| 1. |
- Liu, Ya, 1991, et al.
(författare)
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Graphene based thermal management system for battery cooling in electric vehicles
- 2020
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Ingår i: Proceedings - 2020 IEEE 8th Electronics System-Integration Technology Conference, ESTC 2020.
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Konferensbidrag (refereegranskat)abstract
- In this work, a graphene assembled film integrated heat sink and water cooling technology was used to build an experimental set-up of a thermal management system to demonstrate the possibility to achieve efficient cooling of the propulsion battery in electric vehicles. The experimental results showed that the temperature decrease of a Li-ion battery module can reach 11°C and 9 °C under discharge rates as of 2C and 1C, respectively. The calculated thermal resistance of the graphene based cooling system is about 76% of a similar copper based cooling system. Surface modification was carried out on the graphene sheet to achieve a reliable bonding between the graphene sheet and the battery cell surface. This work provides a proof of concept of a new highly efficient approach for electric vehicle battery thermal management using the light-weight material graphene.
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| 2. |
- Zhang, Q., et al.
(författare)
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Effect of sintering method on properties of nanosilver paste
- 2017
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Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. ; , s. 186-189
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Konferensbidrag (refereegranskat)abstract
- Nanoscale silver paste has a good application prospect in heat dissipation of high-power chips due to the characteristics of low temperature sintering and high temperature service. The properties of the nanosilver paste including thermal conductivity, electrical conductivity, and shear strength are affected greatly by the sintering process. The influence of different sintering methods on the performance of the nanosilver paste was studied in this article. The nanosilver paste with 80.5 wt% nano-scale silver particles, 1.5 wt% submicron-scale SiC particles with Ag coating, 0.9 wt% dispersion agent, 10 wt% organic carrier and 7.1 wt% diluting agent was sintered at 260°C for 30 min with three different methods, heating table sintering, heating furnace sintering, and mixed sintering. The samples obtained by mixed sintering process have higher thermal conductivity than the ones obtained by heating furnace sintering method and heating table sintering method. The effect of sintering methods on shear strength of nanosilver paste was also investigated subsequently. Shear testing equipment was used to measure the shear strength of the samples gained by heating table sintering, heating furnace sintering, and air dry oven sintering. The maximum shear strength was obtained for the samples by heating table sintering method. The shear strength of samples by air dry oven sintering method was the minimum one.
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| 3. |
- Zhang, Q., et al.
(författare)
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Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles
- 2019
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Ingår i: Soldering and Surface Mount Technology. - 1758-6836 .- 0954-0911. ; 31:4, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, Emerald Publishing Limited. Purpose: This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated. Design/methodology/approach: Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively. Findings: Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles. Originality/value: Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.
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| 4. |
- 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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| 5. |
- Gutierrez, Martí, 1993, et al.
(författare)
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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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| 6. |
- Han, H. X., et al.
(författare)
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Functionalization mediates heat transport in graphene nanoflakes
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 7
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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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| 7. |
- Hansson, Josef, 1991, et al.
(författare)
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Synthesis of a Graphene Carbon Nanotube Hybrid Film by Joule Self-heating CVD for Thermal Applications
- 2018
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2018-May
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Konferensbidrag (refereegranskat)abstract
- Hybrid films based on vertically aligned carbon nanotubes (CNTs) on graphene or graphite sheets have been proposed for application as thermal interface materials and micro heat sinks. However, the fabrication of these materials are limited to small scale, expensive and complicated chemical vapor deposition (CVD) for CNT synthesis. We present a new method for direct growth of CNTs on one or both sides of a thin graphene film (GF) using joule self-heating of the graphene film to provide the necessary heat for the thermal breakdown of carbon feedstock in a CVD process. The resulting CNT forests show good density and alignment consistent with regular CVD synthesis processes on silicon surfaces. The resulting double sided GF/CNT hybrid film is directly applicable as a thermal pad. The CNT forest has a thermal conductivity of 30 W/mK, measured by pulsed photothermal reflectance, and the total thermal interface resistance between aluminum blocks was measured to be 60 Kmm 2 /W using an ASTM D5470 compliant 1-D measurement setup. This method of directly synthesizing CNTs on graphene films is more energy efficient and capable of larger volume production compared to traditional CVD methods. It is also compatible with scaling up towards continuous roll-to-roll production for large scale commercial production, one of the major limitations preventing CVD-grown CNTs from commercial applications
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| 8. |
- Huang, Shirong, et al.
(författare)
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Reliability of Graphene-based Films Used for High Power Electronics Packaging
- 2015
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Ingår i: 16th International Conference on Electronic Packaging Technology, ICEPT 2015, Changsha, China, 11-14 August 2015. - 9781467379991 ; , s. 852-855
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Konferensbidrag (refereegranskat)abstract
- Graphene-base film was fabricated with chemical conversion process, including graphene oxide (GO) prepared by Hummer's method, graphene oxide reduced with L-ascorbic acid (LAA), graphene based film deposited by vacuum filtration process. Meanwhile, the functionalization of the graphene-based film was performed to decrease the thermal interface resistance between the graphene-based film and substrate. Characterization data showed that the graphene-based film possessed high reliability after 500 hours under 85°C aging test. In summary, the graphene-based film can be a promising solution in thermal management of high power electronics.
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| 9. |
- 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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| 10. |
- 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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