| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Fan, X., et al.
(författare)
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Reliability of carbon nanotube bumps for chip on glass application
- 2014
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Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962753-
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Konferensbidrag (refereegranskat)abstract
- Carbon nanotubes (CNTs) are an ideal candidate material for electronic interconnects due to their extraordinary thermal, electrical and mechanical properties. In this study, densified CNT bumps utilizing the paper-mediated controlled method were applied as the interconnection for chip on glass (COG) applications, and the silicon chip with patterned CNT bumps was then flipped and bonded onto a glass substrate using anisotropic conductive adhesive (ACA) at a bonding pressure of 127.4 Mpa, 170°C for 8 seconds. The electrical properties of the COG were evaluated with the contact resistance of each bump measured using the four-point probe method. Three different structure traces, marked as Trace A, Trace B, and Trace C, were tested, respectively. Thermal cycling (-40 to 85°C, 800 cycles) and damp heat tests (85°C/85% RH, 1000 hours) were also conducted to evaluate the reliability of the CNT-COG structure. The average contact resistance of the samples was recorded during these tests, in which there was no obvious electrical failure observed after both the thermal cycling and damp heat tests. The results of these tests indicated that the COG has good reliability and the CNT bumps have promising potential applications in COG.
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| 6. |
- 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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| 7. |
- Jiang, Di, 1983, et al.
(författare)
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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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| 8. |
- Liu, Johan, 1960, et al.
(författare)
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1. Thermal Characterization of Power Devices Using Graphene-based Film
- 2014
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781479924073 ; , s. 459 - 463
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Konferensbidrag (refereegranskat)abstract
- Due to its atomic structure with sp2 hybrid orbitals and unique electronic properties, graphene has an extraordinarily high thermal conductivity which has been reported to be up to 5000 W/mK. As a consequence, the use of graphene-based materials for thermal management has been subject to substantial attention during recent years in both academia and industry. In this paper, the development of a new type of graphene-based thin film for heat dissipation in power devices is presented. The surface of the developed graphene based film is primarily composed of functionalized graphene oxide, that can be bonded chemically to the device surface and thus minimize the interface thermal resistance caused by surface roughness. A very high in-plane thermal conductivity with a maximum value of 1600 W/mK was detected by laser flash machine regarding to the graphene-based films. To investigate the structure of the graphene-based films, scanning electron microscopy (SEM) and raman spectroscopy were carried out. Finally, LED demonstrators were built to illustrate the thermal performance of graphene-based film and the functional layers. IR camera recorded a 5°C lower temperature of a LED demonstrator with SHT G1000 as the binding layer instead of a commercial thermal conductive adhesive.
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| 9. |
- Liu, Johan, 1960, et al.
(författare)
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A new solder matrix nano polymer composite for thermal management and die attach applications
- 2014
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Ingår i: Composites Science and Technology. - 0266-3538. ; 94, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- The increasing integration of microelectronics, raising the need for effective heat dissipation, requires new and improved composite materials technologies. For both thermal interface and die attach materials, a major challenge is to combine low thermal resistance joints with sufficient thermomechanical decoupling and reliability. In this paper, we present the fabrication and characterisation of a new type of solder matrix nano polymer composite (SMNPC) aiming to address these challenges. The SMNPC is fabricated into preforms by liquid-phase infiltration of a Sn–Ag–Cu matrix into a silver nanoparticle coated electrospun polyimide fibre mesh. The composite is demonstrated to possess high heat transfer capability, close to that of a direct soldered interface, lower elastic modulus compared to pure Sn–Ag–Cu alloy, and reliable thermomechanical performance during thermal cycling. Taken together, the results indicate that the developed SMNPC can be a useful composite alternative compared to conventional solders and polymer matrix materials for thermal management applications.
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| 10. |
- Liu, Johan, 1960, et al.
(författare)
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CHEMICALLY VAPOR DEPOSITED CARBON NANOTUBES FOR VERTICAL ELECTRONICS INTERCONNECT IN PACKAGING APPLICATIONS
- 2014
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Ingår i: Proceedings of the 12th international conference on Solid States and Integrated Circuits, ICSICT2014. - 9781479932962 ; , s. 47-50
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Konferensbidrag (refereegranskat)abstract
- Carbon Nanotubes (CNTs) have excellent electrical, thermal and mechanical properties. They are mechanically strong at nanoscale yet also flexible if made micro- or milli-meter long. They are synthesized from nano-sized catalyst particles and can be made up to millimeters. A lot of research studies have been spent on various properties of the CNTs. They are regarded as an alternative material in a lot of applications such as ICs, MEMS, sensors, biomedical and other composite materials, etc. Among them, the thermally grown CNTs using chemical vapor deposition method is of particular interested in electronics applications as an interconnect material. This paper reviews the use of CNTs as an interconnect material for packaging applications. The growth and post-growth processing of CNTs are covered and the tailoring of CNTs properties, i.e. electrical resistivity, thermal conductivity and strength, etc., is discussed. To make the electronics systems smaller, faster and more power efficient, CNTs as a potential new material are likely to provide the solution to the future challenges as the electronics systems are getting more and more functional and complex nowadays.
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