POWER SEMICONDUCTOR MODULE COMPRISING SWITCH ELEMENTS AND DIODES

A power module (1) comprises a first switch (2) comprising a first switch element (9) and an associated first diode (10), a second switch (3) comprising a second switch element (11) and an associated second diode (12), the first and second switches (2, 3) being electrically connected to form a half-bridge, wherein the switch elements (9, 11) and diodes (10, 12) are located next to each other, wherein the second switch element (11) and second diode (12) are located between the first switch element (9) and the first diode (10).

The present disclosure relates to a power module comprising first and second switches, each switch comprising at least one switch element and an associated diode. The switches are connected to form a half-bridge. A half-bridge is an electric circuit comprising two switches connected in series between a DC+ and DC− terminal, wherein an AC terminal is connected between the switches. The switch connected to the DC+ terminal is denoted as high side (HS) switch, the switch connected to the DC− terminal is denoted as low side (LS) switch.

Half-bridge power modules form the key building blocks in various power electronic devices, such as motor drives or power converters which can be used in electric vehicles (EV). Power modules need to be compact and designed to operate in harsh environments for a long period of time. The power modules may comprise silicon (Si), silicon carbide (SiC), gallium nitride (GaN) or other semiconductor elements. Three half-bridge power modules form a so-called six-pack power module, forming the three phases of an inverter. The electromagnetic design of the switches is crucial for exploiting the fast switching capabilities of the device.

Documents WO 2010/004802 A1 and WO 2013/171996 A1 disclose different power module layouts. Document EP 3 246 945 A1 discloses a power module with three DC terminals arranged with alternating polarity for reducing the contribution of the terminals to stray inductance of the power module.

Document JP 2005 216876 A discloses a power module with an arrangement of high side and low side IGBTs and diodes such that wires are arranged in parallel and wiring inductances are reduced by electric currents flowing in a reverse direction. Documents EP 3 613 077 B1 and US 2011/062491 A1 disclose further half-bridge power modules.

Embodiments of the disclosure relate to a power module with improved electromagnetic properties.

According to an embodiment, a power module comprises a first switch comprising a first switch element and an associated first diode and comprises a second switch comprising a second switch element and an associated second diode. Each of the switch elements is electrically connected in parallel to its associated diode. The first and second switches are electrically connected to form a half-bridge. The switch elements and diodes are located next to each other, wherein the second switch element and second diode may be located between the first switch element and the first diode.

The power module may be a Si, or a wide-bandgap module such as a SiC or GaN module, for example. The switch elements may be insulated gate bipolar transistors (IGBT), as an example. The switch elements may be alternatively MOSFET or MISFET transistors, for example. The associated diodes may be free-wheeling diodes (FWD). A switch element is electrically connected with its associated diode such that the associated diode is connected between collector and emitter of the switch element. In this way, current can be conducted via the diode in one direction.

In an embodiment, the first switch is an HS switch, connected to a DC+ terminal. The first switch element and the first diode are in this case called HS switch element and HS diode, respectively. The second switch is an LS switch, connected to a DC− terminal. The second switch element and the second diode are in this case called LS switch element and LS diode, respectively.

In an alternative embodiment, the first switch is an LS switch and the second switch is an HS switch.

The arrangement of the switch elements and diodes next to each other in the specified order is symmetric in the sense that the order of sides to which the components are attributed is the same in both directions. This enables reducing stray inductance. Furthermore, also the lengths of commutation paths between a switch element, the diode of the other side and a DC terminal can be confined, which reduces the inductance of loop currents.

In an embodiment, the first switch element is located next to the second diode and the first diode is located next to the second switch element. Accordingly, the switches and diodes of different sides are located next to each other, leading to short commutation paths. In some embodiments, the second switch element is arranged closer to the first diode than the associated second diode.

The power module may comprise at least three DC terminals located on the same side of the power module, wherein the DC terminals have alternating polarity. As an example, the layout of the terminals may be DC+/DC−/DC+. Alternatively, the layout of the terminals may be DC−/DC+/DC−. It is also possible that the power module has further DC terminals of alternating polarity on the same side. The power module may comprise an AC terminal located on a side opposite to the DC terminals.

The power module may comprise metallizations. The metallizations may be in the form of DC+, DC− and AC metallizations connected to the respective terminals. The switch elements and diodes may be located on the DC+ and AC metallizations. The metallizations may be arranged in the form of strips parallel to each other.

