Housing for power semiconductor modules

A housing for power semiconductor modules with a base plate or for direct mounting on a heat sink. The housing (10) surrounds an electrically insulating substrate (40) with metal connection tracks (41) disposed thereon. The metal connection tracks are insulated from one another and have power semiconductor components (50) disposed on them. The housing has a cap (14) and at least one framelike housing part (12) forming the side walls thereof. This housing part (12) includes a main frame (120) and at least one locking frame (130). The main frame (120) has guides (122, 128) for receiving connection elements (30, 32). The locking frame (130) is disposed relative to the main frame (120) such that it rests at least in part on the connection tabs (310, 320) of the connection elements (30, 32), in order to prevent movemnt of the connection elements toward the substrate (40).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a housing for power semiconductor modules with a base plate or for direct mounting on a heat sink.

2. Description of the Related Art

Known power semiconductor modules comprise a housing with connection elements and a substrate with power semiconductor components disposed thereon and connected appropriately in terms of circuitry, such as thyristors and/or diodes, but also power transistors such as MOSFETs or insulated gate bipolar transistors (IGBTs) with recovery diodes connected antiparallel to them.

Modern power semiconductor modules of the kind known for instance from European Patent Disclosure EP 0 750 345 A2 are therefore the point of departure of the present invention. These power semiconductor modules, with particular attention to the components essential to this invention, comprise the following:A base of the power semiconductor module that comprises either a base plate with a substrate disposed on it, or solely a substrate;a substrate, which has connection tracks structured appropriately for the circuitry, on which tracks semiconductor components or other components are disposed;an at least partly framelike housing, which surrounds the substrate and in which the connection elements are embedded, for electrically connecting the components or substrate to external supply lines; anda cap, as a top closure for the power semiconductor module.

Essentially, connection elements in power semiconductor modules have two different tasks: First, connecting the external load current supply lines to the power semiconductor components, and second, connecting external control and/or auxiliary terminals for controlling the power semiconductor components, for connecting to sensors inside the power semiconductor module, or for connecting to further components inside the power semiconductor module. Connection conductors for load currents preferably have screw connections to the external supply lines, while the external control and/or auxiliary terminals are preferably embodied as plug contacts. In the prior art, in the interior of the power semiconductor module, wire bond connections often form the electrical contact between the connection elements and the substrate connection tracks on which the components are disposed. For wire bond connection purposes, the connection elements preferably have partial surfaces that are preferably oriented parallel to the substrate but are not surrounded by the housing.

Such connection conductors are likewise disclosed in German Patent DE 43 25 942 C2, which proposes that the connection conductors be bent multiple times at an angle of less than 90° over their course inside the housing, for the sake of greater stability of the connection conductors, which are injected into the housing, to vibrations that occur in wire bonding.

It is a disadvantage of the prior art that in the references cited, the connection elements are injected into the housing. On the one hand, this means that for various configurations of connection elements, various different housings must be kept in inventory. Furthermore, the plastic shrinks during the cooling-down phase of its manufacture. As a result, the strength of the anchoring of the metal connection elements in the plastic is inadequate. Yet this strength is definitive for the quality of the wire bond connection between the partial face of the connection element and the connection tracks of the substrate, since the wire bonding, because of the vibration that is characteristic of it, requires stable supported surfaces.

SUMMARY OF THE INVENTION

One object of the present invention is to introduce a housing for power semiconductor modules in which the connection elements are permanently fixed in the housing, with minimal mobility toward and away from the substrate, and which can be flexibly equipped with connection elements.

The housing surrounds at least one electrically insulating substrate, with metal connection tracks disposed on the substrate and insulated from one another, and having power semiconductor components disposed on the connection tracks. This housing comprises a plurality of parts; at least one cap, and at least one framelike housing part that forms the side walls. This framelike housing part in turn comprises at least one main frame as well as at least one locking frame. The main frame has guides for receiving connection elements formed in or on the locking frame. The connection elements are associated with the substrate and have at least one partial face in the form of a connection tab extending parallel to the substrate. These connection tabs furthermore have at least one stop face which rests on abutments of the main frame to prevent movement of the connection element away from the substrate. At least one locking frame is disposed relative to the main frame in such a way that the locking frame rests at least partly on the connection tabs of the connection elements to prevent movement of the connection elements associated with the substrate.

Because of this embodiment of the housing of a power semiconductor module, it is assured regardless of the production process of the housing itself, that the connection elements are mechanically fixed and stable inside the housing. A further advantage of this inventive embodiment of the housing is that only those guides of the main frame that are also required for the particular circuit arrangement that is located on the substrate can be equipped with connection conductors. Thus, with a single housing, power semiconductor modules suitable for various different functions can be produced.

