Analysis and Characterization of Thermal Expansion-Matched Wick-Based Multi-Chip Passive Heat Spreaders in Static and Dynamic Environments

2013 ◽  
Author(s):  
David H. Altman ◽  
Anurag Gupta ◽  
Thomas E. Dubrowski ◽  
Darin J. Sharar ◽  
Nicholas R. Jankowski ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Thermal Performance ◽  
High Power ◽  
Coefficient Of Thermal Expansion ◽  
Inertial Force ◽  
Dynamic Environments ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Heat Spreaders

Ensuring adequate spreading of heat dissipated by high power density devices is a critical part of many electronics packaging designs. In many cases, passive wick-based heat spreaders can offer improved heat spreading performance relative to solid conductor alternatives. However, concerns related to performance degradation in high-inertial force environments frequently limit their use to static or near-static applications. In this work we investigate the performance of low coefficient of thermal expansion (CTE) wick-based heat spreaders cooling multiple high heat flux devices in static and high-g environments. Two high-power devices are simulated using custom-manufactured resistor-thermometer chips, enabling dissipation of die average heat fluxes in excess of 150W/cm2. Comparative thermal performance is evaluated for wick-based heat spreaders and solid CuMo heat spreaders of equivalent CTE affixed with interface materials typical of those used when attaching a low CTE package to a high CTE cold plate (e.g., Al or Cu). Thermal performance is characterized as a function of heat input during exposure to increasing g-forces applied using a custom-built centrifuge. Experimental observations are interpreted through detailed modeling of fluid flow patterns within the wick structure of the passive heat spreader. Results from these experiments demonstrate that properly designed wick-based heat spreaders have utility in both static and dynamic environments, exhibiting effective conductivities in excess of that obtainable with competitive low-expansion composites.

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.

Thermal Performance of Natural Graphite Heat Spreaders With Embedded Thermal Vias

2007 ◽  
Author(s):  
Martin Smalc ◽  
Prathib Skandakumaran ◽  
Julian Norley
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Performance ◽  
Numerical Models ◽  
Accelerated Aging ◽  
High Heat ◽  
High Heat Flux ◽  
Natural Graphite ◽  
Heat Spreaders ◽  
Graphite Heat

Natural graphite heat spreaders are in use in electronic cooling applications where heat flux density is low. Natural graphite is an anisotropic material, with a high thermal conductivity in the plane of the spreader combined with a much lower thermal conductivity through its thickness. This low through-thickness thermal conductivity poses a problem when attempting to cool heat sources with relatively high heat flux densities. This problem can be overcome by embedding a thermal via in the graphite material. This via is made from an isotropic material with a thermal conductivity significantly higher than the through-thickness graphite conductivity. This paper examines the thermal performance of a natural graphite heat spreader with an embedded thermal via. The work is primarily experimental although numerical models were used to guide the experiments. The thermal performance of these spreaders is compared to that of spreaders made from conventional isotropic materials. The effect of accelerated aging tests on the performance of these graphite spreaders is reviewed. Finally, two applications are examined; first cooling an ASIC module and second, cooling an FB-DIMM memory card.

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.

scholarly journals Experimental Investigation of Compact Evaporators for Ultralow Temperature Refrigeration of Microprocessors

2007 ◽  
Vol 129 (3) ◽  
pp. 291-299 ◽  
Author(s):  
Robert Wadell ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov
Keyword(s):  
High Heat ◽  
Heat Fluxes ◽  
Junction Temperature ◽  
High Heat Flux ◽  
Base Line ◽  
Vapor Compression ◽  
Pin Fin ◽  
Slit Flow ◽  
Strong Motivation ◽  
Pin Fin Array

Microprocessor performance can be significantly improved by lowering the junction temperature, especially down to the deep subambient levels. This provides the strong motivation for the current study, which focuses on the design and thermohydraulic performance evaluation of high heat flux evaporators suitable for interfacing the microprocessor chip with a cascaded R134a∕R508b vapor compression refrigeration system at −80°C. Four compact evaporator designs are examined—a base line slit-flow structure with no microfeatures, straight microchannels, an inline pin fin array, and an alternating pin fin array—all fitting the same size envelope. Pressure drop and heat transfer measurements are reported and discussed to explain the performance of the various evaporator geometries for heat fluxes ranging between 20W∕cm2 and 100W∕cm2.

