Power semiconductor module with interconnected package portions

A power semiconductor module includes a package having a first package portion and a second package portion. The side of the first package portion facing the second package portion has an anchoring element with a first recess. The second package portion includes a second recess with an indentation which receives the anchoring element. To produce a mechanically firm connection between the first package portion and the second package portion, a plug-in element is inserted in the first recess and the second recess. The plug-in element displaces the anchoring element transversely with respect to the plug-in direction, causing the anchoring element to engage the indentation so that a form-fit connection is produced between the first package portion and the second package portion. The plug-in element prevents the anchoring element from disengaging the indentation.

PRIORITY CLAIM

This application claims priority from German patent application 10 2010 000 943.1 filed on 15 Jan. 2010, the content of said German application incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to a power semiconductor module, and particularly to a power semiconductor module having interconnected package portions and a method for fabricating such a power semiconductor module.

BACKGROUND

Power semiconductor modules have one or more power semiconductor chips which are arranged in a package. The package serves to protect the power semiconductor chips from environmental influences, and for electrically insulating the circuit produced by the power semiconductor chips.

By way of example, such a package may have individual side walls, or a package frame which forms the side walls of the module, and also a package cover and/or a baseplate. In order to fabricate the package, the side walls or the package frame must be connected to the package cover and/or to the baseplate with a precise fit and in mechanically robust form.

However, screw connections require screw elements and hence a correspondingly complex assembly process. In order to produce adhesive bonds, the adhesive needs to be distributed, the package portions to be connected need to be mated and the adhesive needs to be cured, which is complex and time-consuming. For ultrasonic welding and locking, it is necessary to observe low process tolerances. In addition, locking allows only low load-bearing capacity to be achieved for the connection. Caulking likewise requires low process tolerances to be observed.

SUMMARY

A power semiconductor module is provided in which individual package elements are connected using a connection technique which is feasible for mass production, and in which it is possible to dispense with the cited connection techniques (e.g. screwing, adhesive bonding, ultrasonic welding, locking, caulking). A corresponding method is described for fabricating such a power semiconductor module.

According to one embodiment of a power semiconductor module, the module includes a package having a first package portion and a second package portion. The side of the first package portion facing the second package portion has an anchoring element with a first recess. The second package portion has a second recess with an indentation which receives the anchoring element. The anchoring element engages the indentation, so that there is a form-fit connection between the first package portion and the second package portion. In order to prevent the anchoring element from disengaging from the indentation, a plug-in element is provided which is inserted in the first recess and the second recess and which prevents the anchoring element from disengaging from the indentation and thus protects the form-fit connection between the first package portion and the second package portion.

According to an embodiment of a method for fabricating a power semiconductor module, the method involves the provision of a first package portion, which has an anchoring element with a first recess, and the provision of a second package portion, which has a second recess with an indentation. In addition, a plug-in element is provided. When the anchoring element has been positioned in the second recess, the plug-in element is inserted in the first recess and the second recess. This prompts the anchoring element to be displaced laterally, in relation to the plug-in direction, so that a displaced section of the anchoring element engages the indentation, with a form-fit connection being produced between the first package portion and the second package portion.

DETAILED DESCRIPTION

The detailed description which follows relates to the accompanying drawings, which form part of the description and in which specific refinements are used to explain the way in which the invention can be implemented. Directional statements in this regard, such as “top”, “bottom”, “front”, “back”, “anterior”, “posterior” etc., are used in relation to the orientation of the figures explained. Since the elements in the refinements can be arranged in a multiplicity of different orientations, the directional terminology serves merely to clearly explain the figures and should in no way be understood to be limiting. It is pointed out that the present invention may also comprise other refinements. In addition, it is pointed out that any features of the various exemplary refinements described below can be combined with one another unless anything to the contrary is expressly mentioned, or provided that a combination of particular features is not precluded for technical reasons.

FIG. 1Ashows a vertical section through two package portions of a package for a power semiconductor module which are intended to be connected to one another. The module comprises a package having a first package portion1and a second package portion2. By way of example, the second package portion2may be a side wall of an individual side, an annularly closed package frame, or may be an arbitrary section of a package side wall of the power semiconductor module package. By way of example, the first package portion1may be in the form of a flat package cover or in the form of a baseplate of the module package.

In order to mechanically connect the first package portion1to the second package portion2, the first package portion1has an anchoring element3which is provided with a first recess4. In the present example, the anchoring element is in the form of a tubular extension on the first package portion1. In this case, recesses within the context of the present application are regarded as depressions which are partially or totally sealed at their end, as is the case with blind holes, for example, or else passage openings, as shown by way of example inFIG. 1A.

