| 1. |
- Banerjee, Debashree, et al.
(author)
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Elevated thermoelectric figure of merit of n-type amorphous silicon by efficient electrical doping process
- 2018
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In: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 44, s. 89-94
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Journal article (peer-reviewed)abstract
- The currently dominant thermoelectric (TE) materials used in low to medium temperature range contain Tellurium that is rare and mild-toxic. Silicon is earth abundant and environment friendly, but it is characterized by a poor TE efficiency with a low figure of merit, ZT. In this work, we report that ZT of amorphous silicon (a-Si) thin films can be enhanced by 7 orders of magnitude, reaching ∼0.64 ± 0.13 at room temperature, by means of arsenic ion implantation followed by low-temperature dopant activation. The dopant introduction employed represents a highly controllable doping technique used in standard silicon technology. It is found that the significant enhancement of ZT achieved is primarily due to a significant improvement of electrical conductivity by doping without crystallization so as to maintain the thermal conductivity and Seebeck coefficient at the level determined by the amorphous state of the silicon films. Our results open up a new route towards enabling a-Si as a prominent TE material for cost-efficient and environment-friendly TE applications at room temperature.
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| 2. |
- Zhang, Q., et al.
(author)
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Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles
- 2019
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In: Soldering and Surface Mount Technology. - 1758-6836 .- 0954-0911. ; 31:4, s. 193-202
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Journal article (peer-reviewed)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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| 3. |
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| 4. |
- Zhang, Y., et al.
(author)
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MDS study on tensile properties of defective graphene sheet
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
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Conference paper (peer-reviewed)abstract
- Low-dimensional materials such as graphene exhibit superior electrical, mechanical and thermal properties. However, structural defects occur during the growth or treatment process of carbon nanomaterial and greatly affect the material properties. In this paper, molecular dynamics simulation methods are used to study the effects of atomic defects in graphene sheets on the tensile strength, and the vacancy type and defect orientation are considered in the cases of graphene sheets under various mechanical loadings. The simulation results show that for the graphene sheets with structural defects, the fracture starts near the original vacancy position. The tensile strength of the graphene sheets with X1-type vacancy defects under zigzag direction is reduced by about 26.9% compared with that of the defect-free graphene sheet, while the graphene sheet with X2-type vacancy defects shows the least decrease in magnitude, which is 9.5% lower than that of the perfect graphene sheet. When stretched in the armchair direction, the tensile strength of the graphene sheet with H2 vacancy defects was greatly reduced by 27.1%, and the X1 vacancy defects shows the least influence, where tensile strength of the graphene sheets was reduced by 11.2%.
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| 5. |
- Chen, Jiajia, et al.
(author)
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Characterization of Longitudinal Thermal Conductivity of Graphene Film
- 2021
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In: 2021 22nd International Conference on Electronic Packaging Technology, ICEPT 2021.
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Conference paper (peer-reviewed)abstract
- The chase of high performance by chip manufacturers has greatly increased the power consumption of integrated circuits, which brings great challenges to the heat dissipation of electronics systems. It has also slowed down following up of the Moore's Law, and it is expected to hit the wall soon [1]. Graphene film with high in-plane thermal conductivity is one of the key materials to make it possible for electronics industry to continue to follow the Moore's Law. However, there are few studies focusing on the longitudinal thermal conductivity of graphene films. The purpose of this study is to investigate the longitudinal thermal conductivity of graphene films according to ASTM D5470 [2]. The results show that the longitudinal thermal conductivity of the pressed graphene film is greater than that of the unpressurized graphene film. The longitudinal thermal conductivity is 10.6 W/m· K for the unpressurized graphene film and 20.6 W/m· K for the pressed graphene film.
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| 6. |
- Lu, Xiuzhen, et al.
