comprising a power semiconductor module and powertrain for a vehicle comprising such a power semiconductor module

Abstract

Power semiconductor module (10), comprising a substrate (12) on which an electrical circuit (14) is arranged, wherein the electrical circuit (14) comprises at least one power semiconductor device (16a, 16b), and wherein the electrical circuit (14) is at least partially enclosed with an enclosure material (26) which is in direct contact with at least a part of the circuit (14), wherein the substrate (12) has a first region (42) with a first thickness D1 and a second region (44) with a second thickness D2, wherein the second thickness D2 is less than the first thickness D1, and wherein at least one power semiconductor device (16a, 16b) is positioned on the second region (44), the enclosure material (26) comprises an external cooling structure (28) for dissipating heat from the enclosure material (26), and the external cooling structure (28) has cooling fins (30).

Description

The present invention relates to a power semiconductor module. In particular, the present invention relates to a power semiconductor module with an at least partially enclosed circuit featuring improved cooling. The present invention further relates to a powertrain for an electrically powered vehicle and to an electrically powered vehicle itself. The development of control units for electrically powered vehicles is well-established. Printed circuit boards or control units, for example in the automotive sector for applications with a 48V inverter, have traditionally been manufactured with a base plate and housing. Higher-level integrated applications utilize so-called "embedded" technology. Furthermore, solutions already exist using an enclosure material, in which electrical assemblies, either as a whole or as a subgroup of a circuit, are partially or completely enclosed with an enclosure material. EP 2 695 499 B1, for example, describes a device comprising a substrate for supporting an electrical circuit, a housing for enclosing the substrate, and a potting compound contained within the housing that at least partially surrounds the substrate. The potting compound can adhere to the housing. Furthermore, the device has a wall from which the potting compound can detach. However, such solutions can be further improved, particularly with regard to cost-effective and simple manufacturing and / or the provision of improved performance data. US patent 2006 / 0012034A1 describes a motor control system in which electronic components are arranged on a printed circuit board, and the printed circuit board along with the electronic components are overmolded, and a fluid-carrying cooling channel is formed in the overmolding. DE 10 2015 115 271 A1 describes an electronic assembly with interference suppression capacitors, wherein the circuit board is arranged on a metallic heat sink. From DE 10 2008 053 ​​489 A1 a carrier body for a semiconductor device is known, wherein semiconductor chips are arranged on the carrier body and are surrounded by a capsule mass. A power module is described in US 2004 / 0 070 946 A1, which has a printed circuit board with overmolded electronic components. US 2020 / 0343150A1 describes a method for manufacturing a power module wherein a chip is positioned between an upper carrier and a lower carrier. The object of the present invention is to provide a solution with which a power semiconductor module can be improved with regard to its performance data. The present invention is achieved by a power semiconductor module having the features of claim 1. The problem is further solved by a drive train having the features of claim 8 and by an electrically powered vehicle having the features of claim 9. Preferred embodiments of the invention are described in the dependent claims, in the description, or in the figures, wherein further features described or shown in the dependent claims, in the description, or in the figures may, individually or in any combination, constitute an object of the invention unless the context clearly indicates otherwise. The present invention relates to a power semiconductor module comprising a substrate on which an electrical circuit is arranged, wherein the electrical circuit comprises at least one power semiconductor device, and wherein the electrical circuit is at least partially enclosed with an enclosure material which is in direct contact with at least a part of the circuit, wherein the substrate has a first region with a first thickness D1 and a second region with a second thickness D2, wherein the second thickness D2 is less than the first thickness D1, and wherein at least one power semiconductor device is positioned on the second region, the enclosure material comprises an external cooling structure for dissipating heat from the enclosure material, and the external cooling structure has cooling fins. Such a module can offer significant advantages over state-of-the-art solutions, particularly in terms of simplified manufacturing and improved performance data. This document describes a power semiconductor module. A power semiconductor module can be understood to be, in particular, one that, according to a definition known to those skilled in the art, comprises at least one semiconductor device designed for controlling and / or switching high electrical currents and voltages. High currents and voltages are understood to mean, in particular, currents exceeding 1 ampere and voltages exceeding approximately 24 volts. Specifically, the power semiconductor module described here can be used to control an electric motor, as will be described in greater detail later. The power semiconductor module has a substrate on which an electrical circuit is arranged. For this purpose, the substrate has, in particular, an electrically insulating base structure on which the circuit is positioned and connected accordingly. For example, the substrate is a printed circuit board (PCB), a type of circuit board known per se. The substrate may, for example, have electrical conductors and / or be provided with