U.S. patent application number 12/963750 was filed with the patent office on 2011-06-09 for thermoelectric heating/cooling structures including a plurality of spaced apart thermoelectric components.
Invention is credited to Paul Crocco, Philip A. Deane, Ramaswamy Mahadevan, Edward P. Siivola.
Application Number | 20110132000 12/963750 |
Document ID | / |
Family ID | 44080632 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110132000 |
Kind Code |
A1 |
Deane; Philip A. ; et
al. |
June 9, 2011 |
Thermoelectric Heating/Cooling Structures Including a Plurality of
Spaced Apart Thermoelectric Components
Abstract
A thermoelectric heating/cooling structure may include a heat
exchanger and a heat spreader spaced apart from the heat exchanger.
In addition, a plurality of spaced apart thermoelectric components
may be thermally coupled in parallel between the heat exchanger and
the heat spreader. More particularly, each of the thermoelectric
components may include a first header adjacent the heat exchanger,
a second header adjacent the heat spreader, and a plurality of
thermoelectric elements thermally coupled in parallel between the
first and second headers. The first headers of the thermoelectric
components may be spaced apart adjacent the heat exchanger, and the
second headers of the thermoelectric components may be spaced apart
adjacent the heat spreader.
Inventors: |
Deane; Philip A.; (Durham,
NC) ; Siivola; Edward P.; (Raleigh, NC) ;
Crocco; Paul; (Durham, NC) ; Mahadevan;
Ramaswamy; (Chapel Hill, NC) |
Family ID: |
44080632 |
Appl. No.: |
12/963750 |
Filed: |
December 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61285001 |
Dec 9, 2009 |
|
|
|
61327463 |
Apr 23, 2010 |
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Current U.S.
Class: |
62/3.3 |
Current CPC
Class: |
F25B 21/04 20130101;
G01R 31/2874 20130101 |
Class at
Publication: |
62/3.3 |
International
Class: |
F25B 21/04 20060101
F25B021/04 |
Claims
1. A thermoelectric heating/cooling structure comprising: a heat
exchanger; a heat spreader spaced apart from the heat exchanger; a
plurality of spaced apart thermoelectric components thermally
coupled in parallel between the heat exchanger and the heat
spreader, wherein each of the thermoelectric components includes a
first header adjacent the heat exchanger, a second header adjacent
the heat spreader, and a plurality of thermoelectric elements
thermally coupled in parallel between the first and second headers,
wherein the first headers of the thermoelectric components are
spaced apart adjacent the heat exchanger, and wherein the second
headers of the thermoelectric components are spaced apart adjacent
the heat spreader.
2. The thermoelectric heating/cooling structure according to claim
1 further comprising: a low melting temperature metal and/or alloy
thermally coupled between the heat exchanger and each of the first
headers of the respective thermoelectric components and/or between
the heat spreader and each of the second headers of the respective
thermoelectric components.
3. The thermoelectric heating/cooling structure according to claim
2 wherein each of the thermoelectric elements is bonded between the
first and second headers of the respective thermoelectric component
using a solder, wherein the low melting temperature metal and/or
alloy has a melting temperature that is less than a melting
temperature of the solder used to bond the thermoelectric
components.
4. The thermoelectric heating/cooling structure according to claim
2 wherein the low melting temperature metal and/or alloy comprises
gallium-tin.
5. The thermoelectric heating/cooling structure according to claim
2 wherein the low melting temperature metal and/or alloy has a
melting temperature that is lower than an operating temperature of
a surface of the heat exchanger adjacent the thermoelectric
components, wherein the low melting temperature metal and/or alloy
is thermally coupled between the heat exchanger and the first
headers, and wherein the second headers remain solidly bonded to
the heat spreader over operating temperatures of the surface of the
heat spreader.
6. The thermoelectric heating/cooling structure according to claim
1 further comprising: a mechanical stand-off structure between the
heat exchanger and the heat spreader wherein the mechanical
stand-off structure is configured to maintain a gap between the
heat exchanger and the heat spreader.
7. The thermoelectric heating/cooling structure according to claim
1 further comprising: a fluid seal between the heat exchanger and
the heat spreader wherein the fluid seal surrounds the plurality of
thermoelectric components.
