WO2018145910A1

WO2018145910A1 - Cooling apparatus, electronics assembly, and method of producing the same

Info

Publication number: WO2018145910A1
Application number: PCT/EP2018/051813
Authority: WO
Inventors: Hans-Heinrich Angermann; Stefan Schmidgall
Original assignee: Mahle International Gmbh
Priority date: 2017-02-09
Filing date: 2018-01-25
Publication date: 2018-08-16
Also published as: DE102017202066A1

Abstract

The present invention relates to a cooling apparatus (2) for cooling power electronics (3), having a flat tube (5) for carrying a coolant (6), wherein the flat tube (5) consists of an aluminum material. Warping of the cooling apparatus (2) can be prevented if an electrically insulating Al2O3 ceramic plate (9) is attached by brazing to the exterior of the flat tube (5) on an upper face (7) and another is attached by brazing to the exterior of the flat tube (5) on a lower face (8), wherein at least one of the ceramic plates (9) comprises a metal coating (11) on an outer face (10) facing away from the flat tube (5) for mounting components (4) of power electronics (3) by soft soldering, the metal coating consists of Al or Cu and, in the case of a Cu coating, a DCB process is used.

Description

Cooling device, electronic assembly and associated manufacturing method

The present invention relates to a cooling device for cooling power electronics. The invention also relates to an electronic device with such a cooling device. Finally, the invention relates to a method for producing a cooling device for cooling power electronics.

A power electronics usually consists of a variety of electronic and / or electrical components which are arranged on a circuit board and interconnected by interconnects. The conductor tracks can be expediently formed directly on the board, so-called printed circuit board. During operation of the power electronics, their components generate heat that must be dissipated to increase the life of the components or to avoid overheating of the components. For this purpose, it is basically possible to provide the respective board with a heat sink, which absorbs the heat and releases it into an environment, eg by convection and / or by radiation. A significantly better cooling performance can be achieved if the board is coupled to a heat exchanger through which a gaseous or liquid coolant flows, so that the heat can be transferred to the coolant and removed. Such a heat exchanger can be formed in the simplest case by a flat housing, which is usually in several parts, or by a flat tube, which is usually in one piece. To be able to firmly connect the respective board for a good heat transfer to the heat exchanger, a soldering process is considered in principle. In this case, a soft soldering process is preferred because at the higher temperature of a brazing process due to different thermal expansion coefficients, the risk of distortion of the heat exchanger and / or the board is increased. In high voltage applications, there is an additional requirement an electrical insulation between the usually metallic heat exchanger and the power electronics. This can be ensured, for example, by a ceramic plate or by a metallic plate with ceramic coating. In principle, it is conceivable to produce the heat exchanger from copper or from a copper alloy in order to be able to fasten the circuit board to it by means of a soldering process. However, copper is expensive and heavy compared to aluminum. Therefore, a heat exchanger made of aluminum or of an aluminum alloy is preferred. Due to an aluminum oxide layer which is unavoidable and difficult to remove, soft soldering can only be carried out with considerable effort. It is recommended for the connection of the electrically insulating boards a brazing process, but in which the above-mentioned risk of delay is given.

We are looking for a low-cost option for efficient cooling of power electronics, where a delay is negligible or at least reduced.

From DE 100 51 338 A1, a cooling device is known in which a stabilizing structure is used in a heat-flowable by a liquid cooling body, which is formed by a multi-part housing, and fixed by means of a brazing inside at an upper side and at an underside of the housing is. At the top of the housing, a ceramic plate is externally attached via an aluminum coating. This ceramic plate also has a further aluminum coating on its outer side facing away from the housing.

The known liquid cooling device builds in the region of the heat exchanger comparatively massive. In particular, large wall thicknesses are needed to avoid distortion of the housing during brazing. By the large wall thickness results in a correspondingly high material usage with relatively high costs.

