U.S. patent application number 13/111735 was filed with the patent office on 2012-11-22 for thermal interface materials and methods for processing the same.
This patent application is currently assigned to LAIRD TECHNOLOGIES, INC.. Invention is credited to Karen Bruzda, Michael D. Craig, Richard F. Hill, Brian Jones.
Application Number | 20120292005 13/111735 |
Document ID | / |
Family ID | 47174063 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120292005 |
Kind Code |
A1 |
Bruzda; Karen ; et
al. |
November 22, 2012 |
THERMAL INTERFACE MATERIALS AND METHODS FOR PROCESSING THE SAME
Abstract
A thermal interface material is provided for use to fill a gap
between surfaces in a thermal transfer system to transfer heat
between the surfaces. The thermal interface material includes a
base material and thermally conductive particles dispersed within
the base material. The thermal interface material is conditioned
under reduced pressure (e.g., prior to being placed in the gap
between the surfaces, while being placed in the gap, after being
placed in the gap, etc.) and, within about forty-eight hours or
less of conditioning, the conditioned thermal interface material is
either positioned in a container that inhibits ambient gas from
contacting it (either alone or applied to the surfaces), or used to
transfer heat between the surfaces. As such, the thermal interface
material is substantially free of cracks following exposure to
thermal cycling comprising a temperature change of at least about
100 degrees Celsius for at least about 10 cycles.
Inventors: |
Bruzda; Karen; (Cleveland,
OH) ; Hill; Richard F.; (Parkman, OH) ; Jones;
Brian; (Warren, OH) ; Craig; Michael D.;
(Painesville, OH) |
Assignee: |
LAIRD TECHNOLOGIES, INC.
Chesterfield
MO
|
Family ID: |
47174063 |
Appl. No.: |
13/111735 |
Filed: |
May 19, 2011 |
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
F28F 13/00 20130101;
H01L 2924/0002 20130101; F28F 2255/00 20130101; F28F 2013/006
20130101; H01L 2924/00 20130101; H01L 23/3737 20130101; H01L 23/42
20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Claims
1-29. (canceled)
30. A thermal interface material suitable for use to fill a gap
between at least two surfaces to transfer heat between the at least
two surfaces, the thermal interface material comprising: a base
material; and thermally conductive particles dispersed within the
base material; wherein the thermal interface material is
conditioned and/or subjected to reduced pressure, whereby
operational reliability and/or resistance to crack formation during
thermal cycling is improved for the thermal interface material.
31. The thermal interface material of claim 30, wherein the thermal
interface material is conditioned under reduced pressure less than
ambient air pressure.
32. The thermal interface material of claim 30, wherein the thermal
interface is conditioned under reduced pressure between about 0.01
Torr and about 750 Torr.
33. The thermal interface material of claim 30, wherein: at a first
time period, the thermal interface material is substantially free
of cracks following exposure of the thermal interface material to
thermal cycling between a temperature of about -20 degrees Celsius
and a temperature of about 160 degrees Celsius for at least about
10 cycles during use of the thermal interface material to fill a
gap between at least two surfaces; and at a second time period,
after exposure of the thermal interface material to ambient air for
at least about eight hours, the thermal interface material exhibits
crack formation following exposure of the thermal interface
material to thermal cycling between a temperature of about -20
degrees Celsius and a temperature of about 160 degrees Celsius for
at least about 10 cycles during use of the thermal interface
material to fill a gap between at least two surfaces.
34. The thermal interface material of claim 30, wherein: the
thermal interface material is conditioned under reduced pressure
prior to use of the thermal interface material to fill the gap
between the at least two surfaces to transfer heat between the at
least two surfaces; or the thermal interface material is
conditioned under reduced pressure during use of the thermal
interface material to fill the gap between the at least two
surfaces to transfer heat between the at least two surfaces; or the
thermal interface material is conditioned under reduced pressure
prior to, during, or after positioning of the thermal interface
material to fill the gap between at least two surfaces to transfer
heat between the at least two surfaces.
35. The thermal interface material of claim 30, wherein the thermal
interface material is either a thermally conductive putty, a
thermally conductive grease, or a thermally conductive gap pad.
36. The thermal interface material of claim 30, wherein the thermal
interface material has been conditioned under reduced pressure,
whereby within about forty-eight hours or less of conditioning the
thermal interface material, the conditioned thermal interface
material is either positioned in a container that inhibits ambient
gas from contacting the conditioned thermal interface material or
used to transfer heat between at least two thermal transfer
surfaces in a thermal transfer system.
37. The thermal interface material of claim 36, wherein within
about twelve hours or less of conditioning the thermal interface
material, the conditioned thermal interface material is either
positioned in the container that inhibits ambient gas from
contacting the conditioned thermal interface material or used to
transfer heat between the at least two thermal transfer surfaces in
the thermal transfer system.
38. The thermal interface material of claim 30, wherein the thermal
interface material is in a container that inhibits ambient gas from
contacting the thermal interface material.
39. The thermal interface material of claim 38, wherein the thermal
interface material is conditioned under reduced pressure while in
the container.
40. A method for processing a thermal interface material to improve
operational reliability of the thermal interface material when used
to transfer heat between at least two thermal transfer surfaces,
the method comprising conditioning the thermal interface material
by subjecting the thermal interface material to reduced
pressure.
41. The method of claim 40, wherein conditioning the thermal
interface material includes subjecting the thermal interface
material to a vacuum of at least about 127 Torr to reduce pressure
around the thermal interface material.
42. The method of claim 41, wherein subjecting the thermal
interface material to a vacuum of at least about 127 Torr includes
subjecting the thermal interface material to a vacuum of at least
about 127 Torr for at least about 5 minutes.
43. The method of claim 40, wherein conditioning the thermal
interface material includes conditioning the thermal interface
material includes reducing pressure around the thermal interface
material to a pressure below ambient air pressure.
44. The method of claim 40, wherein conditioning the thermal
interface material includes conditioning the thermal interface
material includes reducing pressure around the thermal interface
material to between about 0.01 Torr and about 750 Torr.
45. The method of claim 40, wherein conditioning the thermal
interface material improves operational reliability and/or
resistance to crack formation of the thermal interface material
during thermal cycling.
46. The method of claim 40, wherein the thermal interface material
is substantially free of cracks following exposure to thermal
cycling comprising a temperature change of at least about 100
degrees Celsius for at least about 10 cycles.
47. The method of claim 40, wherein the thermal interface material
is substantially free of cracks following exposure to thermal
cycling comprising a temperature change of at least about 100
degrees Celsius for at least about 10 cycles during use of the
thermal interface material to transfer heat between at least two
thermal transfer surfaces.
48. The method of claim 40, further comprising inhibiting ambient
gas from contacting the conditioned thermal interface material
within about forty-eight hours or less of conditioning the thermal
interface material.
49. The method of claim 40, further comprising inhibiting ambient
gas from contacting the conditioned thermal interface material
within about twelve hours or less of conditioning the thermal
interface material.
50. The method of claim 49, wherein inhibiting ambient gas from
contacting the conditioned thermal interface material includes
sealing the conditioned thermal interface material in a
container.
51. The method of claim 40, further comprising packaging the
conditioned thermal interface material in a container configured to
inhibit ambient gas from contacting the conditioned thermal
interface material.
52. The method of claim 51, further comprising shipping the thermal
interface material in the container to an end user.
53. The method of claim 40, further comprising using the
conditioned thermal interface material to transfer heat between at
least two thermal transfer surfaces in a thermal transfer system
within about forty-eight hours or less of conditioning the thermal
interface material.
54. The method of claim 40, further comprising using the
conditioned thermal interface material to transfer heat between at
least two thermal transfer surfaces in a thermal transfer system
within about twelve hours or less of conditioning the thermal
interface material.
