Inverter, process and motor vehicle

Abstract

Inverter (10) comprising a power module (12) with one or more power semiconductors and a first cooler (14) and a second cooler (16), wherein the power module has a first connection region (18) and a second connection region (20), wherein the first connection region (18) and the second connection region (20) on the power module (12) lie opposite one another, wherein the first connection region (18) of the power module is connected to the first cooler (14) via a sintered connection (22), wherein the second connection region (20) of the power module is connected to the second cooler (16) via a soldered connection (24). In addition, a method for producing an inverter and a motor vehicle with such an inverter are explained.

Description

[0001] The invention relates to an inverter, a method for producing an inverter and a motor vehicle.

[0002] Inverters, also known as drive inverters, are used to operate electric vehicles, especially battery-powered ones. These convert direct current into alternating current to drive one or more electric motors. The inverter's power modules generate large amounts of heat during operation, which must be dissipated. Active liquid cooling systems are well known in the art. In particular, two-sided cooling enables effective heat dissipation and high power density. To ensure good thermal integration, sintered and soldered joints are used between the cooler and the power module, although these require high tolerances.

[0003] In known prior art applications, instead of such highly thermally conductive connections, thermal connections are made using thermal pads or thermal paste, which are applied to both sides of a power module. Their thermal conductivity is lower, but they can compensate for particularly large tolerances.

[0004] Accordingly, the task is to provide an inverter with a power module cooled on both sides, which has a high thermal conductivity towards the coolers and also enables sufficient tolerance compensation.

[0005] This object is achieved by an inverter according to claim 1. The inverter according to claim 1 comprises - a power module with one or more power semiconductors and - a first cooler and a second cooler, - wherein the power module has a first connection area and a second connection area, - wherein the first connection area and the second connection area on the power module are opposite each other, - wherein the first connection area of the power module is connected to the first cooler via a sintered connection, - wherein the second connection area of the power module is connected to the second cooler via a solder connection.

[0006] The inverter is preferably designed for use in a motor vehicle. In particular, the inverter is a drive inverter. The inverter is advantageously arranged between an electric motor and a battery. The inverter enables the extraction of energy from the battery to drive the electric motor and / or the supply of energy from the electric motor to the battery. In particular, the inverter is designed to convert a provided direct current into a single-phase or multi-phase alternating current, preferably three-phase.

[0007] The power semiconductors are arranged within a potting compound on the power module. The potting compound provides electrical insulation and shielding against dirt and environmental influences. The power module, and in particular its power semiconductors, control the current flowing through the inverter. Heat is generated in the power module, which is dissipated via the coolers.

[0008] The first cooler and the second cooler dissipate the heat generated in the power module. Advantageously, one or both of the coolers are designed as active liquid coolers. A cooling fluid, such as water or a water-glycol mixture, flows through a liquid cooler, absorbing and dissipating the heat generated in the power module.

[0009] The connection areas of the power module are preferably formed opposite one another on the power module. The connection areas are preferably formed from a highly thermally conductive material, such as copper. One connection area is preferably flush with the encapsulation or protrudes beyond the encapsulation.

[0010] The sintered joint provides particularly high thermal conductivity, while only allowing for small tolerances. The soldered joint, in contrast, provides slightly lower thermal conductivity, while allowing for larger tolerances. Both joints combined provide very high thermal conductivity to the respective coolers and also allow for sufficient tolerance compensation. Compared to known designs according to the state of the art, the thermal conductivity is significantly increased. This allows for better heat dissipation, higher power density, and a smaller installation space.

[0011] The above object is further achieved by a method according to claim 2. The method for producing an inverter, preferably an inverter according to claim 1 or one of the embodiments of this description, comprises the following steps S1 and S2 - Attaching the cooler to a connection area of the power module by creating a sintered connection - Attach the cooler to a connection area of the power module by creating a solder connection

[0012] Either step S1 or step S2 can be executed first.

[0013] Particularly advantageously, the establishment of the second connection is provided within a time window before the power module has cooled down by more than 30°C from a temperature during establishment of the first connection.

[0014] The first connection corresponds to the connection produced first in time, which can be either a sintered connection or a soldered connection according to step S1 or S2. The second connection represents the connection produced second. The cooling to 30°C refers to a reference temperature. The reference temperature can be the process temperature during step S1 or during step S2. Alternatively, the reference temperature can be the process temperature of the first connection produced or the lower process temperature of steps S1 and S2. By producing both connections in close succession, the thermal load on the power module is kept as low as possible. The process temperatures during production are significantly higher than during operation of the inverter and place a high load on the respective power module.In particular, this lower thermal load due to a single heating-up can significantly reduce the probability of delamination, i.e. detachment of the encapsulation from the electronic components of the power module.

[0015] The above object is further achieved by a motor vehicle according to claim 4. The motor vehicle comprises an inverter according to claim 1 or according to one of the embodiments of this description, or the motor vehicle comprises an inverter produced by a method according to claim 2 or 3 or according to one of the embodiments of this description.

