March 2011
Ultrafast Submicron
Thermoreflectance
Imaging
Thermal Challenges
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Thermal Materials
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Thermal Substrates
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Fans and Blowers
Contents
Editorial
2
Archival Value
Jim Wilson, Editor-in-chief
Thermal Facts and Fairy Tales
4
Published Thermal Conductivities Values: Facts or Fairy Tales?
Clemens J.M. Lasance, Associate Technical Editor
Page 12
Calculation Corner
6
Thermal Interactions Between High-power Packages and
Heat Sinks, Part 2
Bruce Guenin, Associate Technical Editor
Feature Articles
Ultrafast Submicron Thermoreflectance Imaging
10
K. Yazawa and A. Shakouri
Thermal Challenges In Today’s Commercial and Military Aviation
16
Peter deBock and Bill Gerstler
Reasons To Use Two-Phase Refrigerant Cooling
22
Page 18
Jackson Marcinichen, Jonathan Olivier and John R. Thome
Index of Advertisers
32
2011 ElectronicsCooling Buyers’ Guide
Products & Services Index������������������������������� 28
Company Directory������������������������������������������ 30
Page 24
electronics-cooling.com
ElectronicsCooling
1
Editorial
Jim Wilson
Editor-in-Chief, March 2011 Issue
Archival Value
S
hortly after beginning to work in the electronics cooling field (1985), I heard
about visions of a paperless engineering environment. The benefits were
obvious, especially when faced with what to do with desktop-sized plots and
drawings. For the most part, the vision has been realized. We store information
electronically and routinely collaborate across geographic boundaries in real time
as long as there is access to a common database. This engineering environment
has many benefits for thermal engineers. Assuming common software, we can
quickly send models to colleagues for assistance and review. We also can store
substantially more information and details, especially when compared to folded
paper drawings.
In spite of the ease of data storage, I frequently encounter thermal analyses
and test documents that do not consist of much more than a set of presentation
slides. A recent example was revisiting products that were designed and analyzed
a few years ago. This product had gone through the typical design review process
where thermal analysis presentations were tailored for peer reviews and then for
customer reviews. Each tailoring removed more detail, and even though the reviews
were judged complete, the summary type information in a presentation leaves
out many details. In this particular example, it was possible to find the thermal
model simulation files which revealed what was analyzed, but the background
information of how the boundary conditions, heat loads, and material properties
were obtained was lost. While there are many reasons why only a presentation
document is generated, a common reason is that once the reviews are completed
the project did not want to spend any more money generating reports.
We all are exposed to the pressure of reducing the time to perform thermal
analyses and testing and may even generate metrics to show that we are faster now
than in the past. The thermal analyst often works in a consultant type role where
his time is bought by the pound (or Kg to stay consistent with our SI unit policy).
There is a short term cost saving to stopping the effort as soon as the customers
and managers are satisfied that the thermal analysis is sufficient. However, the costs
saved by not documenting can easily be overwhelmed by the costs of recreating
the information if more effort is needed in the future.
Part of the problem with presentation documents when viewed from an archival perspective is that the person generating them often needed to satisfy several
constraints. There was probably a page count or time limit, and back-up material
never receives the same amount of attention as the main body. There is also a
marketing type pressure to show how this thermal design is similar to other products that have worked and this leads to an emphasis on past success rather than a
more thorough engineering review. Adding color isotherm plots from a simulation
can make the presentation look appealing but often do not do much more than
show that a simulation model exists. An additional point is that adding details to
a presentation can make them look cluttered. To compensate, these details are
communicated orally and at best are only available in notes and memories.
I encourage all of our readers to examine their analysis presentations to improve
them from an archival perspective, and make an extra effort to create separate
thermal analysis and test reports. While the desire to be finished can be significant near the end of an effort, improved documentation and the associated cost
avoidance offsets spending the additional time.
“Those who cannot remember the past are condemned to repeat it.” (George Santayana)
2
ElectronicsCooling
www.electronics-cooling.com
Editorial Board
Associate Technical Editors
Bruce Guenin, Ph.D.
Principal Hardware Engineer
Oracle
bruce.guenin@oracle.com
Clemens Lasance, IR
Principal Scientist - Retired
Consultant at SomelikeitCool
lasance@onsnet.nu
Robert Simons
Senior Technical Staff Member - ­Retired
IBM
resimons@att.net
Jim Wilson, Ph.D., P.E.
Engineering Fellow
Raytheon Company
jsw@raytheon.com
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thermal facts and fairy tales
Published Thermal Conductivities Values:
Facts or Fairy Tales?
Clemens J.M. Lasance
Associate Technical Editor
A
round 1980, when I joined the Heat Transfer Group at
Philips CFT, my boss threw a piece of material on my
desk and asked for its thermal conductivity. It took me
a week digging in literature to discover that this was no easy
question to answer, despite the simple mathematics behind
a steady state measurement: k=q/∆T/A, with k the thermal
conductivity, q the dissipation, ∆T the temperature difference
across the test sample, and A the area. All items at the right
hand side are easy to measure, so it seemed.
This is the bottom line: to get high accuracy (let’s say better than 5%) you need very expensive equipment (between
$200,000 and $500,000). But be aware, even after buying such a
tester, there is no guarantee that in practice the value obtained
is the value you are looking for, because many materials of
interest are anisotropic.
Why is the measurement of thermal conductivity so difficult: orders of magnitude when compared to measuring
electrical conductivity, for example? Because the simple
equation is only valid for 1D heat conduction, the problem
being that it is extremely difficult to realize 1D conduction
in practice. Especially when you have small samples, and
even more when you are dealing with higher temperatures
due to increasing radiation losses. This is one of the reasons
why transient tests became popular, despite their much more
difficult mathematics. Simply because these tests measure locally, not globally. However, when talking accuracy, we face the
problem of interpretation. Are the physics the same for steady
state and transient data, you may wonder? At a conference in
Manchester on thermal conductivity in 1986, I encountered,
to my surprise, almost a real fight between believers in steady
state and transient regarding the acceptation of laser diffusivity tests as a standard test method, the argument being the
physics, especially for materials that are to a certain degree
transparent for radiation in a certain wavelength band.
Another problem hampering high accuracy is the lack
of reference materials accepted by NIST (National Institute
of Science and Technology) in the range that is of interest
to electronics cooling. Except for some building materials,
“official’’ materials are Armco iron and graphite, unofficial
the ceramic Pyroceram 9606. Why so few, you may ask? It is
not an easy task, and very expensive too, to select a reference
material. The material should be stored for hundreds of years,
and should stay homogeneous during this period, in time and
in space. Fortunately, other standard labs have more reference
materials in stock, such as NPL (National Physical Laboratory)
in England and JRC (Joint Research Centre) in Belgium [1].
The consequence of the foregoing is that, while the measurement accuracy by individual researchers is claimed to be of the
order of 2%, laboratories participating in round-robin tests pro-
4
ElectronicsCooling
duce results differing from each other by 15% or more [2]. Even the
measurement of pure metals is no exception to this rule. About
50 years ago, the published values of e.g. nickel and tungsten
varied over an order of magnitude, and the rumor goes that a
wrong value for tungsten used in the calculation of the proper
thickness for the thermal shield of early space vehicles led to
fatal problems during re-entry. The large discrepancies found
in “early” literature could possibly be attributed to small impurity levels, for which the thermal conductivity is very sensitive.
On top of this, some frequently used materials exhibit a
large temperature dependence, such as silicon. For example,
using the value for Si at room temperature while calculating
the thermal behavior of a package at operational temperature
can easily result in an error of 20%.
Taking into account the above, one may indeed start to
wonder what the accuracy of the vendor-published data is for
engineering materials: plastics, ceramics, composites. These
materials often exhibit anisotropy (e.g. FR4 shows a factor of
3 difference between in-plane and out-of-plane), and most
standard tests only measure in one direction. In other words,
because 3D conduction heat transfer dominates in practice,
even a very accurate value obtained from a standard lab does
not guarantee accuracy in a practical application. A special
category is formed by thermal interface materials. While 1D
heat conduction always predominates, the contact resistances
play an important role, and hence the pressure under which the
tests are performed. Especially for high-performance materials, quoting the thermal conductivity gives a false impression
of their behavior in practice [3].
In conclusion, when accurate predictions of temperature
are the objective of the analysis, it is recommended to perform
measurements in situ, by imposing a variety of well-known
(hard) boundary conditions (hence refrain from natural or
forced convection!) to the object under study, and fitting the
unknowns of the object (usually the thermal interface material
and the thermal conductivity) to match the measured temperatures. If this is not possible, the best guess can be obtained
by consulting the Tech Data columns in this magazine from
1997 to 2009, see for a summary reference [4].
References
[1] http://www.evitherm.org/default.asp?ID=969
[2] Hulstrom L., Tye R., Smith S., “Round robin testing of thermal conductivity
reference materials,” Thermal Conductivity, Vol. 19, Plenum Press, 1988,
pp. 199-211.
[3] Lasance, C., Murray, C., Saums, D., Rencz, M., “Challenges in Thermal
Interface Material Testing,” Proceedings of SEMI-THERM 22 Conference,
Dallas, Texas, March 15-17, 2006.
[4] Wilson J., Technical Data Summary, ElectronicsCooling, August 2009.
l
March 2011
calculation corner
Thermal Interactions Between High-Power
Packages and Heat Sinks, Part 2
Bruce Guenin
Associate Technical Editor
T
hese days, many thermal engineers face the challenge
of defining effective heat sink cooling solutions for high
power processors and ASICs (Application-Specific Integrated Circuits). The usual practice would be to calculate
a value of JA (junction-to-air thermal resistance) for the
combined package/heat sink assembly and compare it to the
requirements of the application.
Traditionally, in performing this sort of calculation, one
would first obtain a value of JC (junction-to-case thermal
resistance) from the packaging supplier and a value of SA
(sink-to-air thermal resistance) from the heat sink supplier.
Since the heat sink test is usually performed with a uniform
heat flux applied over the entire base, one would need to correct the value of SA, assuming that the heat is transferred into
the heat sink uniformly over the entire contact area between
the package and the heat sink. A very accurate and efficient
method of doing this has been described in this publication
[1]. One would then make assumptions about the thickness
and thermal conductivity of prospective thermal interface
materials (TIMs) to provide effective thermal contact between
the package and the heat sink. The thermal resistance of this
particular TIM, between the package case and the heat sink
base (namely, TIM2) is referred to as CS.
The three thermal resistance values would then be added up
to obtain the desired value of JA per the following expression:
JA = JC + CS + SA (1)
This procedure worked well enough when power levels were
lower than today. The accompanying higher values of thermal
resistance masked the presence of certain thermal interactions
that are important sources of error for high power/low thermal
resistance components. The fact that these resistances are not
boundary-condition independent means that their precise
Figure 1. Diagram of high-power package attached to a heat sink. Components in
bold color are explicitly represented in the model. Those in a faint color are part
of the physical assembly, but are not represented in the model.
6
ElectronicsCooling
value depends upon the details of the heat transfer between
the various components [2]. This is due to the fact that these
thermal resistance metrics are the product of a methodology
which ultimately represents a measurement approach: namely
the temperatures TJ, TC, TS, all are determined at the geometric
center of each component [3]. Such single-point temperature
measurements do not provide direct information regarding
the heat flux distribution that could be useful in defining a
more robust thermal resistance metric.
Summary of Part 1
Part 1 of this article was devoted to exploring the nuances of
the interactions between these components, particularly as to
their effect on the heat flux distribution in the path between
the package case and the heat sink base [4].
Figure 1 depicts a typical configuration of a flip-chip cavity
package containing a copper lid in contact with the base of a
heat sink. Those components depicted using bold colors are
explicitly represented in the Finite Element Analysis (FEA)
model. These constitute the primary heat flow path, from
the chip to the heat sink. Those drawn with the faint colors
are present in the physical assembly, but are not explicitly
represented in the model. These include the heat sink fins and
the package substrate and the printed circuit board (PCB) to
which the package is electrically interconnected. The cooling effect of the fins is accounted for by the use of an effective
heat transfer coefficient (h EFF) applied to the top of the heat
sink base. The heat flow through the package substrate to the
PCB is simply ignored, since in a high-power package, it is of
secondary importance.
Table I defines the package construction and the variations in the heat sink design explored. The heat sink designs
and the large spread in h EFF represent a wide range of thermal
performance.
