Semiconductor component, motor vehicle and method for manufacturing a semiconductor component

Description

[0001] The invention relates to a method for producing a semiconductor device, which comprises the following steps: Providing at least one semiconductor module and a support frame which has a respective opening for each of the semiconductor modules, arranging the at least one semiconductor module on the support frame such that a base plate of the respective semiconductor module rests on the edge of the respective opening, soldering the respective base plate to the support frame, wherein the respective base plate is soldered to the support frame using a solder having a melting point of at least 450°C.

[0002] Three-phase inverters or rectifiers formed by semiconductor switches can be used to drive a three-phase electric machine using direct current or to provide direct current using a three-phase generator. In this case, it is possible to design the entire bridge circuit as an encapsulated component, which can then be mounted on a heat sink or similar, for example. However, if the individual semiconductor components are to be bonded to a substrate by sintering, constructing the entire bridge circuit as a single module represents a relatively high economic risk, as the individual components cannot be bonded and tested separately. The pressure generated during sintering would typically destroy corresponding wire bonds.

[0003] However, when smaller assemblies are used, it can be relatively complex to provide a common cooling system for all semiconductor switches. For example, in the cooling of electrical components disclosed in US 2003 / 0053298 A1, the component-supporting base plates are welded to a component that forms the cooling channels. Due to the high temperatures encountered during a welding process, however, the welds should be located relatively far away from sensitive semiconductor components, so the resulting assembly may be unnecessarily large or require a relatively complex design. Furthermore, ensuring that welded joints are fluid-tight along their entire length is relatively complex.

[0004] The publication DE 10 2016 110 043 A1 relates to a liquid-cooled cooling device used to cool a heat-generating body, for example, a semiconductor component. The cooling device comprises a housing through which coolant flows and a heat sink attached to the housing. The heat sink rests on an edge of the tub-shaped housing. The connection to this edge can be made by soldering.

[0005] A cooling device for a semiconductor module, in which an electrode of the semiconductor module is inserted into a recess of a cover of a cooling channel and thereby closes an opening in the cover, is made of

[0006] This is known from JP 2008 159946 A. The connection is made by a layer of brazing material. Brazing is achieved by melting the initially foil-like brazing material in a vacuum furnace.

[0007] Document WO 2017 / 069005 A1 discloses a method for manufacturing a semiconductor module in which a heat sink engages a recess in a housing. The connection is made by a solder, which, according to the abstract, is melted by induction heating a metallic portion of the housing.

[0008] The document US 2009 / 194862 A1 relates to a semiconductor module with an attached cooling channel. The housing defining the cooling channel is connected to the cooling plate via solder.

[0009] The document JP 2006 222461 A relates to a device for dissipating heat, in which, in one embodiment, a layer of brazing material is arranged between an insulating substrate and a cover of a housing.

[0010] The publication US 2016 / 0183409 A1 relates to power electronics modules that are inserted into recesses of a modular cooling system. A heat transfer plate of the respective power electronics module is attached to the edge of each recess. Various fastening options are mentioned, for example, a mechanical fastening that can be sealed, for example, by an O-ring, soldering, brazing, and ultrasonic welding.

[0011] Publication WO 2018 / 123387 A1 relates to a method for manufacturing a heat exchanger for a liquid cooler. The connection between an upper pan and a base can be achieved using a brazing material.

[0012] The document US 2012 / 0 305 281 A1 relates to a method for joining a metallized ceramic substrate to a metal body. An aluminum-containing metal alloy with a melting point of more than 450°C is placed between these two components, and this entire assembly is heated to a temperature of more than 450°C in a soldering furnace. Plasma soldering, laser soldering, flame soldering, and induction soldering are mentioned as alternatives to using a soldering furnace. Electrical components, such as semiconductor devices, are placed on the ceramic substrate only after the ceramic substrate has been joined to the metal body.

[0013] The invention is therefore based on the object of specifying an improved method for constructing a semiconductor component which can comprise a plurality of semiconductor modules.

