DEVICE FOR A POWER MODULE, ... AND METHOD FOR MANUFACTURING DEVICE FOR A POWER MODULE - Patent application

Abstract

According to one embodiment, an apparatus (100) for a power module comprises an electrically conductive contact area (A1) and a first connection element (1) and a second connection element (2) for electrically connecting the contact areas. The first connection element is rigidly joined to the contact area in a first joining area (11) and the second connection element is welded to the first connection element in a second joining area (12) by laser welding.

Description

[Technical field]

[0001] explanation The present disclosure relates to an apparatus for a power module, a power module, and a method for manufacturing an apparatus for a power module. Summary of the Invention [Problem to be solved by the invention]

[0002] It is an object to provide an improved arrangement for a power module, for example an arrangement having a reliable and space-saving electrical connection and / or an electrical connection for high currents. A further object is to provide a power module having such an arrangement and a method for manufacturing such an arrangement. [Means for solving the problem]

[0003] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to improved apparatus for power modules, improved power modules, and improved methods for manufacturing apparatus for power modules.

[0004] First, an apparatus for a power module is defined. According to one embodiment, an apparatus for a power module comprises an electrically conductive contact area and a first and a second connection element for electrically connecting the contact areas, the first connection element being rigidly joined to the contact area in a first joining area and the second connection element being welded to the first connection element in a second joining area by laser welding.

[0005] Typically, there is limited space in a power module for electrical connections. Furthermore, compact power modules, i.e. power modules with a small footprint, are less expensive and can exhibit improved electromagnetic behavior. This is especially due to the smaller substrate size and smaller parasitic inductances. However, a significant amount of space is usually required for the preparation of wire bond or ribbon bond connections, for example on the top contacts of the power semiconductor devices of the power module, or the top metallization of the substrate of the power module. Often, multiple parallel wire bond or ribbon bond connections are required to achieve significant current capabilities. Also, a large amount of space is required when multiple electrically parallel terminals are connected to the same metallization area of ​​the substrate to achieve sufficient current capabilities. The limited space also limits the number of connections and therefore the current capabilities.

[0006] The invention is based on the realization that a reduction in space consumption can be achieved by an arrangement of at least two connection elements, a first connection element that is firmly bonded to a contact area, such as a top metallization of a substrate or a contact area of ​​a power semiconductor device, and a second connection element that is bonded on the first connection element instead of being bonded to the same contact area adjacent to the first connection element. In this way, the space consumption required for the connection can be reduced by up to 50%. Moreover, in this way, the current capacity of the connection can be increased, especially when the available space is limited, since both the first and second connection elements can be used to transport current.

[0007] Nevertheless, it turns out that the quality of the electrical connection provided by two connection elements, with a first connection element bonded to the contact area and a second connection element bonded to the first connection element, depends on the joining method used. For example, if both connection elements are welded by ultrasonic welding, strong thermal and mechanical stresses are caused by vibrations. This can lead to damage to the bond between the contact area and the first connection element when the second connection element is welded to the first connection element. Moreover, metal particles are usually generated during ultrasonic welding and the amount of space for placing a joining tool such as a sonotrode is large.

[0008] To avoid these problems, laser welding is used to weld the second connection element specifically onto the first connection element. Since laser welding does not produce vibrations like ultrasonic welding, the bond between the contact area and the first connection element is not damaged because there is no mechanical shock.

[0009] The conductive contact area may include or be made of a metal such as Al or Cu or Ni or Au or Ag or an alloy thereof. The contact area is the surface to which the first connection element is bonded. For example, the contact area is a part of a substrate or a power semiconductor device, or a terminal for an external electrical connection.

[0010] The first and second connection elements are electrically conductive. Both may comprise or consist of a metal such as Cu or Al, Au, Ag or alloys thereof. Each connection element may be configured to carry a current of at least 1 A, or at least 10 A, or at least 100 A.

[0011] The first connection element is rigidly bonded to the contact area. "Rigidly bonded" and "materially bonded" are synonymous. For example, an end or terminal portion, respectively, of the first connection element is rigidly bonded to the contact area. Similarly, an end or terminal portion, respectively, of the second connection element may be laser welded to the first connection element.

[0012] In this specification and below, if an element is bonded to another element, this particularly means that these elements are directly bonded to each other. Two elements bonded to each other are also electrically connected to each other.

[0013] The first connection element is firmly joined to the contact area by one or more bonds, hereinafter also referred to as first bonds. The first bond area is defined as an area where one or more first bonds between the first connection element and the contact area are formed. Outside the first bond area, no bonds are formed between the first connection element and the contact area. For example, only one continuous first bond is formed between the contact area and the first connection element. Alternatively, multiple first bonds may be formed between the first connection element and the contact area.