Copper-Carbon Nanotube Micropillars for Passive Thermal Management of High Heat Flux Electronic Devices

2020 ◽  
Author(s):  
Gerardo Rojo ◽  
Jeff Darabi
Keyword(s):  
Thermal Management ◽  
Thermal Performance ◽  
Computational Study ◽  
Copper Substrate ◽  
Heat Removal ◽  
Cost Effective ◽  
High Heat ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Micropillar Array

Abstract Miniaturization of electronic products and a consequent rapid increase in power density of advanced microprocessors and electronic components have created a need for improved cooling techniques to efficiently remove heat from such devices. Traditional air-cooled heat sinks have been utilized for several decades as the most cost-effective cooling technique for electronic cooling applications. However, the existing thermal management solutions are unable to maintain the temperature of the next generation of complex electronic systems within acceptable limits without adding considerable weight and complexity. This paper reports a microstructured wick for application in passive thermal management systems such as heat pipes and vapor chambers. The wick structure consists of mushroom-like composite copper-carbon nanotubes (Cu-CNT) micropillars. The small spacing between micropillar heads provides a higher capillary pressure whereas the large spacing between the base of micropillars provides a higher permeability for liquid flow. The micropillar array was fabricated on a copper substrate using an electroplating technique. The micropillar array was then tested in a controlled environment to experimentally measure its thermal performance under several operating conditions. A heat removal capability of 80 W/cm2 was demonstrated at a wall superheat of 15° C. In addition, a computational study was performed using ANSYS Fluent to predict the thermal performance of the micropillar array. Model predictions were compared with the experimental results and good agreement was obtained.

Optimization of Refrigeration Systems for High-Heat-Flux Microelectronics

2008 ◽  
Author(s):  
P. E. Phelan ◽  
Y. Gupta ◽  
H. Tyagi ◽  
R. Prasher ◽  
J. Cattano ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Consumption ◽  
System Design ◽  
High Heat ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Compressor Inlet

Increasingly, military and civilian applications of electronics require extremely high heat fluxes, on the order of 1000 W/cm2. Thermal management solutions for these severe operating conditions are subject to a number of constraints, including energy consumption, controllability, and the volume or size of the package. Calculations indicate that the only possible approach to meeting this heat flux condition, while maintaining the chip temperature below 50 °C, is to utilize refrigeration. Here we report an initial optimization of the refrigeration system design. Because the outlet quality of the fluid leaving the evaporator must be held to approximately less than 20%, in order to avoid reaching critical heat flux, the refrigeration system design is dramatically different from typical configurations for household applications. In short, a simple vapor-compression cycle will require excessive energy consumption, largely because of the superheat required to return the refrigerant to its vapor state before the compressor inlet. A better design is determined to be a “two-loop” cycle, in which the vapor-compression loop is coupled thermally to a primary loop that directly cools the high-heat-flux chip.

scholarly journals Thermal Assessment of Nano-Particulate Graphene-Water/Ethylene Glycol (WEG 60:40) Nano-Suspension in a Compact Heat Exchanger

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1929 ◽  
Author(s):  
M. Sarafraz ◽  
Mohammad Safaei ◽  
Zhe Tian ◽  
Marjan Goodarzi ◽  
Enio Bandarra Filho ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Ethylene Glycol ◽  
Thermal Performance ◽  
Evaluation Criteria ◽  
High Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
High Heat Flux ◽  
Micro Channel

In the present study, we report the results of the experiments conducted on the convective heat transfer of graphene nano-platelets dispersed in water-ethylene glycol. The graphene nano-suspension was employed as a coolant inside a micro-channel and heat-transfer coefficient (HTC) and pressure drop (PD) values of the system were reported at different operating conditions. The results demonstrated that the use of graphene nano-platelets can potentially augment the thermal conductivity of the working fluid by 32.1% (at wt. % = 0.3 at 60 °C). Likewise, GNP nano-suspension promoted the Brownian motion and thermophoresis effect, such that for the tests conducted within the mass fractions of 0.1%–0.3%, the HTC of the system was improved. However, a trade-off was identified between the PD value and the HTC. By assessing the thermal performance evaluation criteria (TPEC) of the system, it was identified that the thermal performance of the system increased by 21% despite a 12.1% augmentation in the PD value. Furthermore, with an increment in the fluid flow and heat-flux applied to the micro-channel, the HTC was augmented, showing the potential of the nano-suspension to be utilized in high heat-flux thermal applications.

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