| 51. |
- Jiang, Di, 1983, et al.
(författare)
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A flexible and stackable 3D interconnect system using growth-engineered carbon nanotube scaffolds
- 2017
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Ingår i: Flexible and Printed Electronics. - : IOP Publishing. - 2058-8585. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- One of the critical challenges for realizing flexible electronic systems for a wide range of applications is the development of materials for flexible and stackable interconnects. We propose and demonstrate a three-dimensional (3D)interconnect structure embedded in a polymeric substrate using metal-coated carbon nanotube (CNT)scaffolds. By using two different underlayer materials for the catalyst, onestep synthesis of a dual-height CNT interconnect scaffold was realized. The CNT scaffolds serve as flexible cores for both annular metal through-substrate-vias and for horizontal metal interconnect. The 3D-CNT network was fabricated on a silicon substrate, and once the scaffolds were covered by metal, they were embedded in a polymer serving as a flexible substrate after peel-off from the silicon substrate. The 3D-CNT interconnect network was exposed to mechanical bending and stretching tests while monitoring its electrical properties. Even after 300 cycles no significant increase of resistances was found. Electrically there is a trade-off between flexibility and conductivity due to the surface roughness of the scaffold. However, this is to some extent alleviated by the metalized sidewalls giving the horizontal wires a cross-sectional area larger than indicated by their footprint. For gold wires 200 nm thick, measurements indicated a resistivity of 18 μΩ.cm, a value less than one order of magnitude larger than that of bulk gold, and a value that is expected to improve as technology improves. The mechanical properties of the metalized scaffolds were simulated using a finite element model. The potential scale-up capability of the proposed 3D-CNT network was demonstrated by the stacking of two such polymer-embedded interconnect systems.
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| 52. |
- Jiang, Di, 1983, et al.
(författare)
-
Carbon nanotube/solder hybrid structure for interconnect applications
- 2014
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Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962751-
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Konferensbidrag (refereegranskat)abstract
- A carbon nanotube (CNT)/Solder hybrid bump structure is proposed in this work in order to overcome the drawbacks of high CNT resistivity while retaining the advantages of CNTs in terms of interconnect reliability. Lithographically defined hollow CNT moulds are grown by thermal chemical vapor deposition (TCVD). The space inside the CNT moulds is filled up with Sn-Au-Cu (SAC) solder spheres of around 10 μm in diameter. This CNT/Solder hybrid material is then reflowed and transferred onto target indium coated substrate. The reflow melts the small solder spheres into large single solder balls thus forming a hybrid interconnect bump together with the surrounding densified CNT walls, which the CNT and the solder serve as resistors in parallel. The electrical resistance of such a CNT/Solder structure is measured to be around 6 folds lower than pure CNT bumps.
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| 53. |
- Jiang, Di, 1983, et al.
(författare)
-
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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| 54. |
- Jiang, Di, 1983, et al.
(författare)
-
Room Temperature Transfer of Carbon Nanotubes on Flexible Substrate
- 2012
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Ingår i: Proceedings of the 18th Therminic International Workshop on Thermal Investigations of ICs and Systems, Budapest, 25-27 September 2012. - 9782355000225 ; , s. 213-216
-
Konferensbidrag (refereegranskat)abstract
- In this paper we report a novel method of transferring thermally grown vertically aligned carbon nanotubes (VA-CNTs) onto flexible substrates at room temperature with a single-step process. The transfer process is carried out by placing the CNT forests upside down on a double sided thermal release adhesive tape and peeling off the silicon substrate. Scanning electron microscope (SEM) is used to observe the transfer results. Also a second transfer using the same method but a thermal tape with higher release temperature is repeated on the as-transferred CNTs forests. The results show that this method is able to provide a novel process for transferring CNT forests at room temperature. This process will help to bring close the low cost fabrication of vertically aligned CNT structures for electronics.
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| 55. |
- Jiang, Di, 1983, et al.
(författare)
-
Vertically stacked carbon nanotube-based interconnects for through silicon via application
- 2015
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 36:5, s. 499-501
-
Tidskriftsartikel (refereegranskat)abstract
- Stacking of silicon chips with carbon nanotube (CNT)-based through-silicon vias (TSVs) is experimentally demonstrated. Polymer filling is used to improve the transfer quality of CNTs into pre-etched silicon holes. Special hexagonal CNTs are designed to achieve high aspect ratio (10:1) CNT vias. TSVs filled with closely packed CNTs show a highly linear dc I - V response. The proposed process works at room temperature, which makes it compatible with existing device fabrication flow.
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| 56. |
- Kabiri Samani, Majid, 1976, et al.
(författare)
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Improving Thermal Transport at Carbon Hybrid Interfaces by Covalent Bonds
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 2018:5
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Tidskriftsartikel (refereegranskat)abstract
- Graphene and carbon nanotubes have received much attention for thermal management application due to their unique thermal performance. Theoretical work suggests that a covalent bond can combine 1D carbon nanotubes with 2D graphene together to extend the excellent thermal property to three dimensions for heat dissipation. This paper experimentally demonstrates the high heat dissipation capability of a freestanding 3D multiwall carbon nanotube (MWCNT) and graphene hybrid material. Using high-resolution transmission electron microscopy and pulsed photothermal reflection measurement method, the covalent bonds between MWCNT and planar graphene are microscopically and numerically demonstrated. Thermal resistance at the junction with covalent bonds is 9×10^−10 Kelvin square meter per watt, which is three orders of magnitude lower than van der Waals contact. Joule heating method is used to verify the extra cooling effect of this 3D hybrid material compared to graphite film. A demonstrator using high power chip is developed to demonstrate the applicability of this hybrid material in thermal application. Temperature at hot spots can be decreased by around 10°C with the assistance of this hybrid material. These findings are very significant for understanding the thermal conduction during combining 1D and 2D carbon material together for future thermal management application.
