Fluid-permeable cooler for cooling a power module

Abstract

The present invention relates to a fluid-permeable cooler (100) for cooling a power module (208) that comprises a power substrate. The fluid-permeable cooler (101) comprises 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 interconnected by means of a soldering process and define a cooling channel (111) which is permeable by a fluid and in which the cooling structure (1) is located. The first metal part (101) comprises a receiving region (109) to which the power module (208) can be attached. The first metal part (101) is made from a metal material which has an expansion coefficient that is greater than the expansion coefficient of the power substrate (208). The invention also relates to a power electronics assembly (1000) having a cooler (100) of this kind and a power module (200).

Description

[0001] Description

[0002] title

[0003] Fluid-flow cooler for cooling a power module

[0004] State of the art

[0005] The present invention relates to a fluid-permeable cooler for cooling a power module with a power substrate. Furthermore, the invention relates to a power electronics assembly comprising a power module that includes a power substrate and such a fluid-permeable cooler. The power electronics assembly can, in particular, comprise a plurality of power modules that are cooled by the cooler.

[0006] Power semiconductors in a power module in power electronics carry high electrical currents. Combined with switching losses, the resulting conduction losses cause high heat dissipation, which must be dissipated within a very small area. The maximum permissible semiconductor temperature is critical to failure, which is why minimizing the thermal resistance between the semiconductor and the coolant is crucial. For efficient cooling, the power substrates are applied to a fluid-permeable cooler.

[0007] Disclosure of the invention

[0008] The fluid-flow cooler according to the invention for cooling a power module comprising a power substrate has the advantages of a flexible cooler design and good cooling performance. This is achieved by a fluid-flow cooler for cooling a power module with a power substrate, which comprises a first metal part, a second metal part, and a cooling structure. The first metal part and the second metal part are connected to one another by means of a soldering process. In other words, the first metal part and the second metal part are soldered together. The first metal part and the second metal part define a cooling channel through which a fluid can flow and in which the cooling structure is arranged. The first metal part has a receiving area to / on which the power module can be fastened.The first metal part is formed from a metal material having a coefficient of expansion greater than the coefficient of expansion of the power substrate, thereby reducing heat-induced expansion of the first metal part. Before the soldering process, the first metal part can advantageously be a metal part pre-plated, in particular roll-clad, with a solder layer. Accordingly, the second metal part can advantageously be a metal part pre-plated, in particular roll-clad, with a solder layer before the soldering process. Alternatively or in addition to the pre-clad configuration of the first metal part and / or the second metal part, the connection between the first metal part and the second metal part can be made using at least one brazing foil or brazing paste. In particular, the aforementioned coefficients of expansion can be linear expansion coefficients.The power substrate preferably comprises a carrier plate and at least one conductor track. The expansion coefficient of the first metal part can, for example, be at least twice, in particular at least three times, as high as the expansion coefficient of the power substrate.

[0009] The subclaims show preferred developments of the invention.

[0010] The power substrate and the first metal part preferably have different yield strengths. The yield strength is a material property and describes the mechanical stress up to which a material can be elastically deformed.

[0011] The metal material may preferably be a pure metal or a metal alloy.

[0012] Preferably, the metal material of the first metal part has a yield strength after the soldering process that is greater than 30 N / mm 2In other words, the metal material of the first metal part in its soldered state preferably has a yield strength greater than 30 N / mm 2This means that the metal material of the first metal part has the aforementioned yield strength after its thermal treatment resulting from the soldering process. This ensures that when the first metal part bends due to the different expansion coefficients of the first metal part and the power substrate, the first metal part only deforms in the elastic range below the yield strength. At an initial temperature, the first metal part returns to its original state. This prevents plastic deformation, in particular bending, of the first metal part, particularly in the area of ​​the power substrate, which could otherwise occur upon heating / cooling due to the greater expansion / shrinkage of the first metal part than the power substrate and which would steadily increase under cyclic loads.

[0013] In particular, the metal material may have an upper yield strength and a lower yield strength, in which case the yield strength greater than 30 N / mm 2 corresponds to the upper yield point.

[0014] Advantageously, a plastic deformation of the first metal part, the metal material of which has a yield strength of greater than 30 N / mm 2 with a heat flux density of less than 600000 W / m 2 and / or a temperature difference between an initial temperature and a final temperature of at least 120°C must be avoided.

[0015] The metal material of the first metal part has a thermal conductivity coefficient greater than 190 W / (m*K), preferably greater than 200 W / (m*K). Thus, heat generated by the power module can be efficiently transferred from the first metal part to the fluid flowing through the cooling channel.

[0016] The first metal part and the second metal part are preferably joined together by means of a brazing process. This means that a brazing bonding layer is preferably located between the first metal part and the second metal part. This means that the first metal part and the second metal part are preferably brazable.

