Power semiconductor arrangement and inverter bridge with power semiconductor arrangement

Abstract

Power semiconductor arrangement (10, 20, 30) comprising at least one first printed circuit board (14), at least one second printed circuit board (16) and at least one power semiconductor (12), wherein the at least one power semiconductor (12) is arranged partially or completely within the at least one second printed circuit board (16), wherein the at least one first printed circuit board (14) is electrically connected to the at least one second printed circuit board (16) and wherein the at least one power semiconductor (12) is electrically connected to the at least one second printed circuit board (16), and wherein the at least one first printed circuit board (14) is mechanically connected to the at least one second printed circuit board (16) via a conductive short-distance connection (18), wherein the at least one power semiconductor (12) is arranged between an upper copper layer (42) and a lower copper layer (36) of the at least one second printed circuit board (16),wherein the upper copper layer (42) has conductor tracks (42a, 42b) which provide an electrical connection between the at least one power semiconductor (12) and the short-distance connection (18), wherein a further copper layer (50) is arranged below the lower copper layer (36), wherein the further copper layer (50) has at least the same area as the lower copper layer (36), is electrically insulated from the lower copper layer (36) and forms a cooling surface for the at least one second circuit board (16).

Description

Technical area

[0001] This application relates to the technical field of assembly and connection technology for power electronics, in particular for power converters with power semiconductors that convert electrical power in the range of a few kilowatts to a few hundred kilowatts at a voltage of a few hundred volts between direct current and alternating current. Examples of power semiconductors in power converters are semiconductor switches in DC / DC converters, DC / AC converters, or AC / AC converters. Such power converters can have power stages of various topologies, e.g., half- or full-bridge circuits, B6 bridge circuits, or so-called flying-cap topologies, and can optionally be operated bidirectionally. Power converters designed as DC / AC converters are also referred to as inverters.Bridge circuits in inverters, so-called inverter bridges, can be designed in single-phase and three-phase inverters and can have a corresponding number of power stages, the electrical and electronic components of which can be arranged in particular on one or more printed circuit boards. State of the art

[0002] It is known to use power semiconductors as power switches in higher-power converters, e.g., in inverters for power generation systems or energy storage systems. These power semiconductors are designed as discrete THT components (THT Through Hole Technology) and arranged on a circuit board alongside other electrical components of the converter. It is also possible to combine several power switches in a so-called power module and arrange such a power module on a circuit board, for example, using press-fit contacts.

[0003] The power switches of a power converter are usually operated in a clocked mode, whereby the highest possible clock frequency can be advantageous for various reasons. The maximum achievable switching frequency of an inverter can be limited by the achievable clock frequency of the power switches. When using conventional silicon-based power switches, such as IGBTs, this maximum switching frequency can lie beyond the frequency ranges in which these switches are typically operated due to the losses that predominantly occur during switching operations. In power switches designed as SiC or GaN semiconductors, power-dependent conduction losses predominate, so an increase in the switching frequency can be desired, which in turn increases the influence of any parasitic inductances.

[0004] From DE 10 2013 215 647 A1, a power electronic module is known in which a substrate with a power electronic switching element is connected to a printed circuit board via insulating layers and contacting pins, so that the switching element is arranged between the substrate and the printed circuit board.

[0005] US 9 485 865 B2 discloses an inverter in which electronic components of the inverter are arranged between two substrates that are fixed at a defined distance by spacers.

[0006] From JP 2012-195 374 A a semiconductor device is known in which a semiconductor element is arranged on a metal substrate, wherein the metal substrate is arranged on a heat sink and is connected to further components by a circuit board above the metal substrate.

[0007] DE 43 261 04 A1 discloses an electrical assembly comprising a plurality of printed circuit boards provided with conductor tracks, which are arranged parallel to one another and connected to one another by means of soldering points, wherein electrical components are arranged between the printed circuit boards.

[0008] From US 2013 / 0 077 252 A1 an electrical connector with a processor, an auxiliary board and a main board is known, in which the processor is arranged on the auxiliary board and the auxiliary board is connected to the main board via conductive layers and solder pads, wherein the processor is arranged on the same side of the auxiliary board as the main board in a recess of the main board.

[0009] US 2016 / 0 050 768 A1 discloses an integrated power module in which semiconductor modules are arranged between two metal layers and embedded by lamination. Task

[0010] The application is based on the object of providing an improved power semiconductor arrangement which, in particular, enables improved heat dissipation during operation in a power converter and / or better assembly of the power converter. Solution

[0011] The object is achieved by a power semiconductor device having the features of independent claim 1. Advantageous embodiments are claimed in the dependent claims. Description

[0012] A power semiconductor arrangement comprises a first circuit board, at least one second circuit board, and at least one power semiconductor. The at least one power semiconductor is arranged partially or completely within the second circuit board. The first circuit board is electrically connected to the second circuit board, and the at least one power semiconductor is electrically connected to the second circuit board.

