Cooling unit for tempering heat-generating components of a power module

Abstract

The invention relates to a cooling unit (300) for controlling the temperature of heat-generating components of a power module (200), comprising a heat sink (310) with a cooling structure (315), wherein a contact surface (400) for at least indirectly receiving the heat-generating component is formed on a side of the heat sink (310) facing away from the cooling structure (314), characterized in that the contact surface (400) has a recess (405) for receiving a connecting material in a connection process for connecting the heat-generating component to the heat sink (310). Furthermore, the invention relates to a power module (200) with such a cooling unit (300). In addition, the invention relates to an inverter (130) for an electric drive axle (100). Furthermore, the invention relates to an electric drive axle (100) with an electric machine (125) and such an inverter (130).

Description

[0001] The present invention relates to a cooling unit for controlling the temperature of heat-generating components of a power module, comprising a heat sink with a cooling structure, wherein a contact surface for at least indirectly receiving the heat-generating component is formed on a side of the heat sink facing away from the cooling structure. Furthermore, the invention relates to a power module with such a cooling unit. Furthermore, the invention relates to an inverter for an electric drive axle. Furthermore, the invention relates to an electric drive axle with an electric machine and such an inverter.

[0002] WO 2021 / 105028 A1 discloses a power module for the controllable electrical power supply of a consumer. The power module comprises a plurality of encased power semiconductors, each with an electrically non-insulated heat dissipation surface, a printed circuit board, a heat sink, and one or more insulation plates. The printed circuit board is arranged on a side of the power semiconductors opposite the heat sink in an orthogonal direction. The insulation plate is arranged between the encased power semiconductors and a cooling surface of the heat sink, with one side of each insulation plate being positively connected to an electrically non-insulated heat dissipation surface of a encased power semiconductor and the other side being positively connected to the heat sink.

[0003] Current contact or mounting surfaces of a heat sink of a cooling unit, to which heat-generating components, especially at least partially flat electronic components such as half-bridge packages (also called DDPs), are attached and thermally connected, are typically flat or have pedestals with flat contact surfaces. However, during the connection process of heat-generating components to the heat sink, the heat sink can twist, resulting in disruption of subsequent assemblies.

[0004] An object of the invention is to provide a cooling unit for controlling the temperature of heat-generating components of a power module, which realizes an improvement in the position of a heat-generating component arranged thereon during and after a connection process and enables optimized heat transfer.

[0005] The invention solves this problem by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0006] In a first aspect of the invention, a cooling unit for controlling the temperature of heat-generating components of a power module comprises a heat sink with a cooling structure, wherein a contact surface for at least indirectly receiving the heat-generating component is formed on a side of the heat sink facing away from the cooling structure. According to the invention, the contact surface has a recess for receiving a connecting material in a bonding process for connecting the heat-generating component to the heat sink.

[0007] The term "temperature control" refers to the targeted control and maintenance of the temperature of the power module, particularly of heat-generating components of the power module. Temperature control is performed to achieve or control specific temperature effects. In this context, "temperature control" refers to the cooling or targeted heat dissipation of heat-generating components of the power module.

[0008] The cooling unit acts as a heat sink. The heat sink and the cooling structure of the cooling unit serve to efficiently dissipate the heat from the heat-generating component and thus regulate the temperature of the power module. The cooling structure protrudes into a cavity of a cooling device through which a cooling medium flows, wherein the cooling structure is configured to increase the contact area of ​​the cooling unit with the cooling medium in order to improve heat dissipation. The cooling structure can comprise cooling ribs, cooling fins, lamellar, rod, needle, or pin-shaped cooling elements. The cooling elements of the cooling structure further preferably extend perpendicular to the heat sink. In other words, a longitudinal extent of the cooling element is oriented perpendicular to the surface of the heat sink on which the cooling element is arranged. The heat sinks are preferably formed integrally with the heat sink.The heat sinks and cooling structure are constructed of aluminum or copper to optimize thermal conductivity. The selection and design of the cooling structure depend primarily on the specific requirements of the application. The goal is to effectively dissipate heat from the components mounted on the heat sink and maintain the operating temperature at an acceptable level.

[0009] In this bonding process, a thermally conductive connection is created between the heat-generating component and the heat sink by soldering, sintering, and / or welding. In other words, the heat-generating component can be bonded to the heat sink, for example, by sintering. The layer created between the heat sink and the heat-conducting component during the bonding process is referred to as a thermally conductive or thermal compensation layer.

