POWER MODULE HAVING AT LEAST THREE POWER UNITS

Abstract

A power module includes at least two power units. Each power unit includes at least one power semiconductor and a substrate. In order to reduce the installation space required for the power module and to improve cooling, the at least one power semiconductor is connected, in particular in a materially bonded manner, to the substrate. The substrates of the at least two power units are each directly connected in a materially bonded manner to a surface of a common heat sink. A power converter having at least one power module is also disclosed.

Claims

1.-17. (canceled)

18. A power module, comprising: a heat sink configured to enable a gaseous coolant to flow in a direction of coolant flow substantially parallel to a surface of the heat sink, said heat sink comprising cooling ribs extending in the direction of coolant flow; at least three power units, each of the at least three power units comprising a substrate and a power semiconductor connected to the substrate, in particular in a materially bonded manner, with the substrates of the at least three power units being directly connected in a materially bonded manner to the surface of the common heat sink, said at least three power units arranged offset transversely to the direction of coolant flow; a power board arranged to run substantially parallel to the surface of the heat sink; and freely positionable contacts configured to connect the power board to the at least three power units.

19. The power module of claim 18, wherein the substrates of the power units include each a dielectric material layer with a thermal conductivity of at least 25 W.Math.m−1.Math.K−1, in particular at least 100 W.Math.m−1.Math.K−1, and a thickness d of 25 μm to 400 μm, in particular 50 μm to 250 μm.

20. The power module of claim 18, wherein the substrates include each a dielectric material layer with a thickness of 25 μm to 400 μm, in particular 50 μm to 250 μm.

21. The power module of claim 18, further comprising a common housing configured to accommodate at least two of the at least three power units.

22. The power module of claim 18, wherein at least two of the at least three power units are electrically conductively connected to one another, in particular by way of a bond connection.

23. The power module of claim 18, wherein the heat sink is made of a first metal material, with the surface having a cavity which is filled with a second metal material of a thermal conductivity which is higher than a thermal conductivity of the first metal material, said substrate being directly connected in a materially bonded manner to the second metal material.

24. The power module of claim 23, wherein the second metal material terminates substantially flush with the surface of the heat sink.

25. The power module of claim 23, wherein the surface of the heat sink includes three of said cavity filled with the second metal material, with the at least three power units being associated with the cavities in one-to-one correspondence.

26. The power module of claim 23, wherein the second metal material is introduced into the cavity using an additive method.

27. The power module of claim 18, wherein a spacing between the at least three power units varies in the direction of the coolant flow and/or transversely to the direction of the coolant flow.

28. The power module of claim 18, wherein a spacing between the at least three power units increases in the direction of the coolant flow.

29. The power module of claim 18, wherein the freely positionable contacts are connected to the substrates of the at least three power units in a materially bonded manner.

30. The power module of claim 18, wherein the freely positionable contacts are embodied asymmetrically in relation to a force centerline.

31. The power module of claim 18, wherein the freely positionable contacts have a wobble circle.

32. The power module of claim 18, wherein the freely positionable contacts have an elastically flexible section having an S-shaped spring form with a defined spring path, a foot, and a stop arranged parallel to the flexible section and spaced apart from the foot by a gap width, said foot configured for a materially bonded connection.

33. The power module of claim 18, wherein the heat sink is made of an aluminum alloy with a silicon content of up to 1.0%, in particular up to 0.6%, by extrusion pressing.

34. The power module claim 18, wherein the cooling ribs are arranged such that a ratio of a length of the cooling ribs to a spacing between the cooling ribs is at least 10.

35. The power module of claim 18, wherein the heat sink includes a baseplate with a substantially constant first thickness d1 of 3.5 mm to 5 mm, in particular 3.5 mm to 4 mm, with the baseplate and the cooling ribs of the heat sink being embodied in one piece.

36. A power converter, comprising a power module, said power module comprising a heat sink configured to enable a gaseous coolant to flow in a direction of coolant flow substantially parallel to a surface of the heat sink, said heat sink comprising cooling ribs extending in the direction of coolant flow, at least three power units, each of the at least three power units comprising a substrate and a power semiconductor connected to the substrate, in particular in a materially bonded manner, with the substrates of the at least three power units being directly connected in a materially bonded manner to the surface of the common heat sink, said at least three power units arranged offset transversely to the direction of coolant flow, a power board arranged to run substantially parallel to the surface of the heat sink, and freely positionable contacts configured to connect the power board to the at least three power units.

Description

[0040] The exemplary embodiments explained below are preferred forms of embodiment of the invention. In the exemplary embodiments the described components of the forms of embodiment in each case represent individual features of the invention, to be considered independently of one another, which also in each case develop the invention independently of one another and thus are also to be regarded as part of the invention individually or in a combination other than the one shown. Further, the described forms of embodiment can also be supplemented by further of the already described features of the invention.

[0041] The same reference characters have the same meaning in the different figures.

