Cooler with fluid flow through it for cooling a power module

Abstract

The present invention relates to a cooler (100) through which a fluid can flow for cooling a power module (208) including a power board. The cooler (101) through which a fluid can flow includes a first metal part (101), a second metal part (102), and a cooling structure (1). The first metal part (101) and the second metal part (102) are joined to each other by a brazing process to define a cooling passage (111) through which a fluid can flow and in which the cooling structure (1) is disposed. The first metal part (101) has a receiving area (109) through which a power module (208) can be attached. The first metal part (101) is made of a metallic material having a coefficient of expansion greater than that of the power board (208). The present invention also relates to a power electronics assembly (1000) including such a cooler (100) and a power module (200).

Description

[Technical Field]

[0001] The present invention relates to a cooler through which a fluid can flow for cooling a power module having a power substrate. Furthermore, the present invention relates to a power electronics assembly having a power module including a power substrate and a cooler through which a fluid can flow of this kind. The power electronics assembly can in particular include several power modules cooled by the cooler. [Background technology]

[0002] Power semiconductors in power modules in power electronics carry high currents. The resulting conduction losses, together with switching losses, result in high heat output, which must be dissipated over a very small area. Since the maximum permissible semiconductor temperature poses a risk of failure, it is therefore crucial to minimize the thermal resistance between the semiconductor and the coolant. For efficient cooling, coolers that allow a fluid to flow through the power board are used. Summary of the Invention

[0003] The fluid-throughflowable cooler according to the present invention for cooling a power module including a power substrate has the advantages of flexible cooler design and good cooling output. This is achieved by a fluid-throughflowable cooler for cooling a power module having a power substrate, comprising a first metal part, a second metal part, and a cooling structure. The first metal part and the second metal part are joined to each other by a brazing process. In other words, the first metal part and the second metal part are brazed to each other. The first metal part and the second metal part define a cooling passage through which a fluid can flow and in which the cooling structure is disposed. The first metal part has a receiving area on or onto which the power module can be mounted. The first metal part is made of a metal material having a coefficient of expansion greater than that of the power substrate, thereby reducing thermal expansion of the first metal part. Prior to the brazing process, the first metal part may be pre-plated, particularly a roll-plated metal part, with a brazing layer. Accordingly, the second metal part may be a metal part that is preferably pre-plated, in particular roll-plated, with a brazing layer prior to the brazing process. Alternatively or in addition to the pre-plated configuration of the first and / or second metal parts, the connection between the first and second metal parts may be achieved by at least one brazing foil or brazing paste. In particular, the aforementioned coefficients of expansion may be linear coefficients of expansion. The power substrate preferably includes a support plate and at least one strip conductor. The coefficient of expansion of the first metal part may be, for example, at least twice, in particular at least three times, greater than the coefficient of expansion of the power substrate.

[0004] The dependent claims present developments of the invention.

[0005] The power substrate and the first metallic portion preferably have different yield points, which is a characteristic of a material and indicates how much mechanical stress the material can withstand before it can be elastically deformed.

[0006] The metallic material may preferably be a pure metal or an alloy.

[0007] The metal material of the first metal part has a resistance of 30 N / mm after the brazing process. 2 In other words, the metal material of the first metal portion preferably has a yield point higher than 30 N / mm when brazed. 2 Preferably, the metal material of the first metal part has a higher yield point than the power substrate. This means that the metal material of the first metal part has the aforementioned yield point after the heat treatment caused by the brazing process. In this way, if bending of the first metal part occurs due to the different expansion coefficients of the first metal part and the power substrate, it is ensured that the first metal part deforms only in the elastic region below the yield point. At the initial temperature, the first metal part returns to its original state. This prevents plastic deformation, especially distortion, of the first metal part, especially in the region of the power substrate, which would otherwise occur due to the first metal part's stronger expansion / contraction during heating / cooling than the power substrate and which would continually increase under cyclic loads.

[0008] In particular, the metallic material may have an upper and a lower yield point, in this case 30 N / mm 2 The higher yield point corresponds to the upper yield point.

[0009] Metal material is 30N / mm 2 The plastic deformation of the first metal part having a yield point higher than 600,000 W / m 2 Preferably, this can be avoided under a heat flux density less than 100° C. and / or under a temperature difference between the initial and final temperatures of at least 120° C.

[0010] The metal material of the first metal part has a resistance of 190 W / (m * K), preferably greater than 200 W / (m * K) in order to efficiently transfer heat generated by the power module from the first metal part to the fluid flowing through the cooling passages.

[0011] The first metal part and the second metal part are preferably joined together by a brazing process, i.e. there is preferably a bonding braze layer between the first metal part and the second metal part, i.e. the first metal part and the second metal part are preferably brazable.