[0017] Advantageously, the cooling structure can contact the first metal part and / or the second metal part. In particular, the cooling structure can be connected to the first metal part and / or the second metal part, advantageously by means of a brazing process. The brazing layer that connects the first metal part and the second metal part to each other can preferably also connect the cooling structure to the first metal part and / or the second metal part.

[0018] According to an advantageous embodiment of the invention, the metal material of the first metal part comprises magnesium (i.e., the metal material is a metal alloy), while the second metal part is formed from a metal material that does not comprise magnesium. The second metal part can be a pure metal part or a metal alloy. In this embodiment of the invention, the mass percentage of magnesium in the mass of the first metal part is less than 1%.

[0019] According to an alternative embodiment of the invention, the metal material of the first metal part comprises magnesium, wherein the second metal part is formed from a metal material that comprises magnesium. This means that both the metal material of the first metal part and the metal material of the second metal part are metal alloys and each comprise magnesium. Advantageously, a mass percentage of magnesium from the mass of the first metal part and from the mass of the second metal part is less than 1% in total. Particularly preferably, the mass percentage of magnesium in each metal part of the first metal part and the second metal part can be less than 0.5% of the mass of the corresponding metal part.

[0020] Due to the specified mass percentages, the first metal part / the two metal parts can be joined together in a simple manner by means of a brazing process if the first metal part / the two metal parts comprise magnesium.

[0021] Preferably, the metal material of the first metal part is an aluminum alloy, wherein the metal material of the first metal part has the material state O after the soldering process. In other words, the metal material of the first metal part has the material state O in the soldered state of the first metal part. The material state O can be used to designate products in which the properties required for the soft-annealed state are achieved through hot forming processes. Within the scope of the present invention, the cooling structure is preferably understood as a surface-enlarging, flow-guiding, and heat-transfer-enhancing structure.

[0022] The cooling structure can preferably comprise a cooling fin structure and / or a pin structure (cooling pin structure). It is also conceivable that the cooling structure alternatively or additionally also comprises a cooling structure element or a plurality of cooling structure elements that have / have a different shape than a cooling fin or a pin. In particular, it is possible for the cooling structure to have a plurality of cooling structure elements of different shapes. For example, it is possible for the cooling structure to have a cooling fin and a pin, or a plurality of cooling fins and a plurality of pins. A cooling fin and a pin can each be referred to in particular as a cooling structure element within the scope of the present invention.

[0023] The cooling fin structure can preferably comprise (only) one cooling fin or a plurality of cooling fins, which are preferably arranged one behind the other in a flow direction. The flow direction corresponds in particular to a main flow direction of the fluid used as coolant, which flows through through-openings formed by the cooling fin(s). The main flow direction is in particular the direction in which the fluid primarily flows, i.e., the direction in which a velocity component of the fluid is greater than a velocity component of the fluid in a direction perpendicular to the main flow direction. The main flow direction preferably corresponds to an introduction direction of the fluid into the fluid-flowable cooler.

[0024] The cooling fin structure can also be referred to as a turbulator. Preferably, a cooling fin is formed from a wave profile that repeats periodically in a repeating direction.

[0025] The cooling structure is preferably formed at least partially, in particular completely, from a material and / or coated with a material having a thermal conductivity coefficient greater than 200 W / (m K). Advantageously, the cooling structure can be formed at least partially, in particular completely, from aluminum or coated with aluminum. In particular, these embodiments relate to the cooling structure element(s) of the cooling structure.

[0026] In the context of the present invention, the fluid which can flow through the cooler can also be referred to as cooling fluid.

[0027] The invention further relates to a power electronics arrangement comprising a power module with a power substrate and a previously described fluid-flow cooler. The power module is attached to / on the receiving area of ​​the first metal part of the fluid-flow cooler by means of the power substrate.

[0028] The power substrate may preferably be made of copper and / or ceramic (AMB / DBC power substrate; AMB: active metal braze; DBG: direct copper bonding).

[0029] To achieve low thermal resistance between the power substrate and the cooler, in particular the first metal part, the power substrate can preferably be joined to the cooler, in particular the first metal part, using a soft soldering process, or optionally also a sintering process. This means that the power module is preferably joined to the fluid-permeable cooler or the first metal part using a layer produced by a soft soldering process or a sintering process, which is thus accordingly a soft solder layer or sintered layer.

[0030] The power module preferably comprises one or more power semiconductors. A power semiconductor generates heat during operation of the power module, which can be dissipated by the cooler.

[0031] Short description of the drawing

[0032] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0033] Figure 1 is a schematic simplified sectional view of a power arrangement according to the invention with a fluid-flow-through cooler according to an embodiment of the invention.