55. The method of claim 40, wherein conditioning the thermal
interface material by subjecting the thermal interface material to
reduced pressure comprises removing entrained gas from the thermal
interface material.
56. The method of claim 40, further comprising installing the
thermal interface material to a thermal transfer system, and
wherein conditioning the thermal interface material by subjecting
the thermal interface material to reduced pressure includes:
conditioning the thermal interface material prior to installing the
thermal interface material to the thermal transfer system; or
conditioning the thermal interface material while installing the
thermal interface material to the thermal transfer system; or
conditioning the thermal interface material after installing the
thermal interface material to the thermal transfer system.
57. A thermal interface material processed in accordance with the
method of claim 40.
58. A thermal interface material suitable for use to fill a gap
between at least two surfaces to transfer heat between the at least
two surfaces, the thermal interface material comprising: a base
material; and thermally conductive particles dispersed within the
base material; wherein the thermal interface material is
conditioned under reduced pressure; and/or wherein the thermal
interface material is configured such that: at a first time period,
the thermal interface material will be substantially free of cracks
following exposure of the thermal interface material to thermal
cycling between a temperature of about -20 degrees Celsius and a
temperature of about 160 degrees Celsius for at least about 10
cycles during use of the thermal interface material to fill a gap
between at least two surfaces; and at a second time period, after
exposure of the thermal interface material to ambient air for at
least about eight hours, the thermal interface material will
exhibit crack formation following exposure of the thermal interface
material to thermal cycling between a temperature of about -20
degrees Celsius and a temperature of about 160 degrees Celsius for
at least about 10 cycles during use of the thermal interface
material to fill a gap between at least two surfaces.
Description
FIELD
[0001] The present disclosure generally relates to thermal
interface materials conditioned under reduced pressure, for
example, reduced atmospheric pressure, etc., and methods for
conditioning the thermal interface materials. Such conditioning of
the thermal interface materials can be done prior to packaging the
thermal interface materials; prior to, while, or after installing
the thermal interface materials in thermal transfer systems; prior
to or while using the thermal interface materials to transfer heat
between thermal transfer surfaces in thermal transfer systems;
etc.
BACKGROUND
[0002] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0003] Electrical components, such as semiconductors, integrated
circuit packages, transistors, etc., typically have pre-designed
temperatures at which the electrical components optimally operate.
Ideally, the pre-designed temperatures approximate the temperature
of the surrounding air. But the operation of electrical components
generates heat. If the heat is not removed, the electrical
components may then operate at temperatures significantly higher
than their normal or desirable operating temperatures. Such
excessive temperatures may adversely affect the operating
characteristics of the electrical components and the operation of
the associated devices.
[0004] To avoid or at least reduce the adverse operating
characteristics from the heat generation, the heat should be
removed, for example, by conducting the heat from the operating
electrical components to heat sinks. The heat sinks may then be
cooled by conventional convection and/or radiation techniques.
During conduction, the heat may pass from the operating electrical
components to the heat sinks either by direct surface contact
between the electrical components and heat sinks and/or by contact
of the electrical components and heat sink surfaces through
intermediate mediums or thermal interface materials. The thermal
interface materials may be used to fill gaps between thermal
transfer surfaces, in order to increase thermal transfer
efficiency, as compared to having the gaps filled with air, which
is a relatively poor thermal conductor.
SUMMARY
[0005] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0006] Disclosed herein are example embodiments of systems and
methods relating to processing thermal interface materials for
improving reliability, operability, etc. of the thermal interface
materials when used with thermal transfer systems (e.g., to
transfer heat between thermal transfer surfaces of the systems,
etc.) to thereby improve reliability, operability, etc. of the
thermal transfer systems during such use, particularly when the
thermal transfer systems undergo cyclic changes in temperature
during such use. Also disclosed are example embodiments of thermal
interface materials that have been processed in accord with the
present disclosure, including thermal interface materials that have
been conditioned under reduced pressure. In such embodiments,
conditioning of the thermal interface materials can be done prior
to, while, or after installing the thermal interface materials
between thermal transfer surfaces in thermal transfer systems, or
even prior to or while using the thermal interface materials to
transfer heat between the thermal transfer surfaces in the thermal
transfer systems. In some example embodiments, the conditioned
thermal interface materials (e.g., separate from thermal transfer
systems, installed in the thermal transfer systems, etc.) may be
further packaged and/or stored (e.g., alone, in combination with
the thermal transfer systems in which they are installed, etc.)
under conditions so as to inhibit contact of the conditioned
thermal interface materials with ambient gases.
[0007] Example embodiments of the present disclosure are generally
directed toward thermal interface materials suitable for use to
fill gaps between surfaces and/or transfer heat between the
surfaces (e.g., in thermal transfer systems, etc.). In one example
embodiment, a thermal interface material generally includes a base
material and thermally conductive particles dispersed within the
base material. At a first time period, the thermal interface
material is substantially free of cracks following exposure of the
thermal interface material to thermal cycling between a temperature
of about -20 degrees Celsius and a temperature of about 160 degrees
Celsius for at least about 10 cycles during use of the thermal
interface material to fill a gap between at least two surfaces. At
a second time period, after exposure of the thermal interface
material to ambient air for at least about eight hours, the thermal
interface material exhibits crack formation following exposure of
the thermal interface material to thermal cycling between a
temperature of about -20 degrees Celsius and a temperature of about
160 degrees Celsius for at least about 10 cycles during use of the
thermal interface material to fill a gap between at least two
surfaces.
[0008] In another example embodiment, a thermal interface material
generally includes a base material and thermally conductive
particles dispersed within the base material. Here, the thermal
interface material is conditioned under reduced pressure and,
within about forty-eight hours or less of conditioning the thermal
interface material, the conditioned thermal interface material is
either positioned in a container that inhibits ambient gas from
contacting the conditioned thermal interface material, or the
thermal interface material is used to transfer heat between thermal
transfer surfaces of a thermal transfer system. In this example
embodiment, the thermal interface material can be conditioned prior
to, while, or after installing the thermal interface material in
the thermal transfer system. Or, the thermal interface material
could be conditioned at anytime prior to or while using the thermal
interface material to transfer heat between the thermal transfer
surfaces of the thermal transfer system.
[0009] Example embodiments of the present disclosure also generally
relate to methods for processing thermal interface materials to
improve operational reliability of the thermal interface materials
when used to transfer heat between at least two thermal transfer
surfaces. In one example embodiment, a method generally includes
conditioning the thermal interface material under reduced pressure
such that the thermal interface material is substantially free of
cracks following exposure to thermal cycling comprising a
temperature change of at least about 100 degrees Celsius for at
least about 10 cycles.
