Semiconductor power module and method for manufacturing a semiconductor power module

Abstract

A semiconductor power module (1) comprises a metal base structure (10) having a metal top layer (11), a metal bottom layer (13) and a dielectric layer (12) in between. The semiconductor power module (1) further comprises a housing (2) having a top wall (21) and side walls (22) and coupled to the metal base structure (10) such that, with respect to a stacking direction (A), a predetermined distance (D) exists between a lower surface (24) of the top wall (21) and an upper surface (14) of the metal top layer (11) adjacent the side walls (22), respectively. The semiconductor power module (1) further comprises at least one terminal (16) arranged inside the housing (2), the at least one terminal (16) being coupled to the lower surface (24) of the top wall (21) on the one hand and to the upper surface (14) of the metal top layer (11) on the other hand. With respect to the stacking direction (A), a length of the at least one terminal (16) is configured in coordination with the distance (D) such that, due to the at least one terminal (16), the metal base structure (10) is bent in a predetermined manner and comprises a convex shape interacting with the housing (2) and the at least one terminal (16).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a semiconductor power module and a corresponding manufacturing method for a semiconductor power module. BACKGROUND

[0002] Conventional insulated metal substrates form a technology for low and medium power semiconductor packages, while having low insulation requirements and low thermal resistance requirements. Coolers are used for heat dissipation, and it is a challenge to facilitate efficient heat dissipation. SUMMARY

[0003] Embodiments of the present disclosure can provide a semiconductor power module having an insulated metal substrate structure that enables efficient heat dissipation and reliable operation even for high voltage power module applications. Further embodiments of the present disclosure can provide a manufacturing method for such a semiconductor power module.

[0004] According to embodiments, a semiconductor power module comprises an insulated metal substrate structure having a metal top layer, a metal bottom layer and a dielectric layer. The dielectric layer is coupled to both the metal top layer and the metal bottom layer and arranged between both the metal top layer and the metal bottom layer with respect to a stacking direction of the metal substrate structure. The semiconductor power module further comprises a housing configured to enclose electronic devices of the semiconductor power module. The electronic devices can comprise chips, in particular power semiconductor devices, integrated circuits and / or discrete devices of other devices or sensors. The housing comprises a top wall and side walls and can comprise a U-shape or a pot shape. The housing is coupled to the metal substrate structure, for example by means of the side walls of the housing. The housing and the metal substrate structure are coupled to each other directly or indirectly, such that with respect to the stacking direction a predetermined distance exists between a lower surface of the top wall and an upper surface of the metal top layer adjacent to the side walls, respectively. The semiconductor power module further comprises at least one terminal arranged inside the housing or between the housing and the metal substrate structure. The at least one terminal is coupled to the lower surface of the top wall on the one hand and to the upper surface of the metal top layer on the other hand. The at least one terminal has a length with respect to the stacking direction that is configured in coordination with the distance between the lower surface of the top wall and the upper surface of the metal top layer adjacent to the side walls. The length of the at least one terminal is configured such that due to the at least one terminal the metal substrate structure is curved in a predetermined manner and comprises a convex shape of its back side interacting with the housing.

[0005] Due to the described configuration of the housing, the metal base structure and the one or more terminals in between, a semiconductor power module is feasible which provides a proper thermal interface and enables a high efficient heat dissipation and reliable operation even for high voltage power module applications and even for large size modules. The housing and the at least one terminal expose a compression load on the top side or upper surface of the metal base structure. Thus, due to the specific length of the side walls and the one or more terminals which are constructed in coordination with each other, a pre-bowed insulation metal base plate is feasible and the resulting convex bow of the back side facilitates a proper thermal contact between the metal base structure and the cooler.

[0006] According to embodiments, the total length including the length of the at least one terminal is given such that in a direction towards the metal top layer, the at least one terminal protrudes by at least 0.5 mm over this distance or over the length of the side wall or the respective side wall portion. Alternatively expressed, the total length is larger than the distance between the lower surface of the top wall and the upper surface of the metal top layer by 0.5 mm or more. Thus, the one or more terminals can have a specific length which is longer than the multiple parts of the housing compared to the distance between the module cover and the upper surface of the insulation metal base plate in a relaxed state before the housing block is mounted.

[0007] The respective length of the at least one terminal and the side wall can refer to a respective section of the terminal or the side wall or to the complete length of the associated element in the stacking direction. Due to the fact that the at least one terminal is intentionally formed longer than the corresponding length of the side wall, the metal base structure is bent outwards away from the housing, resulting in a convex shape of the back side of the metal base structure. For example, the edges or lateral areas of the metal base structure which are connected to the side walls of the housing are pulled or pressed towards the housing due to the coupling and / or are fixedly connected (e.g. by gluing or screwing) with the side walls of the housing, while the one or more terminals expose a compression load on the metal base structure which pushes the middle section of the metal base structure away from the housing.

[0008] The length of the at least one terminal can also be constructed in coordination with adjacent elements which add to the total length which is larger than the above described predetermined distance between the lower surface of the top wall and the upper surface of the metal top layer. For example, additional elements or protrusions can be present on the upper surface of the metal top layer and / or on the lower surface of the top wall. Thus, the length of the terminal itself can be longer, but does not necessarily have to be longer than the distance between the top wall and the metal top layer.