[0016] The inverter and the method for manufacturing an inverter are explained in detail below using several examples. They show: Fig. 1 an inverter with power module and two coolers in a highly simplified representation; Fig. 2 a representation of the individual steps of the process for manufacturing an inverter.

[0017] In the Fig. 1 shows a schematic representation of an inverter 10. Such an inverter 10 is designed to drive an electric motor vehicle, in particular a battery-powered motor vehicle, and is also referred to as a drive inverter. The inverter 10 is arranged between an electric motor and a battery. The inverter 10 enables the extraction of energy from the battery to drive the electric motor and / or the supply of energy from the electric motor to the battery. In particular, the inverter is designed to convert a provided direct current into a single-phase or multi-phase alternating current, preferably three-phase.

[0018] The inverter 10 comprises a power module 12 as well as a first cooler 14 and a second cooler 16.

[0019] The power module 12 has at least one power semiconductor via which the current flow through the power module is controlled. The electrical components of the power module 12 are embedded in an electrically insulating potting compound. For thermal connection, the power module 12 has a first connection region 18 and a second connection region 20. The connection regions 18 and 20 are formed opposite one another on the power module 12. One connection region is formed, for example, from a highly thermally conductive material, such as copper. The connection region is preferably flush with the potting compound or protrudes above it. The first connection region 18 and the second connection region 20 are located opposite one another on the power module 12.

[0020] One or both of the coolers are designed as liquid coolers. A cooling liquid, for example, water or a water-glycol mixture, absorbs the heat and transports it away. The first cooler 14 is firmly connected to the power module 12 in the first connection area 18 via a sintered connection 22 with high thermal conductivity. The second cooler 16 is firmly connected to the power module 12 in the first connection area 20 via a soldered connection 24 with high thermal conductivity.

[0021] The sintered connection 22 is capable of compensating tolerances to a limited extent, but provides a highly thermally conductive connection. The soldered connection 24 enables greater tolerance compensation than the sintered connection 22. In contrast, the thermal conductivity of the soldered connection 24 is lower than that of the sintered connection 22, while still providing a highly thermally conductive connection. The combination of the two connection types enables advantages with regard to tolerance compensation in the overall inverter system, as well as a highly thermally conductive connection for dissipating the heat generated in the power module 12. In particular, the thermal conductivity is significantly higher than known solutions in the prior art, which rely on a thermal paste or thermal pad on one side for tolerance compensation.

[0022] Contrary to today's common efforts to keep the complexity of manufacturing systems as simple as possible and limit the number of joining processes to a minimum, implementing such a setup requires both a sintering system and a soldering system. However, this increased effort is justified by the fact that the two highly thermally conductive connections provide significantly improved heat dissipation compared to the state of the art. This enables both higher power density and a smaller installation space.

[0023] The individual steps of a process for producing such an inverter are described in the Fig.2. In a step S1, the power module 12 is firmly connected to the first cooler 14 by producing a sintered connection 22. In a second step S2, the power module 12 is firmly connected to the second cooler 16 by producing a soldered connection 24. Step S1 can occur both before and after step S2. According to a further optional step S3, steps S1 and S2 are carried out before a temperature cools by more than 30°C. The cooling here refers to a process temperature of step S1 or S2 during the production of the connection. In particular, the process temperature refers to the lower of the temperatures in steps S1 and S2. This keeps thermal stress on the power module to a minimum.In particular, only a single warm-up is necessary, which reduces the risk of delamination, i.e., the detachment of the encapsulation from the electrical components of the power module. However, this requires a rapid change between the two sintering and soldering systems. In particular, step S3 can be understood as meaning that a change of production systems takes place within a time window in which a maximum cooling of 30°C occurs. List of reference symbols 10 inverters 12 Power module 14 first cooler 16 second cooler 18 first connection area 20 second connection area 22 Sintered connection 24 Solder connection S1 Step 1 S2 Step 2 S3 Step 3

Claims

[1] Inverter (10), comprising - a power module (12) with one or more power semiconductors and - a first cooler (14) and a second cooler (16), - wherein the power module has a first connection area (18) and a second connection area (20), - wherein the first connection area (18) and the second connection area (20) on the power module (12) are opposite each other, - wherein the first connection region (18) of the power module is connected to the first cooler (14) via a sintered connection (22), - wherein the second connection region (20) of the power module is connected to the second cooler (16) via a solder connection (24). [2] A method for producing an inverter, preferably an inverter according to claim 1, comprising the steps - Attaching the cooler (14) to a connection area (18) of the power module (12) by producing a sintered connection (22) - Attaching the cooler (16) to a connection area (20) of the power module (12) by creating a solder connection (24) [3] Method according to claim 2, characterized by that the establishment of the second connection is provided within a time window before the power module (12) has cooled down by more than 30°C from a temperature during establishment of the first connection. [4] Motor vehicle comprising an inverter according to claim 1 or manufactured by a method according to claim 2 or 3.

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