Power semiconductor module, inverter

Abstract

Power semiconductor module (1) comprising at least one substrate (3) with a lower side (7) and an upper side (8) and a plurality of power semiconductor devices (2) arranged on the upper side (8) of the substrate (3), wherein the plurality of power semiconductor devices (2) and at least a part of the upper side (8) of the substrate (3) are embedded in a plastic housing (9), wherein the power semiconductor module (2) further comprises a stiffening structure (12, 13, 14) extending inside or on the plastic housing (9) in a main plane (20) parallel to the substrate (3) and extending over the cross-sectional area of the plastic housing (9).

Description

[0001] Specification

[0002] Power semiconductor module, Inverter

[0003] The present invention relates to a power semiconductor module comprising at least one substrate with a lower side and an upper side and a plurality of power semiconductor devices arranged on the upper side of the substrate, wherein the power semiconductor module comprises a plastic housing. Further, the invention relates to an inverter with the mentioned module.

[0004] Power semiconductor modules are subjected to large temperature fluctuations during the production process as well as in operation. In normal operation, semiconductor devices of a power semiconductor module, for example an inverter module, experience high losses. The heat produced in operation is dissipated mainly via the substrate and adjacent cooling structures, e.g. a liquid cooler.

[0005] Consequently, different parts of the power semiconductor module heat up differently. Furthermore, due to different materials and therefore different thermal expansion coefficients, different parts of the power semiconductor module react differently to an increase in temperature. Warpage and stress can occur as a consequence. Warpage of the module may damage electrical contacts and may furthermore damage the sealing of the plastic housing against external influences, in particular moist.

[0006] Furthermore, warpage may disrupt the close thermal contact between the substrate of a power semiconductor module and a cooling structure and thereby decrease the efficiency of the cooling.

[0007] It is therefore an object of the present invention to provide a power semiconductor module with a reduced risk of warpage during manufacturing and operation.

[0008] This object is achieved by means of the power semiconductor module according to claim 1.

[0009] Advantageous embodiments and developments are objects of the dependent claims. According to an aspect of the invention, a power semiconductor module is provided comprising at least one substrate with a lower side and an upper side and a plurality of power semiconductor devices arranged on the upper side of the substrate. The plurality of power semiconductor devices and at least a part of the upper side of the substrate are embedded in a plastic housing. The power semiconductor module further comprises a stiffening structure extending inside or on the plastic housing in a main plane parallel to the substrate and extending over the cross-sectional area of the plastic housing.

[0010] The stiffening structure provides the plastic housing with enough stiffness to withstand thermal stress and essentially prevent warping of the package. To achieve this, the stiffening structure extends inside or on the plastic housing in a main plane parallel to the substrate. By this it is understood that the stiffening structure extends essentially in a plane and that this plane is arranged parallel to the plane of the substrate. Elements of the stiffening structure may protrude from the plane. The stiffening structure is not necessarily planar, it may comprise curved parts or a bent edge region.

[0011] By the stiffening structure extending over the cross-sectional area of the plastic housing it is understood that the stiffening structure extends essentially over the whole cross-sectional area, i.e. a major part of about at least 70 percent, preferably at least 80 percent, of the plastic housing which may be essentially identical to the footprint of the substrate. Thus, the stiffening structure extends over the whole area that is significant for the occurrence of warpage and is able to prevent warpage.

[0012] The plastic housing can be formed solid and cavers the upper side of the substrate and the of power semiconductor devices arranged on the upper side of the substrate completely.

[0013] According to an aspect of the invention, the power semiconductor module is an inverter module and the plurality of power semiconductor devices comprise at least one high side semiconductor switch and at least one low side semiconductor switch. The semiconductor switches can in particular be SiC-MOSFETs. This semiconductor module may be suitable for use in an electrically driven vehicle, in particular to supply voltage to the electric engine.

[0014] This kind of power semiconductor module experiences particularly high thermal stress due to high losses. The risk of warpage is therefore comparatively large. At the same time, warpage is particularly disadvantageous, because it prevents effective cooling of the module. The power semiconductor module according to the invention has the advantage that warpage can be prevented or significantly reduced by the stiffening structure.

[0015] The stiffening structure may be formed of metal, for example copper. Alternatively or as in combination, it may be formed of fibreglass and / or carbon. A stiffening structure essentially formed of metal has the advantage that it can providing electromagnetic shielding as well as stiffening. This can be significant for applications where electromagnetic interference due to fast switching devices should be minimized.

[0016] In particular, the stiffening structure may be a grid, for example a grid formed of a metal like copper or a metal alloy like copper alloy, or a net, for example a net formed of fibreglass textile or carbon.

[0017] The stiffening structure can in particular have a thickness of a fraction of millimeters, e.g. 0.1 or 0.2 millimeters.

[0018] In particular, the stiffening structure is not an electrical component of the module or not a part of any electrical circuit of the module. More particularly, the stiffening structure is not electrically connected to any electrical components, like conductor layer or conductor track, of the module.