[0042] FIG. 1 shows a schematic representation of a first embodiment of a power module 2 in cross-section. By way of example, the power module 2 has two power units 4, which in each case comprise power semiconductors 6 and a substrate 8. The power semiconductors 6 are embodied as a transistor 10 or as a diode 12, wherein the transistor 10 is for example embodied as an insulated gate bipolar transistor (IGBT), as a metal oxide semiconductor field effect transistor (MOSFET) or as a field effect transistor. For example, each of the transistors 10 is assigned a diode 12, in particular an antiparallel diode 12.

[0043] The substrates 8 of both the power units 4 have a dielectric material layer 14 which contains a ceramic material, for example aluminum nitride or aluminum oxide, or an organic material, for example a polyimide. The dielectric material layer 14 has a thickness d of 25 μm to 400 μm, in particular 50 μm to 250 μm. In addition in each case the substrates 8 have an, in particular structured, upper metallization 18 on a side 16 facing the power semiconductors 6 and a lower metallization 22 on a side 20 facing away from the power semiconductors 6, wherein the substrates 8 in each case are directly connected in a materially bonded manner to a surface 24 of a common heat sink 26. The upper metallization 18 and the lower metallization 22 are for example made of copper. The materially bonded connection 28 to the heat sink 26 is produced by soldering or sintering. A directly materially bonded contact should be understood as a direct contact that includes connection means for producing the materially bonded connection such as adhesives, tin-solder, sinter compound, etc., but excludes an additional connection element such as an additional conductor, a bond wire, a spacer, a baseplate, heat transfer compound, etc. A side 30 of the power semiconductor 6 facing the substrate 8 is in each case likewise connected to the upper metallization 18 of the substrate 8 by way of a materially bonded connection 28 that is produced by soldering or sintering. A side 32 of the power semiconductors 6 facing away from the substrate 8 is in each case connected to the upper metallization 18 of the substrate 8 by way of a bond connection 34. The bond connection 34 for example comprises at least one bond wire, at least one ribbon bond and/or other means for producing a bond connection.

[0044] The transistors 10 in FIG. 1 are by way of example embodied as IGBTs, the collector contacts C of which are in each case connected to the upper metallization 18 of the substrate 8 by way of a materially bonded connection 28 on the side 30 of the power semiconductors 6 facing the substrate 8. The emitter contacts E of the transistors 10 embodied as IGBTs are, electrically insulated therefrom, connected to the upper metallization 18 of the substrate 8 by way of bond connections 34. The gate contacts of the transistors 10 and the bond connections of the diodes 12 are not represented in FIG. 1 for reasons of clarity.

[0045] A power board 36 arranged so as to run substantially parallel to the surface 24 of the heat sink 26 is connected to the power units 4 by way of freely positionable contacts 38, wherein the freely positionable contacts 38 are connected in a materially bonded manner to the upper metallizations 18 of the respective substrates 8 of the power units 4. The freely positionable contacts 38 have an elastically flexible section and are for example connected to the power board 36 by a press-fit connection.

[0046] The heat sink 26 is made of a first metal material 39. Cavities 40 are introduced on its surface 24 that are filled with a second metal material 42, wherein the second metal material 42 has a higher thermal conductivity than the first metal material 39. For example, the first metal material 39 is aluminum and the second metal material 42 is copper. Each of the at least two power units 4 is associated with a cavity 40 filled with the second metal material 42, wherein the second metal material 42 terminates substantially flush with the surface 24 of the heat sink 26 and the lower metallizations 22 of the respective substrate 8 are connected in a materially bonded manner to the second metal material 42. In particular, the second metal material 42 is Introduced into the cavities using an additive method, for example by means of cold gas spraying. Each of the power units 4 can be associated with a dedicated sensor, in particular a temperature sensor, in order to monitor the temperature of the power semiconductors 6.

[0047] FIG. 2 shows a schematic representation of a second embodiment of a power module 2 in a plan view. The heat sink 26 is configured, for example by cooling ribs, so that a gaseous coolant flows in a direction of coolant flow 44, wherein the direction of coolant flow 44 runs substantially parallel to the surface 24 of the heat sink 26. The gaseous coolant is for example air, which flows via a fan in the direction of coolant flow 44 over the cooling ribs of the heat sink 26. By way of example, the power module 2 has two power units 4, which are spaced apart on the surface 24 of the heat sink 26 such that thanks to heat splay an optimum cooling of the power semiconductors 6 takes place. Furthermore, the power units 4 have a rectangular base area with identical dimensions x, y. To achieve an optimum cooling of the power semiconductors 6 the power units 4, viewed transversely to the direction of coolant flow 44, are arranged offset by a first transverse offset x1. In addition, the power units 4, viewed in the direction of coolant flow 44, are spaced apart by a longitudinal offset y1 Because of the size of the surface 24 of the heat sink 26 the transverse offset x1 and the longitudinal offset y1 are smaller than the respective dimensions x, y of the power unit 4. Because the power units 4 are connected to the heat sink 26 in a materially bonded manner, fewer mounting points 46 are required. By way of example, each power unit 4 is associated with two mounting points 46, wherein the heat sink 26 has at least two mounting points 46, in particular at least four mounting points 46. The further embodiment of the power module 2 in FIG. 2 corresponds to the embodiment in FIG. 1.

