WO2022096263A1

WO2022096263A1 - Liquid-cooled heat sink, in particular for cooling power electronics components

Info

Publication number: WO2022096263A1
Application number: PCT/EP2021/079050
Authority: WO
Inventors: Franz Wetzl; Marco Lorenz; Christoph Jatzek
Original assignee: Robert Bosch Gmbh
Priority date: 2020-11-04
Filing date: 2021-10-20
Publication date: 2022-05-12
Also published as: CN116458274A; DE102020213849A1

Abstract

The present invention relates to a liquid-cooled heat sink for cooling a power electronics component (2) using a coolant that flows through the liquid-cooled heat sink, comprising an aluminum lower part (30), an aluminum upper part (31), an aluminum insert (32) arranged between the aluminum lower part (30) and the aluminum upper part (31), and a copper plate (7) arranged on the aluminum upper part (31), wherein the copper plate (7) is arranged in the region of the aluminum insert (32), and wherein the copper plate (7) is designed to secure the power electronics component (2).

Description

description

title

Liquid heat sink, in particular for cooling power electronics components

State of the art

The present invention relates to a liquid cooling body for cooling a power electronics component by means of a cooling liquid flowing through the cooling body. Furthermore, the invention relates to a power electronics arrangement comprising at least one power electronics component and a liquid heat sink.

Power semiconductors in power electronics carry high electrical currents, for example in vehicles with an electric drive or hybrid vehicles. Heat can be lost during operation, but this can only be dissipated over very small areas. Heat flow densities of up to 1,000 W/cm ² can be achieved here. For this reason, liquid cooling must be provided in order to avoid overheating, for example of a control unit in the vehicle. Furthermore, the control units of vehicles have to have a certain robustness in order to be able to withstand temperature fluctuations, vibrations, impacts or the like during operation without being damaged. Therefore, such liquid coolers are often designed as die-cast components, which in addition to being heavy also have a relatively high manufacturing cost. An alternative are aluminum coolers made of several components. These aluminum coolers are manufactured using a brazing process. However, the power electronics components must be connected to the aluminum cooler using a soft soldering process. For this reason, a soft-solderable coating must be provided on the aluminum cooler, for example a copper coating. However, such copper-coated aluminum coolers are very expensive to produce and, in particular, are expensive heat dissipation over such thin copper coatings is often not possible in a sufficient manner.

Disclosure of Invention

The liquid heat sink according to the invention for cooling a power electronics component by means of a liquid flowing through the heat sink with the features of claim 1 has the advantage that production of the heat sink can be made significantly cheaper. Furthermore, heat dissipation through the heat sink according to the invention can be significantly improved in comparison with the prior art. According to the invention, this is achieved in that the liquid cooling body is made of aluminum in several parts and has a copper plate for heat dissipation. More precisely, the heat sink comprises an aluminum lower part, an aluminum upper part and an aluminum insert, which is arranged between the aluminum lower part and the aluminum upper part. The copper plate is arranged on the aluminum upper part and further arranged in the area of the aluminum insert. Furthermore, the copper plate is set up for fastening the power electronics component. Thus, the heat generated by the power electronics component can first be transferred and dissipated to the copper plate and from the copper plate to the aluminum upper part and from there to the cooling liquid flowing through the aluminum insert. Furthermore, the copper plate makes it possible for the power electronics component or components to be easily soldered onto the aluminum heat sink by means of a soft soldering process. In this case, the copper plate, which is a separate component and has a certain thickness, can be connected to the aluminum heat sink in a relatively simple and cost-effective manner. Thus, the aluminum liquid heat sink with the additional copper plate offers a significantly improved heat dissipation option for power electronic components, which generate relatively large amounts of heat during operation. In particular, the heat spread of hotspot heat sources is improved by the copper plate. As a result, thermal damage to such power electronics components or adjacent components and/or the heat sink can be avoided.

The dependent claims show preferred developments of the invention. The copper plate is particularly preferably arranged in a flat recess in the aluminum upper part. The flat recess in the aluminum upper part reduces a wall thickness of the aluminum upper part, so that heat transfer from the copper plate through the aluminum upper part to the coolant can be significantly improved. Although the flat recess reduces the wall thickness of the aluminum upper part in this area, the necessary strength is still maintained by inserting the copper plate into the flat recess of the heat sink.

The copper plate is particularly preferably arranged in the planar recess in such a way that the copper plate does not protrude beyond a surface of the aluminum upper part. The copper plate is particularly preferably arranged in the surface recess in such a way that the surface of the aluminum upper part and the surface of the copper plate form a flat surface. The provision of the thicker copper plate means that no additional installation space is required perpendicular to the surface of the aluminum heat sink. A thickness of the aluminum upper part can thus remain constant.

More preferably, the copper plate is arranged only on a part of the surface of the aluminum top. As a result, it is preferably possible for the copper plate or a plurality of copper plates to be provided only at the positions at which power electronic components are provided. A further cost reduction can thereby be made possible, since the entire surface of the aluminum upper part is not covered by the thick copper plate.

