Transistor unit for a power converter, power converter and method for producing a power converter

Abstract

A transistor unit (112) for a power converter (108), comprising a printed circuit board (304) equipped with a plurality of power transistors (306), wherein the printed circuit board (304) has at least one electrical line (208) for electrically connecting the transistor unit (112) within the power converter (108), a heat conducting unit (114) arranged on the power transistors (306) for thermally coupling the transistor unit (112) to a cooling unit (116) of the power converter (108), and a transistor housing (302) for at least partially enclosing the printed circuit board (304), wherein the transistor housing (302) has at least one housing element (402, 404), characterized in that the transistor housing (302) has a first housing element (402) and a second housing element (404) connected to the first housing element (402), wherein the printed circuit board (304) is embedded between the first housing element (402) and the second housing element (404),wherein the first housing element (402) has at least one contact window (406, 407) for exposing the power transistors (400), wherein the first housing element (402) has an outer surface (408) facing away from the circuit board (304) and lying in a common plane (300) with cooling surfaces (410) of the power transistors (306), wherein the heat conduction unit (114) can be applied to the plane (300).

Description

[0001] The present invention relates to a transistor unit for a power converter, to a power converter and to a method for producing a power converter.

[0002] Power converters are used in many different areas and for different devices or machines, such as in connection with e-mobility, which is becoming increasingly important today.

[0003] Power modules and associated cooling structures are known from DE 11 2016 000 460 T5, DE 10 2020 214 045 A1, DE 10 2020 132 808 A1, US 2022 / 0 181 233 A1 and DE 10 2007 054 618 A1.

[0004] Against this background, the present invention provides an improved transistor unit for a power converter, an improved power converter, and an improved method for manufacturing a power converter according to the main claims. Advantageous embodiments emerge from the subclaims and the following description.

[0005] The approach presented here, for example, creates a way to maximize the available space within a power converter. This includes, in particular, creating as much space as possible for a variety of electrical components. Depending on the design, the size or dimensions of the power converter can also be advantageously reduced.

[0006] A transistor unit for a power converter is presented, wherein the transistor unit has a printed circuit board which is equipped with a plurality of power transistors, wherein the printed circuit board has at least one electrical line for electrically connecting the transistor unit within the power converter, a heat conduction unit arranged on the power transistors for thermally coupling the transistor unit to a cooling unit of the power converter and a transistor housing for enclosing the printed circuit board.

[0007] The transistor unit can be arranged, preferably vertically, in a power converter which is used, for example, for a vehicle. The vehicle can be designed as a passenger car, a commercial vehicle, or a truck. Furthermore, the vehicle can be electrically powered. The power converter can be designed, for example, as an inverter or, advantageously, as a DC-DC converter. The printed circuit board can have a plurality of power transistors. The electrical line can advantageously be shaped to electrically connect the printed circuit board to further electrical components of the power converter. For example, the electrical line can be connectable to or be connected to a further printed circuit board, which can be equipped with chokes. The printed circuit board can have the at least one electrical line or be connected to the same.The electrical leads can advantageously pass through a recess in the transistor housing. The recess can be rounded or square, for example. The recess can be formed in the at least one housing element. Alternatively, the transistor housing can be shaped to improve PCB fixation, electrical insulation, and additionally or alternatively to improve pressing force distribution. In other words, a uniform force introduction can advantageously occur when a plastic part is pressed onto the housing.

[0008] Furthermore, the transistor housing has at least one housing element. Advantageously, the transistor housing can be designed in different ways and can accordingly at least partially surround the printed circuit board. Advantageously, PCB fixation, electrical insulation, and additionally or alternatively, improved press force distribution can be enabled.

[0009] The transistor housing has a first housing element and a second housing element connected to the first housing element, wherein the printed circuit board is embedded between the first housing element and the second housing element. The first housing element further has at least one contact window for exposing the power transistors, wherein the first housing element has an outer surface facing away from the printed circuit board, which lies in a common plane with cooling surfaces of the power transistors. A heat-conducting unit for thermally coupling the transistor unit to a cooling unit of the power converter can be applied to the plane. The housing elements can be referred to, for example, as housing halves. Advantageously, the transistor housing can have a receiving section, shaped, for example, as a receiving structure, in order to hold the printed circuit board in a specific position within the transistor housing.The receiving structure can, for example, be rib-like and additionally or alternatively be arranged on the second housing element opposite the at least one contact window. This means that the at least one contact window can advantageously be arranged on the first housing element in the region of the receiving section for heat dissipation.

