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.

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.

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 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.

Capillary Pumped Loop Heat Spreader for Electronics Cooling

2001 ◽  
Author(s):  
Jaewon Chung ◽  
Costas P. Grigoropoulos ◽  
Ralph Greif
Keyword(s):  
Electronics Cooling ◽  
Cooling Capacity ◽  
Impinging Jets ◽  
Heat Sinks ◽  
Manufacturing Cost ◽  
Air Cooling ◽  
Capillary Pumped Loop ◽  
Heat Spreader ◽  
Vertical Orientation ◽  
Thermoelectric Coolers

Abstract As cooling requirements for electronic devices, e.g. computer processor units, power modules, etc. increase beyond the capabilities of air-cooling, interest has moved to several alternatives such as thermoelectric coolers, impinging jets and heat exchangers with phase change. Included among these, the capillary pumped loop is a very competitive cooling device, because of its performance reliability, no power requirements and low manufacturing cost. In this paper, a heat spreader employing capillary pumped loop principles was made of aluminum and copper and tested. The copper CPL heat spreader with heat sinks and fans on the condenser (86mm thick, 60mm wide, 181mm long) has demonstrated a cooling capacity of 640W at atmospheric pressure in the vertical orientation and maintains a difference between TIHE (temperature of the interface between heater and evaporator) and TAMB (ambient temperature) lower than 100°C.

Ceramic-Based Planar Heat Pipe (Plate) for Passive Electronics Cooling

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000159-000165
Author(s):  
M. Wilson ◽  
H. Anderson ◽  
J. Fellows ◽  
C. Lewinsohn
Keyword(s):  
Integrated Circuits ◽  
Phase Change ◽  
Heat Dissipation ◽  
Thermal Contact ◽  
Three Dimensional ◽  
Electronics Cooling ◽  
Ceramic Materials ◽  
Back Side ◽  
Dimensional Network ◽  
Internal Networks

Heat dissipation has become a major hurdle for the electronics industry, especially as higher performance integrated circuits are being developed for the power industry. Two of the primary hurdles in dissipating this heat are:The thermal contact resistance between the IC and the cooling device.The ability to effectively spread the heat, such that traditional cooling technologies can be effective.By selecting ceramic materials that are thermo-mechanically matched (CTE) to IC materials, the proposed heat plate can be directly bonded by typical solder or braze techniques to the back-side of the IC. This eliminates thermal resistances due to contact and thermal interface materials. Within these heat plates, a three dimensional network of gas channels and fluid wicks spread the high-flux heat loads from localized hot spots to the surrounding regions via phase change fluids and mass transport. Like traditional heat pipes, these heat plates operate at nearly uniform temperature due to the phase change. The internal networks provide for multidimensional heat and mass flow, increasing their dissipating capability. By using matched ceramic materials, and the inclusion of a heat plate, these primary hurdles for heat dissipation can be mitigated. The performance of prototypical planar heat plates will be 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.

Reliability of Underfill-Encapsulated Flip-Chips With Heat Spreaders

1998 ◽  
Vol 120 (4) ◽  
pp. 322-327 ◽  
Author(s):  
H. Doi ◽  
K. Kawano ◽  
A. Yasukawa ◽  
T. Sato
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Thermal Cycling ◽  
Failure Mode ◽  
Flip Chip ◽  
Solder Joints ◽  
Alumina Substrate ◽  
Heat Spreader ◽  
Flip Chips ◽  
Heat Spreaders

The effect of a heat spreader on the life of the solder joints for underfill-encapsulated, flip-chip packages is investigated through stress analyses and thermal cycling tests. An underfill with suitable mechanical properties is found to be able to prolong the fatigue life of the solder joints even in a package with a heat spreader and an alumina substrate. The delamination of the underfill from the chip is revealed as another critical failure mode for which the shape of the underfill fillet has a large effect.

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.

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