Power module with a circuit carrier

Abstract

The invention relates to a power module (10) comprising a circuit carrier (12) on which at least one electronic component (22) is arranged and on which a number of electrically conductive layers (26, 28, 30) extend, in particular at least one first DBC-Cu layer (26) which is electrically contacted by means of at least one wire bond connection (20). The circuit carrier (12), the at least one electronic component (22), and the electrically conductive layers (26, 28, 30) are provided with a molding compound (14). The at least one wire bond connection (20) and the at least one electronic component (22) are substantially completely encapsulated in the molding compound (14), which laterally adjoins conical elevations / tops (58) of a gel material or a sealing adhesive (42) that surround the at least one electronic component (22) and / or the at least one wire bond connection (20).Furthermore, the invention relates to the use of the power module (10) in power electronics of an electric drive.

Description

Technical area The invention relates to a power module with a circuit carrier on which at least one electronic component is arranged and a number of electrically conductive layers extend, in particular at least one first DBC-Cu layer, which is electrically contacted by means of at least one wire bond connection. The circuit carrier, the at least one electrical component, and the electrically conductive layers are provided with a molding compound. Furthermore, the invention relates to the use of the power module in the power electronics of an electric drive. State of the art DE 10 2012 112 769 relates to a module with a discrete device mounted on a DCB substrate. A module contains a DCB substrate and a discrete device mounted on the DCB substrate, wherein the discrete device comprises a leadframe, a semiconductor chip mounted on the leadframe, and an encapsulation material covering the semiconductor chip. A silicone gel covers bond wires and semiconductors in the area of the circuit carrier, with a molded body adjoining the silicone gel. US 9 433 792 B2 discloses a semiconductor module in which bond wires and semiconductors are covered with a silicone gel, with a molded housing adjoining the silicone gel. EP 3 276 660 B1 relates to a power semiconductor module comprising a module housing, a substrate, and a semiconductor chip attached to the substrate and arranged on the module housing. A dielectric first encapsulation is provided, which is attached in the module housing and is in physical contact with both the semiconductor chip and the substrate and has a first modulus of elasticity. A dielectric second encapsulation is provided, which is attached in the module housing and has a second modulus of elasticity, wherein the first encapsulation is a silicone rubber and is arranged between the substrate and the second encapsulation, and the semiconductor chip is arranged between the first encapsulation and the substrate. EP 2 958 139 A1 relates to a semiconductor module with an encapsulating compound covering at least one semiconductor component. A semiconductor module comprises a ceramic circuit carrier supporting at least one semiconductor component, wherein the at least one semiconductor component is covered by an encapsulating compound. The encapsulating compound comprises a cured inorganic cement and a thermal expansion coefficient in the range between 2 and 100 ppm / K. The ceramic of the ceramic circuit carrier is selected from the group consisting of ceramics based on aluminum oxide, aluminum nitride, or silicon nitride. Disclosure of the invention According to the invention, a power module is proposed with a circuit carrier on which at least one electronic component is arranged and on which a number of electrically conductive layers run, in particular at least a first DBC-Cu layer, which is electrically contacted by means of at least one wire bond connection, and the circuit carrier, the at least one electronic component, and the electrically conductive layers are provided with a molding compound. The at least one wire bond connection and the at least one electronic component are essentially completely encapsulated in the molding compound, which laterally adjoins conical tops / elevations of a gel material or a sealing adhesive that surround the at least one electronic component and / or the at least one wire bond connection.With this, the solution proposed according to the invention can prevent the formation of cracks on overmolded wire bond connections. In an advantageous development of the solution proposed according to the invention, the gel material used on the power modules proposed according to the invention is a silicone gel, a sealing adhesive or a glob-top material. In an advantageous development of the power module proposed according to the invention, the electronic components are selected from a group comprising: conductively bonded, passive electronic components, in particular temperature sensors, such as NTCs, PTCs, contact pads, drain contact pads or ASICs. Furthermore, the power module proposed according to the invention is characterized in that the following electrically conductive layers are included, namely: - a first DBC-Cu layer, which is uncoated or has an Ag coating, - a DBC-Al2O3 layer and / or - a DBC-Cu layer In an advantageous development of the power module proposed according to the invention, the electronic components, in particular passive electronic components such as NTCs, are fully encapsulated by the gel material or the sealing adhesive. In the power module proposed according to the invention, drain contact pads or contact pads can further be separated from the molding compound by conical elevations / tops made of gel material or sealing