Power module having at least one power cell

Abstract

The invention relates to a power module (2) having at least one power unit (4), comprising at least one power semiconductor (6) and a substrate (8). In order to improve the reliability of the power module (2) it is proposed that the substrate (8) of the power unit (4) is materially bonded to a surface (10) of a cooling body (12), wherein the at least one power unit (4) is at least partially surrounded by a housing (14), wherein the housing (14) comprises a housing frame (16) made of a first dielectric material and a housing cover (18) made of a second dielectric material, wherein the first dielectric material is different from the second dielectric material, and wherein the housing frame (16) is liquid-tightly connected to the surface (10) of the cooling body (12), and wherein the housing (14) is closed by the connection of the housing cover (18) to the housing frame (16).

Description

Technical Field

[0001] The present invention relates to a power module having at least one power unit.

[0002] Furthermore, the present invention relates to a power converter having at least one such power module.

[0003] Furthermore, the present invention relates to a method for manufacturing a power module having at least one power unit. Background Technology

[0004] In such power converters, closed-loop switching modules, currently manufactured in a discrete manner, are typically screwed onto a cooling body via a solid metal base plate. A power converter should be understood, for example, as a rectifier, inverter, converter, or DC-DC voltage converter.

[0005] In such switching modules, the periphery surrounding the power semiconductor becomes increasingly hot due to the increase in the maximum permissible chip temperature (which is, for example, in the range of 175°C). This particularly affects the housing surrounding the power semiconductor, which is typically made of plastic. Therefore, the rising temperature within the switching module also poses a challenge to the housing surrounding the power semiconductor. Using high-temperature resistant plastics (such as PPS) also has other drawbacks. These high-temperature resistant plastics, for example, have a high proportion of glass fiber, which makes the material brittle, especially under mechanical stress, leading to cracking and eventual breakage. Summary of the Invention

[0006] Against this backdrop, the purpose of this invention is to improve the reliability of power modules.

[0007] According to the invention, this objective is achieved by a power module having at least one power unit, the power module comprising at least one power semiconductor and a substrate, the substrate of the power unit being directly connected to a surface material of a cooling body, wherein at least one power unit is at least partially surrounded by a housing, wherein the housing comprises a housing frame made of a first dielectric material and a housing cover made of a second dielectric material, wherein the first dielectric material is different from the second dielectric material, wherein the housing frame is liquid-tightly connected to the surface of the cooling body, and wherein the housing is closed by connecting the housing cover to the housing frame.

[0008] Furthermore, according to the present invention, this objective is achieved by a power converter having at least one such power module.

[0009] Furthermore, according to the present invention, this objective is achieved by a method for producing a power module having at least one power unit, the power unit comprising at least one power semiconductor and a substrate, wherein the substrate of the power unit is directly connected to a surface material of a cooling body, wherein a housing is arranged around the at least one power unit, wherein the housing comprises a housing frame made of a first dielectric material and a housing cover made of a second dielectric material, wherein the first dielectric material is different from the second dielectric material, wherein the housing frame is liquid-tightly connected to the surface of the cooling body, and wherein the housing is closed by connecting the housing to the housing frame.

[0010] The advantages and preferred design schemes of the power modules listed below can be similarly transferred to power converters and methods.

[0011] This invention is based on the idea of ​​improving the reliability of power modules through a housing, which at least partially surrounds the power unit of the power module. The power unit has at least one power semiconductor and a substrate. The substrate has a dielectric material layer with metallization (particularly on both sides). For example, the dielectric material layer is 25 μm to 400 μm thick, particularly 50 μm to 250 μm, and comprises a ceramic material (e.g., aluminum nitride or alumina) or an organic material (e.g., polyamide). The metallization is made of copper, for example.

[0012] The substrate is directly mated to the surface material of the cooling body. The cooling body should be understood as a metal base plate, which may have cooling ribs or other components to increase the surface area. The cooling body is made of aluminum or an aluminum alloy, for example, by extrusion. Direct material mating connection should be understood as a direct connection, which includes connecting devices for creating the material mating connection (including, for example, adhesives, solder, sintering paste, etc.), but does not include additional connecting elements (e.g., additional conductors, bonding wires, spacers, base plates, thermal paste, etc.).

[0013] The housing includes a housing frame and a housing cover, wherein the housing is sealed by connecting the housing cover to the housing frame. The housing frame is liquid-tightly connected to the surface of the coolant, allowing, for example, flexible packages, particularly silicone packages, to be disposed within the housing frame to protect the power semiconductor. A liquid-tight connection can be achieved, for example, through force-fit or form-fit adhesive bonding. By connecting the housing frame to the coolant, the thermal load on the housing is reduced, even at high temperatures (e.g., in the range of 175°C) for the power semiconductor.

