Power module and method for producing a power module

Abstract

A power module (1) is provided comprising - at least one power semiconductor chip (2), and - a heat buffer (4) thermally conductively connected to the at least one power semiconductor chip (2), wherein - the heat buffer (4) comprises a container (5) of a first material with a cavity, and - the heat buffer (4) comprises a filler (6) of a second material different from the first material arranged within the cavity, and - the second material is a phase change material. Additionally, a method for producing a power module (1) is provided.

Description

[0001] P2023,0640 WO E / P220308WO01 June 30, 2023 - 1 - Description POWER MODULE AND METHOD FOR PRODUCING A POWER MODULE The present disclosure relates to a power module and a method for producing a power module. Power semiconductor modules comprising power semiconductor chips are essential integrated parts of power converters, providing basic building blocks in a diverse range of power electronic systems. Heat generated by the power semiconductor chips, e.g. during a converter operation, is typically dissipated by a heat sink. Typically, a thermal design of the power module with heat sink is according to nominal operations in a steady state, while including a small margin to accommodate for variations around a nominal operating point. However, in many applications, e.g. including high voltage direct current, HVDC, applications it is important and beneficial that power or current can be increased significantly for a certain amount of time, i.e., to be overloaded, resulting in higher losses during the overload. Depending on how demanding an overload profile is, increased heat fluxes can result in temporary high junction temperatures that can damage the semiconductor chip and compromise the operation. A transient thermal response of the power module to heat, i.e., a thermal impedance, Zth,, mainly depends on a thermal conductivity and a heat capacity and a density or specific gravity of the materials surrounding the power semiconductor device, while a steady state thermal resistance, Rth, mainly depends on a thermal conductivity of the materials P2023,0640 WO E / P220308WO01 June 30, 2023 - 2 - surrounding the power semiconductor device and a heat extraction coefficient of a cooler connected to the heat sink. While better cooling or materials with a higher thermal conductivity can lead to reduced Rth and junction temperatures in steady state, it is important to reduce Zthduring the overload and hence to lower the transient junction temperatures for stable converter operation. Embodiments of the disclosure relate to a power module, with an improved thermal performance, especially an improved transient thermal behaviour. A further embodiment relates to a method for producing such a power module. This is achieved by the subject-matter of the independent claims. Further embodiments are evident from the dependent claims and the following description. A power module is described. The term “power” here and in the following, for example, refers to power modules, power semiconductor devices and / or power semiconductor chips adapted for processing voltages and currents of more than 100 V and / or more than 10 A, exemplary voltages up to 10 kV and electrical currents up to 10 kA. According to an embodiment, the power module comprises at least one power semiconductor chip. The power semiconductor chip comprises, for example, a semiconductor material such as at least one of silicon (Si), silicon carbide (SiC), and gallium nitride (GaN). The power semiconductor chip is, for example, a power diode and / or a power metal insulating semiconductor field-effect transistor, power MISFET for short. The term MISFET shall P2023,0640 WO E / P220308WO01 June 30, 2023 - 3 - also comprise MOSFETs, which have an oxide as insulating material at a gate. The power semiconductor chip may also be an insulated-gate bipolar transistor, IGBT. According to the embodiment, the power module comprises a heat buffer thermally conductively connected to the at least one power semiconductor chip. The heat buffer is, for example, directly arranged on the power semiconductor chip or at least one element is arranged between the heat buffer and the power semiconductor chip. According to the embodiment of the power module, the heat buffer comprises a container of a first material with a cavity. Exemplarily, the container has a top wall opposite a bottom wall, wherein the top wall and the bottom wall are connected by at least one side wall. The top wall, the bottom wall and the side wall are in particular formed of the first material forming, e.g. an integral structure. Inner surfaces of the top wall, the bottom wall and the side wall facing one another delimit and / or define the cavity. In particular, the cavity is completely enclosed three dimensionally from the container, i.e. the top wall, the bottom wall and the side wall. According to the embodiment of the power module, the heat buffer comprises a filler of a second material different from the first material arranged within the cavity. Exemplarily, the cavity is partially filled with the filler. This is that the cavity is filled with the filler to at most 95 %, at most 80 % or at most 50 %. A portion of the cavity being not filled with the filler comprises air, gases or vacuum. Alternatively, the filler fills the cavity completely. P2023,0640 WO E / P220308WO01 June 30, 2023 - 4 - According to the embodiment of the power