U.S. patent application number 11/080028 was filed with the patent office on 2005-07-21 for integrated heat spreader package for heat transfer and for bond line thickness control and process of making.
This patent application is currently assigned to Intel Corporation. Invention is credited to Brandenburger, Peter, Deppisch, Carl L., Houle, Sabina J., Hua, Fay, Phillippe, Kim L., Whittenburg, Kris J..
Application Number | 20050157471 11/080028 |
Document ID | / |
Family ID | 32042771 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050157471 |
Kind Code |
A1 |
Whittenburg, Kris J. ; et
al. |
July 21, 2005 |
Integrated heat spreader package for heat transfer and for bond
line thickness control and process of making
Abstract
A system includes a thermal interface material (TIM) to transfer
heat from a die to a heat spreader. The system includes a heat
transfer subsystem disposed on the backside surface of the die. In
one embodiment, the heat transfer subsystem comprises a first heat
transfer material and a second heat transfer material discretely
disposed within the first heat transfer material. A method of
bonding a die to a heat spreader uses a die-referenced process as
opposed to a substrate-referenced process.
Inventors: |
Whittenburg, Kris J.;
(Tempe, AZ) ; Hua, Fay; (San Jose, CA) ;
Deppisch, Carl L.; (Phoenix, AZ) ; Houle, Sabina
J.; (Phoenix, AZ) ; Brandenburger, Peter;
(Chandler, AZ) ; Phillippe, Kim L.; (Phoenix,
AZ) |
Correspondence
Address: |
Schwegman, Lundberg, Woessner & Kluth, P.A.
P.O. Box 2938
Minneapolis
MN
55402
US
|
Assignee: |
Intel Corporation
|
Family ID: |
32042771 |
Appl. No.: |
11/080028 |
Filed: |
March 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11080028 |
Mar 15, 2005 |
|
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10266996 |
Oct 8, 2002 |
|
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6867978 |
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Current U.S.
Class: |
361/719 ;
257/E23.09; 257/E23.112 |
Current CPC
Class: |
H01L 2224/16 20130101;
H01L 23/3733 20130101; H01L 2924/16152 20130101; H01L 2224/73253
20130101; H01L 2924/00014 20130101; H01L 2924/14 20130101; H01L
2924/14 20130101; H01L 23/433 20130101; H01L 24/29 20130101; H01L
2924/00014 20130101; H01L 2924/00 20130101; H01L 2224/0401
20130101 |
Class at
Publication: |
361/719 |
International
Class: |
H05K 007/20 |
Claims
1-9. (canceled)
10. An integrated heat spreader system comprising: a heat spreader
body having a recess; an interface subsystem in the recess, wherein
the interface subsystem is selected from (1) a first heat transfer
material, (2) the first heat transfer material and a second heat
transfer material discretely disposed within the first heat
transfer material, and (3) the second heat transfer material alone
having a discrete patterning within the recess.
11-13. (canceled)
14. The integrated heat spreader system according to claim 10,
wherein the first heat transfer material includes an
organic-inorganic composite.
15. The integrated heat spreader system according to claim 10,
wherein the first heat transfer material further includes: an
organic-inorganic composite including a polymer or a resin;
optionally an inorganic dielectric; and optionally at least one
metallic.
16-18. (canceled)
19. A thermal interface comprising: a first heat transfer material,
selected from a low melting point solder, a polymer, a polymer and
a low melting point solder, a polymer and an inorganic dielectric,
and a polymer and a low melting-point solder and an inorganic
dielectric; and a high melting-point solder second heat transfer
material, discretely disposed within the first heat transfer
material, wherein the high melting-point solder second heat
transfer material has a higher thermal conductivity than the first
heat transfer material.
20. The thermal interface according to claim 19, wherein the high
melting point solder second heat transfer material includes at
least one solder island that has a characteristic thickness in a
range from about 0.1 micron to about 25 micron.
21. (canceled)
22. The thermal interface according to claim 19, further including:
an integrated heat spreader, wherein the thermal interface is on
the integrated heat spreader.