The curved data sets in Figure 2 demonstrate the heat flux
distribution through the TIM2 material determined for the
lowest and highest conductivity heat sinks, at a value of heat
sink width, wHS = 70 mm, and over the full range of h EFF. They
show that, even for a package with a 1 mm thick lid made of
pure copper, the heat flux is concentrated in the center of
the package, in stark contrast to the traditional assumption
of uniform heat flow over the package area.
The rectilinear data sets represent a uniform flux distributed over a specified area defined herein as the Heat Transfer
Area (HTA). The HTA was defined in Part 1 as: the area
bounding a uniform flux region which produces the same
value of SA as the FEA simulation with non-uniform flux
distribution, each with the same total power. This procedure
March 2011
Table 1
Table 1.
was decided upon because of its simplicity, rather than pursuing the more involved process of analyzing the actual flux
distributions. For a square shaped die and package, such as
in the current example, it is convenient to refer to the HTA
Width, which provides a more intuitive sense of the size of
the area than referring to the area itself.
Derivation and Use of the HTA Concept
Figure 3 shows curves of SA versus the full range of values
of HTA Width possible with the present package: from the
die width (13 mm) to the full package width (40 mm). These
curves were calculated using FEA with only the heat sink base
in the solid model and applying the flux at HTA values equal
to 13, 20, 30, and 40 mm sq. (Note that this calculation could
have been performed with equal accuracy using the method
in Ref 1.) The curves were created using a 3rd-order linear
regression technique.
The symbol overlapping each curved line represents a value
of HTA which yields a value of SA equal to that calculated in
the full FEA model of the package in contact with the heat sink.
A spreadsheet solver was used in the calculation. For the low
conductivity heat sink they are clustered in the range of HTA
Widths between 20 and 24 mm. For the high conductivity heat
sink they are in the narrower range between 17 and 18 mm.
It is reasonable to expect that the HTA concept should be
useful in the calculation of CS, as suggested by a comparison
of the uniform flux distribution over the HTA and the actual
flux distribution in Figure 2. Since the flux is assumed to be
uniform within the HTA, the following expression, representing 1-dimensional heat flow, can be used to calculate CS
(2)
magnitude (0.002 ˚C/W) than the values of JC calculated for
the package in contact with the copper heat sink, due to its
greater thickness (6 mm vs. 2 mm). JC values calculated for
the lowest conductivity heat sink are about 0.01 ˚C/W less than
the simulated test value. Comparing these differences with the
values of SA and CS in Figure 3 suggest that these deviations
in JC in the full model from the simulated test value will not
be a significant source of error.
Figure 5 contains a plot of CS versus HTA Width. The
values of CS were calculated using one of two methods: 1)
extraction from the full package/heat sink FEA simulation
and 2) calculation using Eqn. 2 and the values of HTA calculated using the method illustrated in Figure 3. The HTAcalculated values are approximately 0.08 ˚C/W less than the
FEA-calculated values for the low conductivity heat sinks and
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where tTIM2 and kTIM2 are the thickness and thermal conductivity of TIM2, respectively. CS is plotted as a function
of HTA in Figures 3a and 3b. It is useful to compare the magnitude of CS and SA for the two heat sinks studied. For the
low conductivity heat sink, CS is much lower than the lowest
value of SA. In the case of the high conductivity heat sink, CS
is comparable in magnitude to the lowest values of SA. This
fact will be relevant during the error analysis.
Figure 4 shows the calculated values of JC, plotted versus the heat sink thermal conductivity, k HS, for all the cases
studied. It also displays a value of JC, calculated under simulated JEDEC-standard conditions (water-cooled cold plate,
2 mm-thick copper top plate) [5]. Note this is a bit lower in
electronics-cooling.com
ElectronicsCooling
7
calculation corner
Fig. 3
b)
a)
Figure 3. Plot of SA versus HTA Width at
specific values of kHS, wHS, and hEFF. Symbols
represent FEA result for SA at intersection
with SA curves, used to determine value of
HTA for each heat sink condition. Lowest
curve is CS vs HTA. a) low conductivity Al heat
sink; b) Cu heat sink.
Fig. 4
Simplified Theta,JA Calculations Using the
HTA Concept
x
Fig. 5
Figure 4. Plot of JC versus vs kHS at specific values of wHS and hEFF: extracted from
full package/heat sink FEA simulation. Black X symbol represents simulated
JEDEC test result.
It is hoped that the preceding analysis has made it clear that
the assumed size of the area bounding the heat flow between
the package and the heat sink has a significant influence on
the resultant values of CS and SA and, consequently, JA.
This section will explore the accuracy of analytic calculations making various assumptions regarding the size of this
bounding area.
Table 2 describes four methods, which differ in this assumption.
• Method #1 assumes the bounding area = the package area.
• Method #2 assumes the bounding area = a single value
of HTA averaged over all the cases studies.
• Method #3 assumes the bounding area = average of HTA calculated for each of 3 heat sink configurations.
• Method #4 assumes the bounding area = the specific value
of HTA calculated individually for each case.
JA is calculated using Eqn. 3:
JA= JC,TEST + CS(Area) [Eqn. 2] + SA(Area) [Ref. 1] (3)
Figure 5. Plot of CS versus HTA. Blue symbols: values extracted from full
package/heat sink FEA simulation. Red symbols: values calculated from Eqn. 2.
0.05 ˚C/W less for the high conductivity heat sinks. Comparing
these discrepancies with the values of SA in Figure 3, suggest
that this will be a more significant source of error.
8
ElectronicsCooling
The results calculated using each method were compared
to the JA values calculated using the original FEA model. A
complete listing of all the JA results is provided in Table 2
of Part 1 of this article [4]. The results are shown in Figure 6. The error is summarized in Table 2.
All the methods show an increase in the absolute error as
the value of JA gets smaller. Method #1, using the package
size for the heat transfer area, has an error of less than 10% for
values of JA of 3 ˚C/W and greater. For JA values of less than
this, the error grows to 36%. Using the average HTA value of 20.6 mm, in Method #2 leads to a large reduction of error,
with the maximum error equal to 16%. Further improvement
is obtained with Method #3, using the value of HTA averaged
for each heat sink design. Here the maximum error is 10%. Method #4, with a separate value of HTA applied to each
case represented a small improvement with the maximum
error equal to 9%. As indicated earlier, most of the error in
Methods #4 and 5 is due to the CS term.
March 2011
Table 2.
Conclusions
The past practice of assuming a uniform heat flow between
a package and heat sink over the full area of the package is
shown to be inadequate with high-power packages. The HTA
method uses the same assumption of a uniform flux as before,
but uses a value for the bounding area determined from a
detailed finite element analysis of the package and heat sink.
For this method to become more widely useful, correlations
are needed to generate appropriate HTA values for arbitrary
package and heat sink designs. Once the appropriate HTA is on
hand, then the remainder of the calculation is straightforward.
Note: The method described is only valid for the situation discussed: a single source with its individual heat sink,
and cannot be applied to other situations involving multiple
sources on one PCB, heat sink or cold plate.
The reader should be reminded that this sort of analysis
can be very useful in the early design phase of a project. It has
value in generating a preliminary performance specification
for a heat sink and TIM2 to accompany the high-power chip
and package of interest. Of course, in the final design phase,
additional details such as the actual chip power map, the
influence of other heat sources and the heat transfer through
the package substrate must be accounted for in a detailed
numerical model of the package, heat sink, and the system.
Fig. 6
References
[1]. Lee, S., “Calculating Spreading Resistance in Heat Sinks,” ElectronicsCooling,
Vol. 4., No. 1, January 1998.
[2]. Lasance, C., “Heat Spreading: Not a Trivial Problem,” ElectronicsCooling,
Vol. 14, No. 2, May, 2008.
[3]. JEDEC Standard, JESD-12, “Guidelines for Reporting and Using
Electronic Package Thermal Information.” Available for free download at
www.jedec.com.
[4]. Guenin, B., “Thermal interactions Between High-Power Packages and Heat
Sinks, Part 1, ElectronicsCooling, Vol. 16, No. 4, Winter, 2010.
[5]. JEDEC Standard, JESD-14, “Transient Dual Interface Test Method
for the Measurement of the Thermal Resistance Junction to Case of
Semiconductor Devices with Heat Flow Through a Single Path.” Available
for free download at www.jedec.com.
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Figure 6. Error in value of ΘJA, calculated using Eqn. 3 versus ΘJA, extracted from
full package/heat sink FEA simulation. Results reflect effect of four different
assumptions regarding the method of calculating the heat transfer area.
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1/20/11 4:00 PM
Ultrafast Submicron
Thermoreflectance Imaging
K. Yazawa and A. Shakouri
Baskin School of Engineering, University of California at Santa Cruz, California
Kazuaki Yazawa is a Project Scientist holding a Ph.D.
degree from Toyama Prefectural University, Japan. While
working for 29 years at Sony Corporation, his experience
included engineering and researching various electronic
products and taking corporate thermal engineering
leadership as a Thermal Architect and Distinguished
Engineer. He also conducted visiting research at the
University of Minnesota for waste heat energy recovery
in notebook computers from 1999-2001. Yazawa is
actively promoting collaboration between academia
and industry across the United States, Japan and
Europe. Currently, his research interest focuses on the
effective use of phonon transport in electronic devices.
He envisions that emerging nanomaterials can enhance
microdevice performance, and system thermal design
can be optimized using spatial and temporal thermal
characteristics of the devices.
Ali Shakouri is a Professor of Electrical Engineering
at University of California Santa Cruz. He received
his Ph.D. from the California Institute of Technology
in 1995. His current research is on nanoscale heat
and current transport in semiconductor devices, high
resolution thermal imaging, micro refrigerators on a
chip, and waste heat recovery. He is also working on
a new sustainability curriculum in collaboration with
colleagues in engineering and social sciences. He has
initiated an international summer school on renewable
energy sources in practice. He is the director of the
Thermionic Energy Conversion center, a multi-university
collaboration aiming to improve direct thermal to
electric energy conversion technologies. He received the
Packard Fellowship in Science and Engineering in 1999,
the NSF Career award in 2000, and the UCSC School of
Engineering FIRST Professor Award in 2004.
10
ElectronicsCooling
B
oth the miniaturization of electronic and optoelectronic devices and circuits and the increased
operation speeds of electronic devices have exacerbated localized heating problems. Steady-state and transient
characterization of temperature distribution in devices and
interconnects are important for performance and reliability
analysis. In this paper we review recent developments in
ultrafast submicron thermoreflectance imaging techniques.
Many properties of materials depend on temperature and
they can be exploited for local temperature measurement.
Good references explaining different thermal measurement
techniques, specifically thermoreflectance imaging, include
the early stage review by Cutolo [1], the study on dynamic
characterization by Altet [2], work on device circuit focus by
Christofferson [3], a simulation combined method by Raad
[4], and a review by Farzaneh [5]. Thermoreflectance imaging
technique is outlined in the next section followed by examples.
For the characterization of active devices, thermal maps
can provide useful information about the power dissipation
profile, hot spots, and manufacturing or material defects before the device completely fails. Transient thermal imaging
can show temperature variation in switching devices under
pulsed operation. This can be used to identify buried defects
or help to extract the thermal resistance/capacitance network
in the device, surrounding regions in the substrate and the
package. For optoelectronic devices, an additional scheme is
required to separate electro-luminescence and the reflected
illumination used for thermoreflectance. To demonstrate
this, we will show thermal images of solar cells and LEDs. The
CMOS transistor circuits require high spatial resolution. At
the same time, the structure of multiple metal layer interconnects makes for difficult characterization of the active device
junction temperature. With the through silicon substrate
thermal imaging, we directly measure the active transistor
region. The spatial resolution is important to characterize very
small features such as 500 nanometer diameter copper vias
in interconnects. Using electrical resistance measurements
alone isn’t enough to identify potentially critical locations that
can lead to device failure. The latter typically shows the total
series resistance. Electron beam techniques can detect local
open circuits once the interconnect fails completely. However,
the thermal map can show all of the weak connections and
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Figure 1. Merged thermal and optical images of heating in a 550nm via test
structure. Images on the right are at 23ns and 83ns delay. The excitation pulse is
50ns. The left plot shows a transient temperature rise in a small region (25pixels)
around the hot spot for two different vias.
hot spots. Thermal maps have been studied in the submicron
scale [6]. More importantly, submicron features respond very
quickly due to extremely small thermal mass, thus very fast
thermal imaging with short pulses and very low duty cycles
can be used to identify the current distribution profile before
self-heating and temperature-dependent material properties
modify the current path.