[0010] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0011] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0012] FIG. 1 is a flowchart illustrating operations of an example
method for processing a thermal interface material in accordance
with the present disclosure;
[0013] FIG. 2 is a perspective view of an example system operable
to help process a thermal interface material in accordance with the
present disclosure;
[0014] FIG. 3 is a photograph of a sample of a thermally conductive
putty initially exposed to ambient laboratory conditions for about
24 hours and then submerged in degassed liquid silicone under
reduced pressure in a vacuum chamber, and shown in the vacuum
chamber in the degassed liquid silicone at about a time a reduced
pressure of about 127 Torr (about 5 inches of mercury absolute
(inHg abs)) was achieved in the vacuum chamber;
[0015] FIG. 4 is a photograph of a sample of the same thermally
conductive putty of FIG. 3 conditioned at a reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes in
accordance with the present disclosure and then submerged in
degassed liquid silicone under reduced pressure in a vacuum
chamber, and shown in the vacuum chamber in the degassed liquid
silicone at about a time a reduced pressure of about 127 Torr
(about 5 inHg abs) was achieved in the vacuum chamber;
[0016] FIG. 5 is a photograph of a sample of the same thermally
conductive putty of FIG. 3 conditioned at a reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes in
accordance with the present disclosure, then exposed to ambient
laboratory conditions for about 12 hours, and then submerged in
degassed liquid silicone under reduced pressure in a vacuum
chamber, and shown in the vacuum chamber in the degassed liquid
silicone at about a time a reduced pressure of about 127 Torr
(about 5 inHg abs) was achieved in the vacuum chamber;
[0017] FIG. 6 is a photograph of a sample of the same thermally
conductive putty of FIG. 3 conditioned at a reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes in
accordance with the present disclosure, then stored in a sealed bag
under vacuum for about 1 month, and then submerged in degassed
liquid silicone under reduced pressure in a vacuum chamber, and
shown in the vacuum chamber in the degassed liquid silicone at
about a time a reduced pressure of about 127 Torr (about 5 inHg
abs) was achieved in the vacuum chamber;
[0018] FIG. 7 is a photograph of a sample of a thermally conductive
putty conditioned at a reduced pressure of about 381 Torr (about 15
inHg abs) for about 5 minutes in accordance with the present
disclosure and then subjected to thermal cycling analysis;
[0019] FIG. 8 is a photograph of a sample of the same thermally
conductive putty of FIG. 7 not conditioned at a reduced pressure
and subjected to the same thermal cycling analysis as the sample
shown in FIG. 7;
[0020] FIG. 9 is a photograph of a sample of a thermally conductive
putty conditioned at a reduced pressure of about 381 Torr (about 15
inHg abs) for about 5 minutes in accordance with the present
disclosure and then subjected to thermal cycling analysis;
[0021] FIG. 10 is a photograph of a sample of the same thermally
conductive putty of FIG. 9 not conditioned at a reduced pressure
and subjected to the same thermal cycling analysis as the sample
shown in FIG. 9;
[0022] FIG. 11 is a photograph of a sample of a thermally
conductive putty conditioned at a reduced pressure of about 381
Torr (about 15 inHg abs) for about 5 minutes in accordance with the
present disclosure and then subjected to thermal cycling
analysis;
[0023] FIG. 12 is a photograph of a sample of the same thermally
conductive putty of FIG. 11 not conditioned at a reduced pressure
and subjected to the same thermal cycling analysis as the sample
shown in FIG. 11;
[0024] FIG. 13 is a photograph of a sample of a thermally
conductive grease conditioned at a reduced pressure of about 381
Torr (about 15 inHg abs) for about 5 minutes in accordance with the
present disclosure and then subjected to thermal cycling
analysis;
[0025] FIG. 14 is a photograph of a sample of the same thermally
conductive grease of FIG. 13 not conditioned at a reduced pressure
and subjected to the same thermal cycling analysis as the sample
shown in FIG. 13;
[0026] FIG. 15 is a photograph of a sample of a thermally
conductive putty exposed to ambient laboratory conditions for about
24 hours and then subjected to thermal cycling analysis;
[0027] FIG. 16 is a photograph of a sample of the same thermally
conductive putty of FIG. 15 conditioned at a reduced pressure of
about 5 inHg abs for about 15 minutes in accordance with the
present disclosure and then subjected to thermal cycling
analysis;
[0028] FIG. 17 is a photograph of a sample of the same thermally
conductive putty of FIG. 15 conditioned at a reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes in
accordance with the present disclosure, then exposed to ambient
laboratory conditions for about 24 hours, and then subjected to
thermal cycling analysis; and
[0029] FIG. 18 is a photograph of a sample of the same thermally
conductive putty of FIG. 15 conditioned at a reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes in
accordance with the present disclosure, then packaged in a sealed
container under vacuum for about 1 month, and then subjected to
thermal cycling analysis.
[0030] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0031] The following description is merely example in nature and is
in no way intended to limit the present disclosure, application, or
uses.
[0032] Thermal interface materials may be used to fill gaps between
thermal transfer surfaces in thermal transfer systems (e.g.,
between surfaces of heat generating components (e.g., electronic
devices, hot water devices, etc.) and surfaces of heat removing
components (e.g., heat sinks, etc.), etc.) in order to increase
thermal transfer efficiency between the surfaces, as compared to
having the gaps filled with air which is a relatively poor thermal
conductor. The thermal interface materials generally include base
materials (e.g., silicone-based base materials, etc.) and thermally
conductive particles (e.g., ceramic particles, etc.) dispersed
(e.g., provided, located, etc.) within the base materials.
Thermally conductive putties, thermally conductive greases, and
thermal gap pads are example types of thermal interface materials
that can be used to fill such gaps between thermal transfer
surfaces.
[0033] As recognized by the inventors hereof some thermal interface
materials may suffer from reliability issues when subjected to
thermal cycling at temperatures above, for example, about 65
degrees Celsius (e.g., when the thermal interface materials are
used in connection with heat generating components that are
cyclically turned on and off and that cyclically heat to
temperatures above about 65 degrees Celsius and then cool, etc.).
For example, during use between surfaces cracks may form in the
thermal interface materials, and/or the thermal interface materials
may pump out of the gaps between the thermal transfer surfaces
(leaving voids in the thermal interface materials). This in turn
can decrease thermal transfer between the thermal transfer surfaces
because the air filling the cracks and/or voids will have a lower
thermal conductivity than the thermal interface materials.
[0034] As an example, the inventors hereof have recognized that
cracks sometimes form in thermal interface materials when used in
applications that undergo such cyclic changes in temperature (e.g.,
when used to fill gaps between thermal transfer surfaces, etc.).
Without being bound by theory, the inventors hereof hypothesize
that such cracks are caused by movement of gas (e.g., air, etc.)
entrained within the thermal interface materials. Temperature
changes in the thermal interface materials cause the entrained gas
(along with the actual matrices of the thermal interface materials)
to expand and contract and thus move within the thermal interface
materials. Over time, the gas migrates and collects, and forms weak
points within the thermal interface materials at which the cracks
(or fissures) form (e.g., due to internal stresses, etc.).
[0035] The inventors hereof have unexpectedly discovered that
subjecting thermal interface materials to reduced pressure
conditioning (e.g., removing entrained gas from the thermal
interface materials, reducing an amount of entrained gas in the
thermal interface materials, etc.) within a specific time frame
before storing, shipping, using, etc. the thermal interface
materials can help improve operational reliability (e.g.,
consistency of thermal transfer between thermal transfer surfaces,
etc.) of the thermal interface materials (as compared to the same
thermal interface materials not similarly conditioned). Such
conditioning can be done, for example, prior to, while, or after
installing the thermal interface materials in thermal transfer
systems (e.g., prior to, while, or after positioning the thermal
interface material in gaps between the thermal transfer surfaces in
the thermal transfer systems, etc.), or even prior to or while
using the thermal interface materials to transfer heat between
thermal transfer surfaces of the thermal transfer systems.
[0036] For example, the inventors hereof have found that subjecting
thermal interface materials to reduced pressure conditioning (e.g.,
bulk supplies of the thermal interface materials, etc.)
substantially reduces formation of cracks in the thermal interface
materials when used to transfer heat between thermal transfer
surfaces in applications that undergo cyclic changes in temperature
(thus improving operational reliability of the thermal interface
materials as previously described). In particular, the inventors
hereof have found that using the thermal interface materials (e.g.,
to transfer heat between the thermal transfer surfaces, etc.)
within about 48 hours or less (e.g., within about 24 hours or less,
within about 12 hours or less, within about 8 hours or less, etc.)
after subjecting the thermal interface materials to reduced
pressure conditioning substantially reduces formation of cracks in
the thermal interface materials during such use of the thermal
interface materials. The inventors hereof have also found that
further storing the conditioned thermal interface materials (e.g.,
alone, already applied to thermal transfer surfaces, etc.) under
conditions that inhibit the thermal interface materials from coming
into contact with ambient gas (e.g., in sealed containers, under
reduced pressure, etc.) after subjecting the thermal interface
materials to reduced pressure conditioning, and then later using
the stored thermal interface materials (e.g., to transfer heat
between thermal transfer surfaces, etc.), also substantially
reduces formation of cracks in the thermal interface materials when
exposed to cyclic changes in temperature during such use.
