Power electronic device, in particular for a motor vehicle, and motor vehicle

Abstract

The invention relates to a power electronic device (10) comprising a power semiconductor (12) received on a substrate, wherein the substrate has a cooling element (14) on its side facing away from the power semiconductor (12). The cooling element (14) is received in a cooling element receptacle (16) such that a cavity (18) through which a cooling liquid can flow is formed between the cooling element (14) and the cooling element receptacle (16). The cooling element receptacle (16) has a locking contour (20) which engages behind the substrate, in particular the cooling element (14), and by means of which the cooling element (20) is held in the cooling element receptacle (16).

Description

[0001] The invention relates to a power electronic device according to the preamble of independent claim 1. Furthermore, the invention relates to a motor vehicle with such a power electronic device.

[0002] Power electronic devices of the type in question can, for example, be components of pulse-controlled inverters. They contain power semiconductors that emit a comparatively large amount of heat energy during operation. For this reason, it is often necessary to cool power electronic devices of the type in question using liquid cooling.

[0003] Power electronic devices of the type in question are frequently used in motor vehicles. There, they can be used, for example, to supply electrical energy to the drive systems of electrically powered vehicles. Use in a motor vehicle entails further stringent requirements. This particularly applies to a certain degree of mechanical resilience, since power electronic devices are typically exposed to external forces acting on the power electronic device during operation of a motor vehicle, for example, forces caused by acceleration and / or deceleration of the motor vehicle.In particular, driving over obstacles, such as speed bumps in the roadway, and the resulting impacts on the motor vehicle can place greater mechanical stress on a power electronic device than is the case in stationary applications, for example as part of a machine.

[0004] In addition, there is considerable cost pressure in the series production of electrically powered vehicles, which continues to increase, particularly due to the demand for low-priced vehicles with electric drive.

[0005] In practice, power electronic devices have therefore become known in which power semiconductors are arranged on substrates that have a cooling element. With such an arrangement, a compact, mechanically resilient assembly is initially produced in which the thermal energy emitted by the power semiconductor can be conducted relatively well to the cooling element. The cooling element can in turn be accommodated in a cooling element holder in such a way that a cavity is formed between the cooling element and the cooling element holder, through which a cooling liquid can flow. By means of a cooling liquid flowing through this cavity, comparatively large amounts of thermal energy can be dissipated from the power electronic device. According to the prior art, the cooling element is fixed to the cooling element holder by means of clamping devices.The clamping devices can, for example, be frames that are attached to the cooling element holder after the cooling element or the substrate with the cooling element has been inserted into the cooling element holder. The clamping device presses the cooling element against the cooling trough. Seals can be arranged between the cooling element holder and the cooling element.

[0006] The disadvantage of such known solutions, however, is that assembly is comparatively complex. The clamping devices must be secured to the cooling element mount using screws, for example. However, such a design is relatively complex and therefore expensive. Furthermore, the clamping device requires a significant amount of installation space.

[0007] Alternatively, it is possible to bond substrates with power semiconductors mounted on them to heat sinks through which a coolant can flow. In this case, the bonding layer, such as a solder layer or a sintered layer, provides both the mechanical and thermal connection. However, due to differences in thermal expansion coefficients, this bond can be disrupted, resulting in an increase in thermal resistance and, in the worst case, in delamination of the bond and thus in the failure of the power electronic device.

[0008] The invention is therefore based on the object of providing a power electronic device and a motor vehicle with such a power electronic device, which enable high thermal and mechanical stability with a compact design and low manufacturing costs.

[0009] The problem is solved by a power electronic device and a motor vehicle having the features of the independent claims. The features of the dependent claims relate to advantageous embodiments.

[0010] The power electronic device comprises a power semiconductor mounted on a substrate. The power semiconductor can be, for example, a metal oxide semiconductor field-effect transistor (MOSFET). In particular, it can be a silicon carbide MOSFET (SiC MOSFET). These power semiconductors have proven to be particularly powerful and efficient.

[0011] The substrate is, in particular, flat. On its side facing the power semiconductor, the substrate can have a metallic layer. The metallic layer can be formed, for example, from aluminum and / or an aluminum alloy. The metallic layer can extend only partially over the side of the substrate in a defined pattern, thus forming a component of an electronic circuit of the power electronic device. In other words, the substrate can be a printed circuit board.

