Printed circuit board assembly and method for producing a printed circuit board assembly

Description

[0001] The invention relates to a printed circuit board arrangement according to the preamble of patent claim 1 and a method for producing such a printed circuit board arrangement.

[0002] It is known to press printed circuit board-based power electronics assemblies onto a heat sink using screw connections for cooling. The components to be cooled are typically designed as surface-mounted devices (SMD) or through-hole technology (THT) and are located on the underside of the printed circuit board. The components to be cooled comprise an embedded semiconductor component and are also referred to as prepackage modules or—in the terminology used here—as electrical modules.

[0003] Depending on the performance class, a large number of prepackage modules to be cooled are arranged on the underside of the circuit board and pressed against a heat sink for cooling. It is important to note that any gap between the electrical module to be cooled and the heat sink will impair the thermal connection between the electrical module and the heat sink. Therefore, any gap between a module to be cooled and the heat sink should be minimized. If multiple electrical modules need to be cooled, gaps with different gap sizes to the heat sink may exist, which must be compensated for. Further tolerances in the gap sizes arise from the thickness tolerance of the circuit board, local thermal deflection of the circuit board, and unevenness in the heat sink surface.

[0004] To compensate for these height tolerances, thermally conductive materials are commonly used. In power electronics, paste systems or films are used. These are applied to the cooling surface and compensate for minimal gaps and roughnesses of up to 100 µm. However, effective heat transfer into the heat sink only occurs in the area of ​​the electrical modules, as these are pressed against the heat sink, and the thermal resistance decreases with increased mechanical pressure.

[0005] JP 2015 211600 A describes a power conversion device comprising a semiconductor module, a cooler for cooling the semiconductor module, a control substrate connected to the semiconductor module, a terminal for connecting the semiconductor module and the control substrate, and a bus bar for connecting the semiconductor module to an input terminal and an output terminal, wherein at least one of a C-plane, an S-plane, and a lateral surface is made to contact a reinforcing member and to be fixed to the reinforcing member.

[0006] US 2020 / 203301 A1 describes a package structure comprising at least one semiconductor chip, a plurality of hollow cylinders, an insulating encapsulant, a redistribution layer, and vias. The plurality of hollow cylinders surround the at least one semiconductor chip. The insulating encapsulant has an upper surface and a lower surface opposite the upper surface, wherein the insulating encapsulant encapsulates the at least one semiconductor chip and the plurality of hollow cylinders. The redistribution layer is arranged on the upper surface of the insulating encapsulant and above the at least one semiconductor chip. The vias penetrate the plurality of hollow cylinders.

[0007] The present invention is based on the object of providing a printed circuit board arrangement which provides an improved thermal connection of an electrical module to a heat sink, and of specifying a method for producing such a printed circuit board arrangement.

[0008] This object is achieved by a printed circuit board assembly having the features of claim 1 and a method having the features of claim 12. Embodiments of the invention are specified in the dependent claims.

[0009] According to this, in a first aspect of the invention, a printed circuit board assembly comprising a printed circuit board having a top side and a bottom side, at least one electrical module arranged on the bottom side of the printed circuit board, a heat sink, means for providing a pressure with which the electrical module is pressed with its bottom side against the heat sink, and a thermally conductive material, wherein the thermally conductive material is arranged between the bottom side of the electrical module and the heat sink.

[0010] It is provided that the at least one electrical module is embedded in a potting material which is flush with the underside of the electrical module without covering the underside, wherein the potting material is provided and designed to press the thermally conductive material against the heat sink adjacent to the at least one electrical module.

[0011] The solution according to the invention is based on the idea of ​​improving the thermal coupling of an electrical module to a heat sink by means of a potting material in which the electrical module is cast, which additionally presses the heat-conducting foil on the side of the electrical module against the heat sink, so that the thermal transition to the heat sink takes place on an enlarged heat sink surface.

