Electronic module with at least one power semiconductor and method for manufacturing same

Abstract

The invention relates to an electronic module (100) comprising at least one power semiconductor (10) electrically connected to a contact connection array (20) and at least one cooling element (32, 34, 36) for at least indirect cooling of the at least one power semiconductor (10).

Description

[Technical Field]

[0001] The present invention relates to an electronic module comprising at least one power semiconductor which is simultaneously cooled by means of a cooling element and which can be electrically contacted.Furthermore, the present invention relates to a method for manufacturing an electronic module. [Background technology]

[0002] German Patent Application No. DE 10 2014 221 147 A1, filed by the applicant, discloses an electronic module with at least one power semiconductor having the features set forth in the preamble of claim 1. The known electronic module has cooling bodies arranged on opposite sides in operative connection with the power semiconductor via a multi-layer stack structure, which allow the cooling bodies to dissipate heat from the power semiconductor. Cooling elements, which are formed as prefabricated components and are used exclusively for cooling the power semiconductor, are thermally connected to the power semiconductor via a bonding layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Patent Application Publication No. 102014221147 Summary of the Invention [Means for solving the problem]

[0004] Disclosure of the Invention The electronic module according to the invention, which comprises at least one power semiconductor having the features of claim 1, allows for a particularly convenient integration of cooling elements into the multilayer stack of the module, with the advantage that the cooling elements simultaneously serve for electrical contacting of the power semiconductor with the contact array, via which the power semiconductor is connected to the control or circuit. Furthermore, the electronic module makes it possible to provide a cooling element optimized for the respective application in a particularly simple manner.

[0005] The idea behind the present invention is to form the cooling element by a productive or additive manufacturing method, in particular so that it is arranged as an intervening element for the electrical contact connection between the power semiconductor and the contact connection array.

[0006] Therefore, against the background of the above explanation, it is proposed to form an electronic module according to the invention with at least one power semiconductor as claimed in claim 1, in which at least one cooling element is formed as a cooling element manufactured by an additive manufacturing method, the at least one cooling element being arranged between the at least one power semiconductor and the contact-connection array and electrically connecting the at least one power semiconductor to the contact-connection array.

[0007] Preferred developments of the electronic module according to the invention with at least one power semiconductor are set forth in the dependent claims.

[0008] In a particularly preferred development of the module according to the invention, it is provided that at least one cooling element is constructed from a plurality of layers, which layers form channels for guiding a cooling medium. This type of construction therefore makes it possible, in particular, to provide a closed cross section for guiding the cooling medium or to form corresponding channels. Here, the cooling medium is in particular a gas, but alternatively also a cooling liquid.

[0009] In a further embodiment, which is particularly suitable for reducing thermomechanical stresses or module loads in the region of the power semiconductor, it is envisaged that at least one cooling element has a lower stiffness in a direction extending perpendicular to the surface of the power semiconductor than in a direction extending parallel to the surface of the power semiconductor. In other words, this means that the cooling element has a certain degree of flexibility in the direction extending perpendicular to the surface of the power semiconductor in order to compensate for the aforementioned stresses perpendicular to the surface of the power semiconductor. Ideally, therefore, the cooling element forms a kind of spring element. However, the cooling element also has a certain degree of elasticity or spring action in the other direction extending parallel to the plane of the power semiconductor in order to compensate for the mechanical stresses in this direction. Finally, the geometry of the cooling element or its stiffness can be optimized for the respective application, or the stiffness can be optimized depending on the direction.

[0010] In a particularly preferred structural embodiment of the cooling element, it is envisaged that at least one cooling element has first and third layers formed over the entire surface on opposite sides, which first and third layers are electrically connected to the power semiconductor or the contact connection array, and the first and third layers formed over the entire surface are directly followed by a second layer, which forms at least one channel for guiding the cooling medium.

[0011] Furthermore, it is particularly preferred that at least one cooling element is arranged on each of two opposite faces of at least one power semiconductor in order to optimize cooling or to enable the power semiconductors to be electrically contacted from different faces.

[0012] To improve the bond between the cooling element and the power semiconductor or to ensure the connection, at least one power semiconductor is connected to the at least one cooling element by means of a contacting layer, the material of which is the same in type as the material of the cooling body. The same material type of the cooling body and the contacting layer (which may, for example, both consist of or contain aluminum or copper, respectively) makes it possible to achieve a material bond between the contacting layer and the material of the cooling body, in particular when the material of the cooling body is additively built or melted and subsequently solidified (when the additive building takes place via multiple layers of metal powder that are melted using a laser beam).

[0013] In a further preferred embodiment of the module for optimizing the cooling effect, it is envisaged that the at least one cooling element and the at least one power semiconductor are arranged inside a housing containing a cooling medium, and the contact connection array is arranged outside the housing and is connected to the at least one cooling element via a connection element through a preferably sealed opening formed in the housing.

[0014] In a preferred development of this proposal, it is envisaged that the connection element is formed as a monolithic component of the cooling element, so that the connection element, which is part of the cooling element or is produced together with the cooling element by an additive method, bridges the area between the cooling element used for the actual cooling and the contact-connection array.

