Method for manufacturing heat sink having fins and peripheral sidewalls

Abstract

The invention relates to a method for manufacturing a heat sink (2) having fins (24) and peripheral side walls (26) by extrusion. In order to save costs, the following steps are proposed: providing (A) a female die (4) having a base surface (6) and a male die (8) having a pressure surface (10), the base surface (6) of the female die (4) having an opening (12), a peripheral recess (14) being formed on the pressure surface (10) of the male die (8); placing (B) a semi-finished product (20) made of a first metal material in the female die (4); detachably connecting (C) a material layer (22) made of a second metal material having a higher thermal conductivity than the first metal material to the pressure surface (10) of the male mold (8); contacting (D) the male mould (8) with the semi-finished product (20) inserted into the female mould (4) via the material layer (22); pressing (E) the first metal material of the semi-finished product (20) through the openings (12) of the female die (4) by means of the male die (8) in order to form fins (24) and into the peripheral grooves (14) of the male die (8) in order to form peripheral side walls (26), the material layer (22) being connected with the entire surface of the material layer to the first metal material of the semi-finished product (20), the heat sink (2) being formed by the pressing (E); removing (F) the male mold (8) from the material layer (22); and removing (G) the radiator (2) from the female die (4).

Description

Technical Field

[0001] The invention relates to a method for manufacturing a heat sink having fins and a peripheral side wall by extrusion.

[0002] The invention also relates to a heat sink for a semiconductor device, which is manufactured by such an extrusion process.

[0003] Furthermore, the invention relates to a semiconductor arrangement having at least one semiconductor element and a heat sink.

[0004] Furthermore, the invention relates to a power converter having at least one semiconductor device. Background Art

[0005] In such power converters, the semiconductor device is usually fixed to a heat sink. A power converter is understood, for example, as a rectifier, an inverter, a converter or a DC voltage converter. The semiconductor device is usually formed as an electronic module, which has a housing and is screwed to the heat sink via a solid metal base plate. In addition, the semiconductor device can be directly connected to the heat sink. The semiconductor device can include, but is not limited to, an insulated gate bipolar transistor (IGBT) and / or a metal oxide semiconductor field effect transistor (MOSFET).

[0006] Publication EP 3 933 913 A1 describes a power module having at least two power units, each of which comprises at least one power semiconductor and a substrate. In order to reduce the structural space required for the power module and improve heat dissipation, it is proposed that at least one power semiconductor conductor is respectively connected to the corresponding substrate, in particular in a materially bonded manner, wherein the substrates of at least two power semiconductor units are respectively directly connected to the surface of a common heat sink in a materially bonded manner.

[0007] In order to meet the high insulation requirements in such electronic modules, semiconductors and connecting means, such as bonding wires, are covered with a potting compound, which additionally prevents moisture penetration and component corrosion.

[0008] Publication WO 2021 / 058212 A1 describes a carrier for at least one electrical component. The carrier comprises a heat sink having a heat sink surface and two side walls protruding from the heat sink surface and opposite to each other, two sealing blocks arranged on the heat sink surface and spaced apart from each other, and a carrier structure for at least one electrical component arranged between the two sealing blocks on the heat sink surface, wherein the sealing blocks extend between the two side walls and abut against each of the two side walls. Summary of the invention

[0009] Against this background, it is an object of the present invention to provide a cost-effective method for producing a heat sink.

[0010] According to the present invention, the object is achieved by a method for manufacturing a heat sink having fins and peripheral side walls by extrusion, the method comprising the following steps: providing a female mold having a base surface and a male mold having a pressure surface, wherein the base surface of the female mold has an opening, wherein a peripheral groove is formed on the pressure surface of the male mold; placing a semi-finished product made of a first metal material into the female mold; connecting a material layer made of a second metal material to the pressure surface of the male mold in a detachable manner, the second metal material having a higher thermal conductivity than the first metal material; contacting the male mold with the semi-finished product placed in the female mold via the material layer; pressing the first metal material of the semi-finished product through the opening of the female mold to form fins and into the peripheral groove of the male mold to form peripheral side walls by means of the male mold, wherein the material layer is connected to the first metal material of the semi-finished product with the entire surface of the material layer, wherein the heat sink is formed by pressing; detaching the male mold from the material layer; and removing the heat sink from the female mold.

