Bonding method, method for manufacturing semiconductor device, and semiconductor device

Abstract

This bonding method comprises a step for providing an aluminum member and a clad material. The aluminum member includes a first surface. The constituent material of the aluminum member is an aluminum alloy containing magnesium. The clad material includes a second surface. The clad material includes a core material and a brazing material disposed on the core material. The brazing material forms the second surface. The constituent material of the brazing material is an aluminum alloy containing silicon. The bonding method according to the present disclosure further comprises a step for disposing the aluminum member and the cladding material with the first surface facing the second surface, and a step for melting the brazing material with the aluminum member pressurized toward the cladding material.

Description

Bonding method, semiconductor device manufacturing method, and semiconductor device

[0001] The present disclosure relates to a bonding method, a method for manufacturing a semiconductor device, and a semiconductor device.

[0002] For example, Japanese Patent Publication No. 59-48714 (Patent Document 1) describes a method for joining aluminum members. In the method for joining aluminum members described in Patent Document 1, first, a first aluminum member and a second aluminum member are prepared. Second, an insert material is interposed between the first aluminum member and the second aluminum member. The insert material is a hypereutectic alloy of aluminum containing silicon. Third, the insert material is melted while the first aluminum member is pressed toward the second aluminum member (first-stage pressurization). Fourth, the first aluminum member is pressed toward the second aluminum member (second-stage pressurization), thereby extruding the molten insert material from between the first aluminum member and the second aluminum member. By performing these steps, the method for joining aluminum members described in Patent Document 1 joins the first aluminum alloy and the second aluminum alloy.

[0003] Special Publication No. 59-48714

[0004] When joining aluminum members by brazing, it has been considered essential to use a flux to remove the oxide film covering the surface of the aluminum member. However, when the aluminum member is made of an aluminum alloy containing magnesium, brazing is difficult even with the use of a flux because the effect of the flux is inhibited by the magnesium. In the joining method for aluminum members described in Patent Document 1, the production of an insert material is difficult and the material cost of the insert material is high. Furthermore, the joining method for aluminum members described in Patent Document 1 requires two-stage pressurization, which complicates the process. The present disclosure provides a joining method capable of brazing aluminum members containing magnesium without using a flux or a special insert material.

[0005] The joining method of the present disclosure includes the steps of preparing an aluminum member and a clad material. The aluminum member has a first surface. The aluminum member is made of an aluminum alloy containing magnesium. The clad material has a second surface. The clad material has a core material and a brazing filler metal disposed on the core material. The brazing filler metal forms the second surface. The brazing filler metal is made of an aluminum alloy containing silicon. The joining method of the present disclosure further includes the steps of arranging the aluminum member and the clad material so that the first surface faces the second surface, and melting the brazing filler metal while the aluminum member is pressed toward the clad material.

[0006] According to the joining method of the present disclosure, it is possible to braze aluminum members containing magnesium without using flux or special insert materials.

[0007] 1 is a process diagram of a joining method according to a first embodiment. A cross-sectional view of an aluminum member 10. A cross-sectional view of a clad material 20. A cross-sectional view illustrating a placement step S2. A cross-sectional view illustrating a joining step S3. A cross-sectional view of a joined body 100. A first cross-sectional view illustrating a joining mechanism in a joining method according to a first embodiment. A second cross-sectional view illustrating a joining mechanism in a joining method according to a first embodiment. A cross-sectional view of an aluminum member 10 used in a joining method according to a second embodiment. A cross-sectional view of an aluminum member 10 used in a joining method according to a third embodiment. A cross-sectional view of a clad material 20 used in a modified example of the joining method according to the third embodiment. A cross-sectional view illustrating a placement step S2 in a joining method according to a fourth embodiment. A first cross-sectional view illustrating a joining mechanism in a joining method according to a fourth embodiment. A second cross-sectional view illustrating a joining mechanism in a joining method according to a fourth embodiment. An optical microscope image of a joining interface between an aluminum member 10 and a clad material 20. A schematic diagram of a semiconductor device 200. A perspective view of a clad material 20 constituting a fin 212. A first schematic view illustrating a method for manufacturing a semiconductor device 200. A second schematic view illustrating a method for manufacturing a semiconductor device 200. 10A is a third schematic diagram showing the method for manufacturing the semiconductor device 200. FIG. 11A is a cross-sectional view of a fin 212 used in the semiconductor device 200A.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure will be described with reference to the accompanying drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated.

