| 1. |
- Huang, Shirong, et al.
(författare)
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Infrared Emissivity Measurement for Vertically Aligned Multiwall Carbon Nanotubes (CNTs) Based Heat Spreader Applied in High Power Electronics Packaging
- 2016
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Ingår i: 6th Electronic System-integration Technology Conference (ESTC 2016). - 9781509014026 ; , s. Article no 7764696-
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Konferensbidrag (refereegranskat)abstract
- Vertically-aligned multiwall carbon nanotubes were deposited on silicon substrate by low pressure chemical vapor deposition (LPCVD), which can be utilized as heat spreaders in high power electronic packaging due to their remarkable thermal conductivity. The infrared emissivity of the vertically aligned multiwall carbon nanotubes was then characterized based on the FLIR SC600 infrared imaging system. The average infrared emissivity of the multiwall carbon nanotubes sample was about 0.92, which agrees well with experimental results reported before. Scanning electron microscopy (SEM) images of the multiwall carbon nanotubes were further analyzed to explain its high emissivity, and the reason can be attributed to the homogeneous sparseness and aligned structure of the vertically aligned multiwall carbon nanotubes
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| 2. |
- Ye, Hui, et al.
(författare)
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Preventing Aging of Electrically Conductive Adhesives on Metal Substrate Using Graphene-Based Barrier
- 2016
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Ingår i: China Semiconductor Technology International Conference 2016, CSTIC 2016. - 9781467388047
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Konferensbidrag (refereegranskat)abstract
- Electrically conductive adhesives (ECAs) seem to be a promising substitute to traditional metal-based solders, because of them being environmentally friendly materials requiring much lower processing temperatures, and offering a much finer pitch. However, a critical problem related to the use of ECAs is that the contact resistance to the metal pad tends to increase significantly during aging tests due to galvanic corrosion, particularly in 85oC/85% relative humidity (RH) atmospheres. In this respect the reported impermeability of graphene, a property prohibiting most molecules including water vapor from penetrating the film, has made graphene a major candidate as an anti-corrosion barrier material. The use of graphene as an anti-corrosion barrier material on steel and other metals has already been reported in literature. In this paper, the use of graphene-based barriers[12] between the ECA and the copper pads on a printed circuit board for alleviating the galvanic corrosion problem is reported. A PCB test board was designed for monitoring the effects of introducing the graphene-based barrier on the contact resistance between ECA and copper while exposing the board to a 500 hour aging test in 85℃/85% RH. For samples without graphene-based barriers it was found that the contact resistance increased rapidly during the first 200 hours of the aging test, while the contact resistance for samples with the graphene-based barriers remained stable. For these samples with graphene-based barriers, the contact resistance showed a much smaller decay during the aging test than for those samples without graphene-based barriers. These findings indicate that graphene-based barriers could be a solution for improving the reliability of electrically conductive adhesives, especially in harsh 85oC/85% RH environment conditions.
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| 3. |
- Bao, Jie, et al.
(författare)
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Synthesis and Applications of Two-Dimensional Hexagonal Boron Nitride in Electronics Manufacturing
- 2016
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Ingår i: Electronic Materials Letters. - : Springer Science and Business Media LLC. - 1738-8090 .- 2093-6788. ; 12:1, s. 1-16
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Forskningsöversikt (refereegranskat)abstract
- In similarity to graphene, two-dimensional (2D) hexagonal boron nitride (hBN) has some remarkable properties, such as mechanical robustness and high thermal conductivity. In addition, hBN has superb chemical stability and it is electrically insulating. 2D hBN has been considered a promising material for many applications in electronics, including 2D hBN based substrates, gate dielectrics for graphene transistors and interconnects, and electronic packaging insulators. This paper reviews the synthesis, transfer and fabrication of 2D hBN films, hBN based composites and hBN-based van der Waals heterostructures. In particular, this review focuses on applications in manufacturing electronic devices where the insulating and thermal properties of hBN can potentially be exploited. 2D hBN and related composite systems are emerging as new and industrially important materials, which could address many challenges in future complex electronics devices and systems.
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| 4. |
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| 5. |
- Duan, Y., et al.