[0011] In addition, according to the present invention, the object is achieved by a heat sink for a semiconductor device, which is manufactured by such an extrusion process, and has: fins, which are manufactured by pressing a semi-finished product through an opening of a female mold with the help of a pressure surface of a male mold; a peripheral side wall, which is arranged on the side of the heat sink opposite to the fins and is manufactured by pressing the semi-finished product into a peripheral groove of the male mold; a flat surface within the peripheral side wall, which is formed by the pressure surface of the male mold and includes a material layer made of a second metal material.

[0012] Furthermore, the object is achieved according to the invention by a semiconductor arrangement having at least one semiconductor element and such a heat sink, wherein the semiconductor element is connected to the heat sink in an electrically insulating and thermally conductive manner.

[0013] Furthermore, according to the invention, the object is achieved by a power converter having at least one such semiconductor arrangement.

[0014] The advantages and preferred embodiments listed below with respect to the method can be transferred to the heat sink, the semiconductor device and the power converter.

[0015] The invention is based on the consideration that an improved cost position is achieved by manufacturing a heat sink with peripheral side walls, fins and heat diffusion surfaces by extrusion. The heat sink is manufactured with the aid of a semi-finished product made of a first metal material. For example, the first metal material is an aluminum alloy, in particular a forged aluminum alloy. The heat diffusion surface is manufactured with the aid of a material layer made of a second metal material, which has a higher thermal conductivity than the first metal material. The second metal material is, for example, copper or a copper alloy. For example, the material layer is designed as a copper sheet.

[0016] The extrusion process is performed with the aid of a female mold having a base surface and a male mold having a pressure surface. Depending on the desired shape of the heat sink, the base surface of the female mold can be designed in a rectangular (especially square) or elliptical (especially circular) shape and have an opening according to the desired shape of the heat sink. The opening can be designed, but not limited to, as a rectangle, especially a square, or an elliptical, especially a circle. A peripheral groove is formed on the pressure surface of the male mold, which groove is produced, for example, by means of a cutting method, especially by milling. The groove is formed, for example, as a stepped groove with a rectangular or trapezoidal contouring portion.

[0017] The material layer is connected to the pressure surface of the male mold in a releasable manner. The releasable connection can be carried out adhesively, for example, by means of a releasable adhesive. The releasable adhesive connection of the material layer advantageously prevents displacement during the pressing process. After the semi-finished product made of the first metal material is placed in the female mold, the male mold contacts the semi-finished product placed in the female mold via the material layer. Then, the first metal material of the semi-finished product is pressed through the opening of the female mold by means of the male mold to form fins and pressed into the peripheral groove of the male mold to form the peripheral side wall, wherein the material layer is connected to the first metal material of the semi-finished product with the entire surface of the material layer to form a heat diffusion surface. The heat sink is formed by a pressing process. The process is carried out, for example, by means of cup extrusion, in particular by means of cup forward extrusion. In another step, the male mold is detached from the material layer and the heat sink is removed from the female mold. After extrusion, no other steps are required, such as connecting the material layer to diffuse heat, so that costs can be saved even for a small number of pieces.

[0018] Another embodiment provides that after pressing, the fins are cut to length in the die, in particular flush. Directly after pressing, the fins can have different lengths and / or protrude irregularly from the opening of the die. By cutting, for example by means of sawing, milling and / or cutting equipment, the fins are shortened cost-effectively to a uniform final length.

[0019] Another embodiment provides that the material layer is detachably connected to the male mold so that the material layer is flush with the pressure surface of the male mold. With such an arrangement, a heat diffusion surface of maximum size can be produced cost-effectively.

[0020] Another embodiment provides that the material layer is connected to the first metal material in a material-fitting manner via a pressure welding connection. Such a connection can be produced robustly and cost-effectively. In addition, the thermal resistance between the second metal material and the first metal material of the material layer is reduced, in particular compared to a welding or sintering connection.