[0010] According to one embodiment, the circuit board can have at least one fixing opening for fixing the circuit board in a position between the housing elements, wherein the second housing element can have at least one engagement opening. The first housing element can have at least one engagement element that can be shaped to engage through the fixing opening into the engagement opening for closing the transistor housing. The at least one fixing opening can advantageously be implemented as a through-opening that is arranged, for example, in an edge region and additionally or alternatively in a corner region of the circuit board. The fixing opening can be designed, for example, as a drilled opening or as a punched opening. Advantageously, the number of fixing openings can be equal to or greater than or equal to the number of engagement openings and engagement elements.Advantageously, such engagement of engagement elements through the fixing openings into the engagement openings can prevent the circuit board from slipping within the transistor housing.

[0011] Furthermore, the first housing element can have a plurality of projections that can protrude from the common plane as spacers, wherein the intermediate layer for thermally coupling the transistor unit to a cooling unit of the power converter can be arranged between the projections. For example, the projections can have a height above the common plane that can correspond to the thickness of the intermediate layer to be arranged or arranged between the projections. In this way, a flush contact surface for contacting the cooling unit can be formed.

[0012] The transistor housing can also be designed as an overmolded part that at least partially surrounds the circuit board and the power transistors. Additionally or alternatively, the overmolded part can comprise thermally conductive fillers. This can also advantageously improve PCB fixation, electrical insulation, and additionally or alternatively, press force distribution. The overmold can, for example, comprise a thermally conductive but electrically insulating material.

[0013] According to one embodiment, the circuit board can be equipped with a snubber capacitor. The use of the snubber capacitor can advantageously improve the functionality of fast-switching power semiconductors, for example, made of silicon carbide (SiC) or gallium nitride (GaN).

[0014] The circuit board can be equipped with an integrated gate driver. The use of the gate driver can advantageously improve the functionality of fast-switching power semiconductors, for example, made of silicon carbide (SiC) or gallium nitride (GaN).

[0015] According to one embodiment, the heat-conducting unit can comprise a layer composite consisting of at least one layer, wherein the layer composite can comprise an organic material, a ceramic material, a metallic material, a metallized ceramic, and additionally or alternatively a plastic. The heat-conducting unit can advantageously comprise layers of equal thickness in the layer composite. For example, the at least one layer can comprise a plastic such as silicone and additionally or alternatively a phase-changing property. In this way, the electrical insulation of the transistor unit and thermal coupling of the circuit board to the cooling unit can be achieved particularly advantageously. Using a metallized ceramic, the mechanical and thermal connection to the transistors can be achieved via soldering, which enables very high thermal conductivity and can also facilitate tolerance compensation. According to one embodiment, the layered composite can comprise three layers, wherein a middle layer of the layered composite can comprise a different material than the outer layers. For example, the middle layer can be embodied as a ceramic layer and the outer layers as a TIM (thermal interface material).

[0016] The layered composite can also comprise three layers, with a middle layer of the layered composite having different curing characteristics than the outer layers. Advantageously, the layered composite can be applied to the plane during application to the transistor unit. The outer layers may be uncured or only partially cured. The middle layer, on the other hand, can advantageously be fully cured.

[0017] Furthermore, a power converter for a vehicle is presented, wherein the power converter comprises a transistor unit in a variant mentioned herein and a cooling unit for dissipating heat from the transistor unit, wherein the heat conduction unit of the transistor unit is arranged on the cooling unit.

[0018] The power converter can advantageously be designed as a DC-DC converter and used, for example, in a passenger car. The cooling unit can, for example, have at least one cooling channel and, additionally or alternatively, have cooling fins. Heat can advantageously be dissipated from the transistor unit, thus improving the longevity and performance of the transistor unit.

[0019] The power converter can also have a power converter housing, wherein the transistor unit can be arranged in the power converter housing. The cooling unit can be formed as a housing part of the power converter housing or integrated into the power converter housing. Advantageously, the transistor unit can be attached to or in the power converter housing such that it is surrounded by the power converter housing.

