Multilayer Composite Diamond Heat Spreaders for Electronic Packaging

1996 ◽  
Vol 445 ◽  
Author(s):  
K. Jagannadham ◽  
W. D. Fan ◽  
R. B. Dinwidde ◽  
J. Narayan
Keyword(s):  
Electronic Device ◽  
Single Layer ◽  
Heat Spreader ◽  
Microscopy Imaging ◽  
Diamond Composite ◽  
Heat Spreaders ◽  
Composite Diamond ◽  
Composite Substrates ◽  
Composite Heat ◽  
Heat Spreading

AbstractHeat spreader characteristics of single layer and multilayer diamond composite substrates are determined by bonding to electronic device wafers. Preparation of diamond substrates, metallization and bonding procedures to device wafers are described. Infrared microscopy imaging of the bonded device wafers is used to determine the heat spreading characteristics. Advantages associated with multilayer diamond composite heat spreaders are discussed.

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.

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.

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.

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.

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.

Challenges in Package Cooling of High Performance Servers

2007 ◽  
Author(s):  
Jie Wei
Keyword(s):  
Thermal Conductivity ◽  
Power Dissipation ◽  
High Performance ◽  
Heat Pipes ◽  
High Thermal Conductivity ◽  
Thermal Interface Material ◽  
Heat Spreader ◽  
Asymmetric Power ◽  
Heat Spreading ◽  
Silver Composite

Cooling technologies for dealing with high-density and asymmetric power dissipation are discussed, arising from thermal management of high performance server CPU-packages. In this paper, investigation and development of associated technologies are introduced from a viewpoint of industrial application, and attention is focused on heat conduction and removal at the package and heatsink module level. Based on analyses of power dissipation and package cooling characteristics, properties of a new metallic thermal interface material are presented where the Indium-Silver composite was evaluated for integrating the chip and its heat-spreader, effects of heat spreading materials on package thermal performance are investigated including high thermal conductivity diamond composites, and evaluations of enhanced heatsink cooling capability are illustrated where high thermal conductivity devices of heat pipes or vapor chambers were applied for improving heat spreading in the heatsink base.

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