Power module, inverter and method of manufacturing a power module
By using nanostructured connecting elements and bonding elements in the power module through sintering, the limitations of power density and efficiency in the existing power module are solved, achieving efficient and stable electrical connection and mechanical strength, which is suitable for electric drive devices for motor vehicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2024-11-28
- Publication Date
- 2026-05-29
AI Technical Summary
Existing power modules have limitations in improving power density and efficiency, especially in electric drive systems for motor vehicles, where it is difficult to achieve efficient electrical connections and mechanical stability.
The connecting elements with bottom and top nanostructures are sintered together with the bonding elements to form a high-density structure, which improves mechanical strength and conductivity. Copper or copper alloy materials are used to increase current carrying capacity, and higher bonding force is applied by ultrasonic bonding.
This technology enables high power density and high efficiency power modules, extends lifespan, reduces thermomechanical stress, and is suitable for smaller structural sizes and higher current densities.
Smart Images
Figure CN122123201A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a power module, particularly for use in inverters or DC-DC converters, especially in electric drive systems for motor vehicles. Furthermore, the invention relates to an inverter incorporating the power module and a method for manufacturing the power module. Background Technology
[0002] Power modules or power electronic modules with power semiconductor elements are known and used in power electronic devices, such as inverters or DC-DC converters, particularly in the electric drive systems of motor vehicles. Such power modules are used, for example, in the power inverter (product name: EPF2.8) of Vitesco Technologies GmbH.
[0003] As with almost all technological devices, there is a general requirement for power modules to increase their power density and thus improve efficiency.
[0004] Therefore, the purpose of this application is to provide a high-efficiency power module with high power density. Summary of the Invention
[0005] The above-mentioned objectives are achieved through the subject matter of the independent claims. Advantageous embodiments thereof are the subject matter of the dependent claims.
[0006] According to a first aspect of the invention, a power module or power electronic module is provided, particularly for inverters or DC-DC converters, especially for electric drive systems of motor vehicles.
[0007] The power module has a power semiconductor element or power semiconductor switch, the power semiconductor element having a sinterable top-side electrical contact surface and a bonding element having a sinterable bottom side and a bondable top side, wherein the top side serves as a bonding surface (for bonding bonding wires or bonding strips) to form a top-side bonding connection for the top-side contact surface of the power semiconductor element.
[0008] The power module also features a dual-sided sinterable connection element with a bottom-side sinterable nanostructure and a top-side sinterable nanostructure. The connection element is sintered to the top-side contact surface via the bottom-side nanostructure and to the bonding element via the top-side nanostructure, thereby physically and electrically connecting the bonding element to the power semiconductor element or its top-side contact surface.
[0009] For example, the bonding element is in the form of a sheet or a small metal sheet, and acts as a bonding buffer.
[0010] The connecting element has a central portion, as well as bottom and top nanostructures, which are distributed on two opposite sides of the central portion.
[0011] The connecting element acts as a mating element between mating components (i.e., between the power semiconductor element and the bonding element) and forms a sintered connection between these two mating components. After the sintering process, the connecting element thus connects the bonding element and the power semiconductor element physically, with low resistance, and thermally.
[0012] The connecting element disposed on the top side electrical contact surface of the power semiconductor element gives the contact surface mechanical strength, thereby allowing the bonding element to be used as a bonding buffer. Due to its functional requirements, the bonding buffer has significantly higher mechanical strength than the simple contact surface of the power semiconductor element, which would otherwise lead to cracks or pre-damage to the contact surface or the structure directly below it without the connecting element.
[0013] The nanostructures formed on both sides of the connecting element enable a high-density structure between the mating components (i.e., the connecting element on one side and the top electrical contact surface and bonding element of the power semiconductor element on the other side). This structure exhibits high electrical and thermal conductivity as well as high mechanical stability, thereby achieving a reliable electrical connection between the top electrical contact surface of the power semiconductor element and the bonding element. This allows for the application of power semiconductor elements with higher power density and / or smaller contact surface, resulting in a smaller structural size for the power module.