The second package portion2has a second recess5which extends from a first side21of the second package portion2into the second package portion2and which is in a form such that it can completely or at least partially accept the anchoring element3when the first package portion1has a first side11placed onto the first side21of the second package portion2. The second recess5comprises an indentation51which is formed by virtue of the width of the second recess5being increased—in at least one sectional plane through the second package portion2—in a subregion of the second recess5as depth increases. In this case, the depth is ascertained in relation to the level of the entrance opening of the second recess5. In the case of the arrangement shown inFIG. 1A, this level is situated on the first side21of the second package portion2. In the present example, the indentation51is formed by virtue of the second recess5having an inclined side wall.

FIG. 1Bshows the arrangement after the first package portion1has been placed on the second package portion2with a precise fit such that the anchoring element3is arranged in the second recess5. If the first package portion1is a package cover or a baseplate of the module package, for example, and the second package portion2is a package frame of the module package, then the first package portion1may be in a form such that it covers an opening formed by the second package portion2completely. As can also be seen fromFIG. 1B, a subregion of the second recess5between the anchoring element3and the second package portion2, which subregion is formed on the basis of the indentation51, remains at least temporarily free.

In addition, a plug-in element6is provided which can be introduced from a second side12of the first package portion1, which is remote from the second package portion2, both into the first recess4and into the second recess5, so that the arrangement inFIG. 1Cis produced.

To this end, the first recess4is in a form such that, when the plug-in element6is slid into the first recess4, it has a lack of length in comparison with the plug-in element6at least at a slide-in position, so that the anchoring element3is displaced at least to some extent laterally, i.e. at right angles to the slide-in direction z, to the extent that the anchoring element3engages in the indentation51, which produces a form-fit connection between the first package portion1and the second package portion2. In addition, the plug-in element6prevents the anchoring element3from disengaging from the indentation51. In order to allow lateral displacement of the anchoring element3, the first recess tapers at least in a particular section as the distance from the first package portion1increases. Such tapering can be effected conically or in steps, for example. Any other tapers are likewise possible, however.

Another embodiment is shown inFIG. 2A. In this arrangement, the first package portion1is in the form of a package side wall, in the form of an annularly closed package frame, or in the form of part of a package side wall or of an annularly closed package frame, while the second package portion2is a package cover or a baseplate of the module package.

As in the case of the arrangement shown inFIG. 1A, the anchoring element3is arranged as an extension on the first package portion1and is of integral design with the latter. In addition, the anchoring element3also has a first recess4which is sealed at the lower end thereof but which can optionally also extend continuously as far as the second side12of the first package portion1, which forms the side of the first package portion1remote from the first side11.

The second package portion2has a second recess5which is in the form of a passage opening. The anchoring element3and the second recess5are in tune with one another such that the anchoring element3can be inserted into the second recess5without force or only with little force, so that the arrangement shown inFIG. 2Bis produced. The insertion can be effected such that the anchoring element3is not deformed in the process. Alternatively, it is possible for the anchoring element3and/or the first package portion1to be deformed elastically or plastically when the anchoring element3is inserted into the second recess5, for example by virtue of the anchoring element3having an excess length in comparison with the second recess5.

Since, in this embodiment too, the second recess5is provided with an indentation51, a free region remains at least temporarily between the anchoring element3and the second package portion2after the anchoring element3has been positioned in the second recess5.

AsFIG. 2Cshows, the anchoring element3can be displaced laterally, i.e. at generally right angles to the plug-in direction z, to a certain degree by introducing a suitably dimensioned plug-in element6into the first recess4and into the second recess5, so that the anchoring element3engages in the indentation51, so that a form-fit connection is produced between the first package portion1and the second package portion2. The plug-in element6introduced into the first recess4and into the second recess5prevents the anchoring element3from disengaging from the indentation51and hence reliably protects the mechanical connection between the first package portion1and the second package portion2.

In this embodiment too, the plug-in element6is in a form such that it has an excess length in comparison with the first recess4when slid into the first recess4at least one slide-in position laterally with respect to the slide-in direction z, the excess length prompting the anchoring element3to be expanded laterally with respect to the slide-in direction z and thereby to engage in the indentation51.

FIG. 3Ashows a perspective sectional view through a first package portion1, which may be of the same design as the first package portion1shown inFIGS. 1A to 1C. As can be seen fromFIG. 3A, an anchoring element3may have one or more slits31which facilitate lateral, elastic or plastic displacement of the anchoring element3when a plug-in element6is plugged into the first recess4as shown inFIG. 3B.

