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1.
  • Du, Wenhui, et al. (författare)
  • New fast curing isotropic conductive adhesive for electronic packaging application
  • 2010
  • Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. ; :Article number 5582446, s. 199-201
  • Konferensbidrag (refereegranskat)abstract
    • With the rapid development of technologies on high density assembly and packaging in electronic industry, isotropic conductive adhesive (ICA) has been paid more and more attention as a potential substitute of solder, due to its advantages of low processing temperature, simple processing conditions and good manufacturability. However, the curing time of most traditional ICA is more than half an hour. The process duration of ICA is 2 or 3 times longer than that of solder. Thus, low efficiencies of energy using and product manufacturing has been one of factors which limits widely application of ICA. Generally, the curing speed of ICA depends on types and amount of curing agent as well as curing temperature. In our previous experiments, the effects of curing temperature and amount of curing agent have been investigated. So, the present work attempts to choose a new kind of curing agent to shorten process duration of ICA. By using new curing agent, the curing duration of ICA could be shortened in 5 minutes with a high curing rate compared with the previous version. In addition, the basic performance including bulk resistivity and viscosity are also investigated in this work. Finally, we present some discussions about the further optimization of performance, for example regarding the ways of achieving better electrical conductivity with lower filler content and improvement of viscosity etc. © 2010 IEEE.
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2.
  • Fu, Yifeng, 1984, et al. (författare)
  • Selective growth of double-walled carbon nanotubes on gold films
  • 2012
  • Ingår i: Materials Letters. - 0167-577X. ; 72, s. 78-80
  • Tidskriftsartikel (refereegranskat)abstract
    • Growth of high-quality vertical aligned carbon nanotube (CNT) structures on silicon supported gold (Au) films by thermal chemical vapor deposition (TCVD) is presented. Transmission electron microscopy (TEM) images show that the growth is highly selective. Statistical study reveals that 79.4% of the as-grown CNTs are double-walled. The CNTs synthesized on Au films are more porous than that synthesized on silicon substrates under the same conditions. Raman spectroscopy and electrical characterization performed on the as-grown double-walled CNTs (DWNTs) indicate that they are competitive with those CNTs grown on silicon substrates. Field emission tests show that closed-ended DWNTs have lower threshold field than those open-ended.
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3.
  • Fu, Yifeng, 1984, et al. (författare)
  • Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
  • 2012
  • Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
  • Tidskriftsartikel (refereegranskat)abstract
    • A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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4.
  • Lai, Huaxiang, et al. (författare)
  • Effects of BN and SiC nanoparticles on properties of conductive adhesive
  • 2010
  • Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. ; :Article number 5582434, s. 235-239
  • Konferensbidrag (refereegranskat)abstract
    • Isotropic conductive adhesives (ICAs) are a type of interconnect material used more and more widely in computer, robot, mobile phone, LED and so on. Compared with traditional solders, isotropic conductive adhesives have better working plasticity, creep resistance and heat resistance. In particular, isotropic conductive adhesives are more responsive in high density packaging than solder, which determines the dominance of ICAs in high density packaging in the future. In order to improve the thermal conductivity of ICA with acceptable electrical conductivity, Ag flakers, BN and SiC nanoparticles were added into the matrix. The content of silver flakes was 75wt%, and the content of nanoparticles (BN or SiC) in the isotropic conductive adhesives were 0wt%, 0.5wt%, 1.5wt%, 2.5wt%, 3wt%, 5wt% in weight. The conductive adhesives were coated on the PCBs with stencil printing and fifty SR1206 chip components were mounted on a PCB using conductive adhesive. All samples were cured at 150°for 1h. Further research into the reliability of the above isotropic conductive adhesives after temperature & humidity and thermal-cycling was carried out to analyze the effects of BN and SiC nanoparticals on the properties of ICA. The condition of the temperature & humidity test was 85 ° /85%RH, 500h. The thermal-cycling test was -40 °∼125°, 500 cycles and the soaking time and ramping rate were 19min and ±15°/min. Changes to electrical resistance were used to estimate the reliability of the isotropic conductive adhesives in this study. The microstructure of the failure samples was observed using a Scanning Electron Microscope (SEM). The water absorption of all ICAs is the same after 94h temperature and humidity aging and the rate of water absorption is also the same during the aging. The ICA with 3% boron nitride nanoparticles and 75% micron silver flakes shows the best temperature and humidity reliability, with the fewest cracks on the interface between ICA and component. After 500h thermal cycling aging, the resistance reduces in the first 100h and maintains in a certain value after 332h cycled thermal. The samples have no wide cracks but a few small ones on the interface. © 2010 IEEE.
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5.
  • Liu, Yangming, et al. (författare)
  • Numerical investigation on the thermal properties of the micro-cooler
  • 2010
  • Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. ; :Article number 5583917, s. 634-638
  • Konferensbidrag (refereegranskat)abstract
    • The micro-pin-fins prepared on the back side of the power chip enable heat removal on the level of modern microsystem demands. Carbon nanotube (CNT) has been proven to be a potential material for micro-cooler because of its superior advantages including high thermal conductivity, good mechanical property and so forth. And there emerges various applications of CNT in the micro-cooler system. In the present paper, micro-pin-fin heat sink with gas impinging jet as the cooling medium is analyzed. The heat dissipation of forced air convection cooling with micro-pin-fin structures made of aligned carbon nanotube arrays has been taken into consideration. The three-dimensional computational fluid dynamics (CFD) simulation was carried out. The temperature distribution and the pressure drop are studied in the cases of various geometrical parameters of the micro-pin-fin heat sinks at the same heating power prescribed. The fluid flow and the heat transfer phenomena in the micro-pin-fins heat sinks are investigated. The heat removal efficiency of the air microcooler is evaluated. An array of 8×8 fins with the optimized fin-to-base length ratio achieves the best cooling effect © 2010 IEEE.
