Cooling device and method for manufacturing the cooling device

Abstract

Cooling device (1) for cooling power electronics (7), - wherein the cooling device (1) has a heat-dissipating cooling plate (2), - wherein a contact surface (5) with several conductors (6) for fixing and contacting the power electronics (7) is fixed on the heat-dissipating cooling plate (2), - wherein the contact surface (5) is electrically insulated from the heat-dissipating cooling plate (2), - wherein at least one organic intermediate layer (3) is arranged between the heat-dissipating cooling plate (2) and the contacting surface (5), which is bonded to the heat-dissipating cooling plate (2), - wherein the organic intermediate layer (3) is an insulating layer (3b), and - wherein the contact surface (5) is electrically insulated from the heat-dissipating cooling plate (2) by the insulating layer (3b), characterized in that - that the contact surface (5) on the insulating layer (3b) is defined by a wet coating process or by physical vapor deposition, or - that the contact surface (5) is a conductor carrier (11) which is fixed to the insulating layer (3b) by means of an organic adhesive coating (12).

Description

[0001] The invention relates to a cooling device for cooling power electronics according to the preamble of claim 1. The invention also relates to a method for producing the cooling device.

[0002] DE 10 2010 061 011 A1 discloses a semiconductor assembly comprising a metal plate, a power element, a lead frame with a die support, a resin film with insulating properties, a control circuit that controls the power element, and a molding resin. The power element is mounted on the die support, and the die support is mounted on the metal plate with the resin film in between. The resin film covers at least a lower surface of the die support, while the lower surface of the resin film is smaller than an area of ​​the metal plate.

[0003] US Pat. No. 4,901,137 A discloses an electronic device in which a semiconductor component is mounted on a ceramic substrate made of sintered aluminum nitride with high thermal conductivity. A thermally stress-resistant adhesive with high thermal conductivity is used for bonding. The adhesive layer serves as a damping layer.

[0004] From US 2006 / 0 202 324 A1 a cooling device with a metallic heat-dissipating cooling plate is known, to which a ceramic plate with a contact surface and the soldered power electronics is fixed by an adhesive layer.

[0005] From US 2015 / 0 001 700 A1 a cooling device with a cooling plate is known to which a ceramic plate coated on both sides is soldered.

[0006] EP 2 071 620 A1 discloses a cooling device with a metallic cooling plate. An insulating layer is applied to the cooling plate, on which an electrical circuit and several LEDs are arranged.

[0007] US 5 879 808 A discloses an insulating layer made of parylene that can be applied to any substrate.

[0008] Power electronics are typically mounted on a double-sided copper-coated Al2O3 ceramic plate – a so-called DCB plate (DCB - Direct Copper Bonded) – and soldered to the plate on one side. After a functional test of the power electronics, the DCB plate is bonded to a copper plate on the underside, for example, using a soft soldering process below 450°C. The heat generated in the DCB plate by the power electronics can then be dissipated through the copper plate, thus cooling the power electronics. For cost and weight reasons, the copper plate is increasingly being replaced by an aluminum plate – or even an aluminum alloy plate. However, a soft soldering process between the copper-coated DCB plate and the aluminum plate is not readily possible due to an oxide layer on the aluminum plate.

[0009] Several approaches to solving this problem are known from the prior art. For example, a nickel plate is soldered to the aluminum plate in a controlled atmosphere, followed by the DCB plate, for example, using a well-known soft soldering process. The disadvantage is that the nickel plate has lower thermal conductivity than the aluminum plate, and soldering the nickel plate requires additional effort. Further attempts have been made to solder the DCB plate to the aluminum plate, for example, using a brazing process at approximately 600°C with an Al-Si solder. However, the high process temperature leads to residual stresses and damage in the DCB plate upon cooling. Direct soldering of the DCB plate to the aluminum plate is only possible at high process temperatures and for small geometries—for example, contacts. Therefore, none of these approaches leads to a satisfactory solution to the described problem.