The aluminum insert is preferably a strip fin component or a pin fin component. Alternatively, the aluminum insert is a meandering tube or channel or a plurality of parallel tubes.

More preferably, an inlet and an outlet are arranged directly on the liquid heat sink.

According to a further preferred embodiment of the invention, the copper plate has a smaller thickness than a thickness of the aluminum upper part. The copper plate preferably has a thickness of approximately 0.5 to 2.0 mm and the aluminum upper part has a thickness of approximately 1.5 to 2.5 mm. If provided a flat recess, the flat recess particularly preferably has a depth of 0.5 to 2.0 mm in order to be able to completely accommodate the copper plate.

Preferably, the heatsink comprises a plurality of copper plates on the aluminum top. The copper plates are preferably designed with the same dimensions in order to obtain the highest possible number of identical parts.

Furthermore, the present invention relates to a power electronics arrangement comprising at least one power electronics component and a liquid heat sink according to the present invention. The power electronics component is fixed to the heat sink by means of the copper plate of the liquid heat sink by means of a soft-soldered connection. The soft-soldered connection is formed at temperatures < 420°C.

More preferably, the power electronics arrangement comprises a plurality of power electronics components, each power electronics component being fixed to a separate copper plate on the liquid heat sink.

More preferably, all aluminum components of the liquid heat sink are connected by means of a hard-soldered connection, which is formed at temperatures of >590°C.

Furthermore, the invention relates to a control device, in particular for vehicles, with a power electronics arrangement according to the invention.

Brief description of the drawings

Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing is:

FIG. 1 shows a schematic top view of a liquid heat sink of a power electronics arrangement according to a first exemplary embodiment of the invention, FIG. 2 shows a schematic sectional view of the liquid heat sink from FIG. 1 with a power electronics component, and

Figure 3 is a schematic sectional view of a power electronics

Arrangement with a liquid heat sink according to a second embodiment of the invention.

Preferred Embodiments of the Invention

A power electronics arrangement 1 according to a first exemplary embodiment of the invention is described in detail below with reference to FIGS.

FIG. 1 shows the liquid heat sink 3 which comprises an aluminum lower part 30 , an aluminum upper part 31 and an aluminum insert 32 . As can be seen from FIG. 2, the aluminum insert 32 is arranged between the aluminum lower part 30 and the aluminum upper part 31 .

Furthermore, the liquid heat sink 3 includes a copper plate 7. The copper plate 7 is arranged on the aluminum upper part 31. As can be seen from FIG. 2, the copper plate 7 is arranged in the area of the aluminum insert 32 in order to enable improved heat dissipation.

The aluminum upper part 31 has a flat recess 13 to accommodate the copper plate 7 . As can be seen from Figure 2, a surface 7a of the copper plate 7 is flush with a surface 31a of the aluminum upper part 31. The surface 7a of the copper plate 7 and the surface 31a of the aluminum upper part 31 are therefore in a common plane E. The copper plate 7 is therefore not standing from the surface 31a.

As can be seen from FIG. 2, a power electronics component 2 is attached to the copper plate 7 . In this case, a soft-soldered connection 6 is formed between the power electronics component 2 and the copper plate 7 . This is necessary because the power electronics components 2 must be soft-soldered and a hard-soldered connection to aluminum is not possible without damaging the Power electronics component 2 is possible. The soft-soldered connection 6 is preferably formed at temperatures <420°C.

A cooling liquid flows through the liquid cooling body 3, with an inlet 33 and an outlet 34 for the cooling liquid being provided on the liquid cooling body 3, as shown in FIG.

In this exemplary embodiment, the aluminum insert 32 is a pin-fin component, which is arranged over as large an area as possible of the liquid heat sink 3 .

The aluminum components of the liquid heat sink 3 are connected to one another by means of hard-soldered connections 5, which are formed at temperatures of >590°C. The copper plate 7 is connected to the aluminum upper part 31 by means of a low-melting brazing connection 4, which is produced at temperatures of approx. 530°C. A low-melting braze for the low-melting braze joint 4 includes aluminum, silver, copper and silicon.

Thus, a brazed joint can be formed between the copper plate 7 and the aluminum top 31, which can be brazed below a critical temperature of 548°C, thereby avoiding that an undesirable aluminum-copper phase is generated during the brazing process, which occurs at temperatures above of 548°C occurs.

After the liquid heat sink 3 has been produced in this way, the power electronics component 2 can then be fixed on the copper plate 7 by means of the soft-soldered connection 6 .

A thickness of the copper plate 7 is about 0.5 to 2.0 mm. A thickness of the aluminum upper part is approximately 1.5 to 2.5 mm. So that the copper plate 7 does not protrude beyond the surface 31a of the aluminum upper part 31, the flat recess 13 has a depth T which corresponds to the thickness of the copper plate 7.