metallizations. The specific positioning and wiring of the electrical circuit can be implemented in a manner readily known to a specialist, taking into account the desired application. The electrical circuit comprises at least one power semiconductor component, preferably a plurality of power semiconductor components, which in turn are selected according to the desired application. For example, an inverter can be designed, for which the component(s) may include power transistors, such as bipolar transistors, MOSFETs and / or IGBTs. In the power semiconductor module described here, the electrical circuit is at least partially, or for example completely, enclosed by a housing material. For example, the housing material can be a potting compound or another material that is applied directly to at least part of the electrical circuit and can, for example, harden there. Thus, in the sense of the present invention, "enclosure" means in particular that the housing material is in direct contact with at least part of the circuit. For example, the housing material can be in direct contact with power semiconductor components or with bond wires used to connect the components. The enclosure material serves to protect the electrical circuit from external influences, such as moisture, dust, or mechanical influences. In particular, by providing the enclosure material, the use of an additional housing surrounding the electrical circuit can be avoided, so that the power semiconductor module can be designed without a housing. Furthermore, the housing material provides mechanical stability to the power semiconductor module, so that the provision of base plates or similar components that serve to stabilize the module can be dispensed with, or such components can at least be reduced or made lighter and / or with less material. Regarding the substrate, it is further provided that it has a first region with a first thickness D1 and a second region with a second thickness D2, wherein the second thickness D2 is less than the first thickness D1, and wherein at least one power semiconductor element is positioned on the second region. In particular, the provision of such a substrate or such a positioning of the power semiconductor device can offer significant advantages compared to prior art solutions. Because of the substrate's thickness structure, the power semiconductor components can be arranged in such a way that heat dissipation is particularly effective. Since at least one power semiconductor component is located in the second, and thus comparatively thinner, area, heat can be dissipated especially effectively across the substrate, or along its thickness. In this regard, it has been shown that, compared to the substrate material, other materials may exhibit improved thermal conductivity, or that the substrate material may, in some cases, impede heat dissipation. However, this disadvantage can be prevented or at least reduced according to the invention. With regard to performance data, the circuit can therefore be designed to produce a larger amount of heat under operating conditions. This heat can nevertheless be effectively dissipated by the improved heat dissipation concept of the present invention. In particular, improved cooling can also have a positive impact on service life, thus extending the overall lifespan. Furthermore, it can reduce susceptibility to malfunctions, which can lead to increased reliability. This results in improved robustness against thermal, mechanical, and chemical disturbances, despite the elimination of industry-standard housing solutions. Consequently, the robustness of the assembly and interconnection technology is enhanced throughout the entire service life. The housing material of the power semiconductor module, as described, allows for cost reduction while adhering to given requirements and limitations regarding thermal management. High component complexity and significant spatial constraints on the electronic assembly components can be avoided, as these can be gas-tight and protected, for example, by targeted protection of the component solder joints. Components known from the prior art and required there, such as aluminum base plates for mechanical stabilization, thermal interface material, housing, etc., can easily be omitted. As already mentioned, this results in a reduction of overall costs and weight, and simplifies manufacturing. Furthermore, by adjusting the second thickness D2, the heat dissipation can be adapted to the power semiconductor component, ensuring suitable heat dissipation and thus particularly effective thermal management. According to the invention, the enclosure material has an external cooling structure for dissipating heat from the enclosure material. An external cooling structure is, in particular, a structure that is present on the surface of the enclosure material. This is because the housing material is permitted not only to provide mechanical stability and protect the electrical circuit from external influences, but also to be part of the assembly's heat dissipation concept. This allows for particularly effective heat dissipation from the electrical circuit without the need for complex additional components. As a result, the performance and manufacturability of the power semiconductor module can be further improved. Furthermore, this allows for a reduction in the number of individual components required for assembly, thus simplifying manufacturing. It also makes it possible to save costs and weight. The latter can be particularly advantageous in mobile applications, such as the use of the power semiconductor module in an electric vehicle. According to the invention, the outer cooling structure has cooling fins. In this embodiment, structures can be provided, particularly on the surface, which increase the surface area compared to a smooth surface. For example, the cooling fins can be formed in a manner known per se by creating a plurality of adjacent fins, also known as a comb structure. Thus, in this embodiment, passive cooling can be generated, by which heat can be dissipated