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  • Zhang, Dongsheng, et al. (författare)
  • Thermal properties of TIM using CNTs forest in electronics packaging
  • 2016
  • Ingår i: 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
  • Konferensbidrag (refereegranskat)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.
  • Zhang, Maomao, et al. (författare)
  • Effect of pressure during graphitization on mechanical properties of graphene films
  • 2019
  • Ingår i: 2019 20th International Conference on Electronic Packaging Technology, ICEPT 2019.
  • Konferensbidrag (refereegranskat)abstract
    • Graphene films (GFs) can be used in the field of electronics cooling, owing to many outstanding properties. In the present paper, GFs samples were graphitized at different pressures to study their effect on the mechanical properties. The elastic modulus and hardness of GFs were measured by nanoindentation and the tensile strength of GFs were obtained by stretching GFs in a tensile tester. Meanwhile, GFs were characterized by X-ray diffraction(XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. The results show that the modulus, hardness and tensile strength of GFs were strongly influenced by the defect and wrinkles among other things.
  • Zhang, Q., et al. (författare)
  • Effect of sintering method on properties of nanosilver paste
  • 2017
  • Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. ; , s. 186-189
  • 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.
  • Zhang, Q., et al. (författare)
  • Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles
  • 2019
  • Ingår i: Soldering and Surface Mount Technology. - 0954-0911. ; 31:4, s. 193-202
  • 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.
  • 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.
  • 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.
  • Zhang, Yan, 1976, et al. (författare)
  • Experimental and Modeling of the Stress-Strain Behavior of a BGA Interconnect Due to Thermal Load
  • 2008
  • Ingår i: Journal of Electronic Packaging, Transactions of the ASME. - 1528-9044 .- 1043-7398. ; 130:2, s. 0210101-0210107
  • Tidskriftsartikel (refereegranskat)abstract
    • A plastic ball grid array component interconnect has been experimentally investigated and modeled on the basis of micropolar theory. The experimental results were analyzed, and the data also provided the verification for the micropolar interface model. Two different interconnect cross sections, namely, one near the component boundary and the other in the center region beneath the chip, have been measured. The effects of thermal cycling on the interconnect deformation have been considered. The deformation fields, due to the mismatch of the material properties of the constituents in the assembly system, have been observed by means of a multifunction macro-micro-moiré interferometer, whereby the displacement distributions have been obtained and analyzed for the different specimens. The interconnect layer is usually of smaller size as compared to the neighboring component, and there are even finer internal structures included in the interconnect. The scale difference makes conventional methods time consuming and of low efficiency. An interface model based on the micropolar theory has been developed, cf. Zhang, Y., and Larsson, R., 2007, "Interface Modelling of ACA Flip-Chip Interconnects Using Micropolar Theory and Discontinuous Approximation," Comput. Struct., 85, pp. 1500-1513, Larsson, R., and Zhang, Y., 2007, "Homogenization of Microsystem Interconnects Based on Micropolar Theory and Discontinuous Kinematics, " J. Mech. Phys. Solids, 55, pp. 819-841, aiming at predicting the interconnect behavior under thermal load, especially when there exist internal structures in the interface and the component/ structure sizes vary in a wide range. Numerical simulations, using the micropolar interface model, show a fairly good agreement between the experimental data and the numerical simulations.
  • Zhang, Yan, 1976, et al. (författare)
  • Experimental Investigation and Micropolar Modelling of the Anisotropic Conductive Adhesive Flip-Chip Interconnection
  • 2008
  • Ingår i: Journal of Adhesion Science and Technology. - 0169-4243 .- 1568-5616. ; 22:14, s. 1717-1731
  • Tidskriftsartikel (refereegranskat)abstract
    • A conductive adhesive is a promising interconnection material for microsystem packaging. The interconnect features are of great importance to system responses under various loading conditions. The flip-chip packaging system with anisotropic conductive film (ACF) joint under thermal loadings has been investigated both experimentally and theoretically. The displacement distributions have been measured by an interferometer, which could provide the in-plane whole-field deformation observation. The interconnection is of much smaller scales compared with the neighbouring components such as the chip and substrate, and there are even finer internal structures involved in the joint. The wide scale range makes both experimental observation and conventional simulation difficult. A micropolar model is thus developed. Utilizing the homogenization, this model requires low computation resource. Combination of this model with a second-order model was able to produce a highly efficient and valid prediction of the packaging system response under thermal and mechanical loadings. Comparison of the micropolar model simulation and experimental data shows good agreement.
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