[0010] Sintering is a manufacturing process in which fine powders are processed into a solid, porous material by heating and applying pressure or compression. During sintering, the powder particles partially fuse, compacting them into a solid. Sintering is advantageous for creating a thermally conductive connection between two components. Sintering can be achieved by applying a layer of fusible / sinterable, generally highly thermally conductive material (e.g., silver, copper, nickel, gold, or a solder) to the heat sink and then sintering it to the contact surface. The layer can be applied in formats such as tape / film, powder, or paste when applied as a separate material, or it can be applied as a wafer backside coating. A sintering paste such as ALPHA® ARGOMAX® 2048 PASTE from Alpha Assembly Solutions Inc. can be used as an example.The sintering paste is a mixture of powdered metal particles and a binding substance used to create electrical or thermal connections. The sintering paste is used during sintering. The sintering paste ensures efficient heat dissipation. Alternatively, the heat-generating component can be bonded to the heat sink by soldering or using an adhesive.

[0011] The contact surface to which the heat-generating component is connected is a cooling surface that absorbs the heat of the component and transfers it accordingly to the cooling medium.

[0012] During the bonding process, i.e., during the production of the heat-conducting compensating layer, the bonding material, on the one hand, accommodates the heat-generating component and, on the other hand, comes into contact with the contact surface of the heat sink, whereby the bonding material penetrates into the recess and fills it. This can improve the relative positioning accuracy between the heat-generating component and the heat sink. Initial tests have shown that the recess on the contact surface can prevent or at least reduce a slight twisting of the heat sink, which was previously process-related, particularly after sintering. Furthermore, the heat transfer performance can be improved. Such a heat sink can also be designed in a simpler and more compact manner, since additional pedestals for accommodating the heat-generating component are no longer required. This results in a reduction in weight and cost.However, for space reasons or other reasons, it may be necessary to provide a pedestal on the heat sink. For this purpose, in one embodiment, the contact surface is arranged on a pedestal of the heat sink.

[0013] The dimensions and shape of the cooling unit are adapted to the shape and design of the inverter components to be cooled. Semiconductor packages of the power module's half-bridges are typically flat components, so it is advantageous if the heat sink, in particular the heat sink's contact surface, is complementarily flat or plate-shaped. In one embodiment, the heat sink is a cooling plate. Thus, the cooling unit is preferably a cooling plate with heat sinks arranged thereon.

[0014] The recess is preferably designed as a groove. In other words, the recess is groove-shaped or in the form of a furrow. The groove can be straight and / or curved. The recess preferably has an annular or spiral geometry. Due to the annular or spiral design of the recess, a relatively large area of ​​the contact surface can have recesses for receiving the connecting material. A partially circular, in particular semicircular, cross-sectional shape of the recess is advantageous to avoid constraints during or after the bonding process.

[0015] Preferably, at least two separate recesses are provided. This allows a relatively large area of ​​the contact surface to be provided with recesses to realize the advantageous properties. The two recesses are preferably connected to each other via a transverse section. With more than two recesses, individual, several, or all recesses can be connected to each other via one or more transverse sections. This allows a coherent network of recesses to be created to ensure a secure hold of the connecting material on the heat sink during and after the bonding process.

[0016] In a further aspect of the invention, a power module for an inverter of an electric drive axle comprises a cooling unit according to the preceding aspect of the invention, wherein the cooling unit is thermally coupled to heat-generating components of the power module. Depending on the design of the power module, a plurality of heat-generating components are provided, which are to be cooled via the cooling unit. For this purpose, the heat sink can have two or more contact surfaces. A separate contact surface can be provided for each heat-generating component. Alternatively, the contact surface can be configured to accommodate a plurality of heat-generating components. The recess or recesses are formed and arranged on the heat sink accordingly.

[0017] In a further aspect of the invention, an inverter comprises a power module proposed herein and a cooling unit, wherein the cooling unit is thermally coupled to a heat-generating component of the inverter. An inverter is a power converter that converts direct current (DC) into alternating current (AC), or vice versa. The inverter can be a rectifier or inverter. The inverter is preferably a fluid-temperature-controlled, in particular fluid-cooled, inverter, whose cooling unit, in particular its heat sink and cooling structure, comes into contact with a temperature-control fluid, in particular a cooling fluid, at least in some regions or sections.

[0018] The heat-generating component of the inverter is a component of the inverter to be cooled, in particular an electronic component or an excitation module for generating an excitation voltage. The inverter is intended for controlling the motor vehicle's engine and for controlling an electric machine of the motor vehicle. The inverter, in particular a power module of the inverter, can have one or more half-bridges, each comprising semiconductor packages. For example, two semiconductor packages form a half-bridge of the power module, wherein several half-bridges are separately controllable in order to actuate an electric machine of the electric drive axle. The respective semiconductor package serves to switch current, in particular for consumers in the several tens of kW range, in particular for electric machines, e.g., for a motor vehicle.The semiconductor packages are considered heat-generating components of the inverter that must not exceed certain temperatures for optimal operation. Accordingly, the semiconductor packages can be thermally coupled to the cooling unit directly or via an optional compensation layer.