[0010] The object of the invention is therefore to provide a cooling device and a method for producing the cooling device with which the aforementioned disadvantages are overcome.

[0011] This object is achieved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0012] The present invention is based on the general idea of ​​replacing soft soldering and brazing processes in the manufacture of a cooling device for cooling power electronics with an alternative joining method. The generic cooling device comprises a heat-dissipating cooling plate, on which a contact surface with multiple lines for securing and contacting the power electronics is fixed. The contact surface is electrically insulated from the heat-dissipating cooling plate. According to the invention, at least one organic intermediate layer is arranged between the heat-dissipating cooling plate and the contact surface, which is firmly bonded to the heat-dissipating cooling plate.

[0013] The heat-dissipating cooling plate can be made of copper, aluminum, an aluminum alloy, or an aluminum-plastic composite. The heat-dissipating cooling plate has high thermal conductivity, allowing the heat generated in the power electronics to be dissipated through the heat-dissipating cooling plate. The contact surface can be made of copper and has multiple conductors to which the power electronics are electrically connected, for example, using a soft soldering process at temperatures below 450°C. The power electronics can comprise multiple electronic units—such as transistors, converters, or capacitors—that are electrically interconnected in this way.

[0014] The cooling plate is appropriately electrically insulated from the contact surface so that leakage currents between the power electronics and the usually electrically conductive cooling plate are avoided.

[0015] According to the invention, the at least one organic intermediate layer is firmly bonded to the cooling plate. A firm bond between the cooling plate and the organic intermediate layer is created by atomic or molecular forces and cannot be broken without destroying the organic intermediate layer. The organic intermediate layer can, for example, be applied to the cooling plate using a coating process or can be firmly bonded to the cooling plate in the form of a thin film when heat is applied. Further components of the cooling device can be fixed to the organic intermediate layer, wherein the organic intermediate layer has a low process temperature and consequently the cooling device can be manufactured at a lower process temperature. This advantageously prevents, in particular, residual stresses in the other components of the cooling device.In addition, the organic intermediate layer reduces the number of manufacturing steps in the production of the cooling device, resulting in cost and time advantages.

[0016] According to an embodiment not covered by the invention, the organic intermediate layer is an adhesive layer, and the cooling device comprises a ceramic plate fixed to the adhesive layer. The contact surface is firmly bonded to the ceramic plate and electrically insulated from the heat-dissipating cooling plate by the ceramic plate. Advantageously, the ceramic plate can be fixed to the adhesive layer at a process temperature below 250°C, thereby advantageously avoiding residual stresses in the ceramic plate and the contact surface. Furthermore, conventionally required manufacturing steps are eliminated, thus reducing manufacturing complexity and costs.

[0017] The ceramic plate can, for example, be an Al2O3 ceramic plate to which the contact surface is firmly bonded. The contact surface can, for example, be a conductor carrier made from thick copper foil using a stamping process – a so-called leadframe – with multiple conductors, which is attached to the ceramic plate using an adhesive or joining process. Alternatively, the ceramic plate with the copper contact surface can be manufactured using a known manufacturing process, a so-called DCB plate, with reduced effort and cost. Compared to a conventional ceramic plate copper-plated on both sides – a DCB plate – the material and consequently also the manufacturing costs can be reduced. Alternatively, the ceramic plate can have a copper layer facing away from the contact surface.Such a ceramic plate with a copper layer and contact surface corresponds to a conventional double-sided copper-plated ceramic plate – a DCB plate – and is commercially available at a reasonable price. The ceramic plate is conveniently fixed to the adhesive layer with the copper layer, so that the contact surface is electrically insulated from the copper layer and the heat-dissipating cooling plate by the ceramic plate.