[0014] Similarly, by laser welding, the second connection element is firmly joined to the first connection element by one or more bonds, hereinafter also referred to as second bonds. The second bonds are in particular formed by a laser weld spot or a plurality of overlapping laser weld spots, the spot diameter being defined by the laser beam diameter. The second joint area is defined as the area in which one or more second bonds between the second connection element and the first connection element are formed. For example, by laser welding, a plurality of second bonds are formed between the second connection element and the first connection element, the second bonds being spaced apart in pairs from each other.

[0015] A bond is understood here to be an area where a solid joint or material bond, respectively, between two elements is realized. In the case of welding, the bond is for example an area where the material melts. Between two bonds, there may be a contact between the two elements, but there is no solid joint / material bond.

[0016] The first and / or second bond areas may each have an extension parallel to the contact area of, for example, at least 1 mm, or at least 3 mm, and / or at most 10 mm, or at most 5 mm. In the case of only one bond defining the bond area, the area of ​​the bond is equal to the area of ​​the bond area. In the case of a bond area defined by several spaced bonds, the area of ​​each bond is smaller than the area of ​​the bond area assigned to it. For example, the area of ​​each bond is at most 25% or at most 10% of the area of ​​the bond area. By way of example, the extension of each bond is at most 2 mm, or at most 1 mm, or at most 0.5 mm.

[0017] In addition to the first and second connecting elements, the device may comprise one or more further connecting elements. In this case, the third connecting element is welded to the second connecting element in a corresponding joint area by laser welding. The optional fourth connecting element is welded to the third connecting element in a corresponding joint area by laser welding, and so on. In particular, each two connecting elements of the plurality of connecting elements are welded to each other by laser welding. All features disclosed herein in relation to the first and second connecting elements are correspondingly disclosed for the further connecting elements. For example, the joint area between each two connecting elements may overlap the contact area and / or overlap each other in a plan view of the contact area.

[0018] According to further embodiments, the second connecting element comprises one or more coatings. For example, the second connecting element comprises an anti-reflective coating on the top surface facing away from the first connecting element. The top surface is configured to face the impinging laser beam during laser welding, for example. The irradiation efficiency of the laser beam can be improved by the anti-reflective coating on the top surface. Alternatively or additionally, the second connecting element may comprise a coating made of a noble metal, for example silver or gold, or nickel, on the bottom surface facing the first connecting element. Such a coating can prevent oxidation and can improve the laser welding process. The complete connecting element can have such a coating.

[0019] Additionally or alternatively, the second connecting element can include one or more coatings. All features disclosed in relation to the coating of the second connecting element are also disclosed for the coating of the first connecting element.

[0020] According to a further embodiment, the first and second joint areas overlap each other at least partially, i.e. partially or completely, in a plan view of the contact area. The second connection element may be welded onto a joint leg of the first connection element. One or more second joints between the second connection element and the first connection element may at least partially overlap one or more first joints between the first connection element and the contact area when viewed in a plan view of the contact area. Alternatively, the second joints between the first connection element and the second connection element may be in a staggered configuration with the first joints between the contact area and the first connection element, such that in the plan view the first joints do not overlap the second joints. In a plan view of the contact area, the first and second joint areas or the respective joints overlap the contact area.

[0021] According to a further embodiment, the first connection element is welded to the contact area by ultrasonic welding. Alternatively, the first connection element is welded to the contact area by laser welding. The first connection element can also be soldered or sintered or firmly bonded to the contact area by any other suitable method, such as gluing.

[0022] Those skilled in the art can ascertain which joining method was used to join the two elements. For example, ultrasonic welding produces shear displacements and / or sonotrode marks in the elements and the joint. Laser welding produces small, well-defined joints (weld spots) or multiple overlapping dots that form, for example, a continuous welding beam (scribe line or area).

[0023] In the case of ultrasonic welding, for example, there is a single continuous bond. In the case of laser welding, for example, there are multiple pairs of spaced apart bonds.

[0024] According to a further embodiment, the second connecting element comprises a weld structure prepared for improved laser welding. Such a weld structure can be realized by one or more thinned areas, slots, grooves and / or recesses in the second connecting element. The weld structure may overlap, in a plan view of the contact area, the second joining area or the second joint between the first connecting element and the second connecting element, respectively. Alternatively or additionally, the complete part of the second connecting element overlapping the second joining area may be formed thinner than the body of the second connecting element. For example, the thickness range of the thinned area may be between 0.3 and 0.8 times the thickness of the body.