module, the second material is a phase change material. A phase change material can undergo a phase transition between a solid aggregate state and a liquid aggregate state within a predetermined temperature range. During the transition, the phase change material absorbs or releases a predetermined amount of thermal energy as latent heat without a substantial change in its own temperature. In summary, such a power module having a combination of a container with a phase change material as a heat buffer, can provide, inter alia, the following advantages. Advantageously, integrating the phase change material in the power module as a heat buffer is an effective way to reduce the Zth and enables or increases overloadability for the power module. In particular, such a power module can enable an overloadability potential on a system level by providing at least temporary overload capability in the power module, which are the main heat dissipating units in many systems such as HVDC converters, e-mobility, and traction systems. The increased effective heat capacity allows a high amount of heat to be temporarily absorbed by the second material during the overload condition, and then slowly extracted by a cooling system of the power module. The use of phase change materials results in suppressed peak temperature rises which enhances the reliability of the power modules. P2023,0640 WO E / P220308WO01 June 30, 2023 - 5 - In addition, such a power module advantageously reduces extra semiconductor area required to accommodate for the overloadability leading to cost reduction. This invention allows to broaden a safe operating area, SOA, margin of the power semiconductor chip by relaxing the thermal limits. According to a further embodiment of the power module, the container completely encapsulates the filler three dimensionally. Exemplarily, the inner surfaces of the top wall, the bottom wall and the side wall are covered with a coating. The coating comprises, in particular, a different material than the first material and the second material. For example, a thickness of the coating is at most 50 % or at least most 10 %, or at least 1 % of a thickness of top wall, the bottom wall and / or the side wall. The thickness of the coating is, for example, at most 500 µm, at most 100 µm, at most 50 µm or at most 10 µm. The coating can be formed of a high thermal conductivity material, e.g., diamond like carbon, polycrystalline diamond, hexagonal boron nitride and / or has a surface geometry that facilitates a heat transfer to the phase change material. Advantageously, the coating protects the container against the phase change material, e.g. with respect to corrosion. In particular, diffusion of atoms of the phase change material into the first material, or vice versa, is effectively reduced. Additionally, a chemical reaction or a catalytic reaction or degradation is avoided. According to a further embodiment of the power module, the heat buffer further comprises a heat spreading structure of a third material. The third material is, for example, different P2023,0640 WO E / P220308WO01 June 30, 2023 - 6 - from the second material. Exemplarily, the third material is different from the first material or is the same than the first material. For example, the third material is formed as an integral part of the container. Alternatively, the third material is not formed as an integral part of the container. According to a further embodiment of the power module, the heat spreading structure is arranged within the cavity. In particular, the container completely encapsulates the heat spreading structure three dimensionally. Exemplarily, an outer surface of the heat spreading structure is covered with a further coating. The further coating comprises, in particular, a different material than the third material and the second material. For example, a thickness of the further coating is at most 50 % or at most 10 %, or at least 1 % of a thickness, e.g. a diameter, of the heat spreading structure. For example, the coating and the further coating comprise or consist of the same materials. Advantageously, the further coating protects the heat spreading structure against the phase change material. Additionally, the further coating can be used for improved heat conduction. According to a further embodiment of the power module, the heat spreading structure connects a bottom surface of the container and a top surface of the container. The top surface and the bottom surface are formed of the inner surfaces of the top wall and the bottom wall, respectively, facing one another. The heat spreading structure is, for example, in direct contact with the top surface and the bottom surface, respectively. P2023,0640 WO E / P220308WO01 June 30, 2023 - 7 - Advantageously, heat can be dissipated away from the power semiconductor device through the container and the heat buffer with the additional heat spreading structure more effective. According to a further embodiment of the power module, the heat spreading structure is formed of at least one of a pillar, a rib, a porous structure. In particular, the heat spreading structure comprises a plurality of pillars such as pin fins. Exemplarily, the pillars are spaced apart from one another. In cross sectional view parallel to the top surface and the bottom surface, the pillar has a round, elliptical or polygonal shape. In particular, the heat spreading structure comprises a plurality of ribs. Exemplarily, the ribs extend along a main extension direction in