[0014] The housing frame is made of a first dielectric material, while the housing cover is made of a second dielectric material, wherein the first dielectric material differs from the second dielectric material. Specifically, the first dielectric material differs from the second dielectric material in its mechanical, electrical, and thermal properties. By using different dielectric materials for the housing frame and housing cover, a great deal of freedom is provided to optimize the mechanical, electrical, and thermal properties of the housing, thereby improving the reliability of the power module. In particular, the use of different dielectric materials enables the realization of a housing that does not significantly impair the lifespan of the power module even under the high temperatures of power semiconductors.

[0015] Another embodiment proposes a detachable connection between the housing cover and the housing frame. This reversible connection can be achieved, for example, via a force-fit connection between the housing cover and the housing frame. Since the housing cover can be removed from the housing frame, non-destructive analysis of the power unit is possible (e.g., in the event of errors during production or operation).

[0016] Another embodiment proposes that the housing cover and housing frame are form-fitted together. The form-fitting connection is, for example, a snap-fit ​​connection of the housing cover. The snap-fit ​​connection can be created, for example, via the housing cover, which is elastically deformable at least in the area of ​​the snap-fit ​​connection and hooks into the housing frame to create the snap-fit ​​connection. With a form-fitted connected cover, the power unit can be analyzed particularly simply and non-destructively (e.g., in the event of errors during production or operation).

[0017] Another embodiment proposes that the first dielectric material has higher dielectric strength and / or higher temperature stability than the second dielectric material. Since the housing cover is not in direct contact with the coolant heated by the power semiconductor and is therefore at a lower temperature than the housing frame, lower temperature stability is sufficient. Especially when a soft package is used within the housing frame, the housing cover can have a lower dielectric strength than the housing frame. Therefore, cheaper materials can be used for the housing cover.

[0018] Another embodiment proposes that the first dielectric material has higher mechanical stiffness than the second dielectric material. For example, a housing cover including the second dielectric material can elastically deform due to its lower mechanical stiffness to create a snap-fit ​​connection with the housing frame.

[0019] Another embodiment proposes that the first dielectric material comprises a reactive resin and / or has a fiber content of 50% to 75%, particularly 60% to 65%. The reactive resin is, for example, an epoxy resin. For example, glass and / or carbon fibers are used as fillers, thereby achieving high strength and / or stiffness. Furthermore, the first dielectric material achieves high dielectric strength.

[0020] Another embodiment proposes that the second dielectric material comprises a thermoplastic material and / or has a fiber content of 5% to 15%. This thermoplastic material is, for example, polycarbonate. Glass and / or carbon fibers are used as fillers, for example. This proportion of fibers achieves high elasticity in the second dielectric material, for example, for creating snap-fit ​​connections.

[0021] Another embodiment proposes that a power distribution board, arranged substantially parallel to the surface of the cooling body, is connected to the power unit via vertical contacts, wherein the housing cover has openings for the vertical contacts to pass through. The vertical contacts should be understood, for example, as pins, which, due to their structural characteristics, can be arranged vertically on the substrate. Such structural characteristics are, for example, feet that allow pins to be arranged on the substrate (e.g., through connections that mate with the substrate material), and / or oscillating circles, which make it easier to find holes in the power distribution board and provide greater stability and robustness (e.g., in the event of thermal expansion during operation). For example, the vertical contacts are soldered to the substrate and connected to the power distribution board by means of a press-fit connection. Such contacts are made, for example, of copper or a copper alloy to achieve low resistance and high current carrying capacity. The vertical arrangement of the contacts results in short cable paths and associated low inductance, which enables power units with low impedance and low losses.

[0022] Another embodiment proposes that the switchboard has a metallized portion, wherein the metallized portion is at least partially left open. In particular, the metallized portion between the potentials of different vertical contacts is left open in order to maintain the required air and creepage distances. Attached Figure Description

[0023] The present invention will now be described and explained in more detail with reference to the embodiments shown in the accompanying drawings.

[0024] The diagram shows:

[0025] Figure 1 A cross-sectional schematic diagram of the power module is shown.

[0026] Figure 2 A schematic three-dimensional cross-sectional view of the power module is shown.

[0027] Figure 3 A schematic 3D diagram of the power module is shown, and

[0028] Figure 4 A schematic diagram of a power converter with a power module is shown. Detailed Implementation

[0029] The embodiments described below are preferred embodiments of the present invention. In the embodiments, the components of the described embodiments each represent independent features of the present invention, which are considered independently of each other, and which also independently improve the present invention, and are therefore considered as part of the present invention individually or in combinations other than those shown. Furthermore, the described embodiments can also be supplemented by other features of the present invention already described.

[0030] The same reference numerals have the same meaning in all figures.

