Showing papers on "Heat sink published in 2010"

Design, Fabrication, and Characterization of CMOS MEMS-Based Thermoelectric Power Generators

Abstract: This paper presents the design, modeling, fabrication, and characterization of CMOS microelectromechanical-systems-based thermoelectric power generators (TPGs) to convert waste heat into a few microwatts of electrical power. Phosphorus and boron heavily doped polysilicon thin films are patterned and electrically connected to consist thermopiles in the TPGs. To optimize heat flux, the thermal legs are embedded between the top and bottom vacuum cavities, which are sealed on the wafer level at low temperature. A heat-sink layer is coated on the cold side of the device to effectively disperse heat from the cold side of the device to ambient air. The peripheral cavity is designed to isolate heat from the surrounding silicon substrate. Both simulation and experiments are implemented to validate that the energy conversion efficiency is highly improved due to the aforementioned three unique designs. The device has been fabricated by a CMOS-compatible process. Properties of thermoelectric material, such as the Seebeck coefficient, electrical resistivity, and specific contact resistance are measured through test structures. For a device in the size of 1 cm2 and with a 5-K temperature difference across the two sides, the open-circuit voltage is 16.7 V and the output power is 1.3 ?W under matched load resistance. Such energy can be efficiently accumulated as useful electricity over time and can prolong the battery life.

Led light bulbs for space lighting

Abstract: The invention discloses a three dimensional Ϊ..ED arrangement and heat management method using a heat transfer or conduction pipe to enable rapid heat transfer from a three dimensional cluster of LEDs to a heatsink with or without active cooling, the Sight emitted from tile three dimensional cluster not being obstructed by a heat sink arrangement such that the light beam profile generated by the light appears similar to that generated by traditional incandescent bulbs

Heat sinks and lamp incorporating same

Abstract: A lamp (600) comprising a solid state light emitter (450), the lamp being an A lamp and providing a wall plug efficiency of at least 90 lumens per Watt. Also, a lamp (400) comprising a solid state light emitter (450) and a power supply, the emitter being mounted on a heat dissipation element (420), the dissipation element being spaced from the power supply. Also, a lamp, comprising a solid state light emitter and a heat dissipation element that has a heat dissipation chamber, whereby an ambient medium can enter the chamber, pass through the chamber, and exit. Also, a lamp(10), comprising a light transmissive housing (12) at least one solid state lighting emitter and a first heat dissipation element. Also, a lamp comprising a heat sink comprising a heat dissipation chamber. Also, a lamp comprising first and second heat dissipation elements. Also, a lamp comprising means (74) for creating flow of ambient fluid.

Troffer-style fixture

Abstract: An indirect troffer (100). Embodiments of the present invention provide a troffer- style fixture that is particularly well -suited for use with solid state light sources, such as LEDs. The troffer comprises a light engine unit (102) that is surrounded on its perimeter by a reflective pan (104). A back reflector (404) defines a reflective interior surface of the light engine (102). To facilitate thermal dissipation, a heat sink (406) is disposed proximate to the back reflector (404). A portion of the heat sink is exposed to the ambient room environment while another portion functions as a mount surface for the light sources that faces the back reflector (404). One or more light sources disposed along the heat sink mount surface emit light into an interior cavity where it can be mixed and/or shaped prior to emission. In some embodiments, one or more lens plates (410) extend from the heat sink (406) out to the back reflector (404).

Analytical and Numerical Modeling of the Thermal Performance of Three-Dimensional Integrated Circuits

Abstract: Three-dimensional (3D) interconnection technology offers several electrical advantages, including reduced signal delay, reduced interconnect power, and design flexibility. 3D integration relies on through-silicon vias (TSVs) and the bonding of multiple active layers to stack several die or wafers containing integrated circuits (ICs) and provide direct electrical interconnection between the stacked strata. While this approach provides several electrical benefits, it also offers significant challenges in thermal management. While some work has been done in the past in this field, a comprehensive treatment is still lacking. In the current work, analytical and finite-element models of heat transfer in stacked 3D ICs are developed. The models are used to investigate the limits of thermal feasibility of 3D electronics and to determine the improvements required in traditional packaging in order to accommodate 3D ICs. An analytical model for temperature distribution in a multidie stack with multiple heat sources is developed. The analytical model is used to extend the traditional concept of a single-valued junction-to-air thermal resistance in an IC to thermal resistance and thermal sensitivity matrices for a 3D IC. The impact of various geometric parameters and thermophysical properties on thermal performance of a 3D IC is investigated. It is shown that package and heat sink thermal resistances play a more important role in determining temperature rise compared to thermal resistances intrinsic to the multidie stack. The improvement required in package and heat sink thermal resistances for a 3D logic-on-memory implementation to be thermally feasible is quantified. An increase in maximum temperature in a 3D IC compared to an equivalent system-in-package (SiP) is predicted. This increase is found to be mainly due to the reduced chip footprint. The increased memory die temperature in case of memory-on-logic integration compared to a SiP implementation is identified to be a significant thermal management challenge in the future. The results presented in this paper may be useful in the development of thermal design guidelines for 3D ICs, which are expected to help maximize the electrical benefits of 3D technology without exacerbating thermal management issues when implemented in early-stage electrical design and layout tools.

