Method for producing a unit comprising at least one power module and a heat sink through which coolant flows, and unit

Abstract

The invention relates to a method for producing a unit (1) comprising at least one power module (2) and a heat sink (3) through which coolant flows, wherein the heat sink (3) has a cooling pan (10) made of plastic and a cooling plate (9) made of metal, wherein the cooling pan (10) has elements (17) which project laterally beyond the cooling plate (9) or are passed through the cooling plate (9), wherein the cooling pan (10) consists of a thermoplastic material, wherein the elements (17) are softened by the action of heat and form a positive connection with the cooling plate (9), and to such a unit (1).

Description

[0001] The invention relates to a method for producing a unit comprising at least one power module and a heat sink through which coolant flows, as well as to such a unit.

[0002] Power modules comprise a substrate on which at least one power semiconductor is arranged. The power semiconductor heats up during operation due to waste heat. Various options are known for dissipating this waste heat. One option is to combine the power module with a heat sink through which coolant flows, forming a single unit. The coolant is preferably water. The heat sink consists, for example, of a cooler tray and a cooler plate, which together form the closed heat sink. It is also known to screw the cooler plate to the cooler tray, with additional seals being used. The cooler tray and cooler plate are typically made of metal. The screw connection can compensate for the coolant pressures that occur. The disadvantage of screw connections is that they are relatively expensive and require space for screw holes.

[0003] The invention is based on the technical problem of providing a method for manufacturing a unit comprising at least one power module and a heat sink through which coolant flows, enabling a compact design and generating less mechanical stress. A further technical problem is the creation of a corresponding unit comprising the power module and heat sink.

[0004] The solution to the technical problem results from a method having the features of claim 1 and a unit having the features of claim 10. Further advantageous embodiments of the invention result from the subclaims.

[0005] A method is proposed for producing a unit comprising at least one power module and a heat sink through which coolant flows, wherein the heat sink has a plastic heat sink and a metal heat sink plate. The heat sink plate has elements that project laterally beyond the heat sink plate or are passed through the heat sink plate. The heat sink plate is made of a thermoplastic material, with the elements being softened by the action of heat and forming a form-fitting connection with the heat sink plate. This allows the creation of a very compact unit, since the spatial requirements for the elements are very small or, in the case of passed-through elements, virtually zero. The additional effort then only consists in incorporating corresponding through-openings (perforations) into the heat sink plate. The mechanical stress is also reduced.The heatsink plate is preferably made of aluminum or copper, with copper having higher thermal conductivity, while aluminum is lighter and more cost-effective. The thermoplastic should preferably be highly rigid and resistant to the coolant (preferably water). A suitable plastic is PPS GF30, for example. The heatsink plate can be bonded to the power module before forming or integrated into the power module's manufacturing process.

[0006] Preferably, additional mechanical force is applied to the softened elements to further increase the strength of the connection. The resulting connections can then also be referred to as hot rivet heads or hot rivet seams.

[0007] There are now various ways to generate this combination of heat and mechanical power.

[0008] In one embodiment, the elements are hot-stitched using at least one thermode. The hot thermode is pressed against the elements, so that heat and force are applied simultaneously.

[0009] In an alternative embodiment, the elements are softened by means of hot air or infrared radiation and then pressed by means of at least one stamp.

[0010] In a further embodiment, the positive connection is produced by an ultrasonic friction welding process.

[0011] In a further embodiment, seals are arranged between the radiator plate and the radiator pan, which are designed, for example, as separate O-rings.

[0012] In an alternative embodiment, the seals are injection-molded onto the radiator pan, for example using a 2-component injection molding process.

[0013] In a further embodiment, the elements are completely circumferential.

[0014] In a further embodiment, the radiator plate has ribs which, when assembled, form cooling channels together with the radiator pan, which improves the transport of the coolant.

[0015] The unit consists of at least one power module and a heat sink through which a coolant flows. The heat sink has a plastic heat sink and a metal heat sink plate. The heat sink plate is made of a thermoplastic material, and the connection between the heat sink plate and the heat sink plate is formed by a positive connection of thermally formed elements of the heat sink plate. Regarding further possible embodiments, reference is made in full to the preceding explanations.

[0016] The power module is preferably a pulse inverter or part of a pulse inverter.

[0017] The invention is explained in more detail below using preferred embodiments. The figures show: Fig. 1a a unit before thermal forming of the elements, Fig. 1b the unit after thermal forming of the elements, Fig. 2a another unit before thermal forming of the elements, Fig. 2b the further unit after thermal forming of the elements and Fig. 3 a unit with screw connection (state of the art).