[0031] Figure 1 A schematic diagram of power module 2 is shown in cross-section. Power module 2 has at least one power unit 4, which includes a power semiconductor 6 and a substrate 8. The power semiconductor 6 is implemented, for example, as a transistor, particularly an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a field-effect transistor, or a diode. In particular, at least one transistor is provided with an anti-parallel diode.

[0032] At least one power unit 4 has a substrate 8 with a dielectric material layer of 25 μm to 400 μm thickness, particularly 50 μm to 250 μm, comprising a ceramic material (e.g., aluminum nitride or alumina) or an organic material (e.g., polyamide). Furthermore, the substrate 8 has metallized portions on both sides, particularly structured metallized portions, made of, for example, copper, wherein the substrate 8 is directly material-fitted to the surface 10 of the coolant 12 via the metallized portions. The coolant 12 is made of aluminum or an aluminum alloy, for example, by extrusion. The material-fitted connection with the coolant 12 is achieved by welding or sintering. A direct material-fitted connection should be understood as a direct connection, which includes connecting means for creating the material-fitted connection (including, for example, adhesives, solder, sintering paste, etc.), but excludes additional connecting elements (e.g., additional conductors, bonding wires, spacers, base plates, thermal paste, etc.).

[0033] At least one power unit 4 is surrounded by a housing 14, wherein the housing 14 has a housing frame 16 made of a first dielectric material and a housing cover 18 made of a second dielectric material, wherein the housing 14 is closed by connecting the housing cover 18 to the housing frame 16. Furthermore, the housing cover 18 is detachably connected to the housing frame 16 via a protrusion 16a. The housing frame 16 is liquid-tightly connected to the surface 10 of the coolant 12. The housing 14 is filled with a flexible encapsulation 20, particularly a silicone encapsulation, just below the housing cover 18.

[0034] The first dielectric material differs from the second dielectric material in that it has higher dielectric strength and / or higher temperature stability. Furthermore, the first dielectric material has higher mechanical stiffness than the second dielectric material.

[0035] For example, the first dielectric material comprises a reactive resin, particularly an epoxy resin, which is filled with 50% to 75%, particularly 60% to 65%, of fiber content. On the other hand, the second dielectric material comprises, for example, a thermoplastic filled with 5% to 15% of fiber content. For example, glass and / or carbon fibers are used as fillers.

[0036] A power distribution plate 22, extending substantially parallel to the surface 10 of the cooling body 12, is connected to the power unit 4 via vertical contact portions 24, wherein the vertical contact portions 24 are material-fitted to the substrate 8 of the power unit 4. The vertical contact portions 24 have elastically yielding sections 26 and are connected to the power distribution plate 22, for example, by a press-fit connection 28. The power distribution plate 22 has metallized portions 30, particularly on both sides, wherein the metallized portions 30 are at least partially open to maintain the required air gaps and creepage distances on the power distribution plate 22. Specifically, the metallized portions 30 are left open between the potentials of the different vertical contact portions 24 to maintain necessary clearances and creepage distances. The housing cover 18 has openings 32 for the insertion of orthogonal contacts 24.

[0037] Figure 2 A schematic three-dimensional cross-sectional view of the power module 2 is shown. The power module 2 includes at least two power units 4. The housing cover 18 of the corresponding power unit 4 is detachably connected to the housing frame 16 via a snap-fit ​​connection 34. The snap-fit ​​connection is created, for example, via a housing cover 18 that is elastically deformable at least in the area of ​​the snap-fit ​​connection, which hooks into the housing frame 16 on at least two opposite sides to create the snap-fit ​​connection. In particular, the lugs 18a of the housing cover 18 hook into the recesses 16b in the housing frame 16. For clarity, the power distribution board 22 is not shown. Figure 2 Another implementation scheme for the medium power module 2 corresponds to Figure 1 The implementation plan in the document.

[0038] Figure 3 A schematic three-dimensional view of the power module 2 is shown, in which the elastic region 18b of the housing cover 18 is shown, which is used to establish a detachable form-fit connection with the housing frame 16. Figure 3 The design scheme of power module 2 in the middle corresponds to Figure 2 The design scheme in the middle.

[0039] Figure 4 A schematic diagram of a power converter 36 having a power module 2 is shown. The power converter 36 may include more than one power module 2.

[0040] In summary, the present invention relates to a power module 2 having at least one power unit 4, the power unit comprising at least one power semiconductor 6 and a substrate 8. To improve the reliability of the power module 2, the substrate 8 of the power unit 4 is directly and materially connected to the surface 10 of a cooling body 12, wherein at least one power unit 4 is at least partially surrounded by a housing 14, wherein the housing 14 has a housing frame 16 made of a first dielectric material and a housing cover 18 made of a second dielectric material, wherein the first dielectric material is different from the second dielectric material, and wherein the housing frame 16 is liquid-tightly connected to the surface 10 of the cooling body 12, and wherein the housing 14 is closed by connecting the housing cover 18 to the housing frame 16.