lateral directions. For example, the ribs are spaced apart from one another and / or extend parallel to one another. The porous structures comprises, for example, at least one of a foam, a mesh, a fabric. The second material is, in particular arranged in the pores of the porous structures. According to a further embodiment of the power module, the first material is formed electrically conductive. Exemplarily, the first material has an electrical conductivity of at least 5 x 106Siemens / m or at least 30 Siemens / m. P2023,0640 WO E / P220308WO01 June 30, 2023 - 8 - Advantageously, the container is configured to be electrically conductively connected to the power semiconductor chip and thus configured to provide an electrical current to the power semiconductor chip. For example, the first material is formed thermally conductive. Exemplarily, the first material has a thermal conductivity of at least 80 W / (m * K) or at least 200 W / (m * K). Thus, the container and the optionally additional heat dissipating structure is additionally advantageously configured to dissipate heat away from the power semiconductor chip. The first material is, for example, formed electrically conductive and thermally conductive or either electrically conductive or thermally conductive. It is conceivable that that only a part of the container is formed electrically conductive. In particular, the container comprises a first region being formed electrically conductive and a second region formed electrically insulating. According to a further embodiment of the power module, the first material comprises at least one of copper, aluminum or a corresponding alloy, boron doped diamond, copper diamond composites, graphene, carbon nano tubes, graphite, hexagonal boron nitride, silicon carbide, ceramics, composite or a combination thereof. This is that the first material can be formed of an alloy. P2023,0640 WO E / P220308WO01 June 30, 2023 - 9 - The first material can further comprise at least one of graphene, carbon nano tubes, graphite, hexagonal boron nitride, silicon carbide, and ceramics. According to a further embodiment of the power module, the second material has a thermal conductivity of at least 0.1 W / (m*K), a phase change enthalpy of at least 20 J / g, and / or a temperature of phase change of at least 80°C. In particular, the second material has a thermal conductivity of at least at least 0.2 (m*K) or at least 0.5 W / (m*K), a phase change enthalpy of at least 40 J / g or at least 100 J / g, and / or a temperature of phase change of at least 100°C or at least 120°C. In particular, the temperature of phase change is less than a maximum allowed temperature of the power module for example at most 250°C or at most 175°C or at most 120°C. Exemplarily, the second material has a heat conductivity of at least 0.28 W / (m*K) and at most 0.35 W / (m*K), a heat capacity of at least 0.16 J / (g*K) and at most 0.22 J / (g*K) as solid, and / or a phase change enthalpy of at least 40 J / g and at most 46 J / g. In particular, the second material has a melting point of at least 110 °C and at most 140 °C. With such a second material, the heat buffer is advantageously configured to provide an improved overloadability for the power module. According to a further embodiment of the power module, the second material comprises at least one of indium, In, bismuth, Bi, selenium, Sn or a combination thereof. In particular, the second material comprises an InSnZn alloy, a P2023,0640 WO E / P220308WO01 June 30, 2023 - 10 - BiIn alloy, an InSn alloy, a InCd alloy, a BiSn alloy, a BiSnAg alloy, a InAg alloy, a SnBi alloy, or In. According to a further embodiment of the power module, the third material is formed thermally conductive. Exemplarily, the third material has a thermal conductivity of at least 80 W / (m * K) or at least 200 W / (m * K). Thus, the container in combination with the heat spreading structure is further advantageously configured to dissipate heat away from the power semiconductor chip. Additionally, the third material is formed electrically conductive. Exemplarily, the third material has an electrical conductivity of at least 5 x 106Siemens / m or at least 30 Siemens / m. Thus, the container in combination with the heat spreading structure is further configured to improve the electrical conductive connection to the power semiconductor chip. According to a further embodiment of the power module, the third material comprises at least one of copper, aluminum, diamond, boron doped diamond, graphene, carbon nano tubes, graphite, hexagonal boron nitride, silicon carbide, ceramics or a combination thereof. This is that the third material can be formed of an alloy. According to a further embodiment of the power module, a heat spreading layer is arranged between the at least one power semiconductor chip and the heat buffer. Exemplarily, the heat spreading layer is in direct contact to the power semiconductor chip and the heat buffer. For example, the heat spreading layer is bonded, sintered, soldered and / or glued to the power semiconductor chip and / or the heat buffer P2023,0640 WO E / P220308WO01 June 30, 2023 - 11 - According to a further embodiment of the power module, the heat spreading layer is formed of a fourth material being formed thermally conductive. According to a further embodiment of the power module, an additional heat spreading layer is arranged on a main surface of the power semiconductor chip facing away from the heat buffer. For example, the heat spreading