[0014] The high thermal conductivity and mechanical stability of this structure in power semiconductor devices enable the use of stiffer and therefore thicker bonding connections, allowing the use of copper-based bonding wires or tapes, which (compared to aluminum-based bonding connections) have higher current-carrying capacity. In particular, the high mechanical stability allows for the application of higher bonding forces to the bonding elements during bonding and higher ultrasonic energy in the case of ultrasonic bonding. This is especially true because the use of connecting elements between the bonding elements and the top contact surface of the power semiconductor device, and the formation of a stable sintered connection through these connecting elements, compensates for or reduces the thermomechanical stress between the bonding connection or the bonding elements and the top contact surface of the power semiconductor device. This also improves the lifespan of the aforementioned structure in conjunction with the power semiconductor device and the power module.
[0015] Accordingly, a solution is provided for achieving a power module with high efficiency and high power density.
[0016] For example, the connecting element has a sheet-like middle portion, especially in the form of a small metal sheet, on which bottom and top nanostructures are respectively distributed on its two opposite sides.
[0017] For example, the bottom and / or top nanostructures each have a large number of sinterable rod-shaped or hair-like protrusions that extend outward from the intermediate plane of the connecting element or the intermediate portion of the connecting element (at least partially or in their respective segments). Here, the intermediate plane of the connecting element is the plane in which the longitudinal and transverse axes of the connecting element are provided.
[0018] When a sintered connection is formed between the nanostructure formed on one side of the connecting element or its two sides and the top contact surface of the power semiconductor element and the bottom side of the bonding element, the rod-shaped or hair-like protrusions deform and diffuse into the contact surface of the power semiconductor element and the bottom side of the bonding element. This results in a highly densified structure, forming a connection between the mating components that exhibits high physical, electrical, and thermal conductivity and high mechanical stability, while being virtually free of organic contaminants and halogens.
[0019] Furthermore, the rod-shaped or hair-like protrusions can elastically absorb the thermomechanical stress that may exist between the contact surfaces of the bonding elements and the power semiconductor elements after sintering, thereby having a positive effect on the lifespan of the power module.
[0020] The diameter of the protrusion—excluding deviations caused by manufacturing techniques or manufacturing tolerances—can be less than 1 micrometer, or less than 750 nanometers, or less than 500 nanometers, or less than 300 nanometers, or about 100 nanometers.
[0021] The connecting element, for example, has a central portion as a carrier, preferably made of copper or a copper alloy, and has nano-sized rod-shaped protrusions or nanorod covering layers on its two sides.
[0022] The length, diameter, and density of the nanorods are variable and can be selected as required. However, the diameter of the nanorods is within the aforementioned nanoscale range. The intermediate portion can be made of different conductive materials and can be plated with a metal, such as copper, silver, gold, or nickel, or an alloy of one or more of these metals. This metal plating can be achieved by electroplating deposition, for example, after placing a sponge with a corresponding shape for forming protrusions on the intermediate portion.
[0023] For example, the connecting element is integrally molded and made of copper or a copper alloy.
[0024] For example, the bonding element is also made of copper or a copper alloy.
[0025] The top-side bonding connection can be formed, for example, by means of bonding wires or bonding strips. In this case, the bonding wires or bonding strips can be made of copper or a copper alloy.
[0026] The power semiconductor element or power semiconductor switch can be formed as a SiC (silicon carbide) semiconductor element or a SiC power semiconductor switch, or it can be formed as a Si (silicon) semiconductor element or a Si power semiconductor switch, or it can be formed as a GaN (gallium nitride) semiconductor element or a GaN power semiconductor switch.
[0027] By using the connecting element to sinter the bonding element or the bonding buffer for the top contact surface of the power semiconductor element, it is possible to use (significantly) smaller power semiconductor elements with higher current density and current carrying capacity, such as SiC power semiconductor switches.
[0028] The power module may also have a substrate with a sinterable electrical contact surface. In this case, the power semiconductor element may have a sinterable bottom-side electrical contact surface, which is sintered to the contact surface of the substrate and physically and electrically connected to the contact surface of the substrate.