[0021] Another embodiment provides that the material layer is roughened on the side facing away from the pressure surface of the positive mold. Such a roughened surface can be produced cost-effectively and improves the interlocking between the second metal material and the first metal material of the material layer.

[0022] Another embodiment provides that the material layer is connected to the first metallic material via micro-interlocking. In particular, the roughened surface enables such a connection to be produced robustly and cost-effectively via micro-interlocking.

[0023] Another embodiment provides that the opening of the die is formed as an elongated hole, wherein the semi-finished first metal material is pressed through the elongated hole of the die to form the layered fins. The elongated hole can be formed in an angular or rounded shape. The layered fins can achieve optimal heat dissipation, especially in the case of a lateral cooling fluid flow.

[0024] Another embodiment provides that the dielectric material layer is connected in a detachable manner between the pressure surface of the male mold and the material layer made of the second metal material, wherein the dielectric material layer is non-detachably connected to the material layer during pressing. The dielectric material layer contains, for example, an organic insulator. The organic insulator can be filled with a ceramic material, such as aluminum oxide and / or aluminum nitride, but is not limited to it. The dielectric material layer is pressed cost-effectively and simply to the material layer by the pressure of the male mold.

[0025] Another embodiment provides that the female mold has an inner shell surface and the male mold has an outer shell surface, wherein the outer shell surface of the male mold moves flush and parallel to the inner shell surface of the female mold during pressing. This avoids post-processing of the heat sink, which saves additional costs.

[0026] Another embodiment provides that an aluminum alloy, in particular a wrought aluminum alloy, is used for the first metallic material. Such alloys have a particular ductility and enable the production of fins with a high length-to-pitch ratio, thereby increasing the cooling performance.

[0027] Another embodiment provides for the use of an aluminum alloy containing silicon in a weight fraction in the range of 0.1% to 1%, in particular in a range of 0.1% to 0.5%. The aluminum alloy can be, but is not limited to, EN AW 6060 (AlMgSi0.5). In the case of the production of the heat sink by extrusion, in particular compared to cast heat sinks, an aluminum alloy with such a low silicon fraction can be used that the thermal conductivity is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the drawings.

[0029] The accompanying drawings show:

[0030] Figure 1 A schematic three-dimensional cross-sectional view showing a method for manufacturing a heat sink;

[0031] Figure 2 A schematic three-dimensional cross-sectional view showing a further method step for producing a heat sink,

[0032] Figure 3 A schematic three-dimensional view of a heat sink with cylindrical fins is shown,

[0033] Figure 4 Schematic cross-sectional view showing further process steps for producing a heat sink,

[0034] Figure 5 shows a schematic cross-sectional view of a heat sink having a layer of dielectric material,

[0035] Figure 6 A schematic top view of a female mold having an opening formed as a rectangular elongated hole is shown,

[0036] Figure 7 A schematic top view of a negative mold having an opening formed as a rounded elongated hole,

[0037] Figure 8 A schematic three-dimensional view of a heat sink with layered fins is shown,

[0038] Fig. 9 A schematic cross-sectional view showing a semiconductor device having a heat sink, and

[0039] Fig.10 A schematic diagram of a power converter is shown.

[0040] The embodiments explained below are preferred embodiments of the present invention. In the embodiments, the components described in the embodiments are the individual features of the present invention that can be considered independently of each other, and the features also improve the present invention independently of each other and can also be considered as components of the present invention individually or in a combination different from the combination shown. In addition, the described embodiments can also be supplemented by other features of the already described features of the present invention.

[0041] The same reference numerals have the same meaning in different figures. DETAILED DESCRIPTION