[0009] First Embodiment A joining method according to a first embodiment will be described.

[0010] 1 is a process diagram of a bonding method according to embodiment 1. As shown in FIG. 1, the bonding method according to embodiment 1 includes a preparation step S1, a placement step S2, and a bonding step S3. The placement step S2 is performed after the preparation step S1. The bonding step S3 is performed after the placement step S2.

[0011] <Configuration of aluminum member 10 and clad material 20> Figure 2 is a cross-sectional view of the aluminum member 10. As shown in Figure 2, the aluminum member 10 has a first surface 10a. The first surface 10a is, for example, an end surface in the thickness direction of the aluminum member 10. The constituent material of the aluminum member 10 is an aluminum alloy containing magnesium. The constituent material of the aluminum member 10 may also be an aluminum alloy containing magnesium and silicon. Specific examples of the constituent material of the aluminum member 10 include 5000 series aluminum alloys and 6000 series aluminum alloys. The first surface 10a is covered with an oxide film 31.

[0012] FIG. 3 is a cross-sectional view of the clad material 20. As shown in FIG. 3, the clad material 20 has a second surface 20a. The second surface 20a is, for example, an end surface of the clad material 20 in the thickness direction. The clad material 20 has a core material 21 and a brazing filler metal 22. The brazing filler metal 22 is disposed on the core material 21. The brazing filler metal 22 forms the second surface 20a. The core material 21 and the brazing filler metal 22 are integrated by rolling. In the example shown in FIG. 3, the brazing filler metal 22 is disposed on only one of both end surfaces of the core material 21, but the brazing filler metal 22 may be disposed on both end surfaces of the core material 21. The second surface 20a is covered with an oxide film 32.

[0013] The core material 21 is made of, for example, aluminum or an aluminum alloy. Specific examples of the material for the core material 21 include pure aluminum, 1000-series aluminum alloys, 3000-series aluminum alloys, and aluminum alloys containing 0.5 to 2 mass percent manganese, with the remainder being aluminum and unavoidable impurities.

[0014] The brazing filler metal 22 is an aluminum alloy containing silicon. The melting point of the brazing filler metal 22 is lower than the melting points of the materials constituting the aluminum member 10 and the core material 21. If the silicon concentration in the brazing filler metal 22 is too low, the melting point of the brazing filler metal 22 is not sufficiently lowered. On the other hand, if the silicon concentration in the brazing filler metal 22 is too high, the effect of lowering the melting point of the brazing filler metal 22 is small. If the silicon concentration in the brazing filler metal 22 is too high, the core material 21 becomes hard, making it difficult to manufacture the clad material 20. From this perspective, the silicon concentration in the brazing filler metal 22 is preferably 4 mass percent or more and 12 mass percent or less. The brazing filler metal 22 may contain bismuth and / or lithium in addition to silicon. By including bismuth and / or lithium in the brazing filler metal 22, the wettability of the brazing filler metal 22 can be improved.

[0015] The thickness of the brazing filler metal 22 is defined as thickness T. If thickness T is too small, the amount of brazing filler metal 22 that melts and flows during brazing will be insufficient, and the gap between the aluminum member 10 and the core material 21 will not be filled completely, which may result in a gap remaining between the aluminum member 10 and the core material 21. On the other hand, if thickness T is too large, excess brazing filler metal 22 may erode the core material 21. Furthermore, if thickness T is too large, excess brazing filler metal 22 may protrude from the side surfaces of the aluminum member 10 and the core material 21. From this perspective, thickness T is preferably 0.01 mm or more and 0.1 mm or less.

[0016] The brazing filler metal 22 that protrudes from the side surfaces of the aluminum member 10 and the core material 21 during brazing can be removed by cutting, etc. Corrosion of the core material 21 can be prevented by reducing the silicon concentration in the brazing filler metal 22 or by reducing the heating temperature during brazing.

