Heat sink for power semiconductors arranged in a semiconductor package and cooling arrangement

Abstract

A heat sink is provided for power semiconductors arranged in a semiconductor package, wherein the heat sink is formed by a tube made of thermally conductive material being brought into a predetermined shape by means of a hydroforming process, which tube has two end regions and a central, flat region located between the end regions, which is formed on one or both sides at least partially for fastening semiconductor packages.

Description

[0001] The present invention relates to the field of electromobility, in particular to electronic modules for an electric drive.

[0002] The use of electronic modules, also known as power electronics, in motor vehicles has increased significantly in recent decades. This is due on the one hand to the need to improve fuel economy and vehicle performance, and on the other hand to advances in semiconductor technology. The main components of such power electronics are an electronic control unit, also known as an ECU (electronic control unit), which is connected to or forms part of the vehicle control unit(s) and receives control signals and / or information based, for example, on driving behavior or signals from other control units, and a DC / AC inverter, which is used to supply electrical machines such as electric motors or generators with multi-phase alternating current (AC).In this process, a direct current generated by a DC energy source, such as a battery or accumulator, is converted into a multi-phase alternating current. For this purpose, an inverter comprises a multitude of electronic components, particularly semiconductor switches (power semiconductors), which are used to create bridge circuits (such as half-bridges). The semiconductor switches are housed in a housing either as individual topological switches or already connected to form a half-bridge, and are therefore also referred to as semiconductor packages. Within the housing, they are protected from external influences. Only their power and signal / control contacts extend to the outside.

[0003] Current inverter designs are characterized by the fact that the power semiconductors in the semiconductor packages must be actively cooled to dissipate switching and conduction losses. To dissipate these losses, a heat conduction path is created from the semiconductor package into a cooling medium. A heat sink, designed as a so-called base plate, is arranged on at least one side of the semiconductor package. Cooling structures in the form of pins or pin fins are typically provided on the side of the base plate opposite the power semiconductors, which ensure improved heat transfer. However, these structures are very complex and therefore expensive to manufacture.

[0004] Therefore, one goal is to provide a heat sink for power semiconductors that is easier to manufacture.

[0005] This problem is solved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0006] A heat sink is provided for power semiconductors arranged in a semiconductor package, wherein the heat sink is formed by a tube made of thermally conductive material being brought into a predetermined shape by means of a hydroforming process, which has two end regions and a central, flat region located between the end regions, which is formed on one or both sides at least partially for fastening semiconductor packages.

[0007] In one embodiment, the tube from which the heat sink is formed has a predetermined structure on its inner surface.

[0008] In one embodiment, a grid of thermally conductive material is inserted into the tube before the hydroforming process is carried out.

[0009] In one embodiment, the central region of the heat sink has a deformation at at least one location which is not formed for fastening semiconductor packages.

[0010] In one embodiment, the deformation is provided on one or both sides of the heat sink.

[0011] In one embodiment, the deformation is formed as uniform or uneven elevations and depressions in a regular or irregular structure.

[0012] In one embodiment, a thickness of the central region is less than a thickness of the end regions.

[0013] Furthermore, a cooling arrangement is provided, comprising at least one semiconductor package with power semiconductors to be cooled arranged therein, and at least one described heat sink, wherein at least one semiconductor package is fastened to a location in the central, flat region.

[0014] In one embodiment, several heat sinks are connected to each other at one end area.

[0015] Furthermore, an electronic module is provided, comprising an inverter with the described cooling arrangement.

[0016] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details of the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention.

[0017] Preferred embodiments of the invention are explained in more detail below with reference to the attached figures. Fig. 1 shows a sectional view of a basic arrangement of a semiconductor package arranged on a heat sink according to the prior art. Fig. 2 shows a heat sink according to an embodiment of the present invention. Fig. 3 shows the Fig. 1 shown heat sink with semiconductor packages arranged thereon. Fig. 4 shows a heat sink according to another embodiment of the present invention. Fig. 5 shows a heat sink according to another embodiment of the present invention. Fig. 6 shows the Fig. 5 shown heat sink with semiconductor packages arranged thereon.

[0018] In the following descriptions of the figures, the same elements or functions are provided with the same reference symbols.

[0019] The invention relates to a cooling arrangement for power semiconductors arranged in a semiconductor package, which act as semiconductor switches and are part of an inverter (DC / AC inverter). The inverter serves to convert direct current (DC) received from an energy storage device, e.g., a battery, into alternating current (AC) usable for the electrical machine to be operated, such as an electric motor.

[0020] As already mentioned at the beginning, the semiconductor switches (power semiconductors) arranged in a semiconductor package 4 must be actively cooled to operate the inverter in order to dissipate the switching and conduction losses generated during operation. To dissipate these losses, a heat conduction path is constructed from the semiconductor package 4 into a cooling medium, which is characterized by the fact that the total thermal resistance should be as low as possible.