Thermoreflectance Imaging
The challenge in obtaining high quality thermal images arises
when one considers the magnitude of the weak temperaturedependent reflection coefficient (thermoreflectance effect)
in metals and semiconductors. The thermoreflectance coefficient is on the order of 10 -4 -10 -5 per degree Kelvin for most
materials [7]. This coefficient is wavelength, material, and
even surface texture dependent [8], and in-situ calibration
(e.g. with a thermocouple) is necessary. To capture the thermoreflectance signal with reasonable signal-to-noise ratio,
an active device is thermally cycled at a known frequency
Figure 2. Images of poly-Si. 2a) Optical image of a defect, 2b) Optical image with
EL combined to show the location of the EL on the defect, 2c) EL signal in reverse
bias, and 2d) Thermal image of defect at 30V reverse bias.
and lock-in technique (phase sensitive detection) is used.
Images are detected by either a p-intrinsic-n junction (PIN)
diode array camera [9] or a CCD. The PIN array has a higher
dynamic range and thermal resolution (~0.006K), while the
CCD yields superior spatial resolution and is better suited
for low intensity illumination. Thermal resolution for CCD
based thermoreflectance systems is generally assumed to be
limited by the quantization threshold of the camera. Under
ideal circumstances a 12-bit CCD would be able to measure
temperature induced reflectivity changes with an accuracy
equivalent to its quantization limit of ΔR/R=1/212 =2.44x10 -4,
which determines the temperature resolution. However, stochastic resonance processing [8] allows for the recovery of
signals well below the quantization limit. Using this method
of averaging, the discrete limit for the same 12-bit system can
be extended to ΔR/R=2.5x10 -6, with a corresponding expansion in dynamic range from 72dB to 114dB.
Here we show some results with CCD thermoreflectance
which have achieved ultra-high spatial, temporal and temperature resolutions in full field imaging. The results presented
show temperature distribution in high power transistors
and identify defects as small as 200-300nm in size. The high
temperature sensitivity, down to 10mK, for steady-state
measurements provides the opportunity to study the spatial
distribution of current flow (Joule heating) in the device and
identify defects before significant hot spots develop. Finally,
the ultrafast time resolution, down to 800 picoseconds, is important in high speed devices or in studying transient effects
such as Electrostatic Discharge (ESD) [10].
Ultra high spatial and temporal resolution
Figure 3. LED thermal images. 3a) Optical, electroluminescence and thermal
images, and 3b) Temperature response at dashes square region.
12
ElectronicsCooling
In order to test sub-nanosecond thermal imaging capability
at small scales, a sample of test vias was used. Small vias can
heat rapidly, and one can observe the heat diffusing into the
metal. To detect the small change in reflection in very short
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Figure 4. Thermal imaging of CMOS power transistor array. 4a) Device
configuration, and 4b) Topside and backside thermal images.
times, active devices are thermally cycled and characterized
with pulsed illumination and a boxcar averaging circuit. Thermal images are obtained for single vias which are 350nm and
550nm in diameter. The 550nm via is heated by pulsing currents up to 600mA at 50ns. While this is a high current density
(~2x108 A/cm2), the low duty cycle reduces the total power dissipation. Figure 1 shows the thermal images of a 550nm single
via at 23ns and 83ns delay. During turn-on the temperature
field is very localized near the via, however after turn-off the
heat begins to diffuse into the metal. By using a small region,
25 pixels, in the thermal image one can step through the image series and determine the average temperature on top of
the metal where the via is buried. The graph in Figure 1 shows
the temperature for two different via sizes for the first 200ns,
with a 50ns excitation pulse. The peak temperature is actually
higher than the average presented. The red curve from the
550nm via was acquired at only 10sec per frame averaging,
so that the entire curve was acquired in less than an hour.
The blue curve from the 350nm via was acquired with 30sec
averaging per frame, about 3 hours total. The advantage of
the extra averaging is seen in the tail of the curves, where the
blue trace shows less noise. The temperature sensitivity can
be estimated at about 1°C, for a 30sec average.
Simultaneous thermal and electroluminescence imaging of solar cells
In order to identify and characterize various defects in thinfilm amorphous-Si and copper indium gallium selenide (CIGS)
solar cells, the device can be applied forward bias or applied
reverse bias and thermal imaging can be performed. Typically
lock-in infrared thermometry is used, which has micro Kelvin
temperature resolution but the spatial resolution is limited
to a few microns and one cannot detect visible light emission with the same long wavelength cameras. In the case of
thermoreflectance it is possible to do simultaneous imaging
of the visible electro-luminescence (EL) and the temperature
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distribution [11]. In this setup, we used a megapixel siliconbased CCD. EL can be indicative of pre-breakdown sites due to
trap-assisted tunneling and stress-induced leakage currents.
Many defects can be found through electroluminescence
due to direct recombination. In solar cells, these EL defects
are typically sites of avalanche breakdown and emit white
light that can be detected by a silicon CCD. Figure 2 shows an
avalanche defect with visible EL. Since the response time of the
heat diffusion is very different from the electroluminescence
response, we are able to separate the two effects using the same
transient thermoreflectance imaging camera.
LED imaging
Non-uniformity of light emission within the active area of
an LED device can be detected by an image sensor. Since
LED devices are very sensitive to temperature thermal characterization of the active device provides useful information
under both the steady-state and transient operations. Also, the
details of temperature distribution are important to identify
potential defects. Separation of the light emission from the
device and the thermoreflectance signal is performed using
a transient differencing algorithm and a precisely controlled
phase delay [12]. Figure 3 shows the transient response to
a step pulse drive current. The quick response of the metal
surface is shown on the rising edge of the thermal transient
(green arrow) within 25s. The slower thermal transient of
the package is shown by the red arrows.
CMOS Power transistor array
Performance and reliability in high current power transistors
are strongly related to the peak temperature in the device.
Device failure is linked to thermal rather than electrical effects. For power transistors with large areas or arrayed layouts,
non-uniform current distribution throughout the device is
common. Higher current density regions experience more
self heating. If a local junction temperature exceeds critical
levels anywhere in the power device, the structure as a whole
may suffer parasitic electrical effects (e.g. gate leakage and
snapback) or sustain irreversible damage (thermal runaway).
A study on thermal profile in the depth of the device combined with software simulation has been reported by Raad
[13]. Here we present rather direct thermal characterization
of a large area of arrayed lateral diffused channels of the
power MOSFETs with three layers of metallization [14]. The
structure of the tested device is illustrated in Figure 4. The
temperature of the top metal layer is measured with blue
light illumination and the through-silicon thermal image is
obtained using InGaAs camera with 1.5microns wavelength
illumination. Thermal images from the topside and back side
are very different. The topside image shows the temperature
profile dominated by both the heat in the interconnect layer
and the heat at the probes sending the current. The backside
image shows the temperature profile in the transistor array.
The non-uniformity and larger heating near the source contact
can be detected.
Copper interconnect vias for reliability
Thermal expansion mismatch among the different materials
comprising integrated circuit chips results in significant tensile stress after high temperature cycles. Voiding and opening-
Figure 5. A 500nm copper via chain and thermal image after hours of aging under 200 deg-C annealing test. 5a) An optical image of the via chain, 5b) Thermal
images after different annealing times, 5c) The temperature increase in each via after aging, as a function of its initial temperature rise, and 5d) Relative change in
total resistance and temperature for different vias, as a function of aging time.
14
ElectronicsCooling
March 2011
circuit failure from the cracking of interconnects is one of
the key failure mechanisms. This is particularly important in
submicron copper interconnects. The thermal annealing is
often used for accelerated aging for characterizing reliability
(time-to-failure). Typically, total interconnect resistance is
monitored as a function of aging at high temperatures. Increasing resistance is a sign of void formation but it cannot
locate problematic areas. While techniques such as scanning
electron microscopy can be used to locate open circuits,
thermal imaging can detect the local change in each via’s
resistance and in the thermal resistance of the surrounding
material before a complete failure. Figures 5a-5d show the
surface temperature rise of the 10 and 100 via chains under a
bias before and after aging at 200°C for different durations [15].
Visible wavelength thermoreflectance gives 200-300nm spatial
resolution. Localized heating in each of the 10 vias is 2-7°C
before the thermal process. After 150 hours, this increases
to 10-35°C (Figure 5b). During the aging the total resistance
of the via chain increases linearly, a large change in the rate
of the temperature increase is noticeable between 100 and
120 hours (Figure 5d). Close examination of the temperature
profile shows significant change in the heat distribution pattern around the vias, which is a result of the void formation
and the change in local thermal resistance. There is a strong
correlation between local temperature rise in each via before
high temperature treatment and that obtained after many
hours of aging (Figure 5c). This would potentially shorten the
time for reliability tests and suggest more specific solutions
to improve reliability.
for Submicron Temperature Measurements”, Electronics Cooling, Vol. 14,
February 1st, 2008.
[7] G. Tessier, S. Hole, and D. Fournier, “Quantitative Thermal Imaging
By Synchronous Thermoreflectance With Optimized Illumination
Wavelengths”, Applied Physics Letters, Vol. 78, No. 16: pp. 2267-2269,
2001.
[8] D. Lüerßen, J. A. Hudgings, P. M. Mayer, R. J. Ram, "Nanoscale thermoreflectance microscopy with 10mK temperature resolution using stochastic
resonance", Proc. 21st Annual IEEE SEMI-THERM Symp. (San Jose, CA)
pp 253-8, 2005.
[9] J. Christofferson and A. Shakouri, “Thermoreflectance Based Thermal
Microscope”, Review of Scientific Instruments, 76, 024903-1-6, 2005.
[10] J. Christofferson, K. Yazawa, A. Shakouri, "Picosecond transient thermal
imaging using a CCD based thermoreflectance system", Proc. 14th
International Heat Transfer Conference (IHTC14), 2010.
[11] D. Kendig, G.B. Alers, A. Shakouri, “Thermoreflectance imaging of defects
in thin-film solar cells”, Proc. IEEE International Physics Reliability
Symposium (IRPS), 2010.
[12] D. Kenig, A. Shakouri, “Thermal Imaging of Encapsulated LEDs”, 27th IEEE
SEMI-THERM symposium, 2011
[13] P.E. Raad, P.L. Komarov, M.G. Burzo, “Numerical Simulation of Complex
Submicron Devices”, Electronics Cooling, Vol. 15, pp. 18-22, May 2009.
[14] K. Maize, W. Xi, D. Kendig, A. Shakouri, W. French, B. O'Connell, P.
Lindorfer, P. Hopper, “Thermal Characterization of High Power Transistor
Arrays”, Proc. 25th IEEE SEMI-THERM Symposium, 2009.
[15] S. Alavi, K. Yazawa, G. Alers, B. Vermeersch, J. Christofferson, A. Shakouri,
“Thermal Imaging for Reliability Characterization on High Precision
Copper Vias in Silicon”, 27th IEEE SEMI-THERM symposium, 2011.
l
Summary
We explored our recent developments in ultrafast submicron
thermoreflectance imaging techniques. This thermoreflectance was based on the change of a sample’s reflection coefficient as a function of temperature. Imaging with megapixel
CCD cameras allowed precise detection of temperature distribution in a device. For ultrafast thermal measurements,
resolution down to 800ps was achieved. With the use of near
infrared illumination, it was possible to image through silicon
substrates as thick as hundreds of microns. We also provided
examples of thermal imaging in high power CMOS transistors,
electrostatic discharge (ESD) devices, copper interconnects,
LEDs, and solar cells.
References
[1] A. Cutolo, “Selected Contactless Optoelectronic Measurements for Electronic
Applications,” Review of Scientific Instruments, Vol. 69, pp. 337-360, 1998.
[2] J. Altet, W. Claeys, S. Dilhaire, A. Rubio, “Dynamic Surface Temperature
Measurements in ICs,”, to be published in the Proceedings of the IEEE,
Vol. 94, No. 8, pp. 1519-1533, 2006.
[3] J. Christofferson, K. Maize, Y. Ezzahri, J. Shabani, X. Wang, and A. Shakouri,
"Microscale and Nanoscale Thermal Characterization Techniques”, J.
Electronic Packaging, Vol. 130, Issue 4, 041101, 2008.
[4] P. E. Raad, “Keeping Moore’s Law Alive”, Electronics Cooling, Vol. 16 No. 4,
pp. 14-18, 2010.
[5] M. Farzaneh et al., “CCD-based thermoreflectance microscopy: principles
and applications”, Journal of Physics D: Applied Physics 42, 143001 (20pp),
2009.