[0019] In particular, the stiffening structure is not a housing or a part of a housing or a cooler or a part of a cooler of the module.

[0020] According to an embodiment of the invention, the stiffening structure is fixed to the upper side of the plastic housing, for example by an adhesive layer. According to this embodiment, the stiffening structure may be a metal plate or a metal grid which is arranged on the upper side of the housing after the molding process. This has the advantage, that the placement of the stiffening structure is particularly easy.

[0021] According to an embodiment of the invention, the stiffening structure is fixed to the upper side of the substrate. According to this embodiment, the stiffening structure comprises an edge part protruding from the main plane and extending towards the substrate. The stiffening structure may be fixed to the upper side of the substrate by means of a fastening structure. Alternatively, the stiffening structure may be fixed to the upper side of the substrate by an adhesive.

[0022] If the stiffening structure is formed of a metal, an electrically insulating layer may be arranged between the upper side of the substrate and the stiffening structure.

[0023] According to an alternative embodiment of the invention, the stiffening structure is arranged floatingly in the plastic housing. According to this embodiment, the stiffening structure is not fixed to the substrate or the semiconductor devices, but completely embedded in and surrounded by the plastic material. During the molding process, the stiffening structure is held in position by the mold.

[0024] The substrate may in particular be a ceramic substrate, for example a DCB (direct copper bonded) substrate. A ceramic substrate is particularly well-suited for applications where considerable heat is generated and needs to be dissipated. Typically, heat is dissipated from the semiconductor devices into the layers of the substrate and absorbed by a cooling structure which is arranged in thermal contact with the lower side of the substrate.

[0025] According to an embodiment of the invention, the plastic housing can be formed by molding or overmolding of plastic on the upper side of the substrate.

[0026] According to another aspect of the invention, an inverter is provided comprising

[0027] - at least one above-described power semiconductor module, wherein the power semiconductor devices are formed as semiconductor switching elements, and

[0028] - a control circuit to control the at least one power semiconductor module, wherein the control circuit is connected to the power semiconductor devices by signal connenctions.

[0029] Further advantages, advantageous embodiments and the development of the power semiconductor module will become apparent from the exemplary embodiments which are described below in association with the schematic figures.

[0030] Figure 1 shows a cross-sectional view of a power semiconductor module according to a first embodiment of the invention,

[0031] Figure 2 shows a cross-sectional view of a power semiconductor module according to a second embodiment of the invention, Figure 3 shows a cross-sectional view of a power semiconductor module according to a third embodiment of the invention

[0032] Figure 4 shows a perspective view of the power semiconductor module according to figure 1 and

[0033] Figure 5 shows a detail of the power semiconductor module according to the first embodiment.

[0034] Figure 1 shows a power semiconductor module 1 comprising a plurality of power semiconductor devices 2. The power semiconductor devices 2 may in particular be SiC- MOSFETs arranged to function as high side and low side switches of an inverter.

[0035] The power semiconductor devices 2 are arranged on a substrate 3. The substrate 3 is a DCB substrate and comprises at least one layer 4 of copper, one ceramic layer 5 and a second layer 6 of copper, wherein the ceramic layer 5 is arranged between the two layers 4, 6 of copper.

[0036] The substrate 3 has a lower side 7 which to a large part forms the lower side 10 of the power semiconductor module 1 , and an upper side 8 on which the power semiconductor devices 2 are arranged.

[0037] On the upper side 8 of the substrate 3, a plastic housing 9 is arranged in which the power semiconductor devices 2 and the upper side 8 and even an edge part of the substrate 3 are embedded. The lower side 7 of the substrate 3 is exposed and not covered by the plastic housing 9. Thus, the lower side 7 of the substrate 3 may be brought into contact with a cooling structure. The plastic housing 9 has an upper side 11 which forms an upper side of the power semiconductor module 1 .

[0038] Inside the plastic housing 9, a stiffening structure 12 is arranged. The stiffening structure 12 according to this embodiment is formed as a metal grid and placed on the upper side 8 of the substrate 3 above the semiconductor devices 2. The stiffening structure 12 extends thus largely in a plane 20 parallel to the plane of the substrate 3 and is bent at the edges to contact the upper side 8 of the substrate 3. The stiffening structure 12 is placed on the substrate 3 before the molding process and is embedded in the plastic material. The stiffening structure 12 prevents warping of the power semiconductor module 1 . Furthermore, it provides electromagnetic shielding for the power semiconductor devices 2.

[0039] Figure 2 shows a second embodiment of the power semiconductor module 1 . This embodiment differs from the first embodiment shown in figure 1 in the form of the stiffening structure 13. According to the second embodiment, the stiffening structure 13 is a planar structure, for example a planar metal sheet or a planar metal net that is arranged floatingly the in the material of the plastic housing 9. Thus, it is not in contact with the substrate 3 but completely embedded in the plastic material. During production, the stiffening structure 13 may be held in position by the mold or a support structure which is withdrawn during the molding process.