[0013] The first circuit board is mechanically connected to the second circuit board via a conductive short-distance connection. The short-distance connection establishes a mechanical connection between the first and second circuit boards, which determines the spatial position of the first and second circuit boards relative to one another. This offers the advantage that circuit boards with optionally different properties can be combined and mechanically connected using a short-distance connection technology in order to realize a thermally and electrically optimized design of a power semiconductor arrangement. The short-distance connection preferably also represents the electrically conductive connection for the working current that is exchanged between the first and second circuit boards and the electrical components arranged thereon.

[0014] The power semiconductor is arranged between an upper copper layer and a lower copper layer of the second circuit board, wherein the upper copper layer has conductor tracks that establish electrical connections between the power semiconductor and the short-distance connection. The second circuit board has a further copper layer below the lower copper layer. Such a further copper layer preferably has at least the same area as the lower copper layer and is electrically insulated from the lower copper layer. The further copper layer can form a cooling surface of the second circuit board as a whole, in particular by the further copper layer at least partially forming the lower surface of the second circuit board.

[0015] In one embodiment, the first circuit board predominantly comprises a first board material and the at least one second circuit board predominantly comprises a second board material. The first board material is different from the second board material. In particular, a basic structure of the first circuit board consists of the first board material and a basic structure of the second circuit board consists of the second board material. A basic structure of a circuit board is, for example, a carrier board or a predominantly carrier material. Conductor tracks, for example, are inserted or embedded in the basic structure, and components, for example, can be placed on the basic structure.This embodiment offers the advantage that printed circuit boards with different properties can be combined and - optionally by means of a short-distance connection technology - electrically and mechanically connected in order to realize a thermally and electrically optimized structure of a power semiconductor device.

[0016] The two aforementioned embodiments combined make it possible to use a power semiconductor with a high switching frequency, for example, in a switching cell and / or a power stage, and in particular in a power converter with a compact and therefore cost-effective housing for converting electrical power. In particular, the dissipation of the heat generated at high switching frequencies is improved and the need for cooling surfaces on the power converter is reduced by arranging the power semiconductors separately on the second circuit board, and by optimizing the second circuit board to dissipate the heat loss of the power semiconductors to the cooling surfaces.

[0017] Preferably, at least three electrical connections are implemented between the first and second circuit boards, namely to transport power from the first to the second circuit board, to transport power in the opposite direction from the second to the first circuit board, and to transport bidirectional signals via a signal line. The power semiconductor is electrically arranged between the electrical connections that exchange electrical power with the first circuit board and can establish and interrupt the power flow between these electrical connections in a clocked manner. The signal line can have two separate channels, in particular a forward channel and a return channel. The electrical connections should preferably maintain a certain distance from one another for the purpose of insulation coordination.

[0018] From a mechanical point of view, it can be advantageous to implement a plurality of short-distance connections, since fixing the second circuit board to the first circuit board by means of a single short-distance connection can lead to deformation of the circuit boards or similar. In embodiments, a plurality of short-distance connections can therefore be used, which can be arranged around the power semiconductor, for example, like support pillars. It is possible, for example, that only some of these short-distance connections also establish an electrical connection and others have a purely mechanical function. This means that, for example, circuit breakers whose power connections are all on the same side of the circuit breaker can be arranged on the second circuit board and electrically connected to the first circuit board.In particular, two short-distance connections on the terminal side of the circuit breaker can be used for electrical and mechanical connections, and another short-distance connection on the opposite side of the circuit breaker can be used for purely mechanical connections. This results in combinations of two or more mechanical connections, only some of which are electrically active, i.e., have power or signal channels.

[0019] In one embodiment of the power semiconductor arrangement, the second plate material, of which the second circuit board is predominantly made, is more thermally conductive than the first plate material, of which the first circuit board is predominantly made. This enables improved heat dissipation of the at least one power semiconductor. For example, it is possible for the first circuit board to be predominantly made of a glass fiber resin composite material, and the second circuit board to be predominantly made of metal.

[0020] In one embodiment of the power semiconductor arrangement, the first board material is a glass fiber resin composite material, and the first circuit board has conductor tracks that run on multiple levels in the first circuit board and are made in particular of copper. A conductor track establishes, for example, a horizontal connection, i.e., a connection running parallel to the surfaces of the circuit board between two points on the circuit board. Several conductor tracks can be located next to one another in a conductor track level. For each electrical connection that ultimately leads to a power switch on the second circuit board, a conductor track can be provided that leads to the position of a short-distance connection on the first circuit board.