[0020] Furthermore, the power converter can have a holding unit for holding the transistor unit in the power converter, wherein the holding unit can be configured to press the transistor unit against the cooling unit. The holding unit can be designed, for example, as a spring-loaded clip into which the transistor unit can be clipped. This advantageously allows secure contact between the transistor unit and the cooling unit to be achieved.

[0021] The invention also relates to an electric axle drive for a motor vehicle comprising at least one electric motor, a transmission device, and a power converter. The electric axle drive is characterized in that the power converter is designed as described. The transmission device can have a gear for reducing the speed of the electric motor and a differential.

[0022] The invention also relates to a motor vehicle with an electric axle drive and / or a power converter. The motor vehicle is characterized in that the electric axle drive and / or the power converter are designed as described.

[0023] Furthermore, a method for producing a power converter in a previously mentioned variant is presented, wherein the method comprises a step of producing the transistor unit, wherein a circuit board of the transistor unit is populated with a plurality of power transistors, the circuit board is at least partially housed by means of the transistor housing and the heat conduction unit is arranged on the power transistors and further comprises a step of coupling the transistor unit to the cooling unit via the heat conduction unit in order to produce the power converter.

[0024] Advantageously, the power converter can be assembled or mounted using the method. For example, as part of the method for manufacturing the power converter, a joining process for the transistor unit can also be performed or controlled to produce the transistor unit.

[0025] The invention is explained in more detail by way of example with reference to the accompanying drawings. They show: Fig. 1 a schematic representation of a motor vehicle according to an embodiment; Fig. 2 a schematic representation of an embodiment of a power converter; Fig. 3 a schematic sectional view of an embodiment of a power converter; Fig. 4 is an exploded view of an embodiment of a transistor unit; Fig. 5 a schematic sectional view of an embodiment of a transistor unit; Fig. 6 a schematic sectional view of an embodiment of a transistor unit; Fig. 7 to 11 show schematic representations of individual steps of a joining process of an embodiment of a transistor unit; Fig. 12 is a schematic representation of an embodiment of an assembled transistor unit; Fig. 13 is a flowchart of an embodiment of a method for manufacturing a power converter for a vehicle; Fig. 14 is a schematic representation of an embodiment of a transistor unit; Fig. 15 is a schematic representation of an embodiment of a circuit board of a transistor unit; Fig. 16 is a schematic exploded view of an embodiment of a transistor unit; Fig. 17 is a schematic representation of an embodiment of a transistor unit; and Fig. 18 a schematic representation of an embodiment of a transistor unit.

[0026] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0027] To better understand the context of the approach, a brief overview of the topic is provided first. Power transistors are frequently used in converters, such as DC / DC converters and onboard chargers. There are various designs that differ in the type of connection pins and cooling surfaces. A fundamental goal here is to fill the available installation space as optimally as possible and to maximize power density. The size of the installation space is largely determined by other passive components, such as chokes, transformers, or capacitors. According to exemplary embodiments, the aforementioned goal of optimizing installation space utilization and power density can be advantageously achieved.

[0028] Fig. 1 shows a schematic representation of a motor vehicle 100 according to an exemplary embodiment. The motor vehicle 100 is also referred to as a vehicle, for example, and has an electric axle drive 102, which in turn has at least one electric machine 104, a transmission device 106, and a power converter 108. Overall, the motor vehicle is designed, for example, as a passenger car.

[0029] The electric machine 104 is also referred to, for example, as a drive unit or as an electric motor and is coupled, for example, to the transmission device 106. The motor vehicle 100 further comprises a power supply device 110, which is referred to, for example, as a battery. According to this exemplary embodiment, the power converter 108 is connected between the power supply device 110 and the electric machine 104.

[0030] The power converter 108 has, for example, a capacitor and a plurality of switches, for example six in number. These components are combined, for example, as electrical components. In addition to these and / or other electrical components, the power converter 108 according to this exemplary embodiment has a transistor unit 112, a heat-conducting unit 114, and a cooling unit 116. The heat-conducting unit 114 is arranged between the transistor unit 112 and the cooling unit 116 in order to thermally couple the transistor unit 112 and the cooling unit 116 to one another and electrically insulate them from one another. The cooling unit 116 is accordingly designed to dissipate heat from the transistor unit 112. The power converter 108 also has a power converter housing 118, wherein the transistor unit 112 is arranged in the power converter housing 118.According to one embodiment, the cooling unit 116 is formed as a housing part of the power converter housing 118 or integrated into the power converter housing 118.

