Method for producing copper-aluminum-clad material, method for producing heat sink, copper-aluminum-clad material, and heat sink

Abstract

This method for producing a copper-aluminum-clad material is characterized by comprising: a stacking step for forming a stack (20) by stakcing a copper member (2) and an aluminum member (3), the copper member (2) having, on an opposing surface thereof opposing the aluminum member (3), a coating layer (10) that is formed of a metallic material in close contact with said opposing surface and inhibits oxide formation, with the coating layer (10) and the aluminum member (3) facing each other; and a forging step for hot-forging the stack (20) to achieve forged bonding, wherein, in the forging step, a nascent surface (10a) of the coating layer (10) and a nascent surface (3a) of the aluminum member (3) are brought into close contact with each other and bonded to each other with the copper member (2) and the coating layer (10) being in close contact with each other.

Description

Manufacturing method of copper-aluminum clad material, manufacturing method of heat sink, copper-aluminum clad material and heat sink

[0001] The present invention relates to a method for manufacturing a copper-aluminum clad material, a method for manufacturing a heat sink, a copper-aluminum clad material, and a heat sink.

[0002] Heat sinks are used to dissipate heat from electronic components. Copper or aluminum is used as the material for heat sinks. Copper has excellent thermal conductivity and solder wettability. Aluminum has excellent cost, light weight, corrosion resistance, and workability. In order to take advantage of the properties of both copper and aluminum, development is underway to develop heat sinks that have copper on the side where the electronic components are placed and aluminum on the other side where the fins are formed.

[0003] Patent Document 1 discloses a heat sink that is a composite plate (clad material) made of aluminum and copper, in which aluminum heat dissipation fins are provided on the surface of the aluminum plate of the composite plate, and the rolled surface of the composite plate is metallurgically bonded (diffusion bonded). Patent Document 1 describes that the aluminum plate and the copper plate are heated separately, and then the two are overlapped and rolled to metallurgically bond the composite plate.

[0004] Japanese Patent Application Publication No. 9-298259

[0005] In Patent Document 1, a composite plate made of a copper member and an aluminum member is hot-rolled, which may result in the formation of oxides at the bonding surface between the copper member and the aluminum member. In areas where oxides are formed, poor bonding occurs between the copper member and the aluminum member, resulting in a problem of reduced adhesion of the clad material, which may lead to peeling. Furthermore, from the perspective of mass productivity, it is desirable to be able to easily manufacture clad materials or heat sinks using clad materials.

[0006] From this perspective, an object of the present invention is to provide a method for manufacturing a copper-aluminum clad material that is easy to manufacture and does not easily peel off, a method for manufacturing a heat sink, a copper-aluminum clad material, and a heat sink.

[0007] [1] In order to solve the above-mentioned problems, the present invention provides a method for producing a copper-aluminum clad material by forging and joining a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy, to produce a clad material. The copper member has a coating layer formed of a metal material in close contact with the aluminum member on an opposing surface thereof facing the aluminum member, the coating layer suppressing the generation of oxides. The method includes a lamination step of laminating the copper member and the aluminum member with the coating layer and the aluminum member facing each other to form a laminate, and a forging step of forging and joining the laminate by hot forging. The method is characterized in that in the forging step, a newly formed surface of the coating layer and a newly formed surface of the aluminum member are closely contacted and joined together while the copper member and the coating layer are in close contact with each other.

[0008] [2] In the method for producing a copper-aluminum clad material according to [1], it is preferable that in the forging step, the coating layer is divided to form a divided portion where the coating layer is not present between the divided coating layers, and the aluminum member is introduced into the divided portion, thereby bringing a new surface of the copper member exposed at the divided portion into close contact with a new surface of the aluminum member, thereby joining the copper member and the aluminum member.

[0009] [3] In the method for producing a copper-aluminum clad material according to [1] or [2], it is preferable that the metal material is at least one metal selected from the group consisting of titanium, vanadium, chromium, manganese, cobalt, nickel, molybdenum, rhodium, palladium, silver, platinum, and gold, or an alloy thereof.

[0010] [4] Preferably, the method for producing a copper aluminum clad material according to any one of [1] to [3] further comprises a coating step of forming the coating layer on the copper member.

