The invention relates to a power-module.

A conventional power-module may comprise a carrier and one or more semiconduc- tor chips mounted on the carrier. At least one of the semiconductor chips may be a high-power semiconductor chip and/or a semiconductor switch. The high-power sem- iconductor chip may be configured for processing high voltages, for example of more than 100 V, and/or high currents, for example of more than 10 A. The semiconductor chips each may comprise a semiconductor die. The semiconductor die may comprise SiC, GaN, or GaO.

The carrier may comprise a direct bonded copper (DBC) substrate or an insulated metal substrate (IMS). The carrier may comprise one or more terminals for electri- cally coupling the semiconductor chips to one or more external devices and/or one or more signal pins for electrically coupling the semiconductor chips to a driver board of the power-module.

Optionally, the power-module comprises the driver board for driving the semiconduc- tor chips. The driver board may be configured for controlling the semiconductor chips. The driver board may comprise a printed circuit board (PCB). Additionally, one or more electronic components may be arranged on the carrier and/or the driver board. The electronic components each may comprise an active electronic component and/or a passive electronic component. The passive electronic component may com- prise a resistor, a capacitor, and/or a conductor. The active electronic component may comprise a chip and/or a transistor. The active electronic component and/or the semiconductor chips may be configured as high-speed switching devices. The active electronic components and/or the semiconductor chips may be configured as high- power semiconductor devices.

The semiconductor chips may be coupled to the carrier, to each other, and/or to the contact area via one or more wire bonds. The wire bonds may be made of copper, aluminum, or gold. Aluminum has a larger resistance than cooper, leading to more energy losses than copper. The CTE of aluminum is 23x10 ^-6 1/K. A typical CTE of a semiconductor chip may be 2 to 3x10 ^-6 1/K. This large difference may contribute to a short lifetime and/or a bad reliability of the semiconductor chip. Compared to alumi- num, copper has a lower resistance and a lower CTE, i.e. 16x10 ^-6 1/K. This CTE is closer to that of the semiconductor die chip, leading to a longer lifetime and good reli- ability of the power-module. However, copper is harder than aluminum and a surface of the semiconductor chip to be contacted by the corresponding wire bond may be destroyed more easily as when using aluminum. Therefore, it is known in the art to plate or sinter a copper layer, e.g. of about 10 μm to 200 μm, on the corresponding surface of the semiconductor chip as a buffer, leading to increased costs.

Further, high-power semiconductor chips as they are used in the power-modules continuously improve in current density year over year. However, without parallel en- hancements in the thermal stack and the associated bonding and joining technology, significant limitations in harvesting these improvements remain. This is especially true when looking at the potential of SIC or GaN semiconductor chips where higher operating and switching temperatures are limited only by the available packaging technology.

Therefore, it is an object of the present invention to provide a power-module compris- ing at least one semiconductor chip, wherein the power-module enables a high per- formance of the semiconductor chip, contributes to a long life-time and high reliability of the semiconductor chip, and/or may be produced at low costs.

The object is achieved by the subject matter of the independent claim. Advantageous embodiments are given in the dependent claims.

An aspect relates to a power-module. The power-module comprises at least one semiconductor chip and a carrier, on which the semiconductor chip is mounted and which comprises at least one contact area electrically coupled to the first semicon- ductor chip by at least one conductor, wherein the conductor comprises aluminum and copper. Thanks to the mixing of the aluminum and the copper within one conductor, several advantages may be achieved. In particular, the total CTE of the conductor comprising the aluminum and the copper is between the CTE of copper and the CTE of alumi- num. Therefore, the total CTE of the conductor may fit better to the CTE of the semi- conductor chip than the CTE of aluminum only, leading to an increased reliability of the semiconductor chip. In addition, an electrical resistance of the conductor is lower than the electrical resistance of a pure aluminum wire, leading to lower energy losses of the power-module. In addition, a weight of the conductor may be less than the weight of a corresponding copper wire, leading to a light weight of the power-module. Further, the compound material of the conductor is not so hard as copper only. Therefore, the conductor may be used for wire bonding directly and no premeasures have to be taken from the side of the semiconductor chip in order to be able to cou- ple the conductor to the semiconductor chip. Therefore, the costs for the power-mod- ule may be kept relatively low and the design-freedom may be relatively high. In sum, this may lead to a very high reliability and long lifetime of the power-module at the same or lower costs as a conventional power-module, and with the potential for a very high power density.

The power-module may comprise another semiconductor chip. The other semicon- ductor chip may be coupled to the above semiconductor chip and/or the carrier via another conductor being configured as the above conductor. The semiconductor chip(s) may comprise SiC, GaN, or GaO. At least one of the semiconductor chips may be a high-power semiconductor chip and/or a semiconductor switch. The high- power semiconductor chip may be configured for processing high voltages, for exam- ple of more than 100 V, and/or high currents, for example of more than 10 A.