[0025] Such a particular structure can beneficially influence the laser welding process and contribute to a reduction in the required heating power or energy impact of the laser irradiation by the laser beam on the second connecting element and / or the structure below the second connecting element. The welding process is performed on such thinner parts, which results in a smaller amount of melted metal and reduced lateral heat dissipation, so that the laser energy required to achieve the laser welded joint can be reduced.

[0026] The implementation of holes or slots in the second connection element can allow direct irradiation of the interface between the first and second connection elements on the edges of the holes or slots, so that less metal needs to be melted to achieve the laser welded joint. Furthermore, lateral heat diffusion can be prevented or reduced by the holes, slots or grooves. To reduce lateral heat dissipation, the holes, slots or recesses can also be located outside the joining area.

[0027] According to a further embodiment, the first and second connection elements are stacked on top of each other, for example the first connection element and the second connection element extend substantially parallel to each other.

[0028] According to a further embodiment, the first and second connection elements electrically connect the contact region to a further contact region of the device, e.g., the contact region and the further contact region are electrically connected only via the connection elements.

[0029] The further contact region, like the contact region, may comprise or consist of a metal such as Al or Cu or Ni or Au or Ag or alloys thereof.

[0030] According to a further embodiment, the first connection element is firmly connected to the further contact area in the third bonding area. For example, the first connection element is firmly connected to the further contact area by ultrasonic welding or laser welding or soldering or sintering. The part of the first connection element firmly connected to the further contact area may be an end or a terminal part of the first connection element, respectively.

[0031] According to a further embodiment, the second connecting element is welded onto the first connecting element in the fourth joint area by laser welding. The part of the second connecting element welded to the first connecting element in the fourth joint area may be an end or a terminal part of the second connecting element, respectively.

[0032] The definitions of the first and second bond regions and all features disclosed in connection therewith apply equally to the third and fourth bond regions, and thus the third and fourth bond regions may also be defined by the areas where the corresponding bonds are formed.

[0033] According to a further embodiment, the third and fourth bonding regions or corresponding joints, respectively, at least partially overlap one another in a plan view of the further contact region, in particular, the third and fourth bonding regions at least partially overlap the further contact region in a plan view of the further contact region.

[0034] Furthermore, the first connection element may be firmly bonded to the third and / or fourth and / or fifth etc. contact areas. The second connection element may for example be laser welded to the first connection element in all these contact areas such that the corresponding bond areas overlap each other and / or the assigned contact areas in a plan view of the contact areas. The connections to the third and / or fourth and / or fifth etc. contact areas may be stitch connections.

[0035] According to a further embodiment, the contact area is formed by a top metallization of a substrate of the device. The substrate may be an insulated metal substrate (IMS) with an electrically insulating resin layer sandwiched between the top and bottom metallizations. Alternatively, the substrate may be a direct bonded copper (DBC) or direct bonded aluminum (DBA) substrate with active metal bracing or ceramic insulating sheets.

[0036] According to a further embodiment, the contact area is formed by a power semiconductor device, also called a power semiconductor chip of the device. The power semiconductor device may be a transistor, such as a MOSFET, MISFET, IGBT, JFET or HEMTS, or a thyristor, or a diode. For example, the contact area is formed by a top contact. The contact area may be electrically connected to or formed by a main or gate electrode of the power semiconductor device.

[0037] According to a further embodiment, the contact area is formed by a terminal of the device. In this specification, a terminal is understood as an element, for example of metal, typically Cu or a Cu alloy, configured for the external electrical connection of the device, i.e. to an external component of the device. The terminal is, for example, a lead frame or a bus bar of the device. The connection to the external component is, for example, reversible.

[0038] The terminals here are, for example, sheet-like rigid elements. Each terminal may comprise a body and at least one terminal leg. Between the body and the terminal leg, the terminal may be provided with a kink of, for example, 90°.

[0039] The terminal legs may each have a width of at least 1 mm and / or at most 15 mm. The thickness of the terminal legs is in each case, for example, at least 0.5 mm and / or at most 1.5 mm.

[0040] According to further embodiments, the further contact area is formed by a top metallization of a substrate of the device, or by a power semiconductor device of the device, or by a terminal of the device.

[0041] According to a further embodiment, the first and / or second connecting element are ribbons. The ribbons may each have a width of at least 1 mm and / or at most 15 mm. The ribbons may each have a thickness of at least 1 μm or at least 20 μm and / or at most 2 mm. The ribbons may each be flexible or bendable. The ribbons may be laser welded to each other at their joining legs.