[0042] Figure 1A schematic three-dimensional cross-sectional view of a method for manufacturing a heat sink 2 by extrusion is shown. The heat sink 2 is manufactured by a forward extrusion process, in particular by a cup forward extrusion process. The method includes providing a female mold 4 and a male mold 8, the female mold having a base surface 6, and the male mold having a pressure surface 10. The base surface 6 of the female mold 4 has, for example, a circular opening 12 for forming cylindrical cooling fins. A peripheral groove 14, in particular a stepped groove, is formed on the pressure surface 10 of the male mold 8. In addition, the female mold 4 has an inner shell surface 16, and the male mold 8 has an outer shell surface 18, wherein the size of the outer shell surface 18 of the male mold 8 is designed so that the outer shell surface can be moved parallel to the inner shell surface 16 of the female mold 4. In addition, a semi-finished product 20 is made of a first metal material and a material layer 22 is made of a second metal material. The second metal material has a higher thermal conductivity than the first metal material. For example, the first metal material is an aluminum alloy, in particular a forged aluminum alloy, which has a weight content of less than 1%, in particular less than 0.5% of silicon. The first metal material can be, but is not limited to, EN AW 6060 (AlMgSi0.5). The second metal material is, for example, copper or a copper alloy. For example, the material layer 22 is designed as a copper sheet.

[0043] In another step, a semi-finished product 20 made of a first metal material is placed in B the female mold 4. The semi-finished product 20 is designed, for example, in a rectangular parallelepiped shape and is adapted to the inner shell surface 16 of the female mold 4. In addition, a material layer 22 made of a second metal material is connected C to the pressure surface 10 of the male mold 8 in a releasable manner. The releasable connection can be established, for example, adhesively by means of a releasable adhesive. Alternatively, the material layer 22 can be connected to the semi-finished product 20 in a releasable manner. The releasable connection of the material layer 22 to the semi-finished product 20 can also include placing the material layer 22 on a particularly flat surface of the semi-finished product 20 of the rectangular parallelepiped. The releasable adhesive connection of the material layer 22 prevents displacement during the pressing process.

[0044] In another step, the positive mold 8 is brought into contact D with the semi-finished product 20 placed in the negative mold 4 via the material layer 22. In particular, the material layer 22 is brought into contact with the surface of the semi-finished product 20 of the cuboid shape with the entire surface of the material layer.

[0045] Then, the semi-finished product 20 is pressed E by means of the male die 8 to form the heat sink 2. The first metal material of the semi-finished product 20 is pressed through the opening 12 of the female die 4 to form the fins 24 and pressed into the peripheral groove 14 of the male die 6 to form the peripheral side wall 26. The material layer 22 is roughened on the side facing away from the pressure surface 10 of the male die 8. The roughened material layer 22 is connected to the first metal material via micro-interlocking with the entire surface of the material layer by means of the pressure generated by the pressing process. In addition or alternatively, the connection is made in a material-fitting manner by means of pressure welding.

[0046] Figure 2 A schematic three-dimensional cross-sectional view of another method step for producing a heat sink 2 is shown, which method step comprises releasing F the male mold 8 from the material layer 22 and removing F the heat sink 2 from the female mold 4. For the sake of clarity, Figure 2 The removal mechanism is not shown. Figure 2 Another embodiment of the method corresponds to Figure 1 Design solutions in .

[0047] Figure 3 A schematic three-dimensional view of a heat sink 2 with cylindrical fins 24 is shown. The material layer 22 contains copper and forms, for example, a rectangular flat contact surface 28 for contacting, in particular flat contacting, electronic components such as power semiconductors. The material layer 22 enables heat dissipation during operation of the electronic component. Figure 3 Another design scheme of the heat sink 2 corresponds to Figure 2 Design solutions in .

[0048] Figure 4 A schematic cross-sectional view shows further method steps for producing the heat sink 2. Figure 1 After the pressing E shown, the fins 24 are cut to a certain length H in the female mold 4. For example, the fins 24 are shortened to a uniform final length by means of a cutting mechanism 30. The cutting mechanism 30 can include a sawing device, a milling device and / or a cutting device. Then, the male mold 8 is separated from the material layer 22 F, and the heat sink 2 is removed G from the female mold 4 by a removal mechanism 32, which includes ejection pins 34 corresponding to the fins 24. Figure 4 Another embodiment of the method corresponds to Figure 1 Design solutions in .

[0049] Figure 5 A schematic cross-sectional view of a heat sink 2 is shown with a dielectric material layer 36, which contains, for example, an organic insulator. The organic insulator can be filled with, but is not limited to, a ceramic material, such as aluminum oxide and / or aluminum nitride. During the manufacture of the heat sink 2, the dielectric material layer 36 is connected in a detachable manner between the pressure surface 10 of the male mold 8 and the material layer 22. During pressing (E), the dielectric material layer 36 is then pressed against the material layer 22. In addition, the heat sink 2 has layered fins 24. Figure 3 Another design of the heat sink 2 corresponds to Figure 3 Design solutions in .