The power-module may comprise a driver board. The driver board may be coupled to one or more of the semiconductor chips and/or the carrier via a further conductor be- ing configured as the above conductors. At least one electronic component may be arranged on the driver board. The electronic component may be configured for driv- ing, i.e., controlling, the semiconductor chip(s). The electronic component may be an active electronic component, e.g. chip or transistor, or a passive electronic compo- nent, e.g. a resistor, capacitor, or an inductor. The driver board may be a printed cir- cuit board. Alternatively, the driver board may comprise one or more direct bonded copper substrates or insulated metal substrates.

According to an embodiment, the conductor comprises a first strand comprising or being made of the aluminum and a second strand comprising or being made of the copper. For example, the conductor is made of the first and second strand. The first strand and the second strand may be fixedly attached to each other.

According to an embodiment, the conductor extends from the semiconductor chip to the contact area and the first strand and the second strand each extend over the whole extension of the conductor. So, the first strand may extend from the semicon- ductor chip to the contact area and/or the second strand may extend from the semi- conductor chip to the contact area. In other words, a length of the conductor may cor- respond to a length of the first strand and/or to a length of the second strand.

According to an embodiment, the first strand and the second strand physically touch each other. In other words, the first strand and the second strand may be in direct physical contact to each other. This may mean in this context, that no other material may be arranged between the first strand and the second strand.

According to an embodiment, the first strand and the second strand physically touch each other over their whole extension, i.e. over their whole length.

According to an embodiment, the first strand is embedded in the second strand. So, the second strand may surround the first strand at least partly, e.g. completely, in a radial direction, i.e. a direction perpendicular to the longitudinal extension of the con- ductor. In this embodiment, an outer surface of the conductor may be formed by the second strand.

According to an embodiment, the second strand is embedded in the first strand. So, the first strand may surround the second strand at least partly, e.g. completely, in the radial direction, i.e. the direction perpendicular to the longitudinal extension of the conductor. In this embodiment, an outer surface of the conductor may be formed by the first strand.

According to an embodiment, the conductor is a wire having a circular cross-section. For example, the first strand may be a wire having a circular cross-section and may be surrounded by the second strand in the radial direction. Alternatively, the second strand may be a wire having a circular cross-section and may be surrounded by the first strand in the radial direction.

According to an embodiment, the conductor is a ribbon having a rectangular cross- section. For example, the first strand may be a ribbon having a rectangular cross- section and may be surrounded by the second strand in the direction perpendicular to the longitudinal extension of the conductor. Alternatively, the second strand may be a ribbon having a rectangular cross-section and may be surrounded by the first strand in the direction perpendicular to the longitudinal extension of the conductor.

According to an embodiment, the conductor is coupled to the semiconductor chip such that the aluminum of the conductor physically touches the semiconductor chip. For example, the first strand may be directly coupled to the semiconductor chip. So, no other material may be arranged between the first strand and the semiconductor chip.

According to an embodiment, the conductor is coupled to the semiconductor chip such that the copper of the conductor physically touches the semiconductor chip. For example, the second strand may be directly coupled to the semiconductor chip. So, no other material may be arranged between the second strand and the semiconduc- tor chip.

According to an embodiment, the power-module comprises at least one further con- ductor, the further conductor coupling the carrier and/or the semiconductor chip to a driver board of the power-module or to an external device and the further conductor being configured as the conductor. In other words, the power-module may comprise further conductors, wherein one or more of these further conductors may be config- ured in accordance with the above conductor and in particular may comprise alumi- num and copper.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. Below, embodiments of the pre- sent invention are described in more detail with reference to the attached drawings.

Fig. 1 shows a cutaway side view of an exemplary embodiment of a power-module.

Fig. 2 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 .

Fig. 3 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 .

Fig. 4 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 .

Fig. 5 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 .

Fig. 6 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 .

The reference symbols used in the drawings, and their meanings, are listed in sum- mary form in the list of reference symbols below. In principle, identical parts are pro- vided with the same reference symbols in the figures.