[0009] For example, if no additional elements or protrusions are present between the terminal and the top wall and / or between the terminal and the metal top layer, the length of the terminal is greater than the above-mentioned distance and longer than the length of the respective sidewall portion between the lower surface of the top wall and the upper surface of the metal top layer. In such cases, the at least one terminal protrudes beyond this distance or the length of the sidewall or sidewall portion with respect to the direction towards the metal top layer and causes a bending of the insulated metal base structure and a convex shape at its backside when joining the housing together with the terminal and the metal base structure.

[0010] According to an embodiment of the semiconductor power module, the housing and the metal base structure are coupled to each other by means of at least one of screwing, gluing, clamping, and sealing or any other applicable coupling method. For example, a seal can be arranged between the sidewall or frame portion of the housing and the metal base structure. For example, the housing and / or the metal bottom layer comprises a respective screw hole to enable a screwing connection. Thus, the housing and the metal base structure can be coupled to each other by means of screwing connections which are positioned in a respective area or part or portion of the sidewall of the housing.

[0011] According to a further embodiment of the semiconductor power module, the housing is formed by means of molding, for example by means of injection molding, transfer molding, and / or compression molding. The one or more terminals are integrally coupled to the molded housing and partially embedded in the housing. The molded housing can be made of a thermoplastic resin or a thermosetting resin. For example, the housing is made of an epoxy resin. The material of the housing can also comprise fillers, such as particles, fibers, and / or chemical additives.

[0012] According to a further embodiment of the semiconductor power module, the at least one terminal is connected to the lower surface of the top wall and / or to the upper surface of the metal top layer by means of at least one of clamping, soldering, welding, gluing, and sintering. Alternatively or additionally, other applicable joining methods are possible.

[0013] It is found in the context of the present disclosure that due to the concave bow of the backside of the metal base between the bottom plate and the cooler surface, conventional insulated metal bases can have the risk of forming a cavity which greatly reduces the thermal performance of the corresponding power module. Conventional insulated metal bases are typically flat before assembly of the power module and thus, after module assembly, there is a risk that the insulated metal base will have a strong unnecessary concave bow of the backside, making this bottom plate type unusable for power modules with a large footprint. For example, due to thermal mismatch between the silicon chips and the metal sheet and the mechanical setup of the insulated metal base, the backside of the initially flat insulated metal base can have a strong concave bow of several hundred micrometers after soldering the chips to the insulated metal base.

[0014] Due to the described pre-bent metal base plate structure, a predetermined convex shape of the backside of the base plate can be provided. In view of the preliminary stage, e.g. the chip soldering to the metal base plate structure resulting in a concave bow, the described configuration of the semiconductor power module compensates or counteracts the concave bow (over)compensates. Thus, the described semiconductor power module configuration enables to prevent the formation of a cavity between the base plate and the cooler surface when mounting the semiconductor power module to the cooler unit or heat sink. Thus, a very uniform and large surface contact between the bottom surface of the metal base plate structure and the heat sink is feasible, resulting in a proper thermal interface between the metal base plate structure and the heat sink. In particular, due to the convex bow of the backside or bottom surface of the metal base plate structure, a reliable thermal contact is formed in the center of the metal base plate structure. Due to the exposed pressure of the terminals, the base plate can become flat when mounting the semiconductor power module to the cooler, however the pressure is exposed in particular in the center, which prevents the formation of a cavity. Additionally, the convex bow and thus the proper thermal interface can still be available during operation of the module, which can contribute to an improved reliability.

[0015] According to a further embodiment, the semiconductor power module comprises two or more terminals arranged inside the housing and coupled to the lower surface of the top wall on the one hand and to the upper surface of the metal top layer on the other hand. The two or more terminals can have different lengths between the lower surface and the upper surface with respect to the stacking direction. In the following, the present disclosure is described in the context of multiple terminals. For example, the semiconductor power module comprises three or four or five terminals. However, the features and properties of the two or more terminals are disclosed also with respect to semiconductor power modules comprising only one terminal and vice versa.

[0016] According to a further embodiment of the semiconductor power module, the terminals or the respective elongated portions of the terminals are arranged inside the housing symmetrically along a transversal direction perpendicular to the stacking direction and with respect to a center axis or a plane of symmetry of the semiconductor power module.

[0017] According to a further embodiment of the semiconductor power module, the terminals can comprise a spring or stress relief structure configured to expose a pressure or to compensate for an excessive mechanical stress on the metal base plate structure or the respective terminal pin in a predetermined manner.

[0018] According to a further embodiment, the semiconductor power module comprises a buffer element coupled to the at least one terminal, the buffer element being configured to expose a pressure on the terminal and / or the metal base plate structure in a predetermined manner. The buffer element can be arranged on the top wall of the housing and can expose the pressure from the top. Possibly, the buffer element can be arranged between the top side of the housing and the respective terminal. The height of the terminal can be the sum of the height of the terminal itself and the buffer element.

[0019] According to a further embodiment of the semiconductor power module, the terminal includes a corresponding elongated terminal body and a corresponding plate-shaped terminal foot having a contact surface that contacts or faces the upper surface of a metal substrate structure. The terminal foot may directly contact a metallized pattern or a top metal layer, or the contact surface of the terminal foot may be partially or completely covered with a coating comprising one or more layers made of at least one of gold, silver, and nickel. Furthermore, the entire terminal may be coated.