[0021] As in Fig. As shown schematically in Figure 1, one or more semiconductor packages 4 are currently mounted on one side of a so-called base plate 2, which serves as a heat sink. The opposite side of the base plate 2 rests on a housing 5 or is connected thereto in a media-tight manner. The housing 5 contains a cooling fluid. Cooling structures 3, such as pins or pinfins, are also generally provided on the side of the base plate 2 opposite the semiconductor packages 4, enabling improved heat dissipation from the semiconductor packages 4 into the cooling fluid.

[0022] Since the provision of the cooling structures 3 such as pins or pin fins is complex, and the entire cooling arrangement requires a relatively large amount of installation space, and in some cases even additional insulation must be provided in order to maintain creepage distances, an improved heat sink 1 and an improved cooling arrangement for cooling semiconductor packages 4 of an inverter are proposed below.

[0023] The new concept does not require pins or pinfins as a cooling structure 3. The new heat sink 1 is a closed cooling system that is formed in one piece by hydroforming (internal high-pressure forming) from a tube made of thermally conductive material such as copper.

[0024] The novel heat sink 1 has a flat surface in a central region 10, at least at points where semiconductor packages 4 are to be attached (it is flat there). Provision can be made for semiconductor packages 4 to be arranged on one or both (outer) sides of the heat sink 1. At end regions 11, it has a shape that can be connected as easily as possible either to an end region 11 of another heat sink 1 or to an inlet or outlet of a cooling medium, e.g., a cooling liquid. A shape with a round cross-section, for example, is suitable for this purpose, although a flattened shape is also conceivable.

[0025] Since the lowest possible height is to be achieved, the heat sink 1 has the smallest possible thickness in the central region 10, where the semiconductor packages 4 are arranged. This means that the tube is hydroformed in such a way that it has the smallest possible thickness, while of course still being able to provide the required cooling capacity. The end regions 11, where no semiconductor packages 4 are provided and which serve as inlets or outlets or as connections to other heat sinks 1, can therefore also be thicker, e.g., round.

[0026] In a first, in Fig. 2 and Fig. In the embodiment shown in Figure 3, the heat sink 1 is formed in a central region 10 between the two end regions 11 with a flat surface and a smaller thickness than the end regions 11. In this embodiment, the heat sink has a smooth surface in its interior.

[0027] In a second embodiment, the heat sink 1 is also formed in a central region 10 between the two end regions 11 with a flat surface and with a smaller thickness than the end regions 11. The difference to the Fig. 2 and Fig. 3 is that the heat sink 1 does not have a smooth surface inside, but a structure as shown in Fig. 4 is schematically indicated by a view of an opening of an end region 11. By using a heat sink 1 with a structure in its interior, the thermal resistance can be improved, so that the coolant can be better conducted through the heat sink 1 and the heat transfer from the surface into the coolant is improved. The structure inside the heat sink 1 can be selected depending on the cooling requirements and the shape of the heat sink 1. For example, the structure can be determined and optimized through thermodynamic simulations. The introduction of structures into tubes is known from the prior art, so it will not be discussed in detail here.

[0028] In a third embodiment (not shown), the heat sink 1 is also formed in a central region 10 between the two end regions 11 with a flat surface and with a smaller thickness than the end regions 11. The difference to the embodiments shown in Fig. The design shown in Figures 2 to 4 consists in the additional introduction of a thermally conductive material in the form of a grid into the heat sink 1 before hydroforming. Such a grid improves heat transfer from the surface of the heat sink 1 toward the coolant. This design can be used for heat sinks 1 with a smooth inner surface as well as those with a structured inner surface. The material chosen is preferably the same as the material of the tube (of the heat sink 1).

[0029] In a fourth, in Fig. 5 and Fig. 6, the heat sink 1 is also formed in a central region 10 between the two end regions 11 with a flat surface and with a smaller thickness than the end regions 11. The difference from the previous embodiments is that at least parts of the central region 10 have a deformation 101. The locations where semiconductor packages 4 are provided are not deformed, so that they remain flat. The deformation 101 can be provided on one or both sides of the heat sink 1 and both in the central region 10 and at the end regions. The deformation 101 is produced during the formation of the heat sink 1 in the hydroforming process, and is therefore part of the shape of the tool used to form the shape of the heat sink 1.

[0030] The shape of the deformation 101 of the heat sink 1 depends, for example, on the components and the required cooling capacity of the heat sink 1 and can be determined in simulations and tests. Examples are shown in Fig. 5 and Fig. 6 On both sides of the heat sink 1, uniform elevations and depressions in a regular structure are provided at locations where no semiconductor packages 4 are attached. Uneven elevations and depressions may also be provided, as may an irregular structure or a combination thereof. As already mentioned, the deformation 101 shown is only an example. Structures other than those shown may be used to optimize the cooling performance. This design can be used with heat sinks 1 with a smooth inner surface as well as with those with a structured inner surface, and with or without a grid.