[0021] The first circuit board preferably has a base structure made of a fiberglass-resin composite material. Copper layers are inserted into the base structure as conductor track levels. The thermal conductivity of the first circuit board is essentially determined by the fiberglass-resin composite material, which has a rather low thermal conductivity, while the majority of the heat is conducted by the thermally highly conductive copper of the conductor tracks of the conductor track level, albeit in a direction parallel to the surface of the first circuit board. The first circuit board can be, for example, 2-4 mm thick and have, for example, six layers of copper, each layer having a thickness of 70 µm. In such a board, the copper content of the board or thickness of the total thickness is less than 20%.

[0022] In one embodiment of the power semiconductor arrangement, the second plate material is a metal, in particular copper or aluminum, and the at least one second printed circuit board has in particular exactly one level with conductor tracks.

[0023] In particular, the conductor track level of the at least one second printed circuit board has exactly three conductor tracks.

[0024] The second circuit board, for example, has a metallic base structure, in particular a carrier plate. The second circuit board is therefore well suited for heat dissipation. It can also feature electrical insulation and a heat-spreading layer. Instead of a carrier plate, a design with copper inlays is also possible.

[0025] The electrical contacting of SMD components on the second circuit board can be achieved, for example, via near-surface conductor tracks. The second circuit board has, for example, a 2-3 mm thick carrier plate as a metallic base or a corresponding copper inlay, a 200 µm thick insulation layer, two approximately 35 µm thick copper layers (one as a heat spreader layer and one as a conductor track level), and a further 100 µm thick insulation layer between them. This structure has a copper content of over 80% across the cross-section.

[0026] In one embodiment of the power semiconductor arrangement, the distance between the first and the at least one second printed circuit board is less than 5 mm, preferably less than 1 mm, wherein the distance is determined in particular via the thickness of the short-distance connection.

[0027] In one embodiment of the power semiconductor arrangement, the short-distance connection establishes one or more electrical connections between the first circuit board, in particular the conductor tracks of the first circuit board, and the second circuit board, in particular the conductor tracks of the second circuit board, wherein the short-distance connection was established in particular by pressing, soldering, welding, or gluing. During welding, for example, copper layers of the first and second circuit boards are welded together. During soldering, connection pads can be electrically and mechanically connected to one another using a solder material.

[0028] In one embodiment of the power semiconductor arrangement, the short-distance connection comprises a ball grid array for soldering. In the ball grid array, a "ball," which after soldering establishes one of many point electrical contacts between the first and second circuit boards, can be an electrical channel, i.e., a connection between a conductor track of the first circuit board and a conductor track of the second circuit board.

[0029] Alternatively, the short-distance connection can comprise fibrous metal structures to create a metallic hook-and-loop fiber connection. In a hook-and-loop fiber connection, a channel typically comprises a minimum number of individual "fibers" of the hook-and-loop connection or has at least a minimum surface area, which particularly influences the current-carrying capacity of this channel.

[0030] The short-distance connection can connect the first and second printed circuit boards at more than one location. The ball grid array can have multiple electrically isolated connections, each comprising clusters of multiple channels. The metallic fiber-hook connection can establish multiple separate electrical connections between the first and second printed circuit boards via multiple bundles of fibers. A ball grid array or a fiber-hook connection is considered a mechanical connection, even if it has multiple clusters or bundles and establishes multiple separate electrical connections.

[0031] In one embodiment of the power semiconductor arrangement, an electrical connection via the short-distance connection has a plurality of electrical channels, for example several dozen soldering points of a ball grid array. In particular for the transfer of electrical power between the first circuit board and the second circuit board, a plurality of channels can be combined to form a group, wherein a group for transferring electrical power preferably has 10 or more channels. A group can, for example, consist of a cluster of "balls" of the ball grid array or comprise a partial area of ​​a hook-and-loop fiber connection. Such an electrical connection enables, in particular, the transfer of a substantial proportion of a rated power, e.g. of an inverter, via the power semiconductor arrangement.

[0032] In one embodiment of the power semiconductor arrangement, the short-distance connection comprises at least one control and / or signal channel, which enables a transmission of signals via individual channels, in particular a single-digit number of channels.

[0033] In one embodiment of the power semiconductor arrangement, the at least one power semiconductor is electrically connected to the short-distance connection via conductor tracks of the second circuit board and is arranged on a surface of the second circuit board. The electrical connection of the at least one power semiconductor to at least one conductor track of the second circuit board is achieved in particular via surface contacts on a surface of the second circuit board.