layer and / or the additional heat spreading layer can be connected to the power semiconductor chip solely in a thermal conductive manner. This is that there is no electrical conductive connection between the heat spreading layer and / or the additional heat spreading layer and the power semiconductor chip. The power module comprising the heat spreading layer and / or the additional heat spreading layer advantageously is configured to have an improved heat dissipation characteristic. According to a further embodiment of the power module, the additional heat spreading layer is formed of a fifth material being formed thermally conductive. Exemplarily, the fourth material and / or the fifth material has a thermal conductivity of at least 250 W / (m * K) or at least 1000 W / (m * K). Additionally, the fourth material and / or the fifth material is formed electrically conductive. In particular, the fourth material and / or the fifth material has an electrical P2023,0640 WO E / P220308WO01 June 30, 2023 - 12 - conductivity of at least 5 x 106Siemens / m or at least 30 Siemens / m. According to a further embodiment of the power module, the fourth material and / or the fifth material is comprises at least one of boron-doped diamond, hexagonal boron nitride, Cu-diamond, Ag-diamond, chemical vapor deposition grown diamond, single-crystal diamond, and graphene. According to a further embodiment of the power module, the at least one power semiconductor chip comprises at least two power contacts. Exemplarily, the power contacts are configured to provide an electrical current to functional layers or structures of the power semiconductor chip and to receive an electrical current of the functional layers or structures of the power semiconductor chip. Further, the at least one power semiconductor chip comprises, for example, at least one control contact. For example, the control contact is characteristic for a gate contact of the power semiconductor chip. The control contact is, for example, configured for controlling a switching behavior of the power semiconductor chip or for sensing purposes. According to a further embodiment of the power module, the heat buffer is electrically conductively connected to one of the at least two power contacts. According to a further embodiment of the power module, the power module further comprises a substrate on which the power semiconductor chip is arranged. For example, the power semiconductor chip is directly connected and / or directly arranged on the substrate. P2023,0640 WO E / P220308WO01 June 30, 2023 - 13 - According to a further embodiment of the power module, the substrate comprises an electrically insulating layer. According to a further embodiment of the power module, the substrate comprises a first metallization and a second metallization between which the electrically insulating layer is arranged. According to the embodiment, the power module comprises a baseplate on which the at least one power semiconductor chip is arranged. The power semiconductor chip is, for example, directly arranged on the baseplate or at least one element like an insulating substrate is arranged between the power semiconductor chip and the baseplate. Exemplarily, one power semiconductor chip or at least two power semiconductor chips are arranged on the baseplate. If at least two power semiconductor chips are arranged on the baseplate, the power semiconductor chips are in particular connected in parallel or in series with one another. The baseplate comprises, for example, a metal comprising e.g. copper and / or aluminum. Alternatively or additionally, the baseplate comprises, for example, a ceramic comprising e.g. aluminum oxide, aluminum nitride, silicon nitride. Additionally or alternatively the baseplate comprises molybdenum copper alloy, aluminum magnesium carbide, aluminum silicon carbide, a metal mesh composite as aluminum graphite. Exemplarily, the baseplate comprises cooling structures on a main surface facing away from the power semiconductor chip. P2023,0640 WO E / P220308WO01 June 30, 2023 - 14 - The cooling structures can include at least one of pin fins or ribs and cooling pipes. For example, the baseplate, the power semiconductor chip, the heat spreading layer and the heat buffer are stacked above one another in vertical direction, in particular in the order indicated. The baseplate has a main extension plane in lateral directions being perpendicular to the vertical direction. Exemplarily, the baseplate, the additional heat spreading layer, the power semiconductor chip, the heat spreading layer and the heat buffer are stacked above one another in vertical direction, in particular in the order indicated. For example, the heat spreading layer and / or the additional heat spreading layer are arranged on the baseplate. According to a further embodiment of the power module, the substrate is arranged between the baseplate and the at least one power semiconductor chip. According to a further embodiment of the power module, the heat buffer is arranged on a main surface of the power semiconductor chip facing away from the substrate. According to a further embodiment of the power module, the heat buffer is arranged between the power semiconductor chip and the substrate. According to a further embodiment of the power module, the heat buffer is arranged between the substrate and the baseplate. P2023,0640 WO E / P220308WO01 June 30, 2023 - 15 - This is that the heat buffer is advantageously arranged comparatively close to the power