CN116171489A

CN116171489A - Cooling power module package

Info

Publication number: CN116171489A
Application number: CN202180033804.XA
Authority: CN
Inventors: A·斯特拉斯; T·科尔达斯; A·博尔贾; 尤尔根·霍格尔; 麦成乐
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-09-24
Filing date: 2021-09-24
Publication date: 2023-05-26
Also published as: WO2023046289A1

Abstract

A cooling power module package (100) comprising: a power module (110) having an upper metal layer forming an upper heat dissipation surface (111 a); a heat sink (120) comprising a heat absorbing surface (121 b); a metal substrate (130) encapsulated between the heat absorbing surface and the upper heat dissipating surface. The metal substrate includes a first metal line (132 a) protruding from a first substrate surface (131 a) of the metal substrate toward the heat absorbing surface. The first metal wire is disposed within a first cavity formed within a surface structure of a heat absorbing surface of the heat sink. The metal substrate includes a second metal line (132 b) protruding from a second substrate surface (131 b) of the metal substrate toward an upper heat dissipation surface of the power module. The second metal lines are disposed within a second cavity formed within a surface structure of an upper heat dissipation surface of the power module.

Description

Cooling power module package

Technical Field

The present disclosure relates to the field of thermal coupling and cooling of semiconductor power modules, for example, power modules that may be used in automotive and industrial applications, such as power inverter systems and power converters. In particular, the present disclosure relates to cooling power module packages and methods for producing such power module packages. More particularly, the present disclosure relates to a high-conductivity thermally coupled connection for active high-voltage components.

Background

The efficiency of thermal management is critical to the power inverter system for determining its lifetime and switching performance. The thermal resistance between the heat source (die) and the heat sink should be as low as possible to ensure a rapid cooling process. This requires the use of ideal thermal attachment techniques between the joining components (e.g., IGBTs and power modules) and the heat sink, which may be made of, for example, aluminum or aluminum alloys.

Currently, different thermal bonding techniques are available. One approach is a thermally conductive grease material, which is a paste-like substrate, typically with aluminum particles inside to increase thermal conductivity. The disadvantage of this solution is the low thermal conductivity due to the high thermal resistance of the slurry carrier material substrate. Another disadvantage is that the slurry can exhibit a typical "pump out" effect under thermally stressed conditions. This may lead to contamination around the joint area and electrical failure.

Another thermal interface material approach is to use a material having a ribbon-like appearance with certain fillers (e.g., graphite particles) placed between the joined components. Here, it is typically a variant of the phase change type, which becomes soft and even liquid under thermal shock. The "pump out" effect also occurs here and may lead to electrical faults, such as short circuits.

Disclosure of Invention

The present disclosure provides a solution for an efficient cooling concept for power modules without the above-mentioned drawbacks. In particular, a cooling power module package is provided that can guarantee better thermal conductivity at higher switching currents.

The foregoing and other objects are achieved by the features of the embodiments. Further implementations are apparent from other embodiments, the description and the drawings.

The basic idea of the present disclosure is to use a specially shaped metal (e.g. copper) foil for the thermal attachment of a power module (e.g. an IGBT power module) to a metal-based heat sink. This novel metal foil (or metal substrate referred to hereinafter) includes metal nano-filaments (hereinafter metal wires) on both sides of the foil, the metal joining means providing a metal-to-metal attachment to achieve a very low thermal resistance therebetween. In such a metal foil, e.g. copper foil, the nanowires or nanowires on both sides can contact the two joining members without low thermal resistance to dissipate thermal energy from the power module to the heat sink as quickly and efficiently as possible. That is, the present disclosure introduces a novel thermal cooling concept based on thermally attaching a power module with a metal-based heat sink using a special metal (e.g., copper) foil. For better adhesive bonding, an epoxy glue may be additionally applied on each side of the metal foil.

The following advantages can be achieved using this novel cooling concept: a) The metal foil or the nano-filament copper foil can compensate for the surface roughness of each surface of the joint member by using ductile filaments (wires) on both surface sides, respectively. This enables metal-to-metal attachment between bonding materials with low thermal resistance. b) The attachment to the nano-filament metal foil may be performed locally stable under ambient conditions at a certain pressure and temperature after the bonding process. c) The nano-filament metal foil is an additional sheet material that can be used for joining two metal parts without certain machining and treatment of the joining surface. Dirt, oil and grease contamination can be avoided by cleaning the joint components prior to joining. d) The thermal attachment may include mechanical attachment of two engagement members. The bonding force is primarily dependent on the pressure and temperature applied during bonding. For example, temperatures in the range of 100 to 150 degrees celsius allow for faster curing of the epoxy glue. For example, a pressure in the range of 20 to 50MPa may be applied. Depending on the maximum pressure that each engagement member can withstand. For example, the curing time may be set in the range of 8 to 15 minutes.

According to a first aspect, the present disclosure relates to a cooling power module package comprising: a power module for electrical power conversion, the power module comprising a first module side and a second module side opposite the first module side, wherein the first module side comprises an upper metal layer forming an upper heat dissipation surface of the power module; a heat sink including a heat absorbing surface opposite an upper heat dissipating surface of the power module; a metal substrate encapsulated between a heat absorbing surface of the heat spreader and an upper heat dissipating surface of the power module, wherein the metal substrate comprises a first substrate surface and a second substrate surface opposite the first substrate surface, wherein the metal substrate comprises a first metal wire protruding from the first substrate surface towards the heat absorbing surface of the heat spreader, wherein the first metal wire is arranged within a first cavity formed within a surface structure of the heat absorbing surface of the heat spreader, wherein the metal substrate comprises a second metal wire protruding from the second substrate surface towards the upper heat dissipating surface of the power module, wherein the second metal wire is arranged within a second cavity formed within a surface structure of the upper heat dissipating surface of the power module.