[0017] <Details of the joining method according to the first embodiment> In the preparation step S1, the aluminum member 10 and the clad material 20 are prepared. The aluminum member 10 and the clad material 20 are preferably cleaned before being subjected to the placement step S2. This removes the oxide films 31 and 32 (or reduces the thickness of the oxide films 31 and 32). FIG. 4 is a cross-sectional view illustrating the placement step S2. As shown in FIG. 4, the aluminum member 10 and the clad material 20 are placed such that the first surface 10a faces the second surface 20a. At this time, no flux is supplied between the first surface 10a and the second surface 20a.

[0018] 5 is a cross-sectional view illustrating the joining step S3. As shown in FIG. 5, in the joining step S3, the aluminum member 10 is pressed toward the clad material 20. The pressure applied at this time is preferably, for example, 10 kPa or more. The above-mentioned pressure is applied using, for example, a jig. In the joining step S3, the aluminum member 10 and the clad material 20 are heated while the above-mentioned pressure is applied. This causes the brazing material 22 to melt.

[0019] The heating temperature is equal to or higher than the solidus temperature of the brazing filler metal 22. If the heating temperature is lower than the solidus temperature of the brazing filler metal 22, the brazing filler metal 22 will not melt, and brazing will not be performed. The heating temperature is preferably equal to or higher than the liquidus temperature of the brazing filler metal 22 in order to increase the fluidity of the molten brazing filler metal 22 and promote destruction of the oxide film 32. However, the heating temperature is lower than the solidus temperatures of the aluminum members 10 and the core material 21 (e.g., lower than 630°C) in order to prevent the aluminum members 10 and the core material 21 from melting. The heating is preferably terminated, for example, when the heating temperature reaches a temperature just above the liquidus temperature of the brazing filler metal 22. The heating temperature may be maintained for a certain period of time.

[0020] The joining step S3 is performed, for example, in a non-reduced inert atmosphere. The inert gas is, for example, nitrogen gas, argon gas, or the like. The oxygen concentration in the atmosphere is preferably less than 500 ppm to suppress oxidation of the aluminum member 10 and the brazing filler metal 22. When the heating is completed, the molten brazing filler metal 22 solidifies, completing the joining of the aluminum member 10 and the clad material 20, and forming the joined body 100.

[0021] Fig. 6 is a cross-sectional view of the joined body 100. As shown in Fig. 6, in the joined body 100, the aluminum member 10 and the core material 21 are joined by a joining layer 23. The joining layer 23 is formed by cooling and solidifying a molten brazing material 22. The joining layer 23 contains magnesium in addition to silicon. The magnesium in the joining layer 23 is diffused from the aluminum member 10. However, the amount of magnesium in the joining layer 23 is very small. The magnesium concentration in the entire joining layer 23 is, for example, less than 0.1 mass percent.

[0022] 7A is a first cross-sectional view showing the joining mechanism in the joining method according to embodiment 1. As shown in Fig. 7A, in the joining step S3, pressure is applied, causing local destruction of the oxide films 31 and 32 before the brazing filler metal 22 melts. The locally destroyed locations of the oxide films 31 and 32 are referred to as "destroyed locations."

[0023] 7B is a second cross-sectional view showing the joining mechanism in the joining method according to the first embodiment. As shown in FIG. 7B , in the joining step S3, when the temperature further increases and the brazing filler metal 22 melts, the molten brazing filler metal 22 comes into contact with the aluminum member 10 through the destruction site. Magnesium diffuses into the molten brazing filler metal 22 from the portion of the aluminum member 10 that comes into contact with the molten brazing filler metal 22. Magnesium is active in the molten brazing filler metal 22 and has a stronger bond with oxygen than aluminum. Therefore, magnesium removes oxygen from the oxide films 31 and 32, reducing and destroying the oxide films 31 and 32. Therefore, in the joining method according to the first embodiment, the molten brazing filler metal 22 comes into contact with the aluminum member 10 with the oxide films removed, thereby achieving good joining.

[0024] Generally, when brazing aluminum members, a flux is supplied between the brazing filler metal and the aluminum member to remove the oxide film present on the surface of the aluminum member, thereby achieving a bond. However, if the aluminum member contains magnesium, the magnesium inhibits the flux from removing the oxide film, making it difficult to achieve a bond even with the flux. In contrast, in the joining method according to the first embodiment, the oxide films 31 and 32 are removed by the mechanism described above, making it possible to achieve good brazing without the use of a flux.

