Metal-ceramic substrate for use in a coolable power electronics component for electric cars and method for providing a coolable power electronics component for electric cars

Abstract

Metal-ceramic substrate 132 for use in a coolable power electronic component 100 for electric cars, comprising: - a ceramic layer 3 with a ceramic layer top side 3a and a ceramic layer bottom side 3b opposite the ceramic layer top side 3a; - a first metal layer 1, which is connected to the ceramic layer top side 3a via a first connecting layer 4a present at a first contact section 10 between the first metal layer 1 and the ceramic layer top side 3a; and - a second metal layer 2, which is connected to the ceramic layer underside 3b via a second connecting layer 4b present at a second contact section 20 between the second metal layer 2 and the ceramic layer underside 3b, and which second metal layer 2 has perforations 22 designed to be permeable to coolant 4 such that coolant 4 comes into contact with the ceramic layer underside 3b when passing through the perforations 22.

Description

[0001] The invention relates to a metal-ceramic substrate for use in a coolable power electronics component for electric cars and further to a method for providing a coolable power electronics component for electric cars according to the respective independent claim.

[0002] The invention lies in the technical field of power electronics for electric cars. The power electronics of an electric car play a crucial role in providing drive power. For the power electronics, which are composed of power electronic elements, to function properly, efficient cooling of the power electronics is crucial.

[0003] It is state of the art to arrange the power electronics elements on metal-ceramic substrates and to electrically contact them. Especially when using (half-sided) encapsulated power electronics elements, assembly can be particularly well automated and the power electronics can be designed in a compact manner. The power electronics element is then cooled indirectly via contact with the metal-ceramic substrate by first placing a heat exchanger on the side of the metal-ceramic substrate facing away from the power electronics element, and then bringing the coolant into contact with the heat exchanger.

[0004] For more efficient cooling, the state of the art proposes to design the surface of the heat exchanger as large as possible so that heat exchange with the coolant in contact can occur as quickly as possible. Surface structures for heat exchangers featuring nubs and / or fins, so-called "pin-fin" surfaces, are known for this purpose.

[0005] Metal-ceramic substrates are typically used, which have a layered structure, with a ceramic layer bonded to a metal layer on both the underside and the top side. When the ceramic layer is bonded to the metal layers, a bonding layer forms at each contact surface. This can be a solder layer, a sintered layer, or an oxidation layer. In so-called "active metal brazing," metals are used to create the bonding layer, which form a reactive bond with the ceramic layer. Various metals such as copper, silver, nickel, tungsten, molybdenum, or other refractory metals can be used.

[0006] Since the heat is generated in the power electronics element and transferred indirectly to the coolant via contact with the metal-ceramic substrate and then via the heat exchanger arranged on the metal-ceramic substrate, the thermal conductivity coefficients of all layers, especially the metal layers and the ceramic layers, as well as the connecting layers between the layers, especially between the metal layer and the ceramic layer and between the metal layer and the heat exchanger, are crucial. To efficiently dissipate heat along this heat path, all thermal conductivity coefficients should be as high as possible, and all thermal resistances as low as possible.

[0007] Due to their low thermal resistance, silicon nitride has proven advantageous as a material for the ceramic layer and copper as a material for the metal layers. However, better cooling in the current technology is hampered by the fact that the bonding layers between the ceramic layer and the metal layer, in particular, have a comparably high thermal resistance.

[0008] It is the object of the present invention to overcome the disadvantages of the prior art and in particular to provide a metal-ceramic substrate for use in a coolable power electronics component for electric cars and furthermore to provide a method for providing a coolable power electronics component for electric cars, each of which enables particularly good cooling of the power electronics component.

[0009] This object is achieved by a metal-ceramic substrate for use in a coolable power electronics component for electric cars and further by a method for providing a coolable power electronics component for electric cars according to the respective independent claim. Advantageous aspects form the subject matter of the respective dependent claims.