Thus, the liquid cooling body 3 according to the invention, through which a cooling liquid flows, enables improved heat spreading, since copper has a higher thermal conductivity than aluminum. The Copper plate 7 are equipped with an appropriate thickness to further improve heat dissipation. This makes it possible for the power electronics components to be designed overall for higher electrical currents with the same semiconductor area. Furthermore, the liquid heat sink 3 can be made possible by several aluminum components in a cost-effective manner by means of brazing processes at temperatures >590° C., which offers sufficient connection reliability of the aluminum components. Furthermore, a thermal expansion coefficient of the area of the liquid heat sink 3, which is connected to the power electronics component 2 by means of the soft solder, can be reduced by using thicker copper instead of aluminum. As a result, the reliability of the soft solder used to produce the soft-soldered connection 6 can be increased.

FIG. 3 shows a power electronics arrangement 1 with a power electronics component 2 and a liquid heat sink 3 according to a second exemplary embodiment of the invention. Identical or functionally identical parts are denoted by the same reference symbols as in the first exemplary embodiment. In contrast to the first exemplary embodiment, the aluminum insert 32 in the second exemplary embodiment is designed as a strip-fin insert. The strip fin insert can be securely connected to the aluminum lower part 30 by means of a hard soldering process, for example. As can be seen from FIG. 3, the aluminum insert 32 is also arranged below the copper plate 7 in this case. Furthermore, the copper plate 7 is fixed on the surface 31a of the aluminum upper part 31 by means of a low-melting brazing compound 4 . As a result, the copper plate 7 protrudes somewhat from the surface 31a of the aluminum upper part, but this means that a recess in the aluminum upper part 31 can be dispensed with, so that the production costs for this liquid cooling body 3 can be further reduced. This configuration is particularly suitable when there are no installation space problems with regard to the overhang of the copper plate 7 over the surface 31a. Furthermore, this also makes it possible to further reduce the cost of manufacturing the power electronics arrangement 1 .

Regarding the two exemplary embodiments, it should be noted that it is of course also conceivable for the planar recess 13 in the aluminum upper part 31 to have a smaller depth than the thickness of the copper plate 7 Copper plate 7 is only partially arranged in the flat recess 13 and partially projects beyond the surface 31a. It should also be noted that the liquid heat sink 3 can of course also be provided for cooling a large number of power electronics components 2, with each power electronics component 2 then preferably being assigned a separate, separate copper plate 7 and being fixed on the aluminum upper part 31.

Furthermore, it should be noted that a two-dimensional expansion of the copper plate 7 is preferably approximately the same size as a two-dimensional recess of the power electronics component 2. This means that the costs for the copper can be kept within limits. However, it is also possible that in the case of power electronic components, which dissipate a very high level of heat, the copper plate 7 also has a larger areal extent than the areal extent of the power electronic component 2 . This can ensure improved heat dissipation.

Claims

- 9 - Claims

1. liquid heat sink for cooling a power electronics component (2) by means of a cooling liquid flowing through the liquid heat sink, comprising

- an aluminum base (30),

- an aluminum top (31),

- an aluminum insert (32) which is arranged between the aluminum lower part (30) and the aluminum upper part (31), and

- a copper plate (7), which is arranged on the aluminum upper part (31),

- wherein the copper plate (7) is arranged in the area of the aluminum insert (32), and

- Wherein the copper plate (7) is set up for fastening the power electronics component (2).

2. Liquid heat sink according to claim 1, wherein the copper plate (7) is arranged in a flat recess (13) of the aluminum upper part (31).

3. Liquid heat sink according to claim 2, wherein the copper plate (7) is arranged in the planar recess (13) such that the copper plate (7) does not protrude beyond a surface (31a) of the aluminum upper part (31).

4. Liquid heat sink according to claim 3, wherein the surface (31a) of the aluminum top (31) and the surface (7a) of the copper plate (7) form a flat surface (E).

5. Liquid heat sink according to one of the preceding claims, wherein the copper plate (7) is arranged only on a part of the surface of the aluminum top part (31). Liquid heat sink according to one of the preceding claims, in which the aluminum insert (32) is a strip-fin component or a pin-fin component. Liquid heat sink according to one of the preceding claims, wherein the copper plate (7) has a smaller thickness than a thickness of the aluminum top part (31). Liquid heat sink according to one of the preceding claims, comprising a plurality of separate copper plates (7) which are arranged on the surface (31a) of the aluminum top part (31). Power electronics arrangement comprising at least one power electronics component (2) and a liquid heat sink (3) according to one of the preceding claims, the power electronics component (2) being attached to the copper plate (7) of the liquid heat sink (3) by means of a soft-soldered connection (6) is fixed. Power electronics arrangement according to Claim 9, comprising a plurality of power electronics components (2), each power electronics component (2) being fixed to a separate copper plate (7) on the heat sink (3).