[0011] [5] Preferably, in the method for producing a copper aluminum clad material according to any one of [1] to [4], the coating layer is a plating layer, and in the coating step, the plating layer is formed by plating the copper member.

[0012] [6] In the method for producing a copper-aluminum clad material according to [5], the plating treatment is preferably Ni electroplating, electroless Ni—P plating, or Ni—Cr electroplating.

[0013] [7] Preferably, in the method for producing a copper aluminum clad material according to [5] or [6], the thickness of the plating layer is 15 μm or less.

[0014] [8] Preferably, the method for producing a copper aluminum clad material according to any one of [1] to [7] further comprises a heating step of preheating the laminate in an atmospheric atmosphere, and in the forging step, the laminate preheated in the heating step is hot forged in an atmospheric atmosphere.

[0015] [9] The present invention is a method for manufacturing a heat sink, which involves forming fins on an aluminum member while carrying out the method for manufacturing a copper aluminum clad material according to any one of [1] to [8], and is characterized in that in the forging step, the laminate is forged and joined by hot forging, and fins are formed on the aluminum member.

[0016]

[10] The present invention is characterized in that it is a method for manufacturing a heat sink, comprising a cutting fin forming process for forming fins by cutting the aluminum member after carrying out the method for manufacturing a copper aluminum clad material described in any one of [1] to [8].

[0017]

[11] The present invention provides a copper-aluminum clad material in which a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are joined together, wherein an intervening layer made of a metal material is interposed between the copper member and the aluminum member to join them, the copper member and the intervening layer are closely adhered to each other, and the intervening layer and the aluminum member are closely adhered to each other and joined together, and the intervening layer has a thickness of 10 μm or less.

[0018]

[12] Preferably, the intermediate layer has a continuous portion where the intermediate layer is present and a divided portion where the intermediate layer is not present, one surface of the continuous portion is tightly bonded to the copper member, and the other surface of the continuous portion is tightly bonded to the aluminum member, and at the divided portion, the copper member exposed from the intermediate layer and the aluminum member are tightly bonded to each other in the copper aluminum clad material described in

[11] .

[0019]

[13] The metal material is preferably the copper aluminum clad material according to

[11] or

[12] , which contains nickel.

[0020]

[14] The present invention provides a heat sink in a copper-aluminum clad material in which a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are bonded together, with fins formed on the aluminum member, wherein the copper member and the aluminum member are bonded together with an intervening layer made of a metal material, the copper member and the intervening layer are closely adhered to each other, and the intervening layer and the aluminum member are closely adhered to each other and bonded together, and the intervening layer has a thickness of 10 μm or less.

[0021] According to the present invention, a method for manufacturing a copper-aluminum clad material that is easy to manufacture and that is resistant to peeling, a method for manufacturing a heat sink, and a copper-aluminum clad material and a heat sink can be obtained.

[0022] 6 is a side view of a copper-aluminum clad material according to a first embodiment of the present invention; FIG. 7 is a side view showing a preparation step and a covering step of a manufacturing method for a copper-aluminum clad material according to the first embodiment; FIG. 8 is a side view showing a laminating step and a heating step of a manufacturing method for a copper-aluminum clad material according to the first embodiment; FIG. 9 is a side view of a heat sink according to a second embodiment of the present invention; FIG. 10 is a side view of a copper-aluminum clad material according to a third embodiment of the present invention; FIG. 11 is an enlarged view of FIG. 16; FIG. 17 is a side view showing a forging step of a manufacturing method for a copper-aluminum clad material according to a third embodiment of the present invention; FIG. 18 is a side view of a heat sink according to a fourth embodiment of the present invention; FIG. 19 is a table showing test conditions and test results of Test 1; FIG. 20 is a scanning electron microscope photograph of Example 1; FIG. 21 is a scanning electron microscope photograph of Example 2; FIG. 22 is a scanning electron microscope photograph of Example 3; FIG. 23 is a scanning electron microscope photograph of Comparative Example 1; FIG. 24 is an enlarged photograph of FIG. 14; FIG. 25 is a scanning electron microscope photograph of Example 4; FIG. 26 is a scanning electron microscope photograph of Example 5; FIG. 27 is a scanning electron microscope photograph of Example 6; FIG. 28 is a scanning electron microscope photograph of Example 7; FIG. 29 is a scanning electron microscope photograph of Comparative Example 2; FIG. 30 is an enlarged photograph of FIG. 25 is a scanning electron microscope photograph of Example 8. FIG. 26 is a scanning electron microscope photograph of Comparative Example 3. FIG. 27 is an enlarged view of FIG. 23. FIG. 28 is a scanning electron microscope photograph of Comparative Example 4. FIG. 29 is an enlarged view of FIG.

