U.S. patent application number 15/885115 was filed with the patent office on 2019-08-01 for cooling bond layer and power electronics assemblies incorporating the same.
The applicant listed for this patent is Toyota Motor Engineering & Manufacturing North America, Inc.. Invention is credited to Ercan Mehmet Dede, Shailesh N. Joshi.
Application Number | 20190237389 15/885115 |
Document ID | / |
Family ID | 67392898 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190237389 |
Kind Code |
A1 |
Joshi; Shailesh N. ; et
al. |
August 1, 2019 |
COOLING BOND LAYER AND POWER ELECTRONICS ASSEMBLIES INCORPORATING
THE SAME
Abstract
A cooling bond layer for a power electronics assembly is
provided. The cooling bond layer includes a first end, a second end
spaced apart from the first end, a metal matrix extending between
the first end and the second end, and a plurality of micro-channels
extending through the metal matrix from the first end to the second
end. The plurality of micro-channels are configured for a cooling
fluid to flow through and remove heat from the cooling bond layer.
In some embodiments, the plurality of micro-channels are
cylindrical shaped micro-channels. In such embodiments, the
plurality of micro-channels may have a generally constant average
inner diameter along a thickness of the cooling bond layer. In the
alternative, the plurality of micro-channels may have a graded
average inner diameter along a thickness of the cooling bond layer.
In other embodiments, the plurality of micro-channels may have a
wire mesh layered structure.
Inventors: |
Joshi; Shailesh N.; (Ann
Arbor, MI) ; Dede; Ercan Mehmet; (Ann Arbor,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toyota Motor Engineering & Manufacturing North America,
Inc. |
Erlanger |
KY |
US |
|
|
Family ID: |
67392898 |
Appl. No.: |
15/885115 |
Filed: |
January 31, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/29113
20130101; H01L 2224/292 20130101; H01L 2224/29299 20130101; H01L
2224/48137 20130101; H01L 2224/293 20130101; H01L 21/4871 20130101;
H01L 24/48 20130101; H01L 23/473 20130101; H01L 2224/27462
20130101; H01L 2224/29016 20130101; H01L 24/83 20130101; H01L
2924/19107 20130101; H01L 2224/27464 20130101; H01L 2224/2908
20130101; H01L 2924/13055 20130101; H01L 2224/2929 20130101; H01L
2924/0695 20130101; H01L 23/147 20130101; H01L 2224/83193 20130101;
H01L 23/49861 20130101; H01L 2224/831 20130101; H01L 2224/83801
20130101; H01L 2224/8382 20130101; H01L 2924/13091 20130101; H01L
2224/27001 20130101; H01L 24/32 20130101; H01L 2224/05655 20130101;
H01L 2224/27849 20130101; H01L 2224/29076 20130101; H01L 2224/29155
20130101; H01L 2224/3201 20130101; H01L 2224/29147 20130101; H01L
2224/29082 20130101; H01L 2224/8384 20130101; H01L 24/73 20130101;
H01L 2224/29111 20130101; H01L 21/4882 20130101; H01L 2224/04026
20130101; H01L 2224/29109 20130101; H01L 2224/29199 20130101; H01L
24/27 20130101; H01L 24/29 20130101; H01L 2224/29139 20130101; H01L
23/4735 20130101; H01L 2224/29005 20130101; H01L 2924/014 20130101;
H01L 2224/32225 20130101; H01L 23/467 20130101; H01L 2224/2919
20130101; H01L 2224/32245 20130101; H01L 2224/32505 20130101; H01L
2224/83815 20130101; H01L 2924/1203 20130101; H01L 2224/29011
20130101; H01L 2224/73265 20130101; H01L 2924/07025 20130101; H01L
2224/29111 20130101; H01L 2924/014 20130101; H01L 2924/01049
20130101; H01L 2924/01047 20130101; H01L 2224/29111 20130101; H01L
2924/014 20130101; H01L 2924/01083 20130101; H01L 2924/01029
20130101; H01L 2224/29111 20130101; H01L 2924/014 20130101; H01L
2924/01047 20130101; H01L 2924/01029 20130101; H01L 2224/2919
20130101; H01L 2924/07025 20130101; H01L 2224/2919 20130101; H01L
2924/0695 20130101; H01L 2224/292 20130101; H01L 2924/00014
20130101; H01L 2224/29299 20130101; H01L 2924/00014 20130101; H01L
2224/05655 20130101; H01L 2924/00014 20130101; H01L 2224/29155
20130101; H01L 2924/00014 20130101; H01L 2224/29199 20130101; H01L
2924/00014 20130101; H01L 2224/293 20130101; H01L 2924/014
20130101; H01L 2924/00014 20130101 |
International
Class: |
H01L 23/473 20060101
H01L023/473; H01L 23/467 20060101 H01L023/467; H01L 21/48 20060101
H01L021/48; H01L 23/00 20060101 H01L023/00 |
Claims
1. A bond layer for a power electronics assembly comprising: a
cooling bond layer comprising: a first end and a second end spaced
apart from the first end; a metal matrix extending between the
first end and the second end; and a plurality of micro-channels
extending through the metal matrix from the first end to the second
end; wherein the plurality of micro-channels extend from the first
end to the second end of the cooling bond layer and comprise one of
a constant average inner diameter or a graded average inner
diameter as a function of a thickness of the cooling bond layer,
and wherein the plurality of micro-channels are configured for a
cooling fluid to flow through and remove heat from the cooling bond
layer.
2. The bond layer of claim 1, wherein the plurality of
micro-channels comprise a plurality of cylindrical shaped
micro-channels.
3. (canceled)
4. (canceled)
5. The bond layer of claim 2, wherein the plurality of cylindrical
shaped micro-channels comprise a plurality of tubes extending
through the metal matrix.
6. The bond layer of claim 1, wherein the plurality of
micro-channels comprises a wire mesh structure.