[0037] In addition, the inventors hereof have found that such
benefits associated with subjecting thermal interface materials to
reduced pressure conditioning (e.g., reduction in crack formation,
improved operational reliability, etc.) are reversible over time,
and in fact disappear if the conditioned thermal interface
materials are subsequently exposed to ambient gas for a period of
time (e.g., for about 8 hours or more, etc.) before being used
(e.g., to transfer heat between thermal transfer surfaces, etc.) or
being stored as described herein. But the inventors hereof have
found that such benefits can be re-achieved by subsequently
subjecting the thermal interface materials to reduced pressure
conditioning within a specific time frame before the thermal
interface materials are used. As such, the inventors hereof have
found that operations for reduced pressure conditioning the thermal
interface materials can be applied repeatedly to the thermal
interface materials to indefinitely maintain such benefits. Such
reconditioning can be done, for example, prior to, while, or after
installing the thermal interface material in thermal transfer
systems, or even while using the thermal interface materials to
transfer heat between thermal transfer surfaces of the thermal
transfer systems.
[0038] Example embodiments of the present disclosure thus relate to
thermal interface materials (e.g., bulk supplies of the thermal
interface materials, etc.) subjected to reduced pressure
conditioning within a specific time frame of being used (e.g., used
to transfer heat between thermal transfer surfaces, etc.), as well
as to methods for subjecting the thermal interface materials to
reduced pressure conditioning and systems for subjecting the
thermal interface materials to reduced pressure conditioning (e.g.,
in preparation for use, etc.). For example, some example
embodiments include conditioning thermal interface materials by
subjecting the thermal interface materials (e.g., alone, already
applied to thermal transfer surfaces, etc.) to reduced pressure and
then using the thermal interface materials, for example, to
transfer heat between thermal transfer surfaces in thermal transfer
systems, etc. Such conditioning can be done, for example, prior to,
while, or after installing the thermal interface material in
thermal transfer systems (e.g., prior to, while, or after
positioning the thermal interface material in gaps between the
thermal transfer surfaces, etc.), or even prior to or while using
the thermal interface materials to transfer heat between thermal
transfer surfaces of the thermal transfer systems. Some example
embodiments further include packaging the conditioned thermal
interface materials (e.g., alone, already applied to thermal
transfer surfaces, etc.) in containers (e.g., sealed containers,
etc.) under conditions that inhibit contact of the thermal
interface materials with ambient gases, and maintaining the thermal
interface materials in the containers under such conditions as
desired (e.g., until the thermal interface materials are to be
used, during storage of the thermal interface materials, during
transport of the thermal interface materials, etc.) to thereby
improve operational reliability of the thermal interface materials
when unsealed and used by end users.
[0039] Example embodiments will now be described more fully with
reference to the accompanying drawings.
[0040] FIG. 1 illustrates a flowchart of an example method 100 for
use in processing a thermal interface material (e.g., a bulk supply
of the thermal interface material, etc.) in accordance with the
present disclosure. Such processing can help inhibit formation of
cracks and/or help improve operational reliability of the thermal
interface material, for example, when used to transfer heat between
thermal transfer surfaces of components in thermal transfer devices
that undergo cyclic changes in temperature. The example method 100
is described in connection with processing a thermal interface
material prior to installing the thermal interface material in a
thermal transfer system. However, it should be appreciated that the
example method 100 is also applicable to processing a thermal
interface material while installing it into a thermal transfer
system as well as to processing a thermal interface material after
it is already installed to a thermal transfer system.
[0041] The illustrated method 100 generally includes an operation
102 of conditioning the thermal interface material by subjecting
the thermal interface material to reduced pressure, and an
operation 104 of inhibiting ambient gas from contacting the
conditioned thermal interface material, for example, prior to using
the thermal interface material in the thermal transfer system. The
method 100 may be applied to any size and/or quantity of thermal
interface materials (e.g., bulk quantities of thermal interface
materials, etc.).
[0042] In the example method 100, the operation 102 of conditioning
the thermal interface material generally includes positioning the
thermal interface material in a conditioning system (e.g., within a
container portion of the conditioning system, etc.) and reducing
the pressure around the thermal interface material, for example, to
thereby remove entrained gas from the thermal interface material,
etc. The conditioning system is configured to hold the thermal
interface material in a generally sealed condition. This allows for
a desired reduced pressure to be achieved within the conditioning
system around the thermal interface material (and then subsequently
maintained as desired). The conditioning system can include a
vacuum chamber, a hermetically sealable bucket (e.g., a five-gallon
bucket, etc.), a sealable bag (e.g., a plastic heat-seal bag,
etc.), at least one or more dispensing cartridge, at least one or
more sealable tubes, any suitable sealable packaging or container,
conditioning system 220 illustrated in FIG. 2, forty-gallon mixers,
etc. within the scope of the present disclosure. In other example
embodiments, the operation 102 of conditioning the thermal
interface material may include at least one or more other suitable
operations, for example, for removing entrained gas from the
thermal interface material, etc.
[0043] As just described, reducing the pressure around the thermal
interface material can include removing gas (e.g., air, etc.) from
inside the conditioning system around the thermal interface
material using suitable operations (e.g., suction operations,
vacuum operations, other sealing operations, etc.). This creates a
low-pressure environment (e.g., a moderate vacuum, etc.) around the
thermal interface material in the conditioning system where a
pressure around the thermal interface material is less than ambient
pressure outside the conditioning system (e.g., ambient air
pressure, etc.). For example, a resulting pressure around the
thermal interface material may be between about 1.0% of a perfect
vacuum (about 29.5 inches of mercury absolute (inHg abs), about
14.5 pounds per square inch absolute (psia), about 100 kilopascals
absolute (kPa abs), or about 750 Torr) and about 99.999% of a
perfect vacuum (about 0.0004 inHg abs, about 0.0002 psia, about
0.001 kPa abs, or about 0.01 Torr).
[0044] As an example, a port may be installed to the conditioning
system and a vacuum may be drawn via the port to directly reduced
pressure (e.g., remove gas from, etc.) around the thermal interface
material inside the conditioning system. The vacuum may be applied
to the thermal interface material for a desired period of time to
achieve a desired pressure within the conditioning system (and
around the thermal interface material). The resulting pressure
(e.g., reduced pressure, vacuum, etc.) may be achieved
substantially instantaneously around the thermal interface material
following application of the vacuum. As an example, a vacuum of at
least about 381 Torr (at least about 15 inHg abs, at least about
7.37 psia, or at least about 50.8 kPa abs) (gauge pressure) may be
applied to the thermal interface material positioned in the
conditioning system for at least about 5 minutes to achieve the
desired reduced pressure.
[0045] Alternatively, reducing pressure around the thermal
interface material can include reducing a temperature of the gas
within the conditioning system around the thermal interface
material while holding a volume of the conditioning system around
the thermal interface material generally constant, or increasing a
volume of the conditioning system around the thermal interface
material while holding a temperature of the gas within the
conditioning system around the thermal interface material generally
constant, etc.