[0034] Embodiment of the invention

[0035] With reference to Figure 1, a power electronics arrangement 1000 according to the invention comprising a power module (power electronics assembly) 200 and a fluid-flow cooler 100 according to an exemplary embodiment of the invention is described below. It is also possible for the power electronics arrangement 1000 to comprise a plurality of power modules 200.

[0036] As can be seen from Figure 1, the power module 200 comprises a carrier plate 204, conductor tracks 203, 205, and power semiconductors 201. The conductor tracks 203, 205 are designed in particular as copper conductor tracks, with the carrier plate 204 preferably being made of ceramic.

[0037] The power semiconductors 201 are applied to the conductor track 203 by means of a layer 202. Layer 202 is formed, in particular, as a solder or sintered layer.

[0038] The conductor tracks 203, 205 together with the carrier plate 204 form a power substrate 208. The power substrate 208 and thus the power module 200 are joined to the fluid-flowable cooler 100, in particular to a receiving area 109 of the first metal part 101 of the cooler 100, by means of a layer 206 produced by a soft soldering process or a sintering process, which is thus correspondingly a soft solder layer or sintered layer.

[0039] The fluid-flow cooler 100 further comprises a second metal part 102, which is connected to the first metal part 101 by means of a soldering process. In other words, the first metal part 101 and the second metal part 102 are soldered together. In particular, the soldering process is a brazing process, so that the first metal part 101 and the second metal part 102 are connected by means of a connecting brazing layer 103. In particular, both metal parts 101, 102 are formed as metal sheets. Figure 1 further shows that the first metal part 101 is an upper part and the second metal part 102 is a lower part of the housing 110. The first metal part 101 faces the power module 200, while the second metal part 102 faces away from the power module 200. Furthermore, in this embodiment, the first metal part 101 is plate-shaped, wherein the second metal part 102 has a plate-shaped region and a region with a trapezoidal cross-section.However, it is also possible for the first metal part 101 and the second metal part 102 to have other shapes. The second metal part 102 can advantageously be manufactured using a deep-drawing process.

[0040] Between layer 206 and cooler 100, in particular between layer 206 and first metal part 101, there is advantageously a mediating layer 107, which is firmly connected to first metal part 101 and allows wetting of layer 206. The mediating layer 107 is an optional feature of power electronics assembly 1000 and can in particular be considered either as a separate part or as part of cooler 100.

[0041] The first metal part 101 and the second metal part 102, which, when joined together, form a housing 110 of the cooler 100, define an interior space that serves as a cooling channel 111 of the cooler 100. In other words, the interconnected metal parts 101, 102 define the cooling channel 111 of the cooler 100. The cooling channel 111 is advantageously closed, with an inlet and an outlet for the fluid being arranged on the housing of the cooler 100.

[0042] A cooling structure 1 is arranged in the cooling channel 111. It serves as a surface-enlarging structure for a fluid used as a coolant, and as a structure that guides flow and increases heat transfer. The cooling structure 1 is connected to the first metal part 101 and the second metal part 102 by means of the connecting brazing layer 103.

[0043] In particular, the cooling structure 1 comprises or is a cooling fin structure. For this purpose, the cooling fin structure has a cooling fin 10, which extends in the direction of the length of the cooling channel 111 or a flow direction 500 of the fluid. In this case, the cooling structure 1 corresponds to the cooling fin 10. The flow direction 500 corresponds in particular to a

[0044] Main flow direction of the fluid used as coolant.

[0045] As can also be seen from Figure 1, the cooling fin 10 is formed from a wave profile that repeats periodically in a repeating direction 501. Through-openings 14 through which the fluid can flow are formed through the cooling fin 10. The cooling fin 10 is preferably formed from and / or coated with a material that has a thermal conductivity coefficient greater than 200 W / (m K). Advantageously, the cooling fin 10 can be made of aluminum or coated with aluminum. It is also possible to use other thermally conductive materials for the cooling fin 10 and / or its layer.

[0046] Although in this exemplary embodiment the cooling fin structure has only one cooling fin 10, it is also possible for the cooling fin structure to have a plurality of cooling fins 10, which are arranged one behind the other in particular in the flow direction 500 of the fluid.

[0047] The first metal part 101 is formed from a metal material having a coefficient of expansion greater than the coefficient of expansion of the power substrate 200, thereby reducing thermal expansion of the first metal part 101. The metal material of the first metal part 101 is a metal alloy, preferably an aluminum alloy. However, it is also possible to use a pure metal as the metal material of the first metal part 101.

[0048] By attaching the power substrate 208 to / on the receiving area 109 of the first metal part 101, the expansion / shrinkage of the first metal part 101 is inhibited during thermal expansion / shrinkage due to the different thermal expansion coefficients of these components, causing the first metal part 101 and thus the cooler 100 to bend.