[0014] The object is achieved according to the invention by a method of the type mentioned at the outset, wherein the soldering of the respective base plate to the support frame is carried out by laser brazing, wherein the laser is irradiated onto the side of the support frame facing away from the base plate, whereby the support frame is locally heated and the solder is melted by the heated support frame, wherein the material of the support frame is locally melted during the soldering of the respective base plate to the support frame.

[0015] Compared to welding components, a soldered connection, including brazing, can be carried out at considerably lower temperatures by selecting a solder with a suitable melting point. In the method according to the invention, the base plate and the support frame preferably lie flat against one another in a soldered area, so that the liquefied solder is sucked into the space between the two superimposed plate-shaped areas. This achieves robust fluid tightness using simple means. As will be explained in more detail later, this can be used to jointly seal a fluid channel for conducting, for example, liquid coolant through the base plate and the support frame. This makes it possible to achieve very good cooling of the individual semiconductor modules.In other words, it is proposed to firmly bond the base plate and the support frame by means of a solder interposed between them. The soldering is carried out by laser brazing. The base plate supports, in particular, a substrate, which in turn supports the semiconductor components, e.g., semiconductor chips.

[0016] The semiconductor modules rest on the periphery of the opening on all sides, particularly on the periphery. Through all-round soldering, the opening can be completely closed by the respective base plate, which, as explained above, can serve, in particular, to form a cooling channel. The base plate can be soldered to the support frame at least in a section of the area where it rests on the edge of the receptacle. Thus, an overlap connection is used.

[0017] A section of the base plate, in which the base plate is soldered to the support frame, can extend completely around a region of the base plate in which the base plate has projections that extend through the respective opening in the support frame, and it can extend completely around the respective opening in the support frame. The projections of the base plate can in particular be cooling fins, which are preferably permanently in contact with cooling fluid during operation of the semiconductor component. For example, these cooling fins or projections can protrude into a cooling channel that carries the cooling fluid, for example a cooling liquid. By encompassing the region in which the cooling fins are arranged or the entire opening, it can be ensured that the opening through the base plate and the solder connection is completely sealed together.

[0018] The support frame, the respective base plate of the at least one semiconductor module, and a closure element can form a fluid channel that is fluid-tightly sealed on all sides except for a cooling fluid inlet and a cooling fluid outlet. For example, the fluid channel can be fluid-tight with respect to a specific cooling fluid, such as water or oil. The closure element can thus form a type of cover for the cooling channel, wherein the closure element can, in particular, form the cooling fluid inlet and the cooling fluid outlet and can be connected on all sides in an edge region to an edge region of the support frame, or similar.

[0019] The closure element can be soldered or welded to the support frame. As explained above, a fluid-tight connection can be created particularly easily and at relatively low temperatures by soldering. However, since the connection point is typically further away from the semiconductor components of the semiconductor device or semiconductor modules than the connection point between the support frame and the base plate, higher temperatures can also be used and welding can be performed.

[0020] The base plate is soldered to the support frame using a solder with a melting point of at least 450°C. In other words, the base plate and the support frame are joined by laser brazing. This creates a particularly robust connection, while lower temperatures are required for the connection than with a welding process and, as explained above, fluid tightness can be achieved more easily. The solder can in particular have a melting point that is below the melting point of the materials of the base plate and the support frame. In principle, the soldering process can therefore be carried out without the material of the base plate or the support frame being melted. As will be explained later, however, it is also possible for these materials to melt, at least locally.

[0021] Semiconductor components of the respective semiconductor module can be attached to the base plate or a substrate attached to the base plate by sintering, and / or the semiconductor module can be encapsulated with a potting compound. As already explained at the beginning, it is advantageous if semiconductor modules produced by sintering have a relatively low complexity. By producing the semiconductor module according to the invention, a plurality of separately constructed semiconductor modules can be combined with little effort into a single semiconductor component that is easily cooled. Therefore, sintered semiconductor modules with relatively low complexity can be used.