[0034] In one embodiment of the power semiconductor arrangement, the first circuit board has a recess, so that the at least one power semiconductor is arranged within the recess in the assembled state of the power semiconductor arrangement.

[0035] In one embodiment of the power semiconductor arrangement, the electrical connection of the power semiconductor arranged within the second circuit board to at least one conductor track of the second circuit board is established via a hole filled with electrically conductive material through a filler material enclosing the power semiconductor. The power semiconductor can thus be considered integrated into the circuit board, for example, by being arranged in a recess filled with a potting compound and covered with a structured upper copper layer with conductor tracks.To contact the power semiconductor with the conductor track, the potting surrounding the power semiconductor and the copper layer are drilled out at suitable locations, particularly at the level of the power semiconductor's electrical connections, and the connections of the power semiconductor are contacted with the copper layer and thus with the conductor tracks of the second circuit board via a conductive filler material. The conductive filler material can be solder, for example, or can be generated by galvanic deposition of copper. It is also possible to arrange the power semiconductor in a recess and to press it together with the individual layers of the circuit board in a form-fitting manner or to pot it flush with the surface of the circuit board, whereby the conductor track can be located, for example, on or just below the surface of the second circuit board.

[0036] The lower copper layer of the second circuit board can be designed as a heat-spreading layer and thermally connected to a cooling surface of the power semiconductor. The lateral dimension of the lower copper layer is at least twice as large as the cooling surface of the power semiconductor to ensure efficient heat dissipation over a larger area.

[0037] With the design of the described embodiments, the switching cells and / or the power stages of a power converter can be optimally cooled and have a compact design. Compared to conventional assembly and connection concepts with THT components and / or integrated power modules on standard circuit boards, the compact design results in, for example, lower line inductances. For a given cooling capacity of a peripheral of the at least one power switch, in particular with a given heat sink, higher switching speeds can be achieved and / or higher power levels can be realized.

[0038] With the described embodiments, a higher power can be achieved with the same space requirement of the power semiconductor arrangement, e.g., the switching cell, and the complexity of manufacturing and assembly can be reduced. This expands, in particular, the possible applications of SiC- and / or GaN-based power switches in power converters, which can convert high electrical power at a high switching frequency if suitable heat dissipation is ensured according to the claimed embodiments. Possible parasitic inductances are reduced and heat dissipation is improved, so that the switching frequency and / or switching speed can be improved. The described power semiconductor arrangements can be constructed compactly to increase the possibilities for arrangement in housings and / or power modules.In addition, the power semiconductor arrangements, in particular those with a plurality of switches made of power semiconductors, can be assembled without a corresponding plurality of press-in connections having to be produced simultaneously, which makes the assembly process more efficient and simpler and in particular helps to avoid manual assembly of individual power modules.

[0039] The described power semiconductor devices can be used in bridge circuits for power converters, especially in inverters. Bridge circuits in inverters are also called inverter bridges.

[0040] In one embodiment, an inverter bridge comprises a power semiconductor arrangement having at least four power semiconductors in a single-phase bridge circuit, each of which is arranged individually on respective second circuit boards, wherein these second circuit boards are electrically connected to the same first circuit board.

[0041] In one embodiment, the inverter bridge comprises a power semiconductor arrangement with at least four power semiconductors in a single-phase bridge circuit, wherein the power semiconductors are arranged in pairs on at least two second circuit boards or completely on exactly one common second circuit board.

[0042] In one embodiment, the inverter bridge comprises a power semiconductor arrangement having at least six power semiconductors in a three-phase bridge circuit, each of which is arranged individually on respective second circuit boards, wherein the second circuit boards are electrically connected to the same first circuit board.

[0043] In one embodiment, the inverter bridge comprises a power semiconductor arrangement with at least six power semiconductors in a three-phase bridge circuit, wherein the power semiconductors of one phase of the three-phase bridge circuit are each arranged together on a second printed circuit board.

[0044] An inverter according to the invention comprises an inverter bridge according to one of the described embodiments and a heat sink. The power semiconductor arrangement of the respective inverter bridge is preferably mounted on a heat sink that exchanges heat with the environment. The second circuit board is arranged between the first circuit board and the heat sink, ensuring good thermal contact between the power semiconductor and the heat sink. Short description of the characters

[0045] In the following, the invention is explained in more detail with the help of figures. Fig. 1 shows schematically a power semiconductor device; Fig. 2 schematically shows another embodiment of a power semiconductor device; Fig. 3 shows schematically a further embodiment of a power semiconductor device, Fig. 4 shows schematically a cross-section of a second circuit board with integrated power semiconductor, Fig. 5 shows schematically a cross section of a second printed circuit board with integrated power semiconductor in a further embodiment, Fig. 6 shows a schematic plan view of a second circuit board and Fig. Figure 7 shows a schematic plan view of a bridge circuit.