(författare)
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A New Thermally Conductive Thermoplastic Die Attach Film
- 2012
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Ingår i: Proceedings of IEEE CPMT 2012 International Conference on Electronic Packaging Technology & High Density Packaging. - 9781467316804 ; , s. 212-215
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Konferensbidrag (refereegranskat)abstract
- As devices with smaller footprint and, higher functionality become the norm, stacked die technology will be required to enable the advancement of modern integrated packaging. As wafers become ever thinner to meet stacking requirements, new materials technology must address the challenges of handling and processing wafer thicknesses of less than 100 microns. Die attach film (DAF) has being widely used as an alternative. With its good control of bleed, consistent bond line thickness and simplified operation. In this paper, a kind of thermoplastic film with good thermal conductivity was developed for die attachment application and some of its properties, such as shear strength and, thermal conductivity were investigated. In the present work, the formula of the DAF matrix has been determined and in order to improve thermal conductivity of DAF, silicon carbide (SiC) particles with high thermal conductivity were selected to add as filler and in the content of SiC particles on the property of the DAFs were also investigated. Shear tests were conducted to measure the bonding strength of the DAFs. The results show that the films reached a 6.5 MPa in terms of average shear strength and after plasticizing it could reach 3.5 MPa. The thermal conductivity of the DAFs was 0.37W/ m·K.
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| 6. |
- Fazi, Andrea, 1992, et al.
(författare)
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Multiple growth of graphene from a pre-dissolved carbon source
- 2020
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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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| 7. |
- Fu, Yifeng, 1984, et al.
(författare)
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Carbon nanotube growth on different underlayers for thermal interface material application
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226
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Konferensbidrag (refereegranskat)abstract
- Thermal interface material (TIM) is a critical component in thermal management of high density packaging systems since both the reliability and lifetime of microsystems are dependent on how the heat is dissipated. Carbon nanotubes (CNTs) are promising candidate for development of TIMs due to their excellent thermal and mechanical properties. The thermal conductivity of CNTs can be up to 3000 W/mK in the longitudinal direction which acts as ideal heat transfer path. However, the huge interfacial thermal resistance between CNTs and contact surface hinders the exploitation of CNTs as TIMs. In this paper, we will focus on the growth of CNTs on various substrates and underlayers and analyze the interaction between catalyst and underlayer materials. Microscopic analysis is performed to characterize the quality of the CNT materials and monitor the diffusion of Fe particles into different barrier layers. Thermal conductivity of the CNT TIMs will be measured to examine the performance of the materials.
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| 8. |
- han, Hao xue, et al.
(författare)
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Enhanced Heat Spreader Based on Few-Layer Graphene Intercalated With Silane-Functionalization Molecules
- 2014
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Ingår i: IEEE 20th International Workshop on Thermal Investigation of ICs and Systems (Therminic). Greenwich, London, United Kingdom, 24-26 September 2014. - 9781479954155 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- We studied the heat-spreading enhancement of supported few-layer graphene by inserting silane-functionalization molecules between graphene sheets. We calculated the overall thermal resistance of graphene-substrate interface and the in-plane thermal conductivity of graphene sheets by equilibrium molecular dynamics simulations. We probed the spectral phonon transmission coefficient by non-equilibrium Green's function to characterize the local heat conduction through the interface. Our results show that the overal thermal resistance between the substrate graphene and the upper two-layer graphene underwent a three-fold increase by the presence of the molecules, while the local heat conduction from the hot spot to the graphene sheets through the molecules was largely intensified. Furthermore, the in-plane thermal conductivity of the few-layer graphene increased by 60% compared with the supported graphene non-bonded to the substrate through the molecules. This increase is attributed to the refrained cross-plane phonon scattering which in turn reinforces the in-plane heat conduction of the few-layer graphene. In summary, we proved that by inserting silane-functionalization molecules, the few-layer graphene becomes an ideal candidate for heat spreading by guiding heat more efficiently away from the heat source.
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| 9. |
- 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
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Ingår i: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 31:45
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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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| 10. |
- Hansson, Josef, 1991, et al.
(författare)
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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.
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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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