[6] M. G. Burzo, P. L. Komarov, P. E. Raad, “Thermo-Reflectance Thermography
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15
Thermal Challenges in Today’s
Commercial and Military Aviation
Peter deBock and Bill Gerstler
GE Global Research, Niskayuna, New York
Peter de Bock is a Lead Thermal Systems Engineer at GE
Global Research in Niskayuna, N.Y. He has more than
8 years experience on developing innovative thermal
management solutions for electrical machines and
electronics. His current work is focused on developing
next generation heat pipe and vapor chamber systems for
civil and military electronics cooling. He holds an MSME
from Twente Technical University in the Netherlands. He is
an active reviewer for ASME and IEEE.
Bill Gerstler, senior mechanical engineer, Thermal
Systems Lab GE Global Research, received his PhD
in Mechanical Engineering from the University of
Minnesota. Since coming to GE Global Research in
2001, he has worked on thermal management of rotating
electric machines and electronics. Applications of these
products include aviation power, thermal management,
and avionics, subsea O&G industry motors, and
generators related to wind and power plants. He is a
member of AIAA and ASHRAE.
16
ElectronicsCooling
F
or aviation platforms, the goal is to design the most high
performance and lightweight systems that exceed the
required reliability standards. Military aircraft often
emphasize mission capability as the key objective, while
commercial aircraft emphasize Specific Fuel Consumption
(SFC) and overall life-cycle costs. Traditionally mechanical, hydraulic, and pneumatic drive systems have been the
technology of choice on these platforms for Environmental
Control Systems (ECS), and actuation for engine and flight
systems. These systems have proven their reliability and
capability on a variety of aircraft platforms for many years.
Recent advances in high-speed bearing and cooling technologies have enabled high-speed electrical machines to achieve
power densities that are competitive with or better than
aforementioned conventional drive systems[1]. New systems
are also desired to have improved actuation control, and be
“smart,” such that they monitor their own health[2]. All of
these demands have led to a trend where conventional systems
are being replaced with electrical systems. The increased use
of such systems brings with it an increased need for compact
and efficient power generation, conversion, and thermal
management systems.
In addition to the “electrification” trend, demand for onboard power by conventional electronic systems has been
increasing. Modern aircraft have increasingly powerful ECS,
In Flight Entertainment (IFE), and avionics systems; all adding to demand for increased on-board power. Figure 1 shows
an overview of possible systems that have the potential for
electrification on both military and civilian aircraft platforms.
Figure 2 illustrates this increasing demand for on-board
power and its rapid acceleration in recent history. The Airbus
A380 and Boeing 787 stand out as they represent the latest
modern aircraft of today. Weight savings are a key factor in
realizing SFC targets for aircraft and both these platforms
use advanced lightweight materials. Commonly, bleed air
from the engine compressor is used for cabin pressurization,
wing anti-icing systems and ECS. Breaking with this trend,
to realize further weight savings and increased efficiency, the
cabin in the Boeing 787 will be pressurized and controlled by
a 500 kVA electric motor driven compressor system using no
bleed air. As a result, the new engines for this plane, the GEnx
or Rolls-Royce Trent 1000, are unique in the sense that they
March 2011
Figure 1. Overview of actuation systems on military and civilian aircraft.
are near bleedless and have the capability to deliver up to 500
kVA per engine, more than four times the power generation
capacity of the engines on the larger Boeing 747 [4].
This trend in civilian aircraft has been preceded by a similar on-board power surge on military platforms. Increasingly
powerful avionics, fly-by-wire, electronic warfare and radar
systems have driven an accelerated demand and capability of
on-board power systems. Considering the smaller dimensions
of these military aircraft platforms, the trend of on-board
power demand on a per-passenger or per-volume basis shows
an even greater difference between military and civilian
technology.
INCREASED ELECTRIFICATION LEADS TO THERMAL
CHALLENGES
Although electrical systems are highly efficient, the sheer
magnitude of on-board power demand and unique design
aspects of on-board aviation systems lead to considerable
thermal management challenges. Even if a 1 MW system were
to be up to 95% efficient, a total of 50 kW of heat has to be
removed without exceeding acceptable junction temperatures.
This poses significant challenges to the thermal management
system, as it has to remove the total capacity of waste heat with
minimal temperature rise at a minimum of weight and volume.
Figure 3 illustrates how inefficiencies in electrical power
Figure 2. Historic and future on-board power provided by engines. Adapted from Gerstler and Bunker [3].
18
ElectronicsCooling
March 2011
Figure 3. Relation between power and thermal management.
management ultimately translate into
increased challenges to the thermal
management system. Significant thermal management is required at all
levels of power management; generation, distribution, conversion power
electronics(PE). At the application level
heat is mostly produced by avionics, or,
if present, actuators for flight control
surfaces. Efficient thermal management
is required for digital electronics, power
electronics and Environmental Control
Systems (ECS). It is not uncommon for
these systems to be cascaded; meaning
that heat rejected from one system is
added to the heat load of a secondary
system before being rejected to an ultimate heat sink such as fuel or air.
Thermal management solutions have
to be developed at different hierarchically coupled levels:
• Application level thermal management of the avionics at the chip,
board, and electronics frame, heat is
rejected to the system level thermal
management.
• System level thermal management of
the bays and vehicle platform, including heat rejection to the ultimate heat
sink
Aviation system thermal management
solutions have specific requirements to
be extremely reliable, have reduced specific weight/volume, and have a stringent
operating window. Such systems often
function in a controlled environment,
depending on whether they are located
in vented or unvented bays. Environmental conditions often include extreme
temperature ranges, pressure variations,
and the ability to withstand and operate
during high g-force maneuvers. These
specific requirements limit the appli-
cability of Commercial-Off-The-Shelf
(COTS) solutions.
Challenge of heat rejection
for aviation platforms
In addition to the challenge of moving
the heat efficiently to the convective
surface, the ultimate rejection of heat
is a challenge for aviation platforms.
Airborne platforms practically have
two heat sinks available, fuel and ambient air. Fuel is a convenient sink for
several reasons. A large quantity of fuel
is available and must be carried on the
aircraft regardless. Heating fuel prior
to it entering the engine combustor is
advantageous to the engine efficiency,
but thermal stability of conventional jet
fuel limits this. If fuel thermal limits are
exceeded, fuel can degrade by oxidizing reactions. As a result of oxidation,
viscous deposits can form in the fuel
lines. Such deposits can foul the heat
transfer surfaces, leading to decreased
heat transfer performance and/or decreased engine performance[5]. Fuel is
a liquid with good heat transfer properties. Thus the volumetric flow rates, and
the mass of the components needed to
circulate, contain, and exchange heat
with it are reasonable. Its compatibility
with various needed components, as
well as its compatibility for aviation
environmental requirements is already
well established because of its long-time
use on aircraft. It is also straightforward
to use in a primary/secondary loop type
thermal management system where turbine oil, polyalphaolefin (PAO), glycolwater mixtures, or air can be used as
the secondary coolant. Therefore, it is
generally preferred that thermal losses
associated with electrification and any
electronics-cooling.com
ElectronicsCooling
19
Figure 4. Aircraft fuel cooling requirements (adapted from [6]).
other unwanted heat sources are rejected to the fuel. There
are exceptions, for instance, if a component sits in the area of
an aircraft where the ambient air can effectively accept the
losses without the need of a scoop or other component that
increases aerodynamic drag. In that case, there would not be
a need to route fuel to that area.
The More Electric Aircraft (MEA) concept has pushed
the use of fuel as a heat sink to the limit. For some short
missions on military aircraft, the amount of fuel that will
be carried is determined by the electrical heat load rejection
capacity requirements rather than the estimated engine fuel
consumption.
While there is a large amount of fuel on-board an aircraft,
its use is not evenly distributed over the flight envelope.
20
ElectronicsCooling
During ground idle and idle-descent the fuel flow is very low.
During take-off it is extremely high. Thus the fuel flow to the
combustor nozzles rarely matches the electrical loss removal
demands required by an MEA. For instance, an aircraft electrical system often requires significant cooling during idledescent when electrical loads are relatively high (actuation of
flight control surfaces), but fuel flow is extremely low. To meet
the cooling requirements, it is often required that the fuel is
circulated back into the fuel tank after being used for cooling. This return-to-tank arrangement is common on military
platforms. Using the fuel tank for thermal energy storage is
convenient, but also has its limitations. At the beginning of the
mission the hot fuel returning to tank does not significantly
increase the overall temperature of the fuel in the tank because
of the large thermal mass available. As the mission progresses
and fuel levels are reduced, the high temperature return fuel
has an increasingly greater effect of raising the temperature
of the fuel in the tank. The latest military aircraft, and presumably future aircraft [6] (Figure 4), have such high cooling
demands that even with the return-to-tank arrangement, the
fuel simply does not have enough cooling capacity and alternative options such as fuels with improved thermal stability
and refrigeration of fuel prior to take-off are being explored.
The other ultimate heat sink is the ambient air. Air is
abundantly available around the aircraft. The quality of this
air for use as a heat sink varies widely. On the ground, air
can be extremely cold or hot. The air density at 2,700 meters
is about 2/3 that at sea level, and at 5,500 meters 1/2 that at sea
level. Although air at high altitude is cold, viscous heating in
the boundary layer can be significant, especially at supersonic
velocities. These factors combined make air a much less effective cooling fluid than fuel at high altitude, especially at
high speeds. Typical environmental design requirements for
electronics in unpressurized aircraft areas include being able
to operate in conditions ranging from -55 °C up to +85 °C.
The lower temperature includes extreme ground and high
altitude conditions, while the upper temperature limit takes
into account the temperature that can be obtained in the
unpressurized aircraft bays.
Exchanging heat with air is also challenging. Air is not a
great heat transfer fluid, thus significant heat exchanger surface area is often needed. During flight, air can be scooped
from the surrounding aircraft space and passed through a duct
where it interacts with various heat exchangers. Cooling air
obtained in this manner is known as “ram air”. Because of the
aircraft velocity, little or no fan power is needed to drive the air
through the heat exchangers. However, scooping air changes
the aerodynamics of the aircraft and induces drag, resulting in
a fuel burn increase. In addition, if the components dumping
heat into this heat sink require cooling during ground idle,
a fan or similar fluid pumping device is required to move air
across the heat exchangers, or the heat exchangers must be
designed very large to allow for natural convection based
cooling. In the engine area, heat exchangers can be placed in
the bypass airstream in various ways, including a traditional
heat exchanger directly in the airflow, or a surface cooler inside
the engine fan bypass.
Because of their long distance from the engines, and relatively high heat loads, civilian aircraft environmental control
March 2011
systems (ECS) often use ram air to cool the ECS condensers.
In both military and civilian aircraft, surface or direct coolers within the engine fan bypass are often used to reject heat
from the fuel and oil, decreasing the burden on the fuel as a
heat sink.
As the need to reject heat to the ambient increases with
increasingly more electric aircraft, traditional solutions such
as fuel cooling and ram air-cooling become problematic. One
of the major reasons for switching to MEA is decreased fuel
usage. Rejecting the heat associated with MEA using traditional solutions results in excessive mass, drag, and ultimately
fuel usage. It is clear that a system level approach is needed to
trade-off possible solutions. In addition, new inventions in the
area of heat rejection and thermal storage will be invaluable
to finding the proper solution. There are various military and
civilian programs that currently seek to address the issue at
the system level, and progress is expected to continue in the
upcoming years.
CONCLUSION
Aircraft such as the Airbus A380, Boeing 787, F-35, and F-22
have in common that they employ state-of-the-art systems
requiring large amounts of on-board electrical power. Especially for military platforms, power demand has been rising
sharply. Associated with this trend, is an increased need for
efficient and optimized power conversion and distribution, and
thermal management systems. High power electrical systems
on aircraft flying at high-speed and high altitude present
unique thermal challenges both at the application and system
level. Efficiency improvements of the electrical components
and thermal management system at the application level have
the potential to be multiplied to greater benefits if the impact
on the power and thermal management hierarchies are taken
into account. Design of the thermal management solution can
greatly benefit from a system-level approach to determine
how to optimize the beneficial attributes of a component level
improvement. Heat rejection remains an additional challenge
under the conditions at which these aircraft operate. It is
through advances in thermal management and system design
engineering that key technologies are developed enabling
operation of next-generation aircraft platforms.
References
[1] De Doncker, R., Pulle, D. and Veltman A., “Advanced Electrical Drives:
Analysis, Modeling, Control”, Springer, New York, 2010.
[2]John Croft, “MRO USA: Engine Diagnostics: GE opens the envelope”,
http://www.flightglobal.com/articles/2010/04/20/340710/mro-usa-enginediagnostics-ge-opens-the-envelope.html, 2010.