[0042] According to a further embodiment, the first and / or second connection elements are terminals. The terminals are configured for an external electrical connection. The terminals may be laser welded together at their terminal legs.

[0043] According to a further embodiment, the connection areas or connection parts of the terminals are respectively spaced apart from one another. The connection areas or parts are areas or parts of the terminals provided for an external electrical connection. The connection areas / parts may be areas / parts of the terminals that are exposed in the unconnected state of the power module, for example from the module housing or body. The connection areas / parts can be used for the interconnection of the power modules. The connection areas / parts of the terminals may be spaced apart laterally and / or vertically. The laterally is understood in this specification to be a direction parallel to a main extension plane of the device or power module, respectively. The vertical direction is a direction perpendicular to said main extension plane. For example, the contact area and / or the further contact area extend parallel to a main extension plane of the device or power module, respectively.

[0044] According to a further embodiment, the first and / or second connecting elements are both clips. A clip is understood herein to be a rigid sheet-like structure. The clip is a pre-bent structure. For example, each clip comprises at least two clip legs or ends connected by a body of the clip. There may be a kink between the body and each clip leg. The clip legs may be configured to be welded to other elements. For example, the clip legs of the clip are laser welded to each other.

[0045] It is possible for the first and second connection elements to be of the same type, for example both being ribbons or clips or terminals. Alternatively, the first and second connection elements may be of different types, for example one being a ribbon and the other being a clip or terminal. Any other combination is also possible.

[0046] According to a further embodiment, one of the first and second connection elements is a main terminal. The main terminal is arranged for supplying or outputting a current or voltage to or from the power module. For example, the main terminal is configured to transport at least 1 A, or at least 10 A, or at least 100 A, or at least 600 A.

[0047] According to a further embodiment, the other of the first and second connection elements is an auxiliary terminal. The auxiliary terminal is configured to control the power semiconductor device, for example as a gate terminal or for current or voltage measurement. For example, the cross-sectional area of ​​the auxiliary terminal perpendicular to the direction of current flow is at most 50% or at most 10% of the cross-sectional area of ​​the main terminal.

[0048] According to a further embodiment, the second connection element is connected to the first connection element via a number of laser welded weld joints, which are the above-mentioned second joints. These weld joints are distributed over the second joint area and are spaced apart from each other in pairs. For example, in the area between two adjacent weld joints, the first connection element and the second connection element are not firmly joined. In a plan view of the contact area, the weld joints may have a circular or elongated shape. The distance between each two weld joints may be, for example, at least 1 μm or at least 50 μm and / or at most 100 μm.

[0049] The features disclosed for the second joint in the last paragraph are also disclosed for the first joint, in particular when the first connection element is welded to the contact area by laser welding.

[0050] Next, the power module is defined. According to one embodiment of the power module, the power module comprises an apparatus according to any of the embodiments described herein.

[0051] Since the power module comprises the apparatus described herein, all features disclosed for the apparatus are also disclosed for the power module, and vice versa.

[0052] According to a further embodiment of the power module, the power module comprises a housing of an electrically insulating material. The device may be at least partially embedded in the housing. The power module may further comprise one or more power semiconductor devices and one or more substrates, the power semiconductor devices being mounted as described above. Furthermore, the power module may comprise a base plate on which the substrate is mounted and configured for use as a heat sink. The power module may also comprise a main terminal and an auxiliary terminal.

[0053] The housing may be formed of a thermoplastic or thermosetting resin material, or may be filled with inorganic particles or fibers. For example, the housing may be formed at least in part by a resin body or by a resin frame filled with gel or epoxy. For example, the power semiconductor devices of the power module are embedded and encapsulated in the housing. The housing may be formed at least in part by a molding process, such as transfer molding or injection molding.

[0054] A power module may be a device incorporating and electrically and mechanically interconnecting multiple power semiconductor devices. A power module may be adapted to handle currents in excess of 10 A. A power module may be a low voltage module adapted to handle voltages below 1 kV, or a medium voltage module adapted to handle voltages between 1 kV and 10 kV.

[0055] The power module can be used, for example, in an electric converter that can rectify an AC voltage / current to a DC voltage / current that is supplied to a DC link or a battery, such as the battery of an electric vehicle. The power module can also be an inverter that generates an AC voltage / current from a DC voltage / current that is supplied to an electric motor, such as the motor of an electric vehicle. The inverter can also be used to change the frequency of the AC voltage / current to another frequency of AC voltage / current. The power module can be used in automotive applications such as electric cars, motorcycles, buses, off-road construction vehicles, trucks, charging stations or power plants or traction applications.