In embodiments, each of the first and second switches comprises several switch elements and associated diodes connected in parallel to other switch elements and associated diodes of the same switch. Each of the switches may comprise an odd number of switch elements and associated diodes. As an example, each of the switches may comprise three switch elements and associated diodes.

The power module may have a highly symmetric layout. As an example, the switch elements of the same switch may be located in a row. The switch elements may be located at regular distances. Also the associated diodes of the same switch may be located in a row. Each of the switch elements of the same switch may be located on the same metallization. Also each of the associated diodes may be located on the same metallization.

In embodiments, the power module comprises additional first switch elements, associated additional first diodes, additional second switch elements and associated additional second diodes, located in the same column as the first and second switch elements and associated diodes. The additional switch elements and diodes may be arranged in the same order as the first and second switch elements and diodes. The additional switch elements and diodes can also be arranged in an opposite order than the first and second switch elements and diodes. The additional first and second switch elements and associated diodes may be electrically connected in parallel to the first and second switch elements and associated diodes.

Accordingly, the pattern of switch elements and diodes is repeated along the column. In addition to that, the switches may comprise further switch elements and diodes arranged in the same row of first and second switch elements and diodes.

The present disclosure comprises several embodiments. Every feature described with respect to one of the embodiments is also disclosed herein with respect to the other embodiment, even if the respective feature is not explicitly mentioned in the context of the specific embodiment.

FIG.1shows a schematic circuit diagram of a power module1in form of a half bridge. The power module1may be used in a motor drive or power converter in an electric vehicle, for example.

The power module1comprises a first switch2and a second switch3connected in series between two DC+/− terminals4,5with an AC terminal6connected between the switches2,3.

When providing a voltage between the DC+/− terminals4,5and alternatingly switching on and off the switches2,3at gate terminals7,8, an AC voltage is generated at the AC terminal6.

The first switch2comprises a first switch element9and an associated first diode10. The first diode10is connected between an emitter and a collector of the first switch element9. The second switch3comprises a second switch element11and an associated second diode12, which is connected between an emitter and a collector of the second switch element11. The switch elements9,11may be insulated-gate bipolar transistors (IGBT). The diodes10,12may be free-wheeling diodes (FWD). The first switch2is in this case directly connected to the DC+ terminal and is also called “high side” (HS) switch. The first diode10and the first switch element9are called HS diode10and HS switch element9, respectively. The second switch3is in this case directly connected to the DC− terminal and is also called “low side” (LS) switch. The second diode11and the second switch element12are called LS diode and LS switch element, respectively.

It is also possible that the first switch2comprises one or more further first switch elements9′ and associated further first diodes10′ connected in parallel to the first switch element9and associated first diode10and the second switch3comprises one or more further second switch elements11′ and one or more associated further second diodes12′ connected in parallel to the second switch element11and the associated second diode12.

The one or more further first switch elements9′ may have the same features as the first switch element9. The same applies for the further second switch elements11′, further first diodes10′ and further second diodes12′ in relation to the second switch element11, first diode10and second diode12, respectively. The first switch element9and further first switch elements9′ are also denoted as first switch elements9,9′, the second switch element11and the further second switch elements11′ are also denoted as second switch elements11,11′ in the following. The first diode10and further first diodes10′ are also denoted as first diodes10,10′, and the second diode12and the further second diodes12are also denoted as second diodes12,12′ in the following.

As an example, an odd number of first switch elements9,9′ and associated diodes10,10′ may be connected in parallel and an odd number of second switch elements11,11′ and associated second diodes12,12′ may be connected in parallel.

During switching, commutation loop currents flow between the first switch2and the second switch3and the associated commutation loop inductance impacts the switching speed.

FIG.2shows an embodiment of a layout scheme of a power module1comprising a half-bridge in accordance with the circuit diagram ofFIG.1. Only first and second switch elements9,11and associated diodes10,12are depicted. The Further first and second switch elements can be present in a corresponding arrangement shifted along a length direction L.

The switch elements9,11and associated diodes10,12are located on metallizations31on a substrate. The metallizations31can also be denoted as “traces”. In particular, the first switch element9and the first diode10are located on DC+ metallizations13,13aand the second switch element11and the second diode12are located on AC metallizations15,15a.In the shown embodiment, the first switch element9and the first diode10are the HS switch element and HS diode, respectively. The second switch element11and the second diode12are the LS switch element and LS diode, respectively.