7. The bond layer of claim 1, further comprising a pair of low
melting point bond layers, wherein the cooling bond layer is
sandwiched between the pair of low melting point bond layers.
8. The bond layer of claim 7, wherein: the cooling bond layer has a
melting point above a sintering temperature; the pair of low
melting point bond layers each have a melting point below the
sintering temperature; and the sintering temperature is in a range
between about 280.degree. C. and 350.degree. C.
9. A power electronics assembly comprising: a substrate; a
semiconductor device; and a cooling bond layer disposed between and
bonded to the semiconductor device and the substrate, the cooling
bond layer comprising a first end and a second end spaced apart
from the first end, a metal matrix extending between the first end
and the second end, and a plurality of micro-channels extending
through the metal matrix from the first end to the second end,
wherein the plurality of micro-channels extend from the first end
to the second end of the cooling bond layer and comprise one of a
constant average inner diameter or a graded average inner diameter
as a function of a thickness of the cooling bond layer; and a
cooling fluid circuit extending through the cooling bond layer, the
cooling fluid circuit comprising the plurality of
micro-channels.
10. The power electronics assembly of claim 9, wherein the
plurality of micro-channels comprise a plurality of cylindrical
shaped micro-channels.
11. (canceled)
12. The power electronics assembly of claim 10, wherein the
plurality of cylindrical shaped micro-channels comprise a plurality
of oxide coating tubes extending through the metal matrix.
13. The power electronics assembly of claim 9, wherein the
plurality of micro-channels comprise a wire mesh structure.
14. The power electronics assembly of claim 9, wherein the metal
matrix is formed from tin, aluminum, nickel, copper, magnesium, or
alloys thereof.
15. A process for manufacturing a power electronics assembly
comprising: positioning a template for a plurality of
micro-channels between a substrate and a semiconductor device;
depositing a metal or an alloy around the template and forming a
metal matrix, wherein the metal matrix is bonded to the substrate
and the semiconductor device; removing the template from the metal
matrix and forming a cooling bond layer disposed between and bonded
to the semiconductor device and the substrate, the cooling bond
layer comprising a first end, a second end spaced apart from the
first end and the metal matrix extending between the first end and
the second end, and the plurality of micro-channels extending
through the metal matrix from the first end to the second end,
wherein the plurality of micro-channels extend from the first end
to the second end of the cooling bond layer and comprise one of a
constant average inner diameter or a graded average inner diameter
as a function of a thickness of the cooling bond layer, and wherein
the plurality of micro-channels are configured for a cooling fluid
to flow through and remove heat from the cooling bond layer and
form at least part of a cooling fluid circuit for the power
electronics assembly.
16. The process of claim 15, wherein the metal or the alloy is
deposited around the template by electrolytic deposition or
electroless deposition and the cooling bond layer is bonded to the
substrate and the semiconductor device via the electrolytic
deposition or the electroless deposition.
17. The process of claim 15, wherein the template of the plurality
of micro-channels comprises a plurality of cylindrical shaped
members.
18. The process of claim 17, wherein the template is removed via
etching of the plurality of cylindrical shaped members out of the
metal matrix.
19. The process of claim 17, wherein the template is removed by
applying a mechanical force onto the plurality of cylindrical
shaped members.
20. The process of claim 15, wherein the template of the cooling
bond layer comprises a plurality of wire mesh layers.
Description
TECHNICAL FIELD
[0001] The present specification generally relates to bonding
materials, and more particularly, to bonding materials that bond
semiconductor devices to substrates and provide cooling of the
semiconductor devices.
BACKGROUND
[0002] Power electronics devices are often utilized in high-power
electrical applications, such as inverter systems for hybrid
electric vehicles and electric vehicles. Such power electronics
devices include power semiconductor devices such as power IGBTs and
power transistors thermally bonded to a substrate. The substrate
may then be further bonded to a cooling structure, such as a heat
sink. With advances in battery technology and increases in
electronics device packaging density, operating temperatures of
power electronics devices have increased and are currently
approaching 200.degree. C. which require increasing the size of the
cooling structures. Accordingly, alternative cooling structures for
power electronics devices are desired.
SUMMARY
[0003] In one embodiment, a cooling bond layer for a power
electronics assembly includes a first end, a second end spaced
apart from the first end, a metal matrix extending between the
first end and the second end, and a plurality of micro-channels
extending through the metal matrix from the first end to the second
end. The plurality of micro-channels are configured for a cooling
fluid to flow through and remove heat from the cooling bond layer.
In some embodiments, the plurality of micro-channels are
cylindrical shaped micro-channels. In such embodiments, the
plurality of micro-channels may have a generally constant average
inner diameter as a function of a thickness of the cooling bond
layer. In the alternative, the plurality of micro-channels may have
a graded average inner diameter as a function of the thickness of
the cooling bond layer. In other embodiments, the plurality of
micro-channels may be in the form of a wire mesh layer.
[0004] In another embodiment, a power electronics assembly includes
a substrate, a semiconductor device, and a cooling bond layer
disposed between and bonded to the semiconductor device and the
substrate. The cooling bond layer includes a first end and a second
end spaced apart from the first end, a metal matrix extending
between the first end and the second end, and a plurality of
micro-channels extending through the metal matrix from the first
end to the second end. A cooling fluid circuit extending through
the cooling bond layer may be included and be configured to remove
heat transferred to the cooling bond layer from the semiconductor
device. In some embodiments, the plurality of micro-channels are
cylindrical shaped micro-channels. In such embodiments, the
plurality of micro-channels may have a generally constant average
inner diameter as a function of a thickness of the cooling bond
layer. In the alternative, the plurality of micro-channels may have
a graded average inner diameter as a function of the thickness of
the cooling bond layer. In other embodiments, the plurality of
micro-channels may be in the form or a wire mesh layer. The metal
matrix of the cooling bond layer may be formed by reflow soldering
in which a liquid soldering material flows and solidifies around a
template. The template may have the shape or form of the plurality
of micro-channels and may be removed from the metal matrix to form
the plurality of micro-channels.