Such a cooling power module package provides an advantage in that the metal substrate having the metal wires on both sides can compensate for the surface roughness of both surface sides by the metal wires of both surface sides (i.e., the heat absorbing surface of the heat spreader and the upper heat dissipating surface of the power module). This enables metal-to-metal attachment between bonding materials with low thermal resistance.

In an exemplary implementation of the cooling power module package, a surface structure of a heat absorbing surface of the heat spreader is rugged, thereby forming a first cavity; and the surface structure of the upper heat dissipation surface of the power module is rugged, so that a second cavity is formed.

This provides the advantage that the metal substrate can be efficiently attached between two surface structures, thereby closing the air gaps or air cavities created by the rugged surface structures and providing high thermal connectivity between the surfaces.

In an exemplary implementation of the cooling power module package, the metal substrate comprises a metal foil, wherein the first metal line and the second metal line protrude from both sides of the metal foil.

This provides the advantage that the metal wire can be attached to the metal foil efficiently, providing a stable structure.

In an exemplary implementation of the cooling power module package, the lengths of the first and second metal lines are in a range of about 5 microns and 50 microns, the diameters of the first and second metal lines are in a range of about 0.1 microns and 2 microns, and the thickness of the metal foil is in a range of about 5 microns and 400 microns.

For example, the length of the first metal line and/or the second metal line may be 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns, or any value in between.

For example, the diameter of the first metal line and/or the second metal line may be 0.1 micron, 0.2 micron, 0.3 micron, 0.4 micron, 0.5 micron, 0.6 micron, 0.7 micron, 0.8 micron, 0.9 micron, 1.0 micron, 1.1 micron, 1.2 micron, 1.3 micron, 1.4 micron, 1.5 micron, 1.6 micron, 1.7 micron, 1.8 micron, 1.9 micron, 2.0 micron, or any value in between.

For example, the foil thickness may be 5 microns, 10 microns, 20 microns, 30 microns, 40 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 150 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns, or any value in between.

This provides the advantage that such exemplary values of the length and diameter of the first and second metal wires and the thickness of the foil can be easily manufactured and provide excellent heat conducting properties.

In an exemplary implementation of the cooling power module package, the length of the first metal wire is different from the length of the second metal wire; and/or the diameter of the first wire is different from the diameter of the second wire.

This provides the advantage that different surface characteristics of the upper heat dissipation surface of the power module and the heat absorbing surface of the heat sink may require different lengths. Longer lines may be required for rougher surfaces, while shorter lines may be required for less rough surfaces.

In an exemplary implementation of the cooling power module package, the length of the first metal wire corresponds to the length of the second metal wire; and/or the diameter of the first metal wire corresponds to the diameter of the second metal wire.

This provides the advantage that the same surface properties of the upper heat-dissipating surface of the power module and the heat-absorbing surface of the heat sink may require the same length and the same diameter. For example, if two surfaces have the same surface roughness, for example, due to the same manufacturing process.

In an exemplary implementation of the cooling power module package, the first metal lines are irregularly arranged within the first cavity; and the second metal lines are irregularly arranged in the second cavity.

This provides the advantage that such an irregular arrangement of the metal lines results in a better filling of the air gaps or air cavities of the surface structure and thus in a better thermal conductivity of the power module package.

In an exemplary implementation of the cooling power module package, the first metal lines are randomly arranged within the first cavity; and the second metal lines are randomly arranged within the second cavity.

This provides the advantage that such a random arrangement of the metal lines results in a better filling of the air gaps or air cavities of the surface structure and thus in a better thermal conductivity of the power module package.

In an exemplary implementation of the cooling power module package, the first wire is bent one or more times within the first cavity; and wherein the second wire is bent one or more times within the second cavity.

This provides the advantage that such a curved arrangement of the metal lines results in a better filling of the air gaps or air cavities of the surface structures and thus in a better thermal conductivity of the power module package.

In an exemplary implementation of the cooling power module package, the cooling power module package includes an adhesive layer at least partially filling the first cavity between the first metal lines.

This provides the advantage that the adhesive layer can close air gaps or air pockets with low electrical conductivity of air with an adhesive having a higher thermal conductivity than air, which increases the overall thermal conductivity of the package.

In one implementation, the first cavity is (at least partially) filled with an adhesive layer. In an alternative implementation, no adhesive layer is required and the first cavities are filled with air between the first metal lines.

This provides the advantage of a flexible manufacturing of the power module package. Depending on the requirements of the power module package, an adhesive may or may not be used.

In an exemplary implementation of the cooling power module package, the adhesive layer covers only a portion of the first metal line that is not in contact with the heat absorbing surface of the heat spreader.

This provides the advantage that a metal-to-metal connection is provided between the metal wire and the heat sink and that the heat dissipation from the power module to the heat sink is not affected by the adhesive layer.

The adhesive layer may be applied in a liquid state and then may become a solid state. Or more generally: the adhesive layer may be applied at a first viscosity and become a second viscosity after a curing time, as described below with respect to the method embodiments.

In an exemplary implementation of a cooling power module package, the cooling power module package includes: one or more voids in the portion of the first cavity not filled with the adhesive layer or the first metal line.

This provides the advantage of a flexible manufacturing process, wherein low temperature and pressure can be applied in order not to damage the power module.

In an exemplary implementation of the cooling power module package, the first metal line and the second metal line are made of copper.