[0031] Fig. 2 shows a schematic representation of an embodiment of a power converter 108, as already described, for example, in Fig. 1. The converter housing 118 is in Fig. 2 is shown at least partially open, so that the individual components, such as electrical components 202 of the power converter 108, are shown.

[0032] The power converter housing 118 has at least one transverse rib 200, which forms two chambers 204, 206 in the power converter housing 118. According to this exemplary embodiment, the chamber 204 is smaller than the chamber 206. Both chambers 204, 206 have dimensions such that, depending on the application or field of use, additional electronic components can be inserted into the power converter housing 118.

[0033] According to this embodiment, the transistor unit 112 is arranged on the transverse rib 200. For example, the Fig. 1 is integrated into the transverse rib 200, so that the transistor unit 112 is cooled. Electrical lines 208 protrude from the transistor unit 112 on one side surface, which lines are connected or connectable, for example, to a circuit board of the transistor unit 112 (not shown here). The electrical lines 208 are connected, for example, to a circuit board of the transistor unit 112, as is shown, for example, in Fig. 3 is shown and described. According to this embodiment, the power converter 108 has a holding unit 210 for holding the transistor unit 112 in the power converter 108, wherein the holding unit 210 is designed to protect the transistor unit 112 against the cooling unit, which in Fig. 2 is integrated into the transverse rib 200. The holding unit 210 is designed as at least one clamp that is attached to a converter base 212 of the converter 108. According to this exemplary embodiment, the transistor unit 112 is arranged vertically or perpendicularly to the converter base 212 in the converter 108.

[0034] In other words, the transistor unit 112, also referred to as a vertical power package (VPP), is arranged vertically or perpendicularly with respect to the power converter base 212 in the power converter 108. This enables 3D packaging for good volume utilization with advantageous electrical contacting and optimized thermal connection.

[0035] Fig. 3 shows a schematic sectional view of an embodiment of a power converter 108, as it is already described, for example, in at least one of the Fig. 1 to 2. Here, too, the transistor unit 112 is shown mounted in or on the power converter housing 118. As in Fig. 2, the power converter 108 has the holding unit 210, which is arranged on the power converter housing 118 and is resiliently formed to press the transistor unit 112 against the cooling unit 116. Here, the holding unit 210 is screwed to the power converter housing 118 merely by way of example.

[0036] According to this embodiment, the cooling unit 116 is integrated as at least one cooling channel in the power converter housing 118, so that, for example, a coolant can flow through the cooling unit 116. Between the cooling unit 116 and the transistor unit 112, Fig. Three heat conduction units 114 are shown, which only optionally contact a plane 300 of the transistor unit 112 over its area. The plane 300 results from an outer surface of the transistor housing 302 and at least one power transistor 306, which is arranged or mounted on a printed circuit board 304 arranged in the transistor housing 302.

[0037] As also in Fig. As also shown in FIG. 2, the transistor unit 112 has electrical leads 208, which are mechanically and electrically connected to the printed circuit board 304 of the transistor unit 112 and additionally to a printed circuit board 308 of the rectifier 108. At least one of the electrical leads 208 runs through the transistor housing 302, for example through a recess in the transistor housing 302.

[0038] According to this exemplary embodiment, a coil unit 310 is also shown, which is also electrically connected to the circuit board 308 of the power converter 108. The coil unit 310 is also in contact with the cooling unit 116, but on a side of the cooling unit 116 facing away from the heat-conducting unit 114. The coil unit 310 is designed, for example, to generate a magnetic field. Therefore, it can optionally also be referred to as a magnet unit. The coil unit 310 is arranged in a pot-like region 312 of the power converter housing 118, which is surrounded, for example, by the cooling unit 116.

[0039] For example, the heat conduction unit 114 has a thermal interface material (TIM), which includes, for example, silicone. For example, the insulation material of the heat conduction unit 114 is designed in the form of a thermal pad based, for example, on a silicone basis or a phase change material or material with a phase change function.

[0040] Fig. 4 shows an exploded view of an embodiment of a transistor unit 112, as used, for example, in at least one of the Fig. 1 to 3. Here, too, the transistor unit 112 has the circuit board 304, which is populated with a plurality of power transistors 400. The circuit board 304 has at least one electrical line 208 for electrically connecting the transistor unit 112 within the power converter or is connected thereto. Optionally, the circuit board 304 is additionally populated with a snubber capacitor and / or with an integrated gate driver.

