DE102011075565A1 - Circuit module with cooling by phase change material - Google Patents

Abstract

A circuit module 30 comprises an electrical circuit 32 with an electrical component 36 which is at least partially embedded in a phase change material 42.

Description

FIELD OF THE INVENTION

The invention relates to a circuit module, in particular a circuit module with semiconductor switches for an inverter for the electric drive of a vehicle, such as a car, truck or bus.

BACKGROUND OF THE INVENTION

In electrically powered vehicles, a DC power source is often used to power the electric drive of the vehicle. In the case of the electric motors usually used in this case, the direct current must be converted from an inverter to alternating current. Due to the generated in the circuit module of the inverter resistive heat, the electrical components of the circuit module sometimes very hot and must be cooled.

Especially with electrical components that are only temporarily under power, which is the case for example in a circuit module of an inverter, the resulting ohmic heat varies greatly and it can cause temperature peaks. To intercept short-term temperature peaks, a phase change material (PCM, phase change material), for example paraffin, can be used in the cooling of electrical components.

For example, is from the EP 1 416 534 B1 a circuit system with an integrated circuit and a heat sink is known in which a latent heat storage module is arranged with a phase change material between a substrate on which the integrated circuit is mounted, and the heat sink.

SUMMARY OF THE INVENTION

The object of the invention is to provide easily manufactured circuit modules that can be cooled particularly effectively with a phase change material.

This object is solved by the subject matter of the independent claim. Further embodiments of the invention will become apparent from the dependent claims and from the following description.

A first aspect of the invention relates to a circuit module comprising an electrical circuit having at least one electrical component, a heat sink for dissipating heat from the electrical component, and a phase change material for latching electrical or resistive heat from the electrical component.

The electrical circuit may include an inverter for a vehicle or at least a part of this inverter.

An electrical component of an electrical circuit can be characterized in that it is at least temporarily traversed by electricity. However, an electrical component may also include a plastic substrate for the current carrying components, such as a plastic body into which an integrated circuit is typically molded. Furthermore, it is possible for the electrical component to generate electrical heat or electrical heat on its own by flowing through the current. But it is also possible that the electrical component is heated by being thermally in communication with other electrical components that generate this heat. In particular, conductor tracks which are made of copper may be such electrical components, since copper, in addition to its good conductivity for electricity is also a good conductor of heat, which dissipates the heat generated in the semiconductor devices connected to the conductor tracks from these.

The electrical component may comprise at least one semiconductor device, such as a diode, a transistor, a thyristor, an IGBT or an integrated circuit and / or a plurality of interconnects. It should be understood that the above-mentioned semiconductor devices designed to be used in the high voltage region of, for example, more than 100 V (for example, 400 V) or more than 10 A, develop particularly high Ohmic heat and therefore may require a particularly effective cooling. However, it is also possible to cool electrical components in the low-voltage range of less than 50 V, for example 42 V, with the arrangements described below.

A phase change material is generally a material that is capable of changing its phase state upon the absorption of heat or the release of heat. For example, the material may melt during the absorption of heat, that is to pass from the solid to the liquid state, or solidify in the release of heat, so pass from the liquid to the solid state. Although a phase change material releases heat or absorbs heat during phase transition, its temperature does not change until the phase transition is complete. In this way, a phase change material can be used to buffer heat without its Temperature increased or decreased. It is to be understood that the phase change material may be selected such that its phase transition occurs at a temperature in which the temperature of the components to be cooled also moves. In other words, the phase transition temperature of the phase change material may be selected such that the phase change material undergoes a phase transition at the temperature changes occurring in the circuit module.

Especially with components of power electronics, such as the electrical components of an inverter, short-term temperature peaks can be intercepted with a phase change material. For example, the temperature peaks can occur due to transient currents flowing through the components. Due to the compact design of the components or their size, the thermal mass can be so small that even during a short energizing the temperature rises sharply and then drops sharply again. Frequent high-frequency temperature fluctuations, however, can reduce the life of electrical components. For example, in a circuit module of an inverter cracks in a bonding point (solder joint) can be formed into a circuit board. A phase change material, which is in thermal connection with the electrical components of the electrical circuit, can mitigate or reduce the temperature fluctuations.