8. The thermoelectric heating/cooling structure according to claim
1 wherein the heat exchanger includes a fluid inlet and a fluid
outlet configured to allow heat exchange between a heat exchange
fluid and the heat exchanger.
9. The thermoelectric heating/cooling structure according to claim
1 wherein the heat spreader includes a surface spaced apart from
the plurality of thermoelectric components, wherein the surface is
configured to thermally engage with a device under test.
10. The thermoelectric heating/cooling structure according to claim
9 wherein the plurality of thermoelectric components are configured
to pump heat between device under test and the heat exchanger
through the heat spreader.
11. The thermoelectric heating/cooling structure according to claim
9 further comprising: a servomechanism mechanically coupled to the
heat exchanger and heat spreader, wherein the servomechanism is
configured to position the surface of the heat spreader on the
device under test during test operations and to remove the surface
of the heat spreader from the device under test.
12. The thermoelectric heating/cooling structure according to claim
11 wherein the device under test is electrically and mechanically
coupled to a printed wiring board, the thermoelectric
heating/cooling structure further comprising: a mounting frame
configured to engage portions of the printed wiring board spaced
apart from the device under test when the surface of the heat
spreader is positioned on the device under test.
13. The thermoelectric heating/cooling structure according to claim
12 wherein the mounting frame defines an opening surrounding the
heat spreader so that the mounting frame is spaced apart from the
heat spreader.
14. The thermoelectric heating/cooling structure according to claim
13 further comprising: a resilient mechanical coupling between the
mounting frame and the heat spreader, wherein the resilient
mechanical coupling is configured to allow movement of the heat
spreader relative to the mounting frame.
15. The thermoelectric heating/cooling structure according to claim
14 wherein the resilient mechanical coupling comprises at least one
spring.
16. The thermoelectric heating/cooling structure according to claim
12 wherein the mounting frame is mechanically fixed to the heat
spreader and wherein the mounting frame includes an opening
therethrough to allow thermal contact between the device under test
and the heat spreader.
17. The thermoelectric heating/cooling structure according to claim
16 wherein the mounting frame, the heat spreader, and the heat
exchanger define a sealed enclosure.
18. The thermoelectric heating/cooling structure according to claim
16 wherein the mounting frame comprises a plastic frame.
Description
RELATED APPLICATION
[0001] The present application claims the benefit of priority from
U.S. Provisional Application No. 61/285,001 entitled "Integrating
Thermoelectric (TE) Coolers Into Board Level Test Heads" filed Dec.
9, 2009, and from U.S. Provisional Application No. 61/327,463
entitled "Test Head Design" filed Apr. 23, 2010, the disclosures of
which are hereby incorporated herein in their entireties by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of electronics,
and more particularly, to thermoelectric devices and related
structures, methods, and systems.
BACKGROUND
[0003] Board level functional testing of electronic systems may be
performed over a range of temperatures to insure operation when the
board is assembled into a final product such as a laptop computer.
In order to reduce the duration of board test, localized
temperature control of the device under test (DUT) may be
accomplished using a thermal test head that makes contact with the
device under test. A thermal test head, for example, may be capable
of controlling a temperature of the device under test from 0
degrees C. to 100 degrees C. by providing water as a heat exchange
fluid through a heat exchanger of the device. Performance,
temperature change, and/or temperature range, however, may be
limited in such a device.
SUMMARY
[0004] According to some embodiments of the present invention, a
thermoelectric heating/cooling structure may include a heat
exchanger and a heat spreader spaced apart from the heat exchanger.
In addition, a plurality of spaced apart thermoelectric components
may be thermally coupled in parallel between the heat exchanger and
the heat spreader. More particularly, each of the thermoelectric
components may include a first header adjacent the heat exchanger,
a second header adjacent the heat spreader, and a plurality of
thermoelectric elements thermally coupled in parallel between the
first and second headers. The first headers of the thermoelectric
components may be spaced apart adjacent the heat exchanger, and the
second headers of the thermoelectric components may be spaced apart
adjacent the heat spreader.