From US 201 1/0235279 A1 a coolant flow-through flat tube is known, on the one or both sides a solder coated on both sides sheet is applied. On both sides of the sheets lot-coated electrical insulators are placed on the electronic components are placed. The flat tube is made of aluminum and the applied plates are also made of aluminum, but can also be made of copper. In the latter case, they are coated with a Cu solder. The sequence of solders, sheets and electrical insulators can also be laminated to the tube. The structure is relatively cumbersome, costly and builds quite high.

In US 2013/0277034 A1, which represents a further development of the above-mentioned US 201 1/0235279 A1, the metallic, solid sheet is replaced by a perforated sheet. However, this proposal has the same disadvantages as described above.

In JP 2006-294971 A, in the embodiment shown in FIG. 4, an AIN ceramic is applied on both sides to an aluminum flat tube on both sides, the double-sided DBA method (direct bonded aluminum) with 0.4 mm thick Al layers is occupied by means of an epoxy adhesive. In the embodiment shown in FIG. 5, on one side an AIN electrical insulator is soldered onto the aluminum flat tube by means of Al solder, while the opposite side is covered with a 1 mm thick Al 2 O 3 plate. The power module substrate is applied to the AIN ceramic side. A disadvantage is that AIN and the DBA method are very expensive.

The present invention is concerned with the problem of providing a cooling device of the type mentioned at the outset or an electronic device equipped therewith. Kanordnung or for an associated manufacturing method to provide an improved embodiment, which is characterized by low production costs, at the same time efficient cooling of the power electronics is possible. At the same time a high voltage application for the power electronics should be possible.

This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The invention is based firstly on the general idea of using a flat tube as the heat exchanger and fastening both on an upper side of the flat tube and on an underside of the flat tube an electrically insulating ceramic plate by external brazing on the flat tube. A flat tube is characterized in that it has a flat cross-section transversely to its longitudinal direction, in which it can be flowed through by the coolant. The flat cross-section is characterized by the fact that its width is at least twice as large as its height. The length of the flat tube is also at least twice as large as its height. Usually, the length of the flat tube is also greater than the width of the flat tube. Flat tubes, which are used in heat exchangers, usually have a comparatively small wall thickness of a maximum of 1 mm. Usual wall thicknesses are in a range of 0.1 to 0.5 mm. Thus, the flat tube, which consists of an aluminum material, requires little material, so that there is a cost advantage. In particular, the wall thickness of the flat tube is thereby approximately in the same size range as the wall thickness of the ceramic plate, which, for example, likewise amounts to a maximum of 1 mm and which may preferably be in a range of 0.2 to 0.7 mm. It has been found that distortion of the flat tube or the ceramic plates during brazing can be avoided if at the top and at the bottom respectively such a ceramic plate be attached by brazing. Accordingly, a cost-effective design for a cooling device for cooling a power electronics is presented here. Particularly cost is the formation of an Al / Cu soldering between a unplated AI flat tube and a ceramic which is coated at least on one side with Al or Cu. If a Cu coating is provided, this can preferably be realized as DCB, where DCB stands for Direct Copper Bonding. Then there is a DCB ceramic. A metal sheet or a metal laminate, also designed as a perforated plate, between the flat tube and the electrical insulation is not required and preferably does not exist.

The cooling device is particularly economical if the flat tube consists of an aluminum material. The flat tube is preferably produced in one piece. As a coolant, a liquid coolant is preferred. The ceramic plate consists of an electrically insulating ceramic. An inexpensive suitable ceramic is e.g. Al2O3. Then there is an AI2O3 ceramic. Preferably, both ceramic plates are made of the same ceramic. The use of expensive AIN can be dispensed with.

Particularly advantageously, the two above-mentioned variants can be combined, so that a one-sided or both sides coated with metal Al2O3 ceramic is used. If a Cu coating is used at least on one side, the DCB is used again, so that then there is a DCB-Al 2 O 3 ceramic, which can be particularly easily fixed to the unplated Al flat tube by means of a soldering process.

Particularly advantageously, at least one of the ceramic plates on a side remote from the flat tube outside a copper coating for attaching components of power electronics by soldering. To this In this way, the ceramic plate can be equipped particularly easily with the components of the power electronics in order to build up the power electronics.

