The present invention relates to the field of power electric modules in particular to

semiconductor power electric modules having an electrical conductor. The present invention also extends to power electric modules comprising a busbar. Such power electric modules can be a power converter or a power conversion device comprising components such as transistors or semiconductor switches, which may be used in a variety of applications from smaller low voltage systems to larger high voltage systems, e.g. transportation systems, such as trains and electrical vehicles, e.g., or as well in the fields of renewable energy conversion.

Systems which utilise such power electric modules, in particular when used in a system for powering electrical equipment such as electrically driven vehicles or other electrically driven devices, are built usually by a plurality of different power electric modules which are connected to each other via terminals protruding outside from casings of each power electric module. The terminals of different power electric modules can be connected directly to each other or by means of a busbar, which in the gist of the invention also constitutes a power electric module. A connection by electric wires is also to be covered by the invention. In any case, the terminals are provided to connect the electrical conductors within each power electric module with other electric devices to complete, e.g. the electric equipment for an electric drive train of a vehicle.

The connection of two power electric modules is commonly implemented by means of screw joints requiring at least one screw per terminal connection and, in most cases, also a nut and a washer for reliably joining two terminals of two power electric modules together. Using screw joints further requires openings in the terminals in order for the screw used for connecting the terminals to pass the terminals and to seat properly on the terminal. If a nut for holding the screw tidily is to be avoided one of the terminals should be equipped with a thread. Hence, this kind of joining of terminals of two power electric modules requires a lot of preparation and a lot of parts, which makes a screw joint complex and laborious, especially in an automatic process for building up electric equipment. Moreover, the removal of a conductive area to insert the screws in holes in the corresponding terminals reduces the overall current density of the power electric module. Therefore it is an object of the invention to simplify the connection between two power electric modules in order for the manufacturing costs of power electric modules as well as for the assembly costs to be reduced when building a power electric assembly or equipment. In addition, the invention is to provide a robust and reliable connection between terminals of two power modules.

This object is solved by a power electric module according to the features of claim 1. According to the invention a power electric module comprises a casing with electrical components mounted therein and having at least two electrical conductors for conducting electrical current at differing electrical potentials between an outside of the casing and the electrical components located inside the casing. Each of the electrical conductors is at least partially powder-coated with a thermo-stable resin for electric insulation and comprises at least one terminal which protrudes from the casing to outside. The at least one terminal of each connector is provided hole-free and is able to be electrically connected permanently to other terminals of other electric devices of an electric equipment, especially by means of material bonding.

By means of providing powder-coated electrical conductors having hole-free terminals protruding outwards from a casing of the power electric module, terminals of other power electric modules or devices can be connected by material bonding. In particular, automated processes for connecting the terminals can be applied, for instance, all kinds of welding, sintering, soldering or gluing. As screws, washers and/or nuts do not have to be provided any longer for connecting the terminals the assembly costs of a power electric assembly or equipment comprising at least one inventive power electric module can be reduced significantly. By providing hole-free terminals the connection of power electric devices can be realized, e.g. by laser welding or spot welding, wherein all other kinds of material bonding are applicable for connecting these kinds of terminals.

For contacting electric currents at differing electrical potentials to the inventive power electric module a powder coating has to be applied to the conductors for guiding the current between the terminals located outside of the casing to the circuit pattern and/or other electric

components located inside without short circuit. This powder coating to the conductors has to be a thermo-stable one such that an electric installation provided by the powder coating between two adjacent electric conductors is maintained also after applying the necessary heat energy for material bonding, like laser welding or the like to connect the terminals of an inventive power electric module to terminals of a further electric device. The thermo-stability of the powder coating preferably at least provides for thermo-resistivity against heat that the electrical insulation withstands the heat ingress into the terminals during the material bonding process and after cooling down the connection area. However, certain softening during the material bonding may be admissible, as long as the powder-coated electric insulating layer is not damaged and prevents short circuits during operation of the inventive power electric module.

Suitable thermo-stable resins for use in the powder coating of the conductors for the inventive power electric module can be a duroplast material or an epoxy resin, however certain kinds of thermoplastic material are also applicable as long as they maintain the electrical insulation between adjacent conductors. Preferably thermoplastic material is used, even when gluing is applied for material bonding of the terminals. Hence, the usable resin for powder coating the electrical conductor also depends on the bonding method applied to the terminals, i.e. when gluing is the way of bonding the terminals a less thermo-stable resin can be applied to the electrical connectors as compared to laser welding or spot-welding as the way of bonding.