23. (canceled)
24. The thermal interface according to claim 19, wherein the first
heat transfer material is a low melting point solder, and the high
melting-point solder second heat transfer material is present in a
volume range from about 0% to about 5%.
25. A packaging process comprising: coupling a thermal management
device to a die through an interface subsystem, wherein the thermal
management device is selected from an integrated heat spreader, a
heat pipe, and a planar heat sink, and wherein the interface
subsystem is selected from a first heat transfer material, and the
first heat transfer material and a second heat transfer material
discretely disposed within the first heat transfer material,
wherein the first heat transfer material has either a first melting
temperature or a first curing temperature, and the second heat
transfer material has a second melting temperature higher than the
first temperature; and bonding the interface subsystem to the
thermal management device and the die.
26. The process according to claim 25, wherein the first heat
transfer material is selected from a low melting-point solder, an
organic composition, and a combination thereof, and wherein bonding
the interface subsystem includes reflowing the low melting-point
solder or curing and hardening the organic composition.
27. The process according to claim 25, wherein the first heat
transfer material includes a low melting-point solder, wherein the
second heat transfer material includes a high melting-point solder,
and wherein bonding the interface subsystem includes reflowing the
low melting-point solder.
28. The process according to claim 25, wherein coupling the thermal
management device to the die through an interface subsystem further
includes: disposing the first heat transfer material against the
thermal management device; disposing the second heat transfer
material against the die; and coupling the first heat transfer
material and the second heat transfer material.
29. The process according to claim 25, wherein coupling the thermal
management device to the die through an interface subsystem further
includes: disposing the first heat transfer material and the second
heat transfer material against the thermal management device; and
coupling the first heat transfer material and the second heat
transfer material with the die.
30. The process according to claim 25, wherein coupling the thermal
management device to the die through an interface subsystem further
includes: disposing the first heat transfer material and the second
heat transfer material against the die; and coupling the first heat
transfer material and the second heat transfer material with the
thermal management device.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/266996, filed on Oct. 8, 2002, which is incorporated
herein by reference.
BACKGROUND INFORMATION
[0002] 1. Technical Field
[0003] Embodiments of the present invention relate to an integrated
heat spreader as it is bonded to a die. The bond includes a
high-temperature bump or other structure that is discretely
intermingled with a lower-temperature material.
[0004] 2. Description of Related Art
[0005] One of the issues encountered when using an integrated heat
spreader (IHS) is getting a balance between sufficient adhesion to
the die, and a high enough heat flow to meet the cooling load of
the die. To deal with this issue, different bonding materials have
been tried with varying results. If the adhesion is insufficient,
the IHS may spall off from the thermal interface material (TIM) and
result in a yield issue or a field failure. Another issue
encountered is achieving an acceptable IHS standoff from the die
and the board to which the board is mounted. Because of various
existing processes, a substrate-referenced process is used that may
cause a significant variation in bond-line thickness (BLT) between
the top of the die and the bonding surface of the IHS.
[0006] TIM BLT is maintained for mechanical reliability of the
thermal interface during thermal cycling. Due to the difference in
the coefficients of thermal expansion of the IHS and the die, there
is a large amount of shear stress imposed on the TIM. Thicker bond
lines assist the TIM to withstand these high stresses without
failing.
[0007] TIM BLT is also an element in the thermal resistance of the
thermal interface. A thinner TIM BLT can result in a lower thermal
resistance. Due to these limits in TIM BLT, which can be required
for acceptable package performance, TIM BLT must be tightly
controlled.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In order to understand the manner in which embodiments of
the present invention are obtained, a more particular description
of various embodiments of the invention briefly described above
will be rendered by reference to the appended drawings.