A rib structure made of an aluminum material may be expediently arranged in the flat tube in order to improve the heat transfer between the coolant and the flat tube. The rib structure can be fixed inside by brazing on the upper side of the flat tube and inside on the underside of the flat tube. As a result, the heat transfer performance of the cooling device is significantly improved. At the same time, the rib structure also contributes to the dimensional stability during the brazing process. The wall thickness of the rib structure is usually smaller than the wall thickness of the flat tube and is for example a maximum of 0.1 mm.

Suitably, the two ceramic plates are about the same size, which compensate for the effects of different thermal expansion coefficients during brazing. Additionally or alternatively, it can be provided that the two ceramic plates extend over at least 75% of a length of the flat tube and / or over at least 75% of a width of the flat tube. In this way, a particularly large-area contact between ceramic plate and flat tube is realized, which improves the efficiency of the cooling effect.

Another embodiment provides that the respective ceramic plate has a metal coating on its inner side facing the flat tube. The metal coating facilitates the production of a braze joint with the flat tube. As a metal coating is basically any metal coating into consideration, which can be firmly connected by brazing with the flat tube, with appropriate solders and / or flux can be used. However, the metal coating is preferably an aluminum miniumbeschichtung, a nickel coating or more preferably a copper coating. The use of a copper coating is particularly advantageous since the ceramic plate then carries a copper coating both on its inside and on its outside, which reduces thermally induced stresses within the ceramic plate. In addition, the coated on both sides ceramic plate can be produced cheaper in this case over the relatively inexpensive DCB process.

Another embodiment provides that the flat tube outside and / or inside at the top and at the bottom each having a coating or a plating with aluminum solder. The aluminum solder simplifies the brazing of the flat tube with the preferably metallically coated ceramic plate.

An electronic assembly according to the invention is characterized in that it comprises a cooling device of the type described above. Furthermore, the electronic assembly comprises power electronics, which has a plurality of electrical and / or electronic components. Several or all of these components are then attached to at least one of these ceramic plates by soft soldering. In principle, it is possible that the entire power electronics is arranged only on one of the two ceramic plates. However, an embodiment in which the components of the power electronics are distributed over both ceramic plates is preferred. As a result, the structure of the electronic assembly is more compact overall.

The inventive method for producing such a cooling device for cooling a power electronics assumes that the two ceramic plates are fastened simultaneously by a brazing process on the flat tube. For this purpose, a flat tube made of an aluminum material is used, wherein in each case an electrically insulating ceramic plate, for example of AL2O3, on the outside of an upper side of the flat tube and externally placed on an underside of the flat tube. It is essential that the two ceramic plates are fastened simultaneously by brazing to said, opposite sides of the flat tube, as a result, compensate for the stresses caused by different thermal expansion effects quasi each other. Preferably, the brazing process is performed without flux. For this purpose, the components to be soldered together and the solder used are selected accordingly.

Advantageously, the respective ceramic plate may have a metal coating on its inner side facing the flat tube. This simplifies the soldering process and the quality of the soldered seam improves enormously. In principle, a direct soldering of the ceramic plate to the flat tube would also be possible if, for example, a suitable active solder, optionally in combination with a suitable flux, is used. Suitable metal coatings are those which are inexpensive and which use inexpensive solders and inexpensive fluxes or no fluxes. For example, the metal coating may be an aluminum coating or, preferably, a copper coating. Likewise, in principle, a nickel coating is conceivable.

Particularly advantageous is an embodiment in which the metal coating is designed as a copper coating. Such a copper coating can, for example, be cost-effectively produced before the brazing process by direct copper bonding, so-called DCB (Direct Copper Bonding), or by thermal spraying or by wet-chemical coating or by electroplating. Depending on the application, the copper coatings can be single-sided or double-sided. In another embodiment, the flat tube may have an aluminum braze coating or an aluminum braze cladding on the outside at the top and at the bottom at the bottom. This simplifies the brazing process.