[0012] The power semiconductor can be arranged by means of a layer of an additive arranged between the substrate and the power semiconductor. The additive can be a sintered material. In this case, the semiconductor can be electrically connected, in particular, in an electrically conductive manner to the metallic layer of the substrate, in particular to defined regions of the metallic layer of the substrate.

[0013] The substrate has a cooling element on its side facing away from the power semiconductor. The cooling element and / or a portion of the cooling element forms, in particular, a layer of the substrate. The cooling element is made, in particular, of a metallic material, for example, aluminum and / or an aluminum alloy.

[0014] The cooling element is accommodated in a cooling element receptacle such that a cavity is formed between the cooling element and the cooling element receptacle, through which a cooling fluid can flow. The cooling element receptacle can have connections for the cooling fluid. A sealing element can be arranged between the cooling element and the cooling element receptacle to seal the cavity formed between the cooling element and the cooling element receptacle. The sealing element is, in particular, compressed between the cooling element and the cooling element receptacle, so that a reliable sealing effect is created by elastic restoring forces in the cooling element.

[0015] The cooling element receptacle can be trough- and / or tub-shaped. Such a design of the cooling element receptacle advantageously allows the cooling element receptacle, in cooperation with the cooling element, to form a cavity through which the coolant can flow. This can be achieved, in particular, by having regions of the cooling element receptacle that form the side walls of the tub-shaped cooling element receptacle circumferentially encompass the cooling element. In other words, the cooling element forms a kind of lid or cover for the tub formed by the cooling element receptacle.

[0016] The cooling element holder can be a plastic part. The cooling element holder can be manufactured using an injection molding process. A cooling element holder for a power electronic device of the type in question can be manufactured cost-effectively, particularly as a plastic injection-molded part.

[0017] This object is achieved in particular by the cooling element receptacle having a locking contour that engages behind the substrate, by which the cooling element is held in the cooling element receptacle. The locking contour can, in particular, engage behind the cooling element. This design is particularly useful when the cooling element protrudes from other layers of the substrate in the area of ​​the edge of the substrate.

[0018] The locking contour engaging behind the cooling element can be designed in the form of a locking hook. Such locking hooks, which are also referred to in practice as snap hooks, can be engaged with the substrate, in particular with the cooling element, in a particularly simple manner due to their design. Particularly in conjunction with a trough-shaped cooling element receptacle, this can be achieved simply by inserting the substrate into the trough-shaped cooling element receptacle in a movement directed perpendicular to its planar extent.

[0019] The locking hooks have surfaces oriented, in particular, obliquely to the direction in which the movement occurs relative to the cooling element receptacle. These surfaces can slide along the substrate or the cooling element, which can be associated with a temporary elastic deformation of the cooling trough. As soon as the areas of the substrate, in particular the cooling element, that are to be gripped behind by the locking hooks have passed the locking hooks, the locking hooks can grip behind the substrate, in particular the cooling element, and thus form an undercut through which the cooling element is held in the cooling element receptacle.

[0020] The substrate can have an insulating layer, which, on its side facing the power semiconductor, borders a metallic layer that is part of an electronic circuit of the power electronic device, and, with another surface side, borders the cooling element. The insulating layer can be made of a ceramic material. The ceramic material can be, for example, silicon nitride and / or aluminum nitride. Such a structure, in which an insulating layer of the substrate provides electrical insulation between the cooling element and the metallic layer that forms part of an electronic circuit, has a particularly good thermal connection between the cooling element and the power semiconductor.

[0021] The locking contour can be molded integrally with the cooling element holder. This represents a particularly cost-effective solution, especially when the cooling element holder is a plastic injection-molded part.

[0022] Alternatively and / or additionally, the locking contour can be formed by grid elements connected to the cooling element holder. The locking elements can, in particular, be grid elements made of a material different from the material of the cooling element holder.