[0041] The transistor housing 302 is designed to enclose the printed circuit board 304 and thus surround it in the assembled state. The transistor housing 302 has a first housing element 402 and a second housing element 404 connected or connectable to the first housing element 402, wherein the printed circuit board 304 is embedded between the first housing element 402 and the second housing element 404. The first housing element 402 further has at least one contact window 406 and, according to this exemplary embodiment, additionally a second contact window 407 for exposing the plurality 400 of the power transistors for heat dissipation. The first housing element 402 further has an outer surface 408 facing away from the printed circuit board, which outer surface lies in a common plane with cooling surfaces 410 of the plurality of power transistors 400.A heat conducting unit for thermally coupling the transistor unit 112 with a cooling unit of the power converter can be applied to the plane.

[0042] The circuit board 304 has at least one, according to this embodiment in particular four, fixing openings 412, 414, 416, 418, which are shaped to fix the circuit board 304 in a position between the housing elements 402, 404. The second housing element 404 has at least one engagement opening 420. The first housing element 402 has at least one engagement element 422, which is shaped to engage through the fixing opening 412 into the engagement opening 420 for closing the transistor housing 302. Since the second housing element 404 according to this embodiment has a total of four engagement openings 420, 424, 426, 428, which are positioned in the same way as the fixing openings 412, 414, 416, 418 on the circuit board 304, the first housing element 402 also has four engagement elements, of which only two engagement elements 422, 430 are shown due to the illustration perspective.

[0043] According to this embodiment, the second housing element 404 only optionally has a rib structure 432 on a side of the second housing element 404 facing the circuit board 304.

[0044] In other words, the transistor unit 112 has, for example, a 3D packaging concept for discrete power transistors 306, which are used in converter applications (DC / DC, OBC). The construction concept comprises at least one so-called topside-cooled (TSC) power transistor 306, which is soldered, for example, in a pre-assembly process onto the printed circuit board 304. The printed circuit board 304 has, for example, a snubber capacitor and / or an integrated gate driver to optimize the switching properties of fast-switching power semiconductors (SiC / GaN). The transistor unit 112 is, for example, mechanically pressured using, for example, the at least Fig. 3, the holding unit or clamp is mounted or fixed to the cooling unit, also referred to as a heat sink. The transistor unit 112 has the transistor housing 302 with the housing elements 402, 404, which are also referred to as frames and are made of plastic, for example.

[0045] Low-inductance commutation cells for power transistors, such as an integrated snubber capacitor, as well as the possibility of driver integration, are prerequisites for the use of fast-switching power semiconductors made of silicon carbide (SiC) and / or gallium nitride (GaN). Electrical insulation from housing components is achieved, for example, by plastic encapsulation.

[0046] Fig. 5 shows a schematic sectional view of an embodiment of a transistor unit 112, as used, for example, in at least one of the Fig. 1 to 4, especially in Fig. 3. In Fig. 5 also shows the heat conduction unit 114 of the power converter, which is arranged flat on the first housing element 402. The heat conduction unit 114 has a layer composite 500 consisting of at least one layer.

[0047] According to this exemplary embodiment, the layered composite 500 comprises three layers A, B, and A', which, for example, comprise an organic material, a ceramic material, and / or a plastic, such as silicone, with or without a phase-changing property. For example, the outer layers A, A' are formed from the same material or have the same curing characteristics. The middle layer B, on the other hand, has, for example, either different curing characteristics or a different material than the outer layers A, A'.

[0048] This means that the middle layer B can be fully cured, for example, during an application process to the transistor unit 112, while the outer layers A, A' can be at least partially liquid or viscous. This is done, for example, by injection molding, wherein the corresponding material is heated to a high temperature. In this case, the heat-conducting unit 114 is realized or can be realized, for example, as an organic insulator. For example, the different curing characteristics additionally bring about a mechanical coupling with the cooling unit. The layer composite 500 comprises, for example, a partially cured organic insulator or a ceramic insulator.

[0049] As a ceramic insulator, middle layer B of the layered composite 500 comprises the ceramic material, for example, as a ceramic layer. The outer layers A, A' are each designed, for example, as a thermal interface sheet (thermal interface material; TIM) made of the same material, but different from the material of the middle layer B. For example, the outer layer A is completely or partially metallic for mechanical fixation, and layer A' is metallic for cooling.