[0019] In a further aspect of the invention, an electric drive axle according to the invention, also called an E-axle, comprises an electric machine and an inverter proposed herein. The electric machine is a three-phase electric machine. The preferably fluid-cooled inverter forms a motor controller that controls the electric machine. The inverter is therefore designed in particular to control a three-phase electric machine. In addition to the electric machine, the electric drive axle can comprise an optional transmission to provide a torque and a speed for driving a drive wheel of the motor vehicle. The electric machine is supplied with electrical energy from an energy storage device.

[0020] The electric drive axle, the inverter, the power module, and / or the cooling unit can be advantageously used in a motor vehicle. The motor vehicle can, in particular, comprise a motorcycle, a passenger car, a truck, or a bus. The motor vehicle comprises at least two axles. Preferably, two axles are provided, with at least one of the axles being an electric drive axle and being drivable by at least one electric motor. The motor vehicle is thus an electric vehicle or a hybrid vehicle.

[0021] The above definitions and statements regarding technical effects, advantages, and advantageous embodiments of the cooling unit according to the invention also apply mutatis mutandis to the power module according to the invention according to the second aspect of the invention, to the inverter according to the invention according to the third aspect of the invention, to the electric drive axle according to the invention according to the fourth aspect of the invention, and to the aforementioned motor vehicle, and vice versa. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention.

[0022] The invention will now be described in more detail with reference to the accompanying figures, in which: Fig. 1 is a highly schematic view of a motor vehicle with an electric drive axle; Fig. 2 a highly simplified representation of a structure of an inverter according to the invention of the electric drive axle according to Fig. 1, Fig. 3 a schematic cross-sectional view of a cooling unit according to the invention of a power module according to the invention of the inverter according to Fig. 2; and Fig. 4 a schematic plan view of the heat sink of the cooling unit according to the invention according to Fig. 3;, wherein identical or similar components or elements are provided with the same reference numeral.

[0023] Fig. 1 shows an electric drive axle 100 in a motor vehicle 105. The motor vehicle 105 may additionally include an internal combustion engine 110 connected to a drive wheel 120 of the motor vehicle 105 via a transmission 115. In this case, the motor vehicle 105 would be a hybrid vehicle.

[0024] The electric drive axle 110 comprises an electric machine 125, which can also act on the drive wheel 120, preferably by means of the transmission 115. Furthermore, an inverter 130 in the form of a power inverter is provided, which can be supplied with electrical energy from an electrical energy storage device 135. The electrical energy storage device 135 is preferably electrochemically constructed, but a fuel cell or another power source can also be used, for example. The inverter 130 is preferably configured to provide phase-shifted alternating currents to the electric machine 125. The machine 125 is implemented, for example, as a permanent-magnet synchronous machine, but other embodiments are also possible. The voltages and frequencies of the alternating currents provided can be determined such that the electric machine 125 converts a predetermined torque or rotates at a predetermined speed.A field-oriented control system can be implemented to control the direction of rotation and speed. The nominal voltage of the electrical energy storage device 135 is typically several hundred to over 1000 V. The current through the electrical machine 125 can be several hundred A.

[0025] Fig. 2 shows the inverter 130 as a motor controller with a power module 200, comprising three half-bridges 205, which can be controlled, for example, by means of a common control device 210. The motor controller 200 is configured to control the rotational behavior of the electric machine 125 and typically operates digitally using a microcomputer. Each half-bridge 205 comprises two semiconductor packages 215, 220, wherein the semiconductor packages 215, 220 are connected in series between DC voltage potentials of the energy storage device 135 as shown. A DC link capacitor 225 is preferably provided between the potentials. A center tap 230 between the semiconductor packages 215, 220 is connected to an associated phase of the electric machine 125.The upper semiconductor package 215 lies between a high potential of the energy storage device 135 and the center tap 230, and the lower semiconductor package 220 lies between the center tap 230 and a low potential of the energy storage device 135. The half-bridges 205 are thermally coupled to a cooling device 235.

[0026] Fig. 3 shows a cooling unit 300 of the cooling device 235, wherein several exemplary semiconductor packages 215 of the half-bridges 205 are shown here, which are thermally coupled to a heat sink 310 of the cooling unit 300 via a thermal compensation layer 305. The thermal compensation layer 305 is applied to the surface of the heat sink 310 in a sintering process. The cooling unit 300 is provided here for temperature control of the semiconductor packages 215, 220 of the half-bridges 205, wherein only the row of first semiconductor packages 215 is shown here. The semiconductor packages 215, 220 are to be understood as heat-conducting components of the power module 200, which are cooled by means of the cooling unit 300 and a cooling fluid that contacts the heat sink 310 at least in sections. Therefore, the inverter 130 is a fluid-cooled, in particular liquid-cooled inverter 130.The cooling fluid supply can be provided via a pump (not shown here) that supplies a cooling fluid circuit with cooling fluid.