Understanding that these drawings depict only typical embodiments
of the invention that are not necessarily drawn to scale and are
not therefore to be considered to be limiting of its scope, the
embodiments of the invention will be described and explained with
additional specificity and detail through the use of the
accompanying drawings in which:
[0009] FIG. 1 is an elevational cross-section of a package
according to an embodiment;
[0010] FIG. 2 is a partial cut-away cross-sectional view of the
packaging system depicted in FIG. 1 taken along the section line
2-2;
[0011] FIG. 3 is a cut-away cross-sectional view of a portion of
the packaging system depicted in FIG. 1 taken along the section
line 3-3;
[0012] FIG. 4 is a cutaway cross-sectional view of a portion of an
elongate, rectangular package according to an embodiment;
[0013] FIG. 5 is a cross-sectional view of an interface subsystem
according to an embodiment;
[0014] FIG. 6 is a cross-sectional view of an interface subsystem
according to an embodiment;
[0015] FIG. 7 is a cross-sectional view of an interface subsystem
according to an embodiment; and
[0016] FIG. 8 is a process flow diagram that depicts non-limiting
packaging process embodiments.
DETAILED DESCRIPTION
[0017] One embodiment of the present invention relates to a system
that includes a thermal interface material (TIM) intermediary
between a heat spreader and a die for heat transfer out of the die.
One embodiment includes a method of bonding a die to a heat
spreader that uses a die-referenced process as opposed to a
substrate-referenced process.
[0018] The following description includes terms, such as upper,
lower, first, second, etc. that are used for descriptive purposes
only and are not to be construed as limiting. The embodiments of a
device or article described herein can be manufactured, used, or
shipped in a number of positions and orientations. The terms "die"
and "processor" generally refer to the physical object that is the
basic workpiece that is transformed by various process operations
into the desired integrated circuit device. A board is typically a
resin-impregnated fiberglass structure that acts as a mounting
substrate for the die. A die is usually singulated from a wafer,
and wafers may be made of semiconducting, non-semiconducting, or
combinations of semiconducting and non-semiconducting
materials.
[0019] Reference will now be made to the drawings wherein like
structures will be provided with like reference designations. In
order to show the structures of embodiments most clearly, the
drawings included herein are diagrammatic representations of
inventive articles. Thus, the actual appearance of the fabricated
structures, for example in a photomicrograph, may appear different
while still incorporating the essential structures of embodiments.
Moreover, the drawings show only the structures necessary to
understand the embodiments. Additional structures known in the art
have not been included to maintain the clarity of the drawings.
[0020] FIG. 1 is an elevational cross-section of a packaging system
10 according to an embodiment. The packaging system 10 includes a
die 12 with an active surface 14 and a backside surface 16. The die
12 is connected to a thermal management device. In one embodiment,
the thermal management device is integrated heat spreader 18 that
is disposed above the backside surface 16 of the die 12. An
interface subsystem 20, in the form of a TIM, is disposed between a
backside surface 16 and the integrated heat spreader 18. The
interface subsystem 20 includes a first heat transfer material 22
and a second heat transfer material 24 that is discretely disposed
within the first heat transfer material 22. In one embodiment, the
second heat transfer material 24 has a higher thermal conductivity
that the first heat transfer material 22.
[0021] In one embodiment where the two heat transfer materials are
metals, the second heat transfer material 24 has a higher melting
point than the first heat transfer material 22. In one embodiment
where the first heat transfer material is an organic, the second
heat transfer material 24 has a melting point that is higher than
the curing temperature of the first heat transfer material 22.
[0022] In another embodiment, the first heat transfer material 22
in an organic-inorganic composite. The organic-inorganic composite
in one embodiment includes a polymer, optionally an inorganic
dielectric, and optionally at least one metallic. The inorganic
dielectric may be a material as is used as filler in thermal
interface structures. One embodiment of an inorganic dielectric is
fused silica and the like. Where a metallic material is used as a
portion of an organic-inorganic composite, the metallic material in
one embodiment is a low melting-point solder or the like.
[0023] As depicted in FIG. 1, the interface subsystem 20 is
depicted as having a low melting-point solder first heat transfer
material 22 having a first melting point and a high melting-point
solder second heat transfer material 24 that is discretely disposed
within the first heat transfer material 22 and having a second
melting point that is higher than that of the first melting point.