semiconductor chip. Thus, the heat buffer is advantageously configured to provide an effective protection for the power module due to any overload events. In particular, the power module comprise at least two heat buffers, being embodied as described herein before. The at least two heat buffers are arranged in different locations in the power module. According to a further embodiment of the power module, the power module further comprises a cooler on which the baseplate is arranged. In particular, the cooler is arranged on a side of the baseplate facing away from the power semiconductor chip. Furthermore, a method for producing a power module is described here, with which a power module as described herein above can be produced or is produced. Therefore, the features in connection with the power module are disclosed also in connection with the method and vice versa. According to an embodiment of the method, at least one power semiconductor chip is provided. In particular, the power semiconductor chip can be prefabricated. According to the embodiment of the method, a heat buffer is provided. In particular, the heat buffer can be prefabricated. P2023,0640 WO E / P220308WO01 June 30, 2023 - 16 - According to the embodiment of the method, the heat buffer is arranged on the at least one power semiconductor chip such that the heat buffer is thermally conductively connected to the at least one power semiconductor chip. According to the embodiment of the method, the heat buffer comprises a container of a first material with a cavity, the heat buffer comprises a filler of a second material different from the first material arranged within the cavity. The accompanying Figures are included to provide a further understanding. In the Figures, elements of the same structure and / or functionality may be referenced by the same reference signs. It is to be understood that the embodiments shown in the Figures are illustrative representations and are not necessarily drawn to scale. Figures 1, 2 and 3 are each a cross sectional view of a power module according to an exemplary embodiment. Figures 4 and 5 are each a schematic three dimensional view of a typical power module of the prior art. Figure 6 is a schematic three dimensional view of a power module with a heat buffer without a filler. Figures 7 and 8 are each a schematic three dimensional view of power module according to an exemplary embodiment. Figure 9 is a thermal simulation of the structures of Figures 4 to 8. P2023,0640 WO E / P220308WO01 June 30, 2023 - 17 - Figure 10 is a thermal simulation of the structures of Figures 4 and 6 to 8. The power module 1 according to the exemplary embodiment of Figure 1 comprises a power semiconductor chip 2, which is arranged on a substrate 9. The substrate 9 comprises a first metallization 11 and a second metallization 12 between which an electrically insulating layer 10 is arranged. The power semiconductor chip 2 faces the first metallization 11. In particular, the power semiconductor chip 2 is bonded, soldered and / or glued on the first metallization 11 e.g. by by soldering, diffusion soldering, gluing, sintering or other applicable method. The power module 1 further comprises a baseplate 3 on which the substrate 9 is arranged. The baseplate 3 faces the second metallization 12. In particular, the second metallization 12 is bonded, soldered, glued and / or screwed on the baseplate 3. The power module 1 further comprises heat buffer 4 thermally conductively connected to the power semiconductor chip 2. The heat buffer 4 is arranged on the power semiconductor chip 2 facing away from the substrate 9. In particular, the heat buffer 4 is bonded, soldered and / or glued on the power semiconductor chip 2. This is that the baseplate 3, the substrate 9, the power semiconductor chip 2 and the heat buffer 4 are stacked on top of one another in the order indicated. A stacking direction is a vertical direction of the power module 1. The power semiconductor chip 2, substrate 9 and the baseplate 3 and / or the heat buffer 4 each have a main extension direction perpendicular to the vertical direction. P2023,0640 WO E / P220308WO01 June 30, 2023 - 18 - The heat buffer 4 comprises a container 5 of a first material with a cavity, and a filler 6 of a second material different from the first material arranged within the cavity. The cavity is delimited by a top wall opposite a bottom wall, wherein the top wall and the bottom wall are connected by at least one side wall. The walls are part of the container 5 and are formed of the first material. The walls e.g. form an integral structure. Outer surfaces of the walls faces away from the cavity. An outer surface of the bottom wall faces the power semiconductor chip 2. In particular, the outer surface of the bottom wall is connected to the power semiconductor chip 2, exemplarily with a bond connection, a solder connection and / or a glue connection. The cavity is filled with the second material being a phase change material. In particular, the phase change material is configured to absorb heat from the power semiconductor chip 2 which is generated during operation of the power semiconductor chip 2. In particular, the heat absorption of the phase change material is achieved by a phase change from solid to liquid or from liquid to gas. The heat buffer 4 of the power module 1 according to the exemplary embodiment of Figure 2 is arranged between the power semiconductor chip 2 and the substrate 9 in vertical direction, in contrast to Figure 