scholarly journals A Method for Thermal Performance Characterization of Ultrathin Vapor Chambers Cooled by Natural Convection

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Gaurav Patankar ◽  
Simone Mancin ◽  
Justin A. Weibel ◽  
Suresh V. Garimella ◽  
Mark A. MacDonald
Keyword(s):  
Natural Convection ◽  
Temperature Distribution ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Heat Dissipation ◽  
Test Facility ◽  
Vapor Chamber ◽  
Heat Spreader ◽  
Heat Spreaders

Vapor chamber technologies offer an attractive approach for passive cooling in portable electronic devices. Due to the market trends in device power consumption and thickness, vapor chamber effectiveness must be compared with alternative heat spreading materials at ultrathin form factors and low heat dissipation rates. A test facility is developed to experimentally characterize performance and analyze the behavior of ultrathin vapor chambers that must reject heat to the ambient via natural convection. The evaporator-side and ambient temperatures are measured directly; the condenser-side surface temperature distribution, which has critical ergonomics implications, is measured using an infrared (IR) camera calibrated pixel-by-pixel over the field of view and operating temperature range. The high thermal resistance imposed by natural convection in the vapor chamber heat dissipation pathway requires accurate prediction of the parasitic heat losses from the test facility using a combined experimental and numerical calibration procedure. Solid metal heat spreaders of known thermal conductivity are first tested, and the temperature distribution is reproduced using a numerical model for conduction in the heat spreader and thermal insulation by iteratively adjusting the external boundary conditions. A regression expression for the heat loss is developed as a function of measured operating conditions using the numerical model. A sample vapor chamber is tested for heat inputs below 2.5 W. Performance metrics are developed to characterize heat spreader performance in terms of the effective thermal resistance and the condenser-side temperature uniformity. The study offers a rigorous approach for testing and analysis of new vapor chamber designs, with accurate characterization of their performance relative to other heat spreaders.

scholarly journals A Method for Thermal Performance Characterization of Ultra-Thin Vapor Chambers Cooled by Natural Convection

2015 ◽  
Author(s):  
Gaurav Patankar ◽  
Simone Mancin ◽  
Justin A. Weibel ◽  
Suresh V. Garimella ◽  
Mark A. MacDonald
Keyword(s):  
Natural Convection ◽  
Temperature Distribution ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Heat Dissipation ◽  
Test Facility ◽  
Vapor Chamber ◽  
Heat Spreader ◽  
Heat Spreaders

Vapor chamber technologies offer an attractive approach for passive cooling in portable electronic devices. Due to the market trends in device power consumption and thickness, vapor chamber effectiveness must be compared with alternative heat spreading materials at ultra-thin form factors and low heat dissipation rates. A test facility is developed to experimentally characterize performance and analyze the behavior of ultra-thin vapor chambers that must reject heat to the ambient via natural convection. The evaporator-side and ambient temperatures are measured directly; the condenser-side surface temperature distribution, which has critical ergonomics implications, is measured using an infrared camera calibrated pixel-by-pixel over the field of view and operating temperature range. The high thermal resistance imposed by natural convection in the vapor chamber heat dissipation pathway requires accurate prediction of the parasitic heat losses from the test facility using a combined experimental and numerical calibration procedure. Solid Metal heat spreaders of known thermal conductivity are first tested, and the temperature distribution is reproduced using a numerical model for conduction in the heat spreader and thermal insulation by iteratively adjusting the external boundary conditions. A regression expression for the heat loss is developed as a function of measured operating conditions using the numerical model. A sample vapor chamber is tested for heat inputs below 2.5 W. Performance metrics are developed to characterize heat spreader performance in terms of the effective thermal resistance and the condenser-side temperature uniformity. The study offers a rigorous approach for testing and analysis of new vapor chamber designs, with accurate characterization of their performance relative to other heat spreaders.

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.

Integration of Silver Heat Spreaders in LTCC utilizing Thick Silver Tape in the Co-fire Process

2015 ◽  
Vol 2015 (CICMT) ◽  
pp. 000062-000066 ◽  
Author(s):  
T. Welker ◽  
S. Günschmann ◽  
N. Gutzeit ◽  
J. Müller
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Junction Temperature ◽  
Large Area ◽  
Heat Spreader ◽  
Integration Density ◽  
Heat Spreaders ◽  
Cte Mismatch ◽  
Pattern Resolution