[3]Gerstler, W.D., and Bunker, R.S., “Aviation Electric Power”. Mechanical
Engineering, December 2008, pp 74-75.
[4]Moir, I. and Seabridge, A., “Aircraft Systems, mechanical, electrical
and avionics subsystems integration”, 3rd edition, John Wiley & Sons,
Chichester, England, 2008.
[5]Faith, L.E., Ackerman, G.H., and Henderson, H.T., “Heat Sink Capability
of Jet A Fuel: Heat Transfer and Coking Studies”, Shell Development Co.,
S–14115, NASA CR–72951, 1971.
[6]USAF Scientific Advisory Board, “New World Vistas: Air and Space Power
for the 21st Century”, Materials Volume, Washington, D.C., 1996.
l
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ElectronicsCooling
21
Reasons to Use Two-Phase
Refrigerant Cooling
Jackson Marcinichen, Jonathan Olivier, and John R. Thome
Heat and Mass Transfer Laboratory (LTCM), École Polytechnique Fédérale de
Lausanne (EPFL), Switzerland
Dr. Jackson Braz Marcinichen is a Research Post Doc
at the Laboratory of Heat and Mass transfer at the
EPFL (Lausanne-Switzerland) and has over 15 years
experience in HVAC & R systems. He received his BE
in Mechanical Engineering from the Federal University
of Santa Catarina, Brazil in 1996, and his PhD in
Mechanical Engineering from the same university in
2006. He has authored over 20 technical papers in
journals, conferences, book chapters and US patents.
He has designed and evaluated several experimental
facilities characterizing the thermo- and hydrodynamic
of cooling systems (calorimeters, wind tunnel, hybrid
systems etc). Today he is engaged in the development of a
new novel hybrid cooling system to cool high performance
microprocessors using on-chip cooling.
Jonathan Olivier received his bachelors and master’s
degrees from the University of Johannesburg in
2002 and 2003 and his PhD degree in Mechanical
Engineering from the University of Pretoria, South
Africa in 2009. He is currently working as a research
scientist at the Laboratory of Heat and Mass Transfer
(LTCM), Swiss Federal Institute of Technology Lausanne
(EPFL), Switzerland, with his main research area being
microchannel two-phase refrigerant cooling for high heat
flux applications. His other research interests are
single-phase flow and heat transfer inside enhanced
macro-scale tubes in the transition regime as well
as single and two-phase flow and heat transfer in
microchannels and has authored and co-authored 19
journal articles and conference papers in these areas.
Prof. John Richard Thome has been working at the
Swiss Federal Institute of Technology Lausanne (EPFL)
since 1998, where he is a Director of the Laboratory
of Heat and Mass Transfer (LTCM) and the Director of
Doctoral Program in Energy (EDEY). He received his PhD
in Mechanical Engineering at Oxford University in 1978
and worked as an Assistant/Associate Professor in the
USA for 5 years at Michigan State University. He worked
full-time as a consulting engineer for 15 years from
1984 through 1998 with his own firm. He has over 120
journal papers and 4 books since joining the EPFL. His
current main areas of research are two-phase flow and
heat transfer in microchannels, cooling systems for high
heat flux sources and energy recovery systems. All this
research has a total funding of over $1.5 million.
22
ElectronicsCooling
W
ater-cooling at the rack appears to be the new
short-term technological solution for server
cooling in data centers, with its advantages over
traditional cold aisle/hot aisle air-cooling being clear, as can
be seen in [1]. Bringing chilled water to the rack and then
cooling the air inside the rack aids with the transport of
energy across the datacenter, making the necessity for large
air-handling systems to cool large, unnecessary, volumes of
air a thing of the past. This has an overall advantage in that
the servers can now be cooled locally (only if the rack is in
operation), which saves energy and opens the opportunity for
more densely packed rack units, but still requires chillers for
the cold water cooling supply. Long-term, with microprocessor performance increasing, the limits of air-cooling technology are being reached, i.e. forced-air heat sinks have become
significantly larger, more expensive and more complex [2],
imposing a challenge for the development of a more drastic
cooling approach.
One solution attracting a lot of interest, at least in the academic sphere, is direct “two-phase on-chip cooling”, that is,
placing a micro-evaporator heat sink directly on the back of
the chip, since most of the energy generated in a datacenter is
accounted for by the microprocessor, and simpler evaporator
cooling elements on the other heat generating units (memory,
etc.). In fact, microchannel cooling is a promising technology for high heat flux removal that has a low pumping power
requirement relative to the quantity of heat to be removed.
Figure 1 shows some typical microchannel coolers tested in
the LTCM lab at the EPFL, having channel widths from 50 μm
to 200 μm and fin heights from 50 μm to 2 mm. Included is
a silicon microchannel-evaporator having a fin height of 560
μm, fin width of 42 μm and a channel width of 85 μm. A firstof-a-kind prototype was tested early in 2009, which removed a
heat flux of 180 W/cm 2 using refrigerant R134a at a saturation
temperature of 60˚C, while maintaining the chip junction
temperature below 85˚C has been described by Madhour et
al. [3]. Hence, cooling can be achieved by evaporating a fluid
significantly above ambient temperature and dissipated to the
ambient (or recovering the waste heat for other uses) and thus
water chillers are no longer needed.
Other technologies can also be found in the literature, such
as liquid immersion [4] and spray cooling [5], each one with its
March 2011
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Figure 1. Typical microchannels in copper and silicon for micro-evaporator
coolers.
advantages, challenges to be implemented and specific field of
application. For example, Tuma [4] evaluated the liquid immersion technology, which proved to be simpler, denser, much
less expensive and more efficient than any other liquid cooling technology. However, the technology is only suitable for
low heat flux applications (12 W/cm 2). Regarding spray cooling, Finch and Ballew [5] showed an interesting comparison
between air natural, air forced and liquid forced convection,
liquid immersion and direct spray. According to the authors,
for a 30˚C of temperature difference between the chip and the
fluid, the direct spray was able to remove from 6 to 90W against
0.02 to 0.09W, 0.06 to 1.2W, 0.3 to 4.8W and 2.4 to 30W for
the other technologies, respectively. They characterized such
technologies for applications in harsh environments, such as
manned and unmanned military platforms, capable of working at temperatures of -65˚C or +60˚C.
Today, there is a huge initiative to introduce “single-phase
water on-chip cooling” using copper microchannel coolers, as
attested to by the Aquasar project [6] (a joint project involving
IBM, ETH and EPFL in Switzerland). In that project water at
60-70°C is used to cool the chips of a server with the waste
heat being recovered into a heat pump system, illustrating that
there are numerous advantages of using water as the cooling
medium. On the other hand, “two-phase on-chip cooling”
also has many thermal and energetic advantages. However,
due to the perceived complexity of the two-phase flows by
non-specialists, this solution is not yet well understood by the
thermal packaging community. Considering here that “singlephase water on-chip cooling” is the leading technology both
for cooling of high heat fluxes and for its low pumping power
consumption compared to air-cooled systems, the comments
about the advantages of two-phase cooling below are presented
with water-cooling in mind.
COMPATIBILITY WITH ELECTRONICS
When working alongside electronics, water has obvious risks
whilst refrigerants on the other hand are inherently dielectric
fluids, meaning that even with a leak, the electronics will be
safe from damage. In fact, some earlier generations of super
computers, such as the CRAY-2 and CRAY T90, had their
Figure 2. Total pressure drop and pumping power consumption.
Figure 3. System volume and mass of working fluid.
24
ElectronicsCooling
March 2011
Figure 4. Effect hotspots on heat transfer coefficients (left) and junction temperatures (right) for R134a, water, and a 50% ethylene-glycol water mixture along the
length of a chip.
electronics submerged in refrigerants, making use of pool
boiling as the main heat transfer mechanism. Likewise, there
is significant experience with two-phase cold plates for cooling
of the IBM Z-series mainframes. Hence, there is already a long
industrial experience in the handling of refrigerants without
leaks in computer cooling applications.
Pumping power
Simulations and experiments have shown that refrigerants have
a clear advantage regarding pumping power relative to singlephase water [7]. This is due to refrigerants making use of latent
heat removal (about 150 kJ/kg), unlike water (4.2 kJ/kg) that uses
sensible heat removal, the former requiring about 1/10 of the
flow rate. Hence two-phase cooling requires much less pumping power to remove the same amount of heat. Figure 2 shows
the pressure drop and pumping power requirements simulated
for a complete microchannel cooled rack [7]. The first plot is
for R134a as the working fluid with cooling pipe diameters of
3 mm throughout, while the other plots are for water as the
working fluid for various pipe diameters, ranging from 3 mm
to 15 mm. For the single-phase watered cycle to have the same
overall pressure drop as the two-phase refrigerant cycle (the
simulations considered 30% of micro-evaporator outlet vapor
quality), the inner diameter of the piping was more than double,
6.2 mm vs. 3.0 mm. However, even with the pressure drops
being the same, the pumping power for the water cycle is still
more than 9 times higher than for the refrigerant cycle because
of its much larger flow rate. For the system using water to have
the same pumping power as the two-phase system, cooling pipe
diameters need to be 5 times that for R134a.
It is worth mentioning that the reason for a smaller system
volume and mass of water when increasing the diameter from
3 mm to 6.2 mm (viz. Figure 3) is due to the size of the heat
exchanger. As can be observed in Figure 2, there is a huge difference in pumping power when considering the water cooling
cycle with different diameters. This difference in power represents the additional heat load that must to be removed in the
condenser, assuming all energy from the pump is transferred
to the fluid. When increasing the diameter even further, the
Piping
Small diameter pipes are advantageous as they are lighter
in weight, require less coolant, are more flexible and can be
easily installed in confined spaces, an aspect which is very
important in electronic equipment. Figure 3 shows that the
required system volume and mass of working fluid, when using single-phase water (3 mm of piping diameter), is about 4
and 3.5 times more, respectively, than when using two-phase
refrigerant.
electronics-cooling.com
ElectronicsCooling
25
opposite trend is seen since the piping becomes the dominant
reason for the volume increase rather than the heat exchanger
size due to the pumping power dissipation.
Material compatibility
Refrigerants have a long and successful history in the refrigeration and air-conditioning industries with material compatibility well understood. Refrigerants are mostly used with copper
and aluminum, with some refrigeration systems running for
over 30 years. The use of water, on the other hand, is more
problematic, as it is known to attack metallic components unless treated, with ultra-clean water being especially corrosive.
Organic/Fouling
Water is the essence of life, meaning here that organic material
tends to grow inside the system. Thus, water is treated to try
to prevent organic growth. Nevertheless, water tends to foul
its containment, degrading the heat transfer performance of
the cold plate and could eventually block the microchannels,
rendering such a microchannel cooler unreliable. Refrigerants
are not subject to organic growth or fouling.
Erosion
Erosion occurs due to the shear stress exerted by the flowing
fluid on the channel wall, especially in joints. Guidelines for
water flowing inside copper pipes suggest that water velocities should be kept below 0.5-1.2 m/s, depending on the water
temperature. Erosion can lead to the thinning of the piping or,
in the case of the microchannel cooler, the thinning of the fins,
which would degrade their performance. Furthermore, erosion
contaminates the fluid with particles, which would need to
be filtered out, or adversely affect the fluid pump. Due to the
high mass flow rates required when using water for electronics cooling, erosion is a design concern. The flow rates (and
velocities) of the refrigerants are typically much less as noted
above and are known not to have significant erosive properties.
Hot spot management
Hot spots on microprocessors are a topic of much discussion
due to their negative impact on the chip’s life cycle. Large temperatures and temperature gradients lead to thermal stresses
between the layers of cooling materials, while also having a
huge effect on the timing of the transistors. Refrigerants, unlike single-phase fluids, have a self-enhancing effect when it
comes to hot spots. This is shown in Figure 4, which is a comparison of R134a, water and a 50% ethylene-glycol mixture for
a chip having a base heat flux of 50 W/cm2 and each hot spot
having a heat flux of 250 W/cm2 (5-to-1 ratio), assuming parallel microchannels of 1.7 mm height/ 0.17 mm thickness and
0.17 mm channel width. The refrigerant reacts to the hot spot
by increasing the local heat transfer coefficient (decreasing
the local thermal resistance), whilst the single-phase liquids
heat up (further exasperating the problem). This is evidenced
in the junction temperatures shown at the right of Figure 4,
with R134a having much lower temperature differences. This
has also been experimentally observed at the LTCM lab for a
pseudo-chip cooled with a micro-evaporator cooler with 35
local heaters and temperature sensors.
