Power module and method for manufacturing a power module

Abstract

The invention relates to a power module (1) comprising a carrier (2), wherein the carrier (2) has a ceramic (3) and a structured metallization (4), wherein at least one power semiconductor (7) and at least one load terminal (6) are arranged on the structured metallization (4), wherein the power module (1) is at least partially enclosed by an insulating material (10), wherein several dummy bond wires (8) are arranged on the structured metallization (4), wherein the dummy bond wires (8) are each attached at both ends to a common structure (9) of the structured metallization (4), and wherein the dummy bond wires (8) are arranged at the outer edges of the structured metallization (4). The invention also relates to a method for manufacturing such a power module (1).

Description

[0001] The invention relates to a power module and a method for manufacturing a power module.

[0002] Such power modules are used, for example, in the automotive sector or in the energy sector, for example in wind turbines.

[0003] The power modules comprise a substrate with a ceramic insulating layer onto which a structured metallization is applied. This structuring is achieved, for example, by etching or other processes, resulting in separate, electrically isolated structures. At least one power semiconductor, such as a transistor (e.g., MOSFET, IGBT, or GaN HEMT), is mounted on the structured metallization. Typically, multiple power semiconductors are mounted on the structured metallization and connected, for example, as at least one half-bridge. Electrical connections between the individual elements can be made via bond wires and / or leadframes. Furthermore, the power module has at least one load terminal to which a high-voltage voltage can be applied. A power module typically has multiple load terminals.For mechanical protection, the power modules are encapsulated with a potting compound, which is either a silicone gel or a harder, pourable plastic mixture (e.g., epoxy resin with fillers). Alternatively, injection molding (transfer molding) is used, where hot plastic composite materials are pressed into a mold. Thermoseptic resins (e.g., epoxy resins, phenolic resins, polyester resins, melamine resins, silicone resins) are primarily used as the material for the molding compound. A problem with such power modules is the adhesion of the potting compound or transfer mold to the substrate. This can lead to partial detachment of the potting compound or transfer mold, potentially causing insulation problems, for example, due to moisture or mechanical issues within the electrical circuit. In the following, the term "insulation material" is used generally to encompass both the potting compound and the transfer mold.

[0004] US patent 2019 / 0341366A1 discloses a semiconductor device with a stacked die structure, which can also be potted with a potting compound. For improved mechanical fixation of the dies to the substrate, dummy bond wires are proposed to connect the dies to the substrate; these dummy bond wires do not serve for electrical connection.

[0005] From US patents 5,780,772 A and 6,031,281 A, microelectronic circuits with a plurality of bond wires are known, wherein the circuits are potted with a potting compound. Dummy bond wires are placed between the bond wires to prevent them from slipping during the potting process.

[0006] From JP H06-37230A, a power module is known comprising a carrier having a structured metallization, wherein at least one power semiconductor and at least one load terminal are arranged on the structured metallization, and wherein the power module is at least partially encased by an insulating material. Dummy bond wires are arranged on one top side of the power semiconductor, each of which is mounted at both ends on a common structure and has no electrical function, serving to prevent delamination.

[0007] The invention is based on the technical problem of creating a performance module in which the adhesion between the carrier and the potting compound is improved, and of providing a corresponding manufacturing process.

[0008] The solution to the technical problem is achieved by a power module with the features of claim 1 and a manufacturing method with the features of claim 6. Further advantageous embodiments of the invention are set forth in the dependent claims.

[0009] The power module comprises a substrate, the substrate having a ceramic and a structured metallization. At least one power semiconductor and at least one load terminal are arranged on the structured metallization, and the power module is surrounded by an insulating material. Several bond wires are arranged on the structured metallization, with both ends of each bond wire attached to a common structure within the metallization. These dummy bond wires, which do not carry signals, improve the bond between the insulating material (encapsulation compound or transfer mold) and the substrate at these points, thus reducing the risk of the insulating material detaching.

[0010] According to the invention, the bond wires are arranged at the outer edges of the structured metallization, wherein the bond wires are preferably arranged distributed throughout the metallization.

[0011] In another embodiment, the bond wires are arranged at edges between metallization structures.

[0012] In another embodiment, dummy bond wires are arranged around functional elements of the power module. These functional elements can be, for example, power semiconductors, load connections, sensors, or other components. The dummy bond wires also serve to geometrically secure the functional elements against displacement, particularly when thermal processing can soften solder joints. The dummy bond wires effectively fix the functional elements in position.

[0013] In another embodiment, the insulating material, in particular the transfer mold, is an epoxy resin that encases the power module, for example by thermal extrusion.

[0014] In another embodiment, the bond wires are made of copper or a copper alloy (e.g., with Ti or Si). In principle, however, they can also be made of aluminum, an aluminum alloy, gold, or silver. It is also possible for the bond wires to be profiled, i.e., to have grooves, for example, to which the potting compound adheres better.

[0015] The process for manufacturing a power module comprises the following steps: At least one power semiconductor and at least one load connection are arranged on a ceramic substrate with a structured metallization. Electrical connections between elements of the power module are created using bonding wires in a bonding process. It should be noted that the load connections can also be applied after the bonding process. Next, several dummy bonding wires are arranged on the structured metallization, with each dummy bonding wire being attached at both ends to a structure within the metallization, and the multiple dummy bonding wires being positioned at the outer edges of the structured metallization. Finally, the power module is encapsulated with an insulating material (potted or transfer molded).