[0023] In particular, the ability to select the material for the locking elements independently of the material for the cooling element holder enables corresponding optimization of both elements, for example with regard to mechanical properties. For example, the locking elements can be made of a metallic material, which can in particular have higher mechanical strength than a plastic from which the cooling element holder can be formed. During production of the cooling element holder, the locking elements can be connected to the cooling element holder by injection molding or overmolding. Alternatively and / or additionally, the method can provide for first producing the cooling element holder and then connecting the locking elements to the cooling element holder.For example, in this case the method may provide for the locking elements to be connected to the cooling element receptacle only in connection with the introduction of the cooling element into the cooling element receptacle.

[0024] The power electronic device can be designed such that the substrate is pressed against the locking contour by means of a pressing force in a direction at least substantially perpendicular to the plane of extension of the substrate. In particular, the power electronic device can be designed such that the cooling element is pressed against the locking contour by means of the pressing force. Such bracing of the substrate or the cooling element against the locking contour can ensure secure mechanical cohesion of the power electronic device.

[0025] The contact force can result from the elastic deformation of an elastic element arranged between the cooling element and the cooling element holder. Such an elastic element can create a defined tension between the substrate or cooling element and the cooling element holder.

[0026] The elastic element can be a sealing element for sealing the cavity formed between the cooling element and the cooling element holder. In this way, a sealing element can be used to generate the contact pressure, while at the same time, the elastic deformation of the sealing element ensures a sufficient sealing effect. This has the advantage that the sealing element can fulfill a variety of functions. Alternatively, another elastic element, such as a metallic spring element, can also be used to generate the contact pressure.

[0027] The cooling element may have projections projecting toward the cooling element receptacle. These projections may, in particular, be finger-like projections that serve to improve heat transfer from the cooling element to the cooling fluid.

[0028] The projections can be spaced apart from the cooling element receptacle such that, during assembly of the power electronic device, the substrate, in particular the cooling element, is engaged by pressing the cooling element receptacle against the projections. If, in the assembled state of the power electronic device, the projections are spaced apart from the cooling element receptacle and it is possible to press the cooling element receptacle against the projections, this, in conjunction with the locking contour and in particular an elastic element arranged between the cooling element and the cooling element receptacle, results in a simple possibility for mounting the power electronic device. The power electronic device can then be assembled in a simple manner by pressing the cooling element and the cooling element receptacle together against the resistance of the elastic element until the projections rest against the cooling element receptacle.This prevents the elastic element from being damaged, for example, by excessive compression. This would be particularly disadvantageous for a sealing element that is used as an elastic element.

[0029] During the pressing process, the substrate or cooling element can pass the locking contour. In doing so, the substrate or cooling element is moved toward the cooling element holder, particularly beyond the locking point. This ensures that the locking contour securely locks onto the substrate or cooling element, despite any manufacturing tolerances.

[0030] After the power electronic device is relieved of the pressing force, the substrate or cooling element can move away from the cooling element holder due to the pressure force generated by the elastic deformation of the elastic element until the substrate, in particular the cooling element, rests against the locking contour. The assembly process is thus reduced in a process-reliable manner by pressing the substrate or cooling element and the cooling element holder together, with the projections limiting the distance traveled during the pressing process.

[0031] A further advantage of the distance between the projections and the cooling element holder is that the coolant also flows around the projections and the cooling element holder. This can further improve heat transfer.

[0032] The power electronics device can be a pulse-controlled inverter for operating an electric drive or a component of such a pulse-controlled inverter. The component of the pulse-controlled inverter is, in particular, a power module containing the power switches of the pulse-controlled inverter. This can be a half-bridge power module. In particular, a power electronics device designed as a power module can be connected to control electronics for controlling the power switches of the pulse-controlled inverter by means of a plug-in contact or a plurality of plug-in contacts. The control electronics can comprise a printed circuit board via which the control electronics is electrically contacted by means of the plug-in contacts. The printed circuit board is arranged, in particular, parallel to the substrate.

[0033] The motor vehicle has an electric drive and a power electronic device of the type described. In particular, the motor vehicle can have a pulse-controlled inverter as described above. The power electronic device serves to supply the electric drive with electrical energy.

[0034] Power electronic devices of the type in question can be used particularly advantageously in a motor vehicle to supply its drive system with electrical energy. Due to the achievable compact design and simultaneous suitability for economical series production, the described power electronic devices and the described method for their production are predestined to meet the high requirements of the automotive sector in this regard.