[0050] Figure 6 A schematic top view of a die 4 with openings 12 formed as rectangular slots 38 is shown. Laminated fins can be produced by means of such slots 38. The rectangular slots 38 are arranged extending in parallel and have the same spacing d. In order to achieve concentrated heat dissipation, in particular to avoid hot spots, the spacing d can be varied. Figure 6 Another embodiment of the opening 12 in the Figure 1 Design scheme in .

[0051] Figure 7 The schematic top view shows a negative mold 4 with an opening 12 formed as a rounded elongated hole 40. The opening 12 is designed as an elongated hole 40 with a semicircular rounding, for example. Figure 7 Another embodiment of the opening 12 in the Figure 6 Design scheme in .

[0052] Figure 8 1 shows a schematic three-dimensional view of a heat sink 2 having layered fins 24 which are arranged in parallel and have the same spacing d. In particular, the heat sink 2 uses a heat sink such as Figure 6 The cooling fluid flow K extends along the parallel layered fins 24. Figure 8 Another design of the heat sink 2 corresponds to Figure 3 Design scheme in .

[0053] Fig. 9 A schematic cross-sectional view of a semiconductor device 42 with a heat sink 2 is shown. The semiconductor device 42 includes, for example, a semiconductor element 44, which is formed as a vertical power transistor, in particular as an insulated gate bipolar transistor (IGBT). The IGBT is connected to a structured metallization 46 in a material-fitting manner, which is connected to the heat sink 2 in an electrically insulating and thermally conductive manner via a dielectric material layer 36. For example, the IGBT is connected to the metallization 46 on the collector side in a material-fitting manner. The material-fitting connection can be, but is not limited to, a welding connection and / or a sintering connection, and can also be an adhesive connection, for example, using an electrically conductive and thermally conductive adhesive for adhesive connection. In addition, the IGBT is connected to the metallization 46 on the gate side and the emitter side via a bonding connection 48, in particular via a bonding wire or a bonding tape. The semiconductor element 44 is completely encapsulated by a potting compound 50, wherein the potting compound 50 is bounded by the peripheral side wall 26 of the heat sink 2. The potting compound 50, for example, contains a soft potting compound, in particular a silicone potting compound. Fig. 9 Another design of the heat sink 2 corresponds to Figure 8 Design solutions in .

[0054] Fig.10 A schematic diagram of a power converter 52 is shown, which includes, for example, a semiconductor device 42 with a heat sink 2 . Fig.10 The semiconductor device 42 in Fig. 9 Formed as shown in .

[0055] In summary, the present invention relates to a method for manufacturing a heat sink 2 having fins 24 and a peripheral side wall 26 by extrusion. In order to save costs, the following steps are proposed: providing A a female mold 4 having a base surface 6 and a male mold 8 having a pressure surface 10, wherein the base surface 6 of the female mold 4 has an opening 12, wherein a peripheral groove 14 is formed on the pressure surface 10 of the male mold 8; placing a semi-finished product 20 made of a first metal material into B the female mold 4; connecting C a material layer 22 made of a second metal material to the pressure surface 10 of the male mold 8 in a detachable manner, the second metal material having a higher thermal conductivity than the first metal material; contacting D the male mold 8 with the semi-finished product 20 placed in the female mold 4 via the material layer 22; pressing E the first metal material of the semi-finished product 20 through the opening 12 of the female mold 4 to form a fin 24 and pressing into the peripheral groove 14 of the male mold 8 to form a peripheral side wall 26 by means of the male mold 8, wherein the material layer 22 is connected to the first metal material of the semi-finished product 20 with the entire surface of the material layer, wherein the heat sink 2 is formed by pressing E; releasing F the male mold 8 from the material layer 22; removing G the heat sink 2 from the female mold 4.