[0049] To prevent plastic deformation due to bending, a high-strength metal alloy, preferably a high-strength aluminum alloy, is used for the metal material of the first metal part 101, so that the first metal part 101 deforms during heat-induced bending only in the elastic range below the yield point of the metal alloy. When the first metal part 101 no longer experiences expansion / shrinkage, i.e., at the initial temperature, the first metal part 101 returns to its original state. The yield point of the metal alloy for the metal material of the first metal part 101 is greater than 30 N / mm 2. It should be noted that the yield strength of the metal alloy is the yield strength that the metal alloy has after the soldering process, ie after the heat treatment of the first metal part 101 that has taken place during the soldering process. Due to the yield strength of the metal alloy, the first metal part 101 is advantageously designed to only be in the elastic range at a heat flux density of less than 600,000 W / m 2 and / or a temperature difference between an initial temperature and a final temperature of at least 120°C

[0050] If the metal alloy of the first metal part 101 is an aluminum alloy, it advantageously has the material state O after the soldering process. In other words, the aluminum alloy of the first metal part 101 advantageously has the material state O in the soldered state of the first metal part 101.

[0051] The power substrate 208 and the first metal part 101 preferably have different yield strengths.

[0052] The metal alloy of the first metal part 101 has a thermal conductivity coefficient greater than 190 W / (m*K), preferably greater than 200 W / (m*K). Thus, heat generated by the power module 200 can be efficiently transferred from the first metal part 101 to the fluid flowing through the cooling channel 111 and dissipated by the fluid, thereby cooling the power module 200.

[0053] The second metal part 102 is advantageously also formed from an aluminum alloy. Both metal parts 101, 102 can comprise magnesium. In order to be able to join the two metal parts 101, 102 to one another by means of 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 less than 1% in total. In particular, the mass percentage of magnesium in the first metal part 101 can be less than 0.5% of the mass of the first metal part 101, and the mass percentage of magnesium in the second metal part can be less than 0.5% of the mass of the second metal part 102. To produce the fluid-flow-through cooler 100, the first metal part 101, the second metal part 102, and the cooling structure 1 can preferably be joined together in the same manufacturing step by means of a brazing process.

Claims

Claims 1. A fluid-flow cooler (100) for cooling a power module (200) comprising a power substrate (208), wherein the fluid-flow cooler (101): • a first metal part (101); • a second metal part (102), wherein the first metal part (101) and the second metal part (102) are connected to one another by means of a soldering process and define a cooling channel (111) through which a fluid can flow; and • a cooling structure (1) arranged in the cooling channel (111), wherein the first metal part (101) has a receiving area (109) to which the power module (208) can be fastened, and wherein the first metal part (101) is formed from a metal material having a coefficient of expansion that is greater than a coefficient of expansion of the power substrate (208).

2. Fluid-flow cooler (100) according to claim 1, wherein the metal material of the first metal part (101) after the soldering process has a yield strength greater than 30 N / mm 2 has.

3. Fluid-flow cooler (100) according to one of the preceding claims, wherein the metal material of the first metal part (101) has a thermal conductivity coefficient greater than 190 W / (m*K), preferably greater than 200 W / (m*K).

4. A fluid-flow cooler (100) according to any one of the preceding claims, wherein the first metal part (101) and the second metal part (102) are joined together by means of a brazing process.

5. Fluid-flow cooler (100) according to one of the preceding claims, wherein the metal material of the first metal part (101) comprises magnesium, and the second metal part is formed from a metal material which comprises no magnesium, wherein a mass percentage of magnesium in the mass of the first metal part (101) is less than 1%, or wherein the metal material of the first metal part (101) comprises magnesium, and the second metal part is formed from a metal material which comprises magnesium, wherein a mass percentage of magnesium in the mass of the first metal part (101) and in the mass of the second metal part (102) in total is less than 1%. Fluid-flow cooler (100) according to one of the preceding claims, wherein the metal material of the first metal part (101) is an aluminum alloy which has the material state O after the soldering process. Fluid-flow cooler (100) according to one of the preceding claims, wherein the metal material of the first metal part (101) is a metal alloy. Fluid-flow cooler (100) according to one of claims 1 to 4, wherein the metal material of the first metal part (101) is a pure metal.A power electronics arrangement (1000) comprising a power module (200) with a power substrate (208), and a fluid-flow cooler (100) according to one of the preceding claims, wherein the power module (200) is attached to the receiving area (109) of the first metal part (101) of the fluid-flow cooler (100) by means of the power substrate (208). The power electronics arrangement (1000) according to claim 9, wherein the power substrate (100) is made of copper and / or ceramic.

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