[0020] According to a further embodiment, the semiconductor power module includes a heat sink coupled to the bottom surface of a metal substrate for heat dissipation during operation of the semiconductor power module. The semiconductor power module may include a separate heat sink, such as one having fins or ribs. Alternatively or additionally, the metal substrate structure may act as the heat sink itself and may be configured to include stud-like fins, ribs, or protrusions, for example, to provide beneficial heat dissipation. The metal substrate may further act as the base plate of the semiconductor power module. The semiconductor power module including the metal substrate structure may further be partially or entirely encapsulated by a resin prepared by molding or potting, or by a dielectric gel. Even with rigid filler materials, the described arrangement or configuration of the semiconductor power module can help provide and retain the desired bowing during and after the packaging process.

[0021] The described configuration of the semiconductor power module enables the mounting of a housing block (where power terminals and / or auxiliary terminals may be part of the housing block) to an insulating metal substrate, which comprises a metal base, an insulating resin sheet, and circuit metallization implemented by the metal substrate structure. The one or more terminals are specifically designed to expose compressive loads to the insulating metal substrate, resulting in an arching of at least a portion of the back side of the metal substrate structure.

[0022] According to an embodiment, a method for manufacturing a semiconductor power module includes providing a metal substrate structure, a housing, and at least one terminal as described above. Thus, the at least one terminal has a given length relative to the stacking direction, which is greater than, for example, at least 0.5 mm than the length of the sidewall of the housing. The method further includes coupling the at least one terminal, the housing, and the metal substrate structure together such that the at least one terminal is arranged inside the housing and coupled on one hand to a lower surface of a top wall and on the other hand to an upper surface of a top metal layer. Thereby, the one or more terminals provide a compressive load on the metal substrate structure, causing the metal substrate structure to bend in a predetermined manner and include a convex shape on the bottom or back side of the metal substrate structure that interacts with the housing and the at least one terminal.

[0023] The described method thus enables the manufacturing of embodiments of the above semiconductor power module, and the described features and properties of the semiconductor power module are also disclosed for the manufacturing method, and vice versa. The present disclosure thus comprises several aspects, wherein each feature described in relation to one of the aspects is also disclosed herein in relation to the other aspects, even if the respective feature is not explicitly mentioned in the context of a specific aspect.

[0024] According to embodiments of the method, the step of coupling the terminal, the housing and the metal base structure together comprises forming the housing by means of molding such that the at least one terminal is integrally coupled to the molded housing and partially embedded in the housing. The method further comprises coupling the molded housing and the embedded at least one terminal to the metal base structure by means of at least one of screwing, clamping, gluing and sealing.

[0025] According to embodiments of the method, the step of providing the metal base structure can comprise forming an insulated metal base plate by coupling a metal top layer with a dielectric layer and with a metal bottom layer. The method can thus comprise aligning the metal top layer, the dielectric layer and the metal bottom layer relative to each other and laminating the metal top layer, the dielectric layer and the metal bottom layer.

[0026] Alternatively, the step of coupling the metal top layer with the dielectric layer and with the metal bottom layer comprises providing a molding substance, aligning the metal top layer and the metal bottom layer relative to each other with a predetermined distance between the two, and then bringing the provided molding substance between the aligned metal top layer and the metal bottom layer and thereby forming the dielectric layer by means of molding. For example, the forming of the dielectric layer by means of molding can be done by injection molding, compression molding and / or transfer molding.

[0027] The dielectric layer can thus implement a prepreg sheet that is assembled between two metal plates forming the metal top layer and the metal bottom layer on top and bottom. For example, such a metallized sheet or plate is bonded to the insulating part of the dielectric layer by a lamination process. The required metallization structure of the metal top layer can then be completed by subsequent steps of masking and etching processes to locally remove the conductive metal, resulting in the final metallization structure.

[0028] With regard to the molded dielectric layer, the molding substance realizes a pumpable substance with predetermined material properties. The pumpable substance is a liquid or viscous raw material of the dielectric layer to be formed. For example, the molding substance is an epoxy resin and / or a ceramic-based liquid, which contains thermally conductive inorganic filler material including ceramic particles. Alternatively or additionally, the raw material of the dielectric layer can be a thermoset or thermoplastic resin material, such as polyamide, PBT, PET. Alternatively or additionally, the raw material of the dielectric layer can include inorganic fillers in order to improve thermal conductivity and / or CTE adjustment with respect to the metal top layer and / or the metal bottom layer. For example, the molded dielectric layer comprises a resin-based dielectric material with ceramic filler material (e.g., epoxy resin, AI2O3, AIN, BN, Si3N4, or SiO2). For example, the dielectric layer is an epoxy resin with fillers. The dielectric layer can also be based on other materials suitable for transfer molding, injection molding, or compression molding, such as bismaleimides, cyanate esters, polyimides, and / or silicones. Alternatively or additionally, the dielectric layer can include ceramic materials and / or hydroset materials or a material combination of two or more of the above-mentioned components. The thickness of the dielectric resin layer can have a value between 100 pm and 200 pm.