[0035] Further practical embodiments of the invention are described below in conjunction with the drawings. They show: Fig. 1 a schematic sectional view of an exemplary power electronic device, Fig. 2 a schematic sectional view of another exemplary power electronic device.

[0036] The Fig. 1 and Fig. The power electronic devices 10 schematically illustrated in Figure 2 each have power semiconductors 12. As in the example shown, each of the power electronic devices 10 can have a plurality of power semiconductors 12. The power semiconductors 12 of the exemplary power electronic devices 10 are mounted on a substrate. The substrate has a cooling element 14 on its side facing away from the power semiconductor 12. As in the example shown, the substrate and a region of the cooling element 14, which forms a layer of the substrate, can be flat.

[0037] The cooling element 14 is accommodated in a cooling element receptacle 16 such that a cavity 18 is formed between the cooling element receptacle 16 and the cooling element 14. A cooling fluid can flow through the cavity 18.

[0038] The cooling element holder 18 has a locking contour 20. The locking contour 20 can be arranged as shown in the Fig. 1 and Fig. 2, the locking contour 20 can engage behind the substrate; in this case, the locking contour 20 can engage behind the cooling element 14, in particular as in the examples shown. As in the example shown, the cooling element 14 can extend flat over a larger area than other layers of the substrate, so that a surface region 22 of the cooling element 14 facing away from the cooling element receptacle 16 is accessible. This can be used, for example, to engage with a tool during assembly of the power electronic device 10, in particular to press the cooling element receptacle 16 and the cooling element 14 together. The locking contour 20 holds the cooling element 14 in the cooling element receptacle 16. The cooling element receptacle 16 can be trough-shaped, as in the example shown.

[0039] The substrate may have an insulating layer 24, as in the example shown. The insulating layer 24 may have a metallic layer 26 on its surface facing the power semiconductor 12, as in the examples shown. The metallic layer 26 may be part of an electronic circuit of the power electronic device 10.

[0040] The power semiconductors 12 can be connected to the substrate by means of a layer 28 made of an additive, as in the example shown. In this case, the power semiconductors 12 can be electrically connected, in particular, to the metallic layer 26 of the substrate, as in the examples shown.

[0041] The power semiconductors can be encapsulated, as in the examples shown, using a potting compound 30 that fills a space above the substrate. The metallic layer 26 can be contacted by means of electrical contacts 32. The electrical contacts 32 can, in particular, extend away from the substrate at a right angle to the plane of extension of the substrate, as in the example shown. The electrical contacts 32 can, in particular, connect the metallic layer 26 of the substrate to a printed circuit board 34. As in the examples shown, the printed circuit board can be arranged with its plane of extension perpendicular to the plane of extension of the substrate.

[0042] As in the examples shown, the power electronic devices 10 can be designed such that the cooling element 14 is pressed against the locking contour 20 by means of a pressing force in a direction perpendicular to the plane of extension of the substrate. The pressing force can result from the elastic deformation of an elastic element arranged between the cooling element 14 and the cooling element receptacle 16. In the example shown, the elastic element can be a sealing element 36. The sealing element 36 can serve to seal the cavity 18 formed between the cooling element 14 and the cooling element receptacle 16.

[0043] A power electronic device 10 of the type in question can be used in accordance with the Fig. 1 and Fig. 2 can be designed in such a way that the cooling element 14 can be connected to the cooling element receptacle 16 by pressing the cooling element receptacle 16 and the cooling element 14 together.

[0044] The power electronic device 10 can be designed, as in the examples shown, such that the cooling element 14 is spaced apart from the cooling element receptacle 16. As in the example shown, this can mean, in particular, that projections 38 of the cooling element 14, which protrude from the cooling element 14 toward the cooling element receptacle 16, are spaced apart from the cooling element receptacle 16.

[0045] If the assembly of such a power electronic device 10 as described in the Fig. 1 and Fig. 2, by pressing together the cooling element 14 and the cooling element receptacle 16, the cooling element 14 can approach the cooling element receptacle 16 under an elastic deformation of the sealing element 36 until the projections 38 come into contact with the cooling element receptacle 16.