Fig. 1 shows a cutaway side view of an exemplary embodiment of a power-module 20. The power-module 20 comprises a carrier 22 and at least one first semiconductor chip 24, e.g. two or more semiconductor chips 24, each being arranged on the carrier 22. The power-module 20 may be used in an inverter and/or a rectifier. At least one of the semiconductor chips 24 may be a high-power semiconductor chip. The high-power semiconductor chip may be configured for processing high voltages, for example of more than 100 V, and/or high currents, for example of more than 10 A. The semiconductor chips 24 each may comprise SiC, GaN, or GaO,

The carrier 22 may comprise an electrically conductive first layer 30, an electrically insulating second layer 32 under the first layer 30 (in figure 1 ), and an electrically conductive third layer 34 under the second layer 32. The first, second, and/or third layer 30, 32, 34 may be parallel to each other. The first layer 30 may comprise a first contact area 40 and a second contact area 42, which are spatially and electrically separated from each other and/or electrically insulated against each other. Alterna- tively, the first layer 30 may comprise one, or more than two contact areas. The semi- conductor chips 24 may be arranged on and/or electrically and mechanically coupled to the second contact area 42. For example, the semiconductor chips 24 each may comprise an electrical contact being arranged at a bottom of the corresponding semi- conductor chip 24 and this contact may be electrically coupled to the second contact area 42. The first and/or third layer 30, 34 may comprise or may be made of copper and/or aluminum. The second layer 32 may comprise a dielectric material, e.g. an electrically isolating resin. The carrier 22 may be a direct bonded copper substrate (DBC) or an insulated metal substrate (IMS).

The power-module 20 may further comprise a heat spreader 38. The carrier 22 may be arranged on the heat spreader 38. The heat spreader 38 may be configured for dissipating heat generated during an operation of the power-module 20 away from the semiconductor chips 24. Optionally, an interface material 36, e.g. a Thermal Inter- face Material (TIM), may be arranged between the carrier 22 and the heat spreader 38. The interface material 36 may contribute to a very good heat dissipation away from the carrier 22 towards the heat spreader 38.

At least one of the semiconductor chips 24 may be electrically coupled to the carrier

22, e.g. to the first contact area 40, by one or more electrically conductive conductors 44. The conductors ) 44 may extend from the carrier 22 to the corresponding semi- conductor chip 44 in a longitudinal direction of the conductor 44. In addition, the sem- iconductor chips 24 may be electrically coupled to each other by one or more further conductors 44. Further, a first terminal 46 of the power-module 20 may be electrically coupled to the first layer 30, in particular to the first contact area 40, by one or more further conductors 44. Alternatively or additionally, a signal pin 48 of the power-mod- ule 20 may be electrically coupled to one or more of the semiconductor chips 24 by one or more further conductors 44. One or more of these conductors 44 comprise or are made of aluminum and copper.

Optionally, the power-module 20 may comprise a driver board (not shown) which is electrically and mechanically coupled to the carrier 22 and/or the semiconductor chips 24, e.g. via the signal pin 48. The driver board may comprise a Printed Circuit Board (PCB). The driver board may comprise one or more electric lines, e.g. vias, embedded within or printed on the PCB. In addition, the driver board may comprise one or more further terminals, e.g. for coupling the power-module 20 to a controller for controlling the power-module 20. Further, the power-module 20, in particular the terminal 46 may be configured for being electrically coupled to an external device, e.g. a load supplied with energy by the power-module 20, e.g. an electric motor or ac- tor, and/or to an energy source, e.g. the grid or a generator.

The power-module 20 may comprise a mold body 50. The mold body 50 may have the function of a housing of the power-module 20. The mold body 50 may be made from a mold material. In particular, the carrier 22, the semiconductor chips 24, the conductors 44, the heat spreader 38, the terminal 46, the signal pin 48, and/or in case the driver board 40 may be partly or completely embedded within the mold body 50. For example, all components of the power-module 20 mentioned above may be completely embedded within the mold body 50. Alternatively, the components may be partly embedded within the mold body 50, e.g. such that in figure 1 an upper surface of the terminal 46 and/or a bottom surface of the heat spreader 38 may be free from the mold material of the mold body 50. In the following, several embodiments of the conductor(s) 44 are described. For the ease of explanation, only one conductor 44 is described in the following. However, two or more of the above conductors 44 may be configured correspondingly.

Fig. 2 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 , e.g. of one of the above conductors 44. The conductor 44 may comprise a first strand 52 comprising or being made of the aluminum and a sec- ond strand 54 comprising or being made of the copper. For example, the conductor 44 is made of the first and second strand 52, 54. The first strand 52 and the second strand 54 may be fixedly atached to each other.

The conductor 44 may be a wire having a circular cross-section. For example, the first strand 52 may be a wire having a circular cross-section and may be surrounded by the second strand 54 in a radial direction, which is perpendicular to the longitudi- nal extension of the conductor 44.

The conductor 44 may extend from the corresponding semiconductor chip 24 to the first contact area 40 and the first strand 52 and the second strand 54 each may ex- tend over the whole extension of the conductor 44. So, the first strand 52 may extend from the corresponding semiconductor chip 24 to the first contact area 40 and/or the second strand 54 may extend from the corresponding semiconductor chip 24 to the first contact area 40. In other words, a length of the conductor 44 may correspond to a length of the first strand 52 and/or to a length of the second strand 54.

