U.S. patent application number 15/428471 was filed with the patent office on 2018-08-09 for power electronics module.
The applicant listed for this patent is ABB Technology Oy. Invention is credited to Kjell lngman, Jorma Manninen, Mika Silvennoinen.
Application Number | 20180226318 15/428471 |
Document ID | / |
Family ID | 63014126 |
Filed Date | 2018-08-09 |
United States Patent
Application |
20180226318 |
Kind Code |
A1 |
Manninen; Jorma ; et
al. |
August 9, 2018 |
POWER ELECTRONICS MODULE
Abstract
A power electronics module and a method of manufacturing a power
electronics module and a base plate. The power electronics module
comprising at least one power electronics component, wherein the
power electronics module comprises a base plate for transferring
heat generated by the at least one power electronics component to a
cooling device, the base plate comprising a layered structure
having a first copper layer, a second copper layer and a carbon
based layer between the first and second copper layers.
Inventors: |
Manninen; Jorma; (Vantaa,
FI) ; Silvennoinen; Mika; (Espoo, FI) ;
lngman; Kjell; (Soderkulla, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ABB Technology Oy |
Helsinki |
|
FI |
|
|
Family ID: |
63014126 |
Appl. No.: |
15/428471 |
Filed: |
February 9, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/373 20130101;
H01L 2224/32225 20130101; H01L 23/3735 20130101; H01L 25/072
20130101; H01L 23/4924 20130101 |
International
Class: |
H01L 23/367 20060101
H01L023/367; H01L 23/492 20060101 H01L023/492; H01L 21/48 20060101
H01L021/48 |
Claims
1. A power electronics module comprising at least one power
electronics component, wherein the power electronics module
comprises a base plate for transferring heat generated by the at
least one power electronics component to a cooling device, the base
plate comprising a layered structure having a first copper layer, a
second copper layer and a carbon based layer between the first and
second copper layers, wherein the base plate comprises at least one
thermal via formed of particles contained in the carbon based
material layer.
2. A power electronics module according to claim 1, wherein the
first copper layer is adapted to receive heat from the at least one
power electronics component and a surface of the second copper
layer is adapted to receive a surface of a cooling device in
thermal contact for transferring heat from the power electronics
module to the cooling device.
3. A power electronics module according to claim 2, wherein a
surface of the first copper layer is soldered to an inner structure
of the power electronics module.
4. A power electronics module according to claim 3, wherein the
inner structure of the power electronics module comprises a direct
copper bonding structure to which the surface of the first copper
layer is soldered.
5. A power electronics module according to claim 1, wherein the
base plate is formed by copper welding first and second copper
layers together with the carbon based material between the
layers.
6-8. (canceled)
9. A power electronics module according to claim 1, wherein the at
least one thermal via is cylindrical.
10. (canceled)
11. A power electronics module according to claim 1, wherein the at
least one thermal via is situated within a footprint area of a
semiconductor chip of the at least one power electronics
component.
12. A power electronics module according to claim 1, wherein the at
least one thermal via is situated below the semiconductor chip.
13. A method of manufacturing a base plate for a power
semiconductor module, the method comprising providing a first
copper layer, a second copper layer and a carbon based material
layer, forming a layered structure having the first copper layer
and the second copper layer and the carbon based material layer
between the first and second copper layers, and forming at least
one thermal via for enhancing the heat transfer through the layered
structure, the thermal via extending through the first copper
layer, the second copper layer and the carbon based material layer,
and the at least one thermal via being formed of particles
contained in the carbon based material layer.
14-15. (canceled)
16. A method of manufacturing a power electronics module, the
method comprising providing a direct copper bonding structure with
at least one semiconductor chip, providing a first copper layer, a
second copper layer and a carbon based material layer, forming a
layered structure having the first copper layer and the second
copper layer and the carbon based material layer between the first
and second copper layers, forming at least one thermal via for
enhancing the heat transfer through the layered structure, the
thermal via extending through the first copper layer, the second
copper layer and the carbon based material layer, and the at least
one thermal via being formed of particles contained in the carbon
based material layer, and soldering the direct copper bonding
structure to a surface of the formed layered structure.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a power electronics
component having a base plate and to a method of manufacturing a
power electronics component.
