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This paper presents numerical simulations based on the concept of local and global dimensional analysis to reproduce the thermodynamics and aerodynamics of server-fins, i.e., detachable flat/curved fins on the inlet/outlet of a server, for enhancing energy efficiency in data centers. Server-fin designs, combinations of shapes and opening angles, are evaluated by transient analysis, vorticity analysis,...
Improved-efficiency heat spreaders must address ergonomic- and performance-driven thermal management demands of electronic devices of increasingly thin form factor. Heat pipes offer a potential high-conductance solution, but performance limitations unique to sub-millimeter thickness devices must be characterized. Using a reduced-order, one-dimensional resistance network and a two-dimensional numerical...
Stress sensing test chips are a powerful tool for measuring in-situ stresses in electronic packages. In this study, we have applied (111) silicon test chips to perform a variety of measurements of moisture and thermally induced die stresses in flip chip on laminate assemblies. The developed chips incorporated optimized eight-element sensor rosettes that were capable of measuring the complete state...
In this paper, an experimental investigation of the effects of droplet diameters on the Leidenfrost temperature and its shifts has been carried out. Tests were conducted on a 304 stainless steel polished surface and a stainless steel surface which was processed by a femtosecond laser to form Above Surface Growth (ASG) nano/microstructures. To determine the Leidenfrost temperatures, the droplet lifetime...
An ultra-thin polymer pulsating heat pipe (PPHP) was developed by forming with UV curable polymer resin on polyethylene terephthalate films and hydrofluoroether was used as a working fluid. The casing materials were selected in consideration of compatibility between case materials and the working fluid and also the heat and pressure durability. A new apparatus was constructed to evaluate the thermal...
Flow boiling microgap heat sink is attractive due to its high heat transfer capability in compact spaces with a smaller rate of coolant flow than its single phase counterpart. Other advantages of this method are the ease of fabrication and implementation (direct cooling). Although there is general agreement that this system may be able to maintain greater temperature uniformity across the heat sink...
Recently, high thermally conductive polymers have emerged as low cost and energy efficient alternatives to traditional use of metals in heat transfer applications. Here, we present development of ultra-high molecular weight polyethylene (UHMWPE) thin films with high thermal conductivity. The fabrication platform is based on a sol-gel process followed by mechanical drawing. After gel formation and...
Topic is feedback stabilisation of a nonlinear pool-boiling system in three spatial dimensions (3D). Regulation of its unstable (non-uniform) equilibria has great potential for application in micro-electronics cooling and thermal-management systems. Here, as a first step, stabilisation of such 3D equilibria is considered. A control law is designed that regulates the heat supply to the heater as a...
In this paper, a phase change material (PCM) based heat sink was proposed and its geometry was optimized for heat transfer enhancement. The thermal resistance network between the heat source and the control volume was applied to analyze the influence on heat storage performance of the phase change material based heat sink (PCMBHS) and the optimization suggestions were proposed. Besides, the heat storage...
Metal-PCM (Phase Change Material) composite heat spreaders offer a combination of high effective thermal conductivity and high density heat storage capability that are desirable for transient thermal management applications, especially in mobile and wearable electronic devices. In this study, we propose fabrication of microporous metal matrix (MMM)-PCM composite heat spreaders through electrodeposition...
This paper deals with the system design, technology and test of a novel concept of integrating Silicon power dies along with thermo-electric coolers and a phase change heat buffer in order to thermally manage transients occurring during operation. The concept features double-sided cooling as well as new materials and joining technologies to integrate the dies such as transient liquid phase bonding/soldering...
In this effort, theoretical modeling was employed to understand the impact of bypass on the flow performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink and the bypass regions were applied and a generic parameter, referred as the Flow Bypass Factor, was identified from the theoretical solution that mathematically captures the...
Solid-liquid phase change materials (PCMs) can be used as a transient thermal management technique due to their ability to store significant amounts of heat through the solid liquid phase change. It is common to improve the low thermal conductivity of PCMs by adding nanoparticles, however, this addition changes some of the physical properties of the material, including viscosity, possibly hindering...
Presence of a thermal enabling load applied to Ball Grid Array (BGA) components creates a distinctive set of evaluations to be completed for reliability of solder joints (SJ) that connect the BGA to the board. This becomes especially relevant for newer technologies that drive to smaller component form factors. In this comprehensive study, a computational mechanics based Design of Experiments approach...
Mechanical integrity of the dielectric stack is challenged by the trend towards porous, lower dielectric constant interlayer dielectric (ILD) materials. As a result, fracture in the ILD stacks caused either by assembly process or by the dicing process is an important reliability consideration. In general, there is a need to either assess the propensity of the structure to fracture under assembly conditions,...
Modern electronics feature high surface heat fluxes, particularly at localized hot spots, which can be detrimental to chip performance. While techniques have been developed to alleviate these local effects, they are typically advanced solutions using embedded cooling devices. Instead, an effective, less aggressive solution involves the adaptation of traditional micro-channel cooling to the particular...
Three dimensional (3D) stacking of semiconductor chips has the advantages of high electrical performance, including improved bandwidth, reduced wire interconnection lengths, low cost, and heterogeneous integration. However, the power density increases sharply within the stack and the thermal management challenges become major bottlenecks. Inter-tier microfluidic cooling with microgaps with surface...
In this study, several 2D numerical simulations on a non-Newtonian flow over a confined cylinder placed in a rectangular microchannel are carried out at different Weissenberg (Wi) numbers. In particular, the Oldroyd-B model implemented in open source code OpenFOAM is employed to capture the three basic ingredients of polymer rheology, viz., anisotropy, elasticity and relaxation. Numerical calculations...
In recent years, there is increasing interest in copper wirebond technology as an alternative to gold wirebond in microelectronic devices due to its superior electrical performance and low cost. At present, validated constitutive models for the strain rate and temperature dependent behavior of Cu free air ball (FAB) appear to be largely missing in the literature. The lack of reliable constitutive...
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