This provides the advantage of high thermal conductivity due to the excellent thermal conductivity of copper.

In an exemplary implementation of the cooling power module package, a thermal conductivity between the upper heat dissipation surface of the power module and the heat absorption surface of the heat spreader is above 300W/m x K.

This provides the advantage of improving the thermal conductivity and cooling characteristics of the overall package.

In an exemplary implementation of the cooling power module package, the thickness of the first and second metal lines is below 1 micron.

For example, the thickness of the metal lines may be 0.01 microns, 0.02 microns, 0.03 microns, 0.04 microns, 0.05 microns, 0.1 microns, 0.15 microns, 0.2 microns, 0.3 microns, 0.4 microns, 0.5 microns, 0.6 microns, 0.7 microns, 0.8 microns, 0.9 microns, 0.95 microns, 0.99 microns, or any value in between.

This provides the advantage that such exemplary values of the thickness of the metal wire can be easily manufactured and provide excellent heat conduction properties.

In an exemplary implementation of a cooling power module package, the cooling power module package includes: a second heat sink including a heat absorbing surface opposite the lower heat dissipating surface of the power module; and a second metal substrate enclosed between the heat absorbing surface of the second heat sink and the lower heat dissipating surface of the power module, wherein the second metal substrate includes a first substrate surface and a second substrate surface opposite the first substrate surface, wherein the second metal substrate includes a first metal wire protruding from the first substrate surface toward the lower heat dissipating surface of the power module, the first metal wire being disposed within a third cavity formed within a surface structure of the lower heat dissipating surface of the power module, wherein the second metal substrate includes a second metal wire protruding from the second substrate surface toward the heat absorbing surface of the second heat sink, wherein the second metal wire is disposed within a fourth cavity formed within a surface structure of the heat absorbing surface of the second heat sink.

Such a double-sided cooling power module package provides an additional advantage over a single-sided cooling power module package in that two metal substrates with metal lines on both sides can compensate for the surface roughness of all four surface sides (i.e., the two heat absorbing surfaces of the two heat sinks and the upper and lower heat dissipating surfaces of the power module) by the metal lines on both surface sides of the metal substrate. This enables a metal-to-metal attachment between the bonding materials with low thermal resistance for both cooling sides.

According to a second aspect, the present disclosure relates to a method for producing a cooling power module package, the method comprising: providing a power module for electrical power conversion, the power module comprising a first module side and a second module side opposite the first module side, wherein the first module side comprises an upper metal layer forming an upper heat dissipation surface of the power module; providing a heat sink comprising a heat absorbing surface opposite an upper heat dissipating surface of the power module; and encapsulating a metal substrate between the heat absorbing surface of the heat spreader and the upper heat dissipating surface of the power module, wherein the metal substrate comprises a first substrate surface and a second substrate surface opposite the first substrate surface, wherein the metal substrate comprises first metal lines protruding from the first substrate surface towards the heat absorbing surface of the heat spreader, wherein the first metal lines are arranged within a first cavity formed within a surface structure of the heat absorbing surface of the heat spreader, and wherein the metal substrate comprises second metal lines protruding from the second substrate surface towards the upper heat dissipating surface of the power module, wherein the second metal lines are arranged within a second cavity formed within a surface structure of the upper heat dissipating surface of the power module.

The advantages of this method are the same as those of the corresponding implementation of the semiconductor package and vice versa.

That is, the method provides an advantage in that the metal substrate having the metal wires on both sides can compensate for the surface roughness of both surface sides by the metal wires of both surface sides (i.e., the heat absorbing surface of the heat sink and the upper heat dissipating surface of the power module). This enables metal-to-metal attachment between bonding materials with low thermal resistance.

The encapsulation of the metal substrate between the heat absorbing surface of the heat spreader and the upper heat dissipating surface of the power module may be performed at a certain temperature and a certain pressure. The higher the temperature, the higher the pressure, and the better the metal connection (and thus the heat dissipation) between the heat sink and the heat dissipation surface of the power module.

However, excessive pressures and temperatures may damage the power module. It has been shown that for protecting the power module the pressure should be below 3MPa (corresponding to 1 ton). Note that when about 5 tons or more of pressure is applied, intermetallic phases may be reached. Thus, with this approach, there may be no intermetallic phase between the heat sink and the heat dissipation surface of the power module.

In an exemplary implementation of the method, the encapsulation of the metal substrate between the heat absorbing surface of the heat spreader and the upper heat dissipating surface of the power module is performed at a temperature in the range of about 100 to 150 degrees celsius and at a pressure in the range of about 20 to 50 Mpa.

This provides the advantage that by applying temperature and pressure a tight metal connection between the heat sink and the power module can be achieved, thereby ensuring a high thermal conductivity.

In an exemplary implementation of the method, encapsulating the metal substrate between the heat sink surface of the heat spreader and the upper heat dissipation surface of the power module includes applying an adhesive between the heat sink surface of the heat spreader and a first substrate face of the metal substrate; and applying an adhesive between the upper heat dissipation surface of the power module and the second substrate face of the metal substrate.

This provides the advantage that the adhesive can close the air gap or air pocket of low electrical conductivity of air with an adhesive that has a higher thermal conductivity than air, which increases the overall thermal conductivity of the package.

In an exemplary implementation of the method, the adhesive has a first viscosity when the adhesive is applied; and the adhesive has a second viscosity after a curing time after application of the adhesive, wherein the second viscosity is higher than the first viscosity.

This provides the advantage that the adhesive layer may have flexible properties depending on the requirements of the package.