[0015] The present invention further preferably relates to a method for manufacturing an electronic module configured in accordance with the above description, wherein the method according to the invention comprises at least the following steps: first, a step of providing a power semiconductor with at least one contacting layer is performed, followed by a step of forming at least one cooling element on a surface of the at least one contacting layer by an additive manufacturing method, and finally, a step of at least indirectly connecting the at least one cooling element to the contacting array on a side facing away from the power semiconductor.

[0016] In a preferred development of the method, it is envisaged that before at least one cooling element is at least indirectly connected to the contact-connection array, at least one power semiconductor is arranged, the at least one cooling element is arranged inside the housing and the contact-connection array is arranged outside the housing.

[0017] With regard to the formation of the cooling element, it is preferable to use a laser beam to selectively melt and subsequently solidify a powder layer to form at least one cooling element, thereby reducing the welding depth and / or energy input of the laser beam during the formation of the lower or first layer of the cooling element facing the power semiconductor. This, in particular, avoids thermal overload or damage to the power semiconductor. Here, a reduction in the welding depth is possible to some extent by adjusting the process parameters (e.g., laser power, laser travel speed, etc.). Alternatively or additionally, it is also conceivable to use so-called ultrashort pulse lasers to melt the cooling body material. This pulsed laser beam allows, on the one hand, a high absorption intensity (necessary for melting the starting material of the cooling body) and, at the same time, a relatively low absorbed average power (necessary for the desired low heat input into the power semiconductor). Many very weak pulses (in the range between 1 MHz and 100 MHz) allow very precise, particularly very small, welding depths to be achieved. To make this process possible, the powder size distribution must also be adjusted to smaller sizes (between 0.1 μm and 5 μm). This allows for a comparable layer thickness, so that a relatively low build speed is achievable. As soon as a certain structural height of the cooling body (for example, between 10 μm and 100 μm) is reached, the process can be switched back to conventional methods.

[0018] A possible further adjustment of the manufacturing process would be the use of the so-called LTM method (LTM = Laser Transfer Metallization), which is a further development of the LIFT (LIFT = Laser-Induced-Forward-Transfer) method. In the LTM method, a sacrificial layer of the material from which the cooling element is to be constructed is melted above the substrate or the power semiconductor. This melted material sinks onto the power semiconductor and forms a base layer for the structure of the cooling element to be constructed, on which the cooling element can then be constructed by conventional powder bed methods.

[0019] Alternatively, it may be envisaged to reduce the thermal load of the power semiconductor during the additive construction of the cooling element by increasing the thickness or height of the contacting layer of the power semiconductor on which the cooling element is constructed compared to the prior art. Compared to the prior art, an increase in the metallization by a few micrometers already results in a significant widening of the process window for additive processes. In some cases, this may even be so great that the aforementioned measures for reducing the energy input can be omitted. It is also conceivable to reduce the thermal load during the layer construction of the cooling element by adjusting the material of the metallization. In principle, adjustments of the substrate or the power semiconductor are also conceivable for the entire layer system of the metallization.

[0020] Preferably, the powder is a metal powder. This metal powder consists of or contains copper and / or aluminum and / or copper alloys and / or aluminum alloys. Alternatively or additionally, the metal powder comprises a carbon-containing composite. Particularly preferably, additive construction allows the above materials to be mixed into the powder mixture in order to produce different alloys by a melting process.

[0021] Further advantages, features and details of the present invention will become apparent on the basis of the following description and drawings of preferred embodiments of the invention. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a simplified longitudinal section of an electronic module with power semiconductors manufactured by an additive manufacturing method and using two cooling elements connected to a contact connection array; DETAILED DESCRIPTION OF THE INVENTION

[0023] Embodiments of the invention The electronic module 100 shown in Fig. 1 comprises a power semiconductor 10 which generates heat during operation and which is configured in a particularly conventional manner as a substrate. Two opposing surfaces of the power semiconductor 10 are provided with contact layers 12, 14 and 16 in the form of contact pads made of metal, for example made of copper or aluminum in a conventional manner by printing. These contact layers 12, 14 and 16 serve to electrically connect the power semiconductor 10 to a contact array 20 which comprises elements such as conductor tracks, punched grids, etc., and which comprises one connecting element 22, 24 and 26 for each contacting area 12, 14 and 16, respectively.

[0024] The connections between the contact regions 12, 14, 16 and the connection elements 22, 24, 26 of the contact array 20 are made via three exemplary cooling elements 32, 34, 36, each of which is manufactured by an additive manufacturing process.