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ElectronicsCooling
A problem often encountered in cooling systems exposed to
the environment is that the cooling fluid needs to resist very
cold and/or hot climates. Water freezes at temperatures below
0˚C, creating a problem in the winter on most places on the
earth. However, glycol added to water, which decreases the
freezing temperature, degrades the heat transfer performance
and increases the required pumping power quite considerably (by about 50%). Hence, water cooled systems need to be
charged on location. Refrigerants, on the other hand, have very
low freezing temperatures (< -100˚C) and are ideal for harsh
conditions. The critical point for most refrigerants is also on
the order of 100˚C, which is the upper limit of a two-phase
system. On the other hand, the saturation pressure of the
refrigerant becomes very high at high temperatures, creating
a maximum working pressure issue.
Heat dissipation
Two-phase refrigerants also have the advantage of being able to
dissipate heat to higher temperatures using a vapor compression cooling cycle (heat pump). Therefore, chip or electronics
temperatures can be maintained at a convenient operating
temperature and heat can be discharged at temperatures
above ambient. This allows for a longer life cycle of electronic
components in harsh operating conditions.
Environment
Refrigerants are becoming much more environmentally
March 2011
friendly, with the development of so-called fourth generation
refrigerants. One of these refrigerants, R1234yf, resulting from
a joint development of DuPont and Honeywell, is considered to
be one of these. Having thermal characteristics and properties
similar to that of R134a, it is seen as a very good replacement.
Environmentally, though, it is much greener, having a global
warming potential of only 4 (1320 for R134a), an atmospheric
lifetime of 11 days (14 years for R134a) and an ozone depletion
potential of zero.
Complexity
Usually the most widely used reason not to consider a twophase cooling solution in favor of a liquid cooling system is
the “complexity” of two-phase flow. This “complexity” is primarily related to a lack of two-phase flow and heat transfer
(boiling and condensation) expertise in the thermal packaging
industry. Two-phase specialists have been successfully designing refrigeration and air-conditioning systems for nearly a
century, including applications in demanding environments.
Hence this issue is easily remedied with more training of new
personnel with such experience.
Above, the most prominent advantages of two-phase cooling have been addressed…one could also speak of the smaller
size of the refrigerant pump with its 1/10 flow rate compared
to a water pump. It is clear, though, that for industry to move
forward regarding electronics cooling, it needs to adapt a
cooling technology that is reliable, efficient, well known and
that provides a long-term energetically sound, green solution.
Two-phase on-chip cooling with microchannel refrigerant
cooling technology appears to be a good long-term solution.
For those interested in more details on two-phase flow, boiling and condensation in microchannels, please refer to the
free online book of Thome [8] where over 200 two-phase flow
videos are available in Chapter 1 while Chapters 20 and 21
deal specifically with the detailed state-of-the-art reviews of
microscale two-phase flow and heat transfer.
Finally, it is important to highlight that to implement
such a new novel cooling technology some challenges must
be overcome. We can list, for example, the control of microevaporator outlet vapor quality (important to guarantee a high
performance of the micro-evaporator and avoid dry-out) and
the flow distribution for several micro-evaporators operating in a rack populated with several chips under different and
variable heat loads. These problems, however, are not unique
to two-phase micro-evaporator cooling and are also found in
most of the other cooling technologies. We can also detach
that nowadays, with the growth of the electronics field, new
variable components (flow drivers, electrical valves etc) are
in continuous development and are available in the market,
allowing the design of smart control strategies for cooling
systems, which not only saves energy but also offers better
stability and control to the systems [9]. Actually, the LTCM
lab is testing a hybrid cooling system capable of evaluating
the performance of three different two-phase cooling cycles
using micro-evaporators in parallel with cooling capacities up
to 600 W. Until now the results are promising, showing good
controllability for the micro-evaporators outlet vapor quality
and good flow distribution for non-uniform heat loads, all this
using very simple control strategies.
References
[1]Whitenack, K., "Liquid Cooling for Datacom Equipment Centers,"
ElectronicsCooling. August 2008.
[2]Mackey, S. and Hannemann, R., "Advanced Cooling Using Meso-Scale
Evaporative Cold Plates," ElectronicsCooling. November 2007.
[3]Madhour, Y., Olivier, J.A., Costa-Patry, E., Paredes, S., Michel, B., and
Thome, J.R., "Flow Boiling of R134a in a Multi-Microchannel Heat
Sink with Hotspot Heaters for Energy-Efficient Microelectronic CPU
Cooling Applications," IEEE Transactions on Components and Packaging
Technologies, Accepted for publication, 2010.
[4]Tuma, P.E., "Open Bath Immersion Cooling In Data Centers: A New Twist
On An Old Idea," ElectronicsCooling. December 2010.
[5]Finch, A. and Ballew, E., "Direct Spray Cooling and System-level
Comparisons," ElectronicsCooling. August 2009.
[6]Ganapati, P. "Water-Cooled Supercomputer Doubles as Dorm Space
Heater," 2009, Available from: http://www.wired.com/gadgetlab/2009/06/
ibm-supercomputer/
[7]Marcinichen, J.B. and Thome, J.R. "New Novel Green Computer TwoPhase Cooling Cycle: A Model for Its Steady-State Simulation," ECOS2010
- 23rd International Conference on Efficiency, Cost, Optimization,
Simulation and Environmental Impact of Energy Systems. 2010. Lausanne
- Switzerland.
[8]Thome, J.R., ENGINEERING DATABOOK III, in Web-based reference
book available for free at the website, 21 chapters so far, available at: http://
www.wlv.com/products/databook/db3/DataBookIII.pdf. 2010.
[9]Marcinichen, J.B., Holanda, T.N., and Melo, C., "A Dual Siso Controller for
a Vapor Compression Refrigeration System" International Refrigeration
and Air Conditioning Conference at Purdue. July 14-17, 2008.
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Buyers’
Guide
products & services index
The Products & Services Index contains nearly 50 categories to help you find the
equipment, components, and services you need. Locate additional product information
by consulting the Advertiser Index on page 32. Companies listed in bold are advertisers.
Full details of all the suppliers listed within each category can
be found in the Company Directory, starting on page 30.
Adhesives
Chillers
3M Electronics Markets Materials Division
Device Technologies, Inc.
Diemat, Inc.
Dow Corning Corporation
Ellsworth Adhesives
Henkel
ResinLab
Aqua Product Company
Aspen Systems, Inc.
Lytron
Chatsworth Products, Inc.
Curtiss-Wright Controls Electronic Systems
Elma Electronic
Extreme Engineering Solutions
MEN Micro, Inc.
Youthen Technology Co., Ltd.
Circuit Assembly Materials
Epoxy
Indium Corporation
SinkPAD Corporation
Diemat, Inc.
Advanced Materials
Indium Corporation
Minteq International, Inc.
Rogers Corporation
Stablcor
Taica Corporation
Air Conditioners
Aqua Product Company
Aspen Systems, Inc.
EXAIR Corporation
Ice Qube, Inc.
Vortec, ITW Air Management
Air Filters
Universal Air Filter Co.
AISiC Component
CPS Technologies
Rogers Corporation
Baseplates
CPS Technologies
Wolverine Tube Inc. - MicroCool Division
Blower/Fan Accessories
EAO, Ltd.
Elma Electronic, Inc.
ORION Fans
SEPA EUROPE GmbH
STEGO, Inc.
Sunon, Inc.
Universal Air Filter Co.
Blowers
Allied International
Delta Products, Corp.
EAO, Ltd.
ebm papst
Nidec America Corporation
OLC, Inc.
SEPA EUROPE GmbH
Sunon, Inc.
Waypoint Thermal Management, Inc.
Cold Plates
Delta Engineers
Lytron
Malico, Inc.
Minteq International, Inc.
Parker Hannifin Corporation
Summit Thermal System Co., Ltd.
Vette Corp.
Wolverine Tube Inc. - MicroCool Division
Composites
Spectra-Mat, Inc.
Stablcor
Connectors
Amphenol Industrial Operations
Aries Electronics
Indium Corporation
LCR Electronics
Parker Hannifin Corporation
Staubli Corporation
Coolers
Alpha Novatech
Aspen Systems, Inc.
EXAIR Corporation
Nextreme Thermal Solutions
Nuventix, Inc.
Vette Corp.
Vortec, ITW Air Management
Zalman Tech Co., Ltd.
Cooling System Compressors
Aspen Systems, Inc.
Couplings
Staubli Corporation
Education Courses / Seminars
Biber Thermal Design
Future Facilities Inc.
Enclosures
Aitech Defense Systems
28 ElectronicsCooling
Fan Filters
Ice Qube, Inc.
Universal Air Filter Co.
STEGO, Inc.
Sunon, Inc.
Fan Trays
Delta Products, Corp.
ebm papst
Elma Electronic, Inc.
Nidec America Corporation
NMB Technologies
ORION Fans
STEGO, Inc.
Sunon, Inc.
Waypoint Thermal Management, Inc.
Fans
Allied International
Cofan USA
Delta Products, Corp.
EAO, Ltd.
ebm papst
Nidec America Corporation
Nuventix, Inc.
OLC, Inc.
ORION Fans
SEPA EUROPE GmbH
STEGO, Inc.
Sunon, Inc.
Waypoint Thermal Management, Inc.
Zalman Tech Co., Ltd.
Gap Filler Pads
Alfatec GmbH & Co.
Aqua Product Company
AOS Thermal Compounds
The Bergquist Company
Brady Corporation
Device Technologies, Inc.
Fujipoly America Corp.
Stockwell Elastomerics, Inc.
Timtronics
Heat Exchangers
Caliente LLC
Curtiss-Wright Controls Electronic Systems
Heatron, Inc.
Ice Qube Inc
Lytron
Thermacore, Inc.
March 2011
2011 ElectronicsCooling Buyers’ Guide
Heat Pipes
Delta Engineers
Mersen
Radian Heatsinks
Sunon, Inc.
Thermacore, Inc.
TTM Co., Ltd.
Heat Sinks
Alpha Novatech
Celsia Technologies
Cofan USA
Cool Polymers, Inc.
Fischer Elektronik GmbH & Co. KG
Heatron, Inc.
Malico, Inc.
Mersen
Minteq International, Inc.
Nuventix, Inc.
OLC, Inc.
Radian Heatsinks
Seifert Electronic GmbH & Co. KG
Singapore Institute of Manufacturing Technology
SinkPAD Corporation
Spectra-Mat, Inc.
Summit Thermal System Co., Ltd.
Sunon, Inc.
Thermal Solution Resources, LLC
Youthen Technology Co., Limited
Heat Spreaders
3M Electronics Markets Materials Division
Celsia Technologies
CPS Technologies
Minteq International, Inc.
Rogers Corporation
SinkPAD Corporation
Stablcor
Thermacore, Inc.
Elma Electronic, Inc.
Malico, Inc.
Mersen
Parker Hannifin Corporation
Summit Thermal System Co., Ltd.
Thermacore, Inc.
Vette Corp.
Wolverine Tube Inc. - MicroCool Division
Dow Corning Corporation
Ellsworth Adhesives
Indium Corporation
ResinLab
TTM Co., Ltd.
Zalman Tech Co., Ltd.
Passive Air Cooling
Alpha Novatech
Biber Thermal Design
Chatsworth Products, Inc.
Cofan USA
Daat Research Corp.
Enerdyne Solutions
Future Facilities Inc.
Heatron, Inc.
Mentor Graphics Corporation- Mechanical Analysis
Division
Thermal Solution Resources, LLC
Alpha Novatech
Chatsworth Products, Inc.
Elma Electronic, Inc.
Singapore Institute of Manufacturing Technology
Phase Change Materials
Alfatec GmbH & Co.
The Bergquist Company
Brady Corporation
Fujipoly America Corp.
Henkel
Indium Corporation
TTM Co., Ltd.
Sensors, Test &
Measurements
DegreeC
FLIR Commercial Systems, Inc.
Nextreme Thermal Solutions
OptoTherm, Inc.
Sensor Products, Inc.
Temperature@lert
Services
Daat Research Corp.
Mechanical Solutions, Inc.
Infrared Imaging
Software (Simulation)
FLIR Commercial Systems, Inc.
OptoTherm, Inc.
A.J. Wishart
Daat Research Corp.
Future Facilities Inc.
Mechanical Solutions, Inc.
Mentor Graphics Corporation- n Analysis Division
Thermal Solutions Inc.
Interface Materials
3M Electronics Markets Materials Division
Alfatec GmbH & Co.
Alpha Novatech
AOS Thermal Compounds
The Bergquist Company
Brady Corporation
Device Technologies, Inc.
