Compact power electronics module with enlarged cooling surface

Abstract

A power electronic module comprises a first circuit carrier (5, 10, 11) and an electronic component (20, 30) arranged on the upper flat side of the first circuit carrier (5, 10, 11) in electrical contact and a first heat sink (40) in thermal contact with the lower side of the first circuit carrier (5, 10, 11), wherein the module comprises at least a second component (20, 30) arranged on the upper side of a second circuit carrier (5, 10, 11) and a second heat sink (40) arranged on the lower side of the second circuit carrier (5, 10, 11), wherein the first circuit carrier and the second circuit carrier (5, 10, 11) are arranged with their upper sides facing each other and between the components (20, 30) At least one central heat sink (60, 61, 63, 64) electrically insulated from the components (20, 30) is arranged in a space, wherein the components (20, 30) and the at least one central heat sink (60, 61, 63, 64) are embedded in a heat-conducting casting compound (50), wherein the module comprises circuit carriers (5, 10, 11) of number N≥3 together with components (20, 30) mounted on the upper side of the circuit carriers and cooling bodies (40) mounted on the lower side of the circuit carriers, and the side surfaces of the components (20, 30) pointing to each other are arranged to form a shape having an N-angle polygon as a cross-section around the central heat sink (60, 61, 63, 64).

Description

Technical Field

[0001] The invention relates to a power electronics module having a circuit carrier and electronic components arranged in electrical contact on the upper flat side of the circuit carrier, and a cooling body in thermal contact with the underside of the circuit carrier, ie connectable to the underside of the circuit carrier in a thermally conductive manner. Background Art

[0002] The components of power electronics include a component carrier (e.g. a printed circuit board) pre-structured for electrical connection, which is equipped with components suitable for high currents. The component represents the component of the power electronics module through which current flows during operation. As a result, the component forms a heat source due to ohmic power loss.

[0003] The other components of the module are used in particular to carry away the generated heat via contact surfaces with heat sinks, wherein the main heat sink is usually an air-cooled or water-cooled cooling body. In the case of high currents and at the same time insufficient cooling, there is a risk of component destruction.

[0004] Common circuit carriers are, for example, copper punched grids or organically or ceramically insulating printed circuit boards or component carriers with a rail structure. The components are electrically connected to the rails of the circuit carrier via extruded or materially connected contact elements (e.g. bonding wires or thin ribbons). The circuit carrier is either designed to be thermally expandable itself (e.g. by a thick metal layer on the bottom, which is electrically insulated from the conductive conductor on the top by an insulating coating), or the circuit carrier is formed of ceramic, has typically thin rails arranged on the top and is mounted on a separate metallic thermal expansion plate.

[0005] In the context of this description, thermal expansion always takes place on the underside of the circuit carrier, that is, the circuit carrier can have an additionally mounted thermal expansion plate or also act thermally by itself. The underside of the circuit carrier is in thermal contact with the main heat sink in a force-fitting and form-fitting manner. In contrast, on the upper side of the circuit carrier, heat is generated in the component due to ohmic losses.

[0006] The components are usually embedded (or also: cast) in an electrically insulating material such as silicone or an electrically insulating epoxy resin, wherein the insulating material often has a thermal insulation property that is also high. Only the external connection contacts of the power electronics module remain exposed.

[0007] The heat is transported from the component to the cooling body on two time scales: pulse power (<1 second) and continuous power (>>1 second). Pulse power is very short in order to reach the heat sink directly and must be temporarily absorbed in the thermal mass of the insulating material near the component. Continuous power, on the other hand, causes a continuous heat flow of power loss along the thermal gradient through all heat-conducting materials to the heat sink.

[0008] In order to improve cooling, heat-conducting and electrically insulating casting compounds have been proposed as insulating materials, for example, an inorganic bonding agent is proposed in DE 1 514 413 A1. Patent document EP 3 066 684 B1 also uses a heat-conducting bonding agent to arrange a second cooling body in thermal contact on its surface above the component on the mounting side of the thermal expansion plate (see in particular Figures 3 and 4 of EP 3 066 684 B1).