[0018] According to the invention, the organic intermediate layer is an insulating layer, and the contacting surface is electrically insulated from the heat-dissipating cooling plate by the insulating layer. The contacting surface can then be fixed directly to the insulating layer, eliminating additional layers—and in particular the ceramic plate—and resulting in a more compact cooling device. Furthermore, the number of manufacturing steps in the manufacture of the cooling device can be reduced, resulting in significant cost and time savings. To enable faster dissipation of the heat generated in the power electronics, it is advantageously provided that the heat-dissipating cooling plate and / or the insulating layer have a three-dimensional structure.

[0019] In a further development of the inventive solution, it is preferably provided that the insulation layer comprises or consists of parylene. Parylene has a dielectric strength of up to 5,000 volts and a surface resistance of approximately 10 15Ohm at a layer thickness of 50 µm. The parylene insulation layer electrically insulates the contact surface from the heat-dissipating and usually electrically conductive cooling plate, thus preventing leakage currents. Parylenes are also stable up to 350°C and exhibit comparatively high thermal conductivity. The heat generated in the power electronics can therefore be dissipated through the parylene insulation layer to the cooling plate, and even with high heat generation in the power electronics, the parylene insulation layer remains stable. Furthermore, parylenes exhibit low thermal expansion, so that residual stresses in the insulation layer and in the contact surface can be avoided.

[0020] According to the invention, the contacting surface is fixed to the insulation layer by a wet coating process or by physical vapor deposition. For example, the contacting surface can be applied to the insulation layer using a printing process. Advantageously, the contacting surface is produced in a single manufacturing step and fixed to the insulation layer, thereby reducing manufacturing costs and complexity. Alternatively, the contacting surface can be a conductor carrier fixed to the insulation layer by means of an organic adhesive coating. The conductor carrier—a so-called leadframe—can be manufactured, for example, from a thick copper foil using a stamping process. Advantageously, larger currents can flow through the conductor carrier, thus reducing overall heat generation in the line electronics.

[0021] Furthermore, it is advantageously provided that at least one electronic unit is fixed to the contacting surface, preferably using a soft soldering process. The electronic unit—for example, a transistor, a converter, or a capacitor—can be electrically connected to other electronic units via the lines of the contacting surface. Essentially, a so-called SMD component (SMD - Surface Mounted Device) is produced in this way. To protect the at least one electronic unit, the cooling device can have a protective coating that protects the at least one electronic unit from mechanical damage and external influences. The protective coating is preferably made of parylene, which is chemically resistant and electrically insulating. Alternatively or additionally, the protective coating can also be arranged on the intermediate layer or on the contacting surface and protects it from mechanical damage and external influences.

[0022] In the cooling device according to the invention, the contact surface on the cooling plate is defined over a large area, reducing the effort involved. The cooling device according to the invention enables efficient dissipation of the heat generated in the power electronics and can also be manufactured more compactly, cost-effectively, and quickly.

[0023] The invention also relates to a method for producing the cooling device described above. In the method according to the invention, an organic intermediate layer is applied to a heat-dissipating cooling plate, and then a contacting surface with multiple lines for securing and contacting power electronics is fixed to the heat-dissipating cooling plate. The organic intermediate layer can be applied to the cooling plate, for example, using a coating process or bonded to the cooling plate in the form of a thin film when heat is applied. Further components of the cooling device—including the contacting surface—can then be fixed to the organic intermediate layer. The organic intermediate layer can be fixed to the cooling plate at a low process temperature, and consequently the cooling device can be manufactured at a lower process temperature.In this way, residual stresses in the other components of the cooling device can be advantageously avoided.