Another advantage is that the locking frame serves as bracing for the connection tabs. The connection tabs are partial faces of the connection conductors in the interior of the housing, at which faces the wire bond connections to the connection tracks of the substrate or the semiconductor components originate. This is advantageous because an opposing force is presented to the forces that act upon the connection tabs in the direction of the substrate while the wire bond connection is being made. Thus, the housing of the invention makes flexible design possible, while maintaining mechanical stability in terms of the position of the connection elements.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1shows a power semiconductor module with a housing according to the invention, in an oblique top view. The housing10surrounds two substrates40, with metallized surfaces structured appropriately for the circuitry disposed on them. These surfaces act as connection tracks41and are connected by soldering to power semiconductor components50disposed on them. This power semiconductor component50also has wire bond connections80, shown only in part for the sake of simplicity, for electrically connecting the power semiconductor components50and/or the connection tracks41to connection elements30,32. These connection elements serve to provide external connection for the power semiconductor module. To that end, the power semiconductor module has load connection elements30as well as auxiliary and control connection elements32. The housing furthermore has two recesses140for screw connection to a heat sink142(shown in phantom inFIG. 1).

The housing10has a framelike part12, which in turn comprises both a main frame120and two locking frames130. The main frame120has guides122,128for positioning the connection elements30,32. There are three guides122on each of the two long sides for the load connection elements30, which on their end toward the substrate40each have a connection tab310for the disposition of bond wires80for connection to the power semiconductor components50and/or connection tracks41. These connection tabs310rest on the locking frame130, in order to assure a mechanically stable position of the connection tabs310during the production of the wire bond connections80. Locking frame130is furthermore connected to associated recesses126of the main frame120by lugs and, like the main frame, rests on the base plate. In the circuit topology shown, all the guides122are equipped with load connections30. In other circuit topologies, if they allow it, one or more of the guides122might not be so equipped.

On each of the two short sides of the housing10there are four guides128for auxiliary and control connection elements32, which likewise on their end toward the substrate40each have one connection tab320for the disposition of bond wires80for connection to the power semiconductor components50and/or to the connection tracks41. These connection tabs320likewise rest on the locking frame130. In the circuit topology shown, six auxiliary and control connection elements are required, which means that two guides128aare not equipped with auxiliary and control connection elements32.

FIG. 2shows a section through the main frame along the long side of the housing of the invention shown inFIG. 1. The complete housing10is formed by the cap14and a framelike housing part12, which in turn is formed of the main frame120and the locking frame130. The lower closure of the power semiconductor module is formed by the base plate70. The main frame120is partly disposed on the base plate70and partly projects beyond it, surrounding the base plate. The main frame120also has guides122for positioning the load connection elements30. Abutments124are disposed in these guides, as stops for stop faces312of the load connection elements30. It is thus assured that movement of the load connection elements toward the base plate and away from the substrate is prevented.

A locking frame130is also shown connected flush with the main frame120by means of lugs132disposed on the locking frame and associated recesses126of the main frame. Alternatively, the connection between the main frame120and the locking frame130can be accomplished by adhesive bonding.

The locking frame130likewise rests flush on the base plate70. The connection tabs310of the load connection elements30rest on the side of the locking frame130opposite to the substrate or base plate70and thus prevents movement of the load connection elements30in the direction of the base plate70or substrate.

The auxiliary and control connection elements32are fixed analogously by means of both the main frame120and the locking frame130.

Thus, by means of the connection of the main frame120with the locking frame130, the housing10with connection elements30,32disposed therein may be mounted to the base plate70despite mechanical stresses which may be imparted thereto during wire bonding.

FIG. 3shows an exploded view of the housing of the invention ofFIG. 1. The main frame120is shown with guides122, disposed in its interior, for load connection elements30and guides128for auxiliary and control connection elements32. Abutments124are again provided inside the guides30; they act as a stop for both stop faces312of the load connection elements30and, after assembly, effectively prevent movement of these connection elements in the direction away from the base plate. Analogously, the guides128of the auxiliary and control connection elements32likewise have abutments as a stop for the curved stop faces322of the auxiliary and control connection elements32. As a result, movement of the auxiliary and control connection elements32in the direction away from the base plate is also effectively prevented.

Movement of all the connection elements30,32in the direction of the base plate is effectively prevented by the two locking frames130. These locking frames include lugs which latch into associated recesses126. The movement is prevented by the fact that the connection tabs310,320of all the connection elements rest flush on the side of the locking frames remote from the base plate.