According to another advantageous embodiment, a rib structure made of an aluminum material can be inserted into the flat tube before the brazing process. During the subsequent brazing process, the two ceramic plates and the rib structure are then fastened to the flat tube at the same time. The rib structure is fastened both on the upper side and on the underside of the flat tube. As mentioned, the rib structure increases the heat transfer between the flat tube and the coolant. At the same time, the rib structure stabilizes the comparatively thin-walled flat tube. The rib structure itself can also have a comparatively small wall thickness. Conceivable wall thicknesses of less than 0.1 mm. The brazing process can be two-stage, to realize possibly different brazing temperatures. Instead of a separate rib structure, which is inserted into the flat tube, it is in principle also possible to produce the flat tube with integrally formed rib structure, e.g. by an extrusion process.

According to a development, the flat tube can have an aluminum solder coating or an aluminum solder cladding on the inside and the underside. This simplifies the brazing process for attaching the rib structure to the flat tube.

According to another development it can be provided that the Al flat tube has an Al solder plating only on the inside, which faces the ribs. On the outer side or the outer sides, which face the electrically insulating Al2O3 plates, the flat tube does not have any solder plating. It is mixed with the DCB ceramics in a second soldering step at Tempe- connected below the Al / Al brazing temperature of about 600 ° C via an Al / Cu brazing.

Another embodiment provides that, after the brazing process, electrical and / or electronic components of power electronics are fastened to a side of the outer surface of at least one of the two ceramic plates facing away from the flat tube by a soldering process. In other words, the respective ceramic plate is fitted after the brazing process with the components of the power electronics.

The respective ceramic plate may have on its outer side a copper coating in order to simplify the assembly with the components of the power electronics.

For example, the copper coating, in particular before the brazing process, can be produced by direct copper bonding (DCB) or by thermal spraying or by wet-chemical coating or by electroplating. The respective copper coating can basically be full-surface. Preferably, the copper coating has a conductor track structure, which is required for the subsequent assembly with the components of the power electronics. Such structuring of a full surface copper coating is e.g. possible by etching.

In thermal spraying, the ceramic plate is first roughened wet-chemically or by laser ablation and then coated by thermal spraying with the respective metal, preferably with copper. The coating can be patterned using a mask, so it is possible, for example, on the respective outside, already aufzuspritzen strip conductors for power electronics. In wet-chemical coating, the ceramic plate is first roughened, for example by an etching process or by laser ablation. Thereafter, the roughened ceramic plate can be germinated, for example with palladium. Subsequently, the actual metallic coating takes place, for example, with nickel, copper or aluminum. As mentioned, copper is preferred here. Usually, two or more coatings are superimposed. Etching processes can then be used again for the printed conductor structure.

Alternatively, the copper coating, in particular after the brazing process, can be produced by screen printing. In conjunction with a corresponding mask or template, the desired conductor track structure can be realized particularly easily here.

The ceramic plate may be metallically coated on one or both sides, wherein the coating on both sides is preferred. A double-coated ceramic plate may be coated on both sides with the same metal or with different metals. A ceramic plate coated with different metals may be coated on one side with aluminum and on the other side with copper (DCB), the aluminum side being associated with the flat tube and the copper side with the power electronics.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained not only in the combination specified in each case, but which can be used in other combinations or alone, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

The sole FIGURE 1 shows a highly simplified, schematic sectional view of a cooling device in the manufacture of an electronic assembly.

According to FIG. 1, an electronic assembly 1 comprises a cooling device 2 and power electronics 3, which is not yet connected to the cooling device 2 in FIG. The power electronics 3 comprises a plurality of components 4, which are electrical and / or electronic components typically found in power electronics.