In one embodiment, the packaging system 10 includes a second heat
transfer material 24 that is at least one solder island that is
discretely disposed within the first heat transfer material 22.
[0024] In one embodiment, a reactive solder system is used. A
reactive solder material includes properties that allow for
adhesive and/or heat-transfer qualities. For example, the reactive
solder material can melt and resolidify without a pre-flux cleaning
that was previously required. Further, a reactive solder embodiment
can also include bonding without a metal surface. Without the need
of a metal surface for bonding, processing can be simplified.
[0025] In one embodiment, a reactive solder includes a base solder
that is alloyed with an active element material. In one embodiment,
a base solder is indium. In one embodiment, a base solder is tin.
In one embodiment, a base solder is silver. In one embodiment, a
base solder is tin-silver. In one embodiment, a base solder is at
least one lower-melting-point metal with any of the above base
solders. In one embodiment, a base solder is a combination of at
least two of the above base solders. Additionally, conventional
lower-melting-point metals/alloys can be used.
[0026] The active element material is alloyed with the base solder.
In one embodiment, the active element material is provided in a
range from about 2% to about 30% of the total solder. In one
embodiment, the active element material is provided in a range from
about 2% to about 10%. In one embodiment, the active element
material is provided in a range from about 0.1% to about 2%.
[0027] Various elements can be used as the active element material.
In one embodiment, the active element material is selected from
hafnium, cerium, lutetium, other rare earth elements, and
combinations thereof. In one embodiment, the active element
material is a refractory metal selected from titanium, tantalum,
niobium, and combinations thereof. In one embodiment, the active
element material is a transition metal selected from nickel,
cobalt, palladium, and combinations thereof. In one embodiment, the
active element material is selected from copper, iron, and
combinations thereof. In one embodiment, the active element
material is selected from magnesium, strontium, cadmium, and
combinations thereof.
[0028] The active element material when alloyed with the base
solder can cause the alloy to become reactive with a semiconductive
material such as the backside surface 16 of the die 12. The alloy
can also become reactive with an oxide layer of a semiconductive
material such as silicon oxide, gallium arsenide oxide, and the
like. The alloy can also become reactive with a nitride layer of a
semiconductive material such as silicon nitride, silicon
oxynitride, gallium arsenide nitride, gallium arsenide oxynitride,
and the like.
[0029] Reaction of the alloy with the die 12 can be carried out by
thermal processing. Heat can be applied by conventional processes,
such that the active element materials reach the melting zone of
the base solder. For example, where the base solder includes
indium, heating is carried out in a range from about 150.degree. C.
to about 200.degree. C.
[0030] During reflow of the alloy, the active element(s) dissolve
and migrate to the backside surface 16 of the die 12.
Simultaneously, the base solder bonds to the integrated heat
spreader 18. It is not necessary that the backside surface 16 be
metalized prior to soldering. The solder joint (not depicted) that
is formed by the reactive solder material can display a bond
strength in a range from about 1,000 psi and about 2,000 psi.
[0031] FIG. 2 is a partial cut-away cross-sectional view of the
packaging system 10 taken along the section line 2-2'. It is noted
that in FIG. 1, the integrated heat spreader 18 is attached to a
mounting substrate 26 such as a printed circuit board (PCB), such
as a main board, a motherboard, a mezzanine board, an expansion
card, or another mounting substrate, with a bonding material 28
that secures a lip portion 30 of the integrated heat spreader 18
thereto. In one embodiment, the thermal management device is a heat
sink without a lip structure such as a simple planar heat sink. In
one embodiment the thermal management device includes a heat pipe
configuration. It is noted in FIG. 1 that the die 12 is disposed
between the interface subsystem 20 and a series of electrical bumps
32 that are in turn each mounted on a series of bond pads 34. The
electrical bumps 32 make contact with the active surface 14 of the
die 12. Contrariwise, the interface subsystem 20 makes thermal
contact with the backside surface 16 of the die 12.