The integration density in semiconductor devices is significantly increased in the last years. This trend is already described by Moore's law what forecasts a doubling of the integration density every two years. This evolution makes greater demands on the substrate technology which is used for the first level interconnect between the semiconductor and the device package. Higher pattern resolution is required to connect more functions on a smaller chip. Also the thermal performance of the substrate is a crucial issue. The increased integration density leads to an increased power density, what means that more heat has to dissipate on a smaller area. Thus, substrates with a high thermal conductivity (e. g. direct bonded copper (DBC)) are utilized which spread the heat over a large area. However, the reduced pattern resolution caused by thick metal layers is disadvantageous for this substrate technology. Alternatively, low temperature co-fired ceramic (LTCC) can be used. This multilayer technology provides a high pattern resolution in combination with a high integration grade. The poor thermal conductivity of LTCC (3 … 5 W*m−1*K−1) requires thermal vias made of silver paste which are placed between the power chip and the heat sink and reduce the thermal resistance of the substrate. The via-pitch and diameter is limited by the LTCC technology, what allows a maximum filling grade of approx. 20 to 25 %. Alternatively, an opening in the ceramic is created, to bond the chip directly to the heat sink. This leads to technological challenges like the CTE mismatch between the chip and the heat sink material. Expensive materials like copper molybdenum composites with matched CTE have to be used. In the presented investigation, a thick silver tape is used to form a thick silver heat spreader through the LTCC substrate. An opening is structured by laser cutting in the LTCC tape and filled with a laser cut silver tape. After lamination, the substrate is fired using a constraint sintering process. The bond strength of the silver to LTCC interface is approx. 5.6 MPa. The thermal resistance of the silver structure is measured by a thermal test chip (Delphi PST1, 2.5 mm × 2.5 mm) glued with a high thermal conducting epoxy to the silver structure. The chip contains a resistor and diodes to generate heat and to determine the junction temperature respectively. The backside of the test structure is temperature stabilized by a temperature controlled heat sink. The resulting thermal resistance is in the range of 1.1 K/W to 1.5 K/W depending on the length of silver structure (5 mm to 7 mm). Advantages of the presented heat spreader are the low thermal resistance and the good embedding capability in the co-fire LTCC process.

Si Vapor Chamber Integrated with Through Silicon Via for 3D Packaging

2013 ◽  
Vol 2013 (1) ◽  
pp. 000552-000557 ◽  
Author(s):  
Jun Taniguchi ◽  
Takeshi Shioga ◽  
Yoshihiro Mizuno
Keyword(s):  
Thermal Resistance ◽  
Heat Dissipation ◽  
Working Fluid ◽  
In Situ Observation ◽  
Vapor Chamber ◽  
Cover Glass ◽  
Through Silicon Via ◽  
Improvement Rate ◽  
Fine Pitch ◽  
3D Packaging

We demonstrate an etched silicon vapor chamber integrated with a through-silicon via (TSV) for 3D packaging. The Si vapor chamber chip enables low mismatch in the thermal expansion coefficient of a Si-LSI chip and provides a new heat dissipation path for 3D-LSI inter layer cooling. For the first prototype of the vapor chamber, an outside 33-mm × 33-mm chip consisting of a 25-mm × 25-mm area for the vapor chamber, a wick structure 30-μm high, and a vapor passage 100-μm high is developed. In-situ observation of the behavior of the working fluid through the cover glass and heat transfer enhancement is successfully demonstrated. The improvement rate of thermal resistance is 7.1% compared to a test chip without working fluid. Next, the fluid flow of a second vapor chamber prototype consisting of the first prototype integrated with a TSV structure using a Si pillar of 150-μm diameter is investigated. Thermal resistance and droplet observation conducted to evaluate the influence of the TSV. The operation of the vapor chamber is confirmed when a Si pillar is arranged to a coarse pitch of more than 500 μm. A droplet is generated and the vapor passage is partially obstructed. However, the droplet eventually degenerated and the performance of the vapor chamber is maintained. When the Si pillar is arranged to a fine pitch of 200 μm, the entire vapor passage is blocked during the liquid charging process, and no improvement is observed in the thermal resistance of the chip.

Thermal Behavior of Silicon Heat Spreader Coated With Diamond Film

2004 ◽  
Author(s):  
T. W. Lin ◽  
M. C. Wu ◽  
C. H. Peng ◽  
P. L. Chen ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Silicon Wafer ◽  
Diamond Film ◽  
Silicon Surface ◽  
Average Nusselt Number ◽  
Diamond Surface ◽  
Heat Spreader ◽  
Heat Spreaders

In the present study, an experimental setup with stringent measurement methods for performing the natural convection from a horizontal heated chip mounted with a silicon heat spreader coated with diamond film has been successfully established. The parametric studies on the local and average effective heat transfer characteristics for natural convection from a horizontal smooth silicon wafer, rough silicon wafer or silicon wafer coated with diamond film spreader have been explored. The influencing parameters and conditions include Grashof number and spreader material with different surface treatment conditions. From the results, an axisymmetric bowl-shaped Nu profile is achieved, and the highest heat transfer performance occurs at the location near the rim of the heated surfaces for various heat spreaders. The local Nusselt number for a specified convective heat flux decreases along the distance from the disk rim toward the center. The local or average Nusselt number increases with increasing Grashof number for various heat spreaders. As compared with the average Nusselt number for smooth water surface (Ra=5.69nm), the heat transfer enhancements for rough silicon surface (Ra=516.61nm) and rough diamond surface (Ra=319.51nm) are 10.42% and 7.69%, respectively. Furthermore, new correlations for local and average Nusselt numbers for various heat spreaders are presented, respectively. As compared with the smooth silicon surface, the external thermal resistance for rough silicon surface and rough diamond surface are reduced to 91.18% and 90.73%, respectively; and the maximum thermal resistances for rough silicon wafer and silicon wafer coated with diamond film are reduced to 90.43% and 92.61%, respectively.