[0022] The individual semiconductor modules can be encapsulated, for example, by transfer molding, also known as resin transfer molding, but also by injection molding or similar methods. In particular, no separate housing is bonded to a substrate or the base plate; instead, the semiconductor module is encapsulated directly, particularly after sintering or bonding the individual components. The encapsulation compound can seal the semiconductor module on all sides, except for exposed contact surfaces and a free side surface of the base plate. These contact surfaces can, in particular, be externally routed contacts.

[0023] The semiconductor module can in particular comprise at least one semiconductor chip arranged on a substrate or on the base plate. The side of the substrate facing away from the semiconductor chip can be connected to the base plate. The side of the substrate facing away from the substrate or the semiconductor chip can have an edge region on its circumference, in which it rests on the support frame. The projections or cooling fins can be arranged in an inner region of this side of the base plate surrounded by this region. The part resting on the support frame can completely encompass the inner region.

[0024] The support frame can be made of aluminum or an aluminum alloy. Additionally or alternatively, the base plate can be made of copper or aluminum or a composite material in which silicon carbide particles are incorporated in an aluminum matrix. If a base plate made of copper is used, it can in particular be nickel-plated. If the composite material described above is used as the base plate, areas in which soldering is to take place can have an aluminum-rich layer to facilitate the creation of a robust soldered connection. The layer thickness of this aluminum-rich layer can, for example, be 0.5 mm or more. The described structure of the base plate or the support frame can in particular ensure that the thermal expansion behavior of the base plate largely matches the thermal expansion behavior of a substrate attached to it, whereby in particular good heat dissipation can be achieved.

[0025] The semiconductor module can be a half-bridge and / or the semiconductor component can be a bridge inverter or bridge rectifier, particularly a three-phase one. Bridge inverters or bridge rectifiers can be identical in terms of their power components, i.e., the semiconductor modules. They differ primarily in the direction of power transmission and thus in their control. The semiconductor component can therefore also be used, for example, as a bridge rectifier and bridge inverter, as needed.

[0026] Also disclosed is a motor vehicle comprising a semiconductor component manufactured by the method according to the invention. The semiconductor component can, in particular, be an inverter for an electric machine of the motor vehicle, in particular for a drive motor. The semiconductor component can additionally or alternatively also serve to provide a direct current during generator operation of the electric machine, for example, to supply a vehicle electrical system or to charge a battery of the motor vehicle.

[0027] During the manufacture of the semiconductor component, at least one semiconductor module, or preferably several semiconductor modules, are attached to the support frame by first placing them in the region of the openings and then soldering their base plate to the support frame in the edge region of the opening. Details of this have already been explained above. Features explained with reference to the semiconductor component can be transferred to the method according to the invention with the advantages mentioned therein.

[0028] According to the invention, the base plate is brazed to the support frame by laser brazing. The process of laser brazing is known in principle in the prior art and is used, for example, in automotive body construction. Here, the workpiece is locally heated by irradiating it with high-energy laser light at a location where the brazing process is to take place. Laser brazing can also produce narrow brazing seams with high precision.

[0029] To produce the semiconductor component, the laser is irradiated onto the side of the support frame facing away from the base plate.

[0030] This locally heats the support frame, and the solder is melted by the heated support frame. This can be particularly advantageous, as it can prevent excessive heating of components of the semiconductor module.

[0031] If, as explained above, a closure element is connected to the support frame, for example to form a cooling chamber, this can also be done by laser soldering or laser brazing.

[0032] The semiconductor component is manufactured as explained in the method according to the invention.

[0033] The connection of the base plate with the support frame and optionally of the support frame with the closure element is made in the method according to the invention by laser brazing.

[0034] During the production of a semiconductor component according to the invention, the material of the support frame is melted locally during the soldering of the respective base plate to the support frame. Optionally, the material of the base plate can also be melted locally. In particular, the material of the support frame can be melted on a side facing away from the base plate. However, it is also possible for the support frame to be melted across its entire thickness and / or for the side of the base plate facing the support frame to be melted. In contrast to a direct material-to-material connection between the support frame and base plate by welding, the soldering according to the invention nevertheless achieves, due to the capillary action between the base plate and the support frame, that solder is drawn between them, thus creating a particularly robust, fluid-tight connection.