[0010] The invention comprises a metal-ceramic substrate for use in a coolable power electronic component for electric cars, comprising: - a ceramic layer with a ceramic layer top side and a ceramic layer bottom side opposite the ceramic layer top side; - a first metal layer connected to the ceramic layer top side via a first connecting layer present at a first contact portion between the first metal layer and the ceramic layer top side; and - a second metal layer which is connected to the ceramic layer underside via a second connecting layer present at a second contact section between the second metal layer and the ceramic layer underside, and which second metal layer has perforations designed to be permeable to coolant such that coolant comes into contact with the ceramic layer underside when passing through the perforations.

[0011] The ceramic layer can comprise aluminum nitride, aluminum oxide, or silicon nitride. The ceramic layer preferably comprises a material with a particularly low thermal resistance. The first metal layer and the second metal layer can each comprise copper, aluminum, or alloys. The first metal layer and the second metal layer preferably comprise a material with a particularly low thermal resistance.

[0012] The first connecting layer or the second connecting layer can be formed by a material-to-material bond between the first metal layer and the ceramic layer or between the second metal layer and the ceramic layer. The material-to-material bond can be formed at the first contact section between the first metal layer and the ceramic layer or at the second contact section between the second metal layer and the ceramic layer by a solder layer, a sintered layer, or an oxidation layer, thus providing the first connecting layer or the second connecting layer. One technique for producing the first and second connecting layers is so-called "active metal brazing." This involves using metals that form a reactive bond with the ceramic layer. Such metals can be copper, silver, nickel, tungsten, molybdenum, or other refractory metals.

[0013] Particularly efficient cooling can be achieved by having perforations in the second metal layer that are permeable to coolant, so that coolant comes into contact with the underside of the ceramic layer when passing through the perforations. This particularly efficient cooling is achieved by the ability of the coolant, in direct contact with the underside of the ceramic layer, to absorb heat from the ceramic layer directly and particularly quickly. This particularly efficient cooling is further achieved by the fact that the size and number of perforations can reduce the cross-sectional area of ​​the second connecting layer between the ceramic layer and the second metal layer, and thus also the thermal resistance of the second connecting layer.

[0014] For use in a power electronics component, a power electronics element, for example an inverter, can be arranged on the first metal layer of the metal-ceramic substrate and electronically contacted.

[0015] For cooling, coolant can be provided in a coolant flow directed so as to pass through the perforations substantially perpendicularly or at an angle between 5° and 90° to the ceramic layer underside and come into contact with the ceramic layer underside.

[0016] According to an advantageous aspect, the perforations form a perforation grid. A regular perforation grid can be produced particularly easily by selectively etching the second metal layer using a mask. This allows the size and number of perforations to be easily adjusted.

[0017] According to a further advantageous aspect, between 40% and 60%, preferably between 60% and 80%, particularly preferably between 80% and 100% of the perforations are arranged in (parallel) rows in the plane of the second metal layer.

[0018] These perforations, which are thus preferably arranged in alignment, allow for particularly efficient cooling, especially when coolant is provided in a coolant flow that flows (at least partially) along these rows. This results in even faster heat exchange on the underside of the ceramic layer.

[0019] According to a particularly advantageous aspect, each perforation has a width in a range of 1 mm to 4 mm and a length in a range of 1 mm to 4 mm. By not making the perforations any larger, it can be ensured that the second bonding layer between the second metal layer and the underside of the ceramic layer is sufficiently stable.

[0020] According to a preferred aspect, the perforations are designed to remove at least 20%, preferably at least 40%, particularly preferably at least 60%, and most particularly preferably a region between 40% and 60% of the cross-sectional area of ​​the second metal layer. The larger the removed cross-sectional area of ​​the second metal layer, the better the cooling can be achieved. At the same time, not too much of the cross-sectional area must be removed to ensure good contact. Also, to avoid stresses in the metal-ceramic substrate, in the event of a large temperature gradient between the first metal layer and the second metal layer when used in a cooled power electronics component, the proportion of the removed cross-sectional area of ​​the second metal layer must not be too large. If between 40% and 60% of the cross-sectional area of ​​the second metal layer is removed, all three of the above aspects are optimally taken into account.