Whereas the plug-in element6in the arrangements shown inFIGS. 1B,1C,2B and2C is in the form of a solid pin by way of example, the plug-in element6shown inFIG. 3Bis a hollow element. A hollow element of this kind may have a tubular section, for example. This section may be—as shown—a cylindrical tube, for example. Any other tube cross sections are likewise possible, however.

As can also be seen from the plug-in elements6shown inFIGS. 1B,1C,2B,2C,3B and3C, a plug-in element6may have a stop65which hits the first package portion1on the second side12of the first package portion1, which is remote from the second package portion2, when the plug-in element6is plugged into the first recess4, so that the plug-in depth is limited by the stop61. As shown in the present exemplary embodiments, a stop65of this kind may be in the form of a circumferential collar on the plug-in element6, for example. In principle, it is also possible to dispense with such a stop65, however, as shown in a further exemplary embodiment inFIGS. 4A to 4C.

In the embodiment described above, the indentation in the second recess5is produced by inclined, straight side walls, as shown inFIG. 5Afor the second recess5in the second package portion2shown inFIGS. 1A to 1Cand inFIG. 5Bfor the second recess5in the second package portion2shown inFIGS. 2A to 2C.

However, an indentation51in the second recess5in a second package portion2does not necessarily need to be produced by inclined side walls of the second recess5. Alternatively or in addition, the side wall of the second recess5may be designed to be continuously curved completely or at least in sections. In this context, “continuously curved” is understood to mean a continually differentiatable—in the mathematical sense—profile of the side wall or of a section of the side wall.

FIG. 6Ashows a respective second recess5with continuously curved side walls for a second package portion2as shown inFIGS. 1A to 1C, andFIG. 6Bshows a respective second recess5with continuously curved side walls for a second package portion2as shown inFIGS. 2A to 2C.

Instead of or in addition to an at least sectionally inclined, straight side wall and/or an at least sectionally continuously curved side wall, a second recess5may also have an indentation formed by a step, as shown by way of example inFIGS. 7A and 7B.FIG. 7Ashows a respective second recess5, the side wall of which has a step, for a second package portion2as shown inFIGS. 1A to 1C, andFIG. 7Bshows a respective second recess5, the side wall of which has a step, for a second package portion2as shown inFIGS. 2A to 2C.

It is possible to use and combine fundamentally any, including different, materials for the first package portion1and for the second package portion2and also for the plug-in element6.

Insofar as a first or second package portion1or2is in the form of a package side wall or in the form of a package cover or in the form of part of a package side wall or a package cover, it may be formed from plastic, for example. Plastic is an electrical insulator and can be made into almost any arbitrary shape, for example by injection molding. By way of example, the first package portion1and the anchoring element3may be produced in the same injection mold and in the same injection molding step and thereby be an integral design.

In the examples shown inFIGS. 1A,1B,1C,5A,5B,5C, the second recess5is in the form of a blind hole. Alternatively, the recess5may, as indicated by dashed lines inFIG. 5A,5B,5C, also be in the form of a passage opening between opposite sides21and22of the second package portion2. In such embodiments, a plug-in element6can also be introduced into the recess5from the second side22and extend into a recess4in an anchoring element3

which, as shown inFIGS. 1A to 1C, for example, is arranged in the second recess5when the first package portion1is positioned on the side21of the second package portion2.

In the exemplary embodiments described above, the plug-in element6is respectively provided as a separate element, i.e. an element which is independent of the first package portion1and of the second package portion2. In these embodiments, the plug-in element6is positioned correctly before it is plugged into the first recess4and into the second recess5. However, the effort associated with this step can be avoided if the plug-in element6, prior to being slid into the first recess4and into the second recess5, is firmly or moveably connected to that instance of the package portions1,2which is arranged between the other package portion2,1and the plug-in element6during assembly.

By way of example, the connection between the plug-in element6and the relevant package portion1,2may be produced by one or more thin snap-off elements66, e.g. in the form of a thin film or a ribbon hinge, as shown schematically inFIG. 8A. Such snap-off elements66can be produced together with the injection molding process, which is also used to produce the package portion1to which the snap-off elements66are connected. As a result, the snap-off elements66are of an integral design with the relevant package portion1and the plug-in element6. Regardless of the specific refinement of the connection between the plug-in element6and the relevant package portion1, such a connection allows the plug-in element6to adopt a prescribed, precisely defined position in relation to the first recess4or second recess5situated on the relevant package portion1or2, from which position the plug-in element6can easily be slid into the first recess4and into the second recess5without previously aligning the plug-in element6laterally with respect to the slide-in direction z.