[0031] In all versions, the semiconductor packages 4 are attached to the heat sink 1 via one side of their housing, e.g. by soldering.

[0032] In one embodiment, the maximum width of heat sink 1 is smaller than the length of a housing (overmolding) of the semiconductor package, so that no heat sink is located below the power and signal / control contacts. This saves installation space.

[0033] The number of semiconductor packages 4 per heat sink 1 is fundamentally unlimited, since the heat sink 1 can be manufactured in any length. It can be provided that semiconductor packages 4 of each phase are arranged on a common heat sink 1. Several heat sinks 1 can be mechanically and fluidically connected to one another at end regions 11, e.g., by laser welding, so that a coolant can flow through all connected heat sinks 1.

[0034] Furthermore, any type of semiconductor package 4 can be mounted on a heat sink 1, as long as it has a suitable housing (overmolding) with a connection area. Any number of power semiconductors, e.g., two or four, can be provided within a semiconductor package 4.

[0035] Copper is the preferred material for the tube from which the heat sink 1 is made. However, another thermally conductive material that can be formed using hydroforming can also be used. For example, aluminum would be another suitable material.

[0036] By manufacturing the heat sink 1 using hydroforming, a faster and simpler manufacturing process for the heat sink 1 is possible. Furthermore, the heat sink 1 is lighter than a previously used base plate 2 with associated cooling structure 3 and housing, thus requiring less installation space. Multiple heat sinks 1 can also be easily connected to one another, e.g., by laser welding, so that they can use a common cooling circuit. Hydroforming allows for a very thin wall thickness of, for example, 1 mm, to be achieved, which both saves weight and increases cooling performance by improving heat transfer into the coolant.

[0037] The proposed cooling arrangement is advantageously used in an inverter of power electronics, which is preferably used in an electric drive of a vehicle having a three-phase electric motor and a storage battery. The power electronics comprises a multi-phase inverter and is connected to the electric motor and storage battery in order to generate direct current from the storage battery into alternating current usable by the electric motor by means of the inverter in order to drive the electric motor. To control the inverter, an ECU, i.e., an electronic control unit, is provided as part of the power electronics. The ECU is connected to the electric motor for its control and regulation, and to the inverter. The electric motor is, in particular, an electric axle drive.

[0038] A vehicle, e.g. a passenger car or a commercial vehicle, advantageously has at least one such drive. The vehicle is in particular a commercial vehicle such as a truck or a bus, or a passenger car. The power electronics module (i.e. the power electronics) comprises a DC / AC inverter with the described structure. It can also comprise or be a part of an AC / DC rectifier, a DC / DC converter, a transformer and / or another electrical converter or a part of such a converter. In particular, the power electronics module serves to supply current to an electric machine, e.g. an electric motor and / or a generator. List of reference symbols 1 heat sink 10 middle range 101 Deformation 11 End area 2 base plate 3 cooling structures 4 Semiconductor package 5 housings

Claims

[1] Heat sink (1) for power semiconductors arranged in a semiconductor package (4), wherein the heat sink (1) is formed by a tube made of thermally conductive material being brought into a predetermined shape by means of a hydroforming process, which tube has two end regions (11) and a central, flat region (10) located between the end regions, which is formed on one or both sides at least partially for fastening semiconductor packages (4). [2] Heat sink (1) according to claim 1, wherein the tube from which the heat sink (1) is formed has a predetermined structure on its inner surface. [3] Heat sink (1) according to claim 1 or 2, wherein a grid of thermally conductive material is introduced into the tube before carrying out the hydroforming process. [4] Heat sink (1) according to one of the preceding claims, wherein the central region (10) of the heat sink (1) has a deformation (101) at at least one location which is not formed for fastening semiconductor packages (4). [5] Heat sink (1) according to claim 4, wherein the deformation (101) is provided on one or both sides of the heat sink (1). [6] Heat sink (1) according to claim 4 or 5, wherein the deformation (101) is formed as uniform or uneven elevations and depressions in a regular or irregular structure. [7] Heat sink (1) according to one of the preceding claims, wherein a thickness of the central region (10) is less than a thickness of the end regions (11). [8] Cooling arrangement, comprising - at least one semiconductor package (4) with power semiconductors to be cooled arranged therein, and - at least one heat sink (1) according to one of the preceding claims, wherein at least one semiconductor package (4) is attached to a location of the central, flat region (10). [9] Cooling arrangement according to claim 8, wherein a plurality of heat sinks are connected to one another at each end region (11) thereof. [10] Electronic module comprising an inverter with a cooling arrangement according to claim 8 or 9.

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