[0046] As an example, the conditioning system and the thermal
interface material contained therein can be heated and then covered
to create a low-pressure environment around the thermal interface
material. More particularly, a container portion of the
conditioning system and the thermal interface material contained
therein can be heated to any desired temperature, and a lid can
then be used to close the container portion while still heated, to
thereby seal the thermal interface material therein. When the
thermal interface material cools, a slight vacuum/gas-tight seal
will form between the container portion and the lid. It should be
appreciated that only a slight increase in temperature of the
container portion and/or the thermal interface material may be
required so that subsequently closing the container portion of the
conditioning system with the lid and allowing the thermal interface
material therein to cool will create the slight vacuum around the
thermal interface material. However, the container portion and/or
the thermal interface material can be heated to any desired
temperature within the scope of the present disclosure (e.g., any
temperature greater than an ambient air temperature around the
conditioning system and/or the thermal interface material within
the conditioning system, and up to a limit of the container portion
of the conditioning system (e.g., about 80 degrees Celsius for a
plastic container portion, etc.), etc.), depending on a desired
level of vacuum to be achieved. Moreover, the container portion
and/or the thermal interface material can be heated for any desired
time frame (e.g., for about 30 seconds, for about 24 hours, etc.)
depending on a desired level of vacuum to be achieved.
[0047] The operation 104 (of inhibiting ambient gas from contacting
the conditioned thermal interface material) of the illustrated
method 100 generally includes maintaining the conditioned thermal
interface material in a generally sealed condition. This protects
the conditioned thermal interface material from exposure to ambient
gas until desired to use the thermal interface material or transfer
the thermal interface material to another container (e.g., for
packaging, storage, transport, etc.). The thermal interface
material may then be retained in the generally sealed condition as
desired, for example, until needed for use, for storage, for
transport to an end user, etc. When transported to the end user in
the generally sealed condition, the end user can unseal the thermal
interface material (exposing the thermal interface material to
ambient gas) and install the thermal interface material as desired
(e.g., within a desired time frame, etc.). As previously described,
the inventors hereof have unexpectedly discovered that if the
conditioned thermal interface material is installed for use in
components in thermal transfer systems (subject to cyclical changes
in temperature during operation) within about 48 hours or less
after unsealing the thermal interface material, such conditioning
of the thermal interface material can help inhibit formation of
cracks, voids, etc. in the thermal interface material during such
use (thereby improving operational reliability of the thermal
interface material).
[0048] Maintaining the conditioned thermal interface material in a
generally sealed condition can include maintaining the conditioned
thermal interface material within the conditioning system (e.g.,
within the container portion of the conditioning system in which
the thermal interface material was conditioned, etc.) following
application of the conditioning operation 102. For example, the
thermal interface material may be maintained in the conditioning
system under the reduced pressure (e.g., under continued vacuum,
etc.). Or, the vacuum can be discontinued and any open portions of
the conditioning system (e.g., any open portions of the container
portion of the conditioning system, etc.) used to remove entrained
gas from around the thermal interface material can be sealed using
suitable operations to thereby inhibit ambient gas from contacting
the conditioned thermal interface material. The thermal interface
material may then be retained in the conditioning system (e.g., in
the container portion of the conditioning system, etc.) as desired,
for example, until needed for use, for storage, for transport to an
end user, until desired to transfer the thermal interface material
to other containers (e.g., for packaging, etc.), etc.
[0049] Alternatively, maintaining the conditioned thermal interface
material in a generally sealed condition can include transferring
(e.g., for packaging, etc.) the conditioned thermal interface
material from the conditioning system to a desired container that
can be sealed (e.g., hermetically sealed, hermetically packaged,
etc.) to thereby hold the thermal interface material under
conditions that inhibit contact of the conditioned thermal
interface material with ambient gas. The container may include, for
example, a hermetically sealable bucket (e.g., a five-gallon
bucket, etc.), a sealable bag (e.g., a plastic heat-seal bag,
etc.), at least one or more dispensing cartridges, at least one or
more sealable tubes, any suitable sealable packaging or container,
etc. within the scope of the present disclosure. The thermal
interface material may then be retained in the sealed container as
desired, for example, until needed for use, for storage, for
transport to an end user, etc. When transported to the end user in
the sealed container, the end user can open the sealed container
(returning the pressure in the container to ambient pressure) and
install the thermal interface material as desired.
[0050] As needed and/or desired, at least one or more of the
operation 102 of conditioning the thermal interface material and
the operation 104 of inhibiting ambient gas from contacting the
conditioned thermal interface material can be repeated (at least
one or more times) when processing the thermal interface material.
For example, if the conditioned thermal interface material is
exposed to ambient gas but is not used within about 48 hours or
less after such exposure, the operation 102 (and possibly operation
104) may be repeated before the thermal interface material is used
to recondition the thermal interface material and thus improve
operational reliability as generally disclosed herein.
[0051] FIG. 2 illustrates an example system 220 configured to
condition thermal interface materials in accord with the present
disclosure. For example, the illustrated system 220 may be used in
connection with method 100, and at least one or more of operations
102 and 104 thereof. In particular, the system 220 is configured to
receive thermal interface materials therein (e.g., alone, already
installed to thermal transfer surfaces, etc.), condition the
thermal interface materials (e.g., remove entrained gases from the
thermal interface materials, etc.), and then maintain the thermal
interface materials under reduced pressure as desired.
[0052] As shown in FIG. 2, the illustrated system 220 generally
includes a container 222, and first and second valve assemblies
224, 226 coupled to the container 222. The container 222 is
configured to receive thermal interface materials therein. And, the
first and second valve assemblies 224, 226 are configured to
control (in conjunction with a vacuum source (not shown)) gas flow
into and/or out of the container 222 (e.g., for reducing pressure
within the container 222 and removing entrained gas from thermal
interface material within the container 222, etc.). For example,
valve assembly 224 operates to regulate the air pressure to the
system 220. And, valve assembly 226 operates to monitor the air
pressure flowing through line 228 to the container 222 (via gauge
unit 226a), and to monitor the vacuum level inside the container
222 (via gauge unit 226b).
[0053] The container 222 includes a base 230 configured to hold the
thermal interface materials therein, and a lid 232 configured to
cover the base 230. A gasket (not visible) can be provided between
the lid 232 and the base 230 to help substantially seal the thermal
interface materials in the container 222 (when the lid 232 is
positioned to cover the base 230). The lid 232 can be coupled to
the base 230 by suitable operations (e.g., mechanical fasteners,
etc.), and may include transparent and/or translucent material so
that thermal interface materials in the container 222 can be viewed
through the lid 232. The illustrated container 222 includes a
generally cylindrical shape, but may include any other suitable
shape within the scope of the present disclosure (e.g., cubic,
spherical, etc.). In addition, the container 222 may include any
desired size (e.g., 5 gallons, etc.) and/or may be formed from any
desired material (e.g., a metallic material (e.g., steel, aluminum,
combinations thereof, etc.), a plastic material, combinations
thereof, etc.) within the scope of the present disclosure.
[0054] In operation of the illustrated system 220, thermal
interface materials are positioned in the base 230, and the lid 232
is positioned over the base 230 to substantially seal the thermal
interface materials in the container 222. The first and second
valve assemblies 224, 226 are then operated to draw a vacuum in the
container 222 and reduce pressure around the thermal interface
materials in the container 222 (e.g., remove entrained gas from the
thermal interface materials, etc.). For example, the first and
second valve assemblies 224, 226 can be operated to draw a vacuum
in the container 222 of at least about 381 Torr (about 15 inHg abs)
for at least about 5 minutes to reduce pressure around the thermal
interface materials in the container 222. Following application of
the vacuum, the conditioned thermal interface materials may remain
in the container 222 as desired. Or, the thermal interface
materials may be removed from the container 222 for use, for
subsequent packaging, etc. as disclosed herein. In other example
embodiments, vacuums of less than about 381 Torr (about 15 inHg
abs) may be drawn in systems to remove entrained gas from thermal
interface materials, and/or vacuums may be drawn for less than
about 5 minutes.