[0005] In yet another embodiment, a process for manufacturing a
power electronics assembly includes positioning a template and
soldering material between a substrate and a semiconductor device,
forming a metal matrix around the template, and bonding the
substrate to the semiconductor device. The template is removed from
the metal matrix to form a cooling bond layer with a plurality of
micro-channels within the metal matrix. The cooling bond layer
includes a first end, a second end spaced apart from the first end,
and the metal matrix extends between the first end and the second
end. Also, the plurality of micro-channels extend through the metal
matrix from the first end to the second end and are configured for
cooling fluid to flow there through. In some embodiments, the metal
matrix if formed by a reflow soldering process. The template may
include a plurality of cylindrical shaped members that are removed
from the metal matrix using a mechanical force. In the alternative,
or in addition to, the template may include a plurality of tubes
that are not removed from the metal matrix.
[0006] These and additional features provided by the embodiments
described herein will be more fully understood in view of the
following detailed description, in conjunction with the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The embodiments set forth in the drawings are illustrative
and exemplary in nature and not intended to limit the subject
matter defined by the claims. The following detailed description of
the illustrative embodiments can be understood when read in
conjunction with the following drawings, where like structure is
indicated with like reference numerals and in which:
[0008] FIG. 1 schematically depicts a side view of a power
electronics assembly having a power semiconductor device bonded to
a substrate with a cooling bond layer according to one or more
embodiments shown and described herein;
[0009] FIG. 2A schematically depicts an exploded side view of the
cooling bond layer in FIG. 1 according to one or more embodiments
shown and described herein;
[0010] FIG. 2B schematically depicts a view of section 2B-2B in
FIG. 2A;
[0011] FIG. 3 schematically depicts the cooling bond layer in FIG.
2A bonded to the power electronics assembly according to one or
more embodiments shown and described herein;
[0012] FIG. 4 schematically depicts an isolated perspective view of
the cooling bond layer in FIG. 3 with cooling fluid and electrical
current passing through the cooling bond layer;
[0013] FIG. 5 schematically depicts a view of section 2B-2B layer
in FIG. 2A according to one or more embodiments shown and described
herein;
[0014] FIG. 6 schematically depicts a view of section 2B-2B layer
in FIG. 2A according to one or more embodiments shown and described
herein;
[0015] FIG. 7 schematically depicts a view of section 2B-2B layer
in FIG. 2A according to one or more embodiments shown and described
herein;
[0016] FIG. 8 schematically depicts a view of section 2B-2B layer
in FIG. 2A according to one or more embodiments shown and described
herein;
[0017] FIG. 9A schematically depicts a top view of a template for a
plurality of micro-channels in a cooling bond layer according to
one or more embodiments shown and described herein;
[0018] FIG. 9B schematically depicts an exploded side view of the
cooling bond layer in FIG. 1 formed using the template in FIG. 9A
according to one or more embodiments shown and described
herein;
[0019] FIG. 9C schematically depicts a view of section 9B-9B layer
in FIG. 9A;
[0020] FIG. 10 schematically depicts the cooling bond layer in FIG.
9B bonded to the power electronics assembly according to one or
more embodiments shown and described herein;
[0021] FIG. 11A schematically depicts a side cross section view of
the cooling bond layer in FIG. 1 according to one or more
embodiments shown and described herein;
[0022] FIG. 11B schematically depicts a top view of the cooling
bond layer in FIG. 11A according to one or more embodiments shown
and described herein;
[0023] FIG. 12A schematically depicts a side view of a process for
forming the power electronics assembly in FIG. 1 with the cooling
bond layer in FIG. 2A according to one or more embodiments shown
and described herein;
[0024] FIG. 12B schematically depicts an end view of the process in
FIG. 12A;
[0025] FIG. 13A schematically depicts a side view of a process for
forming the power electronics assembly in FIG. 1 with the cooling
bond layer in FIG. 9B according to one or more embodiments shown
and described herein;
[0026] FIG. 13B schematically depicts an end view of the process in
FIG. 13A;
[0027] FIG. 14A schematically depicts a side view of a process for
forming the power electronics assembly in FIG. 1 with the cooling
bond layer in FIG. 11A according to one or more embodiments shown
and described herein;
[0028] FIG. 14B schematically depicts an end view of the process in
FIG. 14A; and
[0029] FIG. 15 schematically depicts a vehicle having a plurality
of power electronics assemblies according to one or more
embodiments shown and described herein.
DETAILED DESCRIPTION
[0030] A power electronics assembly with a power semiconductor
device (semiconductor device) bonded to a substrate with a cooling
bond layer is provided. As used herein, the term "cooling bond
layer" refers to a bond layer disposed between and bonded to a
semiconductor device and a substrate, wherein the bond layer is
configured to extract heat from the semiconductor device via the
flow of a cooling fluid through the bond layer. The cooling bond
layer comprises a first end, a second end spaced apart from the
first end, a metal matrix extending between the first end and the
second end, and a plurality of micro-channels extending through the
metal matrix. As used herein, the phrase "metal matrix" refers to a
generally non-porous metal or alloy layer extending between the
plurality of micro-channels and the term "micro-channels" refers to
hollow passageways with an internal dimension less than 1000
micrometers (.mu.m) that extend through the metal matrix. The metal
matrix of the cooling bond layer may be formed by flowing a liquid
soldering material around a template, e.g., using a reflow
soldering process. The term "template" as used herein refers to a
physical form or object that provides a pattern within the metal
matrix. The template and a soldering material (solid) may be
positioned between a semiconductor device and a substrate and the
metal matrix may be formed and bonded to the semiconductor device
and the substrate during forming of the metal matrix around the
template. The template may be removed from the metal matrix thereby
providing the plurality of micro-channels. That is, the template
may be a sacrificial matrix for the plurality of micro-channels. A
cooling fluid circuit comprising the cooling bond layer may be
configured for a cooling fluid to flow through the plurality of
micro-channels and assist in removing heat from the semiconductor
device during operation of the power electronics assembly. The
cooling bond layer may also provide an electrical conduit (i.e.,
electrical contact) between the semiconductor device and the
substrate. Various embodiments of cooling bond layers and power
electronics assemblies using cooling bond layers will be described
in more detail herein.