[0035] Further advantages and details of the invention will become apparent from the following exemplary embodiments and the accompanying drawings. These schematically show: Fig. 1 shows an embodiment of a semiconductor component according to the invention, Fig. 2 shows a detailed view of the Fig. 1 semiconductor component shown, Fig. 3 an intermediate step in an embodiment of the method according to the invention for producing the Fig. 1 and Fig. 2 shown semiconductor component, and Fig. 4 an embodiment of a motor vehicle according to the invention.

[0036] Fig. 1shows a semiconductor component 1, which can be, for example, a three-phase bridge rectifier or bridge inverter. Since the individual semiconductor components (not shown) should be connected to a substrate by sintering, it may be expedient not to design such a rectifier or inverter as a single module, but rather to use, for example, three semiconductor modules 3, each of which can implement a half-bridge, for example. The internal structure of the individual semiconductor modules 3 and their contacting are not shown in the figures for reasons of clarity. The production of, for example, half-bridges as sintered semiconductor components is known in principle in the prior art and will therefore not be explained.

[0037] In order to nevertheless enable good handling of the semiconductor component 1, which in the example consists of three semiconductor modules 3, and in particular to enable joint cooling of the semiconductor modules 3, the semiconductor modules 3 are arranged on a common support frame 2. The support frame 2 can, for example, be formed from a sheet metal component or the like that has a plurality of openings 6. The semiconductor modules 3 each comprise a base plate 4, which supports the further components, i.e. directly the semiconductor components or a substrate supporting the semiconductor components, and are encapsulated with a potting compound 5. The base plate 4 extends through the openings 6 via projections 16, in particular cooling fins, and rests on the edge 7 of the respective opening 6.

[0038] As will be explained in more detail later, a fluid channel 20 is provided on the side of the support frame 2 facing away from the semiconductor modules 3, through which, for example, liquid coolant can be guided. In order to seal the fluid channel 20, the base plate 4 should be connected to the support frame 2 in a fluid-tight manner. This is achieved in the semiconductor component 1 by soldering the respective base plate 4 to the edge 7 of the respective opening 6 of the support frame 2. This will be explained in more detail below with reference to Fig. 2 and 3 be explained.

[0039] Fig. 2shows an enlarged detailed view of semiconductor component 1. As can be seen there, a solder 8 is arranged between the base plate 4 and the support frame 2 in the region of the edge 7. The solder 8 has a melting point lower than the melting point of the material of the base plate 4 and the support frame 2. To ensure a robust connection even at the relatively high operating temperatures sometimes encountered in semiconductor switches, a solder 8 with a melting point of at least 450°C is used, i.e., brazing is used. Corresponding solders are known in the art and will not be explained in detail.

[0040] Fig. 3 shows an intermediate step in the production of the semiconductor component 1, wherein in this state the closure element 10 is not yet attached to the semiconductor component 1 and wherein Fig. 3a view of the side of the support frame 2 facing away from the semiconductor modules 3. The dashed lines 11 show the section of the base plate 4 in which the respective base plate 4 is soldered to the support frame 2. As in Fig. 3 As can be clearly seen, the solder seam or the section in which soldering takes place completely encompasses the opening 6 or the area in which projections 16 of the base plate 4 penetrate the opening 6. Thus, the opening 6 is completely sealed by the base plate 4 and the solder 8.

[0041] The dashed line 13 in Fig. 3 shows the area where the support frame 2 is soldered to the closure element 10 to form the cooling channel 16. As in Fig. 2As shown, the connection of the support frame 2 to the closure element 10 is thus also made via a solder 12, in particular also by brazing. Alternatively, this connection could also be made by welding, since it is arranged relatively far away from the semiconductor chips in use. By attaching the closure element 10 to the support frame 2 and the fluid-tight connections between the closure elements 10 and the support frame 2 or between the support frame 2 and the base plates 4 using the respective solder 8, 12, the fluid channel 20 is fluid-tightly closed apart from a fluid inlet 14 and a fluid outlet 15. Thus, the projections 16 or cooling fins can have a liquid coolant flow around them, for example in a closed fluid circuit.

