U.S. patent application number 16/175666 was filed with the patent office on 2020-04-30 for implementing strain sensing thermal interface materials.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Eric J. Campbell, Sarah K. Czaplewski-Campbell, Joseph Kuczynski, Timothy Tofil.
Application Number | 20200135611 16/175666 |
Document ID | / |
Family ID | 70056575 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200135611 |
Kind Code |
A1 |
Czaplewski-Campbell; Sarah K. ;
et al. |
April 30, 2020 |
IMPLEMENTING STRAIN SENSING THERMAL INTERFACE MATERIALS
Abstract
Methods and structures are provided for implementing strain
sensing thermal interface materials (TIMs). An in situ strain
sensing thermal interface material (TIM) layer is provided within a
packaging assembly structure. The strain sensing TIM is formed by
graphene incorporated into the TIM layer. Electrical leads are
coupled to the strain sensing TIM layer providing electrical
contacts for measuring the electrical property change of the TIM
which correlates to mechanical strain.
Inventors: |
Czaplewski-Campbell; Sarah K.;
(Rochester, MN) ; Tofil; Timothy; (Rochester,
MN) ; Campbell; Eric J.; (Rochester, MN) ;
Kuczynski; Joseph; (North Port, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
70056575 |
Appl. No.: |
16/175666 |
Filed: |
October 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/4871 20130101;
H01L 23/373 20130101; G01L 1/2287 20130101; H01L 23/42 20130101;
G01L 1/20 20130101; H01L 23/3733 20130101 |
International
Class: |
H01L 23/373 20060101
H01L023/373; G01L 1/22 20060101 G01L001/22; H01L 21/48 20060101
H01L021/48 |
Claims
1. A packaging structure for implementing strain gauge thermal
interface materials (TIMs) comprising: an in situ strain sensing
thermal interface material (TIM) layer in the packaging structure;
graphene incorporated into the TIM layer providing the strain
sensing capability for measuring strain on the strain sensing TIM
layer, and electrical leads coupled to the strain sensing TIM layer
providing electrical contacts for measuring strain.
2. The structure as recited in claim 1, wherein the thermal
interface material (TIM) has predefined viscoelastic
properties.
3. The structure as recited in claim 2, wherein the thermal
interface material (TIM) maintains the viscoelastic properties in
the packaging structure.
4. The structure as recited in claim 1, wherein the strain sensing
TIM is electrically conductive.
5. The structure as recited in claim 1, wherein the graphene
changes the electromechanical properties of the thermal interface
material (TIM).
6. The structure as recited in claim 1, wherein the strain sensing
TIM layer is formed by incorporating graphene nanosheets prepared
by processing liquid phase-exfoliation of graphite producing
nanosheets in to the TIM.
7. The structure as recited in claim 6, wherein the nanosheets
having lengths in a range of approximately 200 nm to 800 nm.
8. The structure as recited in claim 1, wherein the packaging
structure includes the in situ strain sensing thermal interface
material (TIM) layer disposed between a heat source module and a
heat sink.
9. The structure as recited in claim 8, wherein the in situ strain
sensing thermal interface material (TIM) layer enables detecting
when the TIM layer should be replaced.
10. The structure as recited in claim 1, wherein the situ strain
sensing thermal interface material (TIM) layer incorporates
graphene nanosheets.
11. A method for implementing strain sensing thermal interface
materials (TIMs) comprising: providing an in situ strain sensing
thermal interface material (TIM) in a packaging structure; enabling
strain sensing capability by blending graphene into the thermal
interface material (TIM); and providing electrical leads coupled to
a TIM layer for measuring electrical property change of the TIM
cause by mechanical deformation.
12. The method as recited in claim 11, wherein enabling strain
sensing capability in the strain sensing TIM includes blending
graphene nanosheets into the TIM.
13. The method as recited in claim 11, wherein providing an in situ
strain sensing thermal interface material (TIM) in a packaging
structure includes providing a thermal interface material (TIM)
having predefined viscoelastic properties.
14. The method as recited in claim 11, wherein the thermal
interface material (TIM) maintains the viscoelastic properties
assembled within the packaging structure.
15. The method as recited in claim 11, wherein the strain sensing
thermal interface material (TIM) is electrically conductive.
16. The method as recited in claim 15, further comprising: using
the in situ strain sensing thermal interface material (TIM) layer
for detecting when the TIM layer should be replaced
17. The method as recited in claim 11, wherein graphene nanosheets
are prepared by processing liquid phase exfoliation of graphite
producing graphene nanosheets.