(author)
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The influence of sintering process on thermal properties of nano-silver paste
- 2018
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In: 2018 19TH INTERNATIONAL CONFERENCE ON ELECTRONIC PACKAGING TECHNOLOGY (ICEPT). - 9781538663868 - 9781538663868 ; , s. 1157-1160
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Conference paper (peer-reviewed)abstract
- Nano-silver paste with low sintering temperature and high operation temperature was introduced to the application of bonding materials for GaN and SiC devices. Thermal properties are critical issues for die attach materials due to the heat dissipation requirements of high power devices. The influence of sintering process parameters for nano-silver paste on the thermal properties was investigated. The thermal conductivity of sintered nano-silver paste increased with the increase of sintering temperature and sintering time because of the dense structure due to high temperature and long sintering time. To improve the thermal property, Ag coated micro-SiC particles were used as an alternative to partly replace pure nano-Ag particles. The results demonstrate that the SiC particles can reduce the voids and improve the density of the sintered silver structure. Moreover, the addition of SiC particles can also contribute to the increase of thermal diffusivity. As a result, the thermal conductivity of sintered silver paste with 1.5 wt.% Ag coated SiC particles was two times as compared to that without SiC particles with the same Ag concentration.
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| 7. |
- Zehri, Abdelhafid, 1989, et al.
(author)
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High porosity and light weight graphene foam heat sink and phase change material container for thermal management
- 2020
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In: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42
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Journal article (peer-reviewed)abstract
- During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m(-1)K(-1), while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.
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| 8. |
- Zehri, Abdelhafid, 1989, et al.
(author)
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Low-Temperature Sintering Bimodal Micro Copper-Nano Silver for Electrical Power Devices
- 2018
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In: 2018 7th Electronic System-Integration Technology Conference (ESTC). - 9781538668146
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Conference paper (peer-reviewed)abstract
- Copper is generally considered as an electronic packaging material due to its good electrical, thermal properties and relatively low cost. However, copper needs high processing temperature, which negatively affects the electronics reliability. In this paper, silver nanoparticles sintering is evaluated for the propose to decrease the processing temperature of copper. Different fractions of silver nanoparticles were mixed with 10 ×m Cu powder and sintered at temperatures of 250°C, 300°C, 400°C and 500°C, under low pressures 4MPa and 8MPa, and a high pressure of 100MPa for comparison. Densities from 45% to 94% of the density of bulk Cu have been achieved while the thermal and electrical conductivities have been evaluated and reached a value of around 270W/m.K and 1.41×106 S/m.
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| 9. |
- Zhang, Dongsheng, et al.
(author)
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Thermal properties of TIM using CNTs forest in electronics packaging
- 2016
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In: 2016 17th International Conference on Electronic Packaging Technology, ICEPT 2016; Wuhan Optics Valley Kingdom Hotel Wuhan; China; 16 August 2016 through 19 August 2016. ; , s. 1355-1359
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Conference paper (peer-reviewed)abstract
- Thermal interface material (TIM) is applied to fill the air gaps of interfaces, which provides a path for interfacial heat transfer. Owing to the exceptional thermal properties of carbon nanotubes (CNT), TIMs based on CNTs have received much attention in recent years. In this study, heat dissipation performance of vertically aligned carbon nanotubes (VACNT) arrays as TIM in electronic packing was analyzed. Vertically aligned carbon nanotubes with length of 245?m and 763?m were synthesized on a silicon substrate by chemical vapor deposition respectively. Morphology of the vertically aligned carbon nanotubes was characterized by scanning electron microscope. The hotspot temperature of thermal test chip with vertically aligned carbon nanotubes were characterized by resistance temperature detector method and infrared imaging method.
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| 10. |
- Zhou, Chenfei, et al.
(author)
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A novel nano-Ag paste with Ag-rGO and its application in GF/Cu laminated structure
- 2022
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In: 2022 23rd International Conference on Electronic Packaging Technology, ICEPT 2022.
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Conference paper (peer-reviewed)abstract
- The high contact thermal resistance of the interface between graphene films (GF) and substrates has become one of the key obstacles for the application of GF in electronic devices. A novel nano-Ag paste with nano-Ag particles modified reduced graphene oxide (Ag-rGO) was introduced to enhance the heat transport via the interface of GF and substrate. The influence of the content of Ag-rGO on shear strength and electrical resistivity of sintered Ag structure was investigated. The maximum shear strength and the minimum electrical resistivity were got for sintered Ag structure with 0.5 wt.% Ag-rGO. Reduced contact thermal resistance of GF and Cu substrate (GF/Cu) laminated structure was gained by using sintered Ag structure with Ag-rGO as interconnect materials. The minimum value of the thermal resistance of 2.02 ± 0.26 mm2·K/W was obtained for GF/Cu laminated structure connected by sintered Ag structure with 1 wt.% Ag-rGO.
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