The switch elements9,11and associated diodes10,12are arranged next to each other in the order: first switch element9—second diode12—first diode10—second switch element12(inFIG.2from bottom to top). As can be seen inFIG.2, between two components located “next” to each other no other switch element or diode is located. The order of the sides of the components (HS-LS-LS-HS) is the same when going from bottom to top or from top to bottom. The elements are arranged in a column along a width direction W of the power module1. The elements located in the column at least overlap along the length direction L or are arranged centered to each other.

In this arrangement, the first switch element9is not located adjacent to the associated first diode10. Instead, the first switch element9and the second diode12are located as a pair close to each other and the second switch element11and the first diode10are located as a pair close to each other. Thus, the switch elements9,11and diodes10,11of different sides are spatially clustered as pairs. This has the effect that a current commutation path16from the first diode10via the second switch element11to a DC− metallization14is spatially well defined and confined. Also a current commutation path17from the first switch element9via the second diode12to the DC− metallization14is spatially well defined and confined. Thereby, the inductance of the commutation loops is minimized.

The two DC+ metallizations13,13aare on the same electric potential but may be connected to separate terminals. The two AC metallizations15,15aare on the same AC potential. The AC metallizations15,15amay be connected to a single terminal.

FIG.3shows a top view of an embodiment of a power module1with the layout scheme ofFIG.2arranged on a substrate18.

In the shown embodiment, three first diodes10,10′,10″ are located next to each other on the same DC+ metallization13, associated to three first switch elements9,9′,9″ located next to each other on the further DC+ metallization13a.

Three second diodes12,12′,12″ are located next to each other on the same AC metallization15, associated with three second switch elements11,11′,11″ located next to each other on the same, further AC metallization15a.Accordingly, the embodiment has three switch elements and associated diodes per side. The switch elements and associated diodes are located at regular distances only shifted relative to each other along the length direction L. The diodes and switch elements of each side are located next to each other along a length direction L on the same metallization, corresponding to a parallel connection of several first switches and a parallel connection of several second switches in the circuit diagram ofFIG.1. The shown arrangement of diodes and switch elements is very regular and, thereby, a balanced distribution of loads and losses for the diodes and switch elements can be achieved.

While the layout scheme shows three diodes and switch elements per side located on the same metallization, more or less than three diodes per side may be present. In embodiments, only a single diode and a single switch element per side may be present.

The AC metallizations15,15aare connected to a single AC terminal6. The DC+ metallizations are connected to two separate DC+ terminals4,4′ instead of the single terminal4shown inFIG.1. The DC+ terminals4,4′ enclose a DC− terminal5and are located at a side opposite than the AC terminal6.

Each of the switch elements9,9′,9″,11,11′,11″ and each of the diodes11,11′,11″ and12,12′,12″ is connected to an adjacent DC+, DC− or AC metallization13,13a,14,15,15a,by wire bonds19. In this embodiment, also the wire bonds19are homogeneously directed along the width direction W. Overall, a very lean layout of metallizations and connection structures is achieved. Thereby, the chip placement area can be maximized and heat spreading can be increased.

FIG.4shows in a detailed view of a gate metallization layout of the embodiment ofFIG.3. The position of the detailed view is indicated inFIG.3by dashed lines.

Gates20,20′,20″ of the second switch elements11,11′,11″ are connected to a gate metallization21arranged between the first DC+ metallization13and the first AC metallization15. As can be seen fromFIG.3, the gates of the first switch elements9,9′,9″ are connected to a second gate metallization22located between the second DC+ metallization13aand an edge of the substrate18. Depending on the overall layout, the second gate metallization22may be alternatively located between the second DC+ metallization13aand the second AC metallization15a,corresponding to the position of the first gate metallization21. As can be seen, a very lean layout of gate metallizations is achieved.

FIG.5shows in a detailed view an example of an alternative gate metallization layout which can be embodied in the power module1ofFIG.3instead of the gate metallization layout shown inFIG.4. InFIG.5, the first gate metallization21is located on the DC− metallization. As inFIG.4, the first gate metallization21is in the form of an elongate strip, arranged in parallel to the DC+, DC− and AC metallizations.

FIGS.6,7,8and9show further layouts of embodiments of power modules1.

