Development of a High Performance Vapor Chamber for High Heat Flux Applications

2008 ◽  
Author(s):  
Yuan Zhao ◽  
Chung-Lung Chen
Keyword(s):  
Heat Flux ◽  
High Performance ◽  
Experimental Tests ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Porous Network ◽  
Heat Spreader ◽  
Wick Structure

This paper introduces a high performance vapor chamber heat spreader with a novel bi-dispersed wick structure. The main wick structure is a sintered porous network in a latticed pattern, which contains not only small pores to transport liquid by capillary forces, but also many slots to provide large passages to vent vapor from heated surfaces. The copper particles have a diameter of approximately 50 μm; they produce an effective pore radius of approximately 13 μm after sintering. The slots have a typical width of approximately 500 μm. Unlike traditional bi-dispersed wick structures, the latticed wick structures provide undisrupted liquid delivery passages and vapor escape channels and thus greatly improve the heat transfer performance. Preliminary experimental tests were conducted and the results were analyzed. It was shown by the experiments that vapor chamber heat spreaders with the latticed wicks present three times improvement on heat spreading performance, comparing with a solid copper heat spreader, and much improved capacity to handle hot spots with local heat fluxes exceeding 300 W/cm2, which will have great impacts on extending heat pipe technology from traditional low to medium heat fluxes to high heat flux applications.

Integrated Vapor Chamber Heat Spreader for Power Module Applications

2017 ◽  
Author(s):  
Clayton L. Hose ◽  
Dimeji Ibitayo ◽  
Lauren M. Boteler ◽  
Jens Weyant ◽  
Bradley Richard
Keyword(s):  
Heat Flux ◽  
Thermal Resistance ◽  
Power Electronics ◽  
Coefficient Of Thermal Expansion ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Power Module ◽  
Heat Spreader

This work presents a demonstration of a coefficient of thermal expansion (CTE) matched, high heat flux vapor chamber directly integrated onto the backside of a direct bond copper (DBC) substrate to improve heat spreading and reduce thermal resistance of power electronics modules. Typical vapor chambers are designed to operate at heat fluxes > 25 W/cm2 with overall thermal resistances < 0.20 °C/W. Due to the rising demands for increased thermal performance in high power electronics modules, this vapor chamber has been designed as a passive, drop-in replacement for a standard heat spreader. In order to operate with device heat fluxes >500 W/cm2 while maintaining low thermal resistance, a planar vapor chamber is positioned onto the backside of the power substrate, which incorporates a specially designed wick directly beneath the active heat dissipating components to balance liquid return and vapor mass flow. In addition to the high heat flux capability, the vapor chamber is designed to be CTE matched to reduce thermally induced stresses. Modeling results showed effective thermal conductivities of up to 950 W/m-K, which is 5 times better than standard copper-molybdenum (CuMo) heat spreaders. Experimental results show a 43°C reduction in device temperature compared to a standard solid CuMo heat spreader at a heat flux of 520 W/cm2.

Nano-Structured Two-Phase Heat Spreader for Cooling Ultra-High Heat Flux Sources

2010 ◽  
Author(s):  
Mitsuo Hashimoto ◽  
Hiroto Kasai ◽  
Kazuma Usami ◽  
Hiroyuki Ryoson ◽  
Kazuaki Yazawa ◽  
...  
Keyword(s):  
Heat Flux ◽  
Copper Powder ◽  
High Heat ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Heat Spreader ◽  
Two Phase ◽  
Evaporator Temperature ◽  
Sintered Copper ◽  
Multi Walled Carbon Nanotubes

A two-phase heat spreader has been developed for cooling high heat flux sources in high-power lasers, high-intensity light-emitting diodes, and semiconductor power devices. The heat spreader targets the passive cooling of heat sources with fluxes greater than 5 W/mm2 without requiring any active power consumption for the thermal solution. The prototype vapor chamber consists of an evaporator plate, a condenser plate and an adiabatic section, with water as the phase-change fluid. The custom-designed high heat flux source is composed of a platinum resistive heating pattern and a temperature sensor on an aluminum nitride substrate which is soldered to the outside of the evaporator. Experiments were performed with several different microstructures as evaporator surfaces under varying heat loads. The first microstructure investigated, a screen mesh, dissipated 2 W/mm2 of heat load but with an unacceptably high evaporator temperature. A sintered copper powder microstructure with particles of 50 μm mean diameter supported 8.5 W/mm2 without dryout. Four sets of particle diameters and different thicknesses for the sintered copper powder evaporators were tested. Additionally, some of the sintered structures were coated with multi-walled carbon nanotubes (CNT) that were rendered hydrophilic. Such nano-structured evaporators successfully showed a further reduction in thermal resistance of the vapor chamber.

A Vapor Chamber Using Graphite Foams as Wicks for Cooling High Heat Flux Electronics

2005 ◽  
Author(s):  
Minhua Lu ◽  
Larry Mok ◽  
R. J. Bezama
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
High Heat ◽  
High Thermal Conductivity ◽  
Working Fluid ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Capillary Limit ◽  
Wick Structure ◽  
Graphite Foam

A vapor chamber using high thermal conductivity and permeability graphite foam as a wick has been designed, built and tested. With ethanol as the working fluid, the vapor chamber has been demonstrated at a heat flux of 80 W/cm2. The effects of the capillary limit, the boiling limit, and the thermal resistance in restricting the overall performance of a vapor chamber have been analyzed. Because of the high thermal conductivity of the graphite foams, the modeling results show that the performance of a vapor chamber using a graphite foam is about twice that of one using a copper wick structure. Furthermore, if water is used as the working fluid instead of ethanol, the performance of the vapor chamber will be increased further. Graphite foam vapor chambers with water as the working fluid can be made by treating the graphite foam with an oxygen plasma to improve the wetting of the graphite by the water.