[0050] The heat conduction unit 114 therefore has, for example, at least one further insulation material for thermal connection to the heat sink.

[0051] Fig. 6 shows a schematic sectional view of an embodiment of a transistor unit, as used, for example, in at least one of the Fig. 1 to 5 and which in particular correspond to the Fig. 5. According to this exemplary embodiment, the first housing element 402 has a plurality of projections 600, 602, 604 that protrude from the common plane as spacers. The heat-conducting unit 114, as an intermediate layer for thermally coupling the transistor unit 112 to the cooling unit of the power converter, is attached or attachable between the projections 600, 602, 604. More precisely, the first housing element 402 according to this exemplary embodiment has, for example, three projections. The heat-conducting unit 114 is formed in several parts, wherein a thickness of the heat-conducting unit 114 correlates with a height or depth of the projections 600, 602, 604 emanating from the plane.

[0052] For example, the heat conduction unit 114 according to this embodiment is implemented as a filler, which provides insulation for the cooling unit. The filler is applied, for example, in a liquid phase between the projections 600, 602, 604. The heat conduction unit 113 thus comprises the insulation material as a gap filler and is arranged on a frame defined by the projections 600, 602, 604 for adjusting the layer thickness.

[0053] The Fig. 7 to 11 show individual steps of a joining process of an embodiment of a transistor unit, as described, for example, in at least one of the Fig. 1 to 6.

[0054] Fig. 7 shows a schematic representation of an embodiment of a printed circuit board 304, which, for example, corresponds to the one shown in at least one of the Fig. 3 to 6. According to this exemplary embodiment, the circuit board 304 is not yet arranged in the transistor housing. Instead, a first step of the joining process is depicted, in which individual components, such as the plurality of power transistors 306, are soldered onto the circuit board 304. For this purpose, the circuit board 304 is arranged on an auxiliary tool 700.

[0055] In Fig. 8 shows a schematic representation of the first housing element 402, on which the heat conducting element 114 can be arranged or, as shown here, is arranged.

[0056] In Fig. 9, the printed circuit board 304 is finally inserted into the first housing element 402 such that the cooling surfaces 410 of the power transistors 306 form a common plane with the outer surface 408 of the first housing element 402.

[0057] In Fig. 10 shows the transistor unit 112 fully assembled. In addition, according to the Fig. 8 and Fig. 9 the heat conduction unit 114 is arranged on the first housing element 402.

[0058] The transistor unit 112 with the heat conduction unit 114 are then, as in Fig. 11, inserted into the power converter. Here, the transistor unit 112 is pressed against the cooling unit 116 using the holding unit 210, as already shown by way of example in at least one of the Fig. 2 to 3.

[0059] Fig. 12 shows a schematic representation of an embodiment of a mounted transistor unit 112, as used, for example, in at least one of the Fig. 1 to 11. More precisely, in Fig. 12 the transistor unit 112 is shown connected or coupled to the cooling unit 116 via the heat conduction unit 114, as shown in the Fig. 2, Fig. 3 and Fig. 11 was described.

[0060] Fig. 13 shows a flowchart of an embodiment of a method 1300 for producing a power converter for a vehicle, as described, for example, at least in Fig. 1. The method 1300 includes a step 1302 of producing the transistor unit, wherein a circuit board of the transistor unit is populated with a plurality of power transistors and embedded between the first housing element and the second housing element of the transistor unit. Furthermore, the method 1300 includes a step 1304 of applying the heat conduction unit to the common plane of the transistor unit. Furthermore, the method 1300 includes a step 1306 of coupling the transistor unit to the cooling unit via the heat conduction unit to produce the power converter.

[0061] The exemplary embodiments described and shown in the figures are selected only as examples. Different exemplary embodiments can be combined with one another in their entirety or with regard to individual features. Furthermore, one exemplary embodiment can be supplemented by features of another exemplary embodiment.

[0062] Furthermore, method steps according to the invention can be repeated and carried out in a different order than that described.