BACKGROUND OF THE INVENTION
[0002] Power electronics components, such as single power
electronics components or power electronic modules, are commonly
used in high powered devices for switching high currents and
operating on high voltages. With single power electronics
components reference is made to high power thyristors and diodes,
for example. Power electronics modules contain multiple of switch
components which are situated in a same component housing and
typically internally connected to each other to provide a certain
circuit structure.
[0003] Power electronics modules are used, for example, for
producing certain power conversion circuits, such as inverters and
converters. An example of a power electronics module contains two
IGBTs (Insulated Gate Bi-polar Transistors) which are connected in
series inside the module. Other examples may include bridge
topologies or parts of bridge topologies which are readily
electrically connected inside the module.
[0004] Power electronics modules or single power electronics
components may also comprise a base plate which is typically made
of copper. The purpose of the base plate is to conduct the heat
generated by the semiconductors to a cooling device, such as
heatsink. The surface of the base plate is typically a
substantially planar surface to which a heatsink can be attached.
The heatsink is further dimensioned to take into account the amount
of heat generated by the semiconductor components in the
module.
[0005] FIG. 1 shows an example of a cross-section of a power
electronics module 1 attached to a heatsink 2. The power
electronics module of the example comprises two semiconductor chips
11, 12 which are soldered to a direct copper bonding (DCB)
structure. The DCB structure of the example has two copper plates 3
and a ceramic layer 4 between the copper plates 3. The DCB
structure is soldered with a solder layer 5 on the top of a copper
base plate 7 of the module. The module further comprises a housing
6 which is shown with a dash-dot line surrounding the DCB structure
and the chips.
[0006] The module of the example of FIG. 1 is attached to a
heatsink such that a thermal interface material 8 is positioned
between the base plate of the module and the base plate of the
heatsink. The purpose of the thermal interface material is to
transfer the heat from the module's base plate to the heatsink as
effectively as possible. It should be noted that FIG. 1 is provided
only to show an example of structure of power electronic module
attached to a heatsink. It is clear that other kinds of structures
exist.
[0007] Power electronics module's internal electronics packing
density increases gradually with advanced construction materials
and manufacturing methods. This is leading to more challenging
module external cooling solutions as devices are able to create
very high, over 35 W/cm.sup.2, hot spots to the heatsink
surface.
[0008] In view of cooling the situation is most demanding when the
module is operated at its maximum current and voltage level i.e. at
maximum power. In this condition the conventional aluminium heat
sinks' baseplate spreading thermal resistance is too high for the
module base plate high heat spots. That is, a conventional
aluminium heatsink is not able to spread the heat transferred from
the baseplate of the module fast enough. This results in both
higher heatsink-to-baseplate temperatures and chip-to-junction
temperatures accordingly. Although novel components may allow
higher junction temperatures than before due to novel chip
material, the component may not be fully utilized unless the power
electronics module's external cooling in not at appropriate
level.
[0009] Common power electronics module external cooling solutions
include for example aluminium heat sinks. These conventional
solutions are quite sufficient for base plate heat loss densities
of typical power electronics modules.
[0010] More demanding applications with higher base plate heat loss
densities, e.g. over 35 W/cm2, require clearly more effective heat
transfer from the base plate. Typically heat transfer is increased
for example by increasing cooling air flow rate with larger cooling
fans, modifying the aluminium heat sink in different ways like.
Modification may include adding a copper heat spreading plate in to
the base plate or replacing the heatsink aluminium cooling fins
with copper fins. More effective cooling arrangements can be
obtained by replacing the aluminium heat sink with heat pipe heat
sinks or thermosiphon cooling devices.
[0011] Common challenge for these more efficient heat sink and
cooling designs is that their cost is significantly higher than
conventional aluminium heat sink's. The cost increase derives from
several issues like more laborious manufacturing, more complex
manufacturing, and higher price materials. It would thus be
beneficial to manage the centralized heat loss density within the
power electronics module and this way enable use of relatively low
cost heat sink solutions.
BRIEF DISCLOSURE OF THE INVENTION
[0012] An object of the present invention is to provide a power
electronics module and a method of producing a base plate for a
power electronics module and of producing a power electronics
module so as to solve the above problems. The objects of the
invention are achieved by a power electronics module and a method
which are characterized by what is stated in the independent
claims. The preferred embodiments of the invention are disclosed in
the dependent claims.