[0005] A low melting temperature metal and/or alloy may be
thermally coupled between the heat exchanger and each of the first
headers of the respective thermoelectric components and/or between
the heat spreader and each of the second headers of the respective
thermoelectric components. Each of the thermoelectric elements may
be bonded between the first and second headers of the respective
thermoelectric components using a solder, and the low melting
temperature metal and/or alloy may have a melting temperature that
is less than a melting temperature of the solder used to bond the
thermoelectric components.
[0006] The low melting temperature metal and/or alloy may have a
melting temperature that is lower than an operating temperature of
a surface of the heat exchanger adjacent the thermoelectric
components, and the low melting temperature metal and/or alloy may
be thermally coupled between the heat exchanger and the first
headers. Moreover, the second headers may remain solidly bonded to
the heat spreader over operating temperatures of the surface of the
heat spreader. The low melting temperature metal and/or alloy, for
example, may include a gallium-tin alloy.
[0007] A mechanical stand-off structure may be provided between the
heat exchanger and the heat spreader with the mechanical stand-off
structure being configured to maintain a gap between the heat
exchanger and the heat spreader. In addition, a fluid seal may be
provided between the heat exchanger and the heat spreader with the
fluid seal surrounding the plurality of thermoelectric components.
The heat exchanger may include a fluid inlet and a fluid outlet
configured to allow heat exchange between a heat exchange fluid and
the heat exchanger.
[0008] The heat spreader may include a surface spaced apart from
the plurality of thermoelectric components with the surface being
configured to thermally engage with a device under test. The
plurality of thermoelectric components may thus be configured to
pump heat between the device under test and the heat exchanger
through the heat spreader. Moreover, a servomechanism may be
mechanically coupled to the heat exchanger and heat spreader, and
the servomechanism may be configured to position the surface of the
heat spreader on the device under test during test operations and
to remove the surface of the heat spreader from the device under
test.
[0009] The device under test may be electrically and mechanically
coupled to a printed wiring board, and a mounting frame of the
thermoelectric heating/cooling structure may be configured to
engage portions of the printed wiring board spaced apart from the
device under test when the surface of the heat spreader is
positioned on the device under test. The mounting frame may define
an opening surrounding the heat spreader so that the mounting frame
is spaced apart from the heat spreader. In addition, a resilient
mechanical coupling may be provided between the mounting frame and
the heat spreader, with the resilient mechanical coupling being
configured to allow movement of the heat spreader relative to the
mounting frame. More particularly, the resilient mechanical
coupling may include at least one spring.
[0010] The mounting frame may be mechanically fixed to the heat
spreader, and the mounting frame may include an opening
therethrough to allow thermal contact between the device under test
and the heat spreader. More particularly, the mounting frame, the
heat spreader, and the heat exchanger may define a sealed
enclosure, and/or the mounting frame may be a plastic mounting
frame.
[0011] By using thermoelectric components to pump heat in a thermal
test head having structures discussed herein, improved temperature
control and/or a greater range of temperatures may be provided.
Moreover, by providing a plurality of separate thermoelectric
components between the heat exchanger and the heat spreader
together with thermal couplings to the heat exchanger and/or the
heat spreader that are liquid at operating temperatures thereof,
damage to the thermoelectric components and thermoelectric elements
thereof may be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross sectional view illustrating a
thermoelectric test head according to some embodiments of the
present invention.
[0013] FIG. 2A is a plan view of thermoelectric components on a
heat spreader of FIG. 1 according to some embodiments of the
present invention.
[0014] FIG. 2B is a plan view of thermoelectric components on a
heat spreader of FIG. 1 according to some other embodiments of the
present invention.
[0015] FIG. 3 is a cross sectional view of a thermoelectric
component between a heat exchanger and a heat spreader according to
some embodiments of the present invention.
[0016] FIG. 4 is a plan view of the frame of FIG. 1 according to
some embodiments of the present invention.
[0017] FIG. 5 is a cross sectional view illustrating a
thermoelectric test head according to some other embodiments of the
present invention.
DETAILED DESCRIPTION
[0018] The present invention is described more fully hereinafter
with reference to the accompanying drawings, in which embodiments
of the present invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as
limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey the scope of the present
invention to those skilled in the art. In the drawings, the sizes
and relative sizes of layers and regions may be exaggerated for
clarity. Like numbers refer to like elements throughout.