[0046] The areas of the substrate to be gripped behind, in the examples shown, areas of the cooling element 14, pass the locking contour 20 in such a way that, along the direction X, along which the pressing takes place, a distance initially arises between the locking contour 20 and the area of ​​the substrate to be gripped behind. This ensures that the substrate can also be securely gripped behind during assembly. The distance corresponds to the Fig. 1 and Fig. 2 between the cooling elements 14 or their projections 38 and the cooling element receptacle 16, which occurs when the power electronic device 10 is relieved of load after pressing and the cooling element 14 and the cooling element receptacle 16 assume their final position relative to each other. In this final position, the sealing elements 36 shown continue to be elastically deformed.

[0047] The sealing elements 36 can, for example, be inserted sealing elements 36, such as sealing rings with a circular cross-section in the undeformed state in the example shown. Alternatively and / or additionally, the sealing element 36 can also be a sealing element 36 molded onto the cooling element receptacle 16. Such a sealing element 36 can, for example, be produced together with the cooling element receptacle 16 using two-component injection molding.

[0048] The locking contours 20 can, as shown in Fig. 1, be formed integrally with the cooling element holder 16. Alternatively, the locking contour 20 can be formed as in the Fig. 2, it can be formed by a locking element 40 connected to the cooling element holder 16.

[0049] The features of the invention disclosed in the present description, the drawings, and the claims may be essential, both individually and in any combination, for the realization of the invention in its various embodiments. The invention may be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art. List of reference symbols 10 power electronic devices 12 power semiconductors 14 Cooling element 16 Cooling element holder 18 cavity 20 locking contour 22 Surface area 24 Insulating layer 26 metallic layer 28 layer of additive 30 Casting compound 32 electrical contacts 34 circuit board 36 Sealing element 38 projections 40 locking element X direction

Claims

[1] Power electronic device (10) with a power semiconductor (12) which is accommodated on a substrate, wherein the substrate has a cooling element (14) on its side facing away from the power semiconductor (12), wherein the cooling element (14) is accommodated in a cooling element receptacle (16) such that a cavity (18) is formed between the cooling element (14) and the cooling element receptacle (16), through which a cooling liquid can flow, characterized by , that the cooling element receptacle (16) has a locking contour (20) which engages behind the substrate, in particular the cooling element (14), and by means of which the cooling element (20) is held in the cooling element receptacle (16). [2] Power electronic device (10) according to claim 1, characterized bythat the substrate has an insulating layer (24) which, with its surface side facing the power semiconductor (12), adjoins a metallic layer (26) which is a component of an electronic circuit of the power electronic device (10), and with another surface side adjoins the cooling element (14). [3] Power electronic device (10) according to claim 1 or 2, characterized by that the locking contour (20) is formed integrally with the cooling element holder (16) on the cooling element holder (16). [4] Power electronic device (10) according to claim 1 or 2, characterized by that the locking contour (20) is formed by a locking element (40) connected to the cooling element holder (16) and made of a material different from the material of the cooling element holder (16). [5] Power electronic device (10) according to one of the preceding claims, characterized bythat the power electronic device (10) is designed such that the substrate, in particular the cooling element (14), is pressed against the locking contour (20) by means of a pressing force in a direction at least substantially perpendicular to the plane of extension of the substrate. [6] Power electronic device (10) according to one of the preceding claims, characterized by that the pressure force results from the elastic deformation of an elastic element arranged between the cooling element (14) and the cooling element holder (16). [7] Power electronic device (10) according to one of the preceding claims, characterized by that the elastic element is a sealing element (36) for sealing the cavity (18) formed between the cooling element (14) and the cooling element receptacle (16). [8] Power electronic device (10), characterized byin that the cooling element (14) has projections (38) projecting towards the cooling element receptacle (16) and spaced from the cooling element receptacle (16) in such a way that, during assembly of the power electronic device (10), the engagement behind the substrate, in particular the cooling element (14), can be brought about by pressing the cooling element receptacle (16) against the projections (38). [9] Power electronic device (10) according to one of the preceding claims, characterized by that the power electronic device (10) is a pulse-controlled inverter for operating an electric drive or a component of such a pulse-controlled inverter. [10] Motor vehicle with an electric drive and a power electronic device (10) according to one of the preceding claims for supplying the electric drive with electrical energy.

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