into the atmosphere surrounding the cooling structure. For example, in the specific application, air can be present as a cooling atmosphere adjacent to the cooling fins. An advantage of passive cooling can be, in particular, that cooling or heat dissipation can occur directly through the design of the surface structure of the enclosure material without any further active elements, so that further active components can be dispensed with. Preferably, the substrate can further comprise a third region with a third thickness D3, wherein the third thickness D3 is less than the second thickness D2, and wherein at least one power semiconductor element is positioned on the third region. In this embodiment, the substrate can thus have at least two regions on which power semiconductor devices with improved heat dissipation can be positioned. This makes it possible to adapt the heat dissipation of different power semiconductor devices accordingly and thus to consistently provide the aforementioned advantages particularly effectively, even with a plurality of different power semiconductor devices. It is further preferred that a second area be arranged between two first areas. In this embodiment, a kind of cavity can be created for the power semiconductor device, in which the latter can be positioned. In addition to improved heat dissipation, this allows the power semiconductor device positioned in the second area or cavity to also receive mechanical protection from the substrate, which can also have a positive effect on its durability and resistance to damage. It may further be preferred that the first thickness D1 is the greatest thickness of the substrate and that all first regions are free of a power semiconductor device. In this embodiment, improved heat dissipation can be provided for all power semiconductor elements, which makes the advantages of potentially improved performance data and improved manufacturability particularly effective. However, within the scope of the present invention, it is not excluded that one or more power semiconductor elements may also be present in the first region. Regarding the enclosure material, it may be provided that it includes an internal cooling structure for dissipating heat from the enclosure material. An internal cooling structure is understood to be a structure located inside the enclosure material, and thus, for example, may be completely or at least two-dimensionally surrounded by the enclosure material. Additionally, the internal cooling structure may be part of a cooling channel for conveying a cooling medium. In particular, the cooling structure may be part of or define a coolant channel, wherein the coolant channel is, in particular, a channel for conveying liquid coolant. This design allows for particularly effective cooling, as very effective cooling is possible especially through the use of liquid coolant. It can be particularly advantageous that the housing material itself defines the cooling channel, as this allows for particularly simple manufacturing combined with effective cooling. This enables direct mounting onto a liquid-cooled radiator or a section thereof with open cooling channels. Any intermediate supports, such as aluminum plates, can be omitted, which in turn saves costs and weight and simplifies manufacturing. It may also be preferable for the enclosure material to contain a thermally conductive filler. The filler can improve the thermal conductivity, particularly compared to a pure enclosure material, which in turn can lead to improved heat dissipation and thus improved cooling of the circuit. For the purposes of this invention, a thermally conductive filler is understood to be one that exhibits a higher thermal conductivity than the housing material itself. The specific selection of the filler can be made based on the intended application, the desired thermal and mechanical properties, and any cost constraints. Regarding the enclosure material, it may be preferable for it to be a thermoset material. Thermoset materials offer the advantage of a particularly favorable combination of processability and available properties as enclosure materials. Regarding processability, it is advantageous that thermosets can usually be used as potting compounds before they reach their thermosetting state. This makes them well-suited for at least partially enclosing the electrical circuit. Furthermore, this allows for the integration of highly defined and reproducible cooling structures, both internal and external. This can be achieved, for example, by casting in placeholders, such as heat pipes, for internal structures, which define the shape of the cooling element. The external structures can be created using molds or, likewise, using corresponding placeholders. With regard to the achievable properties, thermosets offer the advantage of high stability and hardness and usually very good media resistance, so that a high level of protection of the electrical circuit can be combined with the trouble-free use for conveying a coolant. With reference to further advantages and technical features of the power semiconductor module, reference is made to the description of the powertrain, the vehicle, the figures, and the description of the figures, and vice versa. Furthermore, a drive train for an electrically powered vehicle, such as in particular an electrically powered motor vehicle, is described, comprising a voltage source, a power semiconductor module and an electric motor, wherein the power semiconductor module is designed as described. Such a powertrain can be particularly advantageous for an electrically powered or driveable vehicle, such as a pure electric vehicle, a hybrid vehicle or a mild hybrid vehicle, which only provides recuperated energy. The voltage source, in particular a battery, can be a battery known per se, such as in particular a lithium-ion battery, and provide a voltage in the range of approximately 48 V, which is applied to the power semiconductor module, in particular an inverter. Accordingly, the electrical circuit can form an inverter. It is