Semiconductor module with switching components and driver electronics

A semiconductor module comprises at least one semiconductor chip having at least one semiconductor switch. The at least one semiconductor chip is arranged on a carrier substrate. At least one driver component drives the at least one semiconductor switch. The at least one driver component is arranged on a circuit board. The at least one driver component has at least one input for receiving a control signal. The circuit board has a galvanic isolation in a signal path between the at least one driver component and the at least one semiconductor chip.

BACKGROUND

The present invention relates to the field of power semiconductor modules, with switching semiconductor components and the driver electronics necessary for operating the switching semiconductor components.

Power semiconductor modules are typically embodied as standard modules or as IPM (“intelligent power module”). Both types comprise one or a plurality of power semiconductor chips with one semiconductor switch or else with a plurality of semiconductor switches which are connected up to form half-bridges or three-phase bridges (“six packs”). The driver electronics necessary for the operation of the semiconductor switches are already integrated in IPMs. In contrast thereto, the driver circuits in standard modules have to be provided by the user. In both cases, including if IPMs are used, it is necessary, if the module is intended to be connected to external electronic components (e.g. control electronics), for a galvanic isolation between the power semiconductor module and the external electronic components to be provided by the user for safety reasons.

If, as in IPMs, a driver circuit is integrated in the power semiconductor module, then the user has an advantage only when the galvanic isolation of power section, i.e. the chips with the power semiconductor switches, and driver circuit is embodied in such a way that an application-specific microcontroller or a similar controller can be connected directly to the module, without additional galvanically isolating transfer paths having to be provided. However, this would necessitate a reliable galvanic isolation within the semiconductor module, which has not been achieved with conventional IPM components.

The area requirement for the integration of a galvanic isolation would be so large that conventional semiconductor modules with integrated galvanic isolation between power section and driver circuit would attain external dimensions such that they would become unwieldy and unsuitable for practical requirements. Consequently, there is a need for power semiconductor modules with an improved integrated galvanic isolation.

SUMMARY

According to an exemplary embodiment, a semiconductor module comprises at least one semiconductor chip having at least one semiconductor switch. The at least one semiconductor chip is arranged on a carrier substrate. At least one driver component drives the at least one semiconductor switch. The at least one driver component is arranged on a circuit board. The at least one driver component has at least one input for receiving a control signal. The circuit board has a galvanic isolation in a signal path between the at least one driver component and the at least one semiconductor chip.

DETAILED DESCRIPTION

FIG. 1shows a basic block diagram of a power semiconductor module1in accordance with one exemplary embodiment of the invention. Three blocks44,45and46are arranged in the power semiconductor module1. In this case, the block44has one or a plurality of driver circuits with a driver component7. The block45ensures galvanic isolation between the driver circuit and a power section arranged in block46. The galvanic isolation (block45) can be integrated in the driver component7or in a circuit board9, on which the driver component7is mounted. The block46accommodates the power section, which, in this example, comprises four semiconductor chips2and3each having a power semiconductor switch, which are connected to form a half-bridge circuit. Furthermore, a free-wheeling diode (not illustrated) can be connected in parallel with each transistor. These freewheeling diodes can be arranged either in each case in a separate chip or together with the respective transistor in a common chip.

An application-specific circuit board11as further circuit block69can be connected to the semiconductor module1. Said circuit block69can accommodate, e.g., a microcontroller as a control unit. The application-specific circuit board11can interact with an interface53of a superordinate electronic device.

FIG. 2shows a cross section through a semiconductor module1in accordance with one exemplary embodiment of the invention. The semiconductor module1has at least one semiconductor chip2arranged on a carrier substrate6, e.g. a DCB substrate. In this embodiment of the invention, four semiconductor chips2,3,4and5are applied on the carrier substrate6, and form a full-bridge circuit. The freewheeling diodes are not illustrated separately in this example. If, as mentioned above, the freewheeling diodes are arranged in separate chips, this results in a total number of eight semiconductor chips in the module.