[0029] The substrate can be formed as a ceramic-based circuit carrier, such as a DCB substrate (Direct Copper Bonded Substrate) or an AMB substrate (Active Metal Brazed Substrate), or a metal-based circuit carrier, such as an IMS (Insulated Metal Substrate).
[0030] According to one exemplary embodiment, the bonding element and the connecting element can be integrally formed.
[0031] According to another exemplary embodiment, the bonding element may be metallized by a metal layer made of a metal material different from the bonding element substrate. In particular, the (top) side of the bonding element may be metallized by a metal layer made of a metal material different from the bonding element substrate.
[0032] According to yet another exemplary embodiment, the bonding element may have multiple metal layers made of different metals or metal alloys, which are integrally formed with each other.
[0033] By using connecting and bonding elements, a top-side electrical connection surface is constructed for the power semiconductor device. This surface is sufficiently rigid and mechanically stable, and also imparts sufficient rigidity and mechanical stability to the power semiconductor device or the organization composed of the power semiconductor device, connecting elements, and bonding elements. Thus, an "external" electrical connection element (such as a bonding wire or bonding strip), made of copper or a comparable material with high rigidity, high conductivity, and high current throughput, can be physically and electrically connected to it without damaging the power semiconductor device or the organization due to the mechanical load of the connecting element.
[0034] The materials or material composition of the bonding elements can be freely selected according to needs or requirements. The top side of the bonding elements can also be metallized differently according to needs or requirements. Furthermore, the bonding elements can be integrally formed from multiple layers or material compositions of different materials. Accordingly, for different technical requirements of top-side contact power semiconductor elements, commercially available, low-cost standard semiconductor chips can be used; these chips only have predetermined material layers (or layer complexes), such as an aluminum layer for the top-side contact surface, achieving "arbitrary metallization" by employing "free" material selection on the bonding elements to meet the needs or requirements. Expensive or technically difficult-to-achieve metallization of the top-side contact surface of standard semiconductor chips (e.g., using gold, silver, palladium, copper, and / or tin) can be achieved using relatively low-cost connecting elements. Therefore, for different technical requirements of the top-side contacts of power semiconductor elements, commercially available, low-cost standard semiconductor chips can be used.
[0035] According to a second aspect of the invention, an inverter or power inverter is provided, particularly for electric drive systems of motor vehicles.
[0036] The inverter has one or more of the aforementioned power modules, and one or more drive circuits for driving the power modules. The drive circuits are electrically or signal connected to each power module via one or more control signals.
[0037] According to a third aspect of the present invention, a method for manufacturing a power module is provided.
[0038] According to this method, a substrate with sinterable electrical contact surfaces is provided. Sintering paste is disposed on the contact surfaces of the substrate, for example, by printing or coating.
[0039] In addition, a power semiconductor element having a sinterable top-side electrical contact surface and a sinterable bottom-side electrical contact surface is provided and disposed on a substrate, wherein the power semiconductor element is placed on and in contact with the sintering paste through its bottom-side contact surface.
[0040] Additionally, a dual-sided sinterable connection element is provided, which has a bottom-side sinterable nanostructure and a top-side sinterable nanostructure. The connection element is arranged on the top-side contact surface of a power semiconductor element, wherein the connection element is placed on and in contact with the top-side contact surface of the power semiconductor element through its bottom-side nanostructure.
[0041] Furthermore, a bonding element having a sinterable bottom side and a bondable top side is provided for forming a top-side bonded connection. The bonding element is arranged on the connecting element, wherein the bonding element is placed on and in contact with the top-side nanostructure of the connecting element via its sinterable bottom side.
[0042] Subsequently, the following sintered connection is formed between the substrate, the power semiconductor element, and the bonding element: - A first sintered connection is formed between the bottom contact surface of the power semiconductor device and the contact surface of the substrate using sintering paste. - A second sintered connection is formed between the top contact surface of the power semiconductor device and the connecting element through the bottom nanostructure of the connecting element; and - A third sintered connection is formed between the bottom side of the bonding element and the connecting element through the nanostructure on the top side of the connecting element.