[0042] The respective base plates 4 are soldered to the support frame 2, or the support frame 2 is soldered to the closure element 10, by laser soldering. The solder 8, 12 can be applied to one of the components before the soldering process or can be positioned between them. Laser light can then be irradiated into the corresponding area to melt the solder 8, 12 and thus solder the components.

[0043] To solder the base plates 4 to the support frame 2, the laser is Fig. 3 shown side of the support frame 2, that is from below into Fig. 1 Thus, the support frame 2 is heated locally in the area of ​​the dashed lines 11, and with the heating of the support frame, the solder 8 arranged on the other side of the support frame 2 is also melted. It is intended that the materials of the support frame 2 and optionally the base plate 4 are at least locally melted while the materials are soldered.

[0044] Fig. 4 shows, by way of example, a vehicle 17 in which an electric machine 18, in particular a drive motor of the motor vehicle 17, is to be supplied by a battery 19 or another DC voltage source, for example a vehicle network. In order to convert the DC voltage of the battery 19 or the vehicle network into a three-phase AC voltage for operating the electric machine 18, the Figures 1 and 2 The component 1 shown is used as an inverter. The same component 1 could, for example, be used during generator operation of the electric machine 18 to rectify the generated three-phase alternating voltage, for example, to charge the battery 19.

Claims

1. Method for manufacturing a semiconductor component (1), comprising the steps: - providing at least one semiconductor module (3) and a support frame (2), which has a respective opening (6) for each of the semiconductor modules (3), - arranging the at least one semiconductor module (3) on the support frame (2) such that a base plate (4) of the respective semiconductor module rests on the edge (7) of the respective opening (6), - soldering the respective base plate (4) to the support frame (2), wherein the respective base plate (4) is soldered to the support frame (2) with a solder (8) that has a melting point of at least 450°C, characterized in that the soldering of the respective base plate (4) to the support frame (2) is performed by laser brazing, wherein the laser is hereby radiated onto that side of the support frame (2) which faces away from the base plate (4), whereby the support frame is heated locally and the solder is melted by the heated support frame, wherein the material of the support frame (2) is locally melted in the course of soldering the respective base plate (4) to the support frame (2).

2. Method according to claim 1, characterized in that a section of the base plate (4), at which the base plate (4) is soldered to the support frame (2), extends fully around an area of the base plate (4) in which the base plate (4) has projections (16) which extend through the respective opening (6) of the support frame (2) and extends fully around the respective opening (6) of the support frame (2).

3. Method according to claim 1 or 2, characterized in that a fluid channel (20) is formed by the support frame (2), the respective base plate (4) of the at least one semiconductor module (3) and a closure element (10), which fluid channel apart from a cooling fluid outflow (14) and a cooling fluid outflow (15) is closed in a fluid-tight manner on all sides.

4. Method according to claim 3, characterized in that the closure element (10) is soldered or welded to the support frame (2).

5. Method according to any one of the preceding claims, characterized in that semiconductor components of the respective semiconductor module (3) are attached by sintering to the base plate (4) or to a substrate attached to the base plate (4) and / or in that the semiconductor module (3) is cast by a casting compound (5).

6. Method according to any one of the preceding claims, characterized in that the support frame (2) is made of aluminum or an aluminum alloy and / or in that the base plate (4) is made of copper or aluminum or of a composite material, in which silicon carbide particles are incorporated into an aluminum matrix.

7. Method according to any one of the preceding claims, characterized in that the semiconductor module (3) is a half-bridge and / or in that the semiconductor component (1) is a bridge inverter or bridge rectifier.

8. Method according to claim 7, characterized in that the semiconductor component (1) is a three-phase bridge inverter or bridge rectifier.

9. Method according to any one of the preceding claims, characterized in that in the course of soldering the respective base plate (4) to the support frame (2) the material of the base plate (4) is locally melted.