[0024] According to an embodiment not falling within the scope of the invention, the organic intermediate layer is applied to the heat-dissipating cooling plate in the form of an adhesive layer, and a ceramic plate with the contact surface is fixed to the heat-dissipating cooling plate by means of the adhesive layer when heat is applied. Advantageously, the ceramic plate can be fixed to the adhesive layer even at a process temperature below 250°C, thereby advantageously avoiding residual stresses in the ceramic plate and in the contact surface. The ceramic plate can be made from Al2O3, for example, and the copper contact surface can be fixed to the ceramic plate in a cost-effective and effort-reducing manner using a known manufacturing process for a so-called DCB plate.A copper layer can also be applied to the ceramic plate, facing away from the contact surface, and the ceramic plate can be manufactured as a conventional DCB plate. The ceramic plate electrically insulates the contact surface from the typically electrically conductive cooling plate, thus advantageously preventing leakage currents between the power electronics and the cooling plate.

[0025] According to the invention, the organic intermediate layer is applied to the heat-dissipating cooling plate in the form of an insulating layer, preferably made of parylene, and the contacting surface is electrically insulated from the heat-dissipating cooling plate by the insulating layer. In this way, the contacting surface can be applied directly to the insulating layer, eliminating the need for additional layers—and in particular the ceramic plate. The cooling device can therefore be constructed more compactly, and the number of manufacturing steps can advantageously be reduced. The insulating layer made of parylene, which has a high dielectric strength and a high surface resistance, is preferably applied to the cooling plate. The insulating layer made of parylene electrically insulates the contacting surface from the heat-dissipating and usually electrically conductive cooling plate, advantageously preventing leakage currents.Parylene also remains stable up to 350°C and exhibits comparatively high thermal conductivity, allowing the heat generated in the power electronics to be quickly dissipated to the cooling plate. Furthermore, parylene exhibits low thermal expansion, thus advantageously preventing residual stresses in the insulation layer and the contact surface, even under higher thermal fluctuations.

[0026] The insulation layer can advantageously be applied to the heat-dissipating cooling plate by chemical vacuum vapor deposition. Polymers, preferably parylene, are deposited onto the cooling plate from a gas phase in a controlled atmosphere. Advantageously, a pattern mask can be applied to the heat-dissipating cooling plate prior to chemical vacuum vapor deposition. The polymers are applied to the cooling plate in a patterned manner through the pattern mask. After chemical vacuum vapor deposition, the pattern mask can be removed from the heat-dissipating cooling plate—automatically or manually. Alternatively, the insulation layer can be patterned after chemical vacuum vapor deposition. The insulation layer is preferably patterned using a laser by removing the insulation layer from the cooling plate in certain areas.

[0027] According to the invention, the contacting surface is applied to the insulation layer using a wet coating process or a physical vapor deposition process. For example, the contacting surface can be applied to the insulation layer using a printing process. In this way, the contacting surface is produced in a single manufacturing step and fixed to the insulation layer. This significantly reduces both manufacturing costs and manufacturing effort.

[0028] Alternatively, the contacting surface in the form of a conductor carrier is secured to the insulation layer using an organic adhesive coating. The conductor carrier—a so-called leadframe—can be produced, for example, from a thick copper foil using a stamping process. The conductor carrier advantageously conducts larger currents, and heat generation in the line electronics is thus significantly reduced. To ensure that the conductor carrier can be securely secured to the insulation layer, the insulation layer can be pretreated before the adhesive coating is applied to the insulation layer. The insulation layer is preferably pretreated using a plasma pretreatment process or an adhesive application process to improve the adhesive properties of the insulation layer.

[0029] Advantageously, before the contacting surface is fixed to the cooling plate, at least one electronic unit is fixed to the contacting surface, preferably using a soft soldering process. The soft soldering process is carried out at a process temperature below 450°C, and the at least one electronic unit is electrically connected to at least one line of the contacting surface. Several electronic units—for example, transistors, converters, or capacitors—can also be fixed to the contacting surface, which are interconnected via the contacting surface. Essentially, a so-called SMD component is produced in this way.

[0030] To protect the at least one electronic unit, a protective coating can advantageously be applied to the cooling plate after the contact surface has been defined. This protective coating can protect the at least one electronic unit from corrosion and provide electrical insulation from the outside. The protective coating is preferably made of parylene, which is chemically resistant and electrically insulating.