[0046] In the figures, identical or similar elements are designated by the same reference numerals. Character description

[0047] In Fig. 1 shows a power semiconductor device 10 with a first circuit board 14 and a second circuit board 16.

[0048] Electrical components for operating the power semiconductor arrangement 10 in a power electronic converter, e.g., SMD components 32 and / or THT components 28, are located on the first circuit board 14. The first circuit board 14 is of conventional design and can, in particular, consist predominantly of plastic, for example, a glass fiber resin composite material. The first circuit board 14 is arranged above and substantially parallel to the second circuit board 16. A power semiconductor 12, e.g., a semiconductor power switch as part of a bridge circuit of a power electronic converter, can be of SMD design and can be located on the side facing the first circuit board 14 in the assembled state, in Fig. 1 are located on the top side of the second circuit board 16. The second circuit board 16 is thermally optimized, ie, in particular, optimized to effectively transport heat from a component on one side of the circuit board 16, in particular from the power semiconductor 12, to the other side of the circuit board 16, in Fig. 1, i.e., from its top to its bottom. On its underside, the second circuit board 16 is connected to a heat sink 24 with fins 26 via an optional thermal paste 22. Thus, the power semiconductor 12 is located between the first circuit board 14 and the second circuit board 16.

[0049] The circuit boards 14, 16 are mechanically and optionally electrically connected to one another via generally conductive short-distance connections 18. In particular, the circuit boards 14, 16 can be soldered to one another via the short-distance connection 18, e.g., via a ball grid array. Alternatively, to create the short-distance connection 18, respective copper layers of the two circuit boards 14, 16 can be welded to one another. Further alternatively, the circuit boards 14, 16 can be electrically connected to one another via an electrically conductive mechanical hook-and-loop fastener, wherein the hook-and-loop fastener can be produced, for example, using a hook-and-loop welding process. A hook-and-loop welding process is described, for example, in DE 10 2017 126 724 A1. Such a hook-and-loop fastener can be designed to be detachable, for example to enable the repair of components.A Velcro fastener can also be designed to be non-removable, whereby a connection between the fibers is created at the atomic lattice level when pressure and / or temperature are applied, similar to the cold welding of metals.

[0050] At least one power semiconductor 12 is located on the second circuit board 16. The power semiconductor 12 can, in particular, have three connections, wherein electrical power can flow between two connections or can be interrupted by a switching element, while the third connection serves to control the switching element. Therefore, for the operation of a power semiconductor 12, at least three mutually insulated electrical conduction paths can lead from the first circuit board 14 to the second circuit board or back, of which, in particular, two conduction paths for electrical power and one conduction path as a control and / or signal line. If there are several power semiconductors 12 on the second circuit board 16, a corresponding plurality of connections or conduction paths must be provided between the first circuit board 14 and the second circuit board 16. In this case, several (power) connections can be combined in a short-distance connection 18, e.g.in that several ball grid subarrays of a BGA or several fiber bundles of a hook-and-loop fastener each represent individual electrical conduction paths. Several or all of the conduction paths can be combined in a short-distance connection 18, so that a short-distance connection 18 can establish several separate connections between conductor tracks of the circuit boards 14, 16 and the components connected to them. Individual short-distance connections 18 can alternatively or additionally also fulfill a purely mechanical function, i.e., not establish an electrical connection between components on the circuit boards 14, 16. Any short-distance connections 18 with a purely mechanical function can connect conductor tracks of the circuit boards 14, 16 to one another in order to ensure mechanical stability, whereby these conductor tracks are then not connected to any components or other conductor tracks.

[0051] The thermally optimized second circuit board 16 is thermally connected to a heat sink 24. A heat transfer layer 22 can be arranged between the underside of the second circuit board 16 and a cooling surface of the heat sink 24. The heat transfer layer 22 can be embodied as a TIM (thermal interface material). The TIM can comprise a thermally conductive paste or a thermally conductive foil and may be metallic to provide particularly good thermal conductivity if insulation is already integrated into the second circuit board 16 between the power semiconductor 12 and the metallic base plate.