[0021] According to a further preferred aspect, cooling elements are arranged on a side of the second metal layer facing away from the ceramic layer and / or on the underside of the ceramic layer, which cooling elements are formed protruding from the second metal layer. The cooling elements can be in the form of pins and have a length of at least 0.8 mm. Heat can be efficiently dissipated to the coolant via the surface of the cooling elements. The cooling elements can be arranged in a comb-like arrangement, so that a coolant flow flows through this comb-like arrangement.

[0022] According to a particularly preferred aspect, the cooling elements are arranged adjacent to the perforation.

[0023] According to an advantageous aspect, the cooling elements are applied to the second metal layer by means of 3D printing.

[0024] The invention further comprises a method for providing a coolable power electronics component for electric cars, comprising the steps: A) Providing a metal-ceramic substrate as described above; B) arranging at least one power electronics element on the first metal layer of the metal-ceramic substrate; C) Providing the perforations of the second metal layer of the metal-ceramic substrate such that a coolant can come into contact with the ceramic layer underside through the perforations of the second metal layer.

[0025] By providing perforations in the second metal layer of the metal-ceramic substrate such that coolant can come into contact with the underside of the ceramic layer through the perforations in the second metal layer, particularly efficient cooling can be achieved. This particularly efficient cooling is achieved by the ability of the coolant, in direct contact with the underside of the ceramic layer, to absorb heat from the ceramic layer directly and particularly quickly. This particularly efficient cooling is further achieved by the fact that the size and number of perforations can reduce the cross-sectional area of ​​the second bonding layer between the ceramic layer and the second metal layer, and thus also the thermal resistance of the second bonding layer.

[0026] According to a further preferred aspect, the method comprises step D) of arranging a heat exchange element on a side of the second metal layer facing away from the ceramic layer and / or arranging (by 3D printing) cooling elements on a side of the second metal layer facing away from the ceramic layer and / or on the underside of the ceramic layer, wherein the cooling elements are formed so as to protrude from the second metal layer. The surface of the heat exchange element can have nubs and / or fins, a so-called "pin-fin" surface. Furthermore, the heat exchange element can have holes to ensure unhindered passage of coolant to the perforations of the second metal layer.

[0027] According to a preferred aspect, the method comprises step E) of arranging an encapsulation layer in sections around the metal-ceramic substrate and around the at least one power electronics element arranged thereon. Such encapsulation simplifies automated production of the power electronics component.

[0028] According to a particularly preferred aspect, the coolant can come into contact with the ceramic layer underside in a directed flow substantially perpendicular to the ceramic layer underside through the perforations of the second metal layer. In combination with this or alternatively, between 40% and 60%, preferably between 60% and 80%, particularly preferably between 80% and 100% of the perforations are arranged in rows in the plane of the second metal layer, and the coolant is provided in a flow directed substantially along these rows. When using a coolant flow, it is particularly advantageous if the shape of the perforations is adapted to the coolant flow.

[0029] The invention is explained in more detail below using examples. These show: Fig. 1 Schematic sectional view of a cooled power electronics component for electric cars with a metal-ceramic substrate from the prior art; Fig. 2 Schematic sectional view of a cooled power electronics component for electric cars with a metal-ceramic substrate in a preferred embodiment; Fig. 3 Schematic front view of the metal-ceramic substrate from Fig. 2; Fig. 4 Schematic front view of a preferred second metal layer for the metal-ceramic substrate of Fig. 3; Fig. 5 Schematic sectional view of a cooled power electronics component for electric cars with a metal-ceramic substrate in an advantageous embodiment; and Fig. 6 Schematic front view of the metal-ceramic substrate from Fig. 5.

[0030] In the Fig. 1 - 6 each show a coordinate system along the shown width direction B, depth direction T and height direction H.

[0031] Fig. 1 shows a schematic sectional view of a cooled power electronics component 100 for electric cars with a metal-ceramic substrate 132 from the prior art.