[0040] According to an embodiment not shown in the figures, the stiffening structure 13 comprises a planar structure as shown in figure 2. However, according to this embodiment, the planar structure is not arranged floatingly in the plastic housing 9, but supported by plastic pins, which are arranged on the upper side 8 of the substrate 3 and provide mechanical support for the planar structure, but at the same time electrical insulation against the substrate 3.

[0041] Figure 3 shows a third embodiment of the power semiconductor module 1 which again differs in the form and the arrangement of the stiffening structure 14. According to the third embodiment, the stiffening structure 14 is a planar structure, for example a planar metal sheet or a planar metal grid, which is arranged on the upper side 11 of the plastic housing 9 by means of an adhesive layer 15.

[0042] Figure 4 shows a perspective view of the power semiconductor module 1 according to figure 1 . In the perspective view, the grid structure of the stiffening structure 12 is visible. At the edges, portions of the stiffening structure 12 are bent out of the plane 20 of the stiffening structure 12 towards the substrate 3. The stiffening structure 12 is fixed to the substrate 3 in contact regions 16.

[0043] Figure 5 shows a detailed view of a contact region 16. In the contact region 16, the stiffening structure 12 is fixed to the substrate 3 by means of an insulating layer 17. List of reference symbols

[0044] 1 power module

[0045] 2 power semiconductor chip

[0046] 3 substrate

[0047] 4 layer

[0048] 5 layer

[0049] 6 layer

[0050] 7 lower side

[0051] 8 upper side

[0052] 9 plastic housing

[0053] 10 lower side

[0054] 11 upper side

[0055] 12 stiffening structure

[0056] 13 stiffening structure

[0057] 14 stiffening structure

[0058] 15 adhesive layer

[0059] 16 contact region

[0060] 17 isolation

[0061] 20 plane

Claims

Claims1 . Power semiconductor module (1 ) comprising at least one substrate (3) with a lower side (7) and an upper side (8) and a plurality of power semiconductor devices (2) arranged on the upper side (8) of the substrate (3), wherein the plurality of power semiconductor devices (2) and at least a part of the upper side (8) of the substrate (3) are embedded in a plastic housing (9), wherein the power semiconductor module (2) further comprises a stiffening structure (12, 13, 14) extending inside or on the plastic housing (9) in a main plane (20) parallel to the substrate (3) and extending over the cross-sectional area of the plastic housing (9).

2. Power semiconductor module (1 ) according to claim 1 , wherein the power semiconductor module (1 ) is an inverter module and the plurality of power semiconductor devices (2) comprise at least one high-side semiconductor switch and at least one low side-semiconductor switch.

3. Power semiconductor module (1 ) according to claim 1 or 2, wherein the stiffening structure (12, 13, 14) is formed of metal.

4. Power semiconductor module (1 ) according to any of claims 1 to 3, wherein the stiffening structure (12, 13, 14) is formed of fibre glass.

5. Power semiconductor module (1 ) according to any of claims 1 to 4, wherein the stiffening structure (12, 13, 14) is formed of carbon.

6. Power semiconductor module (1 ) according to any of claims 1 to 5, wherein the stiffening structure (14) is fixed to the upper side (11 ) of the plastic housing (9).

7. Power semiconductor module (1 ) according to any of claims 1 to 6, wherein the stiffening structure (12) is fixed to the upper side (8) of the substrate (3).

8. Power semiconductor module (1 ) according to claim 7, wherein an insulating layer (17) is arranged between the upper side (8) of the substrate (3) and the stiffening structure (12).

9. Power semiconductor module (1 ) according to any of claims 1 to 5,wherein the stiffening structure (13) is arranged floatingly in the plastic housing (9).

10. Power semiconductor module (1 ) according to any of claims 1 to 9, wherein the substrate (3) is a ceramic substrate.11 . Power semiconductor module (1 ) according to any of claims 1 to 10, wherein the plastic housing (9) is formed by molding or overmolding of plastic on the upper side (8) of the substrate (3).

12. Power semiconductor module (1 ) according to any of claims 1 to 11 , wherein the lower side (10) of the power semiconductor module (1 ) is in contact with a cooling structure.

13. Power semiconductor module (1 ) according to any of claims 1 to 12, wherein the stiffening structure (13) is a grid, for example a grid formed of a metal like copper or a metal alloy like copper alloy, or is a net, for example a net formed of fibreglass textile or carbon.

14. Power semiconductor module (1 ) according to any of claims 1 to 13, wherein the stiffening structure (13) is not an electrical component of the module (1 ) or not a part of any electrical circuit of the module (1 ), or is not electrically connected to any electrical components of the module (1 ).

15. Power semiconductor module (1 ) according to any of claims 1 to 14, wherein the stiffening structure (13) is not a housing or a part of a housing or a cooler or a part of a cooler of the module (1 ).

16. Inverter, comprising- at least one power semiconductor module (1 ) according to any of claims 1 to 15, wherein the power semiconductor devices (2) are formed as semiconductor switching elements,- a control circuit to control the at least one power semiconductor module (1 ), wherein the control circuit is connected to the power semiconductor devices (2) by signal connenctions.

Images