1. This is that the baseplate 3, the substrate 9, the heat buffer 4 and the power semiconductor chip 2 and are stacked on top of one another in the order indicated. An outer P2023,0640 WO E / P220308WO01 June 30, 2023 - 19 - surface of the bottom wall faces the substrate 9, in particular the first metallization 11. An outer surface of the top wall faces the power semiconductor chip 2. In particular, the outer surface of the bottom wall is connected to the substrate 9 and the outer surface of the top wall is connected to the power semiconductor chip 2, exemplarily each with a bond connection, a solder connection and / or a glue connection. The heat buffer 4 in Figures 1 and 2 has an extent in lateral directions being in a range of an extent in lateral directions of the power semiconductor chip 2. Here, “a range” means that the extent in lateral directions of the heat buffer 4 is at most 25 % bigger than the extent in lateral directions of the power semiconductor chip 2. The heat buffer 4 of the power module 1 according to the exemplary embodiment of Figure 3 is arranged between the power semiconductor chip 2, in particular the substrate 9 and the baseplate 3 in vertical direction, in contrast to Figures 1 and 2. This is that the baseplate 3, the heat buffer 4, the substrate 9 and the power semiconductor chip 2 and are stacked on top of one another in the order indicated. An outer surface of the bottom wall faces the baseplate 3. An outer surface of the top wall faces the substrate 9, in particular the second metallization 12. In particular, the outer surface of the bottom wall is connected to the baseplate 3 and the outer surface of the top wall is connected to the substrate 9, exemplarily each with a P2023,0640 WO E / P220308WO01 June 30, 2023 - 20 - bond connection, a solder connection and / or a glue connection. The heat buffer 4 in Figure 3 has an extent in lateral directions being bigger than a range of an extent in lateral directions of the power semiconductor chip 2. Here, “larger than a range” means that the extent in lateral directions of the heat buffer 4 is at least 25 % or at least 50 % bigger than the extent in lateral directions of the power semiconductor chip 2. Exemplarily, the heat buffer 4 in Figure 3 has an extent in lateral directions being in a range of an extent in lateral directions of the substrate 9. Here, “a range” means that the extent in lateral directions of the heat buffer 4 is at most 25 % bigger and / or at least 25 % smaller than the extent in lateral directions of the substrate 9. The typical power module according to the example of Figure 4 has a cooler 13, a baseplate 3, two heat spreading layers 7, 8, wherein only one heat spreading layer is shown in Figures 4 to 8, and two power semiconductor chips 2. Each power semiconductor chip is provided with a heat spreading layer 7, 8. Further, on each of the power semiconductor chips 2 a typical bulk aluminum block is arranged. Each typical bulk aluminum block terminates flush with the corresponding power semiconductor chip 2 in lateral directions. In contrast to the typical power module according to Figure 4, to the typical power module of figure 5 has bulk copper blocks. On each of the power semiconductor chips 2 a typical bulk copper block is arranged. Each typical bulk copper block P2023,0640 WO E / P220308WO01 June 30, 2023 - 21 - protrudes beyond the corresponding power semiconductor chip 2 in lateral directions. On each of the power semiconductor chips 2 in Figure 6 a container 5 to be used as heat buffer according to Figure 1 is arranged. On each of the power semiconductor chips 2 in Figure 7 a single heat buffer 4 according to Figure 1 is arranged. Exemplarily, it is conceivable that a single heat buffer 4 is arranged on all power semiconductor chips 2. The power module 1 according to the exemplary embodiment of Figure 8 has in contrast to the exemplary embodiment of Figure 7 additional a heat spreading structure 14 within the cavity, consisting e.g. of pillars in particular connecting the bottom wall and the top wall of the container 5. The diagram of Figure 9 shows on the y axis a junction temperature T in °C and on the x axis the time t in seconds as a response of a heat pulse shown in the inset. The inset shows on the y axis a relative power P of the heat pulse and on the x axis the time t in seconds, wherein the pulse lasts for approximately 4 seconds. The simulation results shown in the diagram of Figure 9 corresponds to the structure shown in Figure 4 for curve K1, Figure 5 for curve K2, Figure 6 for curve K3, Figure 7 for curve K4 and Figure 8 for curve K5 The diagram of Figure 10 shows on the y axis the thermal impedance Zth in K / kW and on the x axis the time t in seconds. The inset shows a zoom showing a dent in the Zth P2023,0640 WO E / P220308WO01 June 30, 2023 - 22 - curve corresponding to when the majority of the phase change materials melts. In this particular case the phase change material is designed for an overload profile case of 4 seconds, which the phase change material melts before the 4 seconds to suppress the peak temperature rise. Generally, depending on overload profile requirement the Zthcurve can be engineered by the design of the heat buffer to enable overloadability from a fraction of second up to few minutes. The simulation results shown in the diagram of Figure 10 corresponds to the structure shown in Figure 4 for curve K1, Figure 5 for curve K2, Figure 6 for curve K3, Figure 7 for curve K4 and Figure 8 for curve K5.