The adhesive layer may be applied in a liquid state and then may become a solid state. Or as defined more generally above, the adhesive layer may be applied at a first viscosity, e.g., a liquid state, and after a curing time, become a second viscosity, e.g., a solid state or a liquid state of a smaller viscosity than before, that is higher than the first viscosity.

According to a third aspect, the present disclosure relates to a computer program product comprising computer executable code or computer executable instructions which, when executed, cause at least one computer to perform a method according to the second aspect described above.

Such a computer program product may be implemented, for example, on a manufacturing machine, such as a Computer Numerical Control (CNC) of a manufacturing machine or manufacturing robot.

Drawings

Other embodiments of the invention will be described with reference to the following drawings, in which:

FIG. 1 shows a schematic diagram illustrating a cross-section of an exemplary cooling power module package 100 according to the present disclosure;

fig. 2 shows a schematic diagram illustrating a cross-section of an exemplary metal substrate 130 with metal lines on both sides for cooling a power module package according to the present disclosure;

FIG. 3 shows a schematic diagram illustrating a cross-section of an exemplary cooling power module having roughened surfaces of two engaging members;

FIG. 4 illustrates a photomicrograph 400 of a cross-section of an exemplary cooled power module package 100 showing a thermal interface for heat transfer from the power module to a heat sink in accordance with the present disclosure; and

Fig. 5 shows a schematic diagram illustrating a method 500 for producing the cooling power module package 100 according to the present disclosure.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is to be understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

It should be understood that comments made in connection with the described methods may also apply to a corresponding device or system configured to perform the method and vice versa. For example, if a particular method step is described, the corresponding device may include means for performing the described method step, even if such means are not explicitly described or illustrated in the figures. Furthermore, it should be understood that features of the various exemplary aspects described herein may be combined with one another, unless specifically noted otherwise.

For example, the power module packages and systems described herein may be implemented in automotive, industrial, or consumer electronics applications, e.g., for driving loads, converting power, etc. However, the power module packages and systems described herein may also be implemented in wireless communication schemes, such as communication schemes according to 5G or WiFi, such as for internet of things and the like. The described power module packages and systems may include integrated circuits and/or power semiconductors, such as IGBTs and/or MOSFETs, and may be fabricated according to a variety of techniques. For example, the power module packages and systems may be used with power and/or logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, and the like.

In this disclosure, a power module having a semiconductor chip is described. For example, the power modules may include MOSFET transistors or IGBTs. The power module may be produced based on silicon carbide (SiC) semiconductor technology and/or based on silicon (Si) semiconductor technology.

Fig. 1 shows a schematic diagram illustrating a cross-section of an exemplary cooling power module package 100 according to the present disclosure. The cooling power module package 100 includes a power module 110, a heat sink 120, and a metal substrate 130. The power module 110 may be a semiconductor power module for electric power conversion.

The power module 110 includes a first module side 110a and a second module side 110b opposite the first module side 110 a. In fig. 1, the first module side 110a is aligned to the top side of the figure, i.e. shown in the vertical direction, while the second module side 110b is aligned to the bottom side of the figure, i.e. shown in the opposite direction to the vertical direction, as can be seen from fig. 1. The first module side 110a includes an upper metal layer that forms an upper heat dissipation surface 111a of the power module 110.

The heat sink 120 includes a heat absorbing surface 121b opposite to the upper heat dissipating surface 111a of the power module 110. In this context, opposite means that the heat absorbing surface 121b faces the upper heat dissipating surface 111a of the power module 110 (through the metal substrate 130).

The metal substrate 130 is enclosed between the heat absorbing surface 121b of the heat spreader 120 and the upper heat dissipating surface 111a of the power module 110. The metal substrate 130 includes a first substrate face 131a and a second substrate face 131b opposite the first substrate face 131 a. The metal substrate 130 includes a first metal line 132a protruding from the first substrate face 131a toward the heat absorbing surface 121b of the heat sink 120. The first metal wire 132a is disposed in a first cavity formed in the surface structure of the heat absorbing surface 121 b. A first cavity is formed in the heat absorbing surface 121b of the heat sink 120 due to the rough surface of the heat absorbing surface 121 b. The first cavity may be formed by a plurality of isolated cavities or micro-holes on the heat absorbing surface 121b, or alternatively by one or several cavities interconnected to each other.

The metal substrate 130 includes a second metal line 132b protruding from the second substrate face 131b toward the upper heat dissipation surface 111a of the power module 110. The second metal lines 132b are disposed in a second cavity formed in the surface structure of the upper heat dissipation surface 111a of the power module 110. A second cavity is formed in the upper heat dissipation surface 111a of the power module 110 due to the rough surface of the upper heat dissipation surface 111 a. The second cavity may be formed by a plurality of isolated cavities or micro-holes in the upper heat dissipation surface 111a, or alternatively by one or several cavities interconnected to each other.

The surface structure of the heat absorbing surface 121b of the heat sink 120 is rugged, thereby forming a first cavity. Similarly, the surface structure of the upper heat dissipation surface 111a of the power module 110 is rugged, thereby forming a second cavity.

The metal substrate 130 may include a metal foil. The first and

second metal lines

132a and 132b protrude from both sides of the metal foil.

For example, in an exemplary implementation of the cooling power module package 100, the lengths of the first and

second metal lines

132a and 132b may be in the range of about 5 microns and 50 microns.

For example, in an exemplary implementation of the cooling power module package 100, the diameters of the first and

second metal lines

132a and 132b may be in the range of about 0.1 microns and 2 microns.

For example, in an exemplary implementation of the cooling power module package 100, the thickness of the metal foil is in the range of about 5 microns and 400 microns.