[0032] As taken along the section line 2-2', FIG. 2 illustrates a
cross-section of the bonding material 28 that fastens a lip portion
30 (FIG. 1) of the integrated heat spreader 18 (FIG. 1) to the
mounting substrate 26 (FIG. 1). Additionally, the electrical bumps
32 are depicted in a ball grid array as is known in the art.
[0033] FIG. 3 is a cut-away cross-sectional view of a portion of
the packaging system 10 depicted in FIG. 1 taken along the section
line 3-3'. It can be seen in FIG. 3, that the lip portion 30 of the
integrated heat spreader 18 is exposed in this view. Additionally,
FIG. 3 depicts a cross-section of the interface subsystem 20, which
includes a pattern of solder islands that are the second heat
transfer material 24 and that are discretely disposed within the
first heat transfer material 22. Although the pattern of solder
islands in the second heat transfer material 24 is depicted as a
five-element grouping, patterning according to various embodiments
includes a single solder island, two solder islands, three solder
islands that are either linearly arranged or otherwise, and
multiple solder islands that are arrayed according to the needs of
a given application of an embodiment.
[0034] According to an embodiment, the heat transfer materials
include solder. The solder may contain lead (Pb) or be a
substantially Pb-free solder. By "substantially Pb-free solder", it
is meant that the solder is not designed with Pb content according
to industry trends. A substantially Pb-free solder in one
embodiment includes an SnAgCu solder as is known in the art.
[0035] One example of a Pb-containing solder includes a tin-lead
solder. In selected embodiments, Pb-containing solder is a tin-lead
solder composition such as from 97% tin (Sn)/3% lead (Sn3Pb). A
tin-lead solder composition that may be used as the first heat
transfer material 22 or as the second heat transfer material 24 is
a Sn63Pb composition of 37% tin/63% lead. In any event, the
Pb-containing solder may be a tin-lead solder comprising
Sn.sub.xPb.sub.y, wherein x+y total 1, and wherein x is in a range
from about 0.3 to about 0.99. In one embodiment, the Pb-containing
solder is a tin-lead solder composition of Sn3Pb for the first heat
transfer material 22, and for the second heat transfer material 24,
it is a tin-lead solder composition of Sn63Pb.
[0036] The following discussion refers specifically to structures
depicted in FIGS. 1-3, but it applies generally to embodiments set
forth herein. In one embodiment, the first heat transfer material
22 includes a Pb-containing solder, and the second heat transfer
material 24 contains a Pb-containing solder that has a higher
melting point than the first heat transfer material 22. In another
embodiment, the first heat transfer material 22 includes a
Pb-containing solder, and the second heat transfer material 24
contains a substantially Pb-free solder that has a higher melting
point than the first heat transfer material 22. In another
embodiment, the first heat transfer material 22 includes a
substantially Pb-free solder, and the second heat transfer material
24 also contains a substantially Pb-free solder that has a higher
melting point than the first heat transfer material 22. In another
embodiment, the first heat transfer material 22 includes a
substantially Pb-free solder, and the second heat transfer material
24 includes a Pb-containing solder that has a higher melting point
than the first heat transfer material 22.
[0037] In one embodiment, the solder islands are arranged in an
elongate, rectangular configuration that may follow the outline of
a rectangular die, as will now be discussed with reference to FIG.
4.