18. The method as recited in claim 11, wherein providing electrical
leads coupled to the TIM layer for forming electrical contacts for
measuring strain includes embedding electrical leads into the TIM
layer providing electrical contacts for the measuring strain.
19. The method as recited in claim 11, wherein embedding electrical
leads into the TIM layer includes embedding a wire array into the
TIM layer attached to a heat sink.
20. The method as recited in claim 11, includes disposing the in
situ strain sensing thermal interface material (TIM) layer between
a heat source module and a heat sink.
Description
FIELD OF THE INVENTION
[0001] The present disclosure relates generally to thermal
interface materials (TIMs), and more particularly, relates to
methods and structures for implementing strain sensing thermal
interface materials (TIMs) used in data processing field.
BACKGROUND
[0002] Thermal interface materials (TIMs) are used extensively to
improve thermal conduction across two mating parts.
[0003] In situ strain gauges would be useful in thermal interface
materials (TIMs) that are used within microprocessor and server
packaging.
[0004] For example, putty and grease TIMs, often used between a
module and heatsink, have a propensity to pump-out with thermal
cycling. This material pump-out reduces heat transfer away from the
module and overall performance. Therefore, it would be beneficial
to monitor pump-out over time in the field or during qualification
testing.
SUMMARY
[0005] Principal aspects of the present disclosure are to provide
methods and structures for implementing strain sensing thermal
interface materials (TIMs). Other important aspects of the present
disclosure are to provide such methods and structures substantially
without negative effects and that overcome many of the
disadvantages of prior art arrangements.
[0006] In brief, methods and structures are provided for
implementing strain sensing thermal interface materials (TIMs). An
in situ strain sensing thermal interface materials (TIM) layer is
provided within a packaging assembly structure. The strain sensing
TIM is formed by graphene incorporated into the TIM layer.
Electrical leads are coupled to the strain sensing TIM layer
providing electrical contacts for measuring the electrical property
change of the TIM which correlates to mechanical strain.
[0007] In accordance with features of the disclosure, incorporating
graphene in TIMs enables the user to monitor the strain in real
time which is especially useful during qualification testing of new
parts to characterize expected TIM performance.
[0008] In accordance with features of the disclosure, the strain
sensing TIM includes electrical conductors, optionally an
electrically conductive mesh formed of a selected material from a
group including copper, copper plated with nickel, coupled to the
strain gauge provided with the thermal interface materials (TIM)
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present disclosure together with the above and other
objects and advantages may best be understood from the following
detailed description of the preferred embodiments of the disclosure
illustrated in the drawings, wherein:
[0010] FIG. 1 is a flow chart illustrating example steps for
implementing in situ strain sensing thermal interface materials
(TIMs) in accordance with an illustrative embodiment;
[0011] FIG. 2 is a side view not to scale schematically
illustrating an example structure including an in situ strain
sensing thermal interface material (TIM) in accordance with an
illustrative embodiment; and
[0012] FIG. 3 is a top down planar view not to scale schematically
illustrating the strain gauge thermal interface material (TIM)
together with example electrical contacts in accordance with an
illustrative embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] In the following detailed description of embodiments of the
disclosure, reference is made to the accompanying drawings, which
illustrate example embodiments by which the disclosure may be
practiced. It is to be understood that other embodiments may be
utilized and structural changes may be made without departing from
the scope of the disclosure.
[0014] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the disclosure. 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.
[0015] In accordance with features of the disclosure, methods and
structures are provided for implementing in situ strain sensing
thermal interface materials (TIMs). The thermal interface materials
(TIMs) of an illustrative embodiment contain graphene which render
the TIM electrically conductive while maintaining the viscoelastic
properties of the TIM in the packaging structure.
[0016] A thermal interface material (TIM) describes any material
that is inserted between two parts in order to enhance the thermal
coupling between these two components. For heat dissipation, the
TIM is inserted between a heat source or heat producing device and
a heat sink or heat dissipation device. Thermal interface materials
(TIMs) include thermal grease, putty, and adhesive.
[0017] In accordance with features of the disclosure, incorporation
of graphene nanosheets into a TIM is provided in order to create an
in situ strain gauge. Graphene nanosheets are blended into a
silicone based TIM or other viscoelastic TIM forming an in situ
strain gauge for use in packaging assemblies to monitor strain in
situ. Strain measurements are used in the field, for example, to
determine if TIM pump-out is occurring and if the TIM layer should
be replaced.