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6.
  • Sun, Jie, 1977, et al. (författare)
  • Direct Chemical Vapor Deposition of Large-Area Carbon Thin Films on Gallium Nitride for Transparent Electrodes: A First Attempt
  • 2012
  • Ingår i: IEEE Transactions on Semiconductor Manufacturing. - 0894-6507. ; 25:3, s. 494-501
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct formation of large-area carbon thin films on gallium nitride by chemical vapor deposition without metallic catalysts is demonstrated. A high flow of ammonia is used to stabilize the surface of the GaN (0001)/sapphire substrate during the deposition at 950 degrees C. Various characterization methods verify that the synthesized thin films are largely sp(2) bonded, macroscopically uniform, and electrically conducting. The carbon thin films possess optical transparencies comparable to that of exfoliated graphene. This paper offers a viable route toward the use of carbon-based materials for future transparent electrodes in III-nitride optoelectronics, such as GaN-based light emitting diodes and laser diodes.
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7.
  • Tao, W., et al. (författare)
  • Reliability characterisation of bi-modal high temperature stable Isotropic Conductive Adhesives
  • 2010
  • Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010, Xian, 16-19 August 2010. ; :Article number 5582437, s. 225-228
  • Konferensbidrag (refereegranskat)abstract
    • Conductive adhesives are generally considered to be one of the strongest candidates for replacement of solder in electronics industry. However, some problems related to the performance have so far limited wider applications of conductive adhesives. One of the major problems is tendency to degrade during temperature and humidity aging. In this paper, two kinds of Isotropic Conductive Adhesives (ICA) with high temperature stable matrix and different fillers were fabricated. The first one was fabricated by simply adding silver flakes into matrix as filler using this high temperature stable matrix based on highly cross-linked aromatic functional groups. For the second one, in addition to silver flakes, nanosilver particles with different weight percentages were also added as filler into matrix to form a bi-modal ICA. The weight percentages of nano-silver particles in filler are 1wt%, 2wt% and 3wt% respectively. The filler content of these two ICAs are both 75wt% in total. All test samples were cured at 150°for 1 hour. The random distribution of the silver flakes in the adhesive was observed by SEM. The bulk resistivity of the ICAs with different fillers was investigated to characterize the electrical conductivity of the ICA. The results show that addition of small amount of nano-silver particles improve the electric conductivity of the ICA but the excessive amount of nano-silver particles led to the increase of the ICA's bulk resistivity. The humidity (85°/85RH) test was carried out and the resistances of the samples were measured. It was shown that some electrical resistance increase was observed during the humidity testing with time. The addition of the nano-particles has also some negative effect of the electrical resistance change. But the effect is limited in a few percentage range of the nano-particle addition.
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8.
  • Zhang, Xia, 1980, et al. (författare)
  • Design of Printed Monopole Antennas on Liquid Crystal Polymer Substrates
  • 2010
  • Ingår i: Journal of Infrared, Millimeter, and Terahertz Waves. - 1866-6892. ; 31:4, s. 469-480
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, a compact printed monopole antenna with an extremely wide bandwidth has been realized on Liquid Crystal Polymer (LCP) substrates by using standard processing technology. Both laminated and directed metalized LCP substrates were used in this experiment. The antenna made on the direct metalized LCP substrate performed well compared to on the laminated LCP substrate. To improve the adhesion, the surface of the LCP was further roughened and a certain adhesion layer was used prior to the deposition of Cu. The measured antenna on a metalized LCP substrate could cover this frequency band with an impedance bandwidth from 0.51 GHz to 14.4 GHz (28.2:1) for VSWRa parts per thousand currency sign2. Moreover, the antenna exhibits a nearly omni-directional radiation pattern. The size of this antenna is only about 0.18 lambda(1) x 0.13 lambda(1), where lambda(1) is the wavelength of the lowest operating frequency. The results show that LCP is a promising candidate for high frequency applications.
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9.
  • Zhang, X., et al. (författare)
  • Printed monopole antenna with extremely wide bandwidth on liquid crystal polymer substrates
  • 2011
  • Ingår i: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. ; , s. 1157-1159
  • Konferensbidrag (refereegranskat)abstract
    • This letter presents a printed monopole antenna with extremely wide bandwidth on a liquid crystal polymer (LCP) substrate. It consists of a hollowed elliptical monopole, two trapeziform ground planes and a tapered co-planar waveguide (CPW) feeder. By using standard processing technology, this monopole antenna is fabricated on the direct metalized LCP film substrate. The fabricated antenna can achieve an extremely wide impedance bandwidth, a nearly omnidirectional radiation pattern and a compact size, which verifies that LCP materials are very suitable as substrates for commercial wireless applications.
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10.
  • Zhang, Yan, et al. (författare)
  • Numerical investigation on thermal properties of micro-pin-fin cooler
  • 2011
  • Ingår i: Journal of Shanghai University. - 1007-6417. ; 15:4, s. 273 - 278
  • Tidskriftsartikel (refereegranskat)abstract
    • Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes (CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.
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