The cooling device 2 is used to cool the power electronics 3. The cooling device 2 has a flat tube 5, which serves to guide a gaseous or liquid coolant 6. Preferably, a liquid coolant 6 is used here. A flow through the flat tube 5 with the coolant 6 is indicated in Figure 1 by an arrow, which is denoted by 6. The flow through the flat tube 5 with the coolant 6 is usually carried out in the longitudinal direction of the flat tube 5, which lies in the drawing plane in FIG. 1 and runs parallel to the flow of the coolant 6 and thus horizontally. A height direction of the flat tube 5 extends vertically in Figure 1 and is also in the plane of the drawing. A width direction of the flat tube 5 extends perpendicular to the plane of the drawing. A cross section of the flat tube 5 extends transversely to the longitudinal direction of the flat tube 5 and thus also extends perpendicularly to the plane of the drawing of FIG. 1. The cross-section defines the width and the height of the flat tube 5. The cross-section is also flat and thus at least twice as wide as high. Thus, the flat tube 5 has a width which is at least twice as large as the height.

The flat tube 5 is made of an aluminum material and has an upper side 7 and a lower side 8. Top 7 and bottom 8 are each just configured in the example and run parallel to each other. The respective plane extends perpendicular to the plane of the drawing, ie parallel to the longitudinal direction and parallel to the width direction. Top 7 and bottom 8 are thus spaced from each other in the height direction. On the outside of the upper side 7 and on the outside of the lower side 8, an electrically insulating ceramic plate 9 is fixed in each case by brazing. In the example shown, each of these ceramic plates 9 has on its side facing away from the flat tube 5 outside 10 a metal coating 1 1, which is preferably designed as a copper coating.

In principle, an aluminum coating or a nickel coating is also conceivable here. The metal coating 1 1 or the copper coating is used to attach the components 4 of the power electronics 3, wherein preferably a soldering process is used.

In the example of Figure 1, a rib structure 12 is arranged in the flat tube 5, which also consists of an aluminum material. The rib structure 12 serves to improve the heat transfer between the coolant 6 and the flat tube 5 and has the added benefit of mechanical stabilization. The rib structure 12 is fixed inside on the top 7 and inside on the bottom 8 by brazing. For example, the rib structure 12 is folded in a rectangular shape so that it has upper contact surfaces 13, which rest flat against the upper side 7 and are fixed thereto by brazing. Likewise, the rib structure 13 has lower contact surfaces 14 which lie flat against the underside 8 and are secured thereto by brazing. In the example of FIG. 1, the two ceramic plates 9 are the same size. Furthermore, the two ceramic plates 9 extend approximately over the entire length of the flat tube 5. In the width direction, the two ceramic plates 9 may extend over at least 75% of the width of the flat tube 5, for example. The ceramic plates 9 preferably extend essentially over the entire width of the flat tube 5.

The respective ceramic plate 9 may have a metal coating 16 on its inner side 15 facing the flat tube 5. Furthermore, the flat tube 5 on the upper side 7 and on the underside 8 can have an aluminum solder coating 17 or aluminum solder plating 17 on the outside, and preferably also an aluminum solder coating 18 or an aluminum solder plating 18 inside. The metal coating 16 and the external aluminum solder cladding 17 are suitably coordinated so that a particularly efficient brazing connection between the respective ceramic plate 9 and the flat tube 5 can be produced. The metal coating 16 on the inner side 15 of the ceramic plate 9 is, for example, an aluminum coating. It is preferably a copper coating. For producing the electronic assembly 1, the components 4 are attached to the outside of the respective ceramic plate 9, in particular by soldering attached thereto. In the preferred example of FIG. 1, both ceramic plates 9 are used for mounting the components 4 of the power electronics 3. The attachment of the components 4 is indicated in Figure 1 by arrows 19.

Hereinafter, a method for manufacturing the cooling device 2 and the electronic assembly 1 will be explained in more detail. In this method, a flat tube 5 made of an aluminum material is used. First, a ceramic plate 9 are placed on the outside 7 on the outside and on the bottom 8 on the outside. Subsequently, the two ceramic plates 9 are simultaneously pressed by a hard Soldering attached to the flat tube 5. In principle, any suitable brazing process can be used. Different solders with or without flux can be used. Preferred are brazing processes that manage without flux.