[0025] When the aluminum member 10 is made of an aluminum alloy containing magnesium and silicon, the solidus temperature of the aluminum member 10 is lower than when the aluminum member 10 is made of an aluminum alloy containing magnesium. Therefore, when the temperature rises in the joining step S3, part of the base material of the aluminum member 10 melts and enters a solid-liquid coexistence state, making the oxide film 31 more susceptible to destruction and enabling better joining.

[0026] Embodiment 2 A joining method according to embodiment 2 will be described. Here, differences from the joining method according to embodiment 1 will be mainly described, and overlapping descriptions will not be repeated.

[0027] Fig. 8 is a cross-sectional view of an aluminum member 10 used in the joining method according to the second embodiment. The oxide film 31 is not shown in Fig. 8 . As shown in Fig. 8 , in the joining method according to the second embodiment, unevenness is formed on the first surface 10a. More specifically, the first surface 10a has protrusions 10b. The unevenness (protrusions 10b) on the first surface 10a is formed by, for example, subjecting the first surface 10a to cutting, grinding, sandblasting, or wet blasting.

[0028] As described above, in the joining step S3, the aluminum member 10 is pressed against the clad material 20 with the first surface 10a and the second surface 20a facing each other. If protrusions 10b are formed on the first surface 10a, the contact area between the tips of the protrusions 10b and the second surface 20a is extremely small, causing stress concentration at the contact points, and making the oxide films 31 and 32 prone to breakage at the contact points. Therefore, the joining method according to the second embodiment further promotes contact between the molten brazing filler metal 22 and the aluminum member 10, making it possible to achieve even better joining.

[0029] Although the example in which the first surface 10a has irregularities has been described above, irregularities may also be formed on the second surface 20a (the second surface 20a may have protrusions), or irregularities may be formed on both the first surface 10a and the second surface 20a. The height of the irregularities (the distance from the material surface to the apex of the protrusions) is, for example, 5 μm or more and less than the thickness of the brazing filler metal 22. For example, if the thickness of the brazing filler metal 22 is 20 μm, the height of the irregularities is preferably less than 20 μm.

[0030] Although the above description has been given of an example in which the shape of the protrusions 10b is triangular in cross section, the shape of the protrusions 10b is not limited as long as it is a shape that can induce stress concentration. The shape of the protrusions 10b in cross section may be, for example, an arc or a trapezoid.

[0031] Embodiment 3 A joining method according to embodiment 3 will be described. Here, differences from the joining method according to embodiment 1 will be mainly described, and overlapping descriptions will not be repeated.

[0032] Fig. 9A is a cross-sectional view of an aluminum member 10 used in the joining method according to the third embodiment. Note that the oxide film 31 is not shown in Fig. 9A. As shown in Fig. 9A, in the joining method according to the third embodiment, the aluminum member 10 has a protruding portion 10c. The protruding portion 10c protrudes from the first surface 10a. The protruding portion 10c is, for example, a burr or burr generated during press working to form a hole 10d in the aluminum member 10. In other words, the protruding portion 10c is located, for example, around the hole 10d.

[0033] As described above, in the joining step S3, the aluminum member 10 is pressed against the clad material 20 with the first surface 10a and the second surface 20a facing each other. If the aluminum member 10 has a protruding portion 10c, the contact area between the tip of the protruding portion 10c and the second surface 20a is extremely small, which causes stress concentration at the contact point, making the oxide films 31 and 32 prone to breakage at the contact point. Therefore, the joining method according to the third embodiment further promotes contact between the molten brazing filler metal 22 and the aluminum member 10, thereby achieving even better joining.

[0034] FIG. 9B is a cross-sectional view of a clad material 20 used in a modified example of the joining method according to the third embodiment. In FIG. 9B, the oxide film 32 is not shown. While the above description has been given of an example in which the aluminum member 10 has a protruding portion 10c, as shown in FIG. 9B, the clad material 20 may have a protruding portion 20c protruding from the second surface 20a. The protruding portion 20c is located, for example, around the hole 20b. The protruding portion 20c is a burr or flaking that occurs during the press working process when forming the hole 20b. Alternatively, both the aluminum member 10 and the clad material 20 may have a protruding portion. Note that the greater the number of holes 10d, the greater the number of burrs and flaking, which is advantageous for joining.

