Power module and method for manufacturing a power module

Abstract

The invention relates to a power module having at least two busbars (1) running parallel to one another, the busbars (1) being separated from one another by an insulating film (2) which is applied in a planar manner along a longitudinal extension (L) of the busbars (1), and the busbars (1) being encapsulated in an encapsulation (3) by means of an insulating injection molding material, wherein the insulating film (2) has an overhang (4) in the longitudinal extension (L), which overhang forms a fused connection with the injection molding material of the injection molding encapsulation (3) in the region of overlap.

Description

Technical Field

[0001] The invention relates to a power module having a carrier substrate and at least a first power semiconductor component and a second power semiconductor component as well as a busbar.

[0002] The invention furthermore relates to a method for producing a power module having an overmolded busbar. Background Art

[0003] In the field of automotive electronics, especially in hybrid vehicles and electric vehicles, power modules with power semiconductor devices arranged on a substrate are increasingly used. Bonding technology is mainly used to make electrical contact between power semiconductor devices and printed conductors, such as direct copper bonding technology.

[0004] Such a power module can be used, for example, to supply power to an electric motor, such as a three-phase AC motor. In such applications, very high power losses and very high switching currents in the range of several hundred amperes can occur in the power module.

[0005] A power module comprising an electrically insulating carrier substrate is known from DE 10 2011 089 740 A1. The carrier substrate comprises a ceramic material or consists of a ceramic material. The power module comprises a first conductive conductor track arranged on a first surface of the carrier substrate and a second conductive conductor track also arranged on the first surface of the carrier substrate. In addition, the power module comprises at least one first power semiconductor component, the first power semiconductor component having at least one first interface and a second interface, wherein the first interface is arranged on a side of the first power semiconductor component facing the first conductor track, and the second interface is arranged on a side of the first power semiconductor component facing away from the first conductor track, and the first interface is electrically coupled to the first conductor track. In addition, the power module comprises at least one second power semiconductor component, the second power semiconductor component having at least one first interface and a second interface, wherein the first interface is arranged on a side of the second power semiconductor component facing the second conductor track, and the second interface is arranged on a side of the second power semiconductor component facing away from the second conductor track, and the first interface is electrically coupled to the second conductor track. The power module comprises an electrically conductive planar connection, which electrically couples the second interface of the first power semiconductor component to the second conductor track. The power module comprises an insulating layer and a third conductive printed conductor. The third printed conductor is arranged on a side of the insulating layer facing away from the carrier substrate. The second interface of the second power semiconductor device is electrically coupled to the third printed conductor. The insulating layer is constructed and arranged so that the insulating layer electrically insulates the third printed conductor from the first printed conductor and the second printed conductor. The first printed conductor and the third printed conductor are arranged at least partially overlapping in the direction of the vertical axis.

[0006] DE 10 2010 001 545 A1 discloses a molded power module, which essentially comprises a circuit carrier, which is designed, for example, as a DBC substrate, as a ceramic material, such as LTCC or a standard ceramic (such as Al2O2), or can also be designed as a stamped grid. Electronic components for representing the circuit are accommodated on such a circuit carrier. A plurality of electronic components, each arranged on the circuit carrier, are soldered, glued or also clamped and then embedded in a molding compound. Usually, the molding compound is injection molded around the components formed on the circuit carrier, so that on the one hand, the individual electronic components can be fixed and on the other hand, a sealing against environmental influences from the outside can be achieved.

[0007] CN 1 05 513 689 A discloses a planar electrical line whose conductors are separated by a substrate material. Summary of the invention

[0008] An object of the present invention is to realize a power module, which helps to improve the performance and / or reliability of the power module.

[0009] This object is achieved by the features of the independent claim. Advantageous developments of the invention are indicated in the dependent claims.

[0010] The object is achieved by means of a power module having at least two busbars extending parallel to one another, wherein the busbars are separated from one another by an insulating film, which is applied in a flat manner along the longitudinal extension of the busbars and is injection-molded in an injection-molded part by means of an insulating injection-molding material, wherein the insulating film has a projection extending in the longitudinal direction, which forms a fused connection with the injection-molding material of the injection-molded part in an overlapping area.

[0011] Such power modules are optimized with regard to their electrical properties and reduce the risk of inductively induced currents.

[0012] The power module saves construction space through the combination of insulating film and injection molding.

[0013] In one embodiment, an insulating film is inserted between the bus bars.

[0014] In a further embodiment, the insulating film is adhesively bonded between the busbars at least on one of the two busbars.

[0015] The insulating film has a projection extending in a transverse direction of the busbar and projecting beyond the end face of the busbar in the contact region.

[0016] The thickness of the insulating film is one twentieth to one tenth of the thickness of the injection-molded coating.

[0017] The object is also achieved by a method for producing a power module, wherein busbars and an insulating film arranged between the busbars are introduced into an injection molding tool, wherein the insulating film is held in the tool or at one of the busbars, and wherein the busbars are injection molded over and the insulating film is melt-bonded to the material of the injection molded coating. The insulating film can also consist of the same material as the injection molded coating.