[0032] The metal-ceramic substrate 132 comprises a full-surface ceramic layer 3 with a ceramic layer top side 3a and a ceramic layer bottom side 3b opposite the ceramic layer top side 3a. Furthermore, the metal-ceramic substrate 132 comprises a full-surface first metal layer 1, which is connected to the ceramic layer top side 3a via a first connecting layer 4a present at a first contact section 10 between the first metal layer 1 and the ceramic layer top side 3a. Furthermore, the metal-ceramic substrate 132 also comprises a full-surface second metal layer 2, which is connected to the ceramic layer bottom side 3b via a second connecting layer 4b present at a second contact section 20 between the second metal layer 2 and the ceramic layer bottom side 3b.

[0033] A power electronics element 0 is arranged on the first metal layer 1 of the metal-ceramic substrate 132 and is electronically contacted. An encapsulation layer 101 is arranged in sections and on one half of the metal-ceramic substrate 132 and around the at least one power electronics element 0 arranged thereon.

[0034] The power electronics component 100 has a heat exchange element 104 arranged on the side 103 of the second metal layer 2 facing away from the ceramic layer 3. For cooling, a coolant 4 is provided, which is in contact only with the heat exchange element 104.

[0035] Fig. 2 and Fig. 3 are described together below. Fig. 2 a schematic sectional view of a cooled power electronics component 100 for electric cars with a metal-ceramic substrate 132 in a preferred embodiment and Fig. 3 a schematic front view of the metal-ceramic substrate 132 of Fig. 2.

[0036] The metal-ceramic substrate 132 comprises a ceramic layer 3 made of silicon nitride with a ceramic layer top side 3a and a ceramic layer bottom side 3b opposite the ceramic layer top side 3a.

[0037] Furthermore, the metal-ceramic substrate 132 comprises a first metal layer 1 made of copper, which is connected to the ceramic layer top side 3a via a first connecting layer 4a present at a first contact section 10 between the first metal layer 1 and the ceramic layer top side 3a.

[0038] Furthermore, the metal-ceramic substrate 132 also comprises a second metal layer 2 made of copper, which is connected to the ceramic layer underside 3b via a second connecting layer 4b present at a second contact section 20 between the second metal layer 2 and the ceramic layer underside 3b.

[0039] The first connecting layer 4a and the second connecting layer 4b are each formed by a material bond at the first contact section 10 between the first metal layer 1 and the ceramic layer 3, and at the second contact section 20 between the second metal layer 2 and the ceramic layer 3, respectively, by means of active metal brazing. Silver was used to form a reactive bond with the ceramic layer 3.

[0040] The second metal layer 2 has perforations 22 which are designed to be permeable to coolant 4, such that coolant 4 comes into contact with the ceramic layer underside 3b when passing through the perforations 22. This achieves particularly efficient cooling, since on the one hand the coolant 4 in direct contact with the ceramic layer underside 3b can absorb heat from the ceramic layer 3 directly and particularly quickly, and on the other hand the perforations increase the cross-sectional area of ​​the second connecting layer 4b between the ceramic layer 3 and the second metal layer 2 and thus also the thermal resistance of the second connecting layer 4b in comparison to the Fig. 1 shown prior art.

[0041] The perforations 22 form a regular perforation grid, which was created by selectively etching the second metal layer 2 using a mask. Each perforation 22 has a width of 1 mm and a length of 2 mm. This ensures the stability of the second connecting layer 4b between the second metal layer 2 and the ceramic layer underside 3b.

[0042] The perforations 22 shown are all, i.e., 100%, arranged in parallel rows along the depth direction T, which lies in the plane of the second metal layer 2. These aligned perforations 22 allow for particularly efficient cooling when, as in this exemplary embodiment, coolant 4 is provided in a coolant flow partially aligned along this depth direction T. This results in an even faster heat exchange on the underside 3b of the ceramic layer.

