| 1. |
- Fu, Yifeng, 1984, et al.
(författare)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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| 2. |
- Fu, Yifeng, 1984, et al.
(författare)
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Selective growth of double-walled carbon nanotubes on gold films
- 2012
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 72, s. 78-80
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Tidskriftsartikel (refereegranskat)abstract
- Growth of high-quality vertical aligned carbon nanotube (CNT) structures on silicon supported gold (Au) films by thermal chemical vapor deposition (TCVD) is presented. Transmission electron microscopy (TEM) images show that the growth is highly selective. Statistical study reveals that 79.4% of the as-grown CNTs are double-walled. The CNTs synthesized on Au films are more porous than that synthesized on silicon substrates under the same conditions. Raman spectroscopy and electrical characterization performed on the as-grown double-walled CNTs (DWNTs) indicate that they are competitive with those CNTs grown on silicon substrates. Field emission tests show that closed-ended DWNTs have lower threshold field than those open-ended.
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| 3. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer-metal nanofibrous composite for thermal management of microsystems
- 2012
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 75, s. 229-232
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, a composite structure based on a porous electrospun polyimide structure infiltrated with indium aimed at thermal interface material applications is presented. A porous nanofibrous structure was prepared by electrospinning of polyimide. An interfacial nanocomposite layer of silver nanoparticles partially or fully embedded in the polyimide matrix was synthesized on the fiber surfaces, followed by autocatalytic deposition of a uniform silver coating (using the interfacial layer as an anchored seed layer) serving as a reactive wetting layer for the infiltrating melt. The thermal performance of the composite was evaluated and the thermal conductivity was determined to be 27 W/mK, accompanied by low contact resistance of the metallurgical bond (
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| 4. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer nanofiber based continuous metal phase composite for thermal management applications
- 2010
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Ingår i: 3rd Electronics System Integration Technology Conference, ESTC 2010; Berlin; Germany; 13 September 2010 through 16 September 2010. - 9781424485536 ; , s. Art. no. 5642950-
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Konferensbidrag (refereegranskat)abstract
- A new composite design approach for thermal interface materials is presented. A porous electro spun nanofiber network composed of temperature stable poly imide was infiltrated with liquid phase indium at a pressure of 30 MPa. The polymer phase defmes composition and geometry, while the continuous metal phase gives binding to surfaces and high thermal conductivity. The composite was characterized by assembly of tri-layer copper/TIM/copper sandwich structures and subsequent xenon flash measurements extracting the thermal properties of the intermediate TIM layer. The interfacial contact resistance was found to be 8 Kmm2/W and the thermal conductivity was 28 W/mK, indicating the potential for use in thermal management applications.
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| 5. |
- Carlberg, Björn, 1983, et al.
(författare)
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Surface-Confined Synthesis of Silver Nanoparticle Composite Coating on Electrospun Polyimide Nanofibers
- 2011
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:21, s. 3057-3066
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1)). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO(3) solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.
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| 6. |
- Casa, Marcello, et al.
(författare)
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Development and characterization of graphene-enhanced thermal conductive adhesives
- 2014
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Ingår i: 15th International Conference on Electronic Packaging Technology, ICEPT 2014; Wangjiang HotelChengdu; China; 12 August 2014 through 15 August 2014. - 9781479947072 ; :Art. no. 6922700, s. 480-483
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Konferensbidrag (refereegranskat)abstract
- According to Moore's Laws, complexity and power densities of electronic devices are increased during the last decades, moreover their dimensions are shrinking to nanometers causing hot-spot temperature escalation. Thermal management, therefore, becomes a critical issue for next generation of electronics. This scenario motivates development of novel thermal conductive adhesive (TCA) with enhanced thermal conductivity. Conventional TCAs use polymers as the matrix (base material) and utilize large loading weight fraction of the filler, usually silver particles, to achieve the thermal conductivity of 1-4 W/ m K at room temperature [1]. Lately it was discovered that graphene exhibit superior thermal conductivity [2] even when they are incorporated with matrix materials [3], which offers a potential to develop high thermal conductive graphene-filled compound. In this paper, a new functionalized graphene and its filled TCA have been developed and characterized. Starting from pristine graphite flakes, graphene was prepared through chemical exfoliation and functionalized with a nano silver layer to form a special metal/graphene hybrid material. Moreover, an efficient method to uniformly disperse the nano-scaled graphene hybrid material in silver-epoxy matrix was developed. Cross-section view of SEM has shown a homogeneous component structure, and TGA analysis of hybrid material is given. The developed compound is based on a commercial TCA which is composed with epoxy matrix and micro-sized Ag flakes. Thermal characterization through Laser-flash equipment has indicated that a significant thermal conductivity improvement was achieved through adding functionalized graphene into the material. Different TCA samples with different weight percentages of functionalized graphene ranging from 0 % (reference) to 11.5 % were prepared and tested to study thermal conductivity change. Data show that a thermal conductivity value of 7.6 W/ m K is reached when the graphene/silver percentage is 11.5 % that is almost 4 times higher than our reference.