adhesive. In an advantageous development of the power module proposed according to the invention, at least the foot region and / or the heel region of the at least one wire bond connection are embedded in the gel material or the sealing adhesive. The power module proposed according to the invention is further designed such that wire bond connections, passive electronic components, in particular NTCs, and drain contact pads on AMB surfaces and / or SiC surfaces and / or DBC surfaces are provided with gel material on a circuit carrier. This allows said components on the top side of the circuit carrier to be effectively protected against external environmental influences. Furthermore, the invention relates to a method for producing a power module with a circuit carrier, with at least the following method steps: a) applying a gel material to electronic components, contact pads and / or wire bond connections which are arranged on AMB surfaces, SiC surfaces and / or DBC surfaces of the circuit carrier and b) overmolding the power module or the circuit carrier which is equipped with a molding material according to method step a). Furthermore, the invention relates to the use of the power module in a power electronics system of an electric drive. Advantages of the invention The solution proposed according to the invention advantageously prevents the occurrence of cracks or delaminations and their propagation in overmolded wire bonds and in the conductive adhesive used for conductively bonded components, such as temperature sensors, in particular NTCs, or in contact pads located in the molding compound. On the one hand, the solution proposed according to the invention protects wire bonds and passive electronic components against environmental influences. On the other hand, the different materials of molding compound and gel material, in particular silicone gel, prevent cracks from occurring during the lifetime of the power module, through which moisture could penetrate, which is highly undesirable. The solution proposed by the invention effectively protects the wire bond connections as well as passive electronic elements and contact pads by applying the gel material and subsequently overmolding said components of the power module. Areas on DBC substrates or layers to which components are bonded using a conductive adhesive may, even in the case of DBC substrates not coated with Ag, have a thin Ag coating in these areas, the surface area of which is often larger than that of the conductive adhesive. Direct bonding to pure Cu should be avoided, as Cu oxidation can vary. The same applies to the use of wire bonds, insofar as an Ag layer is necessary. Short description of the drawings Embodiments of the invention are explained in more detail with reference to the drawings and the following description. 1 along the dashed line, Fig. 2 shows a base of a wire bond connection surrounded by a gel material, Fig. 3 shows gelling of a passive electronic component, for example an NTC, of side edges of a drain pad protruding from the molding compound and partial gelling of a wire bond connection, Fig. 4 is a plan view of the passive electronic components, drain pads and bond connections accommodated on the circuit carrier, Fig. 5 shows gelling of the electronic components shown in Fig. 4 on the circuit carrier and Fig. 5 .1 is a detailed view of Fig. 5 . Embodiments of the invention In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention. Fig. 1 shows a top view of a power module 10 comprising a circuit carrier 12. A number of electronic components are accommodated on the top side of the circuit carrier 12, which are enclosed by a molding compound 14. The circuit carrier 12 of the power module 10 is mounted on a heat sink 16, which is shown in a sectional view in Fig. 1.1. Fig. 1 .1 shows a sectional view through the circuit carrier 12 of the power module 10 according to Fig. 1 along the dashed section line shown there. From the illustration in Fig. 1.1 it can be seen that the circuit carrier 12 is received on a contact surface 18 of the heat sink 16. The circuit carrier 12 comprises at least one wire bond connection 20, of which only one is shown in the sectional illustration in Fig. 1.1. The circuit carrier 12 comprises a number of electronic components 22 and an Alloy 42 layer 24. Furthermore, on the circuit carrier 12, on the Alloy 42 layer 24, electrically conductive layers, such as the first DBC-Cu layer 26, a DBC-Al2O3 layer 28 and a further, second DBC-Cu layer 30, are received. The first DBC-Cu layer 26 is electrically contacted by one end of the wire bond connection 20, according to the sectional illustration in Fig. 1.1. Below the Alloy 42 layer 24 according to the sectional view in Fig. 1 .1 there are a first AMB-Cu layer 32, an AMB-Si3N4 layer 34 and a further, second AMB-Cu layer 36. On the contact surface 18, the arrangement of the layers 32, 34, 36 is connected to the upper side of the contact surface 18, for example by a combination of cold gas sprayed Cu 38 and an Innolot 40. Waste heat generated during operation of the power module 10 is removed and dissipated via the heat sink 16, which is located below the circuit carrier 12 of the power module 10, so that excessive temperature peaks can be avoided during operation of the power module 10. Fig. 2 shows a wire bond connection 20 in a schematic view. Fig. 2 shows a portion of the wire bond 20 with a foot 44 or its top side 46, which is bonded to a first DBC-Cu layer 26. The foot 44 of the wire bond 20 is largely surrounded by a conical top or elevation 58 made of a gel material 42. The gel material 42 is a gel, such as silicone gel or a sealing adhesive. As can be seen from the enlarged illustration in Fig. 2, the entire foot 44 and part of a heel region 56 of the wire bond 20 