[0013] The invention is based on the idea of producing a novel base
plate of a power electronics module. The base plate of a power
electronics module comprises a layered structure having copper
layers and a carbon based layer between the copper layers. The
carbon based layer is preferably graphite layer or graphene layer.
The base plate is preferably formed such that copper surrounds the
carbon based material layer in all sides of the base plate, and
thus the carbon based material forms a core of the base plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the following the invention will be described in greater
detail by means of preferred embodiments with reference to the
accompanying drawings, in which
[0015] FIG. 1 shows a prior art power electronics module attached
to a heatsink;
[0016] FIG. 2 shows cross sections of an embodiment of the present
invention; and
[0017] FIGS. 3 and 4 show flowcharts of the methods.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 2 shows cross sectional views of an embodiment of a
power electronics module of the present disclosure. The upper
drawing of FIG. 2 shows a cross sectional view as seen from the
side of the module and the lower drawing of FIG. 2 shows a cross
sectional view revealing the inner structure of the base plate of
the power electronics module.
[0019] According to the present invention the power electronics
module comprises at least one power electronic component. In the
example of FIG. 2 two power electronics components 11, 12 are
shown. Further, the power electronics module comprises a base plate
21 for transferring heat generated by the at least one power
electronics component to a cooling device. According to the present
disclosure, the base plate comprises a layered structure having a
first copper layer, a second copper layer and a carbon based layer
between the first and second copper layers.
[0020] In the example of FIG. 2, the direct copper bonding
structure 3, 4 and the chips 11, 12 are similar as in the example
of FIG. 1. In FIG. 2, the base plate 21 which is fastened to the
DCB structure 3, 4 of the power electronics module is formed of a
layered structure having a first copper layer 22, a carbon based
material layer 23 and a second copper layer 24. The carbon based
material layer 23 is situated between the two copper layers 22, 24.
It shown in FIG. 2 that the copper layers have larger surface areas
than the carbon based layer and that the copper layers are fastened
to each other in the ends of the layers. When the copper layers are
fastened to each other a carbon based material core is formed
within a copper base plate.
[0021] When the semiconductor components of the module are used,
the losses in the components or chips 11, 12 generate heat. The
heat is transferred through the DCB structure 3, 4 to the base
plate. The base plate of the invention having a carbon based layer
spreads the heat effectively inside the base plate and thus
prevents formation of hot-spots in the base plate in the footprint
area of the semiconductor chips. With the footprint area of the
chips it is referred to the surface area that is directly below
chips.
[0022] The carbon based material layer is preferably formed from
natural graphite, pyrolytic graphite or graphene. This carbon
material layer has anisotropic thermal conductivity of
approximately 1500 W/mK in-plane and 60 W/mK through-thickness.
Thus the material is spreads the heat in the direction of length L
and width W effectively. When the heat is spread inside the base
plate, the heat is also transferred to the second copper layer 24
from the carbon based layer 23 in the whole surface area of the
carbon based layer 23.
[0023] A surface of the second copper layer 24 is adapted to
receive a cooling device in thermally conductive manner such that
the heat from the semiconductor components or chips is led through
the base plate to the cooling device such as a heat sink. As the
heat is spread in a uniform manner in the base plate, the cooling
device does not have to be as effective as in the case with the
known base plates.
[0024] Preferably the base plate comprises at least one thermal via
which is formed of a copper pillar arranged to be in thermal
contact with the first copper layer, second copper layer and the
carbon based material layer. The thermal via or multiple of thermal
vias are arranged preferably within a footprint area a
semiconductor chip of the at least one power electronics
component.
[0025] FIG. 2 shows the thermal vias 25 in the cross sectional
views. The cross sectional view from the side of the component
(upper drawing) is taken along a line which crosses the thermal
vias and therefore the first and second copper layers are shown as
being connected. The lower drawing of FIG. 2 is a cross sectional
view as seen from below the module and taken along a plane which
cuts the carbon based material layer. The lower drawing reveals the
structuring of the thermal vias and their position with respect to
the footprint of the semiconductor chips. The footprints 111, 112
of the two semiconductor chips 11, 12 are shown as dashed lines in
FIG. 2. The thermal vias are situated within the footprints and
thus below the semiconductor chips.
