| 1. |
- Chen, Si, 1981, et al.
(författare)
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Sn-3.0Ag-0.5Cu Nanocomposite Solder Reinforced With Bi2Te3 Nanoparticles
- 2015
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3985 .- 2156-3950. ; 5:8, s. 1186-1196
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite solders are regarded as one of the most promising interconnect materials for the high-density electronic packaging due to their high mechanical strength and fine microstructure. However, the developments of nanocomposite solders have been limited by the inadequate compatibility between nanoparticles and solder matrix with respect to density, hardness, coefficient of thermal expansion, and surface activity. The compatibility issue will lead to a huge loss of nanoparticles from the solder matrix after the reflow soldering process. The thermal fatigue resistance of solder joint will also become degraded. Therefore, aiming to solve this problem, a novel nanocomposite solder consisting of Bi2Te3 semiconductor nanoparticles and Sn-3.0Ag-0.5Cu (SAC305) solder is presented. The effect of nanoparticles on the viscosity of solder paste and the void content of solder bump was first studied. Then, a series of analysis on the composition and microstructure of the solder bump were completed using transmission electron microscopy, X-ray diffraction, inductively coupled plasma-mass spectrometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The survival rate of nanoparticles in the solder bump after reflow soldering process reaches as high as 80%. The refined microstructure was observed from the cross section of the nanocomposite solders. The shear test showed that the average mechanical strength of SAC305 solder after the addition of Bi2Te3 nanoparticles was higher. Meanwhile, no thermal fatigue resistance degradation was detected in the nanocomposite solder after 1000 thermal cycles in the range of -40 degrees C to 115 degrees C.
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| 2. |
- Daon, J., et al.
(författare)
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Chemically enhanced carbon nanotubes based Thermal Interface Materials
- 2015
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Ingår i: THERMINIC 2015 - 21st International Workshop on Thermal Investigations of ICs and Systems 2015. - 9781467397056
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Konferensbidrag (refereegranskat)abstract
- With progress in microelectronics the component density on a device increases drastically. As a consequence the power density reaches levels that challenge device reliability. New heat dissipation strategies are needed to efficiently drain heat. Thermal Interface Materials (TIMs) are usually used to transfer heat across interfaces, for example between a device and its packaging. Vertically Aligned Carbon Nanotubes (VACNTs) can be used to play this role. Indeed, carbon nanotubes are among the best thermal conductors (similar to 3.000 W/mK) and in the form of VACNT mats, show interesting mechanical properties. On one side, VACNTs are in contact with their growth substrate and there is a low thermal resistance. On the other side, good contact must be created between the opposite substrate and the VACNTs in order to decrease the contact thermal resistance. A thin-film deposition of an amorphous material can be used to play this role. This paper reports a chemically enhanced carbon nanotube based TIM with creation of chemical bonds between the polymer and VACNTs. We show that these covalent bonds enhance the thermal transfer from VACNTs to a copper substrate and can dramatically decrease local resistances. Implementation processes and thermal characterizations of TIMs are studied and reported.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Jiang, Di, 1983, et al.
(författare)
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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
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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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| 6. |
- Mu, Wei, 1985, et al.
(författare)
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Tape-Assisted Transfer of Carbon Nanotube Bundles for Through-Silicon-Via Applications
- 2015
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 44:8, s. 2898-2907
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Tidskriftsartikel (refereegranskat)abstract
- Robust methods for transferring vertically aligned carbon nanotube (CNT) bundles into through-silicon vias (TSVs) are needed since CNT growth is not compatible with complementary metal–oxide–semiconductor (CMOS) technology due to the temperature needed for growing high-quality CNTs (∼700°C). Previous methods are either too complicated or not robust enough, thereby offering too low yields. Here, a facile transfer method using tape at room temperature is proposed and experimentally demonstrated. Three different kinds of tape, viz. thermal release tape, Teflon tape, and Scotch tape, were applied as the medium for CNT transfer. The CNT bundle was adhered to the tape through a flip-chip bonder, and the influence of the bonding process on the transfer results was investigated. Two-inch wafer-scale transfer of CNT bundles was realized with yields up to 97% demonstrated. After transfer, the use of several different polymers was explored for filling the gap between the transferred CNT bundle and the sidewalls of the TSV openings to improve the filling performance. The current–voltage characteristic of the CNT TSVs indicated good electrical performance, and by measuring the via resistance as a function of via thickness, contact resistances could be eliminated and an intrinsic CNT resistivity of 1.80 mΩ cm found.
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| 7. |
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| 8. |
- Wang, Nan, 1988, et al.
(författare)
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Flexible Multifunctionalized Carbon Nanotubes-Based Hybrid Nanowires
- 2015
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 25:26, s. 4135-4143
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Tidskriftsartikel (refereegranskat)abstract
- In this work, flexible multifunctionalized carbon nanotube (CNT)-based hybrid nanowires are synthesized through surface modification processes. The good dispersability of the hybrid nanowire in polar solvents facilitates directly making fine patterns with a minimum width of 40 μm for applications of flexible and stretchable circuits (FSCs). The hybrid nanowire possesses a flexible and highly conductive structure which demonstrates stable electro-mechanical properties on polydimethylsiloxane (PDMS) substrates under large structural deformation. FSCs fabricated from the hybrid nanowires show a constant resistance of 0.096 Ω □-1 (equivalent of a resistivity 0.96 Ω μm) under repeated bending cycles. The FSCs also have a low and stable sheet resistance of 0.4 Ω □-1 for strains up to 30%, which is almost four orders of magnitude lower than that of pure CNT samples (1316 Ω □-1). Further improved stretchability and electro-mechanical properties (0.1 Ω □-1, at the strain of 100%) are achieved with a prestrain PDMS substrate. Repeated deformation tests demonstrate the high reliability of FSCs. The observed stable and reliable electro-mechanical performance of FSCs suggests the potential use of the material in wearable and portable electronics. Multifunctionalized hybrid nanowires based on carbon nanotubes are prepared through different surface modification processes. These hybrid nanowires exhibit both the high electrical conductivity of metal and excellent mechanical properties of carbon nanotubes together with good dispersability. Flexible and stretchable electrodes based on the hybrid nanowires demonstrate stable electro-mechanical properties under large structural deformations.
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