[0019] It will be understood that when an element or layer is
referred to as being "on", "connected to" or "coupled to" another
element or layer, it can be directly on, connected or coupled to
the other element, or layer or intervening elements or layers may
be present. In contrast, when an element is referred to as being
"directly on," "directly connected to" or "directly coupled to"
another element or layer, there are no intervening elements or
layers present. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed items.
[0020] It will be understood that, although the terms first,
second, third etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another region,
layer or section. Thus, a first element, component, region, layer
or section discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings of the present invention.
[0021] Spatially relative terms, such as "beneath", "below",
"lower", "above", "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly. Also, as used herein,
"lateral" refers to a direction that is substantially orthogonal to
a vertical direction.
[0022] The terminology used herein is for the purpose of describing
particular embodiments only, and is not intended to be limiting of
the present invention. As used herein, the singular forms "a", "an"
and "the" are intended to include the plural forms as well, unless
the context clearly indicates otherwise. It will be further
understood that the terms "comprises" and/or "comprising," when
used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
[0023] Example embodiments of the present invention are described
herein with reference to cross-section illustrations that are
schematic illustrations of idealized embodiments (and intermediate
structures) of the invention. As such, variations from the shapes
of the illustrations as a result, for example, of manufacturing
techniques and/or tolerances, are to be expected. Thus, embodiments
of the present invention should not be construed as limited to the
particular shapes of regions illustrated herein but are to include
deviations in shapes that result, for example, from manufacturing.
For example, a structure illustrated with angular features may
instead have rounded or curved features. Thus, the regions
illustrated in the figures are schematic in nature and their shapes
are not intended to illustrate the actual shape of a region of a
device and are not intended to limit the scope of the present
invention.
[0024] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. Accordingly, these terms can include equivalent
terms that are created after such time. It will be further
understood that terms, such as those defined in commonly used
dictionaries, should be interpreted as having a meaning that is
consistent with their meaning in the present specification and in
the context of the relevant art, and will not be interpreted in an
idealized or overly formal sense unless expressly so defined
herein. All publications, patent applications, patents, and other
references mentioned herein are incorporated by reference in their
entirety.
[0025] FIG. 1 is a cross sectional view illustrating a
thermoelectric test head according to some embodiments of the
present invention. As shown in FIG. 1, a plurality of spaced apart
thermoelectric components T may be thermally coupled in parallel
between heat exchanger 101 and a high thermal conductivity heat
spreader 103. Heat spreader 103, for example, may be formed of a
high thermal conductivity metal and/or ceramic.
[0026] As shown in greater detail in FIG. 3, each thermoelectric
component T may include high thermal conductivity header 301 (e.g.,
a metal and/or ceramic header) adjacent heat exchanger 101, high
thermal conductivity header 303 (e.g., a metal and/or ceramic
header) adjacent heat spreader 303, and a plurality of n-type and
p-type thermoelectric elements N and P thermally coupled in
parallel between first and second headers 301 and 303. Moreover,
headers 301 of each thermoelectric component T may be spaced apart
adjacent heat exchanger 101, and headers 303 of each thermoelectric
component T may be spaced apart adjacent heat spreader 103.
Accordingly, thermoelectric components T may be configured to pump
heat between heat exchanger 101 and heat spreader 103 responsive to
an electrical signal(s) applied thereto.
[0027] Heat exchanger 101 may include a fluid inlet 101a and a
fluid outlet 101b configured to allow heat exchange between a heat
exchange fluid (such as water) and the heat exchanger. By providing
a heat exchange fluid, heat exchanger 101 may better source/sink
heat to/from thermoelectric components T. Accordingly,
thermoelectric components T may be configured to pump heat in a
first direction from DUT 109 to heat exchanger 101 to cool DUT 109,
and to pump heat in a second direction from heat exchanger 101 to
DUT 109 to heat DUT 109. Moreover, heat exchanger 101 may be
mechanically fixed to support member 105 (e.g., using screws, a
permanent adhesive, etc.), and heat spreader 103 may be
mechanically fixed to heat exchanger 101, for example, using screws
107. Accordingly, fixed mechanical couplings may be provided
between heat spreader 103, heat exchanger 101, and support member
105.