[0026] The thermal vias are formed preferably from copper pillars
which are shown in the Figures to have a circular cross section.
The copper pillars are thus cylindrical pieces which are attached
to the base plate. The thermal vias provide a thermally highly
conductive path below the semiconductors. The copper pillars
enhance the thermal conduction into the carbon core of the base
plate. Further the copper pillars enhance the thermal conduction
through the carbon core or carbon based material layer,
[0027] In the invention the base plate is a layered structure which
has approximately the same thickness as a conventional base plate
which is a solid copper block. For example, if ea known a solid
copper base plate has a thickness of 4 mm, then the base plate of
the module of the invention can be realized in form of two 1.5 mm
thick copper plates with a 1.0 mm thick carbon based material
layer. The copper pillars used for providing thermal conduction
paths can be realized from cylindrical pieces having a diameter of
3 mm, for example. According to an embodiment of the invention, the
thickness of the carbon based material layer is approximately one
third of the sum thicknesses of the copper layers.
[0028] The balance between heat conduction into the carbon core and
through the carbon core can be affected with the dimensioning of
the thermal vias or copper pillars. Both mentioned features are
beneficial for the base plate's effective function and their
relative balance is case specific. The balance depends on baseplate
total thickness, carbon core's thickness t and relative position h
within the copper baseplate, thermal vias' diameter and their count
and their location, heat sources' (chips') footprint size and their
heat flux profile and chip layout, for example. With the relative
position h of the carbon core or carbon layer with the copper base
plate it is referred to the distance of carbon based layer from the
upper surface of the first copper layer. FIG. 2 shows the relative
position h as well as the thickness of the carbon based material
layer or core.
[0029] The one or more copper pillars used as thermal vias act also
as providing physical strength to the base plate. The copper
pillars are placed in a hole which is drilled to the layered
structure. The holes and the pillars can be dimensioned in such a
manner that the pillars are fitted tightly to the corresponding
holes and thereby provide support to the structure. Further, the
hole or holes that are drilled must not penetrate through both of
the copper layers. For example, when a hole is drilled the drill
penetrates through the first layer and the carbon based layer.
However, the drilling may be ended such that it does not penetrate
through the second copper layer.
[0030] For providing a suitable surface for thermal connection the
copper pillars have a suitable length when attached to the holes.
The surfaces of the base plate can also be perforated after the
pillars have been inserted such that a required thermal connection
can be established between the structure of other components of the
power semiconductor module and between the cooling device that is
to be attached to the power semiconductor module.
[0031] The thermal conductivity of the carbon based material layer
is preferably in the range of 1000 W/mK to 1600 W/mK in-plane and
30 W/mK to 100 W/mK through-thickness. Thus the heat is transferred
in the planar direction of the carbon based material layer and
similarly in the planar direction of the base plate considerably
better than in the direction of height of the base plate. Planar
direction comprises the directions shown by arrows W and L and the
direction of height is shown by arrow H in FIG. 2.
[0032] According to an embodiment, the at least one thermal via can
also be produced by small particles which are in the carbon based
material layer. These particles are preferably nano or micro
particles and enhance the thermal conductivity locally in
through-thickness direction H. As with the copper pillars, the
small particles increase the thermal conduction through the layered
structure and to the carbon based material layer.
[0033] In the method of manufacturing a base plate for a power
semiconductor module a first copper layer, a second copper layer
and a carbon based material layer are provided 32 as depicted in
FIG. 3. From the separate layers it is formed 33 a layered
structure having first copper layer and the second copper layer and
a carbon based material layer between the copper layers.
[0034] In an embodiment of the method, at least one thermal via is
formed to the base plate for enhancing the heat transfer through
the layered structure. Preferably the thermal via is formed by
drilling a hole to the layered structure and inserting a copper
pillar to the drilled hole.
[0035] In the method of manufacturing a power electronics module a
direct copper bonding structure with at least one semiconductor
chip is provided 42. Further, a base plate is provided with the
above procedure 43, 44. Further, the provided direct copper bonding
structure is soldered 45 to a surface of the formed layered
structure, that is to a surface of base plate.
[0036] It will be obvious to a person skilled in the art that, as
the technology advances, the inventive concept can be implemented
in various ways. The invention and its embodiments are not limited
to the examples described above but may vary within the scope of
the claims.
* * * * *