[0012] The inventive solution is based on the knowledge that the thermal transfer to the heat sink depends heavily on the contact pressure on the heat sink. In conventional printed circuit board arrangements, the contact pressure is only high in the area of ​​the electrical modules to be cooled, which are pressed against the heat sink. Next to the electrical modules, however, the thermally conductive material simply rests on the heat sink surface without any contact pressure, so that heat transfer into the heat sink is low in these areas. By embedding the electrical module or a plurality of electrical modules in a potting material, the thermally conductive material can also be pressed against the heat sink surface next to the electrical module and between the individual electrical modules. In this way, the thermal transfer to the heat sink is improved overall.

[0013] The inventive solution thus achieves improved heat distribution across the surface of the heat sink and thus improved cooling of the electrical modules. This, in turn, allows for the use of smaller cooling systems.

[0014] It should be noted that, for the purposes of the present invention, the side of the circuit board on which an electrical module to be cooled is arranged is always referred to as the underside of the circuit board, regardless of the actual orientation of the circuit board and the electrical module in space.

[0015] If the printed circuit board arrangement has several electrical modules, it can be provided that these are embedded together in a potting material, whereby the potting material presses the thermally conductive material against the heat sink in the area between the electrical modules.

[0016] In embodiments of the invention, the encapsulating material extends at least partially to the underside of the circuit board, so that the open space between the thermally conductive material and the underside of the circuit board is completely or at least partially filled with the encapsulating material. This achieves improved cooling of all components of the circuit board through a full-surface connection of the circuit board to the heat sink.

[0017] Furthermore, this design allows for partial electrical insulation of critical areas on the underside of the circuit board or in the area between the electrical module and the circuit board. In this context, it should be noted that the arrangement of the electrical modules on the circuit board or on a carrier board is achieved using a soldering process in which associated solder pads on the electrical module and on the circuit board are connected to one another using a layer of solder. This inherently creates an air gap between the electrical module and the circuit board. This air gap is conventionally filled with an insulating material in an underfill process. This material, among other things, protects against partial discharges and enables compliance with clearance and creepage distances. However, the application of an underfill material is challenging from a manufacturing perspective.The material is applied next to the electrical module and then penetrates into the gap due to capillary action. The quality of the underfill layer, with regard to the required absence of bubbles, depends on numerous factors, such as the cleanliness of the gap, the gap height, the gap geometry, and the surfaces used.

[0018] The solution according to the invention makes it possible to avoid an underfill process and instead fill the gap between the top side of the electrical module and the underside of the circuit board with the encapsulating material. One embodiment of the invention provides that the electrical module has electrical solder pads formed on its top side, each of which is in contact with an associated electrical solder pad on the circuit board via a solder layer. The encapsulating material extends adjacent to the solder pads and also into the gap between the underside of the circuit board and the top side of the electrical module. An underfill material is thus replaced by the encapsulating material.This reduces the risk of bubble formation in the gap between the electrical module and the circuit board, since the potting material in embodiments of the invention is significantly more gap-permeable and can also be injected at high pressure, for example by injection molding, as will be explained below.

[0019] A further embodiment provides that the encapsulation material further surrounds and electrically insulates those areas on the underside of the circuit board in which the circuit board forms vias. For background information, it should be noted that the electrical contacts on the circuit board are typically supplied with voltage via vias in the circuit board. Contact surfaces of the circuit board provided with such vias must be electrically insulated. When using an underfill material, it cannot be applied precisely to the circuit board and thus to the surfaces to be insulated due to its cross-linking properties. This requires further process steps with an additional material, for example, using a so-called "dam & fill" process, to insulate the vias. The additional material forms a boundary layer to the underfill material.

[0020] The solution according to the invention avoids these problems by using the encapsulating material to additionally insulate those areas on the underside of the circuit board where the circuit board forms vias. The encapsulating material is thus used for partial insulation of critical areas on the circuit board.