[0025] By way of example, the cooling elements 32, 34, 36 each have at least one, typically several, first layers 41, which are arranged over and connected to the contact-connection layers 12, 14, 16. These are followed by a number of second layers 42, which are correspondingly shown in FIG. 1 and which form cavities 44 as components of channels 45 in the form of a herringbone pattern, purely by way of example. Furthermore, the second layers 42 are here essentially arranged or shaped as follows: by way of example, in a direction extending perpendicular to the plane of the surface of the power semiconductor 10, the cooling elements 32, 34, 36 are arranged or shaped in such a way that, according to the double arrow 46, they have a higher elasticity or a lower stiffness in a direction extending perpendicular to the plane of the surface of the power semiconductor 10 than in a direction extending parallel to the surface of the power semiconductor 10. However, the cooling elements 32, 34, 36 have a lower stiffness than cooling elements 32, 34, 36 made of solid material (i.e. material without cavities 44), also in a direction extending parallel to the plane of the surface of the power semiconductor 10. The second layer 42 therefore has a dual function: on the one hand, it makes it possible to adjust the directionally dependent stiffness or elasticity of the cooling elements 32, 34, 36 to the respective application case, and on the other hand, it is a cooling component around which the cooling medium can flow and which, as a result of the enlarged surface due to the cavities 44, allows for particularly good heat transfer.

[0026] The second layer 42 is followed by a plurality of third layers 43, which are formed as full-surface (i.e., gap-free) layers, for example, overlapping the first layer 41 or having the surface of the first layer 41.

[0027] The cooling elements 32, 34, 36 described so far are arranged together with the power semiconductor 10 inside a housing 50. The housing 50, which is preferably closed, is filled with the medium used for cooling, which may be provided as a liquid or gaseous medium. The flow or circulation of the medium is preferably effected according to the flow arrows 52, in particular such that the cooling elements 32, 34, 36 are circulated by the medium in the cross-sectional area of the channel 45.

[0028] The housing 50 has one through opening 54 pierced by a connecting element 56 assigned to each cooling element 32, 34, 36. The connecting elements 56 are monolithic components of the cooling elements 32, 34, and 36, i.e. the cooling elements 32, 34, 36 together with the respective connecting elements 56 are produced in a single manufacturing process.

[0029] On the outside of the housing 50, the connection element 56 is connected to the connection elements 22, 24, 26 via a further contact-connection layer 58, which is made in particular from the same material as the cooling elements 32, 34, 36.

[0030] The module 100 described above can be changed or modified in a variety of ways without departing from the scope of the present invention, so that, for example, the housing 50 can be omitted and cooling of the power semiconductors 10 can be achieved by air circulation.

Claims

1. An electronic module (100) comprising at least one power semiconductor (10) electrically connected to a contact-connection array (20) and at least one cooling element (32, 34, 36) for at least indirect cooling of said at least one power semiconductor (10), the at least one cooling element (32, 34, 36) is disposed between the at least one power semiconductor (10) and the contact connection array (20) and electrically connects the at least one power semiconductor (10) to the contact connection array (20); the at least one cooling element (32, 34, 36) has first and third layers (41, 43) formed on opposite sides thereof, respectively, over the entire surface thereof, the first and third layers (41, 43) being electrically connected to the power semiconductor (10) or the contact-connection array (20), the first and third layers (41, 43) being directly followed by a second layer (42), and the first, second and third layers (41, 42, 43) forming at least one channel (45) for guiding a cooling medium; An electronic module (100).

2. 2. The electronic module (100) of claim 1, wherein the at least one cooling element (32, 34, 36) has a lower stiffness in a direction extending perpendicular to a surface of the power semiconductor (10) than in a direction extending parallel to the surface of the power semiconductor (10).

3. 2. The electronic module (100) according to claim 1, wherein at least one cooling element (32, 34, 36) is arranged on each of two opposing faces of the at least one power semiconductor (10).

4. 2. The electronic module (100) of claim 1, wherein the at least one power semiconductor (10) is connected to the at least one cooling element (32, 34, 36) by means of a contact-connection layer (12, 14, 16), the material of which is the same type as the material of the at least one cooling element (32, 34, 36).

5. 2. The electronic module (100) of claim 1, wherein the at least one cooling element (32, 34, 36) and the at least one power semiconductor (10) are arranged inside a housing (50) containing a cooling medium, and / or the contact-connection array (20) is arranged outside the housing (50) and is connected to the at least one cooling element (32, 34, 36) via a connecting element (56) formed in the housing (50) and preferably via a sealed opening (54).

6. The electronic module (100) of claim 5, wherein the connection element (56) is formed as a monolithic component of the cooling element (32, 34, 36).

7. A method for manufacturing an electronic module (100), comprising: At least the following steps: Providing a power semiconductor (10) having at least one contacting layer (12, 14, 16); forming at least one cooling element (32, 34, 36) on the surface of said at least one contact-connection layer (12, 14, 16) by an additive manufacturing method; at least indirectly connecting said at least one cooling element (32, 34, 36) to a contact-connection array (20) on a side opposite said power semiconductor (10); Including, The additive formation of the at least one cooling element (32, 34, 36) is performed by selective melting and subsequent solidification of a powder layer using a laser beam, reducing the welding depth and / or energy input of the laser beam when forming layers below the at least one cooling element (32, 34, 36).

8. 8. The method of claim 7, further comprising the steps of: arranging the at least one power semiconductor (10), arranging the at least one cooling element (32, 34, 36) inside a housing (50), and arranging the contact connection array (20) outside the housing (50) before at least indirectly connecting the at least one cooling element (32, 34, 36) to the contact connection array (20).

9. The method of claim 7, wherein the electronic module (100) is the electronic module (100) of claim 1.

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