[0012] Preferably, the cooling structure can be in contact with the first metal part and / or the second metal part. In particular, the cooling structure can be bonded to the first metal part and / or the second metal part, preferably by a brazing process. Preferably, the bonding braze layer bonding the first metal part and the second metal part to each other can also bond the cooling structure to the first metal part and / or the second metal part.

[0013] In a preferred embodiment of the present invention, the metallic material of the first metallic part comprises magnesium (i.e., the metallic material is an alloy), and the second metallic part is composed of a metallic material that does not contain magnesium. In this case, the second metallic part may be a pure metallic part or may be an alloy. The mass percentage of magnesium in the mass of the first metallic part is less than 1% in this embodiment of the present invention.

[0014] In an alternative embodiment of the present invention, the metallic material of the first metal portion comprises magnesium, and the second metal portion comprises a metallic material comprising magnesium. That is, the metallic material of the first metal portion and the metallic material of the second metal portion are both alloys, each comprising magnesium. Preferably, the total mass percentage of magnesium in the mass of the first metal portion and the mass of the second metal portion is less than 1%. It is particularly preferred that the mass percentage of magnesium in each of the first metal portion and the second metal portion is less than 0.5% of the mass of the corresponding metal portion.

[0015] If the first metal part / both metal parts contain magnesium, the above-mentioned mass percentages allow the first metal part / both metal parts to be joined to each other in a simple manner by a brazing process.

[0016] The metallic material of the first metal portion is preferably an aluminum alloy, and the metallic material of the first metal portion has a material state O after the brazing process. In other words, the metallic material of the first metal portion has a material state O when the first metal portion is in the brazed state. The material state O can refer to a product in which the properties required for the soft-annealed state are achieved by a hot forming method.

[0017] Cooling structures are preferably understood in the context of the present invention to be structures that extend the surface, guide the flow and increase the heat transfer.

[0018] The cooling structure preferably includes a cooling rib structure and / or a pin structure (cooling pin structure). Alternatively or additionally, the cooling structure may include one or more cooling structural members having a different shape from the cooling rib or pin. In particular, the cooling structure may include multiple cooling structural members each having a different shape. For example, the cooling structure may include one cooling rib and one pin, or multiple cooling ribs and multiple pins. The cooling rib and the pin may each be specifically referred to as a cooling structural member in the context of the present invention.

[0019] The cooling rib structure can preferably comprise one cooling rib or, preferably, several cooling ribs arranged one behind the other in the through-flow direction. The through-flow direction corresponds in particular to the main flow direction of the fluid used as coolant, which flows through the through-holes formed by one cooling rib (or several cooling ribs). The main flow direction is in particular the direction in which the fluid mainly flows, i.e., the direction in which the velocity component of the fluid is greater than the velocity component of the fluid perpendicular to the main flow direction. The main flow direction preferably corresponds to the direction in which the fluid is introduced into the cooler through which the fluid can flow.

[0020] The cooling rib structure may also be specifically referred to as a turbulator. The cooling rib preferably comprises a wave profile that repeats periodically in a repeating direction.

[0021] The cooling structure is preferably at least partially, in particular entirely, made of and / or coated with a material having a thermal conductivity coefficient greater than 200 W / (m·K). Preferably, the cooling structure is at least partially, in particular entirely, made of or may be coated with aluminum.

[0022] In particular, these embodiments are directed to cooling structural members of a cooling structure.

[0023] In the context of the present invention, the fluid that can flow through the cooler may also be specifically referred to as cooling fluid.

[0024] The present invention further relates to a power electronics assembly including a power module with a power substrate and the above-described cooler through which a fluid can flow, the power module being mounted by the power substrate on / above a receiving area of ​​the first metal part of the cooler through which a fluid can flow.

[0025] The power substrate may preferably consist of copper and / or ceramic (AMB / DBC - power substrate, AMB: active metal braze; DBC: direct copper bonding).

[0026] For the purpose of achieving a low thermal resistance between the power board and the cooler, in particular between the first metal part, the power board can be preferably joined to the cooler, in particular to the first metal part, by a soft soldering process or, alternatively, by a sintering process, i.e. the power module is preferably joined to the cooler, or to the first metal part, through which a fluid can flow, by a layer produced by a soft soldering or sintering process, which is a soft solder layer or a sintered layer, respectively.

[0027] The power module preferably includes one or more power semiconductors, which generate heat during operation of the power module, which can be dissipated through a cooler. Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic, simplified cross-sectional view of a power assembly according to the present invention having a cooler through which a fluid can flow according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] 1, a power electronics assembly 1000 according to the invention is described, which comprises a power module (power electronics structural unit) 200 and a cooler 100 through which a fluid can flow according to an embodiment of the invention. It is also possible for the power electronics assembly 1000 to comprise a plurality of power modules 200.