[0018] In this case, the insulating film can be both mechanically held and partially bonded. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 shows a section through two busbars extending in parallel;

[0020] Figure 2 A view showing parallel busbars. DETAILED DESCRIPTION

[0021] The busbars 1 in a power module are usually mounted parallel to one another. The individual busbars 1 must be insulated from one another and also from other components of the power module.

[0022] In the known construction, the overmolded components, which are positioned at the smallest possible distance relative to one another, are insulated from one another by the injection molding material itself, which penetrates between the components, namely the busbars 1. In order to introduce the injection molding material between the busbars 1, a minimum distance between the busbars 1 is required, which is determined by the material and the injection molding process.

[0023] Typically, a distance is required here which corresponds approximately to the thickness of the injection-molded coating 3 of the busbar 1. Typical injection-molded coatings have a thickness d of several millimeters.

[0024] The problem here is that the busbars 1 are mounted with certain tolerances, so that the minimum spacing between the busbars 1 varies. It is therefore difficult to implement a defined spacing for injection molding.

[0025] According to the invention, an insulating film 2 is arranged between the busbars 1, which has a thickness that is small compared to the minimum distance, or the thickness of the injection-molded coating 3. Insulating films are known and have a thickness s of a few micrometers. The thickness s is therefore one twentieth to one tenth of the thickness d of the injection-molded coating 3.

[0026] The insulating film 2 consists of a material which is compatible with the material used for the injection molding and the resulting injection molding coating 3 and which can produce a fusion bond in the transition region.

[0027] For this purpose, the insulating film 2 is used in one embodiment as a separating component which is fixed in the tool during the injection molding process and effects the separation between the two busbars 1 .

[0028] In an alternative embodiment, the insulating film is at least partially coated with an adhesive, so that the film can be bonded to one of the busbars 1 before the busbars 1 are injection-molded around.

[0029] In a further alternative embodiment, one of the busbars 1 is thinly coated with an insulating layer.

[0030] Two parallel busbars 1 are encapsulated with an insulating film or an insulating layer with an injection molding material, regardless of the preparation. The insulating film 2 here protrudes beyond the two busbars. The overhang 4 is in the range of 1 mm to 5 mm and serves to fuse the insulating film 2 with the injection molding material in the region B in which the busbars are encapsulated with the injection molding material. The injection molding encapsulation 3 is thickened in the region B in order to simplify the fusion.

[0031] Busbars made of copper, aluminum or a copper alloy are used as flow-conducting components.

[0032] For the method for injection molding of busbars, an insulating film 2 is introduced into an injection molding tool. The insulating film is fixed in the tool at at least one location. This can be done by clamping the film or by gluing the film in the tool or alternatively on one of the busbars 1.

[0033] The adhesive used must not affect the properties of the injection molding material. The busbars are introduced into the tool toward the insulating film and extend on both sides of the insulating film 2. The tool is then closed and the injection molding coating 3 is produced.

[0034] exist Figure 2 In the view, the region in which the busbar is led out of the housing, that is, the injection-molded coating 3 with the injection-molded material, can be seen. At this location, the insulating film 2 has a projection 4 in the direction of the longitudinal extension L of the busbar 1, which projection is not melted, and a further projection 5 in the transverse extension Q. The projection 5, but also the part of the projection 4 that is not melted, is intended to prevent the formation of creepage paths between the current-carrying components.

Claims

1. A power module, comprising at least two busbars (1) extending parallel to each other, wherein the busbars (1) are separated from each other by an insulating film (2), the insulating film being applied in a planar manner along a longitudinal extension (L) of the busbars (1), and wherein the busbars are injection-molded in an injection-molded encapsulation (3) by means of an insulating injection-molding material, wherein the insulating film (2) has a protrusion (4) along the longitudinal extension (L), the protrusion forming a fused connection with the injection-molded material of the injection-molded encapsulation (3) in an overlapping region (B).

2. The power module according to claim 1, It is characterized in that The insulating film (2) is inserted between the bus bars (1).

3. The power module according to claim 1, It is characterized in that The insulating film (2) is bonded between the busbars (1) to at least one of the two busbars (1).

4. The power module according to any one of the preceding claims, It is characterized in that The insulating film (2) has a projection (5) extending along the transverse direction (Q) of the busbar, which projection extends beyond the end face (6) of the busbar (1) in the contact region.

5. The power module according to any one of the preceding claims, It is characterized in that The thickness (s) of the insulating film (2) is one twentieth to one tenth of the thickness (D) of the injection-molded coating (3).

6. A method for manufacturing a power module according to claims 1 to 5, wherein a busbar (1) and an insulating film (2) arranged between the busbars (1) are introduced into an injection molding tool, wherein the insulating film (2) is held in the tool or at one of the busbars (1), and wherein the busbar (1) is injection molded and the insulating film (2) is melt-connected to the material of the injection molded part (3) in an overlapping area (B).

7. The method according to claim 6, wherein the insulating film (2) is held mechanically.

8. The method according to claim 6, wherein the insulating film (2) is at least partially bonded by means of an adhesive.

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