[0063] Fig. 14 shows a schematic representation of an embodiment of a circuit board of a transistor unit 112, which, for example, corresponds to the one shown in at least one of the Fig. 1 to 13. According to this exemplary embodiment, the transistor housing 302 at least partially encloses the printed circuit board 304. This means that the transistor housing 302 is arranged on a side of the printed circuit board 304 facing away from the cooling unit 116. Power transistors 306, which contact the heat conduction unit 114, are arranged on the other side of the printed circuit board 304. According to this exemplary embodiment, the heat conduction unit 114 has a metallized ceramic substrate. This means that the carrier substrate comprises, for example, ceramic, to which a thin copper layer is applied for mechanical fixing and thermal connection. The power transistors 306 are soldered onto the heat conduction unit 114 as a metallized ceramic insulator. This ensures, for example, uniform force introduction and tolerance compensation.

[0064] Fig. 15 shows a schematic representation of an embodiment of a printed circuit board module 1500 of a transistor unit. More specifically, a step of a joining process for producing the printed circuit board module 1500 is shown, which is part of the transistor unit, as described, for example, in at least one of the Fig. 1 to 14. According to this embodiment, a soldering process is shown in which the power transistors arranged on the circuit board 304 are soldered to the heat conduction unit 114, thereby forming the circuit board module 1500.

[0065] Fig. 16 shows a schematic exploded view of an embodiment of a transistor unit 112 as used in at least one of the Fig. 1 to 15. According to this embodiment, it is shown that the transistor package 302 is mounted on one side of the circuit board 304 on the circuit board module 1500. The circuit board 304 is, as is also shown in Fig. 15, soldered to the heat conduction unit 114. The printed circuit board module 1500 is in turn arranged on the cooling unit 116 so that the heat conduction unit 115 contacts the cooling unit 116 in the assembled state.

[0066] Fig. 17 shows a schematic representation of an embodiment of a transistor unit 112 as used in at least one of the Fig. 1 to 16. According to this embodiment, the transistor unit 112, as described particularly in the Fig. 15 to 16, is arranged in the power converter. This means that the transistor unit 112 is shown in the assembled state and is pressed against the cooling unit 116 by the holding unit 210.

[0067] Fig. 18 shows a schematic representation of an embodiment of a transistor unit 112, which, for example, corresponds to the one shown in one of the Fig.1 to 17. According to this exemplary embodiment, the transistor housing 302 is designed as an overmolding part that surrounds the circuit board 304 and the power transistors arranged on the circuit board 304. For example, the overmolding part comprises a plastic, for example a thermoset material, which is arranged on the circuit board 304 by means of an injection molding process. According to this exemplary embodiment, the overmolding replaces the function of a plastic holder and simultaneously serves as insulation. In order to improve the thermal connection, it is, for example, a thermally optimized overmolding that contains thermally conductive fillers in order to transfer heat generated in the transistor unit 112 to the cooling unit 116.

[0068] If an embodiment comprises an “and / or” link between a first feature and a second feature, this can be read such that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature. Reference symbol 100 motor vehicles 102 electric axle drive 104 electric machine 106 Gearbox 108 power converters 110 Energy supply facility 112 Transistor unit 114 Heat conduction unit 114' heat conduction unit 116 Cooling unit 118 converter housing 200 cross ribs 202 electrical components 204 Chamber 206 Chamber 208 electrical cables 210 holding unit 212 Converter floor 300 level 302 transistor housing 304 Transistor unit circuit board 306 power transistor 308 Power converter circuit board 310 coil unit 312 pot-like area 400 majority of power transistors 402 first housing element 404 second housing element 406 contact window 407 second contact window 408 exterior area 410 cooling surface 412 Fixing opening 414 Fixing opening 416 Fixing opening 418 Fixing opening 420 access opening 422 engagement element 424 access opening 426 access opening 428 access opening 430 engagement element 432 rib structure 500 layer composite A outer layer B middle layer A' outer layer 600 lead 602 lead 604 lead 700 auxiliary tools 1300 Method for manufacturing a power converter 1302 Step of producing the transistor unit 1304 Step of applying the heat conduction unit 1306 Step of coupling the transistor unit with the cooling unit 1500 PCB module