[0035] Embodiment 4 A joining method according to embodiment 4 will be described. Here, differences from the joining method according to embodiment 1 will be mainly described, and overlapping descriptions will not be repeated.

[0036] Fig. 10 is a cross-sectional view illustrating the arrangement step S2 in the bonding method according to embodiment 4. As shown in Fig. 10, in the bonding method according to embodiment 4, the aluminum member 10 and the clad material 20 are arranged such that the first surface 10a and the second surface 20a face each other with the silicon particles 30 interposed therebetween.

[0037] The silicon particles 30 may be mixed with an organic solvent, for example, to form a paste, and then disposed between the aluminum member 10 and the clad material 20. The purity of the silicon particles 30 (the silicon content in the silicon particles 30) is preferably 99 mass percent or more. The particle size of the silicon particles 30 is preferably smaller than the thickness T. The silicon particles 30 preferably have an angular shape.

[0038] As described above, in the joining step S3, the aluminum member 10 is pressed toward the clad material 20. Fig. 11A is a first cross-sectional view showing the joining mechanism in the joining method according to the fourth embodiment. As shown in Fig. 11A, in the joining method according to the fourth embodiment, silicon particles 30 are interposed between the aluminum member 10 and the clad material 20. Because the contact areas between the silicon particles 30 and the aluminum member 10 and between the silicon particles 30 and the clad material 20 are small, stress concentration is likely to occur at the contact points. This stress concentration promotes destruction of the oxide films 31 and 32.

[0039] Therefore, according to the joining method of the fourth embodiment, contact between the molten brazing filler metal 22 and the aluminum member 10 is further promoted, and it is possible to achieve even better joining. If the silicon particles 30 have an angular shape, the above-mentioned stress concentration is more likely to occur, which further promotes destruction of the oxide films 31 and 32.

[0040] FIG. 11B is a second cross-sectional view showing the bonding mechanism in the bonding method according to the fourth embodiment. Silicon has a high melting point (approximately 1400°C) but is easily dissolved in molten aluminum. Therefore, as shown in FIG. 11B, silicon particles 30 dissolve into the molten brazing material 22 upon contact with the brazing material 22 and disappear from the bonding interface. Therefore, even if silicon particles 30 are interposed between the aluminum member 10 and the clad material 20, they are unlikely to adversely affect the bonding. Note that when the particle size of silicon particles 30 is smaller than the thickness T, silicon particles 30 are easily dissolved in the molten brazing material 22, making it possible to more reliably remove silicon particles 30 from the bonding interface.

[0041] Fig. 12 is an optical microscope image of the joint interface between the aluminum member 10 and the clad material 20. In the sample used for the cross-sectional image of Fig. 12, the thickness of the aluminum member 10 was 2 mm, and the constituent material of the aluminum member 10 was A6063. In this sample, the thickness of the clad material 20 was 0.3 mm, the thickness (thickness) of the brazing filler metal 22 was 0.021 mm, and the clad ratio of the clad material 20 was 7.5%. In this sample, the constituent material of the core material 21 was A3003, and the constituent material of the brazing filler metal 22 was an aluminum alloy containing 7 mass% silicon.

[0042] In this sample, silicon particles 30 in a paste form mixed with ethanol are supplied between the aluminum member 10 and the clad material 20, the particle size of the silicon particles 30 is 5 μm, the purity of the silicon particles 30 is 99.9 mass %, and the amount of the paste applied is 7.5 g / m ２ In this sample, the pressure in the bonding step S3 was applied using a pressure jig, and the pressure was 100 kPa. In this sample, the heating in the bonding step S3 was performed at 620°C in a nitrogen atmosphere. Prior to observation with an optical microscope, the sample was cut at the center, and the cross section was polished and etched. As shown in Figure 12, in this sample, the clad material 20 and the aluminum member 10 were well bonded, and it can be seen that no silicon particles 30 remained at the bonding interface.

[0043] Embodiment 5 A joining method according to embodiment 5 will be described. Here, differences from the joining method according to embodiment 1 will be mainly described, and overlapping descriptions will not be repeated.