[0029] The alignment of the metal top layer and the metal bottom layer with respect to each other with a predetermined distance between both essentially predetermines the later thickness of the molded dielectric layer. For example, the alignment can be achieved by placing the metal top layer onto a release film or a liner or another fixture (e.g., in an encapsulation mold of a molding tool). This enables, for example, to precisely position the provided metallization structures of the metal top layer with respect to the metal bottom layer and can be useful if the metal top layer comprises separate metal pads due to different operating potentials. In case of lamination, the thickness of the resin layer is given by the thickness and behavior of the lamination layers.

[0030] According to a further embodiment of the manufacturing method, the metal top layer can be provided with a given metallization pattern by means of stamping. Alternatively or additionally, the metal top layer can be provided, for example, by means of etching and / or cutting. Alternatively or additionally, the metal top layer is formed, for example, by means of laser cutting of a metal sheet provided with a predetermined structure.

[0031] The metallization of the metal top layer can be formed by a film and / or sheet comprising copper and / or aluminum and / or a copper alloy and / or an aluminum alloy. This can also apply to the metal bottom layer, for example, the metal bottom layer can be formed as a copper and / or aluminum plate and / or a corresponding alloy. The metal top layer can comprise a coating of the circuit metallization. Such a coating can be made of or comprise one or more layers of nickel, gold, silver, and / or other metals. The thickness of the circuit metallization or the metal top layer can have a value between 150 pm and 500 pm.

[0032] The one or more terminals can act as power terminals or auxiliary terminals, e.g. for signal wiring. The one or more terminals can be made of or comprise copper or a copper alloy. The one or more terminals can comprise at the bottom surface a coating of one or more layers made of or comprising nickel, gold, silver and / or other metals. Alternatively or additionally, further portions or the complete terminal can be coated. The one or more terminals are specifically designed for the application of a compression load. The terminals have a length which is at least 0.5 mm larger than the distance between the lower surface of the housing module cover and the upper surface of the insulated metal substrate in a relaxed state before mounting of the housing block. The length of the individual terminals can be different. The housing can be formed as a molded block comprising a shape with a pre-bend or bend or protruding structure which can support the compression load exposed by the terminals to the insulated metal substrate realized by the metal substrate structure.

[0033] The proposal to use a housing block realized by a housing in which the terminals expose a pressure or compression load to an insulated metal substrate realized by a metal substrate structure makes this rather cost-effective substrate technology interesting for large power modules and higher voltage classes of power modules. This enables, for example, the manufacturing of semiconductor power modules with a lateral side length or width of 34 mm times 100 mm or even up to 140 mm times 190 mm. In this regard, the lateral side length or width extends in a lateral direction perpendicular to a stacking direction of the semiconductor power module.

[0034] Due to the exposure of the pressure, the backside of the insulated metal substrate has a correct convex bow orientation even after complete assembly of the semiconductor power module, which is beneficial for a proper thermal interface between the semiconductor power module and a cooler or heat sink. After mounting to the cooler, the substrate becomes almost flat, whereas the one or more longer terminals expose a pressure to the metal substrate structure to prevent the formation of a cavity, especially in the center region.

[0035] The described configuration of the semiconductor power module allows for a significant cost reduction when replacing the standard setup of a ceramic substrate soldered to a base plate by an insulated metal substrate realized by a metal substrate structure. On the one hand material costs can be reduced and on the other hand several process steps can be removed from the process flow, like a joining process between the substrate and the base plate in the assembly of the semiconductor power module. Additionally, the use of a screw connection between the housing and the insulated metal substrate can obviate the need for gluing the module housing to the insulated metal substrate. BRIEF DESCRIPTION OF DRAWINGS

[0036] In the following, exemplary embodiments are explained with the help of schematic drawings and reference signs. The figures show:

[0037] Figure 1 An embodiment of a semiconductor power module is shown in a schematic side view;

[0038] Figures 2 to 3 An embodiment of a semiconductor power module is shown in a schematic cross-sectional view; and

[0039] Figure 4 A flow chart of a method for manufacturing an embodiment of a semiconductor power module is shown. DETAILED DESCRIPTION

[0040] The accompanying drawings are included to provide a further understanding. It will be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale. The same reference numerals designate the same elements or components throughout the several views. Descriptions of elements or components are not repeated for each of the several views, as long as the elements or components correspond to each other in terms of their function, regardless of their appearance in different drawings. For the sake of clarity, elements can not appear in all of the drawings with corresponding reference numerals.

[0041] Figure 1 A side view of an embodiment of a semiconductor power module 1 for a semiconductor device is shown. According to further embodiments, the semiconductor power module 1 can comprise alternative forms, like the form shown in Figure 1 . The semiconductor power module 1 comprises a metal substrate structure 10 implementing an insulated metal substrate. The semiconductor power module 1 further comprises electronic devices coupled with the metal substrate structure 10, and a heat sink 3 also coupled with the metal substrate structure 10. For example, the electronic devices can comprise chips, in particular power semiconductor devices. The electronic devices are coupled with an upper surface 14 of a metal top layer 11 of the metal substrate structure 10, with respect to a stacking direction A of the illustrated embodiment (see Figure 2 and Figure 3 ). The heat sink 3 is coupled with a bottom surface 15 of a metal bottom layer 13 of the metal substrate structure 10. The metal substrate structure 10 further comprises a dielectric layer 12 formed between the metal top layer 11 and the metal bottom layer 13.