[0031] Referring initially to FIG. 1, as a non-limiting example, a
power electronics assembly 100 is schematically illustrated. The
power electronics assembly 100 generally comprises a substrate 110,
two semiconductor devices 120 bonded to the substrate 110 via a
cooling bond layer 130, a cooling structure 140, and a package
housing 102.
[0032] The thicknesses of the substrate 110 and the semiconductor
devices 120 may depend on the intended use of the power electronics
assembly 100. In one embodiment, the substrate 110 has a thickness
within the range of about 2.0 mm to about 4.0 mm, and the
semiconductor device 120 has a thickness within the range of about
0.1 mm to about 0.3 mm. For example and without limitation, the
substrate 110 may have a thickness of about 3.0 mm and the
semiconductor device 120 may have a thickness of about 0.2 mm. It
should be understood that other thicknesses may be utilized.
[0033] The substrate 110 may be formed from a thermally conductive
material such that heat from the semiconductor devices 120 is
transferred to the cooling structure 140. The substrate 110 may any
type of substrate for power semiconductor device assemblies known
to those skilled in the art. Non-limiting examples include metal
substrates, e.g., substrates formed from copper (Cu), e.g., oxygen
free Cu, aluminum (Al), Cu alloys, Al alloys, and the like, direct
bonded copper substrates or semiconductor (e.g., silicon)
substrates. The semiconductor devices 120 may be formed from a wide
band gap semiconductor material suitable for the manufacture or
production of power semiconductor devices such as power
insulated-gate bipolar transistors (IGBTs) and power transistors.
In embodiments, the semiconductor devices 120 may be formed from
wide band gap semiconductor materials including without limitation
silicon carbide (SiC), silicon dioxide (SiO.sub.2), aluminum
nitride (AlN), gallium nitride (GaN), boron nitride (BN), diamond,
and the like. In embodiments, the substrate 110 and the
semiconductor devices 120 may comprise a coating, e.g., nickel (Ni)
plating, to assist in the TLP sintering of the semiconductor
devices 120 to the substrate 110 as discussed in greater detail
below.
[0034] As depicted in FIG. 1, a substrate 110 is bonded to two
semiconductor devices 120 via the cooling bond layer 130. More or
fewer semiconductor devices 120 may be attached to the substrate
110. In some embodiments, heat generating devices other than power
semiconductor devices may be attached to the substrate 110. The
semiconductor devices 120 may be power semiconductor devices such
as IGBTs, power diodes, power metal-oxide-semiconductor
field-effect transistors (MOSFETs), power transistors, and the
like. In one embodiment, the semiconductor devices 120 of one or
more power electronics assemblies are electrically coupled to form
an inverter circuit or system for vehicular applications, such as
for hybrid vehicles or electric vehicles, for example.
[0035] The substrate 110 may be thermally coupled to the cooling
structure 140 via a bond layer 138. In one embodiment, the cooling
structure 140 comprises an air-cooled heat sink. In an alternative
embodiment, the cooling structure 140 comprises a liquid-cooled
heat sink, such as a jet impingement or channel-based heat sink
device that may be in fluid communication with the cooling bond
layer 130. The substrate 110 of the illustrated embodiment is
directly bonded to a first surface 142 of the cooling structure 140
via the bond layer 138 without any additional interface layers
(e.g., additional metal base plates). The substrate 110 may be
bonded to the cooling structure 140 using a variety of bonding
techniques, such as by TLP sintering, solder, brazing, or diffusion
bonding, for example. However, in an alternative embodiment, one or
more thermally conductive interface layers may be positioned
between the substrate 110 and the cooling structure 140. In another
alternative embodiment, the power electronics assembly 100 does not
include the cooling structure 140. That is, the cooling bond layer
130 removes sufficient heat from the semiconductor device 120 such
that the cooling structure 140 is not needed.
[0036] Still referring to FIG. 1, the substrate 110 may be
maintained within a package housing 102, which may be made of a
non-electrically conductive material such as plastic, for example.
The package housing 102 may be coupled to the cooling structure 140
by a variety of mechanical coupling methods, such as by the use of
fasteners or adhesives, for example. In other embodiments, the
package housing 102 may be coupled to the substrate 110. In still
other embodiments, no package housing is provided.
[0037] Within the power electronics assembly 100 may be a first
electrical contact 104a and a second electrical contact 104b to
provide electrical power connections to the semiconductor devices
120. The first electrical contact 104a may correspond to a first
voltage potential and the second electrical contact 104b may
correspond to a second voltage potential. In the illustrated
embodiment, the first electrical contact 104a is electrically
coupled to a first surface of the semiconductor devices 120 via a
first electrical wire 121a, and the second electrical contact 104b
is electrically coupled to a second surface of the semiconductor
devices 120 via a second electrical wire 121b and the substrate
110. It should be understood that other electrical and mechanical
configurations are possible, and that embodiments are not limited
by the arrangement of the components illustrated in the
figures.
[0038] Referring now to FIGS. 2A-2B, an exploded side view of the
region designated by box 150 in FIG. 1 before bonding the
semiconductor devices 120 to the substrate 110 is schematically
depicted in FIG. 2A and a view of section 2B-2B in FIG. 2A is
schematically depicted in FIG. 2B. In embodiments, the substrate
110 is bonded to the semiconductor device 120 via reflow soldering
to form and solder the cooling bond layer 130 to the substrate 110
and the semiconductor device 120 as discussed in more detail below
with reference to FIGS. 12A-12B. It should be understood that other
bonding techniques and processes may be utilized to form and bond
the cooling bond layer 130 to the substrate 110 and the
semiconductor device 120. The cooling bond layer 130 includes a
lower surface 131, an upper surface 133, a first end 132, and a
second end 134 spaced apart (+X direction) from the first end 132.