Hence, in such an embodiment, only the package portions1and2need to be positioned relative to one another. On account of the firm connection between the plug-in element6and one of the two package portions1or2, the plug-in element6together with the relevant package portion1or2is positioned automatically and then needs only to be slid into the first recess4and the second recess5as explained previously herein.

Optionally, the plug-in element6can be separated from the package portion1,2to which it is attached during the sliding-in or by the sliding-in. In the case of the aforementioned connection by means of one or more snap-off elements66, said snap-off elements respectively form a predetermined breaking point which is snapped off when the plug-in element6is slid in, so that the plug-in element6is no longer integrally connected to the relevant package portion1when it has been slid into the first recess4and into the second recess5completely.FIG. 8Bshows the arrangement after the plug-in element6has been slid into the recesses4and5completely.

The first package portion1and/or the second package portion2may be produced not only from plastic, as described, but also from metal, for example. In order to provide a metal first package portion1with an anchoring element3, the first package portion1and the anchoring element3may be of an integral design. Such refinements can be achieved by casting, embossing or milling, for example. However, it is likewise possible for the first packaging portion1and the anchoring element3to be produced independently of one another at first and then to be connected to one another by soldering, welding, adhesive bonding, clamping, screwing or another connection technique.

FIG. 9Ashows individual parts of a power semiconductor module during the fabrication thereof. The module includes a package portion80, e.g. made of plastic, which is in the form of a closed frame, a package cover70, e.g. also made of plastic, and a metal baseplate90of the module package. In addition, a ceramic substrate97is provided, the underside of which is provided with a lower metallization which is soldered to the baseplate90. The top of the ceramic substrate97is provided with an upper metallization which is patterned to form interconnects and to which a power semiconductor chip98arranged on the ceramic substrate97, for example a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a junction field effect transistor (J-FET), a thyristor, a diode or the like, is electrically conductively connected. The upper metallization and the lower metallization are electrically insulated from one another by the ceramic substrate97.

In addition, a metal connection strap99is provided which is electrically conductively connected to the power semiconductor chip98and which is used for making electrical contact with the power semiconductor module on the outside of the module. To this end, the connection strap99has a threaded eye. Instead of using a threaded eye, the connection strap99can also be provided with a press-fit contact or another connecting element, for example.

The package cover70is provided with an anchoring element73which has a recess74. A first side81of the package frame80has a recess85with an indentation851. A second side82of the package frame80, which is remote from the first side81, is provided with an anchoring element83which has a recess84. In addition, the baseplate90contains a recess95which has an indentation. Furthermore, a plug-in element61having a stop615and a plug-in element62are provided.

The package cover70and the baseplate90can be connected to the package frame80using the previously described connection technique.

The package cover70is connected to the package frame80using the method explained with reference toFIGS. 1A to 1C. In this context, the following equivalents in Table 1 apply:

The baseplate90is connected to the package frame80using the method explained with reference toFIGS. 2A to 2C. In this context, the following equivalents in Table 2 apply:

For the purpose of assembling the power semiconductor module100, the package frame80is placed onto the baseplate90, fitted with components, such that the anchoring element83is arranged in the recess95. Accordingly, the package cover70is placed onto the package frame80such that the anchoring element73is arranged in the recess85. In addition, the package cover70has an opening through which the upper end of the connection strap99with the threaded eye can extend into the outside space of the package for the purpose of making electrical contact later.

AsFIG. 9Bshows, the plug-in element62is slid into the recesses95and84, after the package frame80has been placed onto the baseplate90so that the anchoring element83engages in the indentation951. Accordingly, the plug-in element61is slid into the recesses85and74after the package cover70has been placed onto the package frame80so that the anchoring element73engages in the indentation851. In this way, the package cover70, the package frame80and the baseplate90are firmly connected to one another to form a module package for the power semiconductor module100.

FIG. 9Cshows a plan view of the power semiconductor module100with the package cover70removed.FIG. 9Calso shows a sectional plane A-A corresponding to the views shown inFIGS. 9A and 9B.

In the plan view shown inFIG. 9C, it is possible to see that the package frame80may be in the form of a circumferential, annularly closed frame. In addition, it can be seen from the example of a plurality of recesses951in the package frame80that it is also possible to use a plurality of the previously explained connection techniques in order to connect two arbitrary package portions. In this case, it is likewise possible to provide any combination of a plurality of identical or equivalent connection techniques which have been explained for the purpose of connecting the two package portions, such as a plurality of the different connection techniques explained.