[0021] One embodiment of the invention provides that the potting material has a hardness that is greater than the hardness of the thermally conductive material, so that it can effectively press the thermally conductive material against the heat sink. The potting material can be designed as a hard potting material.

[0022] In some examples, the potting material is a thermosetting plastic. For example, the potting material is an epoxy resin. A two-component epoxy consists of a polymer resin and a hardener that react chemically with each other. An epoxy potting compound is characterized by high rigidity and tensile strength, high temperature resistance, and low shrinkage. It also has a high dielectric strength.

[0023] A further embodiment of the invention provides for the at least one electrical module to be embedded in the encapsulating material by transfer molding or injection molding. These processes allow the electrical module to be overmolded under pressure in a defined manner, whereby the volume to be overmolded can be precisely defined. Certain areas of the printed circuit board assembly can also be filled with encapsulating material and partially insulated, such as the gap between the electrical module and the printed circuit board, as well as via areas on the printed circuit board.

[0024] In embodiments, the electrical module is constructed in such a way that it comprises: a ceramic circuit carrier having an insulating ceramic layer and a metallization layer arranged on top of the ceramic layer, and an electrical component arranged on top of the metallization layer and electrically connected thereto, wherein the ceramic layer or a second metallization layer formed on the underside of the ceramic layer is connected to the heat sink via the thermally conductive material.

[0025] Such ceramic circuit carriers serve to electrically insulate the electrical component connected to the ceramic circuit carrier from the heat sink and at the same time to thermally connect it to the heat sink.

[0026] The electrical component integrated into the electrical module can be a semiconductor component, in particular a power semiconductor such as a power MOSFET or an IGBT component. For example, it is a power semiconductor of an inverter or, more generally, a power converter intended for operating an electric motor.

[0027] Furthermore, it can be provided that electrical contacts of the module comprise at least a first via extending from a solder pad on the top side to the first metallization layer, as well as second and third vias extending from other solder pads on the top side to corresponding contacts on the top side of the electrical component. This enables contacting of the electrical component via contacts arranged on the top side of the electrical module.

[0028] A further embodiment provides that the at least one electrical module is arranged in a cavity of the heat sink.

[0029] In a further aspect, the present invention also relates to a method for producing a printed circuit board assembly. The method comprises the steps: Arranging and electrically contacting at least one electrical module on the underside of a printed circuit board, inserting the printed circuit board with the at least one electrical module into a tool, applying a stamp with a compensating film to the underside of the at least one electrical module and pressing the compensating film against the underside, closing the tool, injecting a molding compound into the tool, wherein the at least one electrical module is overmolded without the underside of the electrical module covered with the compensating film being covered with the molding compound, curing the molding compound to form a potting compound, removing the printed circuit board with the at least one electrical module encapsulated with the potting compound from the tool, and thermally coupling the at least one electrical module to a heat sink using a thermally conductive material and means for providing pressure,wherein the potting material adjacent to the at least one electrical module presses the thermally conductive material against the heat sink.

[0030] This aspect of the invention provides a robust and defined method for insulating and overmolding electrical modules and other printed circuit board areas.

[0031] The injection of a molding compound into the tool is carried out, for example, by transfer molding or injection molding.

[0032] One embodiment provides that when the molding compound is injected into the tool, the at least one electrical module is overmolded in such a way that the molding compound also closes a gap between the underside of the circuit board and the top side of the electrical module (except for those areas in which, as explained, electrical solder pads and solder layers are formed).

[0033] Furthermore, it can be provided that when the molding compound is injected into the tool, the at least one electrical module is overmolded in such a way that the molding compound also surrounds and electrically insulates those areas on the underside of the circuit board in which the circuit board forms vias.

[0034] Further design variants provide for the process to be used in a panel, with a plurality of electrical modules being overmolded in the tool at the same time.