[0056] According to a further embodiment, the connection areas of the first and second connection elements are exposed and freely accessible in the disconnected configuration of the power module, in particular the connection areas are not covered by the housing, i.e. there is no housing.

[0057] Next, a method for manufacturing an apparatus for a power module is defined. For example, the method is used to manufacture an apparatus according to any one of the embodiments described herein. Thus, all features disclosed in relation to the apparatus are also disclosed in relation to the method and vice versa.

[0058] According to one embodiment of the method, a method for manufacturing a device for a power module comprises electrically and mechanically connecting a first connection element to a contact area at a first joining region by a joining process. In a further step, a second connection element is electrically and mechanically connected to the first connection element at a second joining region by laser welding.

[0059] For example, first a first connection element is bonded to the contact area, and then a second connection element is laser welded onto the first connection element. Laser welding can be performed using an IR laser or a green laser.

[0060] According to a further embodiment of the method, the first and second bonding regions are formed such that they at least partially overlap one another in a plan view of the contact region, in particular one or more second bonds between the first connecting element and the second connecting element may at least partially overlap one or more first bonds between the first connecting element and the contact region.

[0061] According to a further embodiment of the method, the laser parameters of the laser beam used for laser welding are given to beneficially influence the laser welding. The laser beam or the corresponding laser source used for laser welding can be configured to provide a laser power of 300 W to 3000 W. Alternatively or additionally, the laser beam or the laser source for laser welding can be configured to provide a travel speed of the laser beam of 1 mm / s to 200 mm / s guided along the upper surface of the second connecting element facing the impinging laser beam. The laser beam itself or the workpiece can be moved. Thus, the welding does not have to be performed only at one limited point, but the laser spot of the laser beam providing the welding process can be moved at the aforementioned speed to provide a welded joint over a predetermined area.

[0062] The laser beam can also be configured to oscillate at a predetermined frequency, so that the laser spot position can be oscillated or oscillated with a frequency of up to 2 kHz and / or an amplitude of up to 500 μm to advantageously influence the welding process, for example by preventing localized overheating.

[0063] Hereinafter, the power module device, the power module and the manufacturing method of the power module device will be described in more detail based on exemplary embodiments with reference to the drawings. The attached drawings are included to provide further understanding. In the drawings, elements of the same structure and / or function are given the same reference numerals. It should be understood that the embodiments shown in the drawings are exemplary representations and are not necessarily drawn to scale. Insofar as elements or components correspond to each other in terms of their functions in different drawings, their description will not be repeated in each of the following drawings. For clarity, elements may not be displayed with corresponding reference numerals in all drawings. [Brief description of the drawings]

[0064] [Figure 1] 1A-1D are cross-sectional views illustrating different exemplary embodiments of an apparatus for a power module. [Diagram 2] 1A-1D are cross-sectional views illustrating different exemplary embodiments of an apparatus for a power module. [Diagram 3] 1A-1D are cross-sectional views illustrating different exemplary embodiments of an apparatus for a power module. [Figure 4] 1A-1D are cross-sectional views illustrating different exemplary embodiments of an apparatus for a power module. [Diagram 5] 1A-1D are cross-sectional views illustrating different exemplary embodiments of an apparatus for a power module. [Figure 6] 6 is a plan view of the exemplary embodiment of FIG. 5. [Figure 7] FIG. 1 is a cross-sectional view of an exemplary embodiment of a power module. [Figure 8] FIG. 1 is a cross-sectional view of an exemplary embodiment of a power module. [Figure 9] FIG. 2 is a detailed view of an exemplary embodiment of a first and second bond region in plan view. [Figure 10] FIG. 2 is a detailed view of an exemplary embodiment of a first and second bond region in plan view. [Figure 11] 1 is a flow chart of an exemplary embodiment of a method for manufacturing an apparatus for a power module. [Figure 12] 4 shows a further exemplary embodiment of an apparatus for a power module. [Figure 13] 4 shows a further exemplary embodiment of an apparatus for a power module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] 1 shows a first exemplary embodiment of an apparatus 100 for a power module. The apparatus 100 comprises a substrate 4 having a top metallization 40, a bottom metallization 42 and an electrically insulating layer 41 sandwiched between the top metallization 40 and the bottom metallization 42. For example, the metallizations 40, 42 comprise Cu or Al or their corresponding alloys. The surface of the top metallization 40 facing away from the insulating layer 41 can be formed of a Ni, Au or Ag coating. The insulating layer 41 is formed, for example, of an electrically insulating polymer or ceramic.