[0044] In the joining method according to the fifth embodiment, the magnesium concentration in the brazing filler metal 22 is set to be less than 0.1 mass percent. Note that "a magnesium concentration of less than 0.1 mass percent" includes cases where the brazing filler metal 22 does not contain magnesium. The higher the magnesium concentration in the brazing filler metal 22, the harder and more brittle the brazing filler metal 22 becomes. Therefore, by setting the magnesium concentration in the brazing filler metal 22 to be 0.1 mass percent or less, it is possible to ensure the rollability of the clad material 20.

[0045] Sixth Embodiment A method for manufacturing a semiconductor device according to a sixth embodiment will be described.

[0046] Fig. 13 is a schematic diagram of a semiconductor device 200. As shown in Fig. 13, the semiconductor device 200 has a cooler 210 and a semiconductor chip 220. The cooler 210 has a base 211, fins 212, a jacket 213, a refrigerant inlet 214, and a refrigerant outlet 215.

[0047] The base 211 is an aluminum member 10. The fins 212 are clad materials 20. The base 211 is bonded to the fins 212. FIG. 14 is a perspective view of the clad materials 20 constituting the fins 212. As shown in FIG. 14, holes 20b are formed in each of the clad materials 20 constituting the fins 212 as needed. The holes 20b serve as flow paths for the coolant. The minimum width of the holes 20b is, for example, about 0.2 mm. The shape of the holes 20b is, for example, elliptical. It is also preferable that a large number of holes 20b be formed in each of the clad materials 20. The number of holes 20b is, for example, 50 or more for an area of ​​30 mm x 30 mm. The thickness of each of the clad materials 20 is, for example, 0.2 mm or more and 0.5 mm or less.

[0048] The jacket 213 is, for example, box-shaped. The jacket 213 is attached to the fins 212 so as to cover the outside of the fins 212. A refrigerant inlet 214 and a refrigerant outlet 215 are attached to the jacket 213. The refrigerant flows into the cooler 210 from the refrigerant inlet 214, flows through a flow path inside the cooler 210, and is discharged to the outside of the cooler 210 from the refrigerant outlet 215.

[0049] The semiconductor chip 220 is disposed on the base 211. The semiconductor chip 220 is, for example, soldered to the base 211. The soldering surface of the base 211 may be plated to improve the wettability of the solder. For example, copper plating, nickel plating, or the like is used for the plating. The semiconductor chip 220 may be joined to the base 211 by, for example, a sintered body of silver particles.

[0050] 15A is a first schematic diagram illustrating a method for manufacturing the semiconductor device 200. In the method for manufacturing the semiconductor device 200, first, the base 211 and the fins 212 are stacked as shown in FIG. 15A . In the method for manufacturing the semiconductor device 200, second, the base 211 is brazed to the fins 212 by the joining method according to any one of the first, second, third, fourth, and fifth embodiments. Therefore, it is not necessary to supply flux to the joining surfaces between the base 211 and the fins 212. Pressure is applied when the above-described joining method is performed, for example, by sandwiching the stacked base 211 and fins 212 between plate jigs and fastening the plate jigs with screws or the like.

[0051] 15B is a second schematic diagram showing a manufacturing method of the semiconductor device 200. In the manufacturing method of the semiconductor device 200, third, as shown in FIG. 15B , the jacket 213 is attached to the fins 212. The jacket 213 is attached to the fins 212 by, for example, mechanical fastening, welding, brazing, solid-state welding, or the like. In the manufacturing method of the semiconductor device 200, fourth, a coolant inlet 214 and a coolant outlet 215 are attached to the jacket 213. The coolant inlet 214 and the coolant outlet 215 are attached to the jacket 213 by, for example, brazing.

[0052] 15C is a third schematic diagram showing the manufacturing method of the semiconductor device 200. In the manufacturing method of the semiconductor device 200, in the fifth step, the semiconductor chip 220 is bonded to the base 211. As described above, the semiconductor chip 220 is bonded to the base 211 by, for example, soldering or sintering silver particles. In this way, the structure of the semiconductor device 200 shown in FIG. 13 is formed.

[0053] Seventh Embodiment A method for manufacturing a semiconductor device according to a seventh embodiment will be described. Here, differences from the method for manufacturing a semiconductor device according to the sixth embodiment will be mainly described, and overlapping descriptions will not be repeated.