[0035] The invention is explained in more detail below with reference to the figures of the drawing using several exemplary embodiments. They show: Figure 1 schematically shows an embodiment of a printed circuit board arrangement comprising an electrical module arranged on a printed circuit board, wherein the electrical module is embedded in a potting material which presses a thermally conductive material against a heat sink; Figure 1a shows a section of the printed circuit board arrangement of the Figure 1 ; Figure 2 a printed circuit board arrangement according to the Figure 1 , wherein additional details are shown with regard to the electrical module; Figure 3 shows an example of a printed circuit board assembly not according to the invention, which comprises an electrical module arranged on a printed circuit board; Figure 4 schematically shows the embedding of two electrical modules in a potting material in a manner not according to the invention, in which the underside of the electrical module is covered with the potting material; Figure 5 shows a tool for producing a printed circuit board assembly according to the Figure 1 ; Figure 6 an electrical module of a printed circuit board arrangement according to the Figure 1 , wherein the underside of the electrical module has a vertical offset at its edges to the potting material in which the electrical module is embedded; and Figure 7 shows a flow diagram of a method for producing a printed circuit board assembly according to the Figure 1 .

[0036] For a better understanding of the background of the present invention, the Figure 3 First, a printed circuit board arrangement not according to the invention is described.

[0037] The Figure 3 shows a printed circuit board assembly comprising a printed circuit board 1 and a heat sink 3. The printed circuit board 1 consists of a plurality of printed circuit board layers (not shown separately) arranged one above the other. It has a top side 11 and a bottom side 12.

[0038] Electrical modules 2 are arranged on the underside 12 of the printed circuit board 1. The connection to the printed circuit board 1 is made, for example, via surface mounting. However, this is merely an example. In addition, electrical components can also be arranged on the top side 11 of the printed circuit board 1. Of interest in the present context are the electrical modules 2 arranged on the underside 12, which are active components (for example, power electronics modules) that require cooling by a heat sink 3. For this purpose, the heat sink 3 has a recess 30 into which the modules 2 to be cooled protrude, wherein the modules 2 to be cooled come into thermal contact with the heat sink 3 on their underside.

[0039] It is disadvantageous if a gap exists between the respective module 2 and the heat sink 3, since such a gap impairs the thermal connection to the heat sink 3. To improve the thermal connection, a thermally conductive material 6 is arranged between the modules 2 to be cooled and the heat sink 3.

[0040] The printed circuit board 1 is screwed to the heat sink 3 via metal screws 5. The metal screws 3 are screwed into through-holes 15 that extend from the printed circuit board 1 into the heat sink 3. The metal screws 3 rest on the top side 11 of the printed circuit board 1 via a washer 51 and a metallization 52. They provide a compressive force with which the printed circuit board 1 is pressed against the heat sink 3. In particular, they provide the compressive force with which the electrical modules 2 to be cooled, arranged on the underside 12 of the printed circuit board 1, are pressed against the surface of the heat sink 3 via the thermally conductive material 6 to provide a good thermal transition.

[0041] The heat sink 3 can have numerous configurations. It is made, for example, of a metal such as aluminum or an aluminum alloy and has cooling surfaces (not shown separately). The heat sink 3 is, for example, an active heat sink that is actively cooled by a fan (not shown) or by means of a liquid cooling system (not shown). Alternatively, the heat sink 3 is designed as a passive heat sink.

[0042] In alternative embodiments (not shown), it can be provided that in order to improve the thermal contact between the module 2 to be cooled and the heat sink 3, a hold-down device is additionally used, which presses the circuit board against the heat sink.

[0043] The thermally conductive material 6 is pressed against the heat sink 3 in the areas A below the electrical module 2 due to the compressive force provided by the screws 5. However, in areas B between the individual electrical modules 2 or adjacent to the respective electrical module 2, the thermally conductive material 2 is only in contact with the heat sink. This is shown in the Figure 3 Not shown to scale by a warping of the thermally conductive material 2. Accordingly, there is no or only minimal mechanical pressure on the thermally conductive material 2 adjacent to the electrical modules 2. Thus, in these areas, there is only reduced heat transfer from the thermally conductive material 2 to the heat sink 3.