Note that these values are for example only, and that the cooling power module package 100 may have any other length and/or diameter of

wire

132a, 132b. The same applies to the thickness of the metal foil.

The length of the first metal line 132a may be different from the length of the second metal line 132b.

The diameter of the first metal line 132a may be different from the diameter of the second metal line 132b.

Different surface characteristics of the upper heat dissipation surface 111a of the power module 110 and the heat absorption surface 121b of the heat sink 120 may require different lengths. Longer lines may be required for rougher surfaces, while shorter lines may be required for less rough surfaces.

In an example of the metal foil, the length of the first metal line 132a may correspond to the length of the second metal line 132 b.

In an example of the metal foil, the diameter of the first metal wire (132 a) may correspond to the diameter of the second metal wire 132 b.

The same surface characteristics of the upper heat dissipation surface 111a of the power module 110 and the heat absorption surface 121b of the heat sink 120 may require the same length and the same diameter. For example, if two surfaces have the same surface roughness, for example, due to the same manufacturing process.

In an exemplary implementation of the cooling power module package 100, the first metal lines 132a may be irregularly arranged within the first cavity.

In an exemplary implementation of the cooling power module package 100, the second metal lines 132b may be irregularly arranged within the second cavity.

In an exemplary implementation of the cooling power module package 100, the first metal lines 132a may be randomly arranged within the first cavity.

In an exemplary implementation of the cooling power module package 100, the second metal lines 132b may be randomly arranged within the second cavity.

In an exemplary implementation of the cooling power module package 100, the first wire 132a may be bent one or more times within the first cavity.

In an exemplary implementation of the cooling power module package 100, the second wire 132b may be bent one or more times within the second cavity.

The cooling power module package 100 may include an adhesive layer at least partially filling the first cavity between the first metal lines 132 a.

In one implementation, the first cavity may be (at least partially) filled with an adhesive layer. In an alternative implementation, an adhesive layer is not required, and the first cavities may be filled with air between the first metal lines.

In an exemplary implementation of cooling the power module package 100, the adhesive layer may cover only a portion of the first metal line 132a that is not in contact with the heat absorbing surface 121b of the heat sink 120.

The adhesive layer may be applied in a liquid state and then may become a solid state. Or more generally: the adhesive layer may be applied at a first viscosity and become a second viscosity after a curing time, as described below with respect to the production method.

In an exemplary implementation of the cooling power module package 100, the cooling power module package 100 may include one or more voids in the portion of the first cavity not filled with the adhesive layer or the first metal lines 132 a.

In an exemplary implementation of the cooling power module package 100, the first and

second metal lines

132a and 132b may be made of copper.

In an exemplary implementation of cooling the power module package 100, the thermal conductivity between the upper heat dissipation surface 111a of the power module 110 and the heat absorption surface 121b of the heat sink 120 may be, for example, above 300W/m x K.

For example, in an exemplary implementation of the cooling power module package 100, the thickness of the first and

second metal lines

132a and 132b may be below 1 micron.

The cooling power module package 100 as shown in fig. 1 may be a double-sided cooling power module package including: a second heat sink 140 and a second metal substrate 150.

The second heat sink 140 includes a heat absorbing surface 141a opposite to the lower heat dissipating surface 111b of the power module 110.

The second metal substrate 150 is enclosed between the heat absorbing surface 141a of the second heat sink 140 and the lower heat dissipating surface 111b of the power module 110.

The second metal substrate 150 may include a first substrate surface 151a and a second substrate surface 151b opposite to the first substrate surface 151 a.

The second metal substrate 150 may include a first metal line 152a protruding from the first substrate face 151a toward the lower heat dissipation surface 111b of the power module 110. The first metal lines 152a may be disposed in a third cavity formed in the surface structure of the lower heat dissipation surface 111b of the power module 110.

The second metal substrate 130 may include a second metal line 152b protruding from the second substrate surface 151b toward the heat absorbing surface 141a of the second heat sink 140. The second metal wire 152b may be disposed in a fourth cavity formed in the surface structure of the heat absorbing surface 141a of the second heat sink 140.

The same characteristics as those of the metal substrate 130 having the first and second metal lines described above are also applicable to the second metal substrate 150 having the first and

second metal lines

152a and 152b.

Such a cooling power module package 100 provides the following advantages. The metal substrate 130 having the first and

second metal lines

132a and 132b compensates for surface roughness of both surfaces of the power module 110 and the heat sink 120 by ductile lines or filaments of both surface sides. This enables metal-to-metal attachment between bonding materials with low thermal resistance.

The attachment with the first and

second metal lines

132a and 132b to the metal substrate 130 may be locally stably performed under ambient conditions at a certain pressure and temperature after the bonding process.

The metal substrate 130 with the first metal lines 132a and the second metal lines 132b is an additional sheet that can be used to join two metal parts without some treatment and machining of the joining surfaces.

The thermal attachment may include mechanical attachment of two engagement members. The bonding force is primarily dependent on the pressure and temperature applied during bonding. For example, temperatures in the range of 100 to 150 degrees celsius allow for faster curing of the applied epoxy glue. For example, a pressure in the range of 20 to 50MPa may be applied. Depending on the maximum pressure that each engagement member can withstand. For example, the curing time may be set in the range of 8 to 15 minutes.

Fig. 2 shows a schematic diagram illustrating a cross-section of an exemplary metal substrate 130 with

metal lines

132a, 132b on both sides for cooling a power module package according to the present disclosure.