[0043] In particular, the three types of sintering connections mentioned above are formed (simultaneously) in the same sintering process.
[0044] Here, the connecting element, like the sintering paste (as a mating element between the substrate and the power semiconductor element), serves as a mating element between the power semiconductor element and the bonding element during sintering. After the sintering process, the connecting element connects the bonding element and the power semiconductor element physically, with low resistance, and thermally.
[0045] The advantageous embodiments of the power module described above can also be applied to the above method, and considered as advantageous embodiments of the method, as long as they are applicable. Attached Figure Description
[0046] A specific exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Wherein: Figure 1 An exploded view schematically illustrates a portion of a power module according to an exemplary embodiment of the present invention; and Figure 2 A schematic cross-sectional view is shown from Figure 1 This part of the power module. Detailed Implementation
[0047] Figure 1An exploded view schematically illustrates a portion of a power module LM according to an exemplary embodiment of the present invention. This illustration is intended to show the power module LM prior to assembly, and particularly prior to the sintering process described later. Figure 2 The schematic cross-sectional view shows the source... Figure 1 The state of this part of the power module LM after the assembly or sintering process.
[0048] The power module LM has a substrate ST, such as a DCB or AMB substrate, with a sinterable electrical contact surface KF0, which is formed, for example, as a copper wire.
[0049] The power module LM also has a layer of sintering paste SP (e.g., DTF, "Die Transfer Film"), which is printed or coated on the contact surface KF0 of the substrate ST.
[0050] The power module LM also includes a power semiconductor element LE, which is formed as a SiC power semiconductor switch and has a sinterable top-side electrical contact surface KF1 (with a corresponding coating for sintering if necessary), which constitutes the source terminal of the power semiconductor switch; a bondable top-side electrical contact surface KF2 (with a corresponding coating for bonding if necessary), which constitutes the gate terminal of the power semiconductor switch; and a sinterable bottom-side electrical contact surface KF3 (with a corresponding coating for sintering if necessary), which constitutes the drain terminal of the power semiconductor switch. The sinterable contact surfaces KF1 and KF3 have corresponding coatings for sintering if necessary. Accordingly, the bondable contact surface KF2 has a corresponding coating for bonding if necessary.
[0051] The power semiconductor element LE or SiC power semiconductor switch is placed on the sintering paste SP via its sinterable bottom contact surface KF3, and is physically and electrically connected to the substrate ST via the sintering connection of the sintering paste SP with the contact surface KF0 of the substrate ST.
[0052] The power module LM also has a double-sided sinterable connector VE made of copper or a copper alloy. This connector has a sheet-like intermediate portion MT, a bottom-side sinterable nanostructure NS1 formed on the bottom side of the intermediate portion MT, and a top-side sinterable nanostructure NS2 formed on the top side of the intermediate portion MT. The bottom-side nanostructure NS1 has numerous sinterable rod-shaped or hair-like protrusions VS, which extend outward from the bottom side of the intermediate portion MT and thus from the intermediate plane ME of the connector VE. Similarly, the top-side nanostructure NS2 has numerous sinterable rod-shaped or hair-like protrusions VS, which extend outward from the top side of the intermediate portion MT and thus from the intermediate plane ME of the connector VE, and are therefore also away from the protrusions VS of the bottom-side nanostructure NS1. The protrusions VS of both nanostructures NS1 and NS2 have a diameter of less than 1 micrometer, or an average diameter of approximately 700-800 nanometers.
[0053] The power module LM also has a bonding element BE made of copper or copper alloy, which is formed in the form of a copper sheet and has a sinterable bottom side US (with a corresponding coating for sintering if necessary) for forming a sinterable connection and a bondable top side OS (with a corresponding coating for bonding if necessary) for forming a top side bonding connection BV1.
[0054] The connecting element VE is sintered to the top contact surface KF1 of the power semiconductor element LE via a bottom-side nanostructure NS1. The connecting element VE is also sintered to a bonding element BE or its bottom side US via a top-side nanostructure NS2, thereby physically and electrically connecting the bonding element BE to the top contact surface KF1 of the power semiconductor element LE.