Furthermore, the semiconductor module1has at least one driver component7arranged on the circuit board9. In this example, two driver components7and8drive in each case a half-bridge, wherein the first half-bridge is formed by the chips2and3and the second half-bridge is formed by the chips4and5. This circuit arrangement, too, should merely be understood as an example. It is also possible to provide a dedicated driver component for each individual transistor. The circuit board9and the DCB substrate6are electrically connected to one another by at least one conductive connecting web via which the driver signals (gate signals) generated by the driver components7,8are coupled to the control terminals of the power components.

The semiconductor module1can furthermore have a covering10. The circuit board9additionally comprises connecting elements41and42and contact pins29,30for connecting the circuit board9to an application-specific circuit board not shown here (cf. reference symbol11inFIG. 1).

The semiconductor module1has a housing12configured in such a way that the carrier substrate6and the circuit board9can be arranged one above another. The circuit board9has a galvanic isolation between the electrical control terminals provided for the user and the circuit chips2to5(i.e. the power section). Control signals passed to the driver components7and8are transferred by means of contactless coupling to the semiconductor chips2to5. For this purpose, either the circuit board9has a plurality of electrically conductive wiring layers18,19and20which are electrically insulated from one another and which form coreless transformer loops, or the driver components7themselves contain a coreless transformer (constructed for example with the aid of planar coils). The coreless transformer of the circuit board9or of the driver components7and8enable a contactless, inductive coupling between the electrical terminals of the module that are accessible to the user and the power semiconductor chips2to5.

The circuit board9with the driver components7and8arranged thereon, said circuit board being arranged above the power section (chips2to5), enables a compact, area-saving construction of the semiconductor module1. For this purpose, the circuit board9can have a patterned metal coating forming conductor tracks on the top side16. Moreover, the circuit board9, as mentioned above, has a multilayer lateral wiring with vertical “buried” connecting vias17for connecting the wiring layers18,19and20to the driver components7and8. In this context, “buried” connecting vias17are understood to be vertical connecting lines (vias) which do not form through contacts through the circuit board9, but rather end on one of the inner wiring layers18,19or20. Three wiring layers18,19or20are provided in the present example. Of course, more or fewer wiring layers can also be provided depending on the requirements of the application.

On account of the buried connecting vias17, the underside21is free of connecting vias and can be provided either with an insulation layer, an electrically conductive layer, a shielding layer or a thermally insulating layer. A thermally insulating layer protects the driver components7and8against the evolution of heat of the power section of the semiconductor module1arranged underneath.

The semiconductor module1can be fixed with its carrier substrate6on a heat sink39. For this fixing, the semiconductor module1can have a central screw connection27, for example, which presses the covering10onto the module housing. In this case, the heat sink39is pressed onto the substrate6by its top side49by means of the screw connection27. In addition to the advantages of saving space and area reduction already mentioned above, the semiconductor module1has the advantage of simple exchangeability of defective components.

A method for producing a semiconductor module1begins with producing a cavity housing12with a housing frame22, wherein the housing frame22has a plurality of mounting shoulders24,25and26. Furthermore, a carrier substrate6with at least one power semiconductor chip2, and in this exemplary embodiment four power semiconductor chips2,3,4and5, is produced. Afterward, the carrier substrate6is applied to the first, lower mounting shoulder24of the housing frame22and the power semiconductor chips2,3,4and5are embedded into a soft potting compound15. When applying the carrier substrate6to the first, lower mounting shoulder24, the supply lines43in the form of lead ends are connected to an upper patterned metal layer60of the carrier substrate6by ultrasonic welding. In addition to ultrasonic welding, soldering or spot or laser welding are also possible as connecting techniques.

A circuit board9with driver components7and8on its top side16is furthermore produced. For this purpose, the circuit board9is arranged on a second mounting shoulder25above the first mounting shoulder24. Finally, a covering10with a central hole51is produced and a heat sink39having a central threaded hole52is provided. The covering10can then be applied on an upper, third mounting shoulder26above the second mounting shoulder25.

By means of a screw connection27through the central hole51, which the circuit board9and the carrier substrate6have as well, the covering10is mechanically connected to the threaded hole52of the heat sink39. The screw connection27provides for sufficient pressure of the heat sink39on the carrier substrate6. However, the substrate need not necessarily have a hole. Depending on the application, it is also possible for a plurality of substrates to be arranged in the module in such a way that there is space for the screw between them. The frame construction ensures the correct force distribution.