[0002] P2023,0640 WO E / P220308WO01 June 30, 2023 - 23 - Reference Signs 1 power module 2 power semiconductor chip 3 baseplate 4 heat buffer 5 container 6 filler 7 heat spreading layer 8 additional heat spreading layer 9 substrate 10 electrically insulating layer 11 first metallization 12 second metallization 13 cooler 14 heat spreading structure

Claims

P2023,0640 WO E / P220308WO01 June 30, 2023 - 24 - Claims 1. Power module (1) comprising - at least one power semiconductor chip (2), and - a heat buffer (4) thermally conductively connected to the at least one power semiconductor chip (2), wherein - the heat buffer (4) comprises a container (5) of a first material with a cavity, and - the heat buffer (4) comprises a filler (6) of a second material different from the first material arranged within the cavity, and - the second material is a phase change material.

2. Power module (1) according to claim 1, wherein - the container (5) completely encapsulates the filler (6) three dimensionally.

3. Power module (1) according to one of the claims 1 or 2, wherein - the heat buffer (4) further comprises a heat spreading structure (14) of a third material, and - the heat spreading structure (14) is arranged within the cavity.

4. Power module (1) according to claim 3, wherein - the heat spreading structure (14) connects a bottom surface of the container (5) and a top surface of the container (5).