[0043] Since a temperature gradient occurs between the first metal layer 1 and the second metal layer 2 during operation of the power electronics component 100, the perforations 22 are designed to avoid stresses in the metal-ceramic substrate 132 in such a way as to exclude only 50% of the cross-sectional area of ​​the second metal layer 2.

[0044] A power electronics element 0 is arranged on the first metal layer 1 of the metal-ceramic substrate 132 and is electronically contacted. An encapsulation layer 101 is arranged in sections and on one half of the metal-ceramic substrate 132 and around the at least one power electronics element 0 arranged thereon.

[0045] For cooling, coolant 4 is provided in a coolant flow partially aligned along the depth direction T, which passes through the perforations 22 at an angle of 25° to the ceramic layer underside 3b and comes into contact with the ceramic layer underside 3b.

[0046] The power electronics component 100 has a heat exchange element 104 arranged on the side 103 of the second metal layer 2 facing away from the ceramic layer 3. The surface of the heat exchange element 104 has fins for more efficient heat exchange with the coolant 4. Furthermore, the heat exchange element 104 has holes to ensure unhindered passage of the coolant 4 to the perforations 22 of the second metal layer 2.

[0047] The illustrated embodiment of the cooled power electronics component 100 was provided by a method comprising the steps: A) Providing the metal-ceramic substrate 132 as described above; B) Arranging the power electronics element 0 on the first metal layer 1 of the metal-ceramic substrate 132; C) Providing the perforations 22 of the second metal layer 2 of the metal-ceramic substrate 132 such that the coolant 4 comes into contact with the ceramic layer underside 3b through the perforations 22 of the second metal layer 2; D) Arranging the heat exchange element 104 on the side 103 of the second metal layer 2 facing away from the ceramic layer 3; and E) Arranging the encapsulation layer 101 in sections around the metal-ceramic substrate 132 and around the power electronics element 0 arranged thereon.

[0048] Fig. Fig. 4 shows a schematic front view of a preferred second metal layer 2 for the metal-ceramic substrate 132 of Fig. 3. The perforations 22 form a different regular perforation grid than in the second metal layer 2 in Fig. 3. Each perforation 22 has a width of 1 mm and a length of 4 mm. A metal-ceramic substrate 132 provided with this second metal layer 2 can also be used for the cooled power electronics component 100 in Fig. 2 can be used.

[0049] Fig. 5 and Fig. 6 are described together below. Fig. 5 a schematic sectional view of a cooled power electronics component 100 for electric cars with a metal-ceramic substrate 132 in an advantageous embodiment and Fig. 6 a schematic front view of the metal-ceramic substrate 132 of Fig. 5.

[0050] With reference to the figure description of the Fig. 2 and Fig.3, the cooled power electronics component 100 and the metal-ceramic substrate 132 are substantially identical in construction to the power electronics component 100 and metal-ceramic substrate 132 shown there, with the difference that no heat exchange element 104 is arranged on the side 103 of the second metal layer 2 facing away from the ceramic layer 3, but rather cooling elements 21 are arranged on the side 103 of the second metal layer 2 facing away from the ceramic layer 3 by means of 3D printing.

[0051] The cooling elements 21 are formed protruding from the second metal layer 2 and are in the form of pins with a length of 1.2 mm. The cooling elements 21 are arranged in parallel rows adjacent to the perforation 22 and arranged in a comb-like arrangement, so that the coolant 4 flows through this comb-like arrangement in a coolant flow and efficiently dissipates heat.