[0044] The Figure 1 shows an example of a printed circuit board arrangement. The basic structure is the same as with regard to the Figure 3 explained, so that the explanations for the Figure 3In accordance with the Figure 1 It is provided that the illustrated electrical modules 2 are embedded in a potting material 7. The potting material 7 is flush with the underside of the electrical module without covering the underside. The potting material 7 causes the thermally conductive material 7 to be pressed against the heat sink 3 with high mechanical pressure, even in areas B that border on the electrical modules 2 or lie between the electrical modules 2. High mechanical pressure exists both in areas A below the electrical modules 2 and in areas B between or next to the electrical modules 2.

[0045] It is provided that the potting material 7 is designed as a hard potting compound, which has a greater hardness than the thermally conductive material. The potting material 7 is, for example, an epoxy resin or another thermosetting plastic. The embedding of the electrical modules 2 in the potting material 7 is carried out, for example, by transfer molding or injection molding, as described with regard to the Figures 5 to 7 is explained.

[0046] The thermally conductive material 7 is formed, for example, by a thermally conductive film, a thermally conductive mat, or a thermally conductive paste. It can be provided that an anisotropic thermally conductive film, for example a graphite film, is used, which has a greater thermal conductivity in the plane than in the vertical direction. The use of an anisotropic thermally conductive film enables the heat emanating from the electrical module 2 to be spread over the surface. Due to the high contact pressure according to the invention, even in areas B, the spread heat can be conducted across the entire heat sink surface into the heat sink 3. One embodiment provides for the use of a thermally conductive material with a high thermal conductivity in the plane in the range between 200 W / mK and 1000 W / mK.

[0047] As shown below in the detailed view of the Figure 1a which is explained a part of the circuit board arrangement of the Figure 1in the area of ​​an electrical module 2, the potting material 7 also serves to electrically insulate critical areas between the electrical module 2 and the circuit board 1 as well as on the circuit board 1.

[0048] Thus, the potting material 7 also fills a gap 9 extending between the top side 21 of the electrical module 2 and the bottom side 12 of the printed circuit board 1. Furthermore, the gap 9 contains electrical contacts 8, via which the electrical module 2 is electrically and mechanically connected to the bottom side 12 of the printed circuit board 1. As described with respect to the Figure 2 As explained, these electrical contacts 8 typically each comprise a solder pad on the top side of the electrical module, a solder layer and a solder pad on the bottom side of the circuit board.

[0049] The encapsulating material 7 extends in the gap 9 in areas 71 adjacent to the electrical contacts 8 between the underside 12 of the printed circuit board 1 and the top side 21 of the electrical module 2. It replaces an underfill material that would have to be introduced into the gap 9 by means of an underfill process. This reduces the risk of bubble formation in the gap 9 between the electrical module 2 and the printed circuit board 1.

[0050] Furthermore, the potting material 7 also surrounds and insulates an area 72 on the underside 12 of the circuit board 1, in which the circuit board forms through-contacts 85. The Figures 1, 1a schematically and by way of example only one such via 85. The vias 85 serve, for example, to apply high voltage to solder pads on the underside of the printed circuit board 1.

[0051] It is noted that the number shown is two electrical modules 2 in the Figure 1 is to be understood merely as an example. In particular, two or more rows of electrical modules can be provided one behind the other (perpendicular to the plane of the drawing).

[0052] It should also be noted that the encapsulation material 7 extends to the underside 12 of the circuit board 1, thus essentially completely filling the recess 30 in the heat sink 3 (except for possible edge areas where the recess 30 is not filled with encapsulation material). This means that heat emanating from other electrical components of the circuit board (not shown) can also be dissipated into the heat sink 7 via the circuit board 1, the encapsulation material 7, and the thermally conductive material 6.