[0066] The top metallization 40 comprises three different areas. In the middle area, a power semiconductor device 3, such as an IGBT or a MOSFET, is mounted and connected. On the top side of the power semiconductor module 3 facing away from the substrate 4, a contact area A1 of the power semiconductor device 3 is formed. The contact area A1 is formed by a main electrode 30, such as an emitter electrode or a source electrode or a collector electrode or a drain electrode of the power semiconductor device 3.

[0067] The first connection element 1 in the form of a ribbon is firmly bonded to the contact area A1. The area where the bond (first bond) between the first connection element 1 and the contact area A1 is formed is called the first bonding area 11. For example, the first connection element 1 is welded to the contact area A1 by ultrasonic welding. However, other bonding processes that produce a strong bond are also possible, such as laser welding, soldering, sintering, etc.

[0068] The second connection element 2, also realised by a ribbon, is welded by laser welding to the first connection element 1 in a second joint area 12. The second joint area 12 is again defined by a bond (second bond) formed between the first connection element 1 and the second connection element 2.

[0069] In a plan view of the contact area A1, the first bonding area 11 and the second bonding area 12 at least partially overlap each other. This plan view is shown, for example, in Fig. 9. As can be seen, the second bonding area 12 is defined by a plurality of laser welded joints (second bonding areas) 120 laterally spaced apart from each other. The first bonding area 11 is realized by a single continuous joint (first bonding area) 110 that overlaps each of the laser welded second bonding areas 120.

[0070] Alternatively, if the first connection element 1 is also welded to the contact area A1 by laser welding, there may be several laterally spaced apart first weld joints 110. These first weld joints 110 may at least partially overlap the second weld joints 120 in plan view or may be arranged in a staggered configuration with the second weld joints 120 without overlapping each other in plan view. This second case is shown in FIG.

[0071] Returning to FIG. 1, the first connection element 1 is further firmly bonded to the further contact area A2 in a third bonding area 13. The further contact area A2 is formed by a top metallization 40 of the substrate 4. Here too, the first connection element 1 may be firmly bonded to the further contact area A2 by ultrasonic welding or laser welding or soldering, etc. The second connection element 2 is laser welded onto the first connection element 1 in a fourth bonding area 14, which at least partially overlaps the third bonding area 13 in a plan view of the further contact area A2. The same may apply to the third bonding area 13 and the fourth bonding area 14 as described for the first and second bonding areas and in relation to FIGS. 9 and 10.

[0072] The two connection elements 1, 2 in Fig. 1 are stacked on top of each other and thus realize two parallel electrical connections between the contact area A1 and the further contact area A2. This type of stacked connection element saves space and, moreover, makes it possible to transmit higher currents than could be realized with a single connection element in the form of a ribbon, since fewer parallel connections are required.

[0073] 2 shows a second exemplary embodiment of the device 100. In this case, two substrates 4, each formed as in FIG. 1, are electrically connected by two stacked connection elements 1, 2. Here again, the first connection element 1 is a ribbon that is firmly bonded, for example by ultrasonic or laser welding, to a contact area A1 of the left substrate 4 and firmly bonded, for example by ultrasonic or laser welding, to a further contact area A2 of the right substrate 4. The two ends of the second connection element 2 are laser welded to the two ends of the first connection element 1.

[0074] 3 shows a third exemplary embodiment, where the two connection elements 1, 2 are electrically connected to the top metallization 40 of the substrate 4 and to the terminals 50 of the device 100, i.e. to the upper faces of its terminal legs. The terminals 50 are metal elements that may be arranged on or at least partially integrated into the housing element 5 of the device 100 and are configured for the external electrical connection of the device 100. With regard to the robust bonding in the bonding areas 11, 12, 13, 14, the same applies here as explained in connection with the last two embodiments.

[0075] 4 shows a fourth exemplary embodiment, in which a power semiconductor device 3 mounted on a substrate 4 is electrically connected to a terminal 50 by a first connection element 1 and a second connection element 2. Again, the strong bonds at the bonding areas 11, 12, 13, 14 are as described for the previous exemplary embodiment.

[0076] 5 shows a fifth exemplary embodiment, in which the connection elements 1, 2 are realized by terminals, which are rigid elements, for example lead frames or bus bars, each comprising a connection part 1a, 2a for an external electrical connection.

