| 31. |
- Edwards, Michael, 1986, et al.
(författare)
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Finite element simulation of 2D-based materials as heat spreaders
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226
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Konferensbidrag (refereegranskat)abstract
- Since the discovery of graphene, the first discovered 2D material, by Novoselov and Geim in 2004, the field of 2D materials has taken off and about 20 further 2D materials have been found. One of the most promising of these materials for the passive cooling of chips is hBN. HBN has the very unusual combination of being electrically insulating and thermally conductive, which potentially makes it an ideal material for both laterally spreading heat and passivating hotspots on chips. This gives hBN an advantage over graphene, where the chip requires a SiO2 passivation layer to prevent short circuits. To help evaluate the performance of these heat spreading films, a finite element model has been devised to support the experimental work undertaken in various publications. This model has been validated with experimental data and suggests that both graphene-And hBN-based materials have significant potential in lateral heat spreading applications.
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| 32. |
- Fu, Yifeng, 1984, et al.
(författare)
-
Carbon nanotube growth on different underlayers for thermal interface material application
- 2016
-
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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| 33. |
- Fu, Yifeng, 1984, et al.
(författare)
-
Post-Growth Processing of Carbon Nanotubes for Interconnect Applications - A Review
- 2016
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Ingår i: 2016 6th Electronic System-Integration Technology Conference (Estc). - 9781509014026 ; , s. Article no 7764713-
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Konferensbidrag (refereegranskat)abstract
- Interconnect is one of the most important functions of packaging technology. It delivers power and signals into and out of electronic systems. The performance and reliability of microsystems are dependent on the interconnect quality. This paper reviews the chip-level interconnects based on carbon nanotubes (CNTs), this includes their applications for both on-chip and off-chip interconnects. Various post-growth processing of CNTs, such as doping, densification, transfer, metallization, etc., for the improvement of their performance will be reviewed.
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| 34. |
- Grammatikos, Sotirios, 1985, et al.
(författare)
-
Concrete setting and hardening monitoring using a novel graphene-based sensor
- 2017
-
Ingår i: ICF 2017 - 14th International Conference on Fracture. ; 2, s. 1204-1205
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Konferensbidrag (refereegranskat)abstract
- This paper presents the procedure towards the development of a durable structural sensor based on graphene and other carbon fillers, for the monitoring of structural performance of concrete. The sensor captures electrical resistivity as a strength development and durability index during the whole service life of concrete. To date, performance monitoring systems usually fail in the long-run before the failure of the actual structure. The proposed sensor is embedded in the interrogated structure and ensures sustainable consolidation via appropriate physico-chemical adherence and mechanical interlocking. This allows for an efficient performance monitoring 'build-up' expected to surpass the service life of the parent concrete structure. The effects of different concentrations of graphene and other fillers on the electrical properties of concrete were studied. After an initial investigation to select the appropriate synthesis, the ability of the sensor to monitor the development of resistivity during setting and hardening was tested and the results are presented herein.
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| 35. |
- Gutierrez, Martí, 1993, et al.
(författare)
-
Sintering of SiC enhanced copper paste for high power applications
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging (NordPac). - 9781538630556 ; , s. 151-156
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Konferensbidrag (refereegranskat)abstract
- In this work a Cu paste consisting in both micro and nanoparticles was produced. The copper paste was produced with different additive weight percentages of Ag coated SiC and sintered for 30min at 500°C under 6,5MPa in N2 atmosphere. The thermal resistance and composition of the resulting joints was studied. XPS and EDX measurements show no significant oxidation of the Cu after sintering, which is attributed to the combination of reductive agents in the paste and the inert atmosphere. SEM images of cross sections show contacts with no voids between the SiC particles and the copper matrix. Thermal conductivity measurements with laser flash analysis (LFA) show that the additive increases the effective thermal conductivity to more than double of that of the pure copper paste at 2% additive weight percentage, but bigger amounts yield smaller improvements and presumably would eventually worsen it.
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| 36. |
- Han, H. X., et al.
(författare)
-
Functionalization mediates heat transport in graphene nanoflakes
- 2016
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by similar to 28 degrees C for a chip operating at 1,300 Wcm(-2). Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene-graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.
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| 37. |
- Hansson, Josef, 1991, et al.