[0028] Heat spreader 103 may include a surface spaced apart from
thermoelectric components T, and this surface of heat spreader 103
may be configured to thermally engage with device under test (DUT)
109. DUT 109, for example, may be a printed circuit board having a
plurality of integrated and/or discrete electronic circuits
thereon, or DUT 109 may be an individual integrated circuit on such
a circuit board. Moreover, DUT may be electrically and mechanically
coupled to printed wiring board (PWB) 111 providing electrical and
mechanical connectivity for testing. Accordingly, thermoelectric
components T may be configured to pump heat between DUT 109 and
heat exchanger 101 through heat spreader 103 to provide temperature
control of DUT 109 during functional electrical testing
thereof.
[0029] As shown in FIG. 1, the thermal test head may be mounted to
PWB 111 using positioning screws 115 of servomechanism 116. More
particularly, screws 115 may engage with threaded openings of PWB
111 to raise and lower heat spreader 103 (together with heat
exchanger 101 and support member 105) relative to DUT 109,
Servomechanism 116 may thus be configured to position a surface of
the heat spreader 103 on DUT 109 during test operations (to
thermally engage heat spreader 103 with DUT 109) and to
remove/disengage the surface of heat spreader 103 from DUT 109
after testing. While heat spreader 103 is shown in the raised
position in FIG. 1, it will be understood that servomechanism 116
may be configured to lower heat spreader 103 so that a lower
surface thereof thermally engages an upper surface of DUT 109.
[0030] Servomechanism 116 may thus be configured to lower heat
spreader 103 until thermal contact is provided between heat
spreader 103 and DUT 109. Electrical operations of DUT 109 may then
be activated through PWB 111 to provide electrical/functional
testing of DUT 109 while controlling a temperature of DUT 109 by
pumping heat through heat spreader 103 to raise and/or lower a
temperature of DUT 109 during testing.
[0031] In addition, positioning screws 115 may pass through
mounting frame 117 and mounting frame may be configured to engage
portions of printed wiring board 109 spaced apart from and
surrounding DUT 109 when the surface of heat spreader 103 is
positioned on the device under test. Mounting frame 117 may define
an opening 119 surrounding heat spreader 103 so that mounting frame
117 is spaced apart from heat spreader 103. Opening 119 is further
illustrated in the plan view of mounting frame 119 shown in FIG.
4.
[0032] Resilient mechanical couplings 121 may also be provided
between frame 117 and mounting member 105 to reduce stress on
thermoelectric components T when raising and/or lowering the
thermal test head. The resilient mechanical couplings 121 may thus
be configured to allow movement of heat spreader 103 relative to
mounting frame 117. More particularly, resilient mechanical
couplings 121 may be implemented as springs provided around each of
screws 115 between frame 117 and mounting member 105. While springs
are discussed by way of example, other resilient mechanical
couplings (e.g., compressible rubber bushings around screws 115
between frame 117 and mounting member 105) may be used.
[0033] In addition, a mechanical stand-off structure(s) 123 may be
provided between heat exchanger 101 and heat spreader 103, with
mechanical stand-off structure(s) 123 being configured to maintain
a gap between heat exchanger 101 and heat spreader 103. Mechanical
stand-off structure(2) 123, for example, may surround the
thermoelectric components T as shown in FIG. 2A, or mechanical
stand-off structure(s) 123 may include a plurality of separate
elements 123' spaced around a periphery of thermoelectric
components T as shown in FIG. 2B. According to still other
embodiments of the present invention, mechanical stand-off
structure(s) 123/123' or portions/elements thereof may be provided
between thermoelectric components T. Mechanical stand-off
structure(s) 123 may thus reduce compressive force on
thermoelectric components T between heat exchanger 101 and heat
spreader 103, for example, when heat spreader contacts DUT 109.
[0034] In addition, or in an alternative, a resilient gasket 125
may provide a fluid seal between heat exchanger 101 and heat
spreader 103, with the fluid seal surrounding the plurality of
thermoelectric components T. As shown, screws 107 may pass through
gasket 125, and gasket 125 and mechanical stand-off structure(s)
123/123' may be provided as separate elements. By providing gasket
125 and mechanical stand-off structure 123 as separate elements,
each may be formed of a different material(s) providing higher
performance for their respective functions. Gasket 125, for
example, may be formed of a flexible/resilient material to provide
a better fluid seal, while mechanical stand-off structure 123 may
be formed of a more rigid material that does not allow significant
compression of thermoelectric components T. According to other
embodiments of the present invention, a single structure may
provide both a fluid seal and a mechanical stand-off.