[0077] The terminals 1, 2 each comprise a terminal leg that is used for a strong joint. With regard to the strong joint between the welded joint of the first terminal 1 in the first joint area 11 and the second terminal 2 in the second joint area 12, the same applies as described in the previous exemplary embodiment.

[0078] 6 shows the exemplary embodiment of FIG. 5 in a plan view of the contact area A1. As can be seen, the connection portions 1a, 2a of the first terminal 1 and the second terminal 2 are laterally spaced apart from each other. The first terminal 1 is also wider than the second terminal 2. The first terminal 1 may be a main terminal of the device 100, and the second terminal 2 may be an auxiliary terminal of the device 100, for example for control or measurement purposes. The first bonding area 11 is, for example, larger than the second bonding area 12. The bonding areas 11, 12 partially overlap each other in a plan view of the contact area A1.

[0079] Also, as explained in relation to Figures 5 and 6, in the case of two terminals welded together overlapping each other, space can be saved.

[0080] Figure 7 shows in cross-section a first exemplary embodiment of a power module 1000. The power module 1000 comprises a base plate 7, for example made of metal or ceramic or a composite material such as aluminum silicon carbide or magnesium silicon carbide, on which the device 100 according to figure 3 is mounted. The base plate 7 is configured for use as a cooling or heat sink.

[0081] The power module 1000 comprises a housing 5, 6, which is partly formed by a housing element 5 in the form of a frame and / or cover, on which the terminals 50 are formed or in which the terminals 50 are partly embedded, and partly embedded by an encapsulation 6, which encapsulates the substrate 4 and the power semiconductor devices 3 as well as a part of the terminals 50. The frame 5 forms a cavity into which the encapsulation is filled. The encapsulation 6 is, for example, a gel or a mold. The ribbons 1, 2 are also encapsulated in the encapsulation 6.

[0082] A second exemplary embodiment of a power module 1000 is shown in Fig. 8. Here, the device 100 of Figs. 5 and 6 is mounted on a base plate 7, formed for example as that of Fig. 7. The power module 1000 further comprises a housing 6 in the form of an electrically insulating encapsulation. The encapsulation 6 is formed for example by transfer molding. The connection parts 1a, 2a of the terminals 1, 2 protrude from the encapsulation 6 and are therefore freely accessible for external electrical connection to external components of the power module 1000.

[0083] The power modules of Figures 7 and 8 may each comprise an apparatus according to Figures 1 to 6. In particular, the power modules may comprise several stacks of at least the first and second connection elements described herein. These several stacks may electrically connect different elements of the apparatus. Alternatively, two or more stacks may electrically connect the same elements, and the use of more than two stacks further increases the current capability.

[0084] 11 shows a flow chart of an exemplary embodiment of a method for manufacturing a device. In step S1, a first connection element is electrically and mechanically connected to a contact area in a first joining area by a joining process, for example ultrasonic welding or laser welding or soldering. In step S2, a second connection element is electrically and mechanically connected to the first connection element in a second joining area by laser welding.

[0085] FIG. 12 shows a further exemplary embodiment of the device, in which two connection elements 1, 2 connect a power semiconductor device 3 with a top metallization 40 of a substrate 4 and further with a terminal 50. For this purpose, a first end of a first connection element 1, for example a ribbon, is firmly bonded to a contact area A1 in a first bonding area 11, the first contact area A1 being formed by the power semiconductor device 2. A first end of a second connection element 2, for example also a ribbon, is laser welded onto the first connection element 1 in a second bonding area 12. The second ends of the first connection element 1 and the second connection element 2 are firmly bonded in a third bonding area 13 and a fourth bonding area 14, respectively, to further contact areas A2 formed by terminals 50 and laser welded to each other. A stitched electrical connection to the top metallization 40 is formed between the first and second ends of the connection elements. Thus, the first connection element is firmly bonded to the third contact area A3 formed by the top metallization 40 at the fifth bonding area 15, and the second connection element 2 is laser welded onto the first connection element 1 at the sixth bonding area 16 which overlaps with the bonding area 15 in a plan view of the third contact area A3.

[0086] FIG. 13 shows an exemplary embodiment of a device in which two substrates are electrically interconnected by two clips 1, 2. FIG. 13 shows a plan view in which only the second clip 2 covering the first clip 1 is visible. The clips 1, 2 are metal sheets before bending. The first leg of the first clip 1 is firmly bonded to the contact area A1 formed by the top metallization 40 of the first substrate 4. The first leg of the second clip 2 is laser welded to the first leg of the first clip 1. Furthermore, the second leg of the first clip 2 and the third leg of the first clip 2 are firmly bonded to two different contact areas A2, A3 formed by different top metallizations 40 of the second substrate 4. The second leg of the second clip 2 is laser welded to the second leg of the first clip 2 and the third leg of the second clip 2 is laser welded to the third leg of the first clip 1.