[0042] For example, both the metal top layer 11 and the metal bottom layer 13 consist of or at least comprise a metal, such as copper and / or aluminum and / or a corresponding alloy. Alternative thermally and / or electrically conductive materials or material combinations can be used instead. For example, the dielectric layer 12 is a prepreg sheet or a molded epoxy resin with fillers. The fillers can be ceramic-like or realized by other inorganic fillers, like glass fibers. Alternatively or additionally, the dielectric layer 12 can comprise a thermoplastic or thermoset resin, such as polyamide, PBT and / or PET. Alternatively or additionally, the dielectric layer 12 comprises a ceramic-based insulation layer, such as AI2O3, AIN, BN, Si3N4, SiO2. The dielectric layer 12 can also be based on other materials suitable for injection molding, transfer molding and / or compression molding, such as bismaleimides, cyanate esters, polyimides and silicones, or even possibly on ceramic materials, such as hydroset materials. Thus, the metal substrate structure 10 realizes an insulated metal substrate with a structured top-side metallization, a metal back-side plate and a dielectric insulation layer in between. For example, the pads of the metal top layer 11 are connected to components of the electronic device via the leads 4 and / or via the terminals 16, which are coupled with the metal top layer 11 by means of soldering or brazing.

[0043] The illustrated semiconductor power module 1 can realize a gel or resin filled power module, wherein the entire top side of the electronic device or even more of the metal substrate structure 10 can be embedded in or covered by an epoxy resin, a thermoplastic or other thermoset resin and / or a gel encapsulation. For example, such encapsulation can be done by means of molding after manufacturing the metal substrate structure 10. The potting or molding can be done after mounting the chips and mounting the resin housing, for example with terminals incorporated or separately mounted terminals. Preparation options of the semiconductor power module 1 can include filling with a gel, filling with an epoxy resin by means of injection molding, transfer molding and / or other molding methods, or potting.

[0044] Figures 2 to 3 Different embodiments of the semiconductor power module 1 are illustrated in schematic side views and / or cross-sectional views.

[0045] The semiconductor power module 1 comprises a metal base structure 10 and a housing 2 which is configured to enclose the electronics and the metal base structure 10 of the semiconductor power module 1. The housing 2 comprises a top wall 21 and side walls 22 and is coupled to the metal base structure 10 by means of its side walls 22 and by means of screwing, clamping and / or gluing and can comprise a seal between the side walls 22 and the metal base structure 10. If a screw connection is used, the screw connection can be positioned in a respective region adjacent to the side walls 22 of the housing 2 and spaced apart from the intermediate section 18 of the metal base structure 10. The housing 2 can be formed by molding, for example, from an epoxy resin or using any of a thermoplastic or thermosetting resin. The housing 2 can form the above-mentioned encapsulation of the semiconductor power module 1 or can form an additional cover for the metal base structure 10. The housing 2 can be formed in one piece or can be made of two or more parts, for example comprising a frame providing the side walls 22 and a cover providing the top wall 21.

[0046] The semiconductor power module 1 further comprises at least one terminal 16 arranged inside the housing 2. According to the embodiment illustrated in Figure 2 The semiconductor power module 1 comprises four terminals 16 according to the embodiment illustrated in Figure 3 The semiconductor power module 1 comprises three terminals 16 according to the embodiment illustrated in. The terminals 16 or their elongated portions are symmetrically arranged inside the housing 2 along a transverse direction B perpendicular to the stacking direction A with respect to a central axis M or a plane of symmetry located in the center. Alternatively, the terminal legs can be symmetrically arranged. However, the terminals 16 can also be arranged asymmetrically.

[0047] The terminals 16 are coupled to the lower surface 24 of the top wall 21 on the one hand and to the upper surface 14 of the metal top layer 11 on the other hand. The terminals 16 each comprise an elongated terminal body and a plate-like terminal leg having a contact surface 17 contacting the upper surface 14 of the metal base structure 10. Alternatively, there can be a bonding layer arranged between the contact surface 17 of one or more terminals 16 and the upper surface 14. For example, the bonding layer can be made of or can comprise a glue, a solder and / or a sintering material. The terminals 16 can be connected to the upper surface 14 by means of brazing, gluing, sintering, ultrasonic welding, laser welding and / or another welding and / or bonding process. An upper portion of the elongated terminal body of the terminals 16 can be integrally coupled to the top wall 21 embedded in the overmolded housing 2. A dry or pressure contact or clamping of the terminals 16 and the housing 2 is also possible. Alternatively or additionally, the elongated terminal body of the terminals 16 can be connected to the top wall 21 by another bonding method or it can be connected with a horizontal terminal portion located at the bottom side or lower surface 24 of the top wall 21.

[0048] The housing 2 and the metal base structure 10 are coupled such that, with respect to the stacking direction A, a predetermined distance D exists between the lower surface 24 of the top wall 21 and the upper surface 14 of the metal top layer 11 adjacent to the side wall 22, respectively. The terminals 16 are configured to comprise a specific length or height. For example, at least one terminal 16 comprises a length which is greater than the respective length of the corresponding side wall portion of the side wall 22 proximate to the side wall 22, respectively.

