare)
-
Development of bulk-nanostructuring methods for BiSbTe Thermoelectric
- 2016
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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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| 16. |
- NYLANDER, ANDREAS, 1988
(författare)
-
Fabrication and Characterisation of Carbon Nanotube Array Thermal Interface Materials
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The performance of electronic devices has long been limited by thermal dissipation which will result in device failure if not handled properly. The next generation of integrated circuit (IC) devices will feature new packaging technologies like heterogeneous integration as well as 3D stacking which entails additional emphasis on the thermal management solutions employed. Therefore, new materials are in demand to meet the increased thermal dissipation requirements to allow continued scaling in terms of cost per performance and increased device reliability. The largest bottleneck in thermal dissipation originates from thermal interfaces between different surfaces. For this purpose thermal interface materials (TIMs) are used to conform and bridge the interface and thereby alleviate the thermal dissipation restrictions in the interface. However, commercially available TIMs are either of metallic or polymeric nature which implies a compromise between thermal performance and reliability. Carbon nanotube (CNT) arrays have been suggested as a future potential material in order to achieve a TIM with superior thermal and mechanical properties that would ensure simultaneous high thermal performance and reliability. However, proper bonding solutions are still to be developed in order to apply CNT array TIMs in thermal dissipation applications and to ensure a successful market realisation. This thesis first outlines the field by presenting a thorough literature review of organic functionalization methods for CNT array TIMs. Three different approaches are identified: polymer embedding, polymer bonding and self-assembly based functionalization. The thesis then presents two experimental studies on CNT array TIMs. The first focuses on the development and characterisation of a CNT array TIM using a novel self-assembly based bonding method by employing epoxy chemistry for covalent anchoring. The second part focuses on a reliability study of a CNT array TIM assembled using a polymer bonding method, which is an aspect that previously has been overlooked. The results from the reliability study gave indications that the mechanical bonding between the CNT array and the growth substrate was susceptible for rapid degradation and further research is required in this field to address this challenge.
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| 17. |
- Nylander, Andreas, 1988
(författare)
-
Fundamental Characterization of Low Dimensional Carbon Nanomaterials for 3D Electronics Packaging
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transistor miniaturization has over the last half century paved the way for higher value electronics every year along an exponential pace known as 'Moore's law'. Now, as the industry is reaching transistor features that no longer makes economic sense, this way of developing integrated circuits (ICs) is coming to its definitive end. As a solution to this problem, the industry is moving toward higher hanging fruits that can enable larger sets of functionalities and ensuring a sustained performance increase to continue delivering more cost-effective ICs every product cycle. These design strategies beyond Moore's law put emphasis on 3D stacking and heterogeneous integration, which if implemented correctly, will deliver a continued development of ICs for a foreseeable future. However, this way of building semiconductor systems does bring new issues to the table as this generation of devices will place additional demands on materials to be successful. The international roadmap of devices and systems (IRDS) highlights the need for improved materials to remove bottlenecks in contemporary as well as future systems in terms of thermal dissipation and interconnect performance. For this very purpose, low dimensional carbon nanomaterials such as graphene and carbon nanotubes (CNTs) are suggested as potential candidates due to their superior thermal, electrical and mechanical properties. Therefore, a successful implementation of these materials will ensure a continued performance to cost development of IC devices. This thesis presents a research study on some fundamental materials growth and reliability aspects of low dimensional carbon based thermal interface materials (TIMs) and interconnects for electronics packaging applications. Novel TIMs and interconnects based on CNT arrays and graphene are fabricated and investigated for their thermal resistance contributions as well electrical performance. The materials are studied and optimized with the support of chemical and structural characterization. Furthermore, a reliability study was performed which found delamination issues in CNT array TIMs due to high strains from thermal expansion mismatches. This study concludes that CNT length is an important factor when designing CNT based systems and the results show that by further interface engineering, reliability can be substantially improved with maintained thermal dissipation and electrical performance. Additionally, a heat treatment study was made that enables improvement of the bulk crystallinity of the materials which will enable even better performance in future applications.
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| 18. |
- 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
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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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| 19. |
- 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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| 20. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
-
Graphene-coated copper nanoparticles for thermal conductivity enhancement in water-based nanofluid
- 2019
-
Ingår i: 2019 22nd European Microelectronics and Packaging Conference and Exhibition, EMPC 2019.
-
Konferensbidrag (refereegranskat)abstract
- The integration of metallic nanoparticlcs (NPs) in nanofluids was found to enhance the thermal properties of the mixture and affect the rheological properties of the base liquid. However, due to their size and electrochemical properties, the added metallic nanoparticlcs have a limited contribution to the thermal transport and their stability hinders further development of such an approach in thermal management. We investigated in this work the effect of the presence of graphene as a coating layer of on copper nanoparticles dispersed in water as a water-based graphene coated copper nanofluid. Electronics microscopy was deployed to investigate the presence and the number of layers of graphene around the metallic nanoparticles. The observed particles were found to have a spherical morphology with a full coating of several layers. The elemental characterization of the NPs showed the presence of graphitic structure confirming the nature of the coating. The thermal properties of the fluid were estimated versus loading fraction of graphene coated nanoparticles and temperature using a hot disk method. An increase of up to 17% was recorded at a concentration of 0.1 w.% at 45deg C. Dynamic Light Scattering and zeta potential were used to investigate the electrochemical properties of the produced nanoparticles. The particles were found to present weak surface charges corresponding to a zeta potential of 6mV that promoted the segregation of the NPs. The rheological properties of the resulted fluids were investigated using viscometer. The NFs were found to have a Newtonian behaviour.
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| 21. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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Graphene Oxide and Nitrogen-Doped Graphene Coated Copper Nanoparticles in Water-Based Nanofluids for Thermal Management in Electronics
- 2022
-
Ingår i: JOURNAL OF NANOFLUIDS. - : American Scientific Publishers. - 2169-432X .- 2169-4338. ; 11:1, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) and nitrogen-doped graphene (NG) coated copper nanoparticles (NPs) have been developed in this work and investigated as nanofiller for water as Heat Transfer Fluids (HTFs). The morphology and composition of the coating were characterized to confirm the presence of functional groups and the nitrogen-doping of the graphene coating. Different fractions of the two types of coated nanoparticles NPs between 0.1 and 10 wt.% were dispersed in water. The thermal conductivity of the dispersions was evaluated at temperatures between 20 and 50 degrees C. A positive correlation between the thermal conductivity of the HTFs and the fraction and temperature are observed as a result of the increase of the solid phase contribution into the heat transfer. At a concentration of 0.5 wt.%, the thermal conductivity of the NG-CuNPs nanofluid reached its maximum increase of 78%, compared to a 13% increase in the case of GO-CuNPs. However, due to the poor stability of the NG-CuNPs, further increase of the solid phase did not result in any additional improvement. In contrast, the thermal conductivity of the GO-based dispersion resulted in a 103% enhancement at 10 wt.% at a temperature of 50 degrees C.
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