[0087] The embodiments shown in Figures 1-11 above represent exemplary embodiments. Thus, they do not constitute an exhaustive list of all embodiments of the apparatus, power modules, and methods. The actual apparatus, power modules, and methods may differ from the embodiments shown, for example, with respect to devices and elements. [Explanation of symbols]

[0088] Reference sign 1. First Connection Element 2 Secondary connection element 3. Power Semiconductor Devices 4. Board 5 Housing Elements 6 Encapsulation 7 Base plate 11 First junction area 12 Second junction area 13 The third junction area 14 The fourth junction area 15 The fifth junction area 16 The sixth junction area 30 electrodes 40 Top Metallization 41 Insulating layer 42 Bottom Metallization 50 Terminals 100 devices 1000 Power Module S1 Method step S2 Method step A1 Contact area A2 Further contact area A3 Third contact area

Claims

1. An apparatus (100) for a power module, comprising: Conductive contact areas (30, 40, 50); a first connecting element (1) and a second connecting element (2) for electrically connecting said contact areas (30, 40, 50); Equipped with the first connecting element (1) is firmly joined to the contact area (A1) in a first joining area (11), The device, wherein the second connection element (2) is welded to the first connection element (1) by laser welding in a second joining area (12).

2. 2. The device (100) according to claim 1, wherein the first bonding area (11) and the second bonding area (12) at least partially overlap each other in a plan view of the contact area (A1).

3. 3. The device (100) according to claim 1 or 2, wherein the first connecting element (1) is welded to the contact area (A1) by ultrasonic welding or laser welding or soldering or gluing.

4. 10. The device (100) according to any one of the preceding claims, wherein the first connecting element (1) and the second connecting element (2) are stacked on top of each other.

5. said first connecting element (1) and said second connecting element (2) electrically connecting said contact area (A1) to a further contact area (A2) of said device (100); said first connecting element (1) being firmly joined to said further contact area (A2) in a third joining area (13), the second connecting element (2) is welded to the first connecting element (1) by laser welding in a fourth joining area (14); 10. The device (100) according to any one of the preceding claims, wherein the third bonding area (13) and the fourth bonding area (14) at least partially overlap each other in a plan view of the further contact area (A2).

6. The contact area (A1) is a top metallization (40) of the substrate (4) of said device (100), or a power semiconductor device (3) of said apparatus (100), or Terminals (50) for external electrical connection of said device (100) 13. The apparatus (100) of any one of the preceding claims, formed by:

7. The further contact area (A2) a top metallization (40) of the substrate (4) of said device (100), or a power semiconductor device (3) of said apparatus (100), or Terminals (50) for external electrical connection of said device (100) The device (100) according to claim 5 or claim 6 depending on claim 5, formed by:

8. 10. The device (100) according to any one of the preceding claims, wherein the first connecting element (1) and / or the second connecting element (2) are ribbons or clips.

9. the first connection element (1) and the second connection element (2) are both terminals for external electrical connection, The connection portions (1a, 2a) of the external connection terminals (1, 2) are spaced apart from each other. An apparatus (100) according to any one of the preceding claims.

10. One of the first connection element (1) and the second connection element (2) is a main terminal; the other of the first connection element (1) and the second connection element (2) is an auxiliary terminal; 10. The apparatus (100) of claim 9.

11. 10. The device (100) according to any one of the preceding claims, wherein the second connection element (2) is connected to the first connection element (1) via a plurality of laser welded weld joints (120) distributed over the second joining area (12) and spaced apart in pairs from one another.

12. A power module (1000) comprising an apparatus (100) according to any one of the preceding claims.

13. The device (100) is a device according to claim 9 or any one of claims 10 and 11 depending on claim 9, the connection parts (1 a, 2 a) are exposed and freely accessible in the non-connected configuration of the power module (1000); The power module (1000) of claim 12.

14. A method of manufacturing an apparatus (100) for a power module, comprising the steps of: - electrically and mechanically connecting the first connection element (1) at the first joining area (11) to the contact areas (30, 40, 50) by a joining process; - electrically and mechanically connecting a second connection element (2) to said first connection element (1) by laser welding in a second joining area (12); A method comprising:

15. The method according to claim 14, wherein the first bonding area (11) and the second bonding area (12) are formed so as to at least partially overlap each other in a plan view of the contact area (30, 40, 50).

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