The cooling bond layer 130 includes a metal matrix 136 with a
plurality of tubeless micro-channels 137 disposed within the metal
matrix 136 and extending from the first end 132 to the second end
134. As used herein, the phrase "tubeless micro-channel" refers to
a micro-channel without a tube between the metal matrix and the
hollow passageway of the micro-channel. In embodiments, the cooling
bond layer 130 may be disposed between and in direct contact with
the substrate 110 and the semiconductor device 120 as depicted in
FIG. 3. Accordingly, the lower surface 131 of the cooling bond
layer 130 may be in direct contact with the substrate 110 and the
upper surface 133 may be in direct contact with the semiconductor
device 120. In other embodiments, the cooling bond layer 130 may be
disposed between but not be in direct contact with the substrate
110 and the semiconductor device 120. That is, one or more
additional layers may be disposed between the lower surface 131 of
the cooling bond layer 130 and the substrate 110 and/or one or more
additional layers may be disposed between the upper surface 133 and
the semiconductor device 120.
[0039] In some embodiments, the plurality of tubeless
micro-channels 137 may be cylindrical shaped micro-channels with a
circular cross-section (Y-Z plane) and an average inner diameter
`4:11` as depicted in FIG. 2B. In other embodiments (not shown),
the plurality of tubeless micro-channels 137 may not be cylindrical
shaped and may have a square cross-section, a rectangular
cross-section, an elliptical cross-section, and the like. As
depicted in FIGS. 2A-2B, in some embodiments, the plurality of
tubeless micro-channels 137 may be regularly spaced apart from each
other in the form of an array. As used herein, the term "array"
refers to a pattern of micro-channels arranged in rows and/or
columns within a metal matrix with equal distances between the rows
and/or columns. In such embodiments, the plurality of tubeless
micro-channels 137 may be in the form of two or more different
arrays. In other embodiments, the plurality of tubeless
micro-channels 137 may not be in the form of an array, i.e., the
plurality of tubeless micro-channels 137 may not be regularly
spaced apart from each other. In still other embodiments, a first
portion of the plurality of tubeless micro-channels 137 may be in
the form of an array and a second portion of the plurality of
tubeless micro-channels 137 may not be in the form of an array. As
depicted in FIG. 3, a cooling fluid `CF` may flow through the
plurality of tubeless micro-channels 137 as part of a cooling fluid
circuit 135 comprising the cooling bond layer 130 for the power
electronics assembly 100. Non-limiting examples of the cooling
fluid CF include dielectric cooling fluids such as aromatics,
silicate-ester, aliphatics, silicones, fluorocarbons, and the
like.
[0040] Referring now to FIG. 4, one non-limiting example of the
cooling bond layer 130 providing an electrical conduit (i.e.,
electrical contact) between a semiconductor device and a substrate
is schematically depicted. Particularly, an isolated perspective
view of the cooling bond layer 130 shown in FIG. 3 is depicted with
cooling fluid CF flowing through the plurality of tubeless
micro-channels 137 and an electrical current T flowing from the
upper surface 133 to the lower surface 131. That is, electrical
current may flow between the semiconductor device 120 bonded to the
upper surface 133 and the substrate 110 bonded to the lower surface
131 of the cooling bond layer 130. It should be understood the
cooling fluid CF may be a dielectric fluid such that the current i
flows around the plurality of tubeless micro-channels 137 as
depicted in FIG. 4. Accordingly, the cooling bond layer 130
provides cooling and electrical connectivity for the power
electronics assembly 100.
[0041] While FIGS. 2A, 2B, 3 and 4 depict the plurality of tubeless
micro-channels 137 having a generally constant average inner
diameter d1 as a function of the thickness (Y direction) of the
cooling bond layer 130, in some embodiments, the plurality of
tubeless micro-channels 137 may have a graded inner diameter as a
function of the thickness (Y direction) of the cooling bond layer
130 as depicted in FIGS. 5-8. For example, FIG. 5 depicts one
non-limiting example with four rows of tubeless micro-channels 137
having increasing average inner diameters as a function of the
thickness (+Y direction) of the cooling bond layer 130.
Particularly, a row of tubeless micro-channels 137 closest to the
lower surface 131 (first row) has an average inner diameter of
`4:11`, a row of tubeless micro-channels 137 just above (+Y
direction) the first row (second row) has an average inner diameter
of `4:12` greater than d1, a row of tubeless micro-channels 137
just above (+Y direction) the second row (third row) has an average
inner diameter of `d3` greater than d2, and a row of tubeless
micro-channels 137 just above (+Y direction) the third row (fourth
row) has an average inner diameter of `4:14` greater than d3 (i.e.,
d1<d2<d3<d4). Accordingly, FIG. 5 depicts a plurality of
tubeless micro-channels 137 with an increasing graded average inner
diameter as a function of the thickness of the cooling bond layer
130 from the lower surface 131 to the upper surface 133. Referring
now to FIG. 6, another non-limiting example with four rows of
tubeless micro-channels 137 having decreasing average inner
diameters as a function of the thickness (+Y direction) of the
cooling bond layer 130 is depicted. Particularly, the first row of
tubeless micro-channels 137 has an average inner diameter of
`4:11`, the second row of tubeless micro-channels 137 has an
average inner diameter of `4:12` less than d1, the third row of
tubeless micro-channels 137 has an average inner diameter of `d3`
less than d2, and the fourth row of tubeless micro-channels 137 has
an average inner diameter of `d4` less than d3 (i.e.,
d1>d2>d3>d4). Accordingly, FIG. 6 depicts a plurality of
tubeless micro-channels 137 with a decreasing graded average inner
diameter as a function of the thickness of the cooling bond layer
130 from the lower surface 131 to the upper surface 133 of the
cooling bond layer 130.