[0052] The illustrated embodiment of the cooled power electronics component 100 was provided by a method comprising the steps: A) Providing the metal-ceramic substrate 132 as described above; B) Arranging the power electronics element 0 on the first metal layer 1 of the metal-ceramic substrate 132; C) Providing the perforations 22 of the second metal layer 2 of the metal-ceramic substrate 132 such that the coolant 4 comes into contact with the ceramic layer underside 3b through the perforations 22 of the second metal layer 2; D) Arranging the cooling elements 21 by 3D printing on the side of the second metal layer 2 facing away from the ceramic layer 3, wherein the cooling elements 21 are formed protruding from the second metal layer 2; and E) Arranging the encapsulation layer 101 in sections around the metal-ceramic substrate 132 and around the power electronics element 0 arranged thereon. Reference symbol 0 power electronics element 1 first metal layer 2 second metal layer 3 ceramic layer 3a Ceramic layer top 3b Ceramic layer underside 4a first connection layer 4b second connection layer 10 first contact section 20 second contact section 100 power electronics components 101 Encapsulation layer 103 side of the second metal layer facing away from the ceramic layer 104 Heat exchange element 132 Metal-ceramic substrate

Claims

[1] A metal-ceramic substrate (132) for use in a coolable power electronic component (100) for electric cars, comprising: - a ceramic layer (3) with a ceramic layer top side (3a) and a ceramic layer bottom side (3b) opposite the ceramic layer top side (3a); - a first metal layer (1) which is connected to the ceramic layer top side (3a) via a first connecting layer (4a) present at a first contact section (10) between the first metal layer (1) and the ceramic layer top side (3a); and - a second metal layer (2) which is connected to the ceramic layer underside (3b) via a second connecting layer (4b) present at a second contact section (20) between the second metal layer (2) and the ceramic layer underside (3b), and which second metal layer (2) has perforations (22) designed to be permeable to coolant (4) such that coolant (4) comes into contact with the ceramic layer underside (3b) when passing through the perforations (22). [2] Metal-ceramic substrate (132) according to claim 1, wherein the perforations (22) form a perforation grid. [3] Metal-ceramic substrate (132) according to one of the preceding claims, wherein between 40% and 60%, preferably between 60% and 80%, particularly preferably between 80% and 100% of the perforations (22) are arranged in rows in the plane of the second metal layer (2). [4] Metal-ceramic substrate (132) according to one of the preceding claims, wherein the perforations (22) are formed in such a way as to exclude at least 20%, preferably at least 40%, particularly preferably at least 60%, most particularly preferably a region between 40% and 60% of the cross-sectional area of ​​the second metal layer (2). [5] Metal-ceramic substrate (132) according to one of the preceding claims, wherein cooling elements (21) are arranged on a side of the second metal layer (2) facing away from the ceramic layer (3) and / or on the ceramic layer underside (3b), which cooling elements (21) are formed protruding from the second metal layer (2). [6] Metal-ceramic substrate (132) according to claim 5, wherein the cooling elements (21) are arranged adjacent to perforation (22). [7] Metal-ceramic substrate (132) according to claim 5 or 6, wherein the cooling elements (21) are applied to the second metal layer (2) by means of 3D printing. [8] A method for providing a coolable power electronic component (100) for electric cars, comprising the steps: A) providing a metal-ceramic substrate (132) according to any one of the preceding claims; B) arranging at least one power electronics element (0) on the first metal layer (1) of the metal-ceramic substrate (132); C) Providing the perforations (22) of the second metal layer (2) of the metal-ceramic substrate (132) such that a coolant (4) can come into contact with the ceramic layer underside (3b) through the perforations (22) of the second metal layer (2). [9] Method according to claim 8, comprising the step D) of arranging a heat exchange element (104) on a side (103) of the second metal layer (2) facing away from the ceramic layer (3) and / or of arranging cooling elements (21) on a side of the second metal layer (2) facing away from the ceramic layer (3) and / or on the ceramic layer underside (3b), wherein the cooling elements (21) are formed protruding from the second metal layer (2). [10] Method according to one of claims 8 or 9, wherein - the coolant (4) can come into contact with the ceramic layer underside (3b) in a directed flow substantially perpendicular to the ceramic layer underside (3b) through the perforations (22) of the second metal layer (2); and / or - between 40% and 60%, preferably between 60% and 80%, particularly preferably between 80% and 100% of the perforations (22) are arranged in rows in the plane of the second metal layer (2) and the coolant (4) is provided in a flow directed substantially along these rows.

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