[0031] The process according to the invention allows the contact surface on the cooling plate to be defined over a large area with reduced effort. The process temperature is below 250°C, thus advantageously preventing residual stresses and the resulting damage to the cooling device. Furthermore, the process according to the invention allows the cooling device to be manufactured cost-effectively, quickly, and with reduced effort.

[0032] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0033] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0034] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0035] They show, schematically Fig. 1 a sectional view of a cooling device with a ceramic plate coated on both sides; Fig. 2 a sectional view of a cooling device with a ceramic plate coated on one side; Fig. 3 a sectional view of a cooling device according to the invention with a contact surface in the form of a conductor carrier; Fig. 4 a sectional view of a cooling device according to the invention with a directly applied contact surface.

[0036] Fig. 1 shows a sectional view of a cooling device 1 with a heat-dissipating cooling plate 2. An organic intermediate layer 3, which in this exemplary embodiment is an adhesive layer 3a, is firmly bonded to the cooling plate 2. A ceramic plate 4 is firmly bonded to the adhesive layer 3a. A contacting surface 5 has a plurality of lines 6 for securing and contacting a power electronics unit 7 and is firmly bonded to the ceramic plate 4. The ceramic plate 4 has a copper layer 8 facing away from the contacting surface 5 and, together with the contacting surface 5, corresponds to a conventional DCB plate. The ceramic plate 4 can be secured to the cooling plate 2 by means of the adhesive layer 3a at a process temperature below 250°C, whereby residual stresses in the ceramic plate 4, in the copper layer 8, and in the contacting surface 5 are advantageously avoided.

[0037] Several electronic units 9 of the power electronics 7 are mounted on the contact surface 5 with the lines 6. The electronic units 9 and the contact surface 5 are electrically insulated from the cooling plate 2 by the ceramic plate 4, so that no leakage currents occur in the cooling device 1.

[0038] To protect the electronic units 9, the cooling device 1 in this embodiment has a protective coating 10—preferably made of parylene—which protects the electronic units 9 from mechanical damage and external influences. Alternatively, the cooling device 1 can also be manufactured without the protective coating 10.

[0039] In Fig. Figure 2 shows a sectional view of the cooling device 1 with a different structure. In this embodiment, the ceramic plate 4 has no copper layer 8 and is fixed directly to the adhesive layer 3a. In comparison to the Fig. By using the ceramic plate 4 shown in Figure 1 with the copper layer 8, the material and consequently also the manufacturing costs can be reduced. To further reduce manufacturing costs, the cooling device 1 can also be manufactured without the protective coating 10, for example.

[0040] Fig. 3 shows a sectional view of the cooling device 1 according to the invention, wherein the organic intermediate layer 3 in this exemplary embodiment is an insulating layer 3b, preferably made of parylene. The insulating layer 3b electrically insulates the contacting surface 5 from the cooling plate 2. In this exemplary embodiment, the contacting surface 5 is a conductor carrier 11, which is produced, for example, from a thick copper foil using a stamping process. The conductor carrier 11 is fixed to the insulating layer 3b by an adhesive coating 12. The insulating layer 3b eliminates the need for additional layers—and in particular the ceramic plate 4—and the cooling device 1 is constructed more compactly.The electronic units 9 of the power electronics 7 are fixed to the contact surface 5, for example, in a soft soldering process below 450°C and, in this embodiment, are protected from mechanical damage and external influences by the protective coating 10.

[0041] Fig. Figure 4 shows the cooling device 1 according to the invention with the insulation layer 3b, wherein the contact surface 5 is fixed by a wet coating process or by a physical vapor deposition on the insulation layer 3b. In comparison to the cooling device shown in Fig. The cooling device 1 shown in Figure 3 has the adhesive coating 12, and the cooling device 1 is constructed even more compactly. To make the cooling device 1 even more compact, the cooling device 1 can, for example, be designed without the protective coating 10.