Development of Micro/Nano Engineered Wick-Based Passive Heat Spreaders for Thermal Management of High Power Electronic Devices

2011 ◽  
Author(s):  
David H. Altman ◽  
Joseph R. Wasniewski ◽  
Mark T. North ◽  
Sungwon S. Kim ◽  
Timothy S. Fisher
Keyword(s):  
Heat Flux ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
High Heat ◽  
Test Facility ◽  
Great Promise ◽  
High Heat Flux ◽  
Vapor Chamber ◽  
Heat Spreader

Spreading of high-flux electronics heat is a critical part of any packaging design. This need is particularly profound in advanced devices where the dissipated heat fluxes have been driven well over 100W/cm2. To address this challenge, researchers at Raytheon, Thermacore and Purdue are engaged in the development and characterization of a low resistance, coefficient of thermal expansion (CTE)-matched multi-chip vapor chamber heat spreader, which utilizes capillary driven two-phase heat transport. The vapor chamber technology under development overcomes the limitations of state-of-the-art approaches by combining scaled-down sintered Cu powder and nanostructured materials in the vapor chamber wick to achieve low thermal resistance. Cu-coated vertically aligned carbon nanotubes is the nanostructure of choice in this development. Unique design and construction techniques are employed to achieve CTE-matching with a variety of device and packaging materials in a low-profile form-factor. This paper describes the materials, design, construction and characterization of these vapor chambers. Results from experiments conducted using a unique high-heat flux capable 1DSS test facility are presented, exploring the effects of various microscopic wick configurations, CNT-functionalizations and fluid charges on thermal performance. The impacts of evaporator wick patterning, CNT evaporator functionalization and CNT condenser functionalization on performance are assessed and compared to monolithic Cu wick configurations. Thermal performance is explained as a function of applied heat flux and temperature through the identification of dominant component thermal resistances and heat transfer mechanisms. Finally, thermal performance results are compared to an equivalent solid conductor heat spreader, demonstrating a >40% reduction in thermal resistance. These results indicate great promise for the use of such novel vapor chamber technology in thickness-constrained high heat flux device packaging applications.

Investigations of High Heat Flux Cooling Using Carbon Nanotube Bi-Wick Structure and Integrated Platinum Thermometer/Heater

2009 ◽  
Author(s):  
Qingjun Cai ◽  
Yuan Zhao ◽  
Chialun Tsai ◽  
Chung-lung Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Carbon Nanotube ◽  
High Performance ◽  
Empty Space ◽  
High Heat ◽  
High Heat Flux ◽  
Resistance Variation ◽  
Wick Structure ◽  
Reliable Temperature

With the increase of power consumption in compact electronic devices, passive heat transfer cooling technologies with high heat flux characteristics are highly desired in microelectronics industries. Carbon nanotube (CNT) cluster/forest has high effective thermal conductivity, nano pore size and large porosity, which can be used as wick structure in a heat pipe heatspreader and provides high capillary force for high heat flux thermal management. In this research, investigations of high heat flux cooling of the CNT bi-wick structure are associated with the development of a reliable thermometer and high performance/interface free heater. A 100nm thick and 600μm wide Z-shaped platinum wire resistor is fabricated on the backside of a CNT sample substrate to heat a 2×2mm2 wick area. As a heater, it provides direct heating effect without thermal interface and is capable of over 800°C high temperature operation. As a thermometer, reliable temperature measurement is achieved by calibrating the resistance variation with temperature after the annealing process is applied. The CNT sample substrate is silicon. The backside of the silicon substrate is thermally oxidized to create a 2μm thick and pinhole-free SiO2 layer so that the platinum heater and thermometer can survive from the server CNT growth environments and without any electrical leakage. For high heat flux cooling, the CNT bi-wick structure is composed of 250μm tall, 100μm wide stripe-like CNT clusters and 50μm empty space. Using 1×1cm2 CNT bi-wick samples, experiments are completed in both the open and saturated environments. Testing results of CNT bi-wick structure demonstrate 600W/cm2 heat transfer capacity and good thermal & mass transport characteristics in the nano level porous media.

Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes

2018 ◽  
Author(s):  
Jensen Hoke ◽  
Todd Bandhauer ◽  
Jack Kotovsky ◽  
Julie Hamilton ◽  
Paul Fontejon
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Flow Boiling ◽  
Laser Diodes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Average Maximum

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.

scholarly journals Influence of the ambient temperature on the cooling efficiency of the high performance cooling device with thermosiphon effect

2018 ◽  
Vol 180 ◽  
pp. 02073
Author(s):  
Patrik Nemec ◽  
Milan Malcho
Keyword(s):  
Ambient Temperature ◽  
High Performance ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
Measuring Method ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Cooling Efficiency ◽  
Cooling Device

This work deal with experimental measurement and calculation cooling efficiency of the cooling device working with a heat pipe technology. The referred device in the article is cooling device capable transfer high heat fluxes from electric elements to the surrounding. The work contain description, working principle and construction of cooling device. The main factor affected the dissipation of high heat flux from electronic elements through the cooling device to the surrounding is condenser construction, its capacity and option of heat removal. Experimental part describe the measuring method cooling efficiency of the cooling device depending on ambient temperature in range -20 to 40°C and at heat load of electronic components 750 W. Measured results are compared with results calculation based on physical phenomena of boiling, condensation and natural convection heat transfer.

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