[0035] As shown in greater detail in FIGS. 2A and 2B,
thermoelectric components T may be arranged in an array on heat
spreader 103. By providing a plurality of relatively small
thermoelectric components T (each having its own top and bottom
headers) instead of providing one relative large thermoelectric
component T, damage due to differences of thermal expansion of hot
and cold side headers may be reduced. By providing relatively small
thermoelectric components T with relatively small top and bottom
headers, absolute differences between linear expansion/contraction
of top and bottom headers may be relatively small.
[0036] As shown in FIGS. 1 and 3, each thermoelectric component T
may be mechanically and thermally coupled to heat exchanger 101
using bonding material(s) 131 and mechanically and thermally
coupled to heat spreader 103 using bonding material(s) 133.
Moreover, bonding material 131 and/or 133 may be provided using a
metal and/or alloy (also referred to as a solder) to provide a
solder bond. More particularly, bonding materials 131 and 133 may
be provided using different metals/alloys having different melting
temperatures.
[0037] In particular, one of bonding materials 131 or 133 may be
provided using a low melting temperature metal/alloy (e.g., gallium
tin solder, indium solder, mercury, etc.) having a melting
temperature that is less than an operating temperature of
thermoelectric components T (e.g., a melting temperature less than
50 degrees C., or even less than 30 degrees C.), and the other of
the bonding materials 131 or 133 may be provided using a higher
melting temperature metal/alloy having a melting temperature that
is higher than operating temperatures of thermoelectric components
T (e.g., a melting temperature greater than 100 degrees C., or even
greater than 150 degrees C.). Accordingly, one of the bonding
materials 131 or 133 may be liquid at higher operating temperatures
of thermoelectric components T while the other of the bonding
materials 131 or 133 maintains a solid bond to reduce stress on the
thermoelectric components T as heat exchanger 101 and heat spreader
expand differently (due to differences in temperature) while
maintaining positions of the thermoelectric components T on heat
spreader 103. Even when melted, bonding material 131 may provide a
high thermal conductivity path between thermoelectric components T
and heat exchanger 101. While not shown separately, each bonding
material 131 may including barrier and/or adhesion metals on header
301 and on heat exchanger 101, and solder therebetween. Similarly,
each bonding material 133 may including barrier and/or adhesion
metals on header 303 and on heat spreader 103 and solder
therebetween.
[0038] Accordingly, to some embodiments of the present invention,
the plurality of thermoelectric components T may be soldered to
heat spreader 103 using bonding material 133 having a relatively
high melting temperature before assembly with heat exchanger 101,
servomechanism 116, and/or frame 117. Bonding material 131 having a
relatively low melting temperature (e.g., gallium-tin, indium,
mercury, etc.) may then be provided on exposed surfaces of
thermoelectric components T and/or heat exchanger 101, and heat
spreader 103 may then be fastened to heat exchanger 101. At
increased operating temperatures when differences between thermal
expansions of heat spreader 103 and heat exchanger 101 are
greatest, a high thermal conductivity liquid interface provided by
melted bonding material 131 may reduce shear (lateral strain) of
thermoelectric components T and/or thermoelectric elements thereof.
While bonding material 131 is discussed above as having a low
melting temperature, according to other embodiments of the present
invention, bonding material 133 may have the lower melting
temperature (e.g., less than about 50 degrees C. or even less than
about 30 degrees C.) while bonding material 131 may have the higher
melting temperature (e.g., greater than about 100 degrees C. or
even greater than about 150 degrees C.).
[0039] As shown in greater detail in FIG. 3, each thermoelectric
component T may include a plurality of n-type and p-type
thermoelectric elements N and P thermally coupled in parallel
between headers 301 and 303, and electrically coupled in series
through electrically conductive (e.g., copper) traces 141 and 143.