[0049] For example, the length of the one or more terminals 16 is at least 0.5 mm greater than the one or the distance D in the side wall 22. The length and the distance D refer to the direction along the stacking direction A. The length of the respective terminal 16 is essentially defined by the length of the elongated terminal body between the lower surface 24 of the top wall 21 and the upper surface 14 of the metal top layer 11. The compared side wall 22 length also relates to the section of the respective side wall 22 between the lower surface 24 of the top wall 21 and the upper surface 14 of the metal top layer 11 and / or the bottom surface of the side wall 22 at the outer edge regions where the side wall 22 and the metal base structure 10 are coupled. As Figure 2 and Figure 3 As indicated in the above, the terminals 16 closer to the edge regions can have a smaller length than the terminal(s) 16 in or closer to the middle section 18. Thus, at least one terminal 16 in or closer to the middle section 18 comprises a length which is at least 0.5 mm greater than the length of the side wall 22. At least one of the terminals 16, but not necessarily all of the terminals 16, can have a length which is at least 0.5 mm greater than the length of the side wall 22.

[0050] Thus, due to the one or more terminals 16 being longer than the side wall 22, a compressive load is exposed on the metal base structure 10 such that it is bent in a predetermined manner and comprises a convex shape of the base backside interacting with the housing 2 and the terminals 16. Thus, the middle section 18 of the metal base structure 10 is pressed outwardly and a resulting bending height H is formed between the height level of the upper surface 14 at the edge regions and the height level of the upper surface 14 in the middle section 18. Depending on the length of the terminals 16, the bending height H can have a value of 0.5 mm or more, wherein, for example, the length and / or width of the metal base structure 10 along the lateral direction B and the corresponding further lateral direction can have a value of 34 mm times 100 mm or 140 mm times 190 mm.

[0051] The pre-bent metal substrate structure 10 and its predetermined convex shape enable the provision of a semiconductor power module 1 that prevents the formation of cavities due to the arching on the back side of the substrate between the bottom surface 15 and the upper surface of the heat sink 3. Therefore, the described configuration of the metal substrate structure 10 and the semiconductor power module 1 can be pre-compensated for any deformation that may occur during assembly. Consequently, a very uniform and large surface contact between the bottom surface 15 of the metal substrate structure 10 and the upper surface of the heat sink 3 is feasible, resulting in a suitable thermal interface between the metal substrate structure 10 and the heat sink 3. This allows for improved heat dissipation during operation of the semiconductor power module 1. Due to the applied compressive load and the corresponding arching on the back side of the substrate, the thermal interface can also be thinner in the middle, resulting in better heat dissipation and enhanced reliability during operation, especially when the compressive load remains available during module operation.

[0052] However, the length of at least one terminal 16 itself can be longer, but not necessarily longer than the distance D between the top wall 21 and the metal top layer 11. Alternatively or additionally, additional elements or protrusions 25 may be present on the upper surface 14 of the metal top layer 11 and / or the lower surface 24 of the top wall 21, such as Figure 2 As illustrated in the exemplary diagram. The element or protrusion 25 may be formed as a single piece with the top wall 21, or it may be a separate part. Alternatively or additionally, there may be additional elements, such as chips, metal plates, auxiliary substrates, or bonding materials, or protrusions between the terminal 16 and the metal top layer 11, which may be formed as a single piece with the metal top layer 11 or as a separate part.

[0053] Therefore, relative to the stacking direction A, the at least one terminal 16 has a length that is coordinated with the distance D between the lower surface 24 of the top wall 21 and the upper surface 14 of the metal top layer 11 adjacent to the sidewall 22. The length of the at least one terminal 16 may be coordinated with one or more elements or protrusions 25 such that the at least one terminal 16 contributes to the bending and convex shape of the metal substrate structure 10 in a predetermined manner. As a result, and relative to the relaxed state of the assembled semiconductor power module 1, the distance of the intermediate segment 18 is greater than the distance D near the sidewall 22 on the outer side.

[0054] The corresponding manufacturing method steps can be followed as follows: Figure 4 The flowchart shown is illustrated. In step S1, a metal substrate structure 10, a housing 2, and terminals 16 may be formed and / or provided. At least one terminal 16 has a given length relative to the stacking direction A, which results in a total length at least 0.5 mm greater than the corresponding length of the sidewall 22 of the housing 2.

[0055] In step S2, the terminal 16, the housing 2 and the metal base structure 10 are coupled together such that the terminal 16 is arranged inside the housing 2 and is coupled to the lower surface 24 of the top wall 21 on the one hand and to the upper surface 14 of the metal top layer 11 on the other hand. Thereby, the terminal 16 provides a compression load on the metal base structure 10 such that the metal base structure is bent in a predetermined manner and a convex shape of the base side or bottom surface 15 is formed which interacts with the housing 2 and the terminal 16.

[0056] The terminal 16 can be made of copper or a copper alloy and can implement an auxiliary terminal or a main terminal. The thickness of the terminal 16 can have a value of 0.2 mm up to 3.0 mm with respect to the lateral direction B and / or the stacking direction A. This can apply to both the upright terminal body portion and / or the horizontal terminal leg portion of the L-shaped terminal 16, respectively. The horizontal and vertical sections can have equal or different thicknesses.