[0023] The following describes embodiments of the present invention with reference to the accompanying drawings. The present invention is not limited to the following embodiments. The components in the embodiments and modifications can be combined in part or in whole as appropriate. The directions used in the description are used for convenience and do not limit the present invention. For convenience of explanation, the intervening layer (coating layer) is depicted in a schematic diagram with the actual scale of the component altered.

[0024] [1. First Embodiment] [1-1. Copper-aluminum clad material] A copper-aluminum clad material according to a first embodiment of the present invention will be described. As shown in Fig. 1, the copper-aluminum clad material 1 according to this embodiment includes a copper member 2, an aluminum member 3, and an intermediate layer 4. The copper-aluminum clad material 1 is in the form of a plate, and is a member in which the copper member 2 and the aluminum member 3 are bonded together.

[0025] The copper member 2 is formed of copper or a copper alloy and has a plate shape. The copper member 2 may be any material that can be forged. Examples of copper members that can be used include oxygen-free copper (C1020) and tough pitch copper (C1100) with a copper purity of 99.0% or more. It is preferable that the content of components other than copper is 0.1% by mass or less. This can improve the strength and workability of the copper member. It is also preferable that the copper member be a 1000 series copper member. This can improve the electrical conductivity and thermal conductivity of the copper member. This is particularly suitable when the copper-aluminum clad material is used as a heat sink.

[0026] The aluminum member 3 is formed of aluminum or an aluminum alloy and has a plate shape. The aluminum member 3 may be any forgeable material, and the composition of the aluminum member may be appropriately determined. Examples of the aluminum member 3 that can be used include 1000-series pure aluminum, 2000-series, 6000-series, and 7000-series aluminum alloys, or age-hardened alloys thereof. The aluminum member 3 preferably contains, for example, 2% by mass or less of components other than aluminum. This improves the strength, corrosion resistance, and workability (machinability and rollability) of the aluminum member. The aluminum member preferably contains, for example, 0.1% by mass or less of manganese. This improves the thermal conductivity of the aluminum member. The aluminum member is preferably a 6000-series alloy. This improves the strength and corrosion resistance of the aluminum member.

[0027] The intermediate layer 4 is a layer formed between the copper member 2 and the aluminum member 3. In this embodiment, the intermediate layer 4 is formed over the entire surface of the copper member 2, but it is sufficient that the intermediate layer 4 is formed at least between the copper member 2 and the aluminum member 3.

[0028] The intermediate layer 4 is formed of a metal material, such as at least one metal selected from the group consisting of titanium, vanadium, chromium, manganese, cobalt, nickel, molybdenum, rhodium, palladium, silver, platinum, and gold, or an alloy thereof. The thickness of the intermediate layer 4 may be set as appropriate, but is, for example, 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and particularly preferably 5 μm or less. Whether the intermediate layer 4 is formed of the desired metal material can be determined by observing the bonded cross section containing the intermediate layer 4 using energy dispersive X-ray spectroscopy (SEM-EDS) or an electron probe microanalyzer (EPMA) and performing a composition analysis of the region of the intermediate layer 4.

[0029] The intermediate layer 4 can be formed, for example, by plating the copper member 2, but may also be formed by other methods. When the intermediate layer 4 is formed by plating, Ni electroplating, electroless Ni—P plating, Ni—Cr electroplating, or the like can be performed.

[0030] There is no oxide film between the copper member 2 and the intervening layer 4, and they are joined in a tight contact state. There is also no oxide film between the intervening layer 4 and the aluminum member 3, and they are joined in a tight contact state. More specifically, the new surface formed by breaking the oxide film of the intervening layer 4 and the new surface formed by breaking the oxide film of the aluminum member 3 are joined in a tight contact state by hot forging. The significance of this tight contact will be described later.