According to one embodiment of the invention, the electrical component is at least partially embedded in the phase change material. For example, an electrical component may then be embedded in a phase change material if it is in direct contact with the phase change material on several sides. For example, the electrical component may be at least partially immersed in the phase change material in the liquid phase. It is also possible that the electrical component is at least partially, but also possibly completely surrounded by the phase change material and is in direct thermal contact with the phase change material. A direct thermal contact is to be distinguished from an indirect thermal contact, which can be produced by a transmission body arranged between the electrical component and the phase change material. In other words, in a direct thermal contact no heat transfer body between the electrical component and the phase change material is arranged.

Due to the fact that the electrical component is embedded in the phase change material, the phase change material is brought into thermal contact with the location of the circuit module to be cooled, that is the electrical component, in a localized manner. This can result in a particularly effective heat transfer between the electrical component and the phase change material. The buffering of the electrical heat from the electrical component can be carried out particularly efficiently. In this way, the life of the electronics or the electronic circuit, in particular in an inverter and in particular also in power electronics, can be increased.

According to one embodiment of the invention, the electrical component is completely embedded in the phase change material. In this case, the electrical component may be enclosed on all sides by the phase change material and may thus be in contact with the phase change material on all its outer surfaces, resulting in a very good heat transfer between the electrical component and the phase change material.

According to one embodiment of the invention, the electrical component is arranged in a housing which is at least partially filled with the phase change material. For example, the entire electrical circuit or a circuit board with the electrical circuit can be located in the housing.

At the bottom of the housing and the heat sink of the circuit module can be mounted. Thus, the electrical heat from the electrical component in the phase change material can be temporarily stored in the housing and transmitted from the housing to the heat sink. For example, a heat sink may comprise a device of a good thermal conductivity material, such as metal, configured to transfer heat to another cooling medium. For this purpose, the heat sink, for example, comprise cooling fins, which are flowed around by a coolant, such as air or water.

For example, it is possible for the housing, which is filled with the phase change material, to completely surround the electrical component. In other words, the housing can prevent an exchange of media in its interior with the environment of the housing.

Since in many circuit modules and in particular in circuit modules for an inverter for a vehicle often already a housing for shielding the electrical components of the circuit module is present, by the at least partially filling the housing with a phase change material a manufacturing technology easy to implement execution of a buffer for heat to be provided.

According to one embodiment of the invention, the housing comprises a material which is designed to compensate for an expansion of the phase change material during the phase transition. For example, the housing may comprise a flexible membrane or be partially filled with a compressible medium. For example, a space filled with a gas can be present in the housing, the gas being compressed when the phase change material in the housing expands.

According to one embodiment of the invention, the housing comprises at least one capillary hole. The capillary hole may allow expansion and shrinkage of the phase change material by balancing the interior of the housing with the environment, thereby preventing outflow of molten phase change material by selecting the opening size of the capillary so that flow out due to capillary forces is not possible ,

According to one embodiment of the invention, the housing comprises a phase material-impregnated sponge. A sponge may be a mechanically rigid or mechanically flexible material that comprises so many chambers, so that a large part of the space occupied by the sponge is filled by phase change material when it is absorbed into the chambers of the sponge. A sponge may comprise any porous, elastic and / or compressible material. A sponge can prevent liquid phase change material from leaking out of the housing as the liquid phase change material is held in the tissue or chambers of the sponge by capillary forces.

According to one embodiment of the invention, the phase change material comprises paraffin. However, other materials may be used for storage and release of latent heat, that is, heat absorbed in a phase transition, such as inorganic salts or salt mixtures. The selection of the paraffin or the paraffin mixture may depend on the temperature level which is to be set in the electrical component or in the electrical circuit of the circuit module as the average temperature. Such a temperature may be, for example, 150 ° C.

According to one embodiment of the invention, the electrical component is embedded in a printed circuit board or board, are incorporated in the body of phase change material. For example, phase-change material beads, ie phase-change material encapsulated in plastic, can already be cast during the production of the printed circuit board, which is cast, for example, from plastic. In particular, when there are so many bodies of phase change material in the circuit board that the electrical component is touched at a plurality of locations of its surface almost directly from the bodies of phase change material, the electrical component is embedded in the phase change material in the bodies.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

The 1 shows a diagram with the temperature profile of a conventional electrical component.