[0018] Referring now to FIG. 1, there is shown a flow chart
illustrating example steps for implementing strain sensing thermal
interface materials (TIMs) generally designated by the reference
character 100 in accordance with a preferred embodiment. Referring
also to FIGS. 2 and 3, there are shown an example structure
including in situ strain sensing thermal interface material (TIM)
layer in accordance with preferred embodiments.
[0019] Referring to FIG. 2, there is shown a side view not to scale
schematically illustrating an example structure generally
designated by the reference character 200 including an in situ
strain sensing layer thermal interface material (TIM) layer 202 in
accordance with a preferred embodiment. Structure 200 includes a
printed circuit board (PCB) 204 carrying a heat source module 206.
The in situ strain sensing layer thermal interface material (TIM)
layer 202 is applied to the heat source module 206. Structure 200
includes a heat sink 208 with the in situ strain sensing layer
thermal interface materials (TIMs) layer 202 extending between the
heat source module 206 and the heat sink 208. Electrical wires 210
are provided in the in situ strain gauge TIM layer 202 for
providing the electrical contacts for measuring the electrical
property change of the TIM which correlates to mechanical
strain.
[0020] In FIG. 1, as indicated at a block 102, graphene nanosheets
are formed for use in a thermal interface material (TIM) layer 202
shown in FIGS. 2 and 3. At block 102, graphene nanosheets are
formed by liquid phase exfoliation of graphite, for example, in
n-methyl-pyrrolidone producing nanosheets with lengths of
.about.200 nm to 800 nm. Graphene can be prepared as generally
described by the publication entitled "Sensitive electromechanical
sensors using viscoelastic graphene-polymer nanocomposites" by
Boland et al., in Science 354 (6317), sciencemag.org, 9 Dec. 2018,
pps. 1257-1260. Then, as indicated at a block 104, the graphene
nanosheets are transferred to chloroform or (other suitable
solvent) and mixed with a viscoelastic, for example, silicone-based
TIM that keeps its viscoelastic characteristics in accordance with
a preferred embodiment.
[0021] As indicated at a block 106, the strain sensing TIM is
applied to a heat source module in the assembly structure, forming
the in situ strain sensing thermal interface material (TIM) layer
202 shown in FIG. 2.
[0022] As indicated at a block 108, electrical leads are coupled to
the in situ strain sensing thermal interface material (TIM) layer
202 providing electrical contacts for measuring the electrical
property change of the strain sensing TIM which correlates to
mechanical strain. The electrical leads include, for example,
isolated conductors in a wire mesh with the wire conductors or
electrically conductive mesh providing electrical contacts for the
strain sensing TIM. Example electrical lead wires 210 are
illustrated in FIGS. 2 and 3 including, for example, isolated
conductors or an electrically conductive mesh 210, for example,
formed of a selected material including copper, copper plated with
nickel, and aluminum.
[0023] In accordance with features of the disclosure, the strain
sensing TIM layer 202 includes the wire mesh of embedded wires 210
in the TIM layer 202 to provide the electrical contacts. These wire
leads 210 optionally are embedded into the TIM and attached on the
heat sink 208. By forming a wire array 210, as best shown in FIG.
3, strain at multiple points on the strain sensing TIM layer 202 in
the assembly structure 200 can be monitored and corrective action
taken prior to excessive pump out or failure of the TIM layer 202.
The strain monitoring techniques can be employed not only in the
field, but also as a valuable qualification tool.
[0024] As indicated at a block 106, a strain sensing thermal
interface material (TIM) layer 202 is applied to a heat source
module 206 as shown in the assembly structure 200. Electrical
connections 210, for example, leads for strain monitoring of the
strain sensing TIM layer 202 are attached as indicated at a block
108. Finally a heat sink or heat spreader 208 or other similar heat
transfer device 208 is installed in the assembly structure 200 as
indicated at a block 110.
[0025] In accordance with features of the disclosure, in an
embodiment of the disclosure forming the electrical leads for
strain monitoring includes embedding an electrical wire mesh 210
within the strain gauge TIM layer 202, as shown in FIGS. 2 and
3.
[0026] While the present disclosure has been described with
reference to the details of the embodiments of the disclosure shown
in the drawing, these details are not intended to limit the scope
of the disclosure as claimed in the appended claims.
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