[0052] The cooling surface of the heat sink 24 can have a pedestal on which the second circuit board 16 with the power semiconductor 12 is arranged. This allows the distance between the first circuit board 14, which is equipped with THT components 28 and SMD components 32, and the heat sink 24 to be sufficiently large, ensuring an air gap for insulation coordination. At the same time, the distance between the first circuit board 14 and the second circuit board 16 can be designed so small that it can be bridged by the short-distance connection 18.

[0053] In Fig. 2 shows an embodiment of a power semiconductor arrangement 20. Here, the overall height of the power semiconductor 12 is greater than the distance between the first circuit board 14 and the second circuit board 16. A recess 34, e.g., a milled recess, is provided in the first circuit board 14 in the region of the power semiconductor 12. In the assembled state of the power semiconductor arrangement 20, the recess 34 is arranged above the power semiconductor 12 such that the power semiconductor 12 protrudes upward through the first circuit board 14. The short-distance connections 18 bridge the remaining distance between the circuit boards 14, 16, wherein the distance can be less than one centimeter. When using a correspondingly thin short-distance connection, for example, a suitable ball grid array, the distance between the circuit boards 14, 16 can be less than 5 mm, preferably even less than 1 mm.

[0054] In Fig. 3 shows an embodiment of a power semiconductor arrangement 30. Here, the power semiconductor 12 is arranged within the second circuit board 16. The power semiconductor 12 can be arranged, for example, in a recess or trough in the second circuit board 16, which can be filled after the insertion of the power semiconductor 12. In this embodiment, the distance between the circuit boards 14, 16 can be very small and is limited only by the thickness of the short-distance connection. In contrast to the embodiment according to Fig. 2, the first circuit board 14 has no milling in the area of ​​the power semiconductor 12.

[0055] In Fig. 4 schematically shows a section through a second circuit board 16 with integrated power semiconductor 12. Such a circuit board 16 can be used in particular in the embodiment according to Fig. 3 can be used. The power semiconductor 12 is largely surrounded by the second circuit board 16 in a form-fitting manner, in that the power semiconductor 12 is arranged in a recess of the second circuit board 16, which was subsequently filled with a suitable filling compound, so that the surface of the power semiconductor 12 is covered with the filling compound.

[0056] The power semiconductor 12 has a first contact 44 and a second contact 46. An upper copper layer 42 is located above the power semiconductor 12. The upper copper layer 42 is not continuous or full-surface, but rather divided into conductor tracks 42a, 42b. The conductor tracks 42a, 42b are connected to the first contact 44 and the second contact 46, respectively. This connection can be realized, for example, by holes 40 that extend from the copper layer 42 through the cover layer of the filler compound to the respective contact 44, 46 and are filled with conductive material. This connects the contacts 44 and 46 to the conductor tracks 42a and 42b, respectively.

[0057] The illustrated second circuit board 16 has a lower copper layer 36 below the power semiconductor 12, which is designed as a heat spreading layer. This heat spreading layer can in particular consist of copper or of another metal, e.g. aluminum. The lower copper layer 36 is in thermal contact with a cooling surface 38 of the power semiconductor 12, which cooling surface is provided for dissipating heat loss from the power semiconductor 12 to the environment. The lower copper layer 36 in particular has an extension that is significantly larger than the cooling surface 38 and, due to its good thermal conductivity, acts as a heat spreading layer to improve heat dissipation from the second circuit board 16 by distributing the heat from the power semiconductor 12 in a horizontal direction, i.e. parallel to the surface of the second circuit board 16, over a larger area.The lower copper layer 36 can form the lower surface of the second circuit board 16 and in the assembled state of the circuit board assembly, e.g. according to . Fig. 3, mounted on a heat sink 24.

[0058] Fig. Figure 5 shows a section through a second circuit board 16 with an integrated power semiconductor 12 in a further embodiment. The second circuit board 16 has a further copper layer 48, which is located above the upper copper layer 42 and is divided into two conductor tracks 48a, 48b, which are each connected to the conductor tracks 42a, 42b and thus to the contacts 44 and 46, respectively. The conductor tracks 48a, 48b are located on the surface of the second circuit board 16 and serve to connect the contacts 44, 46 of the power semiconductor 12 via the short-distance connections 18 to the conductor tracks of the first circuit board 14 (see Fig. 3). Furthermore, the second circuit board 16 according to Fig. 5 has a further copper layer 50, which is located below the lower copper layer 36 and is electrically insulated from it. The further copper layer 50 can form the lower surface of the second circuit board 16 and serve as a cooling surface for the second circuit board by dissipating heat loss from the power semiconductor 12 via the lower copper layer 36 and the further copper layer 50 to the environment, in particular to a heat sink 24 on which the second circuit board 16 can be mounted (cf. Fig. 3). During operation of a suitably equipped power converter, the heat loss of the power semiconductor 12 is thus initially distributed over a larger area via a heat spreading layer and then introduced into the cooling fins 26 of the heat sink 24 via a cooling surface with an even larger area in a path that is as direct and unobstructed as possible, yet electrically insulated, and from there dissipated to the environment.