2 shows the temperature profile of an electrical component in a circuit module according to an embodiment of the invention.

3 schematically shows the cross section through a circuit module according to an embodiment of the invention.

4 schematically shows a cross section through a circuit module according to another embodiment of the invention.

5 schematically shows a cross section through a circuit module according to another embodiment of the invention.

6 schematically shows a cross section through a circuit module according to another embodiment of the invention.

7 schematically shows a cross section through a circuit module according to another embodiment of the invention.

Basically, identical or similar parts are provided with the same reference numerals.

DETAILED DESCRIPTION OF EMBODIMENTS

1 shows a diagram in which a temperature profile 10 the temperature T is plotted over the time t. The curve 10 is the temperature profile of an electrical component of a circuit module of an inverter for supplying an electric vehicle drive.

Like from the 1 can be seen, the temperature varies 10 in the short term 12 over a range of about 60 ° C. The temperature fluctuations can be even more than 60 ° C for a short time (see section 14 ) and can also have a maximum temperature 16 temporarily exceed 150 ° C (see area 18 ). Exceeding the temperature profile 10 in the area 18 about the maximum temperature 16 and also short-term temperature fluctuations of more than 60 ° C in the range 14 can lead to a reduction in the lifetime of a circuit module, for example by cracks occurring at bonding sites.

In the 1 is still the area 20 the vehicle ambient temperature shown.

The 2 shows a diagram analogous to the diagram of 1 in which the temperature profile 10 ' an electrical component of an inverter which is in direct contact with a phase change material and which is embedded in the phase change material. Like from the 2 is apparent, is the short-term means of temperature fluctuations 12 ' much lower and is about 20 ° C. Due to the lower temperature fluctuations 12 ' can also reduce the entire temperature level of the circuit module, since temperature peaks analogous to the range 18 from the 1 no longer occur. From the 2 it can be seen that the maximum temperature 16 , in which the electrical components of a circuit module can be damaged, is far from being reached. Thus, the life of a circuit module can be increased and its damage can be reduced by means of a phase change material.

The 3 shows a circuit module 30 a high-voltage inverter, which is operated with 400 V, for example. The circuit module 30 includes an electrical circuit 32 that have electrical leads 34 can be connected to other circuit modules. The electrical circuit 32 includes a plurality of electronic components 36 , in this case IGBTs 36 on a circuit board 38 are arranged. The electrical circuit 32 is located in a housing 40 in which the board 38 and the two components 36 are arranged.

The housing 40 is partially with a phase change material 42 filled. There is so much phase change material 42 in the case 40 present that the components 36 at least partially in the phase change material 42 are embedded. When in the 3 illustrated embodiment, the two components 36 completely of phase change material 42 surround.

Temperature peaks on electronic components 36 may be due to a temporary storage in the electronic component 36 resulting heat in the phase change material 42 be intercepted. Thereby give the electronic components 36 the resulting ohmic heat to the phase change material 42 from, wherein the heat for melting the phase change material 42 is used. The heat therefore goes from reaching the melting point of the phase change material 42 not in a temperature increase. Only from the time when the phase change material 42 is completely melted, the temperature continues to rise. Conversely, when the phase change material solidifies, it decreases 42 , So when it cools, the temperature does not decrease until the phase change material 42 is completely frozen.

That in the 3 illustrated housing 40 is partially filled with air, so includes an air-filled space 44 , The air is used to determine the thermal expansion of the phase change material 42 compensate. In addition, the housing includes 40 on its top a capillary hole 46 or a capillary hole 46 , The capillary bore 46 allows expansion and shrinkage of the phase change material 42 an air balance to the environment, wherein an outflow of the molten phase change material 42 because of the small opening 46 capillary technology is prevented. On the capillary hole 46 However, can be dispensed with, in which case the proportion of air 44 at an extension of the phase change material 42 in the case 40 is compressed.

The housing 40 of the circuit module 30 and the board 38 are with a heat sink 48 at the bottom of the circuit module 30 connected. The heat sink 48 includes cooling fins 50 , which can be flowed around by a fluid such as air or water to the entire circuit module 30 to cool.