Claims

1. A method for manufacturing a heat sink (2) by extrusion, the heat sink having fins (24) and a peripheral side wall (26), the method comprising the following steps: - providing (A) a female mold (4) having a base surface (6) and a male mold (8) having a pressure surface (10), wherein the base surface (6) of the female mold (4) has an opening (12), wherein a peripheral groove (14) is formed on the pressure surface (10) of the male mold (8); - placing (B) a semi-finished product (20) made of a first metal material into the female mold (4); - releasably connecting (C) a material layer (22) made of a second metal material having a higher thermal conductivity than the first metal material to the pressure surface (10) of the male mold (8); - bringing the male mold (8) into contact (D) with the semi-finished product (20) placed in the female mold (4) via the material layer (22); - by means of the male die (8), the first metal material of the semi-finished product (20) is pressed (E) through the opening (12) of the female die (4) to form the fins (24), and the first metal material of the semi-finished product is pressed into the peripheral groove (14) of the male die (8) to form the peripheral side wall (26), wherein the material layer (22) is connected to the first metal material of the semi-finished product (20) over the entire surface of the material layer, wherein the heat sink (2) is formed by the pressing (E); - releasing (F) the male mold (8) from the material layer (22); - Remove (G) the heat sink (2) from the female mold (4).

2. The method according to claim 1, wherein: After the pressing (E), the fins (24) are cut to length (H), in particular cut flush to length, in the die (4).

3. The method according to any one of claims 1 or 2, wherein: The material layer (22) is detachably connected to the male mold (8), so that the material layer (22) is flush with the pressure surface (10) of the male mold (8).

4. A method according to any one of the preceding claims, wherein: The material layer (22) is connected to the first metal material in a materially bonded manner via a pressure welding connection.

5. A method according to any one of the preceding claims, wherein: The material layer (22) is roughened on the side facing away from the pressure surface (10) of the male mold (8).

6. The method according to claim 5, wherein: The material layer (22) is connected to the first metal material via micro-interlocking.

7. A method according to any one of the preceding claims, wherein: The opening (12) of the die (4) is provided as a long hole (38, 40), wherein the first metal material of the semi-finished product (20) is pressed through the long hole (38, 40) of the die (4) to form a layered fin (24).

8. A method according to any one of the preceding claims, wherein: A dielectric material layer (36) is releasably connected between the pressure surface (10) of the male mold (8) and the material layer (22) made of the second metal material, wherein the dielectric material layer (36) is non-releasably connected to the material layer (22) during the pressing (E).

9. A method according to any one of the preceding claims, wherein: The female mold (4) has an inner shell surface (16) and the male mold (8) has an outer shell surface (18), wherein the outer shell surface (18) of the male mold (8) moves during the pressing (E) in a flush and parallel manner relative to the inner shell surface (16) of the female mold (4).

10. A method according to any one of the preceding claims, wherein: An aluminum alloy, in particular a wrought aluminum alloy, is used as the first metal material.

11. The method according to claim 10, wherein: Aluminum alloys are used which contain silicon in a proportion by weight in the range of 0.1% to 1%, in particular in the range of 0.1% to 0.5%.

12. A heat sink (2) for a semiconductor device (42), manufactured by an extrusion process according to any one of the preceding claims, the heat sink having: - a fin (24) produced by pressing (E) the semi-finished product (20) through the opening (12) of the female die (4) by means of the pressure surface (10) of the male die (8), - a peripheral side wall (26) which is arranged on the side of the heat sink (2) opposite the fins (24) and is produced by pressing (E) the semi-finished product (20) into the peripheral groove (14) of the male mold (8), - a flat surface inside the peripheral side wall (26), which is formed by the pressure surface (10) of the male mold (8) and which forms a material layer (22) made of a second metallic material.

13. A semiconductor device (42) comprising at least one semiconductor element (44) and a heat sink (2) according to claim 12, wherein: The semiconductor element (44) is connected to the heat sink (2) in an electrically insulating and thermally conductive manner.

14. The semiconductor device (42) according to claim 13, wherein: At least one of the semiconductor elements (44) is encapsulated by a potting compound (50), wherein the potting compound (50) is bounded by the peripheral side wall (26) of the heat sink (2).

15. A power converter (52) having at least one semiconductor device (42) according to any one of claims 13 or 14.

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