[0009] Thermally conductive bonding agents are well suited to receiving pulsed power. However, their thermal conductivity is in the range of 1 to 20 W / (m*K) and is therefore one to two orders of magnitude lower than the thermal conductivity of conventional cooling bodies. In continuous operation, despite cooling on both sides of the assembly, the heating of the power module of EP 3 066 684 B1 still occurs very asymmetrically, since most of the generated heat can first be released to the cooling body on the lower side of the thermal expansion plate. Therefore, the operation of the second cooling body on the surface of the casting material is largely inefficient. Summary of the invention

[0010] It is therefore an object of the present invention to provide a power electronics module which is as compact as possible and has improved cooling.

[0011] This object is achieved by a power electronics module having the features of claim 1. Advantageous embodiments are described in the dependent claims.

[0012] It can be seen that the basic idea of ​​the invention is to take a power electronic module that can be produced currently (first without a casting compound) and arrange a plurality of power electronic modules with the flat sides of the components (i.e. the heat source) pointing to each other (especially fixedly) in such a way that these power electronic modules form a space between the components. This space is thus heated up particularly strongly and from multiple sides due to the ohmic power loss of the components. Therefore, according to the invention, an additional central heat sink is arranged in this space for cooling, such as a metallic heat sink or a pipe through which a cooling liquid flows. Here, the central heat sink can also include a plurality of heat sinks, especially a combination of different heat sinks (for example, composed of solids and pipes through which a fluid flows). These heat sinks can be connected to each other, so that the central heat sink is designed as an object, such as a grid or a tube array. The central heat sink is fixed and permanently held in the space between the components in such a way that the space is filled with a heat-conducting casting compound, especially an inorganic bonding agent, which embeds the components and the central heat sink together in a separate casting volume.

[0013] The power electronics module according to the invention is cooled on its outside in principle by means of cooling bodies which, in conventional production processes, are in thermal contact with the underside of the circuit carrier. In addition, there is a cooling device arranged in the module which is realized by a central heat sink which is electrically insulated from the components at least by the potting compound and in particular is kept at a fixed distance.

[0014] Therefore, according to the present invention, a power electronic module is proposed, comprising a first circuit carrier and an electronic component arranged on a flat side of an upper part of the first circuit carrier in electrical contact, and a first cooling body in thermal contact with a lower side of the first circuit carrier (i.e., thermally connected to the lower side of the first circuit carrier), wherein the module comprises at least a second component arranged on an upper side of a second circuit carrier and a second cooling body arranged on a lower side of the second circuit carrier, wherein the first circuit carrier and the second circuit carrier are arranged with their upper sides facing each other and at least one central heat sink electrically insulated from the components is arranged in a space between the components, wherein the components and the at least one central heat sink are embedded in a heat-conducting casting compound, wherein the module comprises a number N ≥ 3 circuit carriers together with the components mounted on the upper sides of the circuit carriers and the cooling bodies mounted on the lower sides of the circuit carriers, and the components are arranged with their sides pointing to each other to form a shape having an N-cornered polygon as a cross-section around the central heat sink.

[0015] Therefore, based on the design according to the invention, a multi-dimensional spatial arrangement is possible, wherein the polygonal cross section can be partially closed by a cover at its upper and lower sides. Of course, it should be noted that the inlet and outlet to the centrally arranged radiator are retained.

[0016] Preferably, the central heat sink has a shape with an N-sided polygon as cross section, wherein the N-sided polygon of the heat sink and the N-sided polygon formed by the circuit carrier particularly preferably have the same shape.

[0017] The first circuit carrier and / or the second circuit carrier are preferably of planar design.

[0018] According to another preferred design, the first heat sink is in thermal contact (thermal conductive connection) with the bottom side of the first circuit carrier in a force-fitting and / or form-fitting manner, wherein, particularly preferably, the second heat sink can also be in thermal contact with the bottom side of the second circuit carrier in a force-fitting and / or form-fitting manner.

[0019] The first circuit carrier and the second circuit carrier are arranged in particular to be fixed with their top sides facing each other.

[0020] According to a particularly preferred embodiment, the circuit carriers are designed to be of the same size.

