Optimizing Diamond Heat Spreaders for Thermal Management of Hotspots for GaN Devices

2015 ◽  
Vol 2015 (1) ◽  
pp. 000336-000341
Author(s):  
Thomas Obeloer ◽  
Bruce Bolliger ◽  
Yong Han ◽  
Boon Long Lau ◽  
Gongyue Tang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal Management ◽  
Heat Dissipation ◽  
High Reliability ◽  
Experimental Tests ◽  
Heat Spreader ◽  
Thermal Compression ◽  
Common Solution ◽  
Heat Spreaders ◽  
Test Chips

As devices become smaller while still requiring high reliability in the presence of extreme power densities, new thermal management solutions are needed. Nowhere is this more evident than with the use of Gallium Nitride (GaN) transistors, where engineers struggle with the thermal barriers limiting the ability to achieve the intrinsic performance potential of GaN semiconductor devices. Emerging as a common solution to this GaN thermal management challenge are metallized diamond heat spreaders. In this paper, a diamond heat spreader has been applied with a hybrid Si micro-cooler for to cool GaN devices. Several different grades and thicknesses of microwave CVD diamond heat spreaders, as well as various bonding layers, are characterized for their thermal effects. The heat spreader is bonded through a TCB (thermal compression bonding) process to a Si thermal test chip designed to mimic the hotspots of 8 GaN units. The heat dissipation capabilities were compared through experimental tests and fluid-solid coupling simulations, both showing consistent results. In one configuration, using a diamond heat spreader 400μm thick with a thermal conductivity > 2000W/mK, to dissipate 70W heating power, the maximum chip temperature can be reduced by 40.4%, for test chips 100μm thick. And 10kW/cm2 hotspot heat flux can be dissipated while maintaining the maximum hotspot temperature under 160°C. The concentrated heat flux has been effectively reduced by the diamond heat spreader, and much better cooling capability of the Si micro-cooler has been achieved for high power GaN devices.

Experimental Demonstration of Thermal Management of High-Power GaN Transistors with Graphene Lateral Heat Spreaders

2011 ◽  
Vol 1344 ◽  
Author(s):  
Zhong Yan ◽  
Guanxiong Liu ◽  
Javed Khan ◽  
Jie Yu ◽  
Samia Subrina ◽  
...  
Keyword(s):  
Thermal Management ◽  
High Power ◽  
Heat Dissipation ◽  
Local Temperature ◽  
Heat Spreader ◽  
Heat Spreaders ◽  
Device Structures ◽  
Graphene Flakes ◽  
Lateral Heat

ABSTRACTGraphene is a promising candidate material for thermal management of high-power electronics owing to its high intrinsic thermal conductivity. Here we report preliminary results of the proof-of-concept demonstration of graphene lateral heat spreaders. Graphene flakes were transferred on top of GaN devices through the mechanical exfoliation method. The temperature rise in the GaN device channels was monitored in-situ using micro-Raman spectroscopy. The local temperature was measured from the shift in the Raman peak positions. By comparing Raman spectra of GaN devices with and without graphene heat spreader, we demonstrated that graphene lateral heat spreaders effectively reduced the local temperature by ~ 20oC for a given dissipated power density. Numerical simulation of heat dissipation in the considered device structures gave results consistent with the experimental data.

Fundamental Study on Thermal Characteristics of Heat Spreaders

2011 ◽  
Author(s):  
Yasushi Koito ◽  
Yusaku Nonaka ◽  
Toshio Tomimura
Keyword(s):  
Thermal Management ◽  
Theoretical Study ◽  
Thermal Characteristics ◽  
Thermal Design ◽  
Design Parameters ◽  
Heat Spreader ◽  
Fundamental Study ◽  
Discharge Characteristics ◽  
Heat Spreaders ◽  
Large Heat

A heat spreader is one of the solutions for thermal management of electronic and photonic systems. By placing the heat spreader between a small heat source and a large heat sink, the heat flux is spread from the former to the latter, resulting in a lower thermal spreading resistance between them. There are many types of heat spreaders known today having different heat transfer modes, shapes and sizes. This paper describes the theoretical study to present the fundamental data for the rational use and thermal design of heat spreaders. Two-dimensional disk-shaped mathematical model of the heat spreader is constructed, and the dimensionless numerical analysis is performed to investigate the thermal spreading characteristics of the heat spreaders. From the numerical results, the temperature distribution and the heat flow inside the heat spreaders are visualized, and then the effects of design parameters are clarified. The discussion is also made on the discharge characteristics of the heat spreaders. Moreover, a simple equation is proposed to evaluate the heat spreaders.