By providing electrical conductors being at least partially powder-coated with a thermo-stable resin for electric insulation and simultaneously not showing openings for screwing terminals together with screws or bolts the inventive power electric module, in particular the terminals, can be designed smaller in its overall dimensions because the cross section necessary to provide a low resistant and low inductive conduction of electric current is not being disturbed by openings, as this is the case when screw joints are used.

Furthermore, by the use of hole-free terminals their cross section provides for a low impedance and low inductive electrical contact between the terminals due to the absence of openings in the terminals, which considerably decrease the cross section available for current. A further advantage is given by the fact that no further, i.e. additional material of screws or bolts disturbs the electrical flow between the terminals. Thus for the terminals the same material is usable consequently without introducing separate parts with a differing conductivity. Hence, by use of material bonding, e.g. laser welding, which is the preferred method of joining terminals according to the invention, an electrical connection with better conductivity, i.e. with lower electric resistance and lower inductivity, is obtained contrary to the screw joint connections according to the state of the art. Ultrasonic welding could be an alternative to standard industrial laser welding.

In a preferred embodiment the electric conductors used are not powder-coated completely, in particular not in the regions which are provided for electric connection of the invented power electric module to terminals of other electric devices or to connection areas on the circuit pattern and/or on electric components located inside the inventive power electric module. This, for example, can be achieved by masking the respective regions or by applying, preferably locally, a releasing agent in the respective areas. A person with skills in the relevant art will detect a variety of possibilities for this purpose in order to maintain certain regions of the electric conductor free of powder-coating. Hence, all these possibilities are covered by the invention.

As it is common state of the art, the casings which house the electrical connectors can be a kind of prefabricated box or a molded casing. The latter is one of the preferred embodiments for such a casing when construction space requirements limit the size of the power electric module. Naturally, when mounting or molding the electrical conductors within the casing, the terminals provided for electrical connections with terminals of other electrical devices protrude outside from the molded or assembled casing, so that the terminals can be of any form, in particular for the connection to a busbar or any other electric device. Hence, the terminals can be a busbar terminal or a plurality of such busbar terminals or pin terminals or a combination thereof to provide electric connection of the inventive power electric module with a busbar or any other electric device.

Accordingly, the inventive power electric module can have a plurality of conductors, each of which can comprise more than one terminal protruding from the casing to the outside, and apart therefrom, each terminal may also provide for more than one connecting area. For this purpose the terminals for differing electrical potentials can be, however, don ^' t have to be, aligned in one plane. For instance, for easy connection to a busbar all terminals of one electric potential are aligned in one first plane and can be aligned in a second plane for connection to another electric potential. A person skilled in the art would easily detect that the arrangement of the terminals mentioned before can be of any other kind and no limits are given as long as electric contact of terminals with differing electric potentials does not provide for electric short circuit. The inventive idea includes also the arrangement of a plurality of terminals protruding from different sides of the casing including lateral sides and top side.

In an exemplary embodiment the inventive power electric module is a semiconductor power module comprising at least one semiconductor which can be, in particular, a wide bandgap semiconductor, such as silicon carbide (SiC) or gallium nitride (GaN). Such semiconductor components provide larger bandgaps, higher breakdown electric field, and higher thermal conductivity. Power electric modules made with SiC or GaN are capable of higher blocking voltages, higher switching frequencies, and higher junction temperatures than traditional silicon devices. With the inventive power electric module a further advantage is achieved when the material- bonded terminals which are permanently electrically connected, are coated or covered with a resin, a lacquer or the like. On the one hand, the material bonding can be protected, e.g.

against humidity and/or dirt, on the other hand, the cover or coating material provides for electric insulation. Hence, by coating or covering the material-bonded terminals with an additional resin, lacquer or the like electric insulation between the terminals at differing electrical potentials is provided, too. By doing this, the electric insulation of adjacent terminals can be improved, which means for the inventive power electric module that the distance of terminals at differing electrical potential can be decreased, i.e. the terminals can be arranged closer to each other as with power electric modules known from the state of the art, as short circuits are avoided by means of the coating or covering resin or lacquer or the like, and a higher degree of compactness is achieved. Using the aforementioned construction the inventive power electric module power will have a particularly low parasitic (commutation) inductance.

By the help of the inventive power electric module power electric assemblies, in particular for applications having a life time permanent connection requirement for the used power electric modules, can be manufactured more easily at reduced assembly costs. Furthermore, these power electric assemblies having terminals with a corresponding permanent connection, can be designed smaller due to their hole-free design and/or their capability to be covered or coated additionally with electric insulating material. By doing this, the electric connection between terminals of differing electrical potential can be arranged closer to each other. Hence power electric assemblies being more compact can be achieved. This is especially important for applications of power module assemblies in electric equipments with restricted construction space, like it is quite often the case for the automotive industry.