[0038] FIG. 4 is a cut-away cross-sectional view of a portion of an
elongate, rectangular package according to an embodiment. FIG. 4
depicts the packaging system 110 that would be taken along a
section line similar to the section line 3-3' from FIG. 1 and is
analogous in its view to the view taken in FIG. 3. In this
embodiment, an elongate, rectangular die heat spreader 118 has a
symmetry to match an elongate, rectangular die (not pictured). The
elongate, rectangular die is bonded to a likewise elongate,
rectangular interface subsystem 120. It is noted that a collection
of solder islands, such as depicted in FIG. 3, includes solder
islands 124, 124A, and 124B of varying sizes and orientations of
larger and smaller discrete occurrences of the second heat transfer
material 24. The varying sizes and orientations of larger and
smaller discrete occurrences of the second heat transfer material
24 are depicted in FIG. 3 in arbitrary number, shape, size, and
location. As is noted, there are larger solder islands that are
selected to be disposed adjacent to a die at the more active
regions thereof. By way of non-limiting example, a given solder
island 124B that is larger is disposed directly above a more active
region of the die 112 (not pictured) such as an array of embedded
dynamic random access memory (DRAM), the sense amplifiers thereof,
and the like. A more active region of a die is understood to be, in
one embodiment, a region that generates a greater amount of heat
than the average per area heat generation. By placing a larger
solder island above the die at a more active region, a larger
solder island acts as a heat transfer conduit that has a higher
overall heat transfer coefficient than the heat transfer capability
of a smaller solder island, or, for that matter, the first heat
transfer material 122 alone. This larger heat transfer capability
represents a lowered resistance to heat flow between the
heat-generating die and the heat-sinking heat spreader 118. In one
embodiment, the heat spreader 118 includes a lip portion 130
similar to the embodiment depicted in FIGS. 1 and 3.
[0039] FIG. 5 is a cross-sectional view of an interface subsystem
220 according to an embodiment. The interface subsystem 220 of FIG.
5 is similar to the interface subsystem 20 that is depicted in FIG.
1. According to various embodiments, the interface subsystem 220 is
a combination of a low melting-point solder first heat transfer
material 222 and a higher melting-point solder second heat transfer
material 224. As set forth herein, the two heat transfer materials
are selected from a combination of a Pb-containing solder and a
substantially Pb-free solder. In another embodiment, the interface
subsystem 220 includes an organic first heat transfer material 222
and a metallic second heat transfer material 224. As set forth
herein, the first heat transfer material 222 has a first cure
temperature that is lower than the melting point of the second heat
transfer material 224. Similar to other embodiments as set forth
herein, the placement of second heat transfer material 224 as
discrete occurrences thereof may be located above a more active
region of a die in order to expedite heat transfer away from the
die.
[0040] FIG. 6 is a cross-sectional view of an interface system 320
according to an embodiment. Interface subsystem 320 includes an
organic/inorganic composite. In one embodiment, the
organic/inorganic composite includes an organic matrix 322 and a
metal flake 323 along with a second heat transfer material 324.
Although the metal flake 323 is depicted in this embodiment as a
flake, the metal may be in other shapes. In one embodiment, the
metal flake 323 is a substantially spherical powder that has an
average diameter in a range from about 0.1 micron to about 10
micron. The second heat transfer material 324, which is in one
embodiment a high melting-point solder, is either a Pb-containing
solder or a substantially Pb-free solder as set forth herein.
[0041] FIG. 7 is a cross-sectional view of an interface subsystem
420 according to an embodiment. The interface subsystem 420
includes a metal/nonmetal composite in an organic matrix 422. In
one embodiment, the organic matrix 422 includes an organic material
that acts as a matrix for an inorganic dielectric material 421 and
a metallic material 423. In this embodiment, the metallic material
423 is depicted as having reflowed under a thermal load and has at
least partially wetted the inorganic dielectric material 421. The
combination of the inorganic dielectric material 421 and the
metallic material 423 presents a conglomerate channel from one
surface of the interface subsystem 420 to an opposite surface
thereof. As such, heat transfer through the organic matrix material
422 is expedited. Similarly, a high melting-point solder is
depicted in an embodiment as the second heat transfer material
424.
[0042] Another embodiment relates to a die system. An embodiment of
the die system is depicted in some of the structures illustrated in
FIG. 1 by way of non-limiting example. With reference to FIG. 1, in
one embodiment, the die system includes the die 12 and the
interface subsystem 20 as set forth herein according to the various
embodiments. Further, the die system in one embodiment includes the
interface subsystem 20 that is the first heat transfer material 22
alone. In another embodiment, the die system includes the interface
subsystem 20 with the first heat transfer material 22 and the
second heat transfer material 24 disposed in the first heat
transfer material 22. In another embodiment, the die system
includes the second heat transfer material 24 alone that has a
discrete patterning upon the die backside surface 16. The discrete
patterning of the second heat transfer material 24 alone, upon the
die backside surface 16, is a subset embodiment of the packaging
system 10, as depicted in FIG. 1, wherein the discrete patterning
upon the die 12 may be produced by a distinct business entity. For
example, the heat spreader may be produced by a first company or
division within a company, and the die with discrete patterning may
be produced by a second company or division.