[0018] Before the invention is explained in more detail, the state of the art will first be discussed with reference to Fig. 3 will be explained in more detail. Fig. 3 schematically shows a unit 1 in cross-section, which consists of a power module 2 and a heat sink 3 through which a coolant flows. The power module 1 has a plurality of power semiconductors 4, which are connected to a metallization layer 6 on a substrate 7 via a connecting layer 5. The connecting layer 5 is, for example, a sintered or solder layer. The substrate 7 is preferably a ceramic, which consists, for example, of aluminum nitride (AIN) or silicon nitride. A further metal layer 8 is arranged on the underside of the substrate 7. The heat sink 3 has a cooler plate 9 and a cooler tray 10. The cooler plate 9 and the cooler tray 10 are connected to one another via a clamping device 11 and screw connections 12, wherein the clamping device 11 is designed, for example, as a frame.A seal 13 is arranged laterally between the cooler plate 9 and the cooler tray 10, which is pressed by the screw connection 12 so that no coolant can escape from the heat sink 3. The cooler plate 9 has ribs 14, which, together with the base of the cooler tray 10, form coolant channels 15. The power module 2 and the heat sink 3 are mechanically and thermally coupled or connected by a solder layer 16.

[0019] In the Fig. 1a shows a unit 1 according to the invention before assembly in cross section, wherein the same elements have the same reference numerals as in Fig. 3. The substrate 7 is connected directly to the cooler plate 9. The connection can be a soldered or sintered connection. Furthermore, the cooler tray 10 made of plastic has elements 17 that project laterally beyond the cooler plate 9. These elements 17 can also be referred to as springs or lips. The elements 17 are preferably designed such that they encompass the cooler plate 9 over its entire circumference. It is also shown that two circumferential seals 13 are arranged between the cooler plate 9 and the cooler tray 10. Furthermore, a molding compound 18 is shown, by means of which the power module 2 is protected from external influences. Thermodes 19 are shown above the elements 17 and can be moved in the direction of the arrow. To seal the heat sink 3, the thermode 19 is heated to the glass transition temperature of the plastic and pressed against the elements 17 with a defined force.The thermode 19 is then moved away and the plastic is cooled. The result is shown in . Fig. 1b, where the elements 17 are thermally formed and now form a connecting seam 20, fluid-tightly connecting the radiator plate 9 and the radiator pan 10. It should be noted that this connecting seam 20 does not have to be completely circumferential. Alternatively, a probe can be used instead of a thermode 19 to thermally form the elements 17 by means of ultrasonic friction welding.

[0020] Alternatively, the elements 17 can be softened by hot air or infrared radiation, wherein the contact pressure is then applied by means of a stamp so that the elements 17 are formed into the connecting seam 20.

[0021] In Fig. 2a and Fig. 2b shows an alternative embodiment. The only difference to the embodiment according to Fig. 1a and Fig.1b is that the elements 17 are designed as pins 21 which extend through openings in the cooler plate 9, wherein then by thermal forming by means of thermode 19, sonode or stamp with hot air or infrared radiation hot rivet heads 22 are formed in order to again form a positive connection between the cooler plate 9 and the cooler pan 10. List of reference symbols 1 unit 2 power module 3 heat sinks 4 power semiconductors 5 Connection layer 6 Metallization layer 7 Substrat 8 metal layer 9 Radiator plate 10 Radiator pan 11 Clamping device 12 screw connection 13 Seal 14 rib 15 Coolant channel 16 solder layer 17 elements 18 molding compound 19 Thermode 20 connecting seam 21 pins 22 hot rivet heads

Claims

[1] Method for producing a unit (1) comprising at least one power module (2) and a heat sink (3) through which coolant flows, wherein the heat sink (3) has a cooling pan (10) made of plastic and a cooling plate (9) made of metal, wherein the cooling pan (10) has elements (17) which project laterally beyond the cooling plate (9) or are passed through the cooling plate (9), wherein the cooling pan (10) consists of a thermoplastic material, wherein the elements (17) are softened by the action of heat and form a positive connection with the cooling plate (9). [2] Method according to claim 1, characterized by that an additional mechanical force is applied to the softened elements (17). [3] Method according to claim 2, characterized by that the elements (17) are hot-stacked by means of at least one thermode (19). [4] Method according to claim 2, characterized bythat the elements (17) are softened by means of hot air or infrared radiation and then pressed by means of at least one stamp. [5] Method according to claim 2, characterized by that the positive connection is created by an ultrasonic friction welding process. [6] Method according to one of the preceding claims, characterized by that seals (13) are arranged between the radiator plate (9) and the radiator pan (10). [7] Method according to claim 6, characterized by that the seals (13) are injection-molded onto the radiator pan (10). [8] Method according to one of the preceding claims, characterized by that the elements (17) are completely circumferential. [9] Method according to one of the preceding claims, characterized by that the radiator plate (9) has ribs (14) which, in the assembled state, together with the radiator pan (10) form cooling channels (15). [10] Unit (1) consisting of at least one power module (2) and a heat sink (3) through which a coolant flows, wherein the heat sink (3) has a cooling pan (10) made of plastic and a cooling plate (9) made of metal, wherein the cooling pan (10) consists of a thermoplastic material, wherein the connection between the cooling plate (9) and the cooling pan (10) is formed by a positive connection of thermally formed elements (17) of the cooling pan (10).

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