[0021] Finally, the circuit carrier is arranged to be fixed around the central heat sink. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The module according to the invention can thus be distinguished significantly from the flat, almost two-dimensional design of the power modules customary hitherto, as shown in the following figures:

[0023] Figure 1 Shown are (a) two parallel symmetrical power single switches with an internal active liquid cooling device as a central heat sink, and (b) two parallel symmetrical power single switches with a passive internal cooling device formed by a flat heat conducting plate as a central heat sink;

[0024] Figure 2 Shown are (a) three power switches (here a half-bridge) with triangular symmetry and a (circular) internal heat pipe as a central heat sink, and (b) three power switches (here a half-bridge) with triangular symmetry and a (triangular) internal heat pipe as a central heat sink. DETAILED DESCRIPTION

[0025] The invention is explained in more detail with reference to a particularly preferably designed exemplary embodiment illustrated in the drawings.

[0026] exist Figure 1 One of the simplest designs of a power electronic module of preferred design is shown in a. This design consists of two conventional power modules, the sides of which support the components are arranged to be fixed facing each other. A ceramic substrate 10 with a guide rail element mounted on a heat expansion plate 5 is used as a circuit carrier 5, 10 and is contacted with a semiconductor component 20 mounted thereon by bonding wires 30 to form a single switch 5, 10, 20, 30. The lower side of the circuit carrier 5, 10 (mounted in a thermal contact manner) has a cooling body 40. The same second arrangement is arranged in parallel, but optionally rotated 180 degrees to be arranged opposite to the first arrangement. The required distance between the two components 20, 30 is derived from the electrical insulation distance required to maintain electrical safety. The space between the components 20, 30 is filled with an electrically insulating, preferably inorganic, casting material 50 with high thermal conductivity. In this way, it is ensured that all heat-releasing surfaces of the components 20, 30 are in material contact with the casting material 50. An additional cooling device structure 60 (eg a pipe through which a liquid flows or a closed heat pipe) forms a central heat sink within the potting compound 50 . After the potting compound 50 has hardened, the heat sink 60 remains permanently in place and thus also always remains potential-free.

[0027] Figure 1 b shows Figure 1A variant of a, in which the cooling body 40 extends until it exceeds the edge of the heat expansion plate 5 and is designed to be raised on the other side of the edge until it exceeds the maximum height of the components 20, 30. In other words, in this embodiment, the cooling body 40 has a groove-like shape, and the components 20, 30 are respectively arranged at the bottom of such a groove. If the groove-shaped cooling bodies 40 are stacked on each other with their raised edges in thermal contact, an inner space with components 20, 30 is surrounded by the heat sink 40 on four sides. In addition, Figure 1 b) shows a very good thermally conductive structure in the form of a metallic or ceramic heat-conducting bridge 61 (for example a plate made of copper or aluminum or silicon nitride ceramic or aluminum nitride ceramic). Figure 1 The heat pipe of a, the heat conducting bridge 61, here forms the central heat sink 60 of the compact power electronic module. The heat conducting bridge 61 is installed between the two outer cooling bodies 40 and is in thermal contact with them at the edge of the cooling body 40. The heat conducting bridge can be formed from the same material as the cooling body 40, in particular from metal. The remaining interior space surrounded by the trough-shaped cooling body 40 and not otherwise occupied is preferably completely filled with the heat conducting casting compound 50.

[0028] Preferably, the thermal conductivity of the casting material is greater than 3 W / (m*K). Known thermally conductive bonding agents achieve values ​​greater than 10 W / (m*K). Furthermore, preferably, the thermal conductivity of the material of the heat-conducting bridge 61 is at least 20 times greater than that of the casting material.

[0029] exist Figure 2 A compact power electronic module with a triangular cross section is shown in a. Here, the circuit carrier 11, which is insulated and designed for thermal expansion, is in contact with the rail element and the semiconductor 20 mounted thereon by means of bonding wires 30 to form half bridges 11, 20, 30. The lower side of the circuit carrier 11 (mounted in thermal contact) has a cooling body 40. The same second module and the third module are assembled together with the first module in an isosceles triangle arrangement. In this way, the distance between the three half bridges 11, 20, 30 is minimal. The space between the three components 20, 30 is filled with an electrically insulating, preferably inorganic, casting material 50 with high thermal conductivity. In this way, it is ensured that all heat-releasing surfaces of the components 20, 30 are in material contact with the filler. An additional cooler structure 63 (e.g., a heat-conducting rod or a pipe through which a liquid flows or a closed heat pipe) forms a central heat sink inside the casting material 50.