[0042] Referring now to FIG. 7, a non-limiting example with five
rows of tubeless micro-channels 137 comprising a central or middle
row of tubeless micro-channels 137 having an average inner diameter
that is greater than an average inner diameter of outer rows of
tubeless micro-channels 137 is depicted. Particularly, a pair of
first rows of tubeless micro-channels 137 closest to the lower
surface 131 and the upper surface 133 have an average inner
diameter of `4:11`, a pair of second rows of tubeless
micro-channels 137 next to the pair of first rows of tubeless
micro-channels 137 have an average inner diameter of `4:12` that is
equal to d1, and a middle row of tubeless micro-channels 137 has an
average inner diameter of `d3` that is greater than d1 and d2
(i.e., d1 =d2<d3). Accordingly, FIG. 7 depicts the plurality of
tubeless micro-channels 137 with an increasing graded average inner
diameter as a function of thickness from the lower surface 131 to
the middle or center of the cooling bond layer 130 (+Y direction),
and from the upper surface 133 to the middle or center of the
cooling bond layer 130 (-Y direction). Referring now to FIG. 8, a
non-limiting example with four rows of tubeless micro-channels 137
comprising a pair of outer rows of tubeless micro-channels 137
having an average inner diameter that is greater than an average
inner diameter of a pair of inner rows of tubeless micro-channels
137 is depicted. Particularly, a pair of first rows of tubeless
micro-channels 137 closest to the lower surface 131 and the upper
surface 133 have an average inner diameter of `4:11`, and a pair of
middle rows of tubeless micro-channels 137 have an average inner
diameter of `d2` that is less than d1 (i.e., d1>d2).
Accordingly, FIG. 8 depicts a plurality of tubeless micro-channels
137 with a decreasing graded average inner diameter as a function
of thickness from the lower surface 131 to the middle or center of
the cooling bond layer 130 (+Y direction), and from the upper
surface 133 to the middle or center of the cooling bond layer 130
(-Y direction).
[0043] It should be understood that other configurations and
examples of the arrangement and average inner diameters of the
plurality of tubeless micro-channels 137 may be used to provide a
cooling fluid circuit comprising a cooling bond layer. Also, and as
noted above, the average inner diameter of the plurality of
tubeless micro-channels 137 may be less than 1000 .mu.m. For
example, the average inner diameter of the plurality of tubeless
micro-channels 137 may be between about 10 .mu.m and about 750
.mu.m. In some embodiments, the average inner diameter of the
plurality of tubeless micro-channels 137 may be between about 50
.mu.m and about 500 .mu.m, for example between about 75 .mu.m and
about 250 .mu.m.
[0044] Referring now to FIGS. 9A-9C and 10, a non-limiting example
of a cooling bond layer with non-cylindrical shaped micro-channels
is schematically depicted. Particularly, FIG. 9A schematically
depicts a top view of a wire mesh layer 237' used as a template for
a plurality of micro-channels 237 in a cooling bond layer 230
depicted in FIGS. 9B-9C and 10. That is, one or more wire mesh
layers 237' may be disposed within a metal matrix 236 and then
removed to provide a plurality of micro-channels 237 in the form of
the wire mesh layers 237'. As used herein the phrase "wire mesh
layer" refers to of layer with a mesh structure and not to the
material from which the layer is formed. For example, non-limiting
examples of materials from which the wire mesh layer 237' is formed
include polymers such as nylon, polyimides, polyamide-imides, and
the like.
[0045] Referring specifically to FIG. 9B-9C an exploded side view
of the region designated by box 150 in FIG. 1 before bonding the
semiconductor devices 120 to the substrate 110 is schematically
depicted in FIG. 9B and an end view of section 9C-9C in FIG. 9B is
schematically depicted in FIG. 9C. In embodiments, the substrate
110 is bonded to the semiconductor device 120 via reflow soldering
to form and bond the cooling bond layer 230 to the substrate 110
and to the semiconductor device 120 as discussed in more detail
below. The cooling bond layer 230 includes a lower surface 231, an
upper surface 233, a first end 232, and a second end 234 spaced
apart (+X direction) from the first end 232. The cooling bond layer
230 includes a metal matrix 236 with a plurality of micro-channels
237 disposed within the metal matrix 236 and extending from the
first end 232 to the second end 234. As depicted in FIG. 10, a
cooling fluid `CF` may flow through the plurality of micro-channels
237 as part of a cooling fluid circuit 235 comprising the cooling
bond layer 230 for the power electronics assembly 100.
[0046] In embodiments, the cooling bond layer 230 may be disposed
between and in direct contact with the substrate 110 and the
semiconductor device 120. Accordingly, the lower surface 231 of the
cooling bond layer 230 may be in direct contact with the substrate
110 and the upper surface 233 may be in direct contact with the
semiconductor device 120 (FIG. 10). In other embodiments, the
cooling bond layer 230 may be disposed between but not be in direct
contact with the substrate 110 and the semiconductor device 120.
That is, one or more additional layers may be disposed between the
lower surface 231 of the cooling bond layer 230 and the substrate
110 and/or one or more additional layers may be disposed between
the upper surface 233 and the semiconductor device 120.
[0047] While FIGS. 9B, 9C and 10 schematically depicted the
plurality of micro-channels 237 having a generally constant
thickness (Y direction) as a function of the thickness of the
cooling bond layer 230, it should be understood that other
configurations and examples of the thickness, pattern, etc., of the
plurality of micro-channels 237 may be used to provide a cooling
fluid circuit comprising a cooling bond layer. For example, the
plurality of micro-channels 237 may have a graded thickness (Y
direction) as a function of the thickness of the cooling bond layer
230.