[0030] 1, the power module 200 includes a support plate 204, strip conductors 203 and 205, and a power semiconductor 201. The strip conductors 203 and 205 are preferably configured as copper strip conductors, and the support plate 204 is preferably made of ceramic.

[0031] The power semiconductor 201 is mounted on a conductor strip 203 by means of a layer 202, which here is configured in particular as a solder layer or a sintered layer.

[0032] The strip conductors 203, 205 together with the support plate 204 form a power substrate 208. The power substrate 208, and therefore the power module 200, is joined to the cooler 100 through which a fluid can flow, in particular to the receiving area 109 of the first metal part 101 of the cooler 100, by means of a layer 206 which is produced by a soldering or sintering process and which is a solder layer or a sintered layer, respectively.

[0033] The cooler 100 allowing fluid to flow through further comprises a second metal part 102 connected to the first metal part 101 by a brazing process. In other words, the first metal part 101 and the second metal part 102 are brazed to one another. In particular, the brazing process is a hard brazing process, whereby the first metal part 101 and the second metal part 102 are connected by a bonding hard braze layer 103. In particular, both metal parts 101, 102 are configured as thin plates.

[0034] As can be seen more clearly in FIG. 1 , the first metal part 101 is the upper part of the housing 110, and the second metal part 102 is the lower part. The first metal part 101 faces the power module 200, and the second metal part 102 faces away from the power module 200. Furthermore, in this embodiment, the first metal part 101 is configured in a plate-like manner, and the second metal part 102 has a plate-like region and a trapezoidal region in cross section. Alternatively, the first metal part 101 and the second metal part 102 can have other shapes. The second metal part 102 is preferably produced by a deep drawing process.

[0035] Preferably, there is an intermediary layer 107 between the layer 206 and the cooler 100, in particular between the layer 206 and the first metal portion 101, which is fixedly bonded to the first metal portion 101 and allows wetting of the layer 206. The intermediary layer 107 is an optional component of the power electronics assembly 1000, and in particular can be considered as a separate part or as part of the cooler 100.

[0036] The first metal part 101 and the second metal part 102, which when joined together constitute the housing 110 of the cooler 100, define an interior space that serves as the cooling passage 111 of the cooler 100. In other words, the joined metal parts 101 and 102 define the cooling passage 111 of the cooler 100. The cooling passage 111 is preferably closed, and a fluid inlet and outlet are located in the housing of the cooler 100.

[0037] A cooling structure 1 is disposed in the cooling passage 111, which serves as a structure for expanding the surface, guiding the flow of a fluid used as a coolant, and increasing heat transfer. The cooling structure 1 is bonded to the first metal part 101 and the second metal part 102 by a bonding brazing layer 103.

[0038] In particular, the cooling structure 1 includes or is a cooling rib structure, which for this purpose has cooling ribs 10 extending in the length direction of the cooling channel 111 or in the through-flow direction 500 of the fluid. In this case, the cooling structure 1 therefore corresponds to the cooling ribs 10. The through-flow direction 500 corresponds in particular to the main flow direction of the fluid used as coolant.

[0039] As further apparent from FIG. 1 , the cooling ribs 10 are configured with a periodically repeating wave profile in a repeat direction 501. The cooling ribs 10 form through-holes 14 through which a fluid can flow. The cooling ribs 10 are preferably configured from and / or coated with a material having a thermal conductivity greater than 200 W / (m·K). The cooling ribs 10 are preferably made from aluminum or may be coated with aluminum. Other thermally conductive materials may also be used for the cooling ribs 10 and / or their layers.

[0040] Although in this embodiment the cooling rib structure has only one cooling rib 10, the cooling rib structure can also have a plurality of cooling ribs 10 arranged one behind the other in the throughflow direction 500 of the fluid.

[0041] The first metal portion 101 is made of a metal material having a coefficient of expansion greater than that of the power substrate 208, thereby reducing thermal expansion of the first metal portion 101. The metal material of the first metal portion 101 is an alloy, preferably an aluminum alloy. Alternatively, a pure metal may be used as the metal material of the first metal portion 101.

[0042] Mounting the power board 208 on / over the receiving area 109 of the first metal portion 101 prevents the first metal portion 101 from expanding / contracting due to heat based on the different thermal expansion coefficients of these components, thereby causing the first metal portion 101, and thus the cooler 100, to bend.

