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.

Sizing of Heat Spreaders Above Dielectric Layers

2001 ◽  
Vol 123 (3) ◽  
pp. 173-181 ◽  
Author(s):  
Calvin Chen ◽  
Marc Hodes ◽  
Lou Manzione
Keyword(s):  
Finite Element Analysis ◽  
Thermal Design ◽  
Power Device ◽  
Heat Spreader ◽  
Element Analysis ◽  
Arbitrary Length ◽  
Design Engineers ◽  
Dielectric Layers ◽  
Heat Spreaders ◽  
Length Width

A means to properly size rectangular heat spreaders between a dielectric layer connected to thermal ground and a power device is developed by modeling the problem as a thermal resistance network. Generalized formulas and nondimensional charts to optimize heat spreader thickness and footprint are presented. The power device and heat spreader are assumed to be (concentric) rectangular solids of arbitrary length, width and thickness. The nondimensional results are validated by finite element analysis (FEA) and examples demonstrate the utility of the methodology to thermal design engineers.

Synthesis of CFD Analyses and Experiments in Developing a Thermal Network Model of a Simulated Heat Spreader Panel

2008 ◽  
Author(s):  
Masaru Ishizuka ◽  
Shinji Nakagawa ◽  
Tatsuro Yoshida ◽  
Wataru Nakayama
Keyword(s):  
Network Model ◽  
Thermal Environment ◽  
Thermal Characteristics ◽  
Thermal Design ◽  
Heat Sources ◽  
Heat Spreader ◽  
Thermal Network ◽  
Wide Range ◽  
Cfd Analyses ◽  
Panel Thickness

The object of the present study is a simulated heat spreader panel (80 × 100 × 0.8 mm3) which carries five distributed heat sources and a finned heat sink near one of its corners. The panel thickness is designed to minimize temperature variation over the heat sources. The panel and the wrapping insulation possess geometric and thermal characteristics commonly found in thin electronic products. Thin configuration increases the sensitivity of internal temperature to the variation of external thermal environment; that is, a significant level of uncertainties should be expected in the thermal design of such systems. The present study aims at the development of a methodology for thermal analysis of such thin systems. Uncertainties in the thermal environment demand the coverage of a wide range of relevant parameters by the analysis, and computations can be performed most efficiently with a thermal network model. To achieve the stated goal we performed CFD simulations and the experiments, and reduced the results into a thermal network model.

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.

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.

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.

Thermal Design and Optimization of Harsh Environment Power Electronics in Natural Convection Heat Transfer

2003 ◽  
Author(s):  
Mehmet Arik ◽  
Manoj Nagulapally ◽  
Steven Brzozowski ◽  
John Glaser
Keyword(s):  
Heat Transfer ◽  
Power Electronics ◽  
Thermal Management ◽  
Heat Sink ◽  
Performance Enhancement ◽  
Cooling System ◽  
Thermal Design ◽  
Harsh Environment ◽  
Air Cooling ◽  
Heat Spreader

A study of thermal management of a harsh environment power electronics system is presented. The thermal environments were found to be between 65 °C and 90 °C that is considerably higher than many traditional electronics applications. A modular, low cost, and passive air-cooling system was desired. An analytical model was developed to obtain the heat transfer characteristics. Further performance verification of the thermal management solution was completed using a commercially available CFD tool. A small footprint area for thermal design of the power electronics connected with an electrically isolating low-conductivity material to the heat sink increased the challenge. A further thermal performance enhancement was achieved with the addition of a heat spreader between power electronics and the heat sink, and optimization of the heat spreader was achieved by utilizing FEM technique.

Thermal Spreading Analysis of Rectangular Heat Spreader

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
S. M. Thompson ◽  
H. B. Ma
Keyword(s):  
Expansion Method ◽  
Area Ratio ◽  
Maximum Temperature ◽  
Heat Spreader ◽  
Two Phase ◽  
Cosine Series ◽  
Steady State Temperature ◽  
Heat Spreaders ◽  
Unique Method ◽  
Biot Numbers

A unique nondimensional scheme that employs a source-to-substrate “area ratio” (e.g., footprint), has been utilized for analytically determining the steady-state temperature field within a centrally-heated, cuboidal heat spreader with square cross-section. A modified Laplace equation was solved using a Fourier expansion method providing for an infinite cosine series solution. This solution can be used to analyze the effects of Biot number, heat spreader thickness, and area ratio on the heat spreader's nondimensional maximum temperature and nondimensional thermal spreading resistance. The solution is accurate only for low Biot numbers (Bi < 0.001); representative of highly-conductive, two-phase heat spreaders. Based on the solution, a unique method for estimating the effective thermal conductivity of a two-phase heat spreader is also presented.

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.

Sign in / Sign up

Export Citation Format

Share Document