[0055] The connecting element VE, like the sintering paste SP, serves as a mating element that mates the bonding element BE with the top contact surface KF1 of the power semiconductor element LE.
[0056] A bonding wire or bonding strip, or a circular copper wire or strip, made of copper or a copper alloy, is bonded to the bondable top side OS of the bonding element BE. This forms a bonding connection BV1 leading to the bonding element BE and thus to the top contact surface KF1 of the power semiconductor element LE, and is connected to another electrical component (not shown in the figures) configured according to the function of the power module LM. The bonding connection BV1 is used to transmit load currents with current intensities exceeding several amperes up to 20 amperes.
[0057] The power module LM shown here may be, for example, part of an inverter for driving an electric vehicle, wherein the inverter, in addition to three or more such power modules LM, has a drive circuit for driving these power modules LM. The drive circuit is connected to each power module via a control signal connection and is also electrically or signalally connected to each power semiconductor element LE or its respective bondable top contact surface KF2 via a second bonding connection BV2 (bonding wire made of aluminum or aluminum alloy).
[0058] Figure 2 The manufacturing or assembly process of the power module LM shown is as follows: First, a substrate ST with a sinterable electrical contact surface KF0 is provided. Sintering paste SP is printed or coated onto the contact surface KF0 and dried if necessary. A power semiconductor element LE is placed on the sintering paste SP via its sinterable bottom-side contact surface KF3. A connecting element VE is placed on the sinterable top-side contact surface KF1 of the power semiconductor element LE via its sinterable bottom-side nanostructure NS1. A bonding element BE is placed on the sinterable top-side nanostructure NS1 of the connecting element VE via its sinterable bottom-side US. This forms a layered structure consisting of the substrate ST, sintering paste SP, power semiconductor element LE, connecting element VE, and bonding element BE, loosely stacked together.
[0059] Subsequently, the following sintered connections are formed simultaneously in the same sintering process: - A sintered connection is formed between the bottom contact surface KF3 of the power semiconductor element LE and the contact surface KF0 of the substrate ST using sintering paste SP; - A sintered connection is formed between the top contact surface KF1 of the power semiconductor element LE and the connecting element VE via the bottom nanostructure NS1 of the connecting element VE; and - A sintered connection is formed between the bottom side US of the bonding element BE and the connecting element VE through the top side nanostructure NS2 of the connecting element VE.
[0060] The common sintering process is carried out under pressure on the entire layered structure and at a temperature exceeding 200°C for a predetermined time. During this process, a (bilateral) diffusion process occurs between the rod-like or hair-like protrusions VS of the two nanostructures NS1 and NS2 of the connecting element VE and the surfaces of the corresponding mating components (i.e., the sinterable bottom side US of the bonding element BE and the sinterable top side contact surface KF1 of the power semiconductor element LE). The temperature exceeding 200°C accelerates this diffusion process.
[0061] In subsequent bonding processes or one or more subsequent bonding steps, the two bonding connections BV1, BV2 are bonded or formed on the bondable top side OS of the bonding element BE or the bondable top side contact surface KF2 of the power semiconductor element LE.
Claims
1. A power module (LM), comprising: - Power semiconductor device (LE) with a sinterable top-side electrical contact surface (KF1); - A bonding element (BE) with a sinterable bottom side (US) and a bondable top side (OS) for forming a top-side bonded connection (BV1). - A dual-sided sinterable connector (VE) having a bottom-side sinterable nanostructure (NS1) and a top-side sinterable nanostructure (NS2), and is sintered with the top-side electrical contact surface (KF1) of a power semiconductor element (LE) through the bottom-side nanostructure (NS1), and with the bottom side (US) of a bonding element (BE) through the top-side nanostructure (NS2), thereby physically and electrically connecting the bonding element (BE) to the top-side electrical contact surface (KF1) of the power semiconductor element (LE).
2. The power module (LM) according to claim 1. Its features are: The connecting element (VE) has a plate-shaped intermediate portion (MT). Nanostructures are formed on its two opposite sides in a distributed manner, namely bottom side (NS1) and top side (NS2).