As mentioned, the respective ceramic plate 9 expediently has on its inner side 15 a metal coating 16 in each case. The respective metal coating 16 can be designed as a nickel coating or aluminum coating or as a copper coating. Particularly advantageous is an embodiment as a copper coating. Such a copper coating can be embodied as direct copper bonding, so-called "direct copper bonding", DCB for short.

As mentioned, the flat tube 5 may have the aluminum solder coating 17 on the outside and the aluminum solder coating 18 on the inside.

Optionally, the rib structure 12 made of aluminum material can be inserted into the flat tube 5 before the brazing process. During the subsequent brazing process, the ceramic plates 9 and the rib structure 12 are then fastened to the flat tube 5 at the same time.

If a copper-coated ceramic plate 9 on both sides and a rib structure 12 made of aluminum or aluminum alloy to be soldered to the flat tube 5 made of aluminum or aluminum alloy, advantageously two separate brazing are undertaken, since the Cu / Al brazing temperature about 30 - 40K under the AI / AI brazing temperature should be. Alternatively, in such a case, an extruded flat tube 5 may be used in which the rib structure 12 is formed integrally. As a result, the insertion and soldering, ie the AI / AI brazing the separate rib structure 12 can be omitted. A ceramic plate 9 which is coated on the inside 15 with aluminum and on the outside 10 with copper (DCB) is intended for an Al-Al soldering process, so that a one-shot soldering on the one hand the rib structure 12 on the flat tube 5 and on the other the ceramic plate 9 on the flat tube 5 is possible.

After the brazing process, the components 4 of the power electronics 3 can be arranged on the outside 10 of at least one of the two ceramic plates 9 and fixed by means of a soldering process. For this purpose, the respective ceramic plate 9 on the outside 10 have a suitable metal coating 1 1, which is preferably designed as a copper coating, e.g. via a DCB procedure.

On the respective ceramic plate 9, the metal coating 16 on the inside 15 or the metal coating 1 1 on the outside 10 can be attached, for example by direct copper bonding or by thermal spraying or by wet-chemical coating or galvanic. It is also conceivable to produce the respective metal coating 11 or 16 by screen printing.

As a ceramic material for the respective ceramic plate 9, for example, an aluminum oxide, preferably of the formula AI2O3 is. In principle, other ceramic, electrically insulating materials are conceivable, such as Si3N4 or SiC. The respective ceramic plate 9 may have in the height direction of the flat tube 5, for example, a wall thickness of a maximum of 1 mm. For example, the ceramic plate 9 has a wall thickness in the range of 0.3 to 0.7 mm. Preferably, a ceramic plate 9 coated on both sides is used. The use of a ceramic plate 9 coated on both sides with DCB is particularly advantageous. Such ceramic plates 9 are available inexpensively as circuit boards. On the outer side 10, the respective metal Layering 1 1, preferably the copper coating, already have the required interconnect structure for constructing the power electronics 3 or for interconnecting the components 4. On the inner side 15, however, the metal coating 16 may expediently be configured over its entire surface. It is also conceivable to replicate also on the inner side 15 of the conductor track structure.

The respective metal coating 11 or 16 can also be produced by means of thermal spraying. The ceramic plate 9, preferably again of Al 2 O 3, can first be roughened wet-chemically or by laser ablation and then thermally coated with the respective metal. The coating by means of thermal spraying can be structured by means of a mask, so that, for example, the conductor track structure on the outside 10 can already be produced. In principle, identical metal layers can be produced on the outside 10 and on the inside 15, for example made of aluminum or nickel or copper. It is also possible to produce on the outside 10 and on the inside 15, the metal coatings 1 1, 16 of different metals. For example, the metal coating 1 1 of the outside 10 may be configured as a copper coating to facilitate soldering with the components 4, while the metal coating 16 of the inside 15 is designed as an aluminum coating or nickel coating in order to simplify the brazing with the flat tube 5.