[0043] The die system in another embodiment includes the mounting
substrate 26 disposed below the die 12. In other words, the die 12,
the electrical bumps 32, and their bond pads 34 as mounted upon the
mounting substrate 26, represent a package precursor according to
this embodiment. In another embodiment, the die system includes the
mounting substrate 26 and other structures as set forth herein and
the integrated heat spreader 18 disposed above the die 12. As
depicted in FIG. 1, the interface subsystem 20 is disposed between
to the die 12 and the integrated heat spreader 18.
[0044] Another embodiment relates to a thermal interface alone as
depicted in FIG. 1 (interface subsystem 20), FIG. 5 (interface
subsystem 220), FIG. 6 (interface subsystem 320), and FIG. 7
(interface subsystem 420). According to an embodiment, the high
melting-point solder second heat transfer material 24 (FIG. 1, for
example) has at least one solder island that has a characteristic
thickness that is in a range from about 0.1 micron to about 25
micron. The characteristic thickness is selected to achieve a
preferred bond line thickness (BLT) as is understood in the art.
Referring to FIG. 1, the BLT 36 in this embodiment closely tracks
the solder island characteristic thickness, and it is larger than
the solder island characteristic thickness. In other words, the BLT
36 has substantially the same thickness as the interface subsystem
20. In one embodiment, the BLT 36 is in a range from about 1 mil to
about 25 mils. In one embodiment, the BLT 36 is in a range from
about 2 mils to about 10 mils. In another embodiment, the BLT 36 is
in a range from about 10 mils to about 20 mils. In one embodiment,
the BLT 36 of a polymer matrix-containing material is less than the
BLT 36 of a metal matrix-containing material.
[0045] In another embodiment, the high melting-point solder second
heat transfer material 24 (FIG. 1, for example) is present in
relation to the first heat transfer material 22 in a volume range
from about 0.1% to about 5%. In another embodiment, the high
melting-point solder second heat transfer material 24 is present in
relation to the first heat transfer material 22 in a volume range
from about 0% to about 0.1 %. In another embodiment, the high
melting-point solder second heat transfer material 24 is present in
relation to the first heat transfer material 22 in a volume range
from about 0% to about 100%. In another embodiment, the high
melting-point solder second heat transfer material 24 is present in
relation to the first heat transfer material 22 in a volume range
from about 2% to about 10%.
[0046] Another embodiment relates to packaging process embodiments
800 that includes bringing an integrated heat spreader and a die
into TIM intermediary contact through an interface subsystem to
achieve a BLT according to embodiments set forth herein.
[0047] FIG. 8 is a process flow diagram that depicts non-limiting
packaging process embodiments. According to the various process
flow embodiments depicted in FIG. 8, the interface subsystem may be
configured partially on the integrated heat spreader, partially on
the die, entirely on the integrated heat spreader, or entirely on
the die.
[0048] At 810, representing a first process flow embodiment, an
integrated heat spreader (IHS) is contacted with a first heat
transfer material, and the first heat transfer material is
contacted with a die. The double-headed arrows in FIG. 8 indicate
that the process flow may be in either direction. In other words,
the first heat transfer material in one embodiment is disposed
first against the integrated heat spreader, followed by disposition
of the first heat transfer material against the die. Alternatively,
the first heat transfer material in one embodiment is disposed
first against the die, followed by disposition of the first heat
transfer material against the integrated heat spreader.