[0027] On a side of the heat sink 310 opposite the heat-conducting components, the cooling unit 300 has a cooling structure 315 consisting of a plurality of cooling elements 320 integrally connected to the heat sink 310, here, for example, designed as so-called pin fins. The cooling elements 320 increase the contact area of ​​the cooling unit 300 with the cooling fluid (not shown here), thus improving heat dissipation.

[0028] Out of Fig. 4 shows that the plate-shaped heat sink 310 has, on a side facing the heat-conducting components, several, in this case six, spaced-apart contact surfaces 400 for at least indirectly receiving the respective semiconductor package 215, 220. The size of the contact surface 400 is adapted to the dimensions of the heat-conducting component. Each contact surface 400 has several separate, annular depressions 405 in the form of recessed grooves with continuously decreasing outer dimensions. Each depression 405 is arranged according to the plan view. Fig. 4 is essentially rectangular in shape with rounded corners. The recesses 405 can be of any cross-section. As shown in Fig. As indicated in Figure 3, the recesses 405 have a partially circular, preferably semicircular, cross-section. The recesses 405 are designed as a recessed contour in the cooling plate.

[0029] For example, in a sintering process for producing the thermal compensation layer 305, the sintering material, in particular a sintering paste, enters the recesses 405 and, after curing, creates a positive connection with the heat sink 310. This is shown in Fig. 3. This improves the connection of the heat-generating component to the heat sink 310. In particular, the positional accuracy of the heat-generating component relative to the heat sink 310 is optimized. After sintering, the heat sink 310 maintains its intended position relative to the heat-generating components, and vice versa. High positional accuracy is necessary for further, subsequent joining and / or assembly processes.

[0030] The optimal shape and geometry of the recess 405 or recesses 405 for the application can be determined through simulations, tests, and trials, taking into account the requirements of the manufacturing process. For example, one or more spiral-shaped recesses 405 or recesses 405 can be provided alternatively or additionally on the respective contact surface 400. If several recesses 405 are provided, individual, several, or all recesses 405 can be interconnected via transverse sections 410 in the form of branches or intersections, as shown in Fig. 4 is shown only as an example for the lower horizontal row of contact surfaces 400. Furthermore, the recesses 405 can be designed in a straight line, i.e. according to the illustration according to Fig. 4 horizontally, vertically and / or diagonally. Furthermore, it is not excluded that the contact surface 400 is arranged on a pedestal of the heat sink 310 (not shown here). Thus, several pedestals can be formed on the heat sink 310, each of which can accommodate a heat-generating component. For the sake of simplicity, Fig. 4 not all recesses 405 and all transverse sections 410 of the recesses 405 are provided with reference numerals. Reference symbol 100 Electric drive axle 105 Motor vehicle 110 combustion engine 115 gearboxes 120 drive wheel 125 Electric Machine 130 inverters 135 energy storage 200 power module 205 Half Bridge 210 Control device 215 Upper semiconductor package of the semiconductor bridge 220 Lower semiconductor package of the semiconductor bridge 225 DC link capacitor 230 center tap 235 Cooling device 300 cooling units 305 Thermal compensation layer 310 heat sink 315 Cooling structure 320 cooling element 400 investment area 405 Deepening 410 cross section QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 / 105028 A1

[0002]

Claims

[1] Cooling unit (300) for controlling the temperature of heat-generating components of a power module (200), comprising a heat sink (310) with a cooling structure (315), wherein a contact surface (400) for at least indirectly receiving the heat-generating component is formed on a side of the heat sink (310) facing away from the cooling structure (314), characterized by that the contact surface (400) has a recess (405) for receiving a connecting material in a connection process for connecting the heat-generating component to the heat sink (310). [2] Cooling unit (300) according to claim 1, wherein the heat sink (310) is designed as a cooling plate. [3] Cooling unit (300) according to claim 1 or 2, wherein the recess (405) is formed as a recess groove. [4] Cooling unit (300) according to one of the preceding claims, wherein the recess (405) has an annular or spiral geometry. [5] Cooling unit (300) according to one of the preceding claims, wherein at least two separate recesses (405) are provided. [6] Cooling unit (300) according to claim 5, wherein the two recesses (405) are connected to each other via a transverse section (410). [7] Cooling unit (300) according to one of the preceding claims, wherein the contact surface (400) is arranged on a pedestal of the heat sink (310). [8] Power module (200) for an inverter (130) of an electric drive axle (100), comprising a cooling unit (300) according to one of the preceding claims, wherein the cooling unit (300) is thermally coupled to heat-generating components of the power module (200). [9] Inverter (130) for an electric drive axle (100) of a motor vehicle (105), comprising a power module (200) according to claim 8. [10] Electric drive axle (100) comprising an electric machine (125) and an inverter (130) according to claim 9.

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