Diemat, Inc.
Dow Corning Corporation
Ellsworth Adhesives
Enerdyne Solutions
Fujipoly America Corp.
Henkel
Indium Corporation
Minteq International, Inc.
Plansee SE
ResinLab
Rogers Corporation
Schlegel Electronic Materials
Stockwell Elastomerics, Inc.
Laboratories, Test & Research
Anter Corporation
Liquid Cooling
Aspen Systems, Inc.
Curtiss-Wright Controls Electronic Systems
Delta Engineers
Substrates
The Bergquist Company
Minteq International, Inc.
Rogers Corporation/Curamik
SinkPAD Corporation
Spectra-Mat, Inc.
Thermal Design Services
Thermal Tapes
3M Electronics Markets Materials Division
The Bergquist Company
Stockwell Elastomerics, Inc.
Thermal Testing
Anter Corporation
Enerdyne Solutions
FLIR Commercial Systems, Inc.
Indium Corporation
OptoTherm, Inc.
Singapore Institute of Manufacturing Technology
Taica Corporation
Thermal Engineering Associates, Inc.
Thermally Conductive
Graphite Fibers
Minteq International, Inc.
Taica Corporation
Thermally Conductive
Molding Comp/Fillers
Cool Polymers, Inc.
Thermal Solution Resources, LLC
Thermoelectric Coolers
Caliente LLC
Nextreme Thermal Solutions
Thermoelectric Module
Temperature Controllers
Controllers
Caliente LLC
STEGO, Inc.
Temperature@lert
Caliente LLC
Test Equipment
Celsia Technologies
Radian Heatsinks
Thermacore, Inc.
Anter Corporation
Indium Corporation
Mentor Graphics Corporation- Mechanical Analysis
Division
Sensor Products, Inc.
Teseq
Thermal Compounds
AOS Thermal Compounds
Cool Polymers, Inc.
electronics-cooling.com
Vapor Chambers
Vortex Tube Coolers
EXAIR Corporation
Vortec, ITW Air Management
Contact Sarah Long at
editor@electronics-cooling.com
for additions to the Buyers’ Guide.
ElectronicsCooling 29
1
1
0
2
company directory
M anufacturers, consultants and service organizations active in the electronics
cooling field are listed in this directory. The listings of advertisers in this issue are marked
with the page numbers of their advertisements. To learn how to be included in this directory,
please e-mail info@electronics-cooling.com.
Buyers’
Guide
1-9
Aries Electronics........................................................
CPS Technologies......................................................
Aspen Systems Inc....................................................
Curtiss-Wright Controls Electronic Systems...
B
D
2609 Bartram Road, Bristol, PA 19007
215-781-9956; Fax: 215-781-9845
info@arieselec.com
www.arieselec.com
3M Electronics Markets Materials Division.....
3M Center, Bldg. 225-3S-06, St. Paul, MN 55144-1000
866-599-4227; Fax: 651-778-4244
electronicmaterials.com
www.3M.com/electronics
A
184 Cedar Hill St., Marlborough, MA 01754
508-481-5058, ext. 119; Fax: 508-480-0328
Jim Burnett, jburnett@aspensystems.com
www.aspensystems.com
Aitech Defense Systems..........................................
The Bergquist Company...........................................
......................................................Inside Front Cover
19756 Prairie St., Chatsworth, CA 91311
888-248-3248; Fax: 818-718-9787
www.rugged.com
18930 West 78th St., Chanhassen, MN 55317
952-486-6359; Fax: 952-835-0430
Markus Benson, markusb@bergquistcompany.com
www.bergquistcompany.com
Alfatec GmbH & Co. - Kerafol.................................
Biber Thermal Design...............................................
Meckenloher Strasse 11, Rednitzhembach 91126, Germany
+49-9122-9796-0; Fax: +49-9122-9796-60
Holger Schuh, info@alfatec.de
www.alfatec.de
Allied International....................................................
7 Hill St., Bedford Hills, NY 10507
914-241-6900; Fax: 914-241-6985
sales@alliedinter.com; www.alliedinter.com
6826 SW 10th Ave., Portland, OR 97219
503-892-3771; Fax: 503-892-3771
Cathy Biber, cathy@biberthermal.com
www.biberthermal.com
Brady Corporation......................................................
6555 W. Good Hope Road, Milwaukee, WI 53201-0571
Andy Chou, andy_chou@bradycorp.com
www.bradydiecut.com/thermal
C
Caliente LLC..................................................................
Alpha Novatech......................Inside Back Cover
473 Sapena Ct. #12, Santa Clara, CA 95054-2427
408-567-8082; Fax: 408-567-8053
sales@alphanovatech.com
www.alphanovatech.com
Amphenol Industrial Operations...........................
40-60 Delaware Ave., Sidney, NY 13838
215-781-9956; Fax: 215-781-9845
info@amphenol-aio.com
www.amphenol-industrial.com
Anter Corporation.......................................................
1700 Universal Road, Pittsburgh, PA 15235
412-795-6410; Fax: 412-795-8225
Bob Purvis, sales@anter.com
www.anter.com
AOS Thermal Compounds........................................
22 Meridian Road, Suite 6, Eatontown, NJ 07724
732-389-5514; Fax: 732-389-6380
John Ziemski, sales@aosco.com
www.aosco.com
Aqua Product Company............................................
PO Box 39, Prosperity, SC 29127
800-849-4264; Fax: 803-321-1980
J.R. Seppamaki, jr@aquaproductscompany.com
www.aquaproductscompany.com
30 151 Taylor St., Littleton, MA 01460
978-952-2017; Fax: 978-952-8957
systeminfo@curtisswright.com
www.cwcelectronicsystems.com
Daat Research Corp...................................................
A.J. Wishart.................................................................
129 Gore St., Fitzroy, Victoria 3065, Australia
+61 3 9419 4438; Fax: +61 3 9419 4438
Allan Wishart, allan@awdabpt.com.au
www.awdabpt.com.au
111 South Worcester St., Norton, MA 02766
508-222-0614; Fax: 508-222-0220
Bo Sullivan, bsullivan@alsic.com
www.alsic.com
1501 E. Berry St., Fort Wayne, IN 46803
260-426-3800; Fax: 260-426-3838
Mike Kelly, mike@heatsmarter.com
www.heatsmarter.com
Celsia Technologies..................................................
175 SW 7th St., Suite 1607, Miami, FL 33130
408-577-1407; Fax: 408-779-9196
George Meyer, gmeyer@celsiatechnologies.com
www.celsiatechnologies.com
Chatsworth Products, Inc........................................
31425 Agoura Road, Westlake Village, CA 91361
800-834-4969; Fax: 252-514-2977
Sabrina Cooper, scooper@chatsworth.com
www.chatsworth.com
Cofan USA................................................................ 24
PO Box 5484, Hanover, NH 03755
603-643-2999; Fax: 603-643-2990
Peggy Chalmers, info@daat.com
www.daat.com
DegreeC....................................................................25
18 Meadowbrook Drive, Milford, NJ 03055
603-672-8900; Fax: 603-672-9565
www.degreec.com
Delta Engineers...........................................................
PO Box 1215, Sunset Beach, CA 90742
714-840-9673; Fax: 714-846-5012
Nagui Mankaruse, P.E., mankaruse@aol.com
Delta Products Corp................................................7
4405 Cushing Parkway, Fremont, CA 94538
510-668-5100; Fax: 510-668-0680
mkt-serv@delta.com.tw
www.delta.com.tw
Device Technologies, Inc........................................
155 Northboro Road, Unit 8, Southborough, MA 01772
508-229-2000; Fax: 508-229-2622
Shannon Goyette, sgoyette@devicetech.com
www.devicetech.com/Docs/DTIM_Series.pdf
Diemat, Inc....................................................................
19 Central St., Byfield, MA 01922
978-499-0900; Fax: 978-499-8484
Kevin A. McLaughlin, info@diemat.com
www.diemat.com
Dow Corning Corporation........................................
2200 West Salzburg Road, Midland, MI 48686
800-637-5377; Fax: 989-496-6731
electronics@dowcorning.com
www.dowcorning.com/electronics
E
EAO, Ltd..........................................................................
46177 Warm Springs Blvd., Fremont, CA 94539
800-766-6097; Fax: 510-490-7931
Chang Han, info@cofan-usa.com
www.cofan-usa.com
Highland House, Albert Drive, Burgess Hill, West Sussex, RH15
9TN, United Kingdom
+44 1444 236000; Fax: +44 1444 236641
Robert Davies, robert.davies@eao.com
www.eao.co.uk
Cool Polymers, Inc.....................................................
ebm papst...............................................Back Cover
51 Circuit Drive, North Kingstown, RI 02852
404-375-2301; Fax: 401-667-7831
Jim Miller, jim.miller@coolpolymers.com
www.coolpolymers.com
ElectronicsCooling
100 Hyde Road, Farmington, CT 06034
860-674-1515; Fax: 860-674-8536
www.ebmpapst.us
March 2011
2011 ElectronicsCooling Buyers’ Guide
Ellsworth Adhesives.................................................
W129 N10825 Washington Drive, Germantown, WI 53022
800-888-0698; Fax: 262-509-8793
info@ellsworth.com; www.ellsworth.com
Elma Electronic Inc....................................................
44350 Grimmer Blvd., Fremont, CA 94538
510-656-3400; Fax: 510-656-3783
sales@elma.com; www.elma.com
Enerdyne Thermal Solutions, Inc..........................
125 W. North Bend Way, PO Box 2660, North Bend, WA 98045
425-888-1880; Fax: 425-831-0773
Chris Macris, info@enerdynesolutions.com
www.enerdynesolutions.com
EXAIR Corporation.....................................................
11510 Goldcoast Drive, Cincinnati, OH 45249-1621
513-671-3322; Fax: 513-671-3363
Bryan Peters, techelp@exair.com; www.exair.com
Extreme Engineering Solutions.............................
3225 Deming Way, Suite 120, Middleton, WI 53562
608-833-1155; Fax: 608-827-6171
sales@xes-inc.com; www.xes-inc.com
F
Fischer Elektronik GmbH & Co. KG.................. 19
Postfach 15 90, D-58465 Ludenscheid, Germany
+49 (0) 23 51 / 4 35-0; Fax: +49 (0) 23 51 / 4 57 54
www.fischerelektronik.de
FLIR Commercial Systems, Inc......................... 13
27700A SW Parkway Ave., Wilsonville, OR 97070
866-477-3687
info@sales.com; www.flir.com
Fujipoly America Corp......................................... 26
900 Milik St., PO Box 119, Carteret, NJ 07008-0119
732-969-0100; Fax: 732-969-3311
Frank Hobler, info@fujipoly.com
www.fujipoly.com
Future Facilities Inc...................................................
2025 Gateway Place, Suite 128, San Jose, CA 95110
408-436-7701; Fax: 408-436-7705
Sherman Ikemoto, sherman.ikemoto@futurefacilities.com
www.futurefacilities.com
H
Heatron, Inc..................................................................
3000 Wilson Ave., Leavenworth, KS 66048
913-651-4420; Fax: 913-651-5352
Tim Falk, TimF@Heatron.com
www.heatron.com
Henkel............................................................................
14000 Jamboree Road, Irvine, CA 92606
714-368-8000; Fax: 714-368-2265
electronics@henkel.com
www.henkel.com/electronics
ITEM Publications...........................................23, 27
1000 Germantown Pike, F-2, Plymouth Meeting, PA 19462
484-688-0300: Fax 484-688-0303
Paul Salotto, psalotto@electronics-cooling.com
www.interferencetechnology.com
L
LCR Electronics...........................................................
9 South Forest Ave., Norristown, PA 19401
610-278-0840; Fax: 610-278-0935
Daemon Heckman, sales@lcr-inc.com
www.lcr-inc.com
Lytron..............................................................................
55 Dragon Court, Woburn, MA 01801
781-933-7300; Fax: 781-935-4529
John Miller, info@lytron.com
www.lytron.com
M
Malico Inc...................................................................5
OptoTherm, Inc............................................................
2591 Wexford-Bayne Road, Suite 304, Sewickley, PA 15143
724-940-7600; Fax: 724-940-7611
Rich Barton, sales@optotherm.com
www.optotherm.com
ORION Fans...................................................................
10557 Metric Drive, Dallas, TX 75243
214-340-0265; Fax: 214-340-5870
sales@knightonline.com
www.orionfans.com
P
Parker Hannifin Corporation...................................
Mechanical Solutions, Inc......................................
Plansee SE....................................................................