More particularly, thermoelectric elements N and P may be
electrically and mechanically coupled to electrically conductive
traces 141 and 143 using metal and/or alloy bonding material(s) 151
and 153. Bonding material(s) 151 and 153, for example, may be
provided using a solder(s) having a melting temperature that is
greater than operating temperatures of thermoelectric components T.
More particularly, bonding materials(s) 151 and 153 may have a
melting temperature that is greater than a melting temperature of a
low melting temperature metal/alloy of bonding material 131 or 133
(e.g., greater than about 100 degrees C. or even greater than about
150 degrees C.). Accordingly, a solid mechanical coupling may be
maintained between thermoelectric elements N and P and headers 301
and 303, while a liquid interface is provided between either header
301 and heat exchanger 101 or between header 303 and heat spreader
103. While not shown separately, each bonding material 151 may
include barrier and/or adhesion metals on thermoelectric element
N/P and on trace 141, and solder therebetween. Similarly, each
bonding material 153 may include barrier and/or adhesion metals on
thermoelectric element N/P and on trace 143 and solder
therebetween.
[0040] As shown in FIG. 3, thermoelectric elements N and P and
traces 141 and 143 may be arranged so that current flows in
opposite directions through n-type thermoelectric elements N and
p-type thermoelectric element P to provide a same direction of heat
pumping (either from header 301 to header 303 or from header 303 to
header 301). While not explicitly shown in FIG. 3, thermoelectric
elements N and P and traces 141 and 143 may be arranged in a two
dimensional array on headers 301 and 303. For example, 18 n-type
thermoelectric elements N and 18 p-type thermoelectric elements may
be provided between headers 301 and 303 to provide 18
thermoelectric P-N couples.
[0041] Within a thermoelectric component T, all of the P-N couples
may be electrically coupled in series or groups of the P-N couples
may be electrically coupled in parallel (with couples within a
group being electrically coupled in series). Similarly, all of the
thermoelectric components T (as shown in FIG. 2A, for example) may
be electrically coupled in series, or groups (e.g., rows or
columns) of thermoelectric components T may be electrically coupled
in parallel (with thermoelectric components T in each group being
electrically coupled in series).
[0042] FIG. 5 is a cross sectional view illustrating a
thermoelectric test head according to some other embodiments of the
present invention. The test head of FIG. 5 is similar to that of
FIG. 1 except that frame 117' is mechanically fixed to heat
spreader 103, for example, using screws 107', and frame 117' is
mechanically fixed to support member 105. Thermoelectric components
T may thus be confined within an enclosure 161 defined by support
member 105, frame 117', and heat spreader 103. By providing a fixed
mechanical coupling between heat spreader 103 and frame 117' and
between frame 117' and mounting member 105, a direct mechanical
coupling between heat spreader 103 and heat exchanger 101 (e.g.,
using screws 107 of FIG. 1) may be omitted. Accordingly a liquid
interface between thermoelectric components T and heat exchanger
101 or heat spreader 103 may be allowed to reduce stresses on
thermoelectric components T due to different thermal expansions of
heat exchanger 101 and heat spreader 103.
[0043] Moreover, enclosure 161 defined by support member 105, frame
117', and heat spreader 103 may provide sufficient fluid sealing so
that a separate gasket 125 between heat exchanger 101 and heat
spreader 103 may be omitted. While not shown in FIG. 5, sealing
elements (e.g., gaskets) may be provided between frame 117' and
heat spreader 103 and/or between frame 117' and support member
105.
[0044] In the embodiment of FIG. 5, Frame 117' may be formed of a
material, such as plastic, having a relatively low coefficient of
thermal expansion. Moreover, a compressive force applied to
thermoelectric components T may be reduced and/or controlled by
coupling heat spreader 103 to frame 117'. Stated in other words,
compressive forces (when heat spreader 103 is brought into contact
with DUT 109) may be translated from heat spreader 103 through
frame 117' to support member 105 instead of translating such
compressive forces directly through thermoelectric components
T.
[0045] Because frame 117' may be in direct contact with heat
spreader 103, frame 117' may be provided using a thermally
insulating material, such as plastic, or portions of frame 117' in
direct contact with heat spreader 103 may be provided using a
thermally insulating material. According to some other embodiments
of the present invention, a thermally insulating layer/gasket may
be provided between frame 117' and heat spreader 103.