[0059] Fig. 6 shows a second circuit board 16 with two power semiconductors 12 in a top view. In this example, the second circuit board 16 has a total of five short-distance connections 18a-18d, which are designed here as ball grid arrays with a plurality of solder points 54. The short-distance connections 18a and 18b are each connected via conductor tracks 42a, 42b to one of the contacts 44, 46 of the power semiconductors 12 (compare, for example, Fig. 4). Another conductor track 42c connects the other contacts of the power semiconductors 12 to each other and to another short-distance connection 18c. The additional short-distance connections 18d are optional and not connected to conductor tracks. The power semiconductors 12 are connected to control terminals 52, via which the power semiconductors 12 can be switched on and off.

[0060] Fig. Figure 7 shows a bridge circuit with a section of a first circuit board 14 and a second circuit board 16 located "behind" it in a plan view. The first circuit board 14 has a recess 34, see Fig. 2; alternatively, the recess can be omitted, compare Fig. 1 or Fig. 3. On the first circuit board 14, two capacitors 28a, 28b are arranged as THT components, which can in particular form two potentials DC+, DC- of a DC voltage intermediate circuit. The potentials DC+, DC- are connected via conductor tracks in the first circuit board 14 to short-distance connections 18a, 18b. The potentials DC+, DC- are connected via the short-distance connections 18a, 18b to the conductor tracks 42a, 42b of the second circuit board 16 and thus applied to the power semiconductors 12. The second circuit board 16 can in particular be designed according to Fig. 6, whereby the short-distance connections 18d with only mechanical function in Fig. 7 are not visible.

[0061] By appropriately controlling the power semiconductors 12, for example, by means of the control components 32, the DC+ and DC- potentials can be selectively switched through to the conductor track 42c and thus to the short-distance connection 18c. Via the short-distance connection 18c, the thus clocked DC+ and DC- potentials reach another conductor track of the first circuit board 14, which can be used, for example, as an AC potential and, after suitable filtering and the like, can subsequently form an AC output of the bridge circuit or of an inverter comprising the bridge circuit.

[0062] During operation of an inverter according to the invention, the power semiconductors 12 are switched on and off in a clocked manner. Assuming a suitable voltage in the capacitors 28a, 28b of the DC link, a current can be generated at the AC output of the bridge circuit, which current flows, depending on the half-cycle, from one of the capacitors 28a, 28b via the short-distance connection 18a or 18b to one of the power semiconductors 12 and is then passed (clocked) via the short-distance connection 18c to the AC output. Depending on the topology, a specific inverter can comprise one or more bridge circuits, for example, according to Fig. 7, wherein each bridge circuit may comprise one or more power semiconductors 12, which may each be arranged individually or jointly on one or more second circuit boards 16. List of reference symbols 10, 20, 30 power semiconductor arrangement 12 power semiconductors 14 first circuit board 16 second circuit board 18 short-distance connection 18a, 18b, 18c, 18d Short-distance connections 22 Thermal paste 24 heat sinks 26 Finn 28 THT components 28a, 28b capacitors 32 SMD components 34 recess 36 copper layers 38 cooling surface 40 holes 42 copper layers 42a, 42b Conductor tracks 44 first connection 46 second connection 48 copper layers 48a, 48b Conductor tracks 50 copper layers 52 control connections 54 soldering point