The metal substrate 130 may correspond to the (upper side) metal substrate 130 described with respect to fig. 1 or to the (bottom side) metal substrate 150 described with respect to fig. 1.

The metal substrate 130 may include a metal foil. As can be seen in fig. 2, the first and

second metal lines

132a and 132b protrude from both sides of the metal foil.

As shown in fig. 2, the lengths of the first and

second metal lines

132a and 132b may be, for example, in the range of about 5 micrometers and 50 micrometers.

The diameters of the first and

second metal lines

132a and 132b may be, for example, in the range of about 0.1 micrometers and 2 micrometers.

As shown in fig. 2, the thickness of the metal foil may be, for example, in the range of about 5 microns and 400 microns. These values are given by way of example only. Any other length and/or diameter of

wire

132a, 132b may be used. The same applies to the thickness of the metal foil.

The length of the first metal line 132a may be different from the length of the second metal line 132b. Alternatively, the length of the first metal line 132a may be the same as the length of the second metal line 132b, as exemplarily shown in fig. 2.

The diameter of the first metal line 132a may be different from the diameter of the second metal line 132b. Alternatively, the diameters may be the same.

The

metal wires

132a, 132b may be irregularly arranged in the first/second cavities. As can be seen from fig. 2, the

metal wires

132a, 132b may be regularly arranged within the first/second cavities before the metal substrate 130 is attached between the heat sink and the power module. Through the attachment process, cavities in the surface structure of the heat sink and/or the power module are filled with

wires

132a, 132b, resulting in irregular shapes of these

wires

132a, 132 b.

In other words, the present disclosure describes a method of attaching a specially shaped copper foil with copper nanofilaments or wires on both sides to a metal joining component in a metal-to-metal attachment manner to achieve very low thermal resistance therebetween. The copper foil core may be based on copper foil material from a copper coil. During the electroplating process, copper nanowires or wires may be plated on both sides. Fig. 2 schematically illustrates an electrodeposited copper foil with nanofilaments or threads on both sides.

The nanofilament copper tape may be handled and placed between the joined components based on an automated manufacturing process similar to other thermal interface sheets. Bonding techniques allow for ideal metal-to-metal attachment, nano-filaments from copper tape can compensate for surface roughness.

The shape and length of the

nanowires

132a, 132b on the copper foil may be individually changed according to a certain surface roughness. The application of this copper foil is shown in fig. 1. A double sided cooled IGBT power module (e.g. middle power module 110) can be attached to the

aluminum heat sinks

120, 140 on each side over the nano-filament foil (e.g. metal substrates 130, 150).

Additionally, the nanofilament foil or tape may be applied at the bonding area by an epoxy-based glue. The tape and glue do not become liquid and remain stationary stable under ambient temperature stress. The viscosity of the epoxy resin glue may be above 400 mPa.

The techniques presented herein allow for ideal metal-to-metal attachment because the glue is characterized by low viscosity and can be absorbed by the nanofilaments 132a, 132 b. The tips of the nanofilaments 132a, 132b may still protrude and contact the surface of the

heat sinks

120, 140 to obtain optimal thermal conductivity.

Fig. 3 shows a schematic diagram illustrating a cross-section of an exemplary cooling power module having roughened surfaces of two engaging members.

The figure shows the rough surface characteristics of the power module 110 shown in fig. 1 and the heat sink 120 shown in fig. 1. Due to the roughened surface of the heat absorbing surface 121b of the heat sink 120, a first cavity 301 is created between the protrusions or teeth in the heat absorbing surface 121 b. The same applies to the upper heat dissipation surface 111a of the power module 110. A second cavity is created between the protrusions or teeth of the upper heat dissipation surface 111a of the power module 110.

In fig. 3, the two protrusions or teeth have different heights, for example, due to different materials of the two surfaces or different fabrication of the surfaces. It will be appreciated that it is also possible for two protrusions or teeth to have the same height, for example when the same material is used.

Each metal surface of the two joined components may be characterized by a certain surface roughness. From mechanics, the principle is known that there are only 3 main mechanical contact points between topographically corrugated surfaces at all times. The remaining surface area is not fully contacted. Dielectric air is a thermally insulating material of λ= 0,0262W/m×k and is not suitable as a thermal conductor. The remaining contact surface may be enlarged by applying a paste-like substrate, for example with aluminium particles, between the joining surfaces to close the air pockets. These so-called thermally conductive silicone grease materials can have thermal conductivities of between λ=0.15 and 0.2W/m×k.

To achieve better thermal conductivity, interconnect dielectrics with higher metal content may be applied to improve thermal performance by increasing switching current. Metal substrates are characterized by much higher thermal conductivity values, such as copper: λ=401W/m×k or aluminum: λ=237W/m×k.

The metal substrate 130 described above with respect to fig. 1 and 2 is a novel method of applying a ductile metal-based substrate material (such as copper) having high thermal conductivity that is capable of closing the gap or cavity 301 shown in fig. 3 between two joining surfaces.

The above-described metal substrate 130 is a copper foil having a high ductile appearance, both sides of which have nano-filaments (wires) to enable desired mechanical and thermal attachment between two bonding surfaces. When the nanofilaments on the foil are pressed together with additional heat, the nanofilaments deform according to the surface roughness profile of each joint part, resulting in excellent thermal conductivity.

Fig. 4 illustrates a photomicrograph 400 of a cross-section of an exemplary cooled power module package 100 according to the present disclosure, showing a thermal interface for heat transfer from the power module to a heat sink.