[0054] The semiconductor device according to the seventh embodiment is referred to as semiconductor device 200A. Fig. 16 is a cross-sectional view of fin 212 used in semiconductor device 200A. As shown in Fig. 16, in semiconductor device 200A, fin 212 has a plurality of aluminum members 10 and a plurality of clad materials 20.

[0055] As described above, the constituent material of the aluminum member 10 is an aluminum alloy containing magnesium or an aluminum alloy containing magnesium and silicon. The clad material 20 has a brazing filler metal 22 on the second surface 20a, and also has a brazing filler metal 22 on the surface opposite the second surface 20a. That is, the clad material 20 is a double-clad material. The clad ratio of the clad material 20 is, for example, 2% or more and 13% or less. Here, the clad ratio is the value obtained by dividing the thickness of the brazing filler metal 22 disposed on one surface of the clad material 20 by the total thickness of the clad material 20 and multiplying the result by 100. The thickness of the brazing filler metal 22 on the second surface 20a and the thickness of the brazing filler metal 22 on the surface opposite the second surface 20a may be the same or different.

[0056] In the fin 212 of the semiconductor device 200A, aluminum members 10 and clad materials 20 are alternately and repeatedly laminated. However, the members forming the outermost surfaces (the bottom and top members in FIG. 16 ) are aluminum members 10. This is because if the members forming the outermost surfaces were clad materials 20, there is a risk that they would be joined to other members when the brazing filler metal 22 melts.

[0057] When forming the fins 212 of the semiconductor device 200A, first, holes are drilled in the aluminum members 10 and the clad material 20. These holes serve as channels for the coolant to flow through. Second, the aluminum members 10 and the clad material 20 are alternately stacked. At this time, no flux is applied between the aluminum members 10 and the clad material 20. Third, the stacked aluminum members 10 and the clad material 20 are heated while being pressurized, thereby brazing them with the brazing material 22. This forms the fins 212 having a structure in which the aluminum members 10, the core material 21, and the brazing material 22 are alternately arranged. Note that if the aluminum alloy constituting the aluminum member 10 contains silicon in addition to magnesium, a portion of the base material of the aluminum member 10 melts when the temperature is raised for brazing, resulting in a solid-liquid coexistence state. This makes the oxide film more easily destroyed, enabling better bonding.

[0058] [Appendix] Various aspects of the present disclosure are summarized as appendices.

[0059] <Supplementary Note 1> A joining method comprising the steps of: preparing an aluminum member and a clad material; the aluminum member having a first surface; a constituent material of the aluminum member being an aluminum alloy containing magnesium; the clad material having a second surface; the clad material having a core material and a brazing filler metal disposed on the core material; the brazing filler metal forming the second surface; and a constituent material of the brazing filler metal being an aluminum alloy containing silicon;

[0060] <Supplementary Note 2> The joining method according to Supplementary Note 1, wherein the aluminum members are made of an aluminum alloy containing magnesium and silicon.

[0061] <Supplementary Note 3> The bonding method according to Supplementary Note 1 or Supplementary Note 2, wherein the first surface has an uneven surface.

[0062] <Supplementary Note 4> The bonding method according to Supplementary Note 1 or Supplementary Note 2, wherein the second surface has an uneven surface.

[0063] <Supplementary Note 5> The joining method according to Supplementary Note 1 or Supplementary Note 2, wherein the aluminum member has a first protruding portion protruding from the first surface.

[0064] <Supplementary Note 6> The joining method according to Supplementary Note 1 or Supplementary Note 2, wherein the clad material has a second protruding portion protruding from the second surface.

[0065] <Supplementary Note 7> The joining method according to Supplementary Note 1 or Supplementary Note 2, wherein the aluminum member and the clad material are arranged such that the first surface faces the second surface with silicon particles interposed therebetween.

[0066] <Supplementary Note 8> The joining method according to any one of Supplementary Note 1 to Supplementary Note 7, wherein the concentration of magnesium in the brazing filler metal is less than 0.1 mass percent.

[0067] <Supplementary Note 9> A method for manufacturing a semiconductor device, comprising: joining a base and a fin by the joining method according to any one of Supplementary Note 1 to Supplementary Note 8; wherein the base and the fin are the aluminum member and the clad material, respectively.