Claims

1. A power module (2) having at least one power unit (4), the power unit comprising at least one power semiconductor (6) and a substrate (8). in, The substrate (8) of the power unit (4) is directly connected to the surface (10) of the cooling body (12) in a material-matching manner. In this embodiment, at least one of the power units (4) is at least partially surrounded by the housing (14). The housing (14) includes a housing frame (16) made of a first dielectric material and a housing cover (18) made of a second dielectric material. Wherein, the first dielectric material is different from the second dielectric material, and The housing frame (16) is liquid-tightly connected to the surface (10) of the cooling body (12), and The housing (14) is closed by connecting the housing cover (18) to the housing frame (16). The first dielectric material has higher dielectric strength and / or higher temperature stability compared to the second dielectric material.

2. A power module (2) having at least one power unit (4), the power unit comprising at least one power semiconductor (6) and a substrate (8). in, The substrate (8) of the power unit (4) is directly connected to the surface (10) of the cooling body (12) in a material-matching manner. In this embodiment, at least one of the power units (4) is at least partially surrounded by the housing (14). The housing (14) includes a housing frame (16) made of a first dielectric material and a housing cover (18) made of a second dielectric material. Wherein, the first dielectric material is different from the second dielectric material, and The housing frame (16) is liquid-tightly connected to the surface (10) of the cooling body (12), and The housing (14) is closed by connecting the housing cover (18) to the housing frame (16). The first dielectric material has higher mechanical stiffness compared to the second dielectric material.

3. The power module (2) according to claim 1 or 2, wherein, The housing cover (18) is detachably connected to the housing frame (16).

4. The power module (2) according to claim 1 or 2, wherein, The housing cover (18) is shaped to fit the housing frame (16).

5. The power module (2) according to claim 1 or 2, wherein, The first dielectric material comprises a reactive resin, and / or the first dielectric material has a fiber content of 50% to 75%.

6. The power module (2) according to claim 5, wherein, The first dielectric material has a fiber content of 60% to 65%.

7. The power module (2) according to claim 1 or 2, wherein, The second dielectric material comprises a thermoplastic material and / or the second dielectric material has a fiber content of 5% to 15%.

8. The power module (2) according to claim 1 or 2, wherein, A power distribution board (22), which extends parallel to the surface (10) of the cooling body (12), is connected to the power unit (4) via a vertical contact (24). The housing cover (18) has a recess (32) for the vertical contact portion (24) to pass through.

9. The power module (2) according to claim 8, wherein, The power distribution board (22) has a metallized section (30), wherein the metallized section (30) is at least partially empty.

10. A power converter having at least one power module (2) according to any one of claims 1 to 9.

11. A method for producing a power module (2) having at least one power unit (4), The power unit includes at least one power semiconductor (6) and a substrate (8). in, The substrate (8) of the power unit (4) is directly connected to the surface (10) of the cooling body (12) in a material-matching manner. The housing (14) is arranged around the at least one power unit (4). The housing (14) includes a housing frame (16) made of a first dielectric material and a housing cover (18) made of a second dielectric material. The first dielectric material is different from the second dielectric material. The housing frame (16) is liquid-tightly connected to the surface (10) of the cooling body (12), and The housing (14) is closed by connecting the housing cover (18) to the housing frame (16). The first dielectric material has higher dielectric strength and / or higher temperature stability compared to the second dielectric material.

12. A method for producing a power module (2) having at least one power unit (4), The power unit includes at least one power semiconductor (6) and a substrate (8). in, The substrate (8) of the power unit (4) is directly connected to the surface (10) of the cooling body (12) in a material-matching manner. The housing (14) is arranged around the at least one power unit (4). The housing (14) includes a housing frame (16) made of a first dielectric material and a housing cover (18) made of a second dielectric material. The first dielectric material is different from the second dielectric material. The housing frame (16) is liquid-tightly connected to the surface (10) of the cooling body (12), and The housing (14) is closed by connecting the housing cover (18) to the housing frame (16). The first dielectric material has higher mechanical stiffness compared to the second dielectric material.

13. The method according to claim 11 or 12, wherein, The housing cover (18) is shaped to fit the housing frame (16).

14. The method according to claim 11 or 12, wherein, The housing cover (18) is detachably connected to the housing frame (16).

15. The method according to claim 11 or 12, in, A power distribution board (22), which extends parallel to the surface (10) of the cooling body (12), is connected to the power unit (4) via a vertical contact (24). The housing cover (18) has a recess (32) for the vertical contact portion (24) to pass through.

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