Christopher Yap

Huazhong University of Science and Technology, Wu-han-shih, Hubei, China

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Publications (11)8.01 Total impact

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    ABSTRACT: Inspired by natural branching systems such as tree canopy, leaves, plant root, river basins, mammalian circulatory and respiratory systems, branching networks have been suggested for electronic component cooling. However, previous studies of tree-like branching networks have focused on symmetric structures although most natural tree-like branching systems are asymmetric. Furthermore, leaf-like branching networks have been rarely used and discussed. A three-dimensional model was formulated to compare the flow and heat transfer characteristics of symmetric/asymmetric tree-like branching networks and symmetric/asymmetric (offset) leaf-like branching networks. Results show that the influence of the asymmetry is very small for tree-like branching network at low branching number. Offset in leaf-like branching networks can reduce pressure drop significantly while maintaining maximum temperature difference between the inlet and outlet of the flowing fluid.
    International Journal of Thermal Sciences 02/2010; 49(2):272-280. · 2.47 Impact Factor
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    ABSTRACT: Several tree-shaped microchannel networks with/without loops are numerically examined and compared for application in cooling of electronic components. The physical model of microchannel electronic cooling system is set up with tree-shaped networks. The tree-shaped microchannel nets are embedded in a disk-shaped heat sink, which is attached to a chip to remove the heat dissipated by a chip. The effects of total branching level and loops on the thermal and flow performances of heat sink system are investigated numerically. Results show that tree-shaped nets with loops provide a great advantage when the structure experiences accidental damage to one or more channel segments since the loop assures continuity of coolant flow. Under blockage of some branches, the channel networks only experience an increase of pressure drop while maintaining the capability to remove the heat generated by the chip.
    International Journal of Thermal Sciences 11/2009; 48(11):2139-2147. · 2.47 Impact Factor
  • Xiang-Qi Wang, Christopher Yap, Arun S. Mujumdar
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    ABSTRACT: A numerical study is conducted to evaluate the thermal characteristics of a PCM-based heat sink which can be potentially used for cooling of mobile electronic devices such as personal digital assistants (PDAs) and notebooks. The heat sink consists of a conventional, extruded aluminum sink embedded with appropriate PCMs. Some important parameters, such as PCM volume fraction, temperature difference, aspect ratio, and PCM properties, were studied to investigate their effects on the thermal performance of the hybrid cooling system.
    International Journal of Thermal Sciences. 01/2008;
  • Xiang-Qi Wang, Arun S. Mujumdar, Christopher Yap
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    ABSTRACT: Tree-shaped microchannel networks are being considered for thermal designs that require high heat transfer densities for the cooling of modern electronics. Here we investigate the effect of the bifurcation angles in the constructal nets on the fluid flow and heat transfer characteristics of such networks using a three-dimensional computational fluid dynamics approach. Results show that the bifurcation angle is an important factor which determines the performance of such cooling nets. Surface temperature distributions and pressure drop along the flow paths are analyzed and compared. For the same boundary conditions, a lower temperature and pressure variation is observed at lower bifurcation angles.
    Journal of Applied Physics 11/2007; · 2.21 Impact Factor
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    ABSTRACT: Warped wafers can affect device performance, reliability, and linewidth control in various processing steps. We propose in this paper an in situ fault detection technique for wafer warpage in lithography. The use of advanced process control results in very small temperature disturbance making it suitable for industrial implementation
    IEEE Transactions on Semiconductor Manufacturing 03/2007; · 0.86 Impact Factor
  • Xiang-Qi Wang, Arun S. Mujumdar, Christopher Yap
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    ABSTRACT: Phase change material (PCM)-based heat sink, consisting of a conventional, extruded aluminum sink embedded with appropriate PCMs, can potentially be used for cooling of mobile electronic devices such as personal digital assistants (PDAs) and notebooks which are operated intermittently. During the use of such mobile devices, the orientation changes from time to time. A numerical investigation was carried out to study the effect of orientation of heat sink on the thermal performance of the combined cooling system to determine if it affects the thermal performance of a PCM-based cooling system significantly.
    International Communications in Heat and Mass Transfer. 01/2007;
  • Xiang-Qi Wang, Arun S. Mujumdar, Christopher Yap
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    ABSTRACT: Conventional parallel and serpentine microchannel nets have some inherent drawbacks such as the high pressure drop required and uneven temperature distribution achieved, which limit their wide applications. Since natural systems often give optimal solutions for many problems, the structure of living organism can provide ideas for the design of new microchannel cooling systems. In the current study, conjugated fluid flow and heat transfer through tree-shaped branching microchannel networks, which is embedded in a rectangular heat sink, was numerically investigated. A series of parametric tests were conducted for such microchannel networks. Results show that such channel networks have certain advantages over conventional parallel channel nets such as lower and more uniform temperature distribution and better stability in case of accidental blockage in channel segments.
    International Journal of Thermal Sciences. 01/2006;
  • Xiang-Qi Wang, Arun S. Mujumdar, Christopher Yap
    Journal of Electronic Packaging - J ELECTRON PACKAGING. 01/2006; 128(1).
  • Xiang-Qi Wang, Christopher Yap, Arun S. Mujumdar
    Journal of Electronic Packaging - J ELECTRON PACKAGING. 01/2006; 128(3).
  • Journal of Electronic Packaging - J ELECTRON PACKAGING. 01/2005; 127(3).
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    ABSTRACT: Wafer warpage is common in microelectronics processing. Warped wafers can affect device performance, reliability and linewidth control in various processing steps. We proposed in this paper an in-situ fault detection technique for wafer warpage in lithography. Early detection will minimize cost and processing time. Based on first principle thermal modeling, we are able to detect warpage fault from available temperature measurements. In this paper, the use of advanced process control resulted in very small temperature disturbance making it suitable for industrial implementation. More importantly, the sensitivity for detecting warpage is not compromised even though the temperature signal is small. Experimental results demonstrate the feasibility of the approach.
    Industrial Electronics Society, 2004. IECON 2004. 30th Annual Conference of IEEE; 12/2004