particularly preferred that such an inverter is designed to convert an input voltage of at least 30 V, for example 48 V, into an alternating voltage. In this embodiment, the circuit or power semiconductor module is preferably suitable for use in the drivetrain of an electrically powered vehicle. Thus, the described invention can, in particular, replace prior art solutions where previously different solutions, such as housing-based solutions, have been implemented. Therefore, the advantages of the present invention can be especially effective in such an inverter. Furthermore, thermal management is of great importance, especially for inverters, so improved cooling solutions are significant, particularly for inverters, for example in the powertrain of an electrically powered vehicle. The inverter can invert the current, for example into alternating current, and thereby power the electric motor, such as a three-phase electric motor. This, in turn, can be used to drive the vehicle. Thus, the power semiconductor module can be described as a control unit for the electric motor. Such a structure is known per se, but the use of the power semiconductor module according to the invention offers the advantages described above with regard to improved manufacturability and improved performance data or improved thermal management of the power semiconductor. With reference to further advantages and technical features of the powertrain, reference is made to the description of the power semiconductor module, the vehicle, the figures, and the description of the figures, and vice versa. Furthermore, an electrically powered vehicle is described, wherein the electrically powered vehicle comprises at least one power semiconductor module and a drive train, as described in detail. The vehicle can be, for example, a fully electric vehicle, a hybrid vehicle, or a mild hybrid vehicle. For instance, the vehicle could be a motor vehicle, such as a car, a truck, or a bus. Furthermore, the vehicle could also be any other land vehicle, watercraft, especially a ship, or aircraft, such as an airplane or a spacecraft. The vehicle can in particular exhibit the aforementioned advantages, namely that the vehicle, through the design of the power semiconductor module or the drive train comprising the semiconductor module, offers advantages with regard to thermal management, performance data and manufacturing. With reference to further advantages and technical features of the vehicle, reference is made to the description of the power semiconductor module, the drive train, the figures, and the description of the figures, and vice versa. The invention is further explained below with reference to the figures, whereby one or more features of the figures, individually or in combination, may constitute a feature of the invention. Furthermore, the figures are to be considered merely exemplary and in no way limiting. Fig. 1 schematically shows a sectional view through a first embodiment of a power semiconductor module according to the invention; Fig. 2 schematically shows a sectional view through a further embodiment of a power semiconductor module according to the invention; Fig. 3 schematically shows a sectional view through a further embodiment of a power semiconductor module according to the invention; and Fig. 4 schematically shows a powertrain of a motor vehicle with a power semiconductor module according to an embodiment of the invention. Figure 1 shows a sectional view through a power semiconductor module 10 according to one embodiment of the invention. The power semiconductor module 10 is particularly suitable for use in a drive train 36 of an electrically powered vehicle. In particular, the power semiconductor module 10 can form an inverter and thus control an electric motor 40 of the drive train 36. The power semiconductor module 10 comprises a substrate 12 on which an electrical circuit 14 is arranged, wherein the electrical circuit 14 has two power semiconductor components 16a, 16b. The substrate 12 can, for example, be a conventional printed circuit board formed from an electrically insulating matrix material 18, in or on which electrical conductors 20 are arranged. A conductor frame 22, for example made of copper with a cross-section of 10 x 5 mm, can be surface-mounted on the substrate 12, for example by soldering or press-fitting, to serve as a busbar. The conductor frame 22 can be used to control an electric motor 40 and can also carry a power semiconductor component. Furthermore, the conductor frame 22 is preferably also part of the electrical circuit 14. Furthermore, the power semiconductor components 16a, 16b are arranged on metallizations or the conductor tracks 20. The power semiconductor components 16a, 16b can be applied by soldering and / or sintering and subsequently electrically contacted by wire bonding using bond wires 24a, 24b. Following the foregoing, it may be provided that the electrical circuit 14 forms an inverter, wherein it may be particularly preferred that the inverter is configured to convert an input voltage of at least 30 V, for example of 48 V, into an alternating voltage in order to be able to drive an electric motor 40. In a subsequent process, the entire or partial sections of the electrical circuit 14 are hermetically coated or enclosed with a coating of an encapsulation material 26, such as a thermoset. This enables increased mechanical stability as well as improved resistance to external media, such as harsh environments like those found in an automatic transmission. Examples include contact with transmission oil or protection against corrosion. Fig. 1 shows that the substrate 12 has a first region 42 with a first thickness D1 and a second region 44 with a second thickness D2, wherein the second thickness D2 is less than the first thickness D1, and wherein a power semiconductor element 16a is positioned on the second region 44. Furthermore, it is additionally provided that the substrate 12 also has a third region 46 with a third thickness D3, wherein the third thickness D3 is less than the second thickness D2, and wherein