(författare)
-
A review of recent progress of thermal interface materials: from research to industrial applications
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings; Tonsberg; Norway; 5 - 7 June 2016. - 9781510827226
-
Konferensbidrag (refereegranskat)abstract
- The increasing trend of further scaling down electronic components put an increasing demand for more efficient cooling. A significant part of the thermal resistance from source to ambient occurs at the interface between materials, and thermal interface materials are crucial for efficient heat transfer. Recent years have seen a significant amount of progress various types of thermal interface materials. In this review, the field of thermal interface materials (TIMs) development is summarized and analyzed, focusing on three topics which have received attention at a research level, and their road towards market applicability. The first topic is development in particle laden polymers, which uses thermally conductive filler particles in a polymer matrix. New development is focused on novel fillers such as h-BN or carbon based fillers, and hybrid filler combinations. The next topic is continuous metal phase TIMs, which includes solder and liquid metal TIMs. The thermal performance is already very good, and development is largely focused on improving the mechanical properties. Finally, the last topic is carbon nanotube array TIMs, which used chemical vapor deposition-grown carbon nanotube arrays as bridging material. The concept has promise for great performance in both handling, mechanical stability and thermal performance, but is still at a research stage. In addition to these topics, a quantitative study on the progress of thermal interface materials development is made, both in terms of research papers published and in terms of patents filed. The study shows a stable trend of continuous development on all levels and concludes that significant improvements can be expected to continue in the future.
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| 38. |
- Hansson, Josef, 1991, et al.
(författare)
-
Effect of Fiber Concentration on Mechanical and Thermal Properties of a Solder Matrix Fiber Composite Thermal Interface Material
- 2019
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 9:6, s. 1045-1053
-
Tidskriftsartikel (refereegranskat)abstract
- Increased demand on the mechanical and thermal properties on the thermal interface and die attach material creates a demand for materials with tailored material properties. Solder matrix fiber composites (SMFCs) have been shown to address these challenges, but have, so far, required complicated procedures and components. In this paper, we present the fabrication of a new type of SMFC based on commercially available fiber networks infiltrated with Sn-Ag-Cu alloy (SAC305) or indium using equipment for large-volume production. The composite material exhibits similar thermal properties compared to pure solder, and mechanical properties that can be tailored toward specific applications. We also show that the handling properties of the SMFC allows it to be used in process flows where multiple reflow cycles are required and can achieve a well-defined bond line thickness (BLT) and good bonding using fluxless reflow under pressure.
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| 39. |
- Hansson, Josef, 1991, et al.
(författare)
-
Fabrication and characterization of a carbon fiber solder composite thermal interface material
- 2017
-
Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging (NordPac). - 9781538630556 ; , s. 97-100
-
Konferensbidrag (refereegranskat)abstract
- One of the significant bottlenecks in thermal management is to develop thermal interface materials (TIMs) with lower thermal interface resistance while retaining good reliability, mechanical properties and handling capabilities. Recently, the combination of electrospun polymer fibers and solder matrix has gathered interest, combining the excellent thermal properties of metal with the mechanical properties of polymers. Carbon fibers are increasingly common as reinforcement in composites, owing to their high strength and thermal conductivity. Utilizing carbon fibers in a similar composite could allow for the fabrication of TIMs with so far unexplored properties such as increased thermal conductivity, strength and tunable CTE. In this work, we have fabricated and characterized a TIM based on a carbon fiber network infiltrated by an alloy of Sn-Ag-Cu, (CF-TIM). Commercially available carbon fibers are coated with a thin layer of Ag and infiltrated by molten alloy under high pressure. The result is a preform TIM, easy to handle and compatible with standard SMT assembly. A thermal interface resistance lower than 2 Kmm2/W between two ENIG coated Cu substrates was measured with laser flash. Comparing total thermal interface resistance to bond line thickness indicates a very low contact resistance consistent with good metallurgical bonding and a bulk thermal conductivity of 24 W/mK for the TIM. X-ray inspection and SEM of cross section of the assembled structure indicates good adhesion between fiber and matrix, and a very low degree of voiding. To demonstrate the handling capabilities of CF-TIM, a variety of reflow conditions were investigated. A consistent bond line thickness (BLT) of 45±5μm was achieved independent on applied pressure during reflow, and decreased less than 20% after 10 additional reflow cycles, without additional material leakage. This demonstrates the possibility of CF-TIM use in assembly line processes requiring additional reflow steps. Solder preforms are common in industry, and due to similar handling characteristics of the CF-TIM, it should be easily integrated into existing electronics assembly lines. The usage of commercial fibers not reliant on slow and expensive processes such as electrospinning further opens up the potential for mass production.
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| 40. |
- Hansson, Josef, 1991, et al.
(författare)
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Novel nanostructured thermal interface materials: a review
- 2018
-
Ingår i: International Materials Reviews. - : Informa UK Limited. - 0950-6608 .- 1743-2804. ; 63:1, s. 22-45
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Forskningsöversikt (refereegranskat)abstract
- The trend of continuing miniaturisation of microelectronics leads to new thermal management challenges. A key point in the heat removal process development is to improve the heat conduction across interfaces through improved thermal interface materials (TIMs). We identify the key areas for state-of-the art TIM research and investigate the current state of the field together with possible future advances.
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