[0057] The described embodiment of the semiconductor power module 1 provides the opportunity to form a convex arch of the backside of the metal base structure 10 even after the complete module assembly process. A reliability improvement during module operation can be achieved by exposing a compression load on the center of the backplane such that the convex arch or at least a flat backside is maintained during long term operation. The semiconductor power module 1 can comprise an integrated structure of the module housing 2 and the terminal 16, wherein the respective terminal leg exposes a pressure or compression load on the metal base structure 10 such that the pressure provides a convex arch of the backside or bottom surface 15. The integrated structure of the module housing 2 and the terminal 16 can be implemented as one piece or building block, thereby forming a terminal or housing block. Thus, the terminal 16 can be formed as an integral part of such a housing block. The housing 2 can be screwed, clamped or glued to the metal base structure 10 such that the design of the housing block allows a compression load on the metal base structure 10.

[0058] The housing 2 is typically fixed to the metal base structure 10 by a screw connection. In such a case, corresponding screw holes are available in the metal base structure 10 and / or the housing 2. Nevertheless, other mounting methods are possible, like gluing or clamping. In case of screwing or clamping, a seal between the module housing 2 and the metal base structure 10 is present. This seal can be used to seal the remaining gap between the housing 2 and the metal base structure 10 such that the semiconductor power module 1 can be used in a process for gel or resin filling with liquid without leakage. Such a sealing material can comprise a rubber seal or other elastic material.

[0059] The described compression load on the upper surface 14 of the metal base structure 10 can be applied by the terminal 16 by the following design options, for example:

[0060] • The terminals 16 can have a length which is at least 0.5 mm larger than the distance between the module cover or top wall 21 and the upper surface 14 of the metal base plate structure 10 in a relaxed state before mounting of the housing 2. Here, the length of the terminals 16 can differ with respect to their position in the semiconductor power module 1 and the corresponding arch of the metal base plate structure 10.

[0061] • The compression load can be provided by a corresponding design of the housing 2, which can be realized, for example, by a pre-bending of the housing block or by a bent or protruding structure.

[0062] • The terminals 16 can incorporate a spring or stress relief structure which provides a pressure on the respective terminal leg with a better defined pressure force.

[0063] • An additional cushioning element can expose a pressure on the terminal portion with a better defined amount.

[0064] The metal base plate structure 10 can be formed by stamping a metal top layer 11 with a predefined metallization pattern, a backside metal sheet and a molded dielectric layer 12. Thus, the metal base plate structure 10 can be formed as a stamped and molded metal substrate (SMMS). Alternatively, the metal base plate structure 10 can be formed by lamination and etching of the metal top layer 11. The housing 2, which can form a power module housing consisting of a frame and a cover portion, incorporates the power and auxiliary terminals 16. Depending on the design, the housing 2 can be formed by one piece or two or more separate parts. The one-piece structure can be prepared by any kind of molding process of a resin material, such as transfer molding or injection molding, which embeds at least the upper portion of the respective terminal body of the terminals 16. A variety of resin materials, such as an epoxy resin and / or another thermoset or thermoplastic resin, are conceivable. The resin material can contain any kind of fillers, such as particles or fibers, but also chemical additives, for example, for improving the mechanical and / or thermal behavior. The connection between the respective terminal leg of the terminals 16 and the upper surface 14 of the metal base plate structure 10 can be realized by a variety of joining processes, such as soldering, ultrasonic welding, laser welding, gluing and / or sintering or other applicable processes. Dry contact is also possible. The terminals 16 are typically composed of copper or a copper alloy, which can be coated, for example, by nickel to prevent oxidation.

[0065] Figures 1 to 4 The embodiments shown in the figures represent exemplary embodiments of an improved metal base plate structure 10, semiconductor power module 1 and method of manufacturing thereof; thus, they do not constitute a complete list of all embodiments. For example, the actual arrangement and method can differ from the embodiments shown in terms of the metal base plate structure and power module.

[0066] Reference Signs

[0067] 1 semiconductor power module

[0068] 2 housing

[0069] 21 top wall of the housing

[0070] 22 side wall of the housing

[0071] 24 lower surface of the top wall

[0072] 25 element / protrusion

[0073] 3 heat sink

[0074] 4 lead

[0075] 10 metal base structure

[0076] 11 top metal layer

[0077] 12 dielectric layer

[0078] 13 bottom metal layer

[0079] 14 upper surface of the metal base structure

[0080] 15 bottom surface of the metal base structure

[0081] 16 terminal

[0082] 17 contact surface of the terminal

[0083] 18 intermediate section of the metal base structure

[0084] A stacking direction

[0085] B transversal direction

[0086] D distance between the top wall and the top metal layer

[0087] M middle axis

[0088] H bending height

[0089] S(i) steps of a method for manufacturing a semiconductor power module

Claims

1. A semiconductor power module (1), comprising: - a metal base structure (10) having a metal top layer (11), a metal bottom layer (13) and a dielectric layer (12) coupled to both the metal top layer (11) and the metal bottom layer (13) and interposed between both the metal top layer and the metal bottom layer with respect to a stacking direction (A) of the metal base structure (10), - a housing (2) configured to enclose electronics of the semiconductor power module (1), wherein the housing (2) comprises a top wall (21) and a side wall (22) and is coupled to the metal base structure (10) such that, with respect to the stacking direction (A), a predetermined distance (D) exists between a lower surface (24) of the top wall (21) and an upper surface (14) of the metal top layer (11) adjacent to the side wall (22), respectively, and - at least one terminal (16) arranged inside the housing (2), wherein the at least one terminal (16) is coupled to the lower surface (24) of the top wall (21) on the one hand and to the upper surface (14) of the metal top layer (11) on the other hand, and wherein, with respect to the stacking direction (A), a length of the at least one terminal (16) is configured in coordination with the distance (D) such that, due to the at least one terminal (16), the metal base structure (10) is bent in a predetermined manner and comprises a convex shape interacting with the housing (2).