[0031] [1-2. Manufacturing Method of Copper Aluminum Clad Material] Next, a manufacturing method of the copper aluminum clad material according to this embodiment will be described. In the manufacturing method of the copper aluminum clad material according to this embodiment, a preparation step, a covering step, a lamination step, a heating step, and a forging step are performed in this order.

[0032] The preparation step is a step of preparing a copper member 2 and an aluminum member 3, as shown in Fig. 2. The coating step is a step of forming a coating layer 10 on the opposing surface 2a of the copper member 2 that faces the aluminum member 3, as shown in Fig. 2. The coating layer 10 may be provided on at least the opposing surface 2a, but in this embodiment, the coating layer 10 is formed on the entire surface of the copper member 2.

[0033] The coating process is not limited to a specific coating method, but in this embodiment, it is performed by plating. Examples of plating methods that can be used include electrolytic Ni plating, electroless Ni—P plating, and electrolytic Ni—Cr plating. The coating process is preferably performed so that the oxide film between the copper member 2 and the coating layer 10 is removed, and they are joined in a tightly adhered state, while preventing oxides from being generated on the outer surface of the coating layer 10 during the forging process described below.

[0034] The thickness of the plating layer in the coating step (thickness of the coating layer 10) may be appropriately set depending on the material, film thickness, and formation conditions of the coating layer 10; the preheating temperature; the pressure in the forging step, etc. For example, the thickness of the plating layer is preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 10 μm or less. By setting the thickness of the plating layer to 15 μm or less, the coating layer 10 deforms in accordance with the deformation of the copper member 2 and the aluminum member 3 during the forging step described below, thereby preventing the generation of voids between the copper member 2 and the coating layer 10 and between the aluminum member 3 and the coating layer 10.

[0035] In the lamination step, as shown in FIG. 3, the copper member 2 and the aluminum member 3 are laminated together in a state in which the coating layer 10 and the aluminum member 3 face each other, thereby forming a laminate 20 .

[0036] As shown in FIG. 3 , the heating process is a process of preheating the laminate 20. In the heating process, the laminate 20 is placed in a heating furnace (not shown) and preheated to a predetermined temperature. The heating process may be performed in an inert gas atmosphere such as argon gas or nitrogen gas, but in this embodiment, preheating is performed in the air (in the air atmosphere). The predetermined temperature T is preferably a temperature at which, during the forging process described below, the coating layer 10 is not separated, the oxide film (not shown) of the coating layer 10 is broken to expose the newly formed surface 10 a (see FIG. 4 ), and the oxide film (not shown) of the aluminum member 3 is broken to expose the newly formed surface 3 a (see FIG. 4 ). The predetermined temperature T can be set according to the solidus temperature of the aluminum member 3. For example, the predetermined temperature T is preferably solidus temperature × 50% (°C) ≦ T, more preferably solidus temperature × 65% (°C) ≦ T, even more preferably solidus temperature × 75% (°C) ≦ T, preferably T ≦ solidus temperature × 98% (°C), more preferably T ≦ solidus temperature × 93% (°C), and even more preferably T ≦ solidus temperature × 90% (°C).

[0037] As shown in FIG. 4 , the forging process is a process of hot forging in the air (under the atmospheric environment) by pressing the copper member 2 and the aluminum member 3 toward each other with a predetermined pressure P. The forging process is also performed at room temperature. That is, in this embodiment, hot forging is performed in the air at room temperature. The pressing time in the forging process may be set appropriately, but may be approximately 1 to 3 seconds, and is set to 1 second in this embodiment. The predetermined pressure P is preferably a pressure that, when the forging process described below is performed, does not separate the coating layer 10, breaks the oxide film (not shown) of the coating layer 10, exposing the newly formed surface 10 a, and breaks the oxide film (not shown) of the aluminum member 3, exposing the newly formed surface 3 a. In the forging process, the newly formed surface 10 a of the coating layer 10 exposed by the breakage of the oxide film comes into intimate contact with the newly formed surface 3 a of the aluminum member 3, resulting in a metallurgical bond (diffusion bond).