The figure shows the optimal heat transfer from the power module 110 to the upper heat sink 120 when the metal substrate 130 as described above is applied using the

metal lines

132a, 132b on both sides. The structures of the

metal lines

132a, 132b are irregularly arranged with some air cavities therebetween. These air cavities may be at least partially filled with an adhesive, for example, as described above with respect to fig. 3. An adhesive may be applied to enlarge the contact surface of the two engagement members. For example, the adhesive may include a paste-like substrate with aluminum particles between the joining surfaces to close the air pockets.

The method 500 includes: a power module 110 for electrical power conversion is provided 501, the power module comprising a first module side and a second module side opposite the first module side, wherein the first module side comprises an upper metal layer forming an upper heat dissipation surface 111a of the power module 110, e.g. as described above with respect to fig. 1-4.

The method 500 includes: the heat sink 120 is provided 502, the heat sink 120 comprising a heat absorbing surface 121b opposite the upper heat dissipation surface 111a of the power module 110, e.g. as described above with respect to fig. 1-4.

The method 500 includes: the metal substrate 130 is encapsulated 503 between the heat absorbing surface 121b of the heat spreader 120 and the upper heat dissipating surface 111a of the power module 110, e.g., as described above with respect to fig. 1-4.

The metal substrate 130 includes a first substrate face 131a and a second substrate face 131b opposite the first substrate face 131 a.

The metal substrate 130 includes a first metal line 132a protruding from the first substrate face 131a toward the heat absorbing surface 121b of the heat sink 120, wherein the first metal line 132a is disposed within a first cavity formed within a surface structure of the heat absorbing surface 121b of the heat sink 120.

The metal substrate 130 includes a second metal line 132b protruding from the second substrate face 131b toward the upper heat dissipation surface 111a of the power module 110, wherein the second metal line 132b is disposed within a second cavity formed within the surface structure of the upper heat dissipation surface 111a of the power module 110.

The encapsulation of the metal substrate 130 between the heat absorbing surface 121b of the heat sink 120 and the upper heat dissipating surface 111a of the power module 110 may be performed at a certain temperature and a certain pressure. The higher the temperature, the higher the pressure, and the better the metal connection (and thus the heat dissipation) between the heat sink and the heat dissipation surface of the power module.

However, excessive pressures and temperatures may damage the power module. It has been demonstrated that for protecting the power module, the pressure should be below 3MPa (corresponding to 1 ton). When a pressure of about 5 tons or more is applied, intermetallic phases may be reached. Thus, with this approach, there may be no intermetallic phase between the heat sink and the heat dissipation surface of the power module.

The encapsulation of the metal substrate 130 between the heat absorbing surface 121b of the heat spreader 120 and the upper heat dissipating surface 111a of the power module 110 may be performed at a temperature in the range of about 100 to 150 degrees celsius and at a pressure in the range of between about 20 to 50MPa, for example, as described above with respect to fig. 1-4.

Encapsulating the metal substrate 130 between the heat absorbing surface 121b of the heat spreader 120 and the upper heat dissipating surface 111a of the power module 110 may further include: applying an adhesive between the heat absorbing surface 121b of the heat spreader 120 and the first substrate face 131a of the metal substrate 130; and applying an adhesive between the upper heat dissipation surface 111a of the power module 110 and the second substrate face 131b of the metal substrate 130, such as: as described above with respect to fig. 1-4.

The adhesive may have a first viscosity when the adhesive is applied and a second viscosity after a curing time after the adhesive is applied, wherein the second viscosity may be higher than the first viscosity.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the term "includes," has, "" with, "or other variants thereof is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term" comprising. Furthermore, the terms "example", "e.g. (for example)", and "e.g. (e.g.)" are merely examples, and are not optimal or optimal. The terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms may have been used to indicate that two elements co-operate or interact with each other whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although elements in the following claims are recited in a particular order with corresponding labeling, unless the claim recitations otherwise imply a particular order for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular order.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art will readily recognize that many applications of the present invention are beyond those described herein. While the invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and equivalents thereof, the invention may be practiced otherwise than as specifically described herein.

Claims

1. A cooling power module package (100), comprising:

a power module (110) for electric power conversion, the power module comprising a first module side and a second module side opposite the first module side, wherein the first module side comprises an upper metal layer forming an upper heat dissipation surface (111 a) of the power module (110);

a heat sink (120) comprising a heat absorbing surface (121 b) opposite the upper heat dissipating surface (111 a) of the power module (110);

a metal substrate (130) enclosed between the heat absorbing surface (121 b) of the heat sink (120) and the upper heat dissipating surface (111 a) of the power module (110),

the metal substrate (130) includes a first substrate surface (131 a) and a second substrate surface (131 b) opposite to the first substrate surface (131 a),

the metal substrate (130) comprises a first metal line (132 a) protruding from the first substrate surface (131 a) towards the heat absorbing surface (121 b) of the heat sink (120), wherein the first metal line (132 a) is arranged within a first cavity formed within a surface structure of the heat absorbing surface (121 b) of the heat sink (120), and

the metal substrate (130) comprises a second metal line (132 b) protruding from the second substrate surface (131 b) towards the upper heat dissipation surface (111 a) of the power module (110), the second metal line (132 b) being arranged within a second cavity formed within a surface structure of the upper heat dissipation surface (111 a) of the power module (110).

2. The cooling power module package (100) of claim 1, wherein,

-said surface structure of said heat absorbing surface (121 b) of said heat sink (120) is rugged, thereby forming said first cavity; and is also provided with

The surface structure of the upper heat dissipation surface (111 a) of the power module (110) is rugged, thereby forming the second cavity.