The above and other aspects of the invention will be described in the following in detail with the help of exemplary embodiments which are shown in the accompanying figures. These exemplary embodiments do not limit the scope of the invention and can be modified by a person skilled in the art without departing from the scope of the inventive idea. Hence, the following description of exemplary embodiments of the invention is made with reference to the drawings and is intended to illustrate the general inventive concept of the invention and should not be interpreted as being limitative to the inventive idea. In the drawings:

Figure 1 shows an embodiment for a power electric module according to the invention in a perspective view; and

Figure 2 shows the embodiment of Figure 1 connected to a further electric device; Figure 3 shows an example of a power electric assembly comprising an inventive power electric module;

Figure 1 shows an embodiment for a power electric module 1 according to the invention in a perspective view. Within a casing 2 electric components not visible and/or one or more semiconductors not visible either are connected to the outside of the casing 2 by means of conductors 3. The conductors 3 comprise terminals 4 for connecting the power electric module 1 with other electric devices not shown. Thereby the connecting areas 6 of the terminals 4 are hole-free and free of powder coating 5.

Figure 2 shows a power electric assembly 10 according to the invention having the inventive power electric module 1 connected on one side of the casing 2 by material bonding to a further electric device, here, exemplarily, a busbar module 7. The busbar module 7 may be a capacitor bank also comprising a busbar, may be any other power electric device. Consequently and according to the invention, the terminals 4 of the conductors 3 of the busbar module 7 are realized in the same way as the conductors 3 of the power electric module 1 , i.e. they are provided with a powder coating 5 for internal electric insulation, wherein, in particular, the terminals 4 itself, are free of powder coating and are hole-free in the connection areas 6. More preferably, the terminals 4 of the power electric module 1 facing the other electric device, here a busbar module 7, are welded, e.g. by laser welding, to the terminals 4 of the busbar module 7. For reasons of ease illustration a cover or coating of the connection areas 6 is not shown, however it is preferred to enhance electric insulation in between adjacent material bonded terminals9.

At least a skilled person derives easily from Figure 2 that another further inventive power electric module 1 or any other electric device can be material bonded with its terminals to the busbar module 7 in a very compact way close to the first power electric module 1. Since no screws are used for joining the terminals of two modules and since the material bonding is intended to be non-releasable during the life span of the power electric assembly, a further power electric module can also be connected to the busbar module 7 above or below the first power electric module 1. Hence the inventive design of hole-free terminals 4 at the power electric module 1 provides for greater freedom in the architecture of power electric module assemblies 10, as an accessibility for screwing tools is no longer necessary.

Figure 3 shows an example of a power electric assembly 10 comprising an inventive power electric module 1 , in which the terminals 4 of the power electric module 1 are connected to the terminals 4 of a busbar module 7 by means of material bonding, wherein the connection area between the two components is protected by an insulating material 8, e.g. a resin or lacquer. This insulating material 8 does not cover only the material bonded terminals 9, but insulates the different material bonded terminals 9 from each other. In Figure 3, for illustrative purposes only, the insulating material 8 is shown as a transparent material, however, in practice it is not relevant to the invention whether or not the insulating material 8 is transparent. A person skilled in the art will understand that it is up to design reasons, for instance the distance of two adjacent material bonded terminals 9 and the amount of electric power which is to be conducted over the connected terminals 9, whether the insulating material 8 is applied as a thin layer on each connection of two material bonded terminals 9 or in the manner of an additional casing covering the whole connection area between two power electric components.

The present invention provides for power electric modules in general, which can be designed more compact with terminals at differing electrical potential being arranged closer to each other, due to the possibility to cover the material bonded connection to other electric devices with an electrical insulating resin or lacquer or the like, such that the clearance and/or creepage distance can be reduced significantly. Furthermore, as the material bonding of the terminals is a permanently electric connection which does not have to be released during life time of the power electric modules, the power electric modules of a power electric module assembly can be stacked together to obtain a more compact design, as accessibility to the connection areas is no longer necessary. Hence the present invention provides especially for space-critical applications for power electronics more freedom in architecture and more reliable connections, due to material bonding, as well as less manufacturing and assembling costs, in particular automation of assembling of power electric module assemblies can be improved further. Furthermore short circuit failure is reduced also as the connection of the material bonded terminals can be insulated by applying an electric insulating cover material on the connected terminals which does not have to be accessed in an assembly state during life time of the power electric module assembly. List of reference numbers

1 Power electronic module 2 Casing

3 Conductor

4 Terminal

5 Powder coating

6 Connecting area

7 Busbar module

8 Insulating material

9 Material bonded terminals

10 Power electric assembly