[0048] Referring now to FIGS. 11A-11B, a non-limiting example of a
cooling bond layer with micro-channels in the form of tubing
extending through the cooling bond layer is schematically depicted
(herein referred to as "tube micro-channels"). Particularly, FIG.
11A and 11B schematically depict a side cross sectional view and a
top view, respectively, of the semiconductor device 120 thermally
bonded to the substrate 110 with a cooling bond layer 330. The
cooling bond layer 330 includes a metal matrix 333 with a plurality
of tubes 334 disposed within and extending through the metal matrix
333 as depicted in FIGS. 11A-11B. That is, the plurality of tubes
334 are disposed within and extend beyond (+/- X directions) the
cooling bond layer 330. It should be understood that the plurality
of tubes 334 are hollow with inner diameters that form a plurality
of tube micro-channels within the metal matrix 333. As depicted in
FIGS. 11A-11B, a cooling fluid `CF` may flow through the plurality
of tubes 334 as part of a cooling fluid circuit (not labeled)
comprising the cooling bond layer 330 for the power electronics
assembly 100. It should be understood that electrical current may
flow between a lower surface (not labeled) and an upper surface
(not labeled) of the cooling bond layer 330 as described above with
respect to the cooling bond layer 130 and FIG. 4.
[0049] In embodiments, the cooling bond layer 330 may be disposed
between and in direct contact with the substrate 110 and the
semiconductor device 120. In other embodiments, the cooling bond
layer 330 may be disposed between but not be in direct contact with
the substrate 110 and the semiconductor device 120. That is, one or
more additional layers may be disposed between the cooling bond
layer 330 and the substrate 110 and/or one or more additional
layers may be disposed between the cooling bond layer 330 and the
semiconductor device 120. One non-limiting example includes a Ni
layer on the substrate 110 and/or the semiconductor device 120 to
assist in bonding with the cooling bond layer 330.
[0050] Referring now to FIGS. 12A-12B, a process for forming the
cooling bond layer 130 and the power electronics assembly 100 is
schematically depicted. Particularly, a side view of a process for
forming the cooling bond layer 130 and the power electronics
assembly 100 is schematically depicted in FIG. 12A and an end view
of the process depicted in FIG. 12A is shown in FIG. 12B. At step
10 a template 139 for the plurality of tubeless micro-channels 137
and a soldering material is positioned between the substrate 110
and the semiconductor device 120. The template 139 may comprise a
plurality of cylindrical shaped members 137', e.g., cylindrical
shaped rods or tubes. In the alternative, or in addition to, the
template 139 may comprise a plurality of non-cylindrical shaped
members (not shown). In embodiments, the soldering material may be
electrolytically or electrolessly deposited layers of soldering
material on the substrate 110 and the semiconductor device 120. For
example, the upper surface (+Y direction) of the substrate 110 and
the lower surface (-Y direction) of the semiconductor device 120
may be electroplated with a thin layer of Ni (not shown), after
which a layer of soldering material (not shown) is electrolytically
or electrolessly deposited onto the Ni layers to provide a pair of
Sn soldering layers. In other embodiments, a layer of soldering
material paste (not shown) is disposed on the upper surface of the
substrate 110, the plurality of cylindrical shaped members 137' are
positioned onto the layer of soldering paste, and the semiconductor
device 120 is positioned onto the plurality of cylindrical shaped
members 137'. In still other embodiments, a first foil of soldering
material (not shown) is positioned on the upper surface of the
substrate 110, the plurality of cylindrical shaped members 137' are
positioned onto the first foil of soldering paste, a second foil of
soldering material is positioned on the plurality of cylindrical
shaped members 137', and the semiconductor device 120 is positioned
on the second foil of soldering material.
[0051] At step 12 the cooling bond layer 130 is formed and the
substrate 110 is thermally bonded to the semiconductor device 120.
One non-limiting process for forming the cooling bond layer 130 and
thermally bonding the substrate 110 to the semiconductor device 120
is the reflow soldering process. Particularly, the substrate 110,
plurality of cylindrical shaped members 137', soldering material,
and semiconductor device 120 may be placed in an oven or furnace
and heated to a soldering temperature above the melting point of
the soldering material. At the soldering temperature the soldering
material melts, flows around the plurality of cylindrical shaped
members 137' and forms the metal matrix 136 around the plurality of
cylindrical shaped members 137' when the liquid soldering material
solidifies. That is, during the reflow soldering process at step 12
the soldering material melts and flows between the plurality of
cylindrical shaped members 137' and forms the metal matrix 136. In
embodiments, the soldering material is a Sn soldering material such
as a Sn87/10In/3Ag alloy with a solidus temperature of about
204.degree. C., a Sn92/B5i/Cu3 alloy with a solidus temperature of
about 211.degree. C., a Sn95.5/Ag4/Cu0.5 alloy with a solidus
temperature of about 217.degree. C., and the like.
[0052] In embodiments, for example when the plurality of
cylindrical shaped members 137' are cylindrical shaped rods or
tubes, the cylindrical shaped members 137' may be removed from the
metal matrix 136 to form the cooling bond layer 130 with the
plurality of tubeless micro-channels 137. For example, the
cylindrical shaped members 137' may be formed from material that
does not wet or is not wet by the liquid soldering material during
the reflow soldering process. Accordingly, the plurality of
cylindrical shaped members 137' can be mechanically removed by
applying a force to one end of the cylindrical shaped members 137'
and pushing the cylindrical shaped members 137' out of the metal
matrix 136 as depicted at step 14. As used herein, the term "wet"
refers to a surface bonding to liquid soldering material via a
diffusion reaction between the surface and the liquid surface
material. Accordingly, a material that does not wet during the
reflow soldering process does form a surface bond with the liquid
soldering material during the reflow soldering process.