Claims

[1] Power semiconductor arrangement (10, 20, 30) with at least one first circuit board (14), at least one second circuit board (16) and at least one power semiconductor (12), wherein the at least one power semiconductor (12) is arranged partially or completely within the at least one second circuit board (16), wherein the at least one first circuit board (14) is electrically conductively connected to the at least one second circuit board (16) and the at least one power semiconductor (12) is electrically conductively connected to the at least one second circuit board (16), and wherein the at least one first circuit board (14) is mechanically connected to the at least one second circuit board (16) via a conductive short-distance connection (18), wherein the at least one power semiconductor (12) is arranged between an upper copper layer (42) and a lower copper layer (36) of the at least one second circuit board (16),wherein the upper copper layer (42) has conductor tracks (42a, 42b) which represent an electrical connection between the at least one power semiconductor (12) and the short-distance connection (18), wherein a further copper layer (50) is arranged below the lower copper layer (36), wherein the further copper layer (50) has at least the same area as the lower copper layer (36), is electrically insulated from the lower copper layer (36) and forms a cooling surface of the at least one second printed circuit board (16). [2] Power semiconductor arrangement (10, 20, 30) according to claim 1, wherein the at least one first circuit board (14) has a first plate material and the at least one second circuit board (16) has a second plate material and the first plate material is different from the second plate material. [3] The power semiconductor device according to claim 2, wherein the second plate material is more thermally conductive than the first plate material. [4] Power semiconductor arrangement according to one of the preceding claims, wherein the at least one second circuit board (16) establishes a thermally conductive connection between the at least one power semiconductor (12) and a heat sink (24). [5] Power semiconductor arrangement according to one of claims 2 and 3, wherein the first plate material is a glass fiber resin composite material and the at least one first circuit board has conductor tracks which run on several levels in the first circuit board and are in particular made of copper. [6] Power semiconductor arrangement according to one of the preceding claims, wherein the distance between the at least one first and the at least one second printed circuit board (14, 16) is less than 5 mm, preferably less than 1 mm, and the distance is determined in particular via the short-distance connection (18). [7] Power semiconductor arrangement according to one of the preceding claims, wherein the short-distance connection (18) establishes electrical connections between the at least one first printed circuit board, in particular conductor tracks of the at least one first printed circuit board (14), and the at least one second printed circuit board (16), in particular conductor tracks of the at least one second printed circuit board (16), wherein the short-distance connection (18) was established in particular by pressing in, soldering, welding or velcro. [8] Power semiconductor arrangement according to claim 7, wherein the short-distance connection (18) is designed as a ball grid array or metallic velcro fiber connection. [9] Power semiconductor arrangement according to claim 7 or 8, wherein the electrical connection via the short-distance connection (18) has a plurality of electrical channels, wherein in particular for the transfer of electrical power between the at least one first circuit board (14) and the at least one second circuit board (16) a plurality of channels can be combined to form a group, wherein a group preferably has ten or more channels. [10] Power semiconductor arrangement according to one of claims 7 to 9, wherein the short-distance connection (18) comprises at least one control and / or signal channel which enables transmission of signals via individual channels, in particular via a single channel of the channels of the short-distance connection (18). [11] Power semiconductor arrangement according to one of claims 6 to 10, wherein the at least one power semiconductor (12) is electrically connected to the short-distance connection (18) via conductor tracks of the at least one second printed circuit board (16) and is arranged on a surface of the at least one second printed circuit board (16), wherein the electrical connection of the at least one power semiconductor (12) to at least one conductor track of the at least one second printed circuit board (16) is made via at least one surface contact on a surface of the at least one second printed circuit board (16). [12] Power semiconductor arrangement according to claim 1, wherein the electrical connection of the at least one power semiconductor (12) to the conductor tracks of the at least one second printed circuit board (16) is made via holes (40) filled with electrically conductive material. [13] Power semiconductor arrangement according to claim 1, wherein the lower copper layer (36) is thermally connected to a cooling surface (38) of the at least one power semiconductor (12) and has an extent which is at least twice as large as the cooling surface (38) of the at least one power semiconductor (12). [14] Inverter bridge, with at least one power semiconductor arrangement (10, 20, 30) according to one of the preceding claims. [15] Inverter bridge according to claim 14, comprising at least four power semiconductors (12) in a single-phase bridge circuit, each individually arranged within a respective second circuit board (16), said at least four second circuit boards (16) being electrically connected to the same at least one first circuit board (14). [16] Inverter bridge according to claim 14, comprising at least four power semiconductors (12) in a single-phase bridge circuit, wherein the at least four power semiconductors (12) are arranged in pairs on at least two second printed circuit boards (16) or completely on exactly one common one of the at least one second printed circuit board (16). [17] Inverter bridge according to claim 14, comprising at least six power semiconductors (12) in a three-phase bridge circuit, each individually arranged within a respective second circuit board (16), wherein the at least six second circuit boards are electrically connected to the same at least one first circuit board (14). [18] Inverter bridge according to claim 15, comprising at least six power semiconductors (12) in a three-phase bridge circuit, wherein the power semiconductors (12) of one phase of the three-phase bridge circuit are each arranged together on one of the at least one second printed circuit board (16). [19] Inverter with an inverter bridge according to one of claims 15 to 18 and a heat sink (24), wherein the power semiconductor arrangement (10, 20, 30) is mounted on the heat sink, wherein the at least one second circuit board (16) is arranged between the at least one first circuit board (14) and the heat sink (24).

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