are enclosed by the gel material 42. The arrangement in Fig. 2 is enclosed by a molding compound 14. Since very high strains and stresses can occur locally in the base 44 of the wire bond connection 20, as a delaminated mold directly engages the underside of the base 44 and a significant displacement occurs over a short length, damage or delamination can occur. The same applies to passive components bonded using a conductive adhesive 50 (see illustration in Fig. 3), such as temperature sensors 52, especially NTCs. Drain or contact pads 48 can also be affected. To protect the wire bond connections 20, their base 44 or another part of the heel area 56 can be gel-coated. Even if delamination of the molding compound 14 occurs from the surface, the molding compound 14 can impart displacement to the wire bond connection 20, but this displacement occurs over a significantly greater distance compared to the case where the gel material 42 is missing. This means that the strain occurring in the wire bond connection 20 is significantly lower when using gel material 42 (estimated to be 10 times lower), resulting in a significantly longer service life. From the illustration according to Fig. 3 it can be seen by way of example that here on an upper side 46, for example of the first DBC-Cu layer 26, a drain pad 48 is glued by means of a conductive adhesive 50. Furthermore, in the illustration according to Fig. 3, a passive electronic component 22 in the form of a temperature sensor 52, in particular an NTC, is applied to the upper side 46 of the first DBC-Cu layer 26, as well as the wire bond connection 20 already shown in connection with Fig. 2. From Fig. 3 it can be seen that here, for example, the passive electronic component 22 in the form of the temperature sensor 52, in particular an NTC 52, is embedded in a full encapsulation 54 made of gel material 42. The molding compound 14, which in turn surrounds the gel material 42, does not come into contact in any way with the passive electronic component 22 in the form of the temperature sensor, in particular an NTC 52. Thus, after delamination of the molding compound 14, no forces perpendicular to the substrate plane, i.e. perpendicular to the top side 46 of the first DBC-Cu layer 26, can act on the passive electronic component 22 in the form of the temperature sensor 52. In the same way, the drain pads 48 shown here as examples are protected in such a way that their side walls are provided with a gel material 42, which forms a conical top or elevation 58 around the side walls of the drain pad 48. In this case, too, the molding compound 14 has no contact with the drain pad 48 itself, so that no forces perpendicular to the substrate plane can occur on the drain pad 48 after mold delamination. The same applies to the foot 44 or the heel area 56 of the wire bond connection 20, partially shown on the right in Fig. 3. The gel material 42 can be, for example, the gel KER-6230-F (ShinEtsu) or alternatively Semicosil911 (Wacker) or TSE3046S (Momentive). Furthermore, a sealing adhesive 42, such as Elastosil RT722 (Wacker), can be used. From the illustration in Fig. 4, it can be seen that, for example, the first DBC-Cu layer 26 is formed on a DBC surface 64, at least one temperature sensor 52, in particular in the form of an NTC, several electronic components 22, for example drain pads 48, and a number of wire bond connections 20 are formed on the circuit carrier 12. These are located at different locations on the DBC surface 64 of the first DBC-Cu layer 26. Fig. 5 shows in conjunction with Fig. 4 that the components shown in Fig. 4, in particular the temperature sensor 52, which is embodied as an NTC by way of example, the wire bond connections 20 and the at least one drain pad 48 are provided in the marked areas with gelling by means of gel material 42 or a sealing adhesive 42. All positions shown in Fig. 5 can be provided with the gel material 42, ie all wire bond connections 20, not only on a DBC surface 64, but equally on an AMB surface 60 or a SiC surface 62. After the gelling of the components shown in Fig. 4 as shown in Fig. 5, the power module 10 can be overmolded with the molding compound 14 and electrically tested. Fig. 5.1 again shows, on an enlarged scale, several selected positions where, for example, the drain pad 48 is located, the upper side of which is free of gel material 42, since bonded connections are formed here by welding. In contrast, the electronic component 22 shown in Fig. 5.1 in the form of the NTC 52 is shown in full encapsulation 54 made of gel material 42. The gelation of the foot 44 or the heel region 56 of the wire bond connection 20 according to Fig. 5.1 essentially corresponds to the illustration in Figs. 2 and 3. According to the proposed invention, the power module 10 with said circuit carrier 12 is manufactured in such a way that, according to paragraph a), a gel material 42 is applied to electrical components 22, drain pads 48 and / or wire bond connections 20 that have been applied to AMB surfaces 60, SiC surfaces 62 and / or DBC surfaces 64 of the circuit carrier 12, and, according to paragraph b), the power module 10 or the circuit carrier 12, which is populated according to method step a), is encapsulated with a molding compound 14. The invention further relates to the use of the power module 10 proposed according to the invention in an inverter or power electronics of an electric drive. The power module 10 can be used to generate an alternating voltage from a direct voltage and can be used in at least one fuel cell or fuel cell arrangement of an electrically powered vehicle. The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art. QUOTES CONTAINED IN THE DESCRIPTION This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature DE 10 2012 112 769