Alternatively, the respective ceramic plate 9 can be coated galvanically or wet-chemically. For this purpose, the ceramic plate 9 can first be roughened, for example by etching or by laser ablation. Subsequently, a germination can be carried out, for example with palladium. This is followed by a metallic coating, preferably galvanically. The wet-chemical coating or galvanic coating can also be realized with nickel, copper and aluminum. Likewise, two or more different metallic see coatings are stacked. The respective metallic coating typically has a thickness of less than 3 μm. Preferably, the layer thickness is in the range of 1 μηη to 2 μηη. The conductor track structure on the outside 10 can be introduced by a subsequent etching process. In principle, it is conceivable to dispense with the preceding etching if the electrical resistance of the metallic coating is sufficiently high by reducing the layer thickness to less than 1 μm. Electrical leakage currents are then comparatively low and negligible.

It is also conceivable to dispense with the metal coating 16 on the inner side 15 when the ceramic plate 9 is roughened on the inner side 15 and germinated with, for example, palladium. Even then, the ceramic plate 9 can be soldered with a suitable solder and optionally with a suitable flux. Likewise, the use of a Aktivlots is conceivable without the mentioned seeding.

The flat tube 5 is preferably made of a single piece of sheet metal. For example, a flat piece of sheet metal can be rolled up around the longitudinal axis of the flat tube 5 and fixed to the front side, ie in the circumferential direction, preferably welded, in order to form the flat tube 5. The weld then extends in the longitudinal direction of the flat tube 5. Likewise, an embodiment of the flat tube 5 as a so-called folding tube is possible in which instead of a weld seam, a fold is used to fasten the circumferentially adjacent ends of the sheet metal piece together. Furthermore, integrally drawn or extruded tubular body are conceivable. Theoretically, a flat tube 5 assembled from two half-shells is also conceivable. The individual parts of the flat tube 5 can also be secured together by brazing. This is then expediently carried out during brazing for fastening the ceramic plates 9 and possibly the rib structure 12. The wall thickness of the flat tube 5 and the wall thickness of the respective ceramic plate 9 are preferably in the same order of magnitude. This ranges from a minimum of 0.1 mm to a maximum of 1.0 mm. For example, the wall thickness of the flat tube 5 is in the range of 0.1 to 0.5 mm, while the wall thickness of the respective ceramic plate 9 is in the range of 0.2 to 0.7 mm. Preferably, therefore, the wall thicknesses of the flat tube 5 and the ceramic plates 9 are each less than 1 mm. The small wall thickness of the flat tube 5 reduces the manufacturing costs and improves the heat transfer to the coolant 6.

Claims

claims

1 . Cooling device (2) for cooling power electronics (3),

with a flat tube (5) for guiding a coolant (6),

- wherein the flat tube (5) consists of an aluminum material,

- Wherein externally on an upper side (7) of the flat tube (5) and externally on a lower side (8) of the flat tube (5) each an electrically insulating ceramic plate (9) is fixed by brazing,

- Wherein at least one of the ceramic plates (9) on a side facing away from the flat tube (5) outside (10) has a metal coating (1 1) for attaching components (4) of a power electronics (3) by soldering.

2. Cooling device according to claim 1,

characterized,

- That in the flat tube (5) a rib structure (12) made of an aluminum material for improving the heat transfer between the coolant (6) and the flat tube (5) is arranged,

- That the rib structure (12) is fixed inside the top (7) of the flat tube (5) and inside the bottom (8) of the flat tube (5) by brazing.

3. Cooling device according to claim 1 or 2,

characterized,

- That the two ceramic plates (9) consist of the same ceramic, and / or

- That the two ceramic plates (9) are the same size, and / or - That the two ceramic plates (9) extend over at least 75% of a length and / or a width of the flat tube (5).

4. Cooling device according to one of claims 1 to 3,

characterized,

the respective ceramic plate (9) has a metal coating (16) on its inner side (15) facing the flat tube (5).

5. Cooling device according to one of claims 1 to 4,

characterized,

the flat tube (5) has an aluminum solder coating (17, 18) or an aluminum solder cladding (17, 18) on the outside and / or inside on the top side (7) and on the bottom side (8).

6. Electronic assembly (1),

- with a cooling device (2) according to one of claims 1 to 5,

with power electronics (3) having a plurality of components (4),

- Wherein several or all of these components (4) are attached to at least one of the ceramic plates (9) by soldering.