In the 4 is a cross section through a circuit module 30 essentially the same as the circuit module 30 from the 3 is constructed. The circuit module 30 from the 4 is different from the one from the 3 in that the housing 40 completely with phase change material 42 filled, the phase change material 42 the electrical circuit 32 so completely surrounds. The housing 40 does not have a capillary hole 46 on. However, the housing includes 40 from the 4 a flexible membrane 52 at the top of the case 40 is arranged. The flexible membrane 52 serves to equalize the thermal expansion of the phase change material 42 ,

The 5 shows a longitudinal section through a further embodiment of a circuit module 30 , similar to the circuit modules 30 from the 3 and 4 is constructed. As with the 4 , is at the circuit module 30 of the 5 the phase change material 42 from the case 40 completely enclosed. It is in the case 40 A sponge 54 arranged with the phase change material 42 is soaked. The sponge 54 may comprise a porous, elastic and compressible material, which may also be configured to thermal expansions of the phase change material 42 compensate.

The 6 shows a further embodiment of a circuit module 30 in which a circuit board 46 on a heat sink 48 is arranged. The electrical circuit 32 on the board 56 is arranged, this comprises conductor tracks 36 as electrical components 36 the electrical circuit 32 , The tracks 36 are at their base in a phase change material 42 embedded. The phase change material 42 is located in a chamber that passes through the board 56 and the heat sink 48 is formed and in which the conductor tracks 36 protrude. In particular, in a low-voltage version, for example with 42 V, an inverter, it is possible that not the semiconductor components of the circuit module are thermally critical, but the leading them to tracks 36 on the board 56 ,

The phase change material 42 can into the multilayer laminated board 56 be integrated. For example, as in the 6 shown in a lower layer of the board 56 a recess may be provided by a second layer of the board 56 is covered. The phase change material 42 can then be introduced into the recess of the lower layer, for example a laminate intermediate layer.

7 shows a further embodiment of a circuit module 30 in which electrical conductors 36 in a phase change material 42 are embedded. In the carrier material 58 the board 56 are small bodies 60 with phase change material 42 incorporated. In the carrier material 58 are so many bodies 60 present that every tracks 36 on their side surfaces and on their underside with a plurality of bodies 60 in thermal contact. For example, the carrier material 58 be prepared by that phase change material beads 60 in the still liquid carrier material 58 be mixed. The body 60 can be encapsulated in plastic phase change material 42 be used, for example, in house cleaning for thermal buffering between daytime and nighttime.

In addition, it should be noted that "encompassing" does not exclude other elements or steps, and "a" or "an" does not exclude a multitude. It should also be appreciated that features or steps described with reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limiting.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• EP 1416534 B1 [0004]

Claims (10)

Circuit module ( 30 ) comprising: an electrical circuit ( 32 ) with at least one electrical component ( 36 ), a heat sink ( 48 ) for the removal of heat from the electrical component ( 36 ), a phase change material ( 42 ) for temporarily storing electrical heat from the electrical component ( 42 ), characterized in that the electrical component ( 36 ) at least partially into the phase change material ( 42 ) is embedded. Circuit module ( 30 ) according to claim 1, wherein the electrical component ( 36 ) completely into the phase change material ( 42 ) is embedded. Circuit module ( 30 ) according to claim 1 or 2, wherein the electrical component ( 36 ) comprises a semiconductor device and / or a conductor track. Circuit module ( 30 ) according to one of the preceding claims, wherein the electrical component ( 36 ) in a housing ( 40 ) arranged at least partially with the phase change material ( 42 ) is filled. Circuit module ( 30 ) according to claim 4, wherein the housing ( 40 ) a material ( 44 . 54 ), which is adapted to an expansion of the phase change material ( 42 ). Circuit module ( 30 ) according to claim 4 or 5, wherein the housing ( 40 ) at least one capillary hole ( 46 ). Circuit module ( 30 ) according to one of claims 4 to 6, wherein the housing ( 40 ) at least one flexible membrane ( 52 ). Circuit module ( 30 ) according to one of claims 4 to 7, wherein the housing ( 40 ) one with phase change material ( 42 ) soaked sponge ( 54 ). Circuit module ( 30 ) according to any one of the preceding claims, wherein the phase change material ( 42 ) Paraffin comprises. Circuit module ( 30 ) according to one of the preceding claims, wherein the electrical component ( 36 ) in a printed circuit board ( 56 ) is embedded in the body ( 60 ) of phase change material ( 42 ) are incorporated.

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