[0053] The underside 22 of the electrical module 2, as well as the lower surface of the potting material 7, presses on the thermally conductive material 6.

[0054] The electrical modules 2 of the Figure 1 can be used in embodiments according to the Figure 2 The electrical module 2 then has a top side 21 and a bottom side 22. It comprises a ceramic circuit carrier 260, an electrical component 24, and electrical contacts 31, 32, 33 arranged on the top side 21 of the module 2. The ceramic circuit carrier 260 comprises an insulating ceramic layer 26, a metallization layer 23 arranged on the top side of the ceramic layer 26, and a further metallization layer 27 arranged on the bottom side of the ceramic layer 26. The ceramic layer 26 consists, for example, of aluminum nitride (AIN) or silicon nitride (Si 3 N 4 ). The metallization layers 23, 27 consist, for example, of copper, aluminum, silver, or tungsten.

[0055] The electrical component 24 is arranged on the metallization layer 23 via a solder layer (not separately shown). The component 24 has a bottom side 241, with which it is arranged on the metallization layer 23, and a top side 242. The top side 242 and the bottom side 241 can be metallized, for example, copper-plated. The electrical component 24 is, for example, a power semiconductor embodied as a chip.

[0056] The ceramic circuit carrier 260 and the electrical component 24 are arranged in a substrate 28, which defines the external dimensions of the electrical module 2. In one embodiment, the substrate 28 is a potting compound in which the ceramic circuit carrier 260 and the electrical component 24 are embedded. Alternatively, the substrate 28 is a printed circuit board, in which case the ceramic circuit carrier 260 and the electrical component 24 have been embedded in a printed circuit board in a printed circuit board embedding process.

[0057] The substrate 28 comprises an upper side, which also forms the upper side 21 of the module 2. The underside of the substrate 28 runs flush with the lower metallization layer 27, which forms the underside 22 of the module 2. The ceramic circuit carrier 260 is connected to the lower metallization layer 27 via a thermally conductive material 6 and a heat sink 3. Heat loss from the electrical component 24 is dissipated via the heat sink 3.

[0058] The electrical contacts 31, 32, 33 on the top side 21 of the module are provided by solder pads. The solder pads 31, 32, 33 are electrically connected to the solder pads 41, 42, 43 of the circuit board 1 via solder connections. For example, a drain connection is provided via the solder pad 31, and a source connection and a gate connection of the electrical component 24 are provided via the solder pads 32, 33.

[0059] Vias 5 extend from the solder pad 31 and extend to the upper metallization layer 23 of the ceramic circuit carrier 260. Vias 50 extend from the solder pads 32, 23 and extend to the upper side 242 of the electrical component 24.

[0060] The Figure 4 illustrates possible problems that may arise when manufacturing a printed circuit board assembly according to the Figure 1 can arise. The Figure 4 two electrical modules 2 (each with a ceramic circuit carrier 260, an electrical component 24 and a spacer 29 in a similar structure as with respect to the Figure 2explained), which are slightly tilted after soldering to the circuit board 1 (for example, by ± 50 µm). This tilting can result in the encapsulation material 7 also covering the underside of the electrical modules 2 in the areas K. However, this should be avoided because it would impair the thermal transition between the electrical module 2 and the heat sink 3.

[0061] The Figures 5-7 explain a method for manufacturing a printed circuit board assembly according to the Figure 1 , whereby it is ensured that even if the electrical modules 2 are tilted on the underside of the printed circuit board 1, the potting compound 7 does not cover the underside 22 of the electrical module.

[0062] A potting compound is provided by injection molding in a tool 110. This tool comprises a mold cavity 140 into which a printed circuit board with electrical modules 2 arranged thereon can be inserted. A molding compound 70 can be pressed into the mold cavity 140 by means of channels 120 and a press 130.