[0016] In one embodiment, the multiple dummy bond wires are bonded together during the bonding process for the electrical connections. This leaves the manufacturing time practically unchanged compared to conventional methods.

[0017] In another embodiment, several dummy bond wires are arranged at edges between metallization structures.

[0018] In another embodiment, several dummy bonding wires are arranged around functional elements of the power module.

[0019] The invention is explained in more detail below with reference to a preferred embodiment. The figures show: Fig. 1. A highly simplified side view of a performance module, Fig. 2 a schematic top view of a beam and Fig. 3. A flowchart of a process for manufacturing a power module.

[0020] In the Fig. Figure 1 is a simplified representation of a power module 1. The power module 1 has a support 2 which has a ceramic 3 as an insulating layer, on which a structured metallization 4 is applied. A further metallization 5 is applied to the underside of the ceramic 3, which serves, for example, for thermal connection to a heat sink (not shown). Two load terminals 6 and at least one power semiconductor 7 are arranged on the structured metallization 4. It is further shown that an electrical connection between the power semiconductor 7 and one of the load terminals 6 is established by means of a bond wire 15. Also shown is one of several dummy bond wires 8, which is bonded at both ends to a structure 9 (see Figure 1). Fig. 2) is arranged in the structured metallization 4. The power module 1 is encased in an insulating material 10, with the load connections 6 partially protruding from the insulating material 10.

[0021] In the Fig. Figure 2 shows a simplified top view of the structured metallization 4 of the support 2. The structured metallization 4 has separate structures 9, separated by trenches 11, where the metal has been removed. The ceramic 3 is located at the bottom of the trenches 11. Dummy bond wires 8 are arranged at the outer edges 12 of the structured metallization 4, preferably circumferentially. The number of dummy bond wires 8 depends on the available space on the structure 9 and can vary. Dummy bond wires 8 are also arranged at edges 14 between the structures. The dummy bond wires 8 have no electrical function and serve only to improve the adhesion of the insulating material 10 to the support 2. The figure also shows how dummy bond wires 8 are arranged around a functional element 13 (e.g., a power semiconductor 7).These dummy bonding wires 8 have the additional function of stabilizing the position of the functional element 13.

[0022] In the Fig. Figure 3 shows a flowchart of the process for manufacturing a power module 1. In a first step S1, at least one power semiconductor 7 is deposited onto a structured metallization 4 of a substrate 2. The connection can be a soldered or sintered joint. In a second step S2, a bonding process takes place in which electrical connections 15 are made using bond wires. Simultaneously, dummy bond wires 8 are bonded, each of which is attached at both ends to an identical structure 9. In a third step S3, load terminals 6 are then connected to the structured metallization 4, and subsequently, in a fourth step S4, the power module 1 is encased with an insulating material 10. Reference symbol list 1 power module 2 carriers 3 Ceramics 4 structured metallization 5 Metallization 6 Load connection 7 Power semiconductors 8 dummy bonding wire 9 Structure 10 Insulation material 11 trench 12 outer edge 13 Functional element 14 edge 15 Bond wire

Claims

[1] Power module (1) comprising a support (2) wherein the support (2) has a ceramic (3) and a structured metallization (4) wherein at least one power semiconductor (7) and at least one load terminal (6) are arranged on the structured metallization (4) wherein the power module (1) is at least partially enclosed by an insulating material (10), characterized by , that several dummy bond wires (8) are arranged on the structured metallization (4), wherein the dummy bond wires (8) are attached at both ends to a common structure (9) of the structured metallization (4), and wherein the dummy bond wires (8) are arranged at the outer edges (12) of the structured metallization (4). [2] Power module (1) according to claim 1, characterized by , that the dummy bond wires (8) are arranged at edges (14) between structures (9) of the structured metallization (4). [3] Performance module (1) according to any of the preceding claims, characterized by , that the dummy bond wires (8) are arranged around functional elements (13) of the power module (1). [4] Performance module (1) according to any of the preceding claims, characterized by , that the insulating material (10) is an epoxy resin. [5] Performance module (1) according to any of the preceding claims, characterized by , that the dummy bond wires (8) are made of copper or a copper alloy. [6] Method for manufacturing a power module (1) wherein at least one power semiconductor (7) and at least one load terminal (6) are arranged on a support (2) made of a ceramic (3) with a structured metallization (4), wherein electrical connections between elements of the power module (1) are made in a bonding process using bonding wires (15), wherein the power module (1) is finally at least partially encased with an insulating material (10), characterized by , that Several dummy bond wires (8) are arranged on the structured metallization (4), wherein the dummy bond wires (8) are attached at both ends to a common structure (9) of the structured metallization (4), and wherein the dummy bond wires (8) are arranged at the outer edges (12) of the structured metallization (4). [7] Method according to claim 6, characterized by , that the multiple dummy bond wires (8) are bonded in the bonding process for the electrical connections. [8] Method according to claim 6 or 7, characterized by , that further dummy bond wires (8) are arranged at edges (14) between structures (9) of the metallization (4). [9] Method according to any one of claims 6 to 8, characterized by , that several dummy bonding wires (8) are arranged around functional elements (13) of the power module (1).

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