MEN Micro, Inc...........................................................
R
215-542-9575; Fax: 215-542-9577
sales@menmicro.com
www.menmicro.com
Radian Heatsinks.......................................................
2785 NW Upshur St., Suite E, Portland, OR 97210
503-313-6594; Fax: 503-384-2965
Kevin O’Connor, ko@MSthermal.com
www.MSthermal.com
24 North Main St., Ambler, PA 19002
Mentor Graphics Coporation............................. 17
Mechanical Analysis Division
300 Nickerson Road, Suite 200, Marlborough, MA 01752
508-480-0881; Fax: 508-480-0882
Sharon Shepard, mad_info@mentor.com
www.mentor.com/mechanical
Mersen...........................................................................
6220 Kestrel Road, Mississauga, Ontario, Canada L5T 1Y9
905-795-0077, ext. 247; Fax: 905-795-2508
sales.mis@mersen.com
www.us-ferrazshawmut.mersen.com/thermal
Minteq International, Inc.........................................
Pyrogenics Group, 640 N. 13th St., Easton, PA 18042
610-250-3398; Fax: 610-250-3321
Mark Breloff, mark.breloff@minteq.com
www.pyrographite.com
N
Nextreme Thermal Solutions.................................
Ice Qube, Inc................................................................
Nidec America Corporation....................................
50 Braintree Hill, Braintree, MA 02184
781-848-0970; Fax: 781-380-3634
Charlie Welsch, charlie.welsch@nidec.com
www.nidec.com
NMB Technologies....................................................
9730 Independence Ave., Chatsworth, CA 91311
Sarah deRosier, sderosier@nmbtc.com
www.nmbtc.com
34 Robinson Road, Clinton, NY 13323
800-4-INDIUM; Fax: 800-221-5759
askus@indium.com
www.indium.com
PO Box 1899, Pleasanton, CA 94566
408-921-9688; Fax: 925-462-0698
Will C., willc@olc-inc.com
www.olc-inc.com
Precision Cooling Systems Division
10801 Rose Ave., New Haven, IN 46774
260-255-5108; Fax: 866-851-0660
Dale Thompson, dale.thompson@parker.com
www.powersystemscooling.com
I
Indium Corporation....................................................
OLC, Inc..........................................................................
No. 5, Ming Lung Road, Yangmei 32663, Taiwan
886-3-4728155, ext. 1616; Fax: 886-3-4725979
inquiry@malico.com.tw
www.malico.com.tw
3908 Patriot Drive, Suite 140, Durham, NC 27703
919-597-7300; Fax: 919-597-7301
info@nextreme.com; www.nextreme.com
141 Wilson Ave., Greensburg, PA 15601
724-837-7600; Fax: 724-837-6365
Tim Mikos, sales@iceqube.com
www.iceqube.com
O
Nuventix, Inc................................................................
4635 Boston Lane, Suite 100m, Austin, TX 78735
512-382-8123; Fax: 512-382-8101
Ryan Ahearn, rahearn@nuventix.com
www.nuventix.com
electronics-cooling.com
10113 Carroll Canyon Road, San Diego, CA 92131
Nicole Peter, nicole.peter@plansee.com
www.plansee-tms.com/index.htm
2160 Walsh Ave., Santa Clara, CA 95050
408-988-6200; Fax: 408-988-0683
Thierry Sin, tsin@radianheatsinks.com
www.radianheatsinks.com
ResinLab........................................................................
W186 N11687 Morse Drive, Germantown, WI 53022
262-502-6610; Fax: 262-253-6919
Terry Stringer, tstringer@ellsworth.com
www.resinlab.com
Rogers Corporation....................................................
Thermal Management Solutions
2225 W. Chandler Blvd., Chandler, AZ 85224
480-917-6137; Fax: 480-917-6119
Mona Fechter, mona.fechter@rogerscorporation.com
www.rogerscorporation.com
S
Schlegel Electronic Materials...............................
806 Linden Ave., Suite 100 (14625), P.O. Box 20310,
Rochester, NY 14602-0310
585-643-2000; Fax: 585-427-7216
schlegelemi.na@schlegelemi.com
www.schlegelemi.com
Seifert Electronic GmbH & Co. KG........................
Egerstrasse 3, 58256 Ennepetal, Germany
+49 2333 79060; Fax: +49 2333 7906144
components@seifert-electronic.de
www.seifert-electronic.de
Sensor Products Inc..................................................
300 Madison Ave., Madison, NJ 07940
973-428-8985; Fax: 973-884-1699
Vadin Shalyt, vshalyt@sensorprod.com
www.sensorprod.com
SEPA EUROPE GmbH.................................................
Weisserlenstrasse 8, D-79108 Freiburg, Germany
+49 761 3842273 0; Fax: +49 761 3842273 99
Robert Cap, info@sepa-europe.com
www.sepa-europe.com
ElectronicsCooling 31
2011 ElectronicsCooling Buyers’ Guide
Singapore Institute of Manufacturing
Technology....................................................................
71 Nanyang Drive, Singapore 638075
+65 6793 8361; Fax: +65 6792 4763
limsuyin@SIMTech.a-star.edu.sg
http://liquidforging.simtech.a-star.edu.sg
SinkPAD Corporation................................................
950 Fee Ana St., Unit-A, Placentia, CA 92870
714-660-2944
Sam Bhayani, enquiry@sinkpad.com
www.sinkpad.com
Spectra-Mat, Inc........................................................
100 Westgate Drive, Watsonville, CA 95076
831-722-4116; Fax: 831-722-4172
Sandra L. Petznick, Sandra_Petznick@saes-group.com
www.thermalmanagementsolutions.com;
www.spectramat.com
T
V
Taica Corporation
Vette Corp.....................................................................
Nisseki Takanawa Bldg 3F, 2-18-10 Takanawa, Minato-ku, Tokyo
108-0074 Japan
81-3-6367-6624; Fax: 81-3-6367-6600
www.taica.co.jp/english/index.html
Temperature@lert......................................................
101 Federal St., 19th Floor, Boston, MA 02110
866-524-3540; Fax: 866-415-9884
Dave Ruede, info@temperaturealert.com;
www.temperaturealert.com
Teseq...............................................................................
52 Mayfield Ave., Edison, NJ 08837
732-225-9533; Fax: 732-225-4789
info@teseq.com; www.teseq.com
Stablcor.........................................................................
17011 Beach Blvd., Suite 900, Huntington Beach, CA 92647
714-375-6644; Fax: 714-375-6699
Don Roy, donroy@stablcor.com
www.Stablcor.com
Staubli Corporation....................................................
201 Parkway West, PO Box 189, Duncan, SC 29334
864-486-5446; Fax: 864-486-5495
www.staubli.com
1395 South Marietta Pkwy, Bldg. 800, Marietta, GA 30067
770-984-0858; Fax: 770-984-0615
Gary Silk, gsilk@stegousa.com
www.stegousa.com
Stockwell Elastomerics, Inc.
4749 Tolbut St., Philadelphia, PA 19136-1512
215-335-3005; Fax: 215-335-9433
Bob Zarr, bzarr@stockwell.com
www.Stockwell.com
Vortec, ITW Air Management..............................9
10125 Carver Road, Cincinnati, OH 45242
800-441-7475; Fax: 513-891-4092
Steve Broerman, sbroerman@itw-air.com
www.vortec.com
W
Thermacore, Inc..........................................................
Waypoint Thermal Management, Inc..................
Thermal Engineering Associates, Inc.................
Wolverine Tube Inc. - MicroCool Division.... 15
780 Eden Road, Lancaster, PA 17601
717-569-6551; Fax: 717-569-8424
Gregg J. Baldassarre, info@thermacore.com;
www.thermacore.com
2915 Copper Road, Santa Clara, CA 95051
650-961-5900; Fax: 650-227-3714
Bernie Siegal, info@thermengr.com; www.thermengr.com
Thermal Solution Resources, LLC.........................
STEGO, Inc....................................................................
14 Manchester Square, Suite 201, Portsmouth, NH 03801
508-804-5509; Fax: 508-203-5905
Donna Michael, dmichael@vettecorp.com
www.vettecorp.com
www.coolcentric.com
91 Point Judith Road, Suite 123, Narragansett, RI 02882
401-515-3269; Fax: 617-391-3057
Mikhail Sagal, info@thermsource.com; www.thermsource.com
Thermal Solutions Inc...............................................
3135 S. State St., Suite 108, Ann Arbor, MI 48108
734-761-1956; Fax: 734-761-9855
geninfo@thermalsoftware.com; www.thermalsoftware.com
Timtronics.....................................................................
150 River Road, Suite I-4A, Montville, NJ 07045
908-672-7362; Fax: 973-257-8999
sales@waypointmanagement.com
www.waypointmanagement.com
200 Clinton Ave, Suite 1000, Huntsville, AL 35801
256-580-3530; Fax: 256-580-3519
Dwight Brown, dwight.brown@wlv.com
www.microcooling.com
Y
Youthen Technology Co., Ltd...................................
Cuihu Road, Chigang Section, Humen Town, DongGuan,
GuangDong, China, 523921
86-769-8161 9568; Fax: 86-769-8161 9598
Jack Zhang, sales@youthentec.com
www.youthentec.cn
35 Old Dock Road, Yaphank, NY 11980
Prakash Khatri, info@timtronics.com; www.timtronics.com
Z
Summit Thermal System Co., Ltd..................... 20
TTM Co., Ltd.................................................................
Zalman Tech Co., Ltd.................................................
Sunon, Inc...................................................................3
U
Shin-lan Sec, Humen Town, Dong Guan, Guang Dong, P.R. China,
523917
86-769-8862-3990; Fax: 86-769-8862-3998
sales@summit.heat-sink.com.tw
www.heat-sink.com.tw
1075 W. Lambert Road, Unit A, Brea, CA 92821
714-255-0208, ext. 1107; Fax: 714-255-0802
David Ku, davidk@sunon.com
www.sunonamerica.com
512 Sameun-ri Jiksan-eup Seobook-gu Cheonan-si
Chungcheongnam-do Korea
82-31-888-9258; Fax: 82-31-888-9268
Sean Choi, sean-choi@coolttm.com; www.coolttm.com
#1007 Daeryung Techno Town III, 448 Gasan-dong,
Gumchun-gu, Seoul, 153-803, Korea
+82-2-2107-3232; Fax: +82-2-2107-3322
Joowhan Kim, zmbtb@zalman.co.kr
www.zalman.co.kr
Universal Air Filter Co...............................................
1624 Sauget Industrial Parkway, Sauget, IL 62206
618-271-7300; Fax: 618-271-8808
Mike Miano, uaf@uaf.com; www.uaf.com
Index of Advertisers
Alpha Novatech�������������������������������������������������Inside Back Cover
Fujipoly America Corp.������������������������������������������������������������������ 26
The Bergquist Company��������������������������������� Inside Front Cover
ITEM Publications.������������������������������������������������������������������� 23, 27
Cofan USA�������������������������������������������������������������������������������������������24
Malico Inc.������������������������������������������������������������������������������������������� 5
DegreeC��������������������������������������������������������������������������������������������� 25
Mentor Graphics Corporation������������������������������������������������������ 17
Delta Products Corp..����������������������������������������������������������������������� 7
SEMI-THERM������������������������������������������������������������������������������������ 11
ebm papst������������������������������������������������������������������������ Back Cover
Summit Thermal System Co., Ltd����������������������������������������������� 20
Electronic Components and Technology Conference ���������21
Sunon, Inc.�������������������������������������������������������������������������������������������� 3
Fischer Elektronik GmbH & Co. KG�������������������������������������������� 19
Vortec, ITW Air Management�������������������������������������������������������� 9
FLIR Commercial Systems, Inc.��������������������������������������������������� 13
Wolverine Tube, Inc.����������������������������������������������������������������������� 15
32 ElectronicsCooling
March 2011
Effect.
Cause.
-79%
When using ebm-papst ACi 4400 axial compact fans
instead of conventional AC fans in control cabinets,
energy costs can be reduced by 79%.
GreenTech stands for climate protection that benefits more than just the environment. Consistent use of ebm-papst fans with EC
technology can radically reduce the power consumption compared to AC fans - and that pays off. In an average sized factory building
with 50 control cabinets and filter fans in continuous operation for example, 6.5 MWh of energy can be saved annually. After only 4-6
months the additional investment will have paid for itself. This reflects our simple yet firm philosophy: Each newly developed product
must exceed the economic and ecological performance of its predecessor. www.ebmpapst.us/greentech
ACi 4400
The engineer’s choice