5. Power module (1) according to one of the claims 3 or 4, wherein - the heat spreading structure (14) is formed of at least one of a pillar, a rib, a porous structure.P2023,0640 WO E / P220308WO01 June 30, 2023 - 25 - 6. Power module (1) according to one of the claims 1 to 5, wherein - the first material is formed electrically conductive, and - the first material comprises at least one of copper, aluminum or a corresponding alloy, boron doped diamond, copper diamond composites, graphene, carbon nano tubes, graphite, hexagonal boron nitride, silicon carbide, ceramics, composite or a combination thereof.

7. Power module (1) according to one of the claims 1 to 6, wherein - the second material has a thermal conductivity of at least 0.1 W / (m*K), a phase change enthalpy of at least 20 J / g, and / or a temperature of phase change of at least 80°C.

8. Power module (1) according to one of the claims 1 to 7, wherein - the second material comprises of at least one of indium, In, bismuth, Bi, selenium, Sn or a combination thereof.

9. Power module (1) according to one of the claims 3 to 8, wherein - the third material is formed thermally conductive, and - the third material comprises at least one of copper, aluminum or corresponding alloy, diamond, boron doped or undoped diamond, graphene, carbon nano tubes, graphite, hexagonal boron nitride, silicon carbide, ceramics or a combination thereof.

10. Power module (1) according to one of the claims 1 to 9, whereinP2023,0640 WO E / P220308WO01 June 30, 2023 - 26 - - a heat spreading layer (7) is arranged between the at least one power semiconductor chip (2) and the heat buffer (4), and - the heat spreading layer (7) is formed of a fourth material being formed thermally conductive.

11. Power module (1) according to one of the claims 1 to 10, wherein - an additional heat spreading layer (8) is arranged on a main surface of the power semiconductor chip (2) facing away from the heat buffer (4), and - the additional heat spreading layer (8) is formed of a fifth material being formed thermally conductive.

12. Power module (1) according to one of the claims 10 or 11, wherein - the fourth material and / or the fifth material is comprises at least one of boron-doped or undoped diamond, hexagonal boron nitride, Cu-diamond, Ag-diamond, chemical vapor deposition grown diamond, single-crystal diamond, and graphene.

13. Power module (1) according to one of the claims 1 to 12, wherein - the at least one power semiconductor chip (2) comprises at least two power contacts, and - the heat buffer (4) is electrically conductively connected to one of the at least two power contacts.

14. Power module (1) according to one of the claims 1 to 13, wherein - the power module (1) further comprises a baseplate (3) on which the at least one power semiconductor chip (2) is arranged.P2023,0640 WO E / P220308WO01 June 30, 2023 - 27 - 15. Power module (1) according to one of the claims 1 to 14, wherein - the power module (1) further comprises a substrate (9) on which the power semiconductor chip (2) is arranged, - the substrate (9) comprises an electrically insulating layer (10), and - the substrate (9) comprises a first metallization (11) and a second metallization (12) between which the electrically insulating layer (10) is arranged.

16. Power module (1) according to claim 15, wherein - the substrate (9) is arranged between the baseplate (3) and the at least one power semiconductor chip (2).

17. Power module (1) according to one of the claims 15 or 16, wherein at least one of - the heat buffer (4) is arranged on a main surface of the power semiconductor chip (2) facing away from the substrate (9), - the heat buffer (4) is arranged between the power semiconductor chip (2) and the substrate (9), and - the heat buffer (4) is arranged between the substrate (9) and the baseplate (3).

18. Power module (1) according to one of the claims 1 to 17, wherein - the power module (1) further comprises a cooler (13) on which the baseplate (3) is arranged.

19. Method for producing a power module (1), with - providing at least one power semiconductor chip (2), - providing a heat buffer (4),P2023,0640 WO E / P220308WO01 June 30, 2023 - 28 - - arranging the heat buffer (4) on the at least one power semiconductor chip (2) such that the heat buffer (4) is thermally conductively connected to the at least one power semiconductor chip (2), wherein - the heat buffer (4) comprises a container (5) of a first material with a cavity, - the heat buffer (4) comprises a filler (6) of a second material different from the first material arranged within the cavity, and - the second material is a phase change material.

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