Instead of a central screw connection27, it is also possible to fix the circuit board9and the covering10on the shoulders25and26, respectively, of the housing frame22by means of corresponding adhesive bonding or soldering methods, but this would make it more difficult to disassemble the semiconductor module or to exchange damaged components.

FIGS. 3 to 10show cross sections through components during the production of the semiconductor module1in accordance withFIG. 2. Components having the same functions as in the previous Figures are identified by the same reference symbols and are not discussed separately.

FIG. 3shows a cross section through a housing12. The housing12has an interior space54surrounded by walls55and56, which form the housing frame22. An interior wall57of the interior space54is structured in such a way that three mounting shoulders24,25and26are produced, on each of which components of the semiconductor module1are arranged.

The material of the housing frame22can be a ceramic or a plastic, wherein vertical leads33and horizontal or lateral leads34are provided within the ceramic or the plastic of the housing frame22. The vertical leads33merge into contact pins31and32on the upper edge28of the housing12. The lateral or horizontal lines34merge into leads43of the housing12and project into the interior space54in the region of the first, lower shoulder24. A cavity housing12of this type can be molded by means of a plastic injection-molding technique or be pressed by means of a ceramic sintering method.

FIG. 4shows a schematic cross section through a carrier substrate6of the semiconductor module1, wherein the carrier substrate6has on its top side58a patterned metal coating60, on which power semiconductor chips2,3,4and5are fixed with their rear sides40. The carrier substrate6can comprise a ceramic or metal plate if particularly high powers are to be switched by the power semiconductor chips2,3,4and5. In other cases, the carrier substrate6can also have a plastic plate. The rear sides40of the power semiconductor chips2,3,4and5can be provided with a rear side coating prior to application to the carrier substrate6, said coating having a substance from the group aluminum, gold, silver or palladium/gold or alloys thereof. The power semiconductor chips2,3,4and5themselves are produced from a silicon single-crystal wafer in this embodiment of the invention.

In order to achieve a cohesive connection between the power semiconductor chips2,3,4and5and the patterned metal layer60of the carrier substrate6, a die bonding method is often used. For the die bonding method, solder materials can be applied to a solderable surface region of the carrier substrate6or to the solderable rear sides40of the power semiconductor chips2to5, for example as solder paste.

The patterned metal coating60has chip islands for the rear sides40of the power semiconductor chips2,3,4and5and contact pads for connecting elements to the top sides61of the power semiconductor chips2,3,4and5. A patterning of the metal coating60on the carrier substrate6can be effected by dry or wet etching methods in which a resist mask protects the patterned metal coating60to be formed. Finally, such a resist mask is removed after the dry or wet etching method. A resist etching mask of this type is not necessary if the metal coating60is patterned by means of a laser beam or by means of printing methods such as screen printing methods, stencil printing methods or jet printing methods.

In this exemplary embodiment of the invention, the power semiconductor chips2,3,4and5are arranged alongside one another on the carrier substrate6and form a full-bridge circuit comprising two half-bridge circuits with the power semiconductor chips2and3and, respectively,4and5. In order to save further space, it is also possible to arrange the half-bridge chips2and3and, respectively, also the chips4and5of the second half-bridge circuit compactly in a manner stacked one above another in such a way that a full-bridge circuit comprising half-bridges arranged alongside one another is realized in a very confined space.

FIG. 5shows a schematic cross section through the housing12in accordance withFIG. 3after fitting the carrier substrate6in accordance withFIG. 4on the lower, first shoulder24of the housing frame22, such that the underside59of the carrier substrate6forms a coplanar area with the underside23of the housing frame22. By means of ultrasonic welding (as an alternative also soldering or laser welding), the leads43of the housing frame22can be electrically and mechanically connected to the metal coating60on the top side58of the carrier substrate6. The carrier substrate6is thus held on the shoulder24of the housing frame22. In order to improve the thermal transfer, the underside59of the carrier substrate6can also be provided with a metallic coating62.

FIG. 6shows a cross section through a circuit board9with driver components7and8. The driver components7and8are arranged on the circuit board9for a respective semiconductor bridge circuit. The circuit board9has on its top side16a patterned metal coating63, which can be patterned in an analogous manner to the metal coating60of the top side58of the carrier substrate6. Alongside the driver components7and8, connecting elements41and42are arranged on the top side16of the circuit board9, which connecting elements can be connected via plug connectors29,30to an application-specific circuit board which is described below and which is not shown here.