[0046] As shown in FIG. 5, an opening 119' through frame 117' may
allow thermal contact between heat spreader 103 and DUT 109.
Dimensions of opening 119', however, may be less than dimensions of
heat spreader 103 to allow mechanical coupling therebetween and/or
to provide a fluid seal therebetween.
[0047] As discussed above with respect to FIG. 1, bonding material
131 or bonding material 133 may be liquid at an operating
temperature of the thermoelectric components T to reduce stress
resulting from different thermal expansions of heat exchanger 101
and heat spreader 103. Moreover, mechanical stand-off structure(s)
123 may maintain a desired spacing between heat exchanger 101 and
heat spreader 103 even when bonding material 131 or bonding
material 133 melts during operation. In thermoelectric components T
of FIGS. 1, 3, and 5, heat may be pumped from header 301 to header
303 (and thus from heat exchanger 101 to heat spreader 103)
responsive to a current through serially coupled p-type and n-type
thermoelectric elements P and N thereby heating DUT 109 that is
thermally coupled to heat spreader 103. By reversing the current,
heat may be pumped from header 303 to header 301 (and thus from
heat spreader 103 to heat exchanger 101) responsive to the reversed
current thereby cooling DUT 109 that is thermally coupled to heat
spreader 103. Thermoelectric structures are discussed, for example,
in U.S. Publication Nos. 20060289052 (entitled "Methods Of Forming
Thermoelectric Devices Including Conductive Posts And/Or Different
Solder Materials And Related Methods And Structures"), 20060289050
(entitled "Methods Of Forming Thermoelectric Devices Including
Electrically Insulating Matrixes Between Conductive Traces And
Related Structures"), 20060086118 (entitled "Thin Film
Thermoelectric Devices For Hot-Spot Thermal Management In
Microprocessors And Other Electronics"), 20060289052 (entitled
"Methods Of Forming Thermoelectric Devices Including Conductive
Posts And/Or Different Solder Materials And Related Methods And
Structures"), 20070089773 (entitled "Methods Of Forming Embedded
Thermoelectric Coolers With Adjacent Thermally Conductive Fields
And Related Structures"), 20070215194 (entitled "Methods Of Forming
Thermoelectric Devices Using Islands Of Thermoelectric Material And
Related Structures"), 20090000652 (entitled "Thermoelectric
Structures Including Bridging Thermoelectric Elements"), and
2009/0072385 (entitled "Electronic Assemblies Providing Active Side
Heat Pumping And Related Methods And Structures"), the disclosures
of which are hereby incorporated herein in their entirety by
reference.
[0048] P-type and N-type thermoelectric elements N and P may be
provided using semiconductor thin-film deposition techniques, and
thermoelectric components T may be fabricated using
micro-fabrication techniques. In such thermoelectric components T,
a plurality of P and N type thermoelectric elements may be
electrically coupled in series (with the series connections
alternating between P-type and N-type thermoelectric elements) and
thermally coupled in parallel between thermally conductive headers
301 and 303. For example, thin-films of P-type and N-type
thermoelectric materials (e.g., bismuth telluride or
Bi.sub.2Te.sub.3) may be epitaxially grown on respective substrates
and then diced to provide substantially single crystal P-type and
N-type thermoelectric elements N and P that are then soldered to
respective conductive traces 141 and 143 on header 301 and 303. In
an alternative, thermoelectric elements may be provided using bulk
(e.g., thicker and non-crystalline) thermoelectric materials.
[0049] By using thin-film substantially single crystal
thermoelectric elements N and P, a size of a thermoelectric module
may be reduced and performance may be improved. Bulk thermoelectric
devices, for example, may be limited to about 10 W/cm.sup.2. Use of
thin-film substantially single crystal thermoelectric elements,
however, may allow heat pumping capacities of 100 W/cm.sup.2 or
higher. Accordingly, substantially single crystal and/or thin film
thermoelectric elements N and P may provide dramatically higher
performance than conventional bulk thermoelectric elements, and
structures of FIGS. 1-5 may facilitate use of such high performance
thermoelectric elements in a test head requiring repeated contact
with DUTs without damaging the thermoelectric
elements/components.
[0050] While the present invention has been particularly shown and
described with reference to embodiments thereof, it will be
understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
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