[0002] US 9 433 792 B2

[0003] EP 3 276 660 B1

[0004] EP 2 958 139 A1

[0005]

Claims

Power module (10) having a circuit carrier (12) on which at least one electronic component (22) is arranged and on which a number of electrically conductive layers run, in particular at least one first DBC-Cu layer (26), which is electrically contacted by means of at least one wire bond connection (20), and the circuit carrier (12), the at least one electrical component (22) and the electrically conductive layers (26, 28, 30) are provided with a molding compound (14), characterized in that the at least one wire bond connection (20) and the at least one electronic component (22) are substantially completely encapsulated in the molding compound (14) and connects the latter laterally to conical tops / elevations (58) of a gel material or of a sealing adhesive (42), which surround the at least one electrical component (22) and / or the at least one wire bond connection (20).Power module (10) according to claim 1, characterized in that the gel material (42) is a silicone gel, a sealing adhesive or a glob top material.Power module (10) according to Claims 1 and 2, characterized in that the electronic components (22) are selected from the group comprising passive components which are bonded to the conductor, in particular NTCs, drain contact pads, contact pads or ASICs.Power module (10) according to claims 1 to 3, characterized in that the electrically conductive layers comprise: - a first DBC-Cu layer (26) that is uncoated or has an Ag coating, - a DBC-Al 2 O 3- layer (28), - a second DBC-Cu layer (30).Power module (10) according to Claims 1 to 4, characterized in that the electronic components (22), in particular passive electronic components such as NTCs (52), are surrounded in full encapsulation (54) by the gel material or by the sealing adhesive (42).Power module (10) according to Claims 1 to 4, characterized in that drain contact pads (48) are separated from the molding compound (14) by conical tops / elevations (58) made of gel material (42) or sealing adhesive (42).Power module (10) according to Claims 1 to 4, characterized in that at least its foot region (44) and / or its heel region (56) are embedded in the gel material (42) or the sealing adhesive (42) on the at least one wire bond connection (20).Power module (10) according to Claims 1 to 7, characterized in that wire bonds (20), passive electronic components (22), in particular NTCs (52), and drain contact pads (48) on AMB surfaces (60), SiC surfaces (62) and / or DBC surfaces (64) are provided with mold material (42) on a circuit carrier (12).Method for producing a power module (10) according to one of Claims 1 to 8 with a circuit carrier (12), with the following method steps: a) applying a gel material (42) to electronic components (22), contact pads (48) and / or wire bonds (20) which are arranged on AMB surfaces (60), SiC surfaces (62) and / or DBC surfaces (64) of the circuit carrier (12), b) injection moulding a moulding compound (14) around the power module (10) or the circuit carrier (12) fitted according to method step a).Use of the power module (10) according to one of Claims 1 to 8 in power electronics of an electrically driven vehicle.Use of the power module (10) according to one of Claims 1 to 8 for generating an AC voltage from a DC voltage or in a vehicle driven by means of a fuel cell.

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