3. The power module (LM) according to claim 1 or 2. Its features are: The bottom (NS1) and / or top (NS2) nanostructures each have multiple sinterable rod-shaped protrusions (VS). Each protrusion (VS) extends outward from the midplane (ME) of the connecting element (VE).
4. The power module (LM) according to claim 3. Its features are: The diameter of the protrusion (VS) is less than 1 micrometer, or less than 750 nanometers, or less than 500 nanometers, or less than 300 nanometers, or about 100 nanometers.
5. The power module (LM) according to any of the preceding claims. Its features are: The connecting element (VE) is made of copper or a copper alloy and is formed as a single piece.
6. The power module (LM) according to any of the preceding claims. Its features are: The bonding element (BE) is made of copper or a copper alloy.
7. The power module (LM) according to any of the preceding claims. Its features are: The top-side bonding connection (BV1) is achieved via bonding wires or bonding tapes. The bonding wire or bonding band is made of copper or a copper alloy.
8. The power module (LM) according to any of the preceding claims. Its features are: The power semiconductor element (LE) is a Si semiconductor element, a SiC semiconductor element, or a GaN semiconductor element.
9. The power module (LM) according to any of the preceding claims further includes: - Substrate with sinterable electrical contact surface (KF0) (ST); - The power semiconductor element (LE) has a sinterable bottom-side electrical contact surface (KF3) and is sintered to the contact surface (KF0) of the substrate (ST) via the bottom-side electrical contact surface (KF3), and is physically and electrically connected to the contact surface (KF0) of the substrate (ST).
10. The power module (LM) according to any of the preceding claims. Its features are: The bonding element (BE) and the connecting element (VE) are formed as a single unit.
11. The power module (LM) according to any of the preceding claims. Its features are: The bonding element (BE) or its top side (OS) is metallized by a metal layer made of a metallic material. This metallic material is different from the matrix material of the bonding element (BE).
12. The power module (LM) according to any of the preceding claims. Its features are: The bonding element (BE) has several metal layers made of different metals or metal alloys. These metal layers are formed into a single unit.
13. An inverter, comprising: - Power module (LM) according to any of the preceding claims; - A drive circuit for operating the power module (LM), which is electrically connected to the power module (LM) via a control signal connection.
14. A method for manufacturing a power module (LM), comprising the following steps: - Provide substrates (ST) with sinterable electrical contact surfaces (KF0); - Apply sintering paste (SP) to the contact surface (KF0) of the substrate (ST); - A power semiconductor device (LE) having a sinterable top-side electrical contact surface (KF1) and a sinterable bottom-side electrical contact surface (KF3) is disposed on a substrate, wherein the power semiconductor device (LE) is placed on a sintering paste (SP) via its bottom-side electrical contact surface (KF3); - Provides a dual-sided sinterable connecting element (VE) having a bottom-side sinterable nanostructure (NS1) and a top-side sinterable nanostructure (NS1). - A connection element (VE) is arranged on a power semiconductor element (LE), wherein the connection element (VE) is placed on the top electrical contact surface (KF1) of the power semiconductor element (LE) via its bottom nanostructure (NS1); - Provide a bonding element (BE) with a sinterable bottom side (US) and a bondable top side (OS) for forming a top-side bonded connection (BV1). - A bonding element (BE) is arranged on a connecting element (VE), wherein the bonding element (BE) is placed on the top-side nanostructure (NS2) of the connecting element (VE) via its sinterable bottom side (US); - The bottom electrical contact surface (KF3) of the power semiconductor device (LE) is formed by a first sintering connection between the contact surface (KF0) of the substrate (ST) and the sintering paste (SP); - The top-side electrical contact surface (KF1) of the power semiconductor element (LE) is connected to the connecting element (VE) via a second sintering connection between the bottom-side nanostructure (NS1) and the connecting element (VE); - The bottom side (US) of the bonding element (BE) is connected to the connecting element (VE) via a third sintering connection through the top side nanostructure (NS2) of the connecting element (VE).
15. The method according to claim 14, Its features are: The first, second, and third sintering connections are completed in the same sintering process.