7. Electronic assembly according to claim 6,

characterized,

in that in each case at least one component (4) of the power electronics (3) is attached to both ceramic plates (9) by soft soldering.

8. A method for producing a cooling device (2) for cooling power electronics (3),

in which a flat tube (5) made of an aluminum material is used, - In which each an electrically insulating ceramic plate (9) on the outside on an upper side (7) of the flat tube (5) and externally on a bottom (8) of the flat tube (5) is placed,

- In which the two ceramic plates (9) are fastened simultaneously by a brazing process on the flat tube (5).

9. The method according to claim 8,

characterized,

the respective ceramic plate (9) is provided with a metal coating (16) on its inner side (15) facing the flat tube (5) prior to attachment to the flat tube (5).

10. The method according to claim 8 or 9,

characterized,

the respective ceramic plate (9) is provided with a metal coating (16) on its inner side (15) facing the flat tube (5) and on the outer side (10) facing away from the flat tube (5).

1 1. Method according to claim 9 or 10,

characterized,

in that the metal coating is designed as a copper coating which is produced by direct copper bonding or by thermal spraying or by wet-chemical coating or by electroplating before the brazing process.

12. The method according to any one of claims 8 to 1 1,

characterized,

that the metal coating is designed as a copper, nickel or aluminum coating.

13. The method according to any one of claims 8 to 12,

characterized,

in that the metal coating of the ceramic plate (9) on the inner side (15) facing the flat tube (5) and the metal coating of the ceramic plate (9) on the outer side (10) facing away from the flat tube (5) with the same metal or two different Metals is formed.

14. The method according to any one of claims 8 to 13,

characterized,

the metal coating of the ceramic plate (9) on the inside (15) and on the outside (10) consists of copper or is formed with copper.

15. The method according to any one of claims 8 to 14,

characterized,

that the metal coating of the ceramic plate (9) on the inside (15) with aluminum and on the outside (10) is formed with copper or consists thereof.

16. The method according to any one of claims 8 to 15,

characterized,

in that the flat tube (5) is provided on the outside at the top (7) and at the bottom (8) with an aluminum solder coating (17) or with aluminum solder plating (17) before the ceramic plates (9) are attached.

17. The method according to any one of claims 8 to 16,

characterized,

in that before the brazing process a rib structure (12) of aluminum material is inserted into the flat tube (5), - That during brazing process at the same time for fixing the ceramic plates (9) and the rib structure (12) inside the top (7) of the flat tube (5) and on the underside (8) of the flat tube (5) is attached.

18. The method according to claim 17,

characterized,

in that the flat tube (5) is provided on the inside (7) and bottom (8) with an aluminum solder coating (18) or with an aluminum solder plating (18) before the insertion of the rib structure (12).

19. The method according to any one of claims 8 to 18,

characterized,

in that after the brazing process, components (4) of power electronics (3) are fastened to an outer side (10) of at least one of the two ceramic plates (9) facing away from the flat tube (5) by a soldering process.

20. The method according to claim 19,

characterized,

in that the respective ceramic plate (9) is provided with a metal coating (11) on its outside prior to the attachment of the components (4).

21. Method according to claim 20,

characterized,

the metal coating (11) is prepared by direct copper bonding or by thermal spraying or by wet-chemical coating or by electroplating before the brazing process.

22. The method according to claim 20,

characterized, the metal coating (11) is produced by screen printing after the brazing process.

23. The method according to any one of claims 20 to 22,

characterized,

the brazing process between the ceramic plate (9) and the flat tube (5) is based on a brazing joint of aluminum and aluminum by means of Al brazing alloy.

24. The method according to any one of claims 20 to 23,

characterized,

that the AI flat tube (5) is only covered on the inside facing the ribs with AI solder and only there takes place AI / AI brazing.

25. The method according to any one of claims 20 to 24,

characterized,

that the brazing process between ceramic plate (9) and flat tube (5) is based on a solder joint of aluminum and copper.