2. The semiconductor power module (1) according to claim 1, wherein A total length comprising the length of the at least one terminal (16) is given such that, in a direction towards the metal top layer (11), the at least one terminal (16) protrudes at least 0.5 mm beyond a length of the side wall (22).

3. The semiconductor power module (1) according to claim 1, wherein The housing (2) and the metal base structure (10) are coupled to each other by means of at least one of screwing, gluing, clamping and sealing.

4. The semiconductor power module (1) according to claim 3, wherein The housing and / or the metal bottom layer (13) comprise a respective one or more screw holes, and the housing (2) and the metal base structure (10) are coupled to each other by means of a screw connection, wherein the screw connection is positioned in a respective area adjacent to the side wall (22) of the housing (2).

5. The semiconductor power module (1) according to any one of claims 1 to 4, wherein, The housing (2) is formed by means of molding, and wherein the at least one terminal (16) is integrally coupled to the top wall (21) and partially embedded in the molded housing (2).

6. The semiconductor power module (1) according to any one of claims 1 to 4, wherein The at least one terminal (16) is connected to the lower surface (24) of the top wall (21) and / or to the upper surface (14) of the metal top layer (11) by means of at least one of clamping, soldering, welding, gluing and sintering.

7. The semiconductor power module (1) according to any one of claims 1 to 4, comprising: two or more terminals (16) arranged inside the housing (2) and coupled to the lower surface (24) of the top wall (21) on the one hand and to the upper surface (14) of the metal top layer (11) on the other hand, wherein the two or more terminals (16) comprise different lengths between the lower surface (24) and the upper surface (14) with respect to the stacking direction (A).

8. The semiconductor power module (1) according to claim 7, wherein The two or more terminals (16) are symmetrically arranged inside the housing (2) with respect to a median axis (M) or a plane of symmetry along a transverse direction (B) perpendicular to the stacking direction (A).

9. The semiconductor power module (1) according to any one of claims 1 to 4, wherein The at least one terminal (16) comprises a spring or an elastic or stress relief structure configured to expose a pressure on the metal base plate structure (10) in a predetermined manner.

10. The semiconductor power module (1) according to any one of claims 1 to 4, comprising: a buffer element coupled to the at least one terminal (16), the buffer element being configured to expose a pressure on the terminal and / or the metal base plate structure (10) in a predetermined manner.

11. The semiconductor power module (1) according to any one of claims 1 to 4, wherein The at least one terminal (16) comprises an elongated terminal body and a plate-like terminal leg having a contact surface (17) contacting or facing the upper surface (14) of the metal base plate structure (10).

12. The semiconductor power module (1) according to claim 11, wherein The contact surface (17) of the terminal leg and / or a contact portion of the upper surface (14) of the metal top layer (11) is covered with a coating comprising at least one layer made of at least one of gold, silver and nickel.

13. The semiconductor power module (1) according to any one of claims 1 to 4, comprising: a heat sink (3) coupled to a bottom surface (15) of the metal bottom layer (13).

14. A method for manufacturing a semiconductor power module (1), comprising: providing a metal base plate structure (10) having a metal top layer (11), a metal bottom layer (13) and a dielectric layer (12) coupled to both the metal top layer (11) and the metal bottom layer (13) and interposed between both the metal top layer and the metal bottom layer with respect to a stacking direction (A) of the metal base plate structure (10), providing a housing (2) having a top wall (21) and side walls (22) having a given length, providing at least one terminal (16) having a given length, and - coupling together the at least one terminal (16), the housing (2) and the metal base structure (10) such that the at least one terminal (16) is arranged inside the housing (2) and is coupled to the lower surface (24) of the top wall (21) on the one hand and to the upper surface (14) of the metal top layer (11) on the other hand, wherein the length of the at least one terminal (16) is configured in coordination with the distance (D) between the lower surface (24) of the top wall (21) and the upper surface (14) of the metal top layer (11) adjacent to the side wall (22), and thereby a compression load is provided on the metal base structure (10) due to the at least one terminal (16) such that the metal base structure (10) is bent in a predetermined manner and comprises a convex shape interacting with the housing (2) and the at least one terminal (16).

15. The method of claim 14, wherein, The step of coupling together the at least one terminal (16), the housing (2) and the metal base structure (10) comprises: - forming the housing (2) by means of molding such that the at least one terminal (16) is integrally coupled to the top wall (21) and is partially embedded in the molded housing (2), and - coupling the molded housing (2) and the embedded at least one terminal (16) to the metal base structure (10) by means of at least one of screwing, clamping, gluing and sealing.

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