[0038] The pressure P in the forging process may be appropriately set depending on the materials of the copper member 2 and the aluminum member 3 to be forged; the material, film thickness, and formation conditions of the coating layer 10; the preheating temperature, etc., so that the copper member 2 and the coating layer 10 are in close contact with each other and the newly formed surface 10a of the coating layer 10 and the newly formed surface 3a of the aluminum member 3 can be tightly bonded to each other. For example, the predetermined pressure P is preferably 200 (MPa) ≦ P, more preferably 300 (MPa) ≦ P, even more preferably 400 (MPa) ≦ P, and particularly preferably 500 (MPa) ≦ P. The upper limit of the predetermined pressure P is not particularly limited, but from the viewpoint of avoiding an increase in the size of the press machine and an increase in the equipment costs for the press machine, it is preferably P ≦ 1000 (MPa).

[0039] The meaning of "adhesion" in the claims "in the forging process, the copper member and the coating layer are in close contact with each other, and the newly formed surface of the coating layer is in close contact with the newly formed surface of the aluminum member," "the copper member and the intermediate layer are in close contact with each other, and the intermediate layer is in close contact with the aluminum member," and "one surface of the continuous portion is in close contact with the copper member, and the other surface of the continuous portion is in close contact with the aluminum member" will be explained. Here, "adhesion" is defined as a porosity of less than 15% at the bonded interface, as determined by observing a scanning electron microscope photograph of a cross section at each interface (bonded interface) of the copper-aluminum clad material 1 after the forging process at a magnification of 1000. In other words, if the copper member 2 and the intermediate layer 4 are in close contact with each other at the bonded interface, it can be determined that the copper member 2 and the coating layer 10 were bonded in close contact with each other during the forging process. Furthermore, if the aluminum member 3 and the intervening layer 4 are in close contact at the interface after joining, it can be determined that the newly formed surface of the coating layer 10 and the aluminum member 3 were joined in a state of close contact in the forging process. Furthermore, if the copper member 2 and the aluminum member 3 are in close contact at the interface after joining, it can be determined that the newly formed surface of the copper member 2 and the newly formed surface of the aluminum member 3 were joined in a state of close contact in the forging process.

[0040] The porosity refers to the ratio of the length of the region where voids exist to the length of the bonded interface in the interface direction within the field of view. In particular, the porosity refers to the ratio of the length of the region where voids exist to the length of the continuous portion of the coating layer (intermediate layer) in the interface direction of the bonded interface. For example, Figure 23 shows Comparative Example 3 (described below). A scanning electron microscope was set to 1000x magnification, and the porosity at the interface between the copper member 302 and the continuous portion 305 of the coating layer (intermediate layer 304) (the ratio of the total length of voids to the total length of the continuous portion at the bonded interface within the field of view of the photograph) was approximately 26%, indicating poor adhesion (the bonding result was "poor").

[0041] The copper-aluminum clad material 1 is formed through the above steps. The forging process presses and deforms the coating layer 10 (slightly thinning it) to form the intermediate layer 4. At this time, the metallic material contained in the coating layer 10 may react with the aluminum of the aluminum member 3 to form an intermetallic compound. For example, if the coating layer 10 is a nickel layer made of nickel, the nickel and aluminum react to produce an Al / Ni compound as the intermetallic compound. In this case, the intermediate layer 4 has a multi-layer structure including a metallic material layer made of a metallic material on the copper member 2 side and an intermetallic compound layer made of an intermetallic compound on the aluminum member 3 side. As a result, in the copper-aluminum clad material 1, the copper member 2 and the metallic material layer of the intermediate layer 4 are closely adhered to each other, and the intermetallic compound layer of the intermediate layer 4 and the aluminum member 3 are closely adhered to each other and joined together.

[0042] The method for producing the copper-aluminum clad material is not limited to the above-described embodiment, and for example, hot forging may be performed while heating the laminate 20 during the forging step without preheating. Also, the coating step may be omitted, and a copper member on which a coating layer has been formed in advance may be used.

[0043] [1-3. Effects] Generally, when forming a copper-aluminum clad material using a copper member and an aluminum member, hot forging is preferable to cold forging because it promotes metal bonding (diffusion bonding). However, when the copper member is heated, the oxide film on the copper member oxidizes, and a large amount of oxide is generated on the surface of the copper member, making it substantially difficult to bond the copper member and the aluminum member.