[0030] Figure 2 a and Figure 2The comparison of b shows the possibility of further optimization: the heat sink structure 63 with a circular cross section can be easily replaced by a heat sink structure 64 with a triangular cross section. This has the following direct advantage: the large part of the heat path from the components 20, 30, through the relatively poorly thermally conductive casting material 50, to the central heat sink 64 is shortened. At the same time, this variation of the cross section of the central heat sink 64 has no negative effect on the outer dimensions of the compact power electronic module according to the invention.

[0031] according to Figure 2 For example, a B6 bridge circuit for a 3-phase motor control can be formed in this way. These three half-bridge components, which are thus identical in structure, occupy the smallest volume in the illustrated isosceles triangle configuration facing each other, and the power electronics module is thus maximally compact according to the teaching of the invention.

[0032] It is not difficult for a person skilled in the art to realize that in a similar manner, it is also possible to construct other (typically symmetrical) compact arrangements consisting of conventional power modules based on additional central heat sinks 60, 61, 63, 64 with a cooling surface enlarged according to the invention, preferably such arrangements having a square or an N-cornered polygon (where N>4) as a cross-section.

Claims

1. A power electronic module comprising a first circuit carrier (5, 10, 11) and an electronic component (20, 30) arranged in electrical contact on the upper flat side of the first circuit carrier (5, 10, 11) and a first heat sink in thermal contact with the lower side of the first circuit carrier (5, 10, 11), wherein: The module comprises at least a second component (20, 30) arranged on the upper side of a second circuit carrier (5, 10, 11) and a second heat sink arranged on the lower side of the second circuit carrier (5, 10, 11), wherein the first circuit carrier and the second circuit carrier (5, 10, 11) are arranged with their upper sides facing each other and at least one central heat sink (60, 61, 63, 64) electrically insulated from the components (20, 30) is arranged in the space between the components (20, 30), wherein the components (20, 30) and the at least one central heat sink (60, 61, 63, 64) are embedded in a heat-conducting casting compound (50), wherein the module comprises a number N ≥ Three circuit carriers (5, 10, 11) together with components (20, 30) mounted on the upper sides of the circuit carriers and a cooling body mounted on the lower sides of the circuit carriers are arranged with the sides of the components (20, 30) pointing to each other to form a shape having an N-angle polygon as a cross section around the central heat sink (60, 61, 63, 64).

2. The power electronic module according to claim 1, characterized in that The central heat sink (60, 61, 63, 64) has a shape with an N-angle polygon as its cross section.

3. The power electronic module according to claim 2, characterized in that: The N-sided polygon of the heat sink (60, 61, 63, 64) and the N-sided polygon formed by the circuit carriers (5, 10, 11) have the same shape.

4. A power electronic module according to any one of the preceding claims, characterized in that The first circuit carrier (5, 10, 11) is planar.

5. The power electronic module according to claim 4, characterized in that: The second circuit carrier (5, 10, 11) is planar.

6. The power electronic module according to claim 1, characterized in that: The first cooling body is in thermal contact with the underside of the first circuit carrier (5, 10, 11) in a force-fitting and form-fitting manner.

7. The power electronic module according to claim 6, characterized in that: The second cooling body is in thermal contact with the underside of the second circuit carrier (5, 10, 11) in a force-fitting and form-fitting manner.

8. The power electronic module according to claim 1, characterized in that: The first circuit carrier and the second circuit carrier (5, 10, 11) are arranged to be fixed with their upper sides facing each other.

9. The power electronic module according to claim 1, characterized in that: The circuit carriers are designed to be of the same size.

10. The power electronic module according to claim 1, characterized in that: The circuit carriers (5, 10, 11) are arranged to be fixed around the central heat sink (60, 61, 63, 64).

Images