[0043] To prevent plastic deformation due to bending, a particularly high-strength alloy, preferably a high-strength aluminum alloy, is used for the metal material of the first metal portion 101, so that when thermally induced bending occurs, the first metal portion 101 deforms only in the elastic region below the yield point of the alloy. When the first metal portion 101 no longer expands / contracts, i.e., at the initial temperature, the first metal portion 101 returns to its original state. The yield point of the alloy of the metal material of the first metal portion 101 is here 30 N / mm 2 It should be noted that the yield point of the alloy is the yield point of the alloy after the brazing process of the first metal portion 101, i.e., after the heat treatment performed by the brazing process. The first metal portion 101 has a yield point of 600,000 W / m 2 Preferably, the material is configured to deform only in the elastic region under a heat flux density less than 100° C. and / or a temperature difference between the initial and final temperatures of at least 120° C.

[0044] If the alloy of the first metal portion 101 is an aluminum alloy, it preferably has a material state O after the brazing process. In other words, the aluminum alloy of the first metal portion 101 preferably has a material state O when the first metal portion 101 is in a brazed state.

[0045] Preferably, the power substrate 208 and the first metal portion 101 have different yield points.

[0046] The alloy of the first metal portion 101 has a thermal conductivity of 190 W / (m * K), preferably greater than 200 W / (m * K) in order to efficiently transfer heat generated by the power module 200 from the first metal portion 101 to the fluid flowing through the cooling passages 111 and thereby dissipate the heat, thereby cooling the power module 200.

[0047] Preferably, the second metal part 102 is also made of an aluminum alloy. Both metal parts 101, 102 then contain magnesium. To enable the two metal parts 101, 102 to be joined together by a brazing process, the mass percentage of magnesium in the mass of the first metal part 101 and in the mass of the second metal part 102 is lower than 1% in total. In particular, the mass percentage of magnesium in the first metal part 101 may be lower than 0.5% of the mass of the first metal part 101, and the mass percentage of magnesium in the second metal part may be lower than 0.5% of the mass of the second metal part 102.

[0048] To manufacture the cooler 100 through which a fluid can flow, the first metal part 101, the second metal part 102 and the cooling structure 1 can preferably be joined to one another in the same manufacturing step by means of a brazing process.

Claims

1. A fluid-throughflowable cooler (100) for cooling a power module (200) including a power board (208), the cooler (100) comprising: a first metal part (101); a second metal portion (102), wherein the first metal portion (101) and the second metal portion (102) are joined together by a brazing process and define a cooling passage (111) through which a fluid can flow; a cooling structure (1) arranged in the cooling passage (111), wherein the first metal part (101) has a receiving area (109) to which the power module (200) can be attached, and the first metal part (101) is made of a metal material having an expansion coefficient greater than the expansion coefficient of the power board (208).

2. The metallic material of the first metallic part (101) has a resistance of 30 N / mm after the brazing process. ２ 2. The cooler (100) of claim 1, wherein the cooler (100) has a yield point higher than 0.

15.

3. The metal material of the first metal portion (101) has a resistance of 190 W / (m ＊ K), preferably 200 W / (m ＊ 3. The cooler (100) according to claim 1, wherein the cooler (100) has a heat transfer coefficient greater than 100 kJ / cm.

4. The cooler (100) according to any one of claims 1 to 3, wherein the first metal part (101) and the second metal part (102) are joined to each other by a brazing process.

5. the metallic material of the first metallic portion (101) contains magnesium and the second metallic portion is made of a metallic material that does not contain magnesium, and the mass percentage of magnesium in the mass of the first metallic portion (101) is lower than 1%; or 5. A cooler (100) that allows fluid to flow through as described in any one of claims 1 to 4, wherein the metal material of the first metal portion (101) comprises magnesium, the second metal portion is made of a metal material that comprises magnesium, and the mass percentage of magnesium in the mass of the first metal portion (101) and the mass of the second metal portion (102) is lower than 1% in total.

6. 6. The cooler (100) according to claim 1, wherein the metallic material of the first metallic part (101) is an aluminum alloy having a material state O after the brazing process.

7. The cooler (100) according to any one of claims 1 to 6, wherein the metallic material of the first metallic part (101) is an alloy.

8. The cooler (100) according to any one of claims 1 to 4, wherein the metallic material of the first metallic part (101) is a pure metal.

9. 9. A power electronics assembly (1000) comprising a power module (200) having a power board (208) and a cooler (100) through which a fluid can flow as claimed in any one of claims 1 to 8, wherein the power module (200) is attached to the receiving area (109) of the first metal part (101) of the cooler (100) through which a fluid can flow.

10. The power electronics assembly (1000) of claim 9, wherein the power substrate (100) is comprised of copper and / or ceramic.

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