[0042] In the cooling device 1 according to the invention, the contact surface 5 with the power electronics 7 is fixed over a large area on the cooling plate 2, thus reducing the effort involved. The cooling device 1 according to the invention enables efficient dissipation of the heat generated in the power electronics 7 and can also be manufactured more compactly, cost-effectively, and quickly.

Claims

[1] Cooling device (1) for cooling a power electronics (7), - wherein the cooling device (1) has a heat-dissipating cooling plate (2), - wherein a contact surface (5) with a plurality of lines (6) for fixing and contacting the power electronics (7) is fixed on the heat-dissipating cooling plate (2), - wherein the contact surface (5) is electrically insulated from the heat-dissipating cooling plate (2), - wherein at least one organic intermediate layer (3) is arranged between the heat-dissipating cooling plate (2) and the contacting surface (5), which intermediate layer is firmly fixed to the heat-dissipating cooling plate (2), - wherein the organic intermediate layer (3) is an insulating layer (3b), and - wherein the contact surface (5) is electrically insulated from the heat-dissipating cooling plate (2) by the insulation layer (3b), characterized by , - that the contacting surface (5) on the insulation layer (3b) is fixed by a wet coating process or by physical vapor deposition, or - that the contacting surface (5) is a conductor carrier (11) which is fixed to the insulation layer (3b) by means of an organic adhesive coating (12). [2] Cooling device according to claim 1, characterized by that the insulation layer (3b) comprises parylene. [3] Cooling device according to one of claims 1 to 2, characterized by that the heat-dissipating cooling plate (2) and / or the insulation layer (3b) have a three-dimensional structure. [4] Cooling device according to one of the preceding claims, characterized by that at least one electronic unit (9) is fixed on the contacting surface (5), preferably using a soft soldering process. [5] Cooling device according to one of the preceding claims, characterized bythat the cooling device (1) has a protective coating (10). [6] A method for manufacturing the cooling device according to any one of claims 1 to 5, wherein - an organic intermediate layer (3) is applied to a heat-dissipating cooling plate (2), - subsequently, a contacting surface (5) with several lines (6) for fixing and contacting power electronics (7) is fixed on the heat-dissipating cooling plate (2), - wherein the organic intermediate layer (3) is applied in the form of an insulating layer (3b), preferably made of parylene, to the heat-dissipating cooling plate (2), - wherein the contact surface (5) is electrically insulated from the heat-dissipating cooling plate (2) by the insulation layer (3b), characterized by , - that the contacting surface (5) is applied to the insulation layer (3b) in a wet coating process or in a physical vapor deposition process, or - that the contacting surface (5) in the form of a conductor carrier (11) is fixed to the insulation layer (3b) by means of an organic adhesive coating (12). [7] Method according to claim 6, characterized by that the insulation layer (3b) is applied to the heat-dissipating cooling plate (2) by chemical vacuum vapor deposition. [8] Method according to claim 7, characterized by , - that a structural mask is arranged on the heat-dissipating cooling plate (2) before the chemical vacuum vapor deposition, - that after chemical vacuum vapor deposition, the structural mask is removed from the heat-dissipating cooling plate. [9] Method according to claim 7, characterized bythat after the chemical vacuum vapor deposition, the insulation layer (3b) is structured, preferably by means of a laser. [10] Method according to one of claims 6 to 9, characterized by that before the adhesive coating (12) is fixed on the insulation layer (3b), the insulation layer (3b) is pretreated, preferably in a plasma pretreatment process or in an adhesive application process. [11] Method according to one of claims 6 to 10, characterized by that before fixing the contacting surface (5) on the cooling plate (2), at least one electronic unit (9) is fixed to the contacting surface (5), preferably using a soft soldering process. [12] Method according to claim 11, characterized by that after the contacting surface (5) has been fixed on the cooling plate (2), a protective coating (10), preferably made of parylene, is applied.

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