The first strand 52 and the second strand 54 may physically touch each other. In other words, the first strand 52 and the second strand 54 may be in direct physical contact to each other. This may mean in this context, that no other material may be arranged between the first strand 52 and the second strand 54. The first strand 52 and the second strand 54 may physically touch each other over their whole exten- sion, i.e. over their whole length. The first strand 52 may be embedded in the second strand 52. So, the second strand 54 may surround the first strand 52 at least partly, e.g. completely, in the radial direc- tion, i.e. the direction perpendicular to the longitudinal extension of the corresponding conductor 44. In this embodiment, an outer surface of the conductor 44 may be formed by the second strand 54,

The conductor 44 may be coupled to the corresponding semiconductor chip 24 such that the copper of the conductor 44 physically touches the semiconductor chip 24. For example, the second strand 54 may be directly coupled to the corresponding semiconductor chip 24. So, no other material may be arranged between the second strand 54 and the corresponding semiconductor chip 24.

Fig. 3 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 , e.g. of one of the above conductors 44. The conductor 44 of figure 3 may partly correspond to the conductor 44 explained with respect to figure 2. Therefore, only those parts and/or features of the conductor 44 are explained in the following, in which the conductor 44 of figure 3 differs from the conductor 44 ex- plained with respect to figure 2.

The second strand 54 may be embedded in the first strand 52. So, the first strand 52 may surround the second strand 54 at least partly, e.g. completely, in the radial direc- tion, i.e. the direction perpendicular to the longitudinal extension of the conductor 44. In this embodiment, an outer surface of the conductor 44 may be formed by the first strand 52. The conductor 44 may be coupled to the corresponding semiconductor chip 24 such that the aluminum of the conductor 44 physically touches the corre- sponding semiconductor chip 24. For example, the first strand 52 may be directly coupled to the corresponding semiconductor chip 24. So, no other material may be arranged between the first strand 52 and the corresponding semiconductor chip 24.

The second strand 54 may be a wire having a circular cross-section and may be sur- rounded by the first strand 52 in the radial direction. Fig. 4 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 , e.g. of one of the above conductors 44. The conductor 44 of figure 4 may partly correspond to the conductor 44 explained with respect to figure

2. Therefore, only those parts and/or features of the conductor 44 are explained in the following, in which the conductor 44 of figure 4 differs from the conductor 44 ex- plained with respect to figure 2.

The conductor 44 may be a ribbon having a rectangular cross-section. For example, the first strand 52 may be a ribbon having a rectangular cross-section and may be surrounded by the second strand 54 in the direction perpendicular to the longitudinal extension of the conductor 44.

Fig. 5 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 , e.g. of one of the above conductors 44. The conductor 44 of figure 5 may partly correspond to the conductor 44 explained with respect to figure

3. Therefore, only those parts and/or features of the conductor 44 are explained in the following, in which the conductor 44 of figure 5 differs from the conductor 44 ex- plained with respect to figure 3.

The conductor 44 may be a ribbon having a rectangular cross-section. For example, the second strand 54 may be a ribbon having a rectangular cross-section and may be surrounded by the first strand 52 in the direction perpendicular to the longitudinal ex- tension of the conductor 44.

Fig. 6 shows a cross-section of an exemplary embodiment of a conductor of the power-module of figure 1 , e.g. of one of the above conductors 44. The conductor 44 of figure 6 may partly correspond to one or more of the above conductors 44. There- fore, only those parts and/or features of the conductor 44 are explained in the follow- ing, in which the conductor 44 of figure 6 differs from the above conductors 44.

The first strand 52 and the second strand 54 each may be a ribbon, wherein these ribbons are arranged next to each other such that the whole conductor 44 also forms a ribbon. In particular, the first strand 52 and the second strand 54 each may have a rectangular cross-section such that the whole conductor 44 also has a rectangular cross-section. Depending on the surface to which the conductor 44 should be cou- pled, the conductor 44 may be coupled to the corresponding surface via the first strand 52 or via the second strand 54.

The invention is not restricted by the above embodiments. For example, there may be more or less semiconductor chips 24 and/or corresponding conductors 44, and/or one or more further terminals 46 and/or signal pins 48. While the invention has been illustrated and described in detail in the drawings and foregoing description, such il- lustration and description are to be considered illustrative or exemplary and not re- strictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plu- rality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to ad- vantage. Any reference signs in the claims should not be construed as limiting the scope.

List of reference symbols power-module carrier first semiconductor chip first layer second layer third layer interface material heat spreader first contact area second contact area conductor terminal signal pin mold body first strand second strand