[0068] <Supplementary Note 10> The method for manufacturing a semiconductor device according to Supplementary Note 9, further comprising the step of fastening a jacket to the fin.

[0069] <Supplementary Note 11> The method for manufacturing a semiconductor device according to Supplementary Note 9 or Supplementary Note 10, further comprising the step of bonding a semiconductor chip onto the base.

[0070] <Supplementary Note 12> A semiconductor device comprising: a cooler; and a semiconductor chip bonded to the cooler; wherein the cooler has fins; wherein the fins have a plurality of aluminum members and a plurality of clad materials; wherein each of the plurality of aluminum members and each of the plurality of clad materials are alternately stacked; wherein each of the plurality of clad materials has a core material and a brazing material disposed on one surface of the core material and on the other surface of the core material opposite to the one surface; wherein a constituent material of the brazing material is an aluminum alloy containing silicon; and wherein a constituent material of each of the plurality of aluminum members is an aluminum alloy containing magnesium or an aluminum alloy containing magnesium and silicon.

[0071] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0072] 10 Aluminum member, 10a First surface, 10b Protrusion, 10c Protruding portion, 10d Hole, 20 Cladding material, 20a Second surface, 20b Hole, 20c Protruding portion, 21 Core material, 22 Brazing material, 23 Bonding layer, 30 Silicon particles, 31, 32 Oxide coating, 100 Bonded body, 200 Semiconductor device, 210 Cooler, 211 Base, 212 Fin, 213 Jacket, 214 Coolant inlet, 215 Coolant outlet, 220 Semiconductor chip, S1 Preparation step, S2 Placement step, S3 Bonding step, T Thickness.

Claims

1. The method includes the steps of preparing an aluminum member and a clad material; the aluminum member has a first surface; the aluminum member is made of an aluminum alloy containing magnesium, the clad material has a second surface and a second protrusion protruding from the second surface; The clad material includes a core material and a brazing material disposed on the core material, The brazing material forms the second surface, the brazing filler metal is an aluminum alloy containing silicon; placing the aluminum member and the clad material so that the first surface faces the second surface; and melting the brazing material while the aluminum member is pressed against the clad material.

2. 2. The joining method according to claim 1, wherein the aluminum member is made of an aluminum alloy containing magnesium and silicon.

3. The bonding method according to claim 1 , wherein the first surface has an uneven surface.

4. The bonding method according to claim 1 , wherein the second surface has an uneven surface.

5. The joining method according to claim 1 , wherein the aluminum member has a first protruding portion protruding from the first surface.

6. The bonding method according to claim 1 , wherein the aluminum member and the clad material are arranged with the first surface facing the second surface with silicon particles interposed therebetween.

7. The joining method according to claim 1 , wherein the concentration of magnesium in the brazing filler metal is less than 0.1 mass percent.

8. a step of joining a base and a fin by the joining method according to claim 1, The method for manufacturing a semiconductor device, wherein the base and the fin are the aluminum member and the clad material, respectively.

9. The method for manufacturing a semiconductor device according to claim 8 , further comprising the step of fastening a jacket to the fin.

10. The method for manufacturing a semiconductor device according to claim 9 , further comprising the step of bonding a semiconductor chip onto the base.

11. A cooler; a semiconductor chip bonded to the cooler, the cooler has fins, The fin has a plurality of aluminum members and a plurality of clad materials, the plurality of aluminum members and the plurality of clad materials are alternately stacked, Each of the plurality of clad materials has a core material and a brazing material disposed on one surface of the core material and on the other surface of the core material that is the opposite surface of the one surface, the brazing filler metal is an aluminum alloy containing silicon; a constituent material of each of the plurality of aluminum members is an aluminum alloy containing magnesium or an aluminum alloy containing magnesium and silicon, The aluminum member and the clad material have holes.

12. The aluminum member has a first surface facing the clad material, the aluminum member has a first protruding portion protruding from the first surface, The semiconductor device according to claim 11 , wherein the first protrusion is a burr or a burr.

13. The clad material has a second surface facing the aluminum member, The semiconductor device according to claim 11 , wherein the clad material has a second protruding portion protruding from the second surface.

14. A semiconductor device as described in Claim 11, wherein the concentration of magnesium contained in the brazing material is less than 0.1 mass percent.