[0049] At 820, representing a second process flow embodiment, an
integrated heat spreader is contacted with a first heat transfer
material. The first heat transfer material is contacted with a
second heat transfer material that is disposed on a die. The
double-headed arrows indicate alternative process flows as set
forth above.
[0050] At 830, representing a third process flow embodiment, an
integrated heat spreader is contacted with a second heat transfer
material. The second heat transfer material is contacted with a
first heat transfer material that is disposed on a die. The
double-headed arrows indicate alternative process flows as set
forth above.
[0051] At 840, representing a fourth process flow embodiment, an
integrated heat spreader is contacted with combined first and
second heat transfer materials. The combined first and second heat
transfer materials are contacted with a die. The double-headed
arrows indicate alternative process flows as set forth above. In
another embodiment, the order of placing the first and second heat
transfer materials onto the IHS is reversed.
[0052] At 850, representing a fifth process flow embodiment, a die
is contacted with combined first and second heat transfer
materials. The combined first and second heat transfer materials
are contacted with a die. The double-headed arrows indicate
alternative process flows as set forth above. In another
embodiment, the order of placing the first and second heat transfer
materials onto the die is reversed.
[0053] As depicted in the various process flow embodiments depicted
in FIG. 8, it is noted that the die 12 (FIG. 1) is previously
disposed upon a mounting substrate 26 (also FIG. 1). Further as
depicted in FIG. 1, it is noted that an integrated heat spreader
clip 38 is used to impart a pressure to the die-interface-heat
spreader at least partially through a spring 40. Depending upon the
combination of interface subsystem 20 and other factors such as
adhesive gelling time, organic curing time, low melting-point
reflow time, and others, the exact tension of the spring 40 is
selected to the requirements of a given packaging system.
[0054] According to an embodiment, the bonding process of bringing
an integrated heat spreader and a die into intermediary contact
through an interface subsystem 20, 120, 220, 320, or 420 is
referred to as a die-referenced process. The die-referenced process
relates to the situation that the die 12 is already affixed upon
the mounting substrate 26. And as in some embodiments, a second
heat transfer material 24 is disposed between the integrated heat
spreader 18 and the backside surface 16 of the die 12 while tensing
the system with the spring 40. Accordingly, the variability in
bonding thickness may often largely be in the bonding material 28
as it bridges the space between the lip 30 of the integrated heat
spreader 18 and the mounting substrate 26.
[0055] In a general embodiment, after bringing the integrated heat
spreader into intermediary contact with the die through the
interface subsystem according to various embodiments, bonding the
interface subsystem includes reflowing the low melting-point solder
first heat transfer material, and/or curing an organic first heat
transfer material. Additionally, where a second heat transfer
material is disposed in a first heat transfer material, the solder
reflowing process is carried out after bringing the structures
together. Where the first heat transfer material is an organic
material, a curing and/or hardening process is carried out after
bringing the structures together. Where the first heat transfer
material is an organic/inorganic composite, curing, hardening,
and/or reflowing is carried out after bringing the structures
together.
[0056] It is emphasized that the Abstract is provided to comply
with 37 C.F.R. .sctn. 1.72(b) requiring an Abstract that will allow
the reader to quickly ascertain the nature and gist of the
technical disclosure. It is submitted with the understanding that
it will not be used to interpret or limit the scope or meaning of
the claims.
[0057] In the foregoing Detailed Description, various features are
grouped together in a single embodiment for the purpose of
streamlining the disclosure. This method of disclosure is not to be
interpreted as reflecting an intention that the claimed embodiments
of the invention require more features than are expressly recited
in each claim. Rather, as the following claims reflect, inventive
subject matter lies in less than all features of a single disclosed
embodiment. Thus the following claims are hereby incorporated into
the Detailed Description of Embodiments of the Invention, with each
claim standing on its own as a separate preferred embodiment.
[0058] It will be readily understood to those skilled in the art
that various other changes in the details, material, and
arrangements of the parts and method stages which have been
described and illustrated in order to explain the nature of this
invention may be made without departing from the principles and
scope of the invention as expressed in the subjoined claims.
* * * * *