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| 7. |
- Chen, S., et al.
(författare)
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A solder joint structure with vertically aligned carbon nanofibres as reinforcements
- 2014
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Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962851-
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Konferensbidrag (refereegranskat)abstract
- In this paper, a solder joint structure was developed for the electronic packaging industry. Vertically aligned carbon nanofibres (VACNFs) were grown, transferred and used at the interface between Si/Au pads and Sn-3.0Ag-0.5Cu (SAC305) alloy as reinforcements in order to increase the solder joint thermal fatigue resistance. The transfer and assembly processes related to VACNFs were optimised and developed. The thermal cycling test results show that the thermal fatigue life of VACNF/SAC305 solder joints is 40% longer than that of pure SAC305. The dye and pry analysis and scanning electron microscopy observation prove that the VACNFs can effectively delay the crack propagation near the interface and consequently prolong the solder joint thermal fatigue life.
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| 8. |
- Daon, J., et al.
(författare)
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Electrically conductive thermal interface materials based on vertically aligned carbon nanotubes mats
- 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
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Konferensbidrag (refereegranskat)abstract
- In power microelectronics, the trends towards miniaturization and higher performances result in higher power densities and more heat to be dissipated. In most electronic assembly, thermal interface materials (TIM) help provide a path for heat dissipation but still represent a bottleneck in the total thermal resistance of the system. VA-CNTs mats are typically grown on HR silicon substrate with Al2O3 diffusion barrier layer using Thermal CVD process. In many cases, 'die attach' thermal interface materials need to be electrically conductive and the growth of dense VA-CNT mats on an electrically conductive substrate remains a challenge. This paper presents the growth of dense VA-CNT mats on doped silicon with Al2O3 and TiN diffusion barrier layer. Processes, thermal and electrical characterization of VA-CNTs based thermal interface materials are studied and reported.
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| 9. |
- Du, W., et al.
(författare)
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Study into high temperature reliability of isotropic conductive adhesive
- 2011
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Ingår i: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. - 9781457717680 ; , s. 1053-1055
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Konferensbidrag (refereegranskat)abstract
- With the rapid development of technologies for high density assembly and packaging in electronic industry, isotropic conductive adhesive (ICA) has been paid more and more attention as a potential substitute for solder, due to its advantages of low processing temperature, simple processing conditions and good manufacturability. However, studies into the reliability of ICA are not as abundant as those of solder. As a composite material, the failure feasibility of ICA not only depends not only on the variation in performance of different constituent parts, such as high temperature aging of the polymer, aging due to moisture absorption and oxidization of filler particles, but also on interface changes. Thus, the failure mechanism of ICA seems to be complicated and studies into the reliability of ICA are also necessary. Reliability in humidity and heat has been investigated in previous works, and in this paper high temperature reliability will be studied as a comparison. Some reliability tests and results will be given and some failure mechanisms discussed. Finally, we present some discussion about the further optimization of reliability for follow-up studies.
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| 10. |
- Fałat, T., et al.
(författare)
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Experimental results versus numerical simulations of In/Cu intermetallic compounds growth
- 2014
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Ingår i: Proceedings of the 16th Electronics Packaging Technology Conference, EPTC 2014, Marina Bay Sands, Singapore, 3-5 December 2014. - 9781479969944 ; , s. 797-800
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Konferensbidrag (refereegranskat)abstract
- Indium is often used as a solder material which also plays a role of thermal interface e.g. in power LED systems. Indium and copper forms the intermetallic compounds. The growth rate constant at 400 K between copper and indium by the molecular dynamics simulations, as well as, experimentally was investigated. The results shown that the growth of the intermetallic compound in both cases follows the parabolic low, which indicates that the growth was mainly controlled by volume diffusion.
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