[0044] On the other hand, conventionally, when forming a clad material of a copper member and an aluminum member, hot forging is performed with a metal member interposed (simply arranged) between the two. However, if a metal member is simply interposed during hot forging, the linear expansion coefficients of each member are different, so the interposed metal member cannot follow the deformation of the copper member and the aluminum member during hot forging. This results in the generation of voids between the copper member and the metal member, and between the aluminum member and the metal member, resulting in a decrease in thermal conductivity, a decrease in strength, etc. Furthermore, if a metal member is simply interposed during hot forging, the presence of an oxide film between the copper member and the metal member causes poor joining.

[0045] Furthermore, when a clad material of a copper member and an aluminum member is manufactured by hot forging, preheating and hot forging are performed in an inert gas atmosphere and the surface oxide film is removed in order to avoid the influence of an oxide film formed on the surface of the copper member on the bonding. In this case, large-scale devices and equipment are required for preheating and hot forging in an inert gas atmosphere and for removing the surface oxide film.

[0046] In this regard, according to the copper-aluminum clad material 1 and the manufacturing method of the copper-aluminum clad material of the present embodiment, the copper member 2 is provided with a coating layer 10 that suppresses the generation of oxides, and in the forging process, the copper member 2 and the coating layer 10 are in close contact with each other, and the newly formed surface 10a of the coating layer 10 is closely bonded to the newly formed surface 3a of the aluminum member 3. More specifically, by pressing the heated copper member 2 and the aluminum member 3 during the forging process, the oxide coatings of the coating layer 10 and the aluminum member 3 are destroyed, and the exposed newly formed surfaces 10a, 3a are bonded to each other. This allows bonding to be performed while suppressing the generation of oxides between the copper member 2 and the coating layer 10, and between the aluminum member 3 and the coating layer 10, and makes it possible to form a copper-aluminum clad material 1 that is resistant to peeling.

[0047] Furthermore, in this embodiment, since forging is performed in a state in which the copper member 2 and the coating layer 10 are in close contact with each other and the aluminum member 3 and the coating layer 10 are in close contact with each other, the coating layer 10 follows the deformation of the copper member 2 and the aluminum member 3 during forging. This makes it possible to prevent voids from being generated between the copper member 2 and the coating layer 10 and between the aluminum member 3 and the coating layer 10, and it is possible to form a copper-aluminum clad material 1 that is difficult to peel off. Furthermore, since the copper member 2 provided with the coating layer 10 is simply laminated on the aluminum member 3 and hot forged, no large-scale equipment or facilities are required, and the copper-aluminum clad material 1 can be easily manufactured, thereby improving mass productivity.

[0048] In this embodiment, the metal material used in the coating process is at least one metal selected from the group consisting of titanium, vanadium, chromium, manganese, cobalt, nickel, molybdenum, rhodium, palladium, silver, platinum, and gold, or an alloy thereof. Forming the coating layer 10 using these materials can suppress oxide formation on the copper member 2, resulting in a copper-aluminum clad material 1 that is less likely to peel. This also reduces the amount of oxide film formed on the surface of the coating layer 10. Nickel is particularly preferred as the metal material for the coating layer 10 because of its high corrosion resistance and heat resistance.

[0049] Furthermore, this embodiment includes a coating step of forming the coating layer 10 on the copper member 2. This makes it possible to easily form the coating layer 10.

[0050] In the present embodiment, the coating layer 10 in the coating step is a plated layer, and the plated layer is formed by plating the copper member 2 in the coating step. This makes it possible to easily form the coating layer 10. Furthermore, by performing the plating process, the oxide film on the copper member 2 is removed, and the copper member 2 and the coating layer 10 (plated layer) can be tightly bonded together.

[0051] In this embodiment, the plating process is Ni electroplating, electroless Ni—P plating, or Ni—Cr electroplating. This allows for easy plating. Furthermore, these nickel-containing plating processes have excellent heat resistance, preventing the coating layer 10 from dissolving during a heating process. Furthermore, these nickel-containing plating processes can form a coating layer 10 that has excellent corrosion resistance, as well as appropriate hardness and flexibility. This allows the coating layer 10 to conform to the deformation of the copper member 2 and the aluminum member 3 during the forging process, thereby preventing voids from forming at the interface (joint interface).

[0052] In this embodiment, the thickness of the coating layer 10 (plating layer) is 15 μm or less. In the copper-aluminum clad material 1 according to this embodiment, the thickness of the intervening layer 