[0048] FIG. 3 shows a schematic representation of a third embodiment of a power module 2 in a plan view, wherein the two power units 4 have a common housing 48. Both the power units 4 of the power module 2 are electrically conductively connected to one another by way of a bond connection 34, wherein the bond connection 34 has a plurality of bond wires, ribbon bonds and/or other means for producing the bond connection 34. For example, the housing 48 comprise a half-bridge circuit for high-current applications, wherein two half-bridges, which are each associated with a power unit 4, are connected in parallel, in order to drive a higher load current. The further embodiment of the power module 2 in FIG. 3 corresponds to the embodiment in FIG. 2.

[0049] FIG. 4 shows a schematic representation of a fourth embodiment of a power module 2 in a plan view, wherein the power module 2 comprises three power units 4. A spacing x1, x2, y1, y2 between the power units 4 varies in the direction of coolant flow 44 and transversely to the direction of coolant flow 44. In order to ensure a substantially even cooling of the power units 4, these are arranged such that the spacing y1, y2 between the power units 4 increases in the direction of coolant flow 44. The further embodiment of the power module 2 in FIG. 3 corresponds to the embodiment in FIG. 2.

[0050] FIG. 5 shows a schematic representation of a fifth embodiment of a power module 2 in a plan view, wherein besides the variation in the spacings x1, x2, y1, y2 between the power units 4 an additional heat splay is achieved thanks to a different arrangement of the components on the substrates 8. In particular, the power semiconductors 6 having the freely positionable contacts 38 are arranged on the respective substrates such that an optimum cooling of the power semiconductors 4 takes place. The surface area of the respective substrates 8 can be varied for a larger heat splay. The further embodiment of the power module 2 in FIG. 5 corresponds to the embodiment in FIG. 4.

[0051] FIG. 6 shows a schematic three-dimensional representation of a sixth embodiment of a power module 2, wherein the power module 2 comprises three power units 4. The power units 4 in each case have a housing 48 having a housing cover 50, wherein the housing cover 50 is represented as transparent in the case of the foremost power unit 4. The heat sink has a baseplate 51 having cooling ribs 52 running in the direction of coolant flow 44, wherein the cooling ribs 52 are connected to the baseplate 51 and wherein the baseplate 51 and the cooling ribs 52 of the heat sink 26 are embodied in one piece. The baseplate 51 has a substantially constant first thickness d1 of 3.5 mm to 5 mm, in particular 3.5 mm to 4 mm, whereas the ribs have a second thickness d2 that is smaller than the first thickness d1 of the baseplate 51. By way of example, the cooling ribs 52 are arranged equidistantly transversely to the direction of coolant flow 44.

[0052] The heat sink 26 is produced by extrusion pressing from an aluminum alloy, which for example has a silicon content of 0.1% to 1.0% in particular of 0.1% to 0.6%. Furthermore, the cooling ribs 52 are arranged such that a ratio of a length l of the cooling ribs 52 to a spacing a between the cooling ribs 52 is at least 10: l/a≥10. The further embodiment of the power module 2 in FIG. 6 corresponds to the embodiment in FIG. 4.

[0053] FIG. 7 shows a three-dimensional representation of a freely positionable contact 38. The freely positionable contact 38 has a press-in zone 53 that can be connected to the power board 36 and is embodied asymmetrically in respect of a force centerline 54, wherein a press-in force can be introduced into the freely positionable contact 38 along the force centerline 54. Positioning aids 56 are attached in a central part 55 for the alignment of the freely positionable contact 38, for example in a solder jig. A lower part 58 of the freely positionable contact 38 is embodied as an asymmetrical relief section, which has an elastically flexible section 60 and a stop 62 arranged parallel thereto, wherein the stop is spaced apart from a foot 64 by way of a gap width s. The foot 64 is configured for a materially bonded connection, for example by soldering or sintering. In particular the freely positionable contact 38 is connected to the upper metallization 18 of a substrate 8 in a materially bonded manner by way of the foot 64. The elastically flexible section 60 has an S-shaped spring form with a defined spring path. It is therefore possible to absorb forces that are for example caused by jolting and occur in the relief section during the press-in process or during operation. In addition, thanks to the elasticity, tolerances can be compensated. In particular, a spring constant of the elastically flexible section 60 is produced by stamping with the help of a reduction in the cross-section. The further embodiment of the freely positionable contact 38 in FIG. 7 corresponds to the embodiment in FIG. 1.

[0054] FIG. 8 shows a schematic representation of a power converter 66 having a power module 2. The power converter 66 can comprise more than one power module 2.

[0055] In summary, the invention relates to a power module 2 having at least two power units 4, which in each case comprise at least one power semiconductor 6 and a substrate 8. In order to reduce the installation space required for the power module and to improve cooling it is proposed that the respective at least one power semiconductor 6 is connected, in particular in a materially bonded manner, to the respective substrate 8, wherein the substrates 8 of the at least two power units 4 are in each case directly connected in a materially bonded manner to a surface 24 of a common heat sink 26.