Non-limiting examples of materials that do not wet during the
reflow soldering process include graphite, stainless steel and the
like. In the alternative, or in addition to, the cylindrical shaped
members 137' may be removed by etching the cylindrical shaped
members 137' out of the metal matrix 136 (not shown) to form the
cooling bond layer 130 with the plurality of tubeless
micro-channels 137.
[0053] Referring now to FIGS. 13A-13B, a process for forming the
cooling bond layer 230 and the power electronics assembly 100 is
schematically depicted. Particularly, a side view of a process for
forming the cooling bond layer 230 and the power electronics
assembly 100 is schematically depicted in FIG. 13A and an end view
of the process depicted in FIG. 13A is shown in FIG. 13B. At step
20 a template 239 for the plurality of micro-channels 237 and
soldering material are positioned between the substrate 110 and the
semiconductor device 120. The template 239 may comprise a plurality
of wire mesh layers 237'. Similar to the cooling bond layer 130
discussed above with reference to FIGS. 12A-12B, the cooling bond
layer 230 may be formed during a reflow soldering process in which
liquid soldering material flows around the plurality of wire mesh
layers 237'. The plurality of wire mesh layers 237' are removed
from the metal matrix 236 to form the cooling bond layer 230 with
the plurality of micro-channels 237 at step 24. For example, the
template 239 may be removed by dissolving the plurality of wire
mesh layers 237'.
[0054] Referring now to FIGS. 14A-14B, a process for forming the
cooling bond layer 330 and the power electronics assembly 100 is
schematically depicted. Particularly, a side view of a process for
forming the cooling bond layer 330 and the power electronics
assembly 100 is schematically depicted in FIG. 14A and an end view
of the process depicted in FIG. 14A is shown in FIG. 14B. At step
30 a first solder material foil 331, a plurality of tubes 334 and a
second solder material foil 332 are positioned between the
substrate 110 and the semiconductor device 120. The first solder
material foil 331 is position on the substrate 110 as are
stand-offs 340 for supporting and positioning the plurality of
tubes 334 above (+Y direction) the substrate 110 as depicted in
FIG. 14A. At step 32 the plurality of tubes 334 are positioned in
contact with the first solder material foil 331, the second solder
material foil 332 is positioned in contact with the plurality of
tubes 334, and the semiconductor device 120 is positioned in
contact with the second solder material foil 332 to form a
soldering assembly (not labeled). The soldering assembly is heated
to an elevated temperature (e.g., a soldering temperature) where
the first solder material foil 331 and the second solder material
foil 332 melt and from a metal matrix 333 (e.g., a single solder
layer) with the plurality of tubes 334 disposed there within at
step 34. As shown at step 34, the plurality of tubes 334 are not
removed from the metal matrix 333 and thereby provided the
plurality of micro-channels configured for a cooling fluid to flow
through and remove heat from the cooling bond layer 330.
[0055] In embodiments, the first solder material foil 331 and the
second solder material foil 332 may each comprise a tin (Sn) alloy
layer with a thickness (Y direction) between about 50 .mu.m and
about 500 .mu.m, the plurality of tubes may include Sn plated oxide
coated stainless steel tubes, and the soldering temperature may be
between about 200.degree. C. and about 250.degree. C. One
non-limiting example includes a first solder material foil 331
formed from a Sn alloy and having a thickness of about 100 .mu.m, a
second solder material foil 332 formed from a Sn alloy and having a
thickness of about 200 .mu.m, and a plurality of stainless steel
tubes 334 with an inner diameter of about 80 .mu.m. The plurality
of stainless steel tubes 334 may be plated with Ni and/or Sn. It
should be understood that solder material layers formed form
different alloys and having different thicknesses, and tubes with
different diameters, may be utilized.
[0056] As stated above, the power electronics assemblies described
herein may be incorporated into an inverter circuit or system that
converts direct current electrical power into alternating current
electrical power and vice versa depending on the particular
application. For example, in a hybrid electric vehicle application
as illustrated in FIG. 15, several power electronics assemblies
100a-100f may be electrically coupled together to form a drive
circuit that converts direct current electrical power provided by a
bank of batteries 164 into alternating electrical power that is
used to drive an electric motor 166 coupled to the wheels 168 of a
vehicle 160 to propel the vehicle 160 using electric power. The
power electronics assemblies 100a-100f used in the drive circuit
may also be used to convert alternating current electrical power
resulting from use of the electric motor 166 and regenerative
braking back into direct current electrical power for storage in
the bank of batteries 164.
[0057] Power semiconductor devices utilized in such vehicular
applications may generate a significant amount of heat during
operation thereby requiring cooling of the semiconductor devices.
The cooling bond layers described and illustrated herein may be
used as part of a cooling fluid circuit to cool the semiconductor
devices while also providing a compact package design.
[0058] It should now be understood that the cooling bond layers in
the power electronics assemblies and vehicles described herein may
be utilized for cooling semiconductor devices without the need for
complex cooling circuits, thereby providing for a more compact
package design. Particularly, the cooling bond layers described
herein may be bonded to semiconductor devices that generate heat
during operation and the plurality of micro-channels within the
cooling bond layers are configured for fluid to flow through the
cooling bond layers thereby removing heat from the semiconductor
devices.
[0059] It is noted that the terms "about" and "generally" may be
utilized herein to represent the inherent degree of uncertainty
that may be attributed to any quantitative comparison, value,
measurement, or other representation. This term is also utilized
herein to represent the degree by which a quantitative
representation may vary from a stated reference without resulting
in a change in the basic function of the subject matter at
issue.
[0060] While particular embodiments have been illustrated and
described herein, it should be understood that various other
changes and modifications may be made without departing from the
spirit and scope of the claimed subject matter. Moreover, although
various aspects of the claimed subject matter have been described
herein, such aspects need not be utilized in combination. It is
therefore intended that the appended claims cover all such changes
and modifications that are within the scope of the claimed subject
matter.
* * * * *