Semiconductor device and method of manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To make a substrate size small and to improve durability by reducing thermal stress of solder while preventing heat dissipation from decreasing owing to a void in spite of use of lead-free solder, with respect to a semiconductor device having semiconductor elements bonded to one surface of an insulating substrate made of a ceramic substrate having metal plates bonded to both surfaces and also having a metallic heat sink bonded to the other surface via the lead-free solder. SOLUTION: The semiconductor elements S, S' are bonded to the insulating substrate P such that two or more semiconductor elements of the same kind are not mounted on the one insulating substrate P, and the area A of a surface of the second metal plate M2 which is opposed to the heat sink B is set to be 1 to 2.5 times as large as the overall area At of the semiconductor elements S, S'. COPYRIGHT: (C)2011,JPO&INPIT

Experimental Investigation of an Ultrathin Manifold Microchannel Heat Sink for Liquid-Cooled Chips

Abstract: We report an experimental investigation of a novel, high performance ultrathin manifold microchannel heat sink. The heat sink consists of impinging liquid slot-jets on a structured surface fed with liquid coolant by an overlying two-dimensional manifold. We developed a fabrication and packaging procedure to manufacture prototypes by means of standard microprocessing. A closed fluid loop for precise hydrodynamic and thermal characterization of six different test vehicles was built. We studied the influence of the number of manifold systems, the width of the heat transfer microchannels, the volumetric flow rate, and the pumping power on the hydrodynamic and thermal performance of the heat sink. A design with 12.5 manifold systems and 25 μm wide microchannels as the heat transfer structure provided the optimum choice of design parameters. For a volumetric flow rate of 1.3 l/min we demonstrated a total thermal resistance between the maximum heater temperature and fluid inlet temperature of 0.09 cm 2 K/W with a pressure drop of 0.22 bar on a 2 ×2 cm 2 chip. This allows for cooling power densities of more than 700 W/cm 2 for a maximum temperature difference between the chip and the fluid inlet of 65 K. The total height of the heat sink did not exceed 2 mm, and includes a 500 μm thick thermal test chip structured by 300 μm deep microchannels for heat transfer. Furthermore, we discuss the influence of elevated fluid inlet temperatures, allowing possible reuse of the thermal energy, and demonstrate an enhancement of the heat sink cooling efficiency of more than 40% for a temperature rise of 50 K.

Integrated Microfluidic Cooling and Interconnects for 2D and 3D Chips

Abstract: Power dissipation in microprocessors is projected to reach a level that may necessitate chip-level liquid cooling in the near future. An on-chip microchannel heat sink can reduce the total thermal interfaces between an integrated circuit chip and the convective cooling medium and therefore yield smaller junction-to-ambient thermal resistance. This paper reports the fabrication, assembly, and testing of a silicon chip with complementary metal-oxide-semiconductor process compatible microchannel heat sink and thermofluidic chip input/output (I/O) interconnects fabricated using wafer-level batch processing. Ultra-small form factor, low-cost fabrication and assembly (system integration) are achieved for 2D and 3D chips, as the microchannel heat sink is fabricated directly on back-side of each chip. Through-wafer electrical and fluidic vias are used to interconnect the monolithically integrated microchannel heat sink to thermofluidic chip I/O interconnections. The feasibility of the novel fluidic I/O interconnect is demonstrated through preliminary thermal resistance measurements.

Entropy Generation Analysis for Nanofluid Flow in Microchannels

Abstract: Employing a validated computer simulation model, entropy generation is analyzed in trapezoidal microchannels for steady laminar flow of pure water and CuO-water nanofluids. Focusing on microchannel heat sink applications, local and volumetric entropy rates caused by frictional and thermal effects are computed for different coolants, inlet temperatures, Reynolds numbers, and channel aspect ratios. It was found that there exists an optimal Reynolds number range to operate the system due to the characteristics of the two different entropy sources, both related to the inlet Reynolds number. Microchannels with high aspect ratios have a lower suitable operational Reynolds number range. The employment of nanofluids can further minimize entropy generation because of their superior thermal properties. Heat transfer induced entropy generation is dominant for typical microheating systems while frictional entropy generation becomes more and more important with the increase in fluid inlet velocity/Reynolds number.

Low profile light

Abstract: A luminaire includes a heat spreader and a heat sink thermally coupled to and disposed diametrically outboard of the heat spreader, an outer optic securely retained relative to at least one of the heat spreader and the heat sink, and a light source disposed in thermal communication with the heat spreader, the light source having a plurality of light emitting diodes (LEDs). The heat spreader, the heat sink and the outer optic, in combination, have an overall height H and an overall outside dimension D such that the ratio of H/D is equal to or less than 0.25. The combination defined by the heat spreader, the heat sink and the outer optic, is so dimensioned as to: cover an opening defined by a nominally sized four-inch can light fixture; and, cover an opening defined by a nominally sized four-inch electrical junction box.

Thermal Characterization of Interlayer Microfluidic Cooling of Three-Dimensional Integrated Circuits With Nonuniform Heat Flux

Abstract: It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ∼300 W/cm 2 . In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer.

Numerical analysis of deterioration in heat transfer to near-critical rocket propellants

Abstract: Liquid propellants, which are typically used for regenerative cooling of rocket thrust chambers, can flow in channels at supercritical pressures and in the neighborhood of pseudocritical temperature (near-critical fluid). This could be for instance the case for the envisioned liquid-oxygen/liquid-methane engines with chamber pressures larger than about 50 bar. When the fluid is in such a near-critical condition, deterioration in heat transfer can occur if the heat transfer level is higher than a threshold value. Aiming to improve flow prediction capabilities for the design of such systems, the present study is devoted to numerical simulations of near-critical fluids flowing in uniformly heated straight tubes. After code validation against experimental data of near-critical-hydrogen flow, numerical simulations of near-critical-methane flow in heated tubes are carried out, each characterized by a different wall heat flux. Results are discussed in detail and the near-critical-methane flow condition that exhi...