[0063] The Figure 7 explained the method. First, in step 701, at least one electrical module or several electrical modules 2 are arranged on the underside of a printed circuit board. This is done via a soldering process. Subsequently, in step 702, the printed circuit board with the electrical modules 2 is inserted into the tool 110, namely into its mold cavity 140. The underside 22 of the electrical modules is shown in the illustration of the Figure 5 directed upwards. For example, 4 × 5 electrical modules are arranged on the circuit board per panel and inserted into the tool 110.

[0064] According to step 703, a stamp with a compensating foil is then placed on the underside 22 of the electrical modules 2 and the compensating foil is pressed against the respective underside 22 via the stamp. In the illustration of the Figure 5The stamp with the compensating film (not shown separately) is placed from above onto the underside 22 of the respective module 2. The compensating film is, for example, a Teflon film. The tool 110 is then closed in step 704. A molding compound is then injected under pressure into the tool 110 via the channels 120 and left in the tool for a specific time, step 705. The volume to be overmolded is precisely defined by the tool 110 and its mold cavity 140. The electrical modules 2 are overmolded without the underside, which is each covered with a compensating film, being covered with the molding compound. The compensating film prevents this even if the modules 2 are tilted on the circuit board.

[0065] During the residence time of the molding compound in the mold 110, the molding compound vulcanizes or cures, forming the potting compound (step 706). The residence time depends on various factors such as the resin type, any fillers used, processing pressure, and processing temperature. Once the residence time is over, the mold 110 is opened, and the circuit board with the electrical modules 2 encapsulated with the potting compound is removed from the mold 110 (step 707).

[0066] Subsequently, in step 708, the electrical modules 2 are thermally coupled to a heat sink. This is done using a thermally conductive material and means for providing a pressure, corresponding, for example, to the design of the Figure 1 . The potting material adjacent to the electrical modules 2 presses the thermally conductive material against the heat sink.

[0067] The result of using a stamp with a compensation foil illustrates the Figure 6 , which represents a single electrical module 2 embedded in a potting compound 7. The electrical module is, for example, according to the Figure 2 and comprises a ceramic circuit carrier with a metallization layer 27, which forms the underside 22 of the electrical module 2. At the edges of the metallization layer 27, there is a small vertical offset V1, V2 relative to the surface of the encapsulating material 7, which is, for example, in the range between 0.01 mm and 0.1 mm. The underside 22 of the electrical module 2 is free of encapsulating material 7. The offset is caused by the compensating film, which presses against the underside 22 during injection molding.

Claims

1. Printed circuit board arrangement having: - a printed circuit board (1) with a top side (11) and a bottom side (12), - at least one electrical module (2) with a top side (21) and a bottom side (22), which is arranged with its top side (21) on the bottom side (12) of the printed circuit board (1), - a heat sink (3), - means (5) for providing a pressure with which the electrical module (2) is pressed with its bottom side (22) against the heat sink (3), and - a thermally conductive material (6) arranged between the bottom side (22) of the electrical module (2) and the heat sink (3), characterized in that the at least one electrical module (2) is embedded in a potting material (7) which is flush with the bottom side (22) of the electrical module (2) without covering the bottom side (22), wherein the potting material (7) is provided and formed to press the thermally conductive material (6) against the heat sink (3) adjacent to the at least one electrical module (2).

2. Printed circuit board arrangement according to Claim 1, characterized in that the printed circuit board arrangement has a plurality of electrical modules (2) which are embedded in the potting material (7), wherein the potting material (7) is provided and formed to press the thermally conductive material (6) against the heat sink (3) in the area (B) between the electrical modules (2).

3. Printed circuit board arrangement according to Claim 1 or 2, characterized in that the potting material (7) extends at least in sections to the bottom side (12) of the printed circuit board (1).