at least one power semiconductor element 16b is positioned on the third region 46. This enables particularly effective heat dissipation from the power semiconductor elements 16a, 16b. This is because the power semiconductor elements 16a, 16b are arranged in regions with a comparatively small thickness, so that the substrate 12 does not impede heat dissipation, or only to a comparatively small extent. Furthermore, Fig. 1 shows that the second region 44 and also the third region 46 are arranged between two first regions 42. This allows the power semiconductor components 16a, 16b to be mechanically protected by the substrate 12, which combines good heat dissipation with high mechanical stability. To improve heat dissipation from the enclosure material 26 and thus also from the circuit 14, and therefore basically to improve thermal management, it may be provided that the enclosure material 26 contains a thermally conductive filler. The figures further show that the enclosure material 26 comprises at least one inner and one outer cooling structure 28 for dissipating heat from the enclosure material 26. Different embodiments of the cooling structure 28 are shown in Figures 1, 2 to 3, where identical or comparable components are designated with the same reference numerals. Therefore, the different embodiments will be discussed in detail below. Figure 1 shows an external cooling structure 28 comprising cooling fins 30. The cooling fins 30 are arranged approximately in a comb-like structure and increase the surface area of ​​the housing material 26, thus ensuring good contact with the atmosphere surrounding the cooling fins 30. This allows for improved heat dissipation from the housing material 26 and consequently from the circuit 14. Figure 2 shows that an internal cooling structure 28 is part of a cooling channel 32 for conveying a cooling medium. In particular, the cooling channel 32 can be designed to convey a liquid cooling medium and can be bounded on one side by the housing material 26 and on the other side by an external cooler 34, wherein the cooling channel 32 is bounded between the cooler 34 and the housing material 26 by seals 35. The cooler 34 can, in particular, be made of a metal. In this configuration, the cooling channel 32 can thus be part of a cooling circuit that conveys a cooling medium through the cooling channel. Furthermore, it can be provided that the housing material 26 also has cooling fins 30, which, together with the cooler 34, can form the cooling channels. Figure 3 shows an embodiment in which a cooling channel 32 is also present, but this is an internal cooling structure 28. Thus, in the embodiment according to Figure 3, the cooling channel 32 is provided within the housing material 26, so that an external cooler 34 can be dispensed with. Nevertheless, the cooling channel 32 can, as described above, be part of a cooling circuit. Figure 4 shows the integration of the power semiconductor module 10 into the powertrain 36 of a motor vehicle. Specifically, it shows that a battery, such as a lithium-ion battery capable of providing a voltage of approximately 48 V, is connected to the power semiconductor module 10. The power semiconductor module 10 can, in particular, function as an inverter and convert the DC voltage supplied by the battery, which serves as the voltage source 38, into AC voltage. This AC voltage can then power an electric motor 40, such as a three-phase motor.

Claims

Power semiconductor module (10), comprising a substrate (12) on which an electrical circuit (14) is arranged, wherein the electrical circuit (14) comprises at least one power semiconductor device (16a, 16b), and wherein the electrical circuit (14) is at least partially enclosed with an enclosure material (26) which is in direct contact with at least a part of the circuit (14), wherein the substrate (12) has a first region (42) with a first thickness D1 and a second region (44) with a second thickness D2, wherein the second thickness D2 is less than the first thickness D1, and wherein at least one power semiconductor device (16a, 16b) is positioned on the second region (44), the enclosure material (26) comprises an external cooling structure (28) for dissipating heat from the enclosure material (26), and the external cooling structure (28) has cooling fins (30). Power semiconductor module (10) according to claim 1, characterized in that the substrate (12) further comprises a third region (46) with a third thickness D3, wherein the third thickness D3 is less than the second thickness D2, and wherein at least one power semiconductor device (16a, 16b) is positioned on the third region (46). Power semiconductor module (10) according to one of claims 1 or 2, characterized in that a second region (44) is arranged between two first regions (42). Power semiconductor module (10) according to one of claims 1 to 3, characterized in that the first thickness D1 is the greatest thickness of the substrate (12) and that all first regions (42) are free of a power semiconductor device (16a, 16b). Power semiconductor module (10) according to one of claims 1 to 4, characterized in that the housing material (26) comprises an internal cooling structure (28) for dissipating heat from the housing material (26). Power semiconductor module (10) according to claim 5, characterized in that the internal cooling structure (28) is part of a cooling channel (32) for guiding a cooling medium. Power semiconductor module (10) according to one of claims 1 to 6, characterized in that the housing material (26) comprises a thermally conductive filler. Powertrain (36) for an electrically powered vehicle, comprising a voltage source (38), a power semiconductor module (10) and an electric motor (40), wherein the power semiconductor module (10) is configured according to one of claims 1 to 7. Electrically powered vehicle, wherein the electrically powered vehicle comprises at least one of a power semiconductor module (10) according to any one of claims 1 to 7 and a drive train (36) according to claim 8.

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