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.

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.

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.

Thermal Conductivity of Graphene Layers Encased in Oxide

2009 ◽  
Author(s):  
Zhen Chen ◽  
Wanyoung Jang ◽  
Wenzhong Bao ◽  
Chun Ning Lau ◽  
Chris Dames
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Electrical Resistance ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Metal Films ◽  
Heat Spreader ◽  
Graphene Layers ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Experimental knowledge of the heat flow along graphene layers encased by oxide is essential for future graphene-based nanoelectronics, interconnects, and thermal management structures. We used a “heat spreader method” to study the heat dissipation performance of encased graphene. Fitting the experimental data with a three-dimensional finite-element method (FEM) allows the in-plane thermal conductivity of the graphene layers to be extracted. The method is validated on samples with metal films of known thermal conductivity, as determined from electrical resistance measurements and the Wiedemann-Franz law.

Effects of Thin Film Heat Spreader on Hot Spots Mitigation in Heat Sinks

2021 ◽  
pp. 1-17
Author(s):  
Sohail Reddy ◽  
George S. Dulikravich ◽  
Ann-Kayana Blanchard
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Integrated Circuit ◽  
Conjugate Heat Transfer ◽  
Hot Spot ◽  
Heat Transfer Analysis ◽  
Temperature Uniformity ◽  
Heat Spreader ◽  
Heat Spreaders

Abstract The effects of graphene platelets and diamond based thin film heat spreaders on maximum temperature of integrated electronic circuits were investigated. A fully three-dimensional conjugate heat transfer analysis was performed to investigate the effects of thin film material and thickness on the temperature of a hot spot and temperature uniformity on the heated surface of the integrated circuit when subjected to forced convective cooling. Two different materials, diamond and graphene were simulated as materials for thin films. The thin film heat spreaders were applied to the top wall of an array of micro pin-fins having circular cross sections. The integrated circuit with a 4 × 3 mm footprint featured a 0.5 × 0.5 mm hot spot located on the top wall which was also exposed to a uniform background heat flux of 500 W cm−1. A hot spot uniform heat flux of magnitude 2000 W cm−2 was centrally situated on the top surface over a small area of 0.5 × 0.5 mm. Both isotropic and anisotropic properties of the thin film heat spreaders made of graphene platelets and diamond were computationally analyzed. The conjugate heat transfer analysis incorporated thermal contact resistance between the thin film and the silicon substrate. The isotropic thin film heat spreaders significantly reduced the hot spot temperature and increased temperature uniformity, allowing for increased thermal loads. Furthermore, it was found that thickness of the thin film heat spreader need not be greater than a few tens of microns

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.

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.

Thermal Performance of Natural Graphite Heat Spreaders

2005 ◽  
Author(s):  
Martin Smalc ◽  
Gary Shives ◽  
Gary Chen ◽  
Shrishail Guggari ◽  
Julian Norley ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Numerical Models ◽  
Laptop Computer ◽  
Natural Graphite ◽  
Heat Spreader ◽  
Graphite Sheet ◽  
Cooling Fan ◽  
Heat Spreaders ◽  
Graphite Heat

Heat spreaders can be made from natural graphite sheet materials. These spreaders take advantage of the anisotropic thermal properties of natural graphite. Natural graphite exhibits a high thermal conductivity in the plane of the sheet combined with a much lower thermal conductivity through the thickness of the sheet. As a result, a natural graphite sheet can function as both a heat spreader and an insulator and can be used to eliminate localized hot spots in electronic components. In some cases, a natural graphite heat spreader can replace a conventional thermal management system consisting of a heat sink and cooling fan. This paper examines the properties of natural graphite heat spreaders and the application of these spreaders to thermal management problems in laptop computers. The thermal and mechanical properties of natural graphite heat spreaders are presented along with a discussion of how those properties are measured. The use of a natural graphite heat spreader to reduce the touch temperature in a laptop computer is presented. Both experimental techniques and numerical models are used to examine performance of the heat spreader in this application.

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