FIG.6shows a layout of a power module1, in which, compared toFIG.3, the locations of the second switch element11and the second diode12have been swapped. Also in this case, the arrangement of the diodes and switches along the length direction L is homogenous. Thereby, a balanced distribution of loads and losses for the diodes and switches within the sides is achieved.

In contrast to the embodiment ofFIG.2, the switch elements9,11of different sides are arranged close to each other and the diodes10,12of different sides are arranged close to each other. The switch elements9,11are arranged at a distance from the associated diodes10,12. The pairs of switch elements9,11are separated by an AC metallization15from the pairs of the diodes10,12.

The metallizations13,13a,14,15,15aare elongated strips arranged parallel to each other in a single row. Also here, in case of several switches per side, the further sets of switch elements and diodes of the switches are positioned on along the respective metallization at regular distances in a row, i.e., along the length direction L.

The switch elements9,11can be connected to gate metallizations arranged adjacent to the AC metallization15and DC+ metallization13, respectively. As an example, a first gate metallization for connection to the HS switch element11may be located at the side of the DC+ metallization13afacing away from the AC metallization15a. A second gate metallization for connection to the LS switch element9may be located adjacent to the AC metallization15, e.g., between the DC+ metallization13and the AC metallization15. The second gate metallization may be alternatively located on the DC− metallization14.

The relative arrangement of the further switch elements9′,9″,11′,11″ and further diodes10′,10″,12′,12″ is the same but only shifted along the length direction L.

FIG.7shows a further layout of a power module1. In this embodiment, the DC− metallizations and associated terminals are not arranged in a ‘+/−/+’-scheme (from top to bottom in the figure) but are arranged in a ‘−/+/−’-scheme.

In this embodiment, the first switch element9and the first diode10are parts of the HS switch and the second switch element11and the second diode12are part of the LS switch. Also here, the order of the sides (HS-LS-LS-HS) is the same when going from bottom to top or from top to bottom. The second switch element11and the second diode12are located close to each other on the same DC+ metallization13at different positions along the width direction W. The first switch element11and the associated first diode12are arranged close to each other. However, the first switch element9and the associated diode10are separated from each other by the DC+ metallization13and the second switch element11and the second diode12. Also in this embodiment, the commutation path16from the second diode12via the first switch element9to the DC− metallization14and also the commutation path17from the second switch element11via the first diode10to the DC− metallization14ais short and the inductance is low.

As in the previous embodiments, the first set of switch elements9,11and associated diodes10,12of the switches are arranged at the same positions along the length L of the power module1. The second set of switch element9′,11′ and associated diodes10′,12′ is arranged identically but only shifted along the length direction L. Also the third set of switch elements9″,11″ and associated diodes10″,12″ is arranged identically but only shifted along the length direction L.

FIG.8shows a further layout of a power module1. In comparison to the layout ofFIG.7, the positions of the second switch elements11,11′,11″ and the positions of the associated diodes12,12′,12″ are swapped. Also in this case, a balanced load and loss distribution can be obtained.

FIG.9shows a further layout of a power module1. In this embodiment, the DC-metallizations and associated terminals are arranged in a ‘−/+/−/+/−’-scheme along the width direction W.

The shown embodiment is obtained when the layout scheme shown inFIG.8is doubled in the width direction W, with a shared DC− terminal14a.Accordingly, the power module1comprises a first set of switches forming a half-bridge, the first set comprising first and second switch elements9,11and associated diodes10,12and a second set of switches comprising additional switch elements9a,11aand associated additional diodes10a,12a.Due to a separation of the respective metallizations within the power module1, the parallel connection may be established when the module terminal is further connected, to an inverter, for example.

Further sets of identically arranged switches are located at positions shifted along the longitudinal direction L, exemplarily at regular distances from each other.

Accordingly, the layout is symmetric in regard of the arrangement of the switch elements and diodes in a direction along the metallizations. Exemplarily, the switch elements and diodes of each side are merely shifted along the metallization direction but the layout does not change along the metallization.

Simulations of the layout shown inFIG.3show that mutual coupling inductances for each switch element between the associated commutation loop and gate loop are negative and well-balanced and, thus, a proper dynamic current sharing can be accomplished. In addition to that, the switching behavior at a simulated turn-off of switch elements and turn-on on diodes for all three switch elements is well-aligned and, thus, a good balance is accomplished between switch elements of the switches. Also the switching behavior of the diodes is well-balanced.

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