Claims

[1] Transistor unit (112) for a power converter (108), the transistor unit (112) having the following features: - a circuit board (304) which is equipped with a plurality (400) of power transistors (306), wherein the circuit board (304) has at least one electrical line (208) for electrically connecting the transistor unit (112) within the power converter (108); - a heat conduction unit (114) arranged on the power transistors (306) for thermally coupling the transistor unit (112) to a cooling unit (116) of the power converter (108); and - a transistor housing (302) for at least partially housing the printed circuit board (304), wherein the transistor housing (302) has at least one housing element (402, 404), characterized byin that the transistor housing (302) has a first housing element (402) and a second housing element (404) connected to the first housing element (402), wherein the printed circuit board (304) is embedded between the first housing element (402) and the second housing element (404), wherein the first housing element (402) has at least one contact window (406, 407) for exposing the power transistors (400), wherein the first housing element (402) has an outer surface (408) facing away from the printed circuit board (304) and lying in a common plane (300) with cooling surfaces (410) of the power transistors (306), wherein the heat conduction unit (114) can be applied to the plane (300). [2] The transistor unit (112) according to claim 1, wherein the circuit board (302) has at least one fixing opening (412) for fixing the circuit board (304) in a position between the housing elements (402, 404), wherein the second housing element (404) has at least one engagement opening (420), wherein the first housing element (402) has at least one engagement element (422) formed to engage through the fixing opening (412) into the engagement opening (420) for closing the transistor housing (302). [3] Transistor unit (112) according to one of claims 1 to 2, wherein the first housing element (402) has a plurality of projections (600, 602, 604) which protrude from the common plane (300) as spacers, wherein the heat conducting unit (114, 114') can be attached as an intermediate layer for thermally coupling the transistor unit (112) to a cooling unit (116) of the power converter (108) between the projections (600, 602, 604). [4] Transistor unit (112) according to claim 1, wherein the transistor housing (302) is designed as an overmolding part at least partially surrounding the circuit board (304) and the power transistors (306), and / or wherein the overmolding part comprises thermally conductive fillers. [5] Transistor unit (112) according to one of the preceding claims, wherein the circuit board (304) is equipped with a snubber capacitor. [6] Transistor unit (112) according to one of the preceding claims, wherein the circuit board (304) is equipped with an integrated gate driver. [7] Transistor unit (112) according to one of the preceding claims, wherein the heat conducting unit (114) comprises a layer composite (500) of at least one layer (A, A', B), wherein the layer composite (500) comprises an organic material, a ceramic material, a metallic material, a metallized ceramic and / or a plastic. [8] Transistor unit (112) according to claim 7, wherein the layer composite (500) comprises three layers (A, A', B), wherein a middle layer (B) of the layer composite (500) comprises a different material than the outer layers (A, A'). [9] Transistor unit (112) according to one of claims 7 to 8, wherein the layer composite (500) has three layers (A, A', B), wherein a middle layer (B) of the layer composite (500) has a different curing characteristic than the outer layers (A, A'). [10] Power converter (108) for a vehicle (100), the power converter (108) having the following features: - a transistor unit (112) according to one of the preceding claims; and - a cooling unit (116) for dissipating heat from the transistor unit (112), wherein the heat conduction unit (114) of the transistor unit (112) is arranged on the cooling unit (116). [11] Power converter (112) according to claim 10, comprising a power converter housing (118), wherein the transistor unit (112) is arranged in the power converter housing (118), wherein the cooling unit (116) is formed as a housing part of the power converter housing (118) or is integrated into the power converter housing (118). [12] Power converter (108) according to one of claims 10 to 11, comprising a holding unit (210) for holding the transistor unit (112) in the power converter (108), wherein the holding unit (210) is designed to press the transistor unit (112) against the cooling unit (116). [13] Electric axle drive (102) for a motor vehicle (100) with at least one electric machine (104), a transmission device (106) and a power converter (108), characterized by that the power converter (108) is designed according to one of claims 10 to 12. [14] Motor vehicle (100) comprising an electric axle drive (102) according to claim 13 and / or a power converter (108) according to one of claims 10 to 12 and / or a transistor unit (112) according to one of claims 1 to 9. [15] A method (1300) for manufacturing a power converter (108) according to any one of claims 10 to 12, wherein the method (1300) comprises the following steps: - producing (1302) the transistor unit (112), wherein a circuit board (304) of the transistor unit (112) is populated with a plurality of power transistors (400), the circuit board (304) is at least partially housed by means of the transistor housing (302), and the heat conduction unit (114) is arranged on the power transistors (306); ; and - coupling (1306) the transistor unit (112) to the cooling unit (116) via the heat conduction unit (114) to produce the power converter (108).

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