4. Printed circuit board arrangement according to one of the preceding claims, characterized in that the electrical module (2) has electrical solder pads (31-33) formed on its top side (21), which are each in contact with an associated electrical solder pad (41-43) of the printed circuit board (1) via a solder layer, wherein the potting material (7) extends adjacent to the solder pads (31-33) also in the gap (9) between the bottom side (12) of the printed circuit board (1) and the top side (21) of the electrical module (2).

5. Printed circuit board arrangement according to one of the preceding claims, characterized in that the potting material (7) surrounds and electrically insulates those areas on the bottom side of the printed circuit board in which the printed circuit board (1) forms vias (85).

6. Printed circuit board arrangement according to one of the preceding claims, characterized in that the potting material (7) has a hardness which is greater than the hardness of the thermally conductive material (6) and / or is an epoxy resin.

7. Printed circuit board arrangement according to one of the preceding claims, characterized in that the at least one electrical module (2) has been embedded in the potting material (7) by transfer moulding or injection moulding.

8. Printed circuit board arrangement according to one of the preceding claims, characterized in that the at least one electrical module (2) comprises: - a ceramic circuit carrier (260) having an insulating ceramic layer (26) and a metallization layer (23) arranged on the top side of the ceramic layer (26), - an electrical component (24) which is arranged on the top side of the metallization layer (23) and is electrically connected thereto, - wherein the ceramic layer (26) or a second metallization layer (27) formed on the bottom side of the ceramic layer (26) is connected to the heat sink (3) via the thermally conductive material (6).

9. Printed circuit board arrangement according to Claim 8, characterized in that the electrical component (24) is a semiconductor component, in particular a power semiconductor.

10. Printed circuit board arrangement according to Claim 8 or 9, characterized in that electrical contacts of the module (2) comprise at least a first via (5) extending from a solder pad (31) on the top side (21) to the first metallization layer (23), and comprise second and third vias (50) extending from other solder pads (32, 33) on the top side (21) to corresponding contacts on the top side (242) of the electrical component (24).

11. Printed circuit board arrangement according to one of the preceding claims, characterized in that the at least one electrical module (2) is arranged in a cavity (30) of the heat sink (3).

12. Method for producing a printed circuit board arrangement comprising the steps of: - arranging (701) and electrically contacting at least one electrical module (2) on the bottom side of a printed circuit board (1), - inserting (702) the printed circuit board (1) with the at least one electrical module (2) into a mould (110), - applying (703) a stamp with a compensating film to the bottom side (22) of the at least one electrical module (2) and pressing the compensating film against the bottom side, - closing (704) the mould (110), - injecting (705) a moulding compound into the mould (110), wherein the at least one electrical module (2) is overmoulded without the bottom side (22) of the electrical module (2) covered with the compensating film being covered with the moulding compound, - curing (706) the moulding compound to generate a potting compound (7), - removing (707) the printed circuit board (1) with the at least one electrical module (2) encapsulated with the potting compound (7) from the mould (110), and - thermally (708) coupling the at least one electrical module (2) to a heat sink (3) using a thermally conductive material (6) and means (5) for providing a pressure, wherein the potting material (7) adjacent to the at least one electrical module (2) presses the thermally conductive material (6) against the heat sink (3).

13. Method according to claim 12, characterized in that when injecting (705) the moulding compound into the mould (110), the at least one electrical module (2) is overmoulded such that the moulding compound also closes a gap (9) between the bottom side of the printed circuit board (1) and the top side of the electrical module (2).

14. Method according to Claim 12 or 13, characterized in that when injecting (705) the moulding compound into the mould (110), the at least one electrical module (2) is overmoulded such that the moulding compound also surrounds and electrically insulates those areas on the bottom side of the printed circuit board (1) in which the printed circuit board forms vias (85).

15. Method according to one of Claims 12 to 14, characterized in that in one panel a plurality of electrical modules (2) are simultaneously overmoulded in the mould.