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| 57. |
- Kabiri Samani, Majid, 1976, et al.
(författare)
-
Thermal conductivity measurement of densified carbon nanotube bundles by pulsed photothermal reflectance technique
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226
-
Konferensbidrag (refereegranskat)abstract
- Carbon nanotubes (CNTs) were proposed as a promising interconnection material in future miniaturized electronics, owing to their exceptional electrical and thermal properties. A series of CNT bundles with 1 mm diameter were grown on silicon substrate by thermal Chemical Vapor Deposition (CVD) at temperature 700 oC. The as grown CNT bundles were densified by a vapor densification method. SEM analysis shows that the vapor densification is densified the CNT forests, which reduces the air volume fraction to increase thermal conductivity of the CNT bundles. The pulsed photothermal reflectance technique is applied to measure thermal conductivity of the CNT bundle before and after densification and the results show the thermal conductivity of densified CNT bundles increases and capability of making CNT filled through silicon via with better thermal and electrical performance.
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| 58. |
- Li, Qi, 1990, et al.
(författare)
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Compact and low loss electrochemical capacitors using a graphite / carbon nanotube hybrid material for miniaturized systems
- 2019
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 412, s. 374-383
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Tidskriftsartikel (refereegranskat)abstract
- With the establishment of the internet of things (IoT) and the rapid development of advanced microsystems, there is a growing demand to develop electrochemical capacitors (ECs) to replace bulky electrolytic capacitors on circuit boards for AC line filtering, and as a storage unit in energy autonomous systems. For this purpose, ECs must be capable of handling sufficiently high signal frequencies, display minimum energy loss through self-discharge and leakage current as well as maintaining an adequate capacitance. Here, we demonstrate ECs based on mechanically flexible, covalently bonded graphite/vertically aligned carbon nanotubes (graphite/VACNTs) hybrid materials. The ECs employing a KOH electrolyte exhibit a phase angle of −84.8°, an areal capacitance of 1.38 mF cm−2 and a volumetric capacitance (device level) of 345 mF cm−3 at 120 Hz, which is among the highest values for carbon based high frequency ECs. Additionally, the performance as a storage EC for miniaturized systems is evaluated. We demonstrate capacitive charging/discharging at μA current with a gel electrolyte, and sub-μA leakage current reached within 50 s, and 100 nA level equilibrium leakage within 100 s at 2.0 V floating with an ionic liquid electrolyte.
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| 59. |
- Li, X., et al.
(författare)
-
Reliability of Carbon Nanotube Bumps for Chip on Film Application
- 2013
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Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781479906758 ; , s. 845-848
-
Konferensbidrag (refereegranskat)abstract
- Carbon nanotubes (CNTs) are an ideal candidate for electrical interconnects due to their extraordinary thermal, electrical and mechanical properties. In this work, as-densified CNT bumps were applied as chip on film (COF) interconnection material. A silicon chip with patterned CNT bumps was bonded onto a flexible substrate using anisotropic conductive adhesive (ACA) with bonding pressure, at 127.4 MPa, 170 °C and for 8 seconds. The electrical properties of this structure were evaluated by measuring the contact resistance of each bump using the four-point probe method. Thermal cycling (-40∼85°C, 1000 cycles) and damp heat tests (85°C/85% RH, 1000 hours) were conducted to evaluate the reliabilities of the CNT-COF structure bonded with ACA. The average contact resistances of two samples used for the reliability tests were 226 mΩ and 260mΩ. No electrical failure was observed after the damp heat test and only two were observed after the thermal cycling test. The average contact resistance was increased only 15.7% and 13.8%, respectively, after the thermal cycling and the damp heat tests. © 2013 IEEE.
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| 60. |
- Liu, Johan, 1960, et al.
(författare)
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Carbon Nanotubes for Electronics Manufacturing and Packaging: From Growth to Integration
- 2013
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Ingår i: Advances in Manufacturing. - : Springer Science and Business Media LLC. - 2095-3127 .- 2195-3597. ; 1:1, s. 13-27
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Forskningsöversikt (refereegranskat)abstract
- Carbon nanotubes (CNTs) possess excellent electrical, thermal and mechanical properties. They are light in weight yet stronger than most of the other materials. They can be made both highly conductive and semi-conductive. They can be made from nano-sized small catalyst particles and extend to tens of millimeters long. Since CNTs emerged as a hot topic in the early 1990s, numerous research efforts have been spent on the study of the various properties of this new material. CNTs have been proposed as alternative materials of potential excellence in a lot of applications such as electronics, chemical sensors, mechanical sensors/actuators and composite materials, etc. This paper reviews the use of CNTs particularly in electronics manufacturing and packaging field. The progresses of three most important applications, including CNT-based thermal interface materials, CNT-based interconnections and CNT-based cooling devices are reviewed. The growth and post-growth processing of CNTs for specific applications are introduced and the tailoring of CNTs properties, i.e., electrical resistivity, thermal conductivity and strength, etc., is discussed with regard to specific application requirement. As the semiconductor industry is still driven by the need of getting smaller and faster, CNTs and the related composite systems as emerging new materials are likely to provide the solution to the future challenges as we make more and more complex electronics devices and systems.
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