3. The cooling power module package (100) according to claim 1 or 2, characterized in that,

the metal substrate (130) comprises a metal foil, wherein the first metal line (132 a) and the second metal line (132 b) protrude from both sides of the metal foil.

4. The cooling power module package (100) of claim 3, wherein the first metal lines (132 a) and the second metal lines (132 b) have a length in the range of about 5 microns and 50 microns,

the first metal line (132 a) and the second metal line (132 b) have diameters in a range of about 0.1 microns and 2 microns, and

the thickness of the metal foil is in the range of about 5 microns and 400 microns.

5. The cooling power module package (100) of any of the preceding claims, wherein a length of the first wire (132 a) is different than a length of the second wire (132 b); and/or

The diameter of the first wire (132 a) is different from the diameter of the second wire (132 b).

6. The cooling power module package (100) of any of claims 1 to 4, wherein a length of the first wire (132 a) corresponds to a length of the second wire (132 b); and/or

The diameter of the first wire (132 a) corresponds to the diameter of the second wire (132 b).

7. The cooling power module package (100) of any of the preceding claims, wherein the first metal wire (132 a) is irregularly arranged within the one cavity; and the second metal lines (132 b) are irregularly arranged within the second cavity.

8. The cooling power module package (100) of any of the preceding claims, wherein the first metal wires (132 a) are randomly arranged within the first cavity; and the second metal lines (132 b) are randomly arranged within the second cavity.

9. The cooling power module package (100) of any of the preceding claims, wherein the first wire (132 a) is bent one or more times within the first cavity; and the second wire (132 b) is bent one or more times within the second cavity.

10. The cooling power module package (100) according to any of the preceding claims, comprising:

an adhesive layer at least partially fills the first cavity between the first metal lines (132 a).

11. The cooling power module package (100) of claim 10, wherein the adhesive layer covers only a portion of the first metal line (132 a) that is not in contact with the heat absorbing surface (121 b) of the heat sink (120).

12. The cooling power module package (100) of claim 10 or 11, comprising:

one or more voids in a portion of the first cavity not filled by the adhesive layer or the first metal line (132 a).

13. The cooling power module package (100) of any of the preceding claims, wherein the first metal wire (132 a) and the second metal wire (132 b) are made of copper.

14. The cooling power module package (100) according to any of the preceding claims, wherein the thermal conductivity between the upper heat dissipation surface (111 a) of the power module (110) and the heat absorption surface (121 b) of the heat sink (120) is above 300W/m x K.

15. The cooling power module package (100) of any of the preceding claims, wherein the thickness of the first metal lines (132 a) and the second metal lines (132 b) is below 1 micron.

16. The cooling power module package (100) according to any of the preceding claims, comprising:

a second heat sink (140) comprising a heat absorbing surface (141 a) opposite to the lower heat dissipating surface (111 b) of the power module (110);

a second metal substrate (150) enclosed between the heat absorbing surface (141 a) of the second heat sink (140) and the lower heat dissipating surface (111 b) of the power module (110),

the second metal substrate (150) includes a first substrate surface (151 a) and a second substrate surface (151 b) opposite to the first substrate surface (151 a),

the second metal substrate (150) comprises a first metal line (152 a) protruding from the first substrate surface (151 a) towards the lower heat dissipation surface (111 b) of the power module (110), wherein the first metal line (152 a) is arranged within a third cavity formed within a surface structure of the lower heat dissipation surface (111 b) of the power module (110);

the second metal substrate (130) comprises a second metal line (152 b) protruding from the second substrate surface (151 b) towards the heat absorbing surface (141 a) of the second heat sink (140), wherein the second metal line (152 b) is arranged in a fourth cavity formed in the surface structure of the heat absorbing surface (141 a) of the second heat sink (140).

17. A method (500) for producing a cooling power module package (100), the method comprising:

providing (501) a power module (110) for electric power conversion, the power module comprising a first module side and a second module side opposite the first module side, wherein the first module side comprises an upper metal layer forming an upper heat dissipation surface (111 a) of the power module (110);

-providing (502) a heat sink (120), the heat sink (120) comprising a heat absorbing surface (121 b) opposite to the upper heat dissipating surface (111 a) of the power module (110); and

encapsulating (503) a metal substrate (130) between the heat absorbing surface (121 b) of the heat spreader (120) and the upper heat dissipating surface (111 a) of the power module (110),

The metal substrate (130) comprises a second metal line (132 b) protruding from the second substrate surface (131 b) towards the upper heat dissipation surface (111 a) of the power module (110), wherein the second metal line (132 b) is arranged within a second cavity formed within a surface structure of the upper heat dissipation surface (111 a) of the power module (110).

18. The method of claim 17, wherein encapsulating the metal substrate (130) between the heat absorbing surface (121 b) of the heat spreader (120) and the upper heat dissipating surface (111 a) of the power module (110) is performed at a temperature in a range of about 100 to 150 degrees celsius and at a pressure in a range of about 20 to 50 Mpa.

19. The method of claim 17 or 18, wherein encapsulating the metal substrate (130) between the heat absorbing surface (121 b) of the heat spreader (120) and the upper heat dissipating surface (111 a) of the power module (110) comprises:

-applying an adhesive between the heat absorbing surface (121 b) of the heat spreader (120) and the first substrate surface (131 a) of the metal substrate (130); and

an adhesive is applied between the upper heat dissipation surface (111 a) of the power module (110) and the second substrate surface (131 b) of the metal substrate (130).

20. The method of claim 19, wherein the adhesive has a first viscosity when the adhesive is applied; and

the adhesive has a second viscosity after a curing time after application of the adhesive,

the second viscosity is higher than the first viscosity.