[0055] In some example embodiments of the present disclosure,
thermal interface materials are provided suitable for use to fill
gaps between thermal transfer surfaces in thermal transfer systems.
Here, the thermal interface materials generally include base
materials and thermally conductive particles dispersed within the
base materials. The thermal interface materials are conditioned
(e.g., prior to, while, or after installing the thermal interface
materials in electrical components, etc.) by subjecting them to
reduced pressures within about eight hours before being used to
fill the gaps between the thermal transfer surfaces in the thermal
transfer systems or before being stored under conditions that
inhibit ambient gas from contacting the conditioned thermal
interface materials. As described herein, this helps improve
operational reliability of the thermal interface materials to
transfer heat between the thermal transfer surfaces. In some
example embodiments, the thermal interface materials are subjected
to reduced pressures that are less than ambient air pressure. And
in some example embodiments, the thermal interface materials are
subjected to reduced pressures that are between about 0.01 Torr and
about 750 Torr.
[0056] In some example embodiments of the present disclosure, the
conditioned thermal interface materials are packaged within desired
containers, for example, for storage, transport, etc. (e.g., alone,
already installed to thermal transfer surfaces, etc.). The
containers may be capable of being hermetically sealed with the
thermal interface materials packaged therein under conditions that
inhibit ambient gas from contacting the conditioned thermal
interface materials. In some example embodiments, the thermal
interface materials are shipped, stored, etc. in the hermetically
sealed containers. In some example embodiments, the thermal
interface materials are maintained under conditions that inhibit
ambient gas from contacting the conditioned thermal interface
materials until about 48 hours or less before being used (e.g., to
transfer heat between thermal transfer surfaces, etc.). And more
particularly, the thermal interface materials may be maintained
under such conditions until about 24 hours or less before being
used, or even more particularly until about 12 hours or less before
being used, or still more particularly until about 8 hours or less
before being used. In some example embodiments, the thermal
interface materials may be removed from the hermetically sealed
containers, and then subsequently reconditioned as needed (e.g., if
the thermal interface materials are not used within about 48 hours
or less of being exposed to ambient gas, etc.).
[0057] In some example embodiments, the thermal interface materials
of the present disclosure are substantially free of cracks formed
during use of the thermal interface materials to fill gaps between
thermal transfer surfaces in thermal transfer systems. For example,
the thermal interface materials may be substantially free of cracks
following exposure of the thermal interface materials to thermal
cycling between a temperature of about -20 degrees Celsius and a
temperature of about 160 degrees Celsius, etc. for at least about
10 cycles or more (e.g., 10 cycles, 20 cycles, 40 cycles, 50
cycles, 1,000 cycles, etc.). Also for example, the thermal
interface materials may be substantially free of cracks following
exposure of the thermal interface materials to thermal cycling
comprising a temperature change of at least about 100 degrees
Celsius, etc. for at least about 10 cycles or more (e.g., 10
cycles, 20 cycles, 40 cycles, 50 cycles, 1,000 cycles, etc.)
[0058] In some example embodiments, the thermal interface materials
of the present disclosure are substantially free of cracks formed
during exposure to thermal cycling analysis. In some example
embodiments, the thermal interface materials are substantially free
of cracks formed during exposure of the thermal interface materials
to thermal cycles comprising a temperature change of at least about
100 degrees Celsius. In some example embodiments, the thermal
interface materials of the present disclosure are substantially
free of cracks formed during exposure of the thermal interface
materials to thermal cycles of about -20 degrees Celsius to about
90 degrees Celsius. In some example embodiments, the thermal
interface materials are substantially free of cracks formed during
exposure of the thermal interface materials to thermal cycles of
about -20 degrees Celsius to about 120 degrees Celsius. In some of
these example embodiments, the thermal interface materials of the
present disclosure are substantially free of cracks formed during
exposure of the thermal interface materials to thermal cycles
involving at least about 10 cycles or more (e.g., 10 cycles, 20
cycles, 40 cycles, 50 cycles, 1,000 cycles, etc.).
[0059] In one example embodiment, thermal interface materials of
the present disclosure, at a first time period, are substantially
free of cracks formed during exposure of the thermal interface
materials to thermal cycling between a temperature of about -20
degrees Celsius and at temperature of about 160 degrees Celsius for
at least about 10 cycles during use of the thermal interface
material to fill a gap between at least two surfaces. However, at a
second time period, after exposure of the thermal interface
material (e.g., the same thermal interface material, a sample taken
from the same bulk supply of the thermal interface material, etc.)
to ambient air for at least about eight hours or more, the thermal
interface material exhibits crack formation following exposure to
thermal cycling between a temperature of about -20 degrees Celsius
and a temperature of about 160 degrees Celsius for at least about
10 cycles during use of the thermal interface material to fill a
gap between at least two surfaces.
[0060] Example thermal interface materials suitable for use in
accord with the present disclosure can include a wide range of
materials including, but not limited to, thermally conductive
putties, thermally conductive greases, thermally conductive gap
pads, organic (e.g., polymeric) materials (as compared to an
inorganic (e.g., metal solder) materials), cured self supporting or
free standing pads or sheets (as contrasted to spreadable pastes or
reflowable solders), etc.
EXAMPLES
[0061] The following examples are example in nature. Variations of
the following examples are possible without departing from the
scope of the disclosure.
Example 1
[0062] In this example, presence of entrained gas was evaluated in
four samples of a thermally conductive putty (a silicone thermal
gap filler product). The thermally conductive putty had a thermal
conductivity of about 3 Watts per meter-Kelvin (W/mK), and a
density of about 2.4 grams per cubic centimeter (g/cc).
[0063] A first sample included a bulk sphere of the thermally
conductive putty exposed to ambient laboratory conditions for about
24 hours. The sample was then submerged in degassed liquid silicone
in a clear glass jar, and the jar was placed inside a vacuum
chamber (with a clear window for viewing the sample). A
progressively increasing vacuum was drawn inside the vacuum
chamber, creating an ultimate reduced pressure in the chamber of
about 127 Torr (about 5 inHg abs) (generating a gauge reading of
about -25 inHg in the chamber). The sample was maintained at this
reduced pressure in the chamber for about 1 hour, with the
following observations. Gas bubbles began forming on the surface of
the sample at a reduced pressure of about 254 Torr (about 10 inHg
abs), and increased in quantity up to the ultimate reduced pressure
of about 127 Torr (about 5 inHg abs). FIG. 3 shows the first sample
(and the gas bubbles emerging therefrom) at about the time the
reduced pressure of about 127 Torr (about 5 inHg abs) was achieved
in the chamber. Cracks then began forming on the surface of the
sample, with gas bubbles emerging from the cracks. After about 15
minutes at the reduced pressure of about 127 Torr (about 5 inHg
abs), approximately 50 percent less gas bubbles were emerging from
the sample. And, after about 1 hour at the reduced pressure of
about 127 Torr (about 5 inHg abs), only a small fraction of the gas
bubbles were still emerging from the sample, indicating that a
significant percentage of the gas had been removed from the
sample.