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.

Microchannel Optimization for Heat Dissipation From a Solid Substrate

2008 ◽  
Author(s):  
C. B. Sobhan ◽  
P. S. Anoop ◽  
Kuriyan Arimboor ◽  
Thomas Abraham ◽  
G. P. Peterson
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Computational Model ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Solid Substrate ◽  
Nusselt Numbers

A computational model was developed to analyze and optimize the convective heat transfer for water flowing through rectangular microchannels fabricated in a silicon substrate. A baseline case was analyzed by solving the nondimensional governing equations. Using a quasi three-dimensional computational model, the velocity and temperature distributions were obtained and the numerical results were then used to determine the overall dimensionless thermal resistance for the convective heat transfer from the substrate to the fluid. To validate the numerical model, the average Nusselt numbers as determined by the numerical model were compared with experimental results available in the literature, for channels with comparable hydraulic diameters. The procedure for arriving at an optimum geometric configuration and arrangement of microchannels on the substrate, subject to given design constraints, so that the thermal resistance is at a minimum, is described and demonstrated using the computational model.

Flat Polymer Heat Spreader With High Aspect Ratio Micro Hybrid Wick Operating Under Adverse Gravity

2011 ◽  
Author(s):  
Christopher Oshman ◽  
Qian Li ◽  
Li-Anne Liew ◽  
Ronggui Yang ◽  
Y. C. Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Thermal Resistance ◽  
High Aspect Ratio ◽  
Circuit Board ◽  
Gravitational Acceleration ◽  
Heat Spreader ◽  
Flexible Polymer ◽  
Heat Spreaders

We report the successful fabrication and application of a micro-scale hybrid liquid wicking structure in flat polymer-based heat spreaders to improve the heat transfer performance under gravitational acceleration. The hybrid wick consists of 100 μm high, 200 μm wide square electroformed high aspect ratio copper micro-pillars with 31 μm spacing for liquid flow. A woven copper mesh with 51 μm diameter and 76 μm spacing was bonded to the top surface of the pillars to enhance evaporation and condensation heat transfer. The exterior device geometry is 40 mm × 40 mm × 1.0 mm. The 100 μm thick liquid crystal polymer (LCP) casing contains a two-dimensional array of copper filled vias to reduce the overall thermal resistance. The device was tested with heat flux input of up to 63 W/cm2 at horizontal and vertical orientations. The difference in temperature between the evaporator and condenser was measured and compared to a copper reference block of identical exterior dimensions. The experimentally determined thermal resistance of the copper block remained nearly constant at 1.2 K/W. The thermal resistance of the flat polymer heat spreader at horizontal orientation was 0.55 K/W. The same device at −90° adverse orientation resulted in a thermal resistance of 0.60 K/W. These measurements indicate that this hybrid wicking structure is capable of providing a capillary pumping pressure that is effective at transferring at least 63 W/cm2 heat flux regardless of orientation. This work illustrates an important step to developing more effective thermal management strategies for the next generation of heat generating components and the possibility of developing flexible, polymer-based heat spreaders fabricated with standardized printed circuit board technologies.

Heat Spreader Characteristics Of Multilayer Diamond Films For High Frequency Power Devices

1997 ◽  
Vol 483 ◽  
Author(s):  
B. Ramaswami ◽  
K. Jagannadham
Keyword(s):  
Diamond Films ◽  
Single Layer ◽  
Power Devices ◽  
Heat Spreader ◽  
Power Semiconductor ◽  
Power Semiconductor Devices ◽  
Heat Spreaders ◽  
Composite Heat ◽  
Frequency Power

AbstractSingle layer diamond and multilayer diamond films consisting of diamond and aluminum nitride are deposited on molybdenum and silicon nitride substrates. Silicon or GaAs device wafers and the diamond substrates are prepared by metallization and bonded using gold-tin eutectic solder. Results of characterization of the bond by thermal cycling, scanning electron microscopy of the cross-section samples and X-ray mapping of the distribution of different elements are presented. Advantages of use of multilayer diamond composite heat spreaders in power semiconductor devices are discussed.

Copper–graphite–copper sandwich: superior heat spreader with excellent heat-dissipation ability and good weldability

RSC Advances ◽  
2016 ◽  
Vol 6 (30) ◽  
pp. 25128-25136 ◽  
Author(s):  
Bin Jiang ◽  
Huatao Wang ◽  
Guangwu Wen ◽  
Enliang Wang ◽  
Xiaoqiang Fang ◽  
...  
Keyword(s):  
Potential Application ◽  
Heat Dissipation ◽  
Thermal Conductance ◽  
Electronics Cooling ◽  
Low Density ◽  
Wearable Electronics ◽  
Heat Spreader ◽  
Heat Spreaders

Cu–graphite–Cu sandwich heat spreaders with high thermal conductance and low density present outstanding ability of heat dissipation, which have potential application in smart and wearable electronics cooling.

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