The underside21of the circuit board9can have an insulation layer, a patterned metal layer or a thermally insulating layer in order also thermally to isolate the power section of the semiconductor module from the region of the driver components7and8. The circuit board9has a plurality of wiring layers18,19and20, which are insulated from one another and can be electrically connected only by blind connecting vias17extending from the top side16as far as at most the lower wiring layer20.

The underside21is not reached by such “buried” connecting vias17. In this case, the wiring layers18,19and20can be arranged in a ceramic material or in a plastic material. The metal layers of the wirings18,19and20can be configured in such a way that they form coupled planar coils, that is to say a planar coreless transformer, such that control signals of the driver components7and8can be transferred contactlessly, i.e., in a galvanically isolated fashion, to the power semiconductor chips2,3,4and5of the carrier substrate6.

FIG. 7shows an enlarged cross section through a circuit board9with “buried” connecting vias17in the vertical direction, which connect the lateral wiring layers18,19and20to one another, while the underside21of the circuit board9is not contact-connected by the vertical buried connecting vias17.

FIG. 8shows a cross section through the housing12in accordance withFIG. 5with an introduced circuit board9in accordance withFIG. 6and a heat sink39and also a covering10prior to assembly to form a semiconductor module. In this case, the circuit board9is positioned with its underside21on the second, central shoulder25of the housing frame22, thereby achieving a galvanic isolation between the power section, which is arranged on the carrier substrate6, and the control electronics arranged on the top side16of the circuit board9with the driver components7and8. An electrical connection to an application-specific circuit board is possible via the connecting elements41and42and the contact pins29,30. The covering10is dimensioned in such a way that it fits onto an upper shoulder26of the housing frame22.

Finally, the covering10has a central hole51arranged congruently with respect to a corresponding central hole of the circuit board9and the carrier substrate6. A screw connection27is inserted through this central hole51in this embodiment of the invention, the thread attachment66of said screw connection corresponding to a threaded hole52of the heat sink39. As a result, the substrate6is pressed onto the heat sink in the course of mounting. A suitable heat conducting material can be provided between heat sink and module in order to improve the heat dissipation.

FIG. 9shows a schematic cross section through the assembled semiconductor module1in accordance withFIG. 8and an application-specific circuit board11for such a semiconductor module1. After the covering10has been applied (i.e. adhesively bonded) to the upper mounting shoulder26of the housing frame22, the heat sink39can be screwed together with the module and thus be thermally connected by its top side49to the underside59of the carrier substrate6.

The heat loss occurring in the power section can therefore be dissipated via the heat sink39. Moreover, the covering10is fixed on the third, upper mounting shoulder26of the housing frame22in such a way that the through openings64and65correspond to the connecting elements41and42on the circuit board9. The pins31and32projecting from the upper edge28of the housing frame22can on the one hand serve as electrical or thermal (“thermal bridge”) connection and on the other hand be used as fitting pins.

The application-specific circuit board11shown above inFIG. 9has openings for receiving the contact pins29and30and thus enabling an electrical connection to the circuit board9. Moreover, the application-specific circuit board11has openings67and68corresponding to the pins31and32of the housing frame22. Both the top side38of the application-specific circuit board11and the underside37can be populated with components35and36, respectively, and perform the controller or control logic functions of the block47, as illustrated inFIG. 1. For this purpose, the components35and36can be surface-mountable components. Moreover, the application-specific circuit board11can have supply voltage leads and switching pulse leads.

FIG. 10shows a schematic cross section through the semiconductor module1with applied application-specific circuit board11. For this purpose, the application-specific circuit board11is placed with its openings67and68in an accurately fitting manner onto the pins31and32of the housing frame22, such that the contact pins29and30of the module can simultaneously make contact with the application-specific circuit board11. The application-specific circuit board11can also be provided with interface contacts (not shown) at its edges in order to connect the semiconductor module1to a superordinate device.

Although various examples to realize the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. Such modifications to the inventive concept are intended to be covered by the appended claims.