[0064] A second sample included a bulk sphere of the thermally
conductive putty subjected to an initial vacuum conditioning
operation (in accordance with the present disclosure) at a reduced
pressure of about 127 Torr (about 5 inHg abs) (at a gauge reading
of about -25 inHg) for about 15 minutes. The vacuum conditioned
sample was then submerged (immediately following the vacuum
condition operation) in degassed liquid silicone in a clear glass
jar, and the jar was placed inside a vacuum chamber (with a clear
window for viewing the sample). A vacuum was drawn in the vacuum
chamber in substantially the same fashion as for the first sample,
creating an ultimate reduced pressure in the chamber of about 127
Torr (about 5 inHg abs). The sample was then maintained at this
reduced pressure for about 1 hour. FIG. 4 shows the second sample
at about the time the reduced pressure of about 127 Torr (about 5
inHg abs) was achieved in the chamber. As shown in FIG. 4, the
second sample demonstrated a drastically reduced amount of bubbling
from its surface as compared to the first sample (FIG. 3).
Specifically, the quantity of gas bubbles observed in connection
with the second sample at about the time the reduced pressure of
about 127 Torr (about 5 inHg abs) was achieved in the chamber was
about the same as the quantity of gas bubbles observed in
connection with the first sample after being exposed to the reduced
pressure of about 127 Torr (about 5 inHg abs) for about 1 hour.
Thus, the decreased gas bubbles associated with the second sample
(in comparison to the first sample) demonstrates that the initial
vacuum conditioning operation effectively removed entrained gases
from the second sample.
[0065] A third sample included a bulk sphere of the thermally
conductive putty subjected to an initial vacuum conditioning
operation at a reduced pressure of about 127 Torr (about 5 inHg
abs) for about 15 minutes. Following this vacuum conditioning
operation, the sample sat at ambient laboratory conditions for
about 12 hours. The sample was then submerged in degassed liquid
silicone in a clear glass jar, and the jar was placed inside a
vacuum chamber (with a clear window for viewing the sample). A
vacuum was drawn in the vacuum chamber in substantially the same
fashion as for the first sample, creating an ultimate reduced
pressure in the chamber of about 127 Torr (about 5 inHg abs). The
sample was then maintained at this reduced pressure for about 1
hour. FIG. 5 shows the third sample (and the gas bubbles emerging
therefrom) at about the time the reduced pressure reached about 127
Torr (about 5 inHg abs) in the chamber. As shown in FIG. 5, large
quantities of gas bubbles emerged from the sample in similar
fashion to the first sample (FIG. 3), suggesting that removal of
entrained gases in the sample by the initial vacuum conditioning
operation is reversible if the sample is subsequently exposed to
ambient gas as described herein.
[0066] A fourth sample included a bulk sphere of the thermally
conductive putty subjected to an initial vacuum conditioning
operation at a reduced pressure of about 127 Torr (about 5 inHg
abs) for about 15 minutes. Following this vacuum conditioning
operation, the sample was stored in a sealed bag with gas removed
(to help inhibit the sample from coming into contact with ambient
gas) for about 1 month. The sample was then submerged in degassed
liquid silicone in a clear glass jar, and the jar was placed inside
a vacuum chamber (with a clear window for viewing the sample). A
vacuum was drawn in the vacuum chamber in substantially the same
fashion as for the first sample, creating an ultimate reduced
pressure in the chamber of about 127 Torr (about 5 inHg abs). The
sample was then maintained at this reduced pressure for about 1
hour. FIG. 6 shows the fourth sample (and the gas bubbles emerging
therefrom) at about the time the reduced pressure of about 127 Torr
(about 5 inHg abs) was achieved in the chamber. As shown in FIG. 6,
the fourth sample demonstrated a drastically reduced amount of
bubbling from its surface as compared to the first sample (FIG. 3)
and the third sample (FIG. 5), suggesting that no significant
quantity of gas was entrained in the sample during the storage
period.
Example 2
[0067] In this example, thermal cycling analysis was performed on
two samples of a thermally conductive putty (a silicone thermal gap
filler product). The thermally conductive putty had a thermal
conductivity of about 3 W/mK, and a density of about 1.5 g/cc.
[0068] A first sample of the thermally conductive putty was
positioned in a container and subjected to a reduced pressure. In
particular, gas was removed from the container (and entrained gas
was removed from the sample in the container) via application of a
vacuum of about 381 Torr (about 15 inHg abs) to the container and
thermally conductive putty for about 5 minutes (such that the first
sample was vacuum conditioned). A second sample of the thermally
conductive putty was not subjected to the reduced pressure (and was
thus not vacuum conditioned). Thermal cycling analyses were then
immediately performed on the first and second samples. Each sample
was placed between a pair of glass plates, so that effects of the
thermal cycling analysis could be readily observed. Spacers
separated the plates of each pair so that each sample had a
substantially constant thickness of between about 40 mils and about
60 mils (between about 1 millimeter and about 1.5 millimeter). And,
the plates of each pair were held together with spring clip clamps
to help hold the samples at that thickness. Each sample was then
placed in a cycling oven programmed to cycle the samples between a
temperature of about -20 degrees Celsius and a temperature of about
160 degrees Celsius for about 42 cycles (where each cycle had a
duration of about 4 hours). FIG. 7 shows the vacuum conditioned
first sample following analysis. And, FIG. 8 shows the
unconditioned second sample following analysis. As can be seen by
comparing FIG. 7 and FIG. 8, the vacuum conditioned first sample
(FIG. 7) included substantially no visible cracks following
analysis while the unconditioned second sample (FIG. 8) included
substantial visible cracks.
Example 3
[0069] In this example, thermal cycling analysis was performed on
two samples of a thermally conductive putty (a silicone thermal gap
filler product). The thermally conductive putty had a thermal
conductivity of about 2 W/mK, and a density of about 3.0 g/cc.
[0070] A first sample of the thermally conductive putty was
positioned in a container and subjected to a reduced pressure. In
particular, gas was removed from the container (and entrained gas
was removed from the sample in the container) via application of a
vacuum of about 381 Torr (about 15 inHg abs) to the container and
sample for about 5 minutes (such that the first sample was vacuum
conditioned). A second sample of the thermally conductive putty was
not subjected to the reduced pressure (and was thus not vacuum
conditioned). Thermal cycling analyses were then immediately
performed on the first and second samples. Each sample was placed
between a pair of glass plates, so that effects of the thermal
cycling analysis could be readily observed. Spacers separated the
plates of each pair so that each sample had a substantially
constant thickness of between about 40 mils and about 60 mils
(between about 1 millimeter and about 1.5 millimeter). And, the
plates of each pair were held together with spring clip clamps to
help hold the samples at that thickness. Each sample was then
placed in a cycling oven programmed to cycle the samples between a
temperature of about -20 degrees Celsius and a temperature of about
160 degrees Celsius for about 42 cycles (where each cycle had a
duration of about 4 hours). FIG. 9 shows the vacuum conditioned
first sample following analysis. And, FIG. 10 shows the
unconditioned second sample following analysis. As can be seen by
comparing FIG. 9 and FIG. 10, the vacuum conditioned first sample
(FIG. 9) included substantially no visible cracks following
analysis while the unconditioned second sample (FIG. 10) included
substantial visible cracks.
Example 4
[0071] In this example, thermal cycling analysis was performed on
two samples of a thermally conductive putty (a silicone thermal gap
filler product). The thermally conductive putty had a thermal
conductivity of about 3 W/mK, and a density of about 2.4 g/cc.
[0072] A first sample of the thermally conductive putty was
positioned in a container and subjected to a reduced pressure. In
particular, gas was removed from the container (and entrained gas
was removed from the sample in the container) via application of a
vacuum of about 381 Torr (about 15 inHg abs) to the container and
sample for about 5 minutes (such that the first sample was vacuum
conditioned). A second sample of the thermally conductive putty was
not subjected to the reduced pressure (and was thus not vacuum
conditioned). Thermal cycling analyses were then immediately
performed on the first and second samples. Each sample was placed
between a pair of glass plates, so that effects of the thermal
cycling analysis could be readily observed. Spacers separated the
plates of each pair so that each sample had a substantially
constant thickness of between about 40 mils and about 60 mils
(between about 1 millimeter and about 1.5 millimeter). And, the
plates of each pair were held together with spring clip clamps to
help hold the samples at that thickness. Each sample was then
placed in a cycling oven programmed to cycle the samples between a
temperature of about -20 degrees Celsius and a temperature of about
160 degrees Celsius for about 42 cycles (where each cycle had a
duration of about 4 hours). FIG. 11 shows the vacuum conditioned
first sample following analysis. And, FIG. 12 shows the
unconditioned second sample following analysis. As can be seen by
comparing FIG. 11 and FIG. 12, the vacuum conditioned first sample
(FIG. 11) included substantially no visible cracks following
analysis while the unconditioned second sample (FIG. 12) included
substantial visible cracks.
Example 5
[0073] In this example, thermal cycling analysis was performed on
two samples of a thermally conductive grease (a silicone-based
thermal grease having a thermal conductivity of about 3.8 W/mK, a
density of about 2.6 g/cc, and suitable for use in high performance
computer processing units, etc.). A first sample of the thermally
conductive grease was positioned in a container and subjected to a
reduced pressure. In particular, gas was removed from the container
(and entrained gas was removed from the sample in the container)
via application of a vacuum of about 381 Torr (about 15 inHg abs)
to the container and sample for about 5 minutes (such that the
first sample was vacuum conditioned). A second sample of the
thermally conductive grease was not subjected to the reduced
pressure (and was thus not vacuum conditioned). Thermal cycling
analyses were then immediately performed on the first and second
samples. Each sample was placed between a pair of glass plates, so
that effects of the thermal cycling analysis could be readily
observed. Spacers separated the plates of each pair so that each
sample had a substantially constant thickness of between about 40
mils and about 60 mils (between about 1 millimeter and about 1.5
millimeter). And, the plates of each pair were held together with
spring clip clamps to help hold the samples at that thickness. Each
sample was then placed in a cycling oven programmed to cycle the
samples between a temperature of about -20 degrees Celsius and a
temperature of about 160 degrees Celsius for 42 cycles (where each
cycle had a duration of about 4 hours). FIG. 13 shows the vacuum
conditioned first sample following analysis. And, FIG. 14 shows the
unconditioned second sample following analysis. As can be seen by
comparing FIG. 13 and FIG. 14, the vacuum conditioned first sample
(FIG. 13) included few visible cracks following analysis while the
unconditioned second sample (FIG. 14) included substantial visible
cracks.
Example 6
[0074] In this example, thermal cycling analysis was performed on
four samples of a thermally conductive putty (a silicone thermal
gap filler product). The thermally conductive putty had a thermal
conductivity of about 3 W/mK, and a density of about 2.4 g/cc.
[0075] Each sample was prepared as follows prior to analysis. A
first sample of the thermally conductive putty was exposed to
ambient laboratory conditions for about 24 hours. A second sample
of the thermally conductive putty was subjected to an initial
vacuum conditioning operation at a reduced pressure of about 127
Torr (about 5 inHg abs) for about 15 minutes. A third sample of the
thermally conductive putty was subjected to the initial vacuum
conditioning operation at the reduced pressure of about 127 Torr
(about 5 inHg abs) for about 15 minutes, and was then exposed to
ambient laboratory conditions for about 24 hours. And, a fourth
sample of the thermally conductive putty was subjected to the
initial vacuum conditioning operation at the reduced pressure of
about 127 Torr (about 5 inHg abs) for about 15 minutes, and was
then packaged in a sealed container under vacuum (to help inhibit
the sample from coming into contact with ambient gases) for about 1
month. The initial vacuum conditioning operation included
positioning the subject samples in containers and then drawing a
vacuum in the containers of about 127 Torr (about 5 inHg abs) for
about 15 minutes.
[0076] Following the sample preparation, thermal cycling analyses
were immediately performed on the four samples. Each sample was
placed between a pair of generally square glass plates (having
dimensions of about 2.5 inches by about 2.5 inches and a thickness
of about 0.25 inches), so that effects of the thermal cycling
analysis could be readily observed. Spacers separated the plates of
each pair so that each sample had a substantially constant
thickness of between about 40 mils and about 60 mils (between about
1 millimeter and about 1.5 millimeter). And, the plates of each
pair were held together with spring clip clamps to help hold the
samples at that thickness. Each sample was then placed in a cycling
oven programmed to cycle the samples between a temperature of about
-20 degrees Celsius and a temperature of about 160 degrees Celsius
at a rate of about 1.5 degrees Celsius per minute for about 42
cycles (such that each cycle had a duration of about 4 hours, and
analysis lasted about 7 days).
[0077] FIG. 15 shows the first sample following analysis, FIG. 16
shows the second sample following analysis, FIG. 17 shows the third
sample following analysis, and FIG. 18 shows the fourth sample
following analysis. As can be seen by comparing FIGS. 15-18, the
second and fourth samples (FIG. 16 and FIG. 18, respectively),
which were subjected to the initial vacuum conditioning operation
within about 24 hours of analysis, exhibited substantially no
visible cracks. The first and third samples (FIG. 15 and FIG. 17,
respectively), however, which were exposed to ambient laboratory
conditions for about 24 hours prior to analysis, exhibited
substantial visible cracks. As such, the first sample (FIG. 15)
shows the adverse effects of thermal cycling on the thermally
conductive putty (when not initially subjected to the vacuum
conditioning operation). The second sample (FIG. 16) shows the
benefits (e.g., substantially reduced surface cracking, etc.) of
the vacuum conditioning operation when applied to the thermally
conductive putty. The third sample (FIG. 17) shows that the
benefits of the vacuum conditioning operation when applied to the
thermally conductive putty can wear off over time, such that
subsequent use of the thermally conductive putty in applications
involving thermal cycling can result in undesirable crack
formation. And, the fourth sample (FIG. 18) shows that the benefits
of the vacuum conditioning operation when applied to the thermally
conductive putty can be maintained over time by packaging the
vacuum conditioned thermally conductive putty in a sealed container
under vacuum to protect it from exposure to ambient gas.
[0078] Example embodiments of the present disclosure can be used to
condition bulk supplies of thermal interface materials. Such bulk
supplies can include any desired volume of material.
[0079] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, systems, devices, and methods, to
provide a thorough understanding of embodiments of the present
disclosure. It will be apparent to those skilled in the art that
specific details need not be employed, that example embodiments may
be embodied in many different forms and that neither should be
construed to limit the scope of the disclosure. In some example
embodiments, well-known processes, well-known device structures,
and well-known technologies are not described in detail.
[0080] In addition, the disclosure of particular values (e.g.,
pressures, times, dimensions, etc.) herein is not exclusive of
other values that may be useful in other example embodiments
depending, for example, on particular thermal interface materials
being processed, other factors, etc.
[0081] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore 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. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0082] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, 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 engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0083] 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 may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. 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 example embodiments.
[0084] Spatially relative terms, such as "inner," "outer,"
"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. Spatially relative terms may be
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 example 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.
[0085] The disclosure herein of particular values and particular
ranges of values for given parameters are not exclusive of other
values and ranges of values that may be useful in one or more of
the examples disclosed herein. Moreover, it is envisioned that any
two particular values for a specific parameter stated herein may
define the endpoints of a range of values that may be suitable for
the given parameter. The disclosure of a first value and a second
value for a given parameter can be interpreted as disclosing that
any value between the first and second values could also be
employed for the given parameter. Similarly, it is envisioned that
disclosure of two or more ranges of values for a parameter (whether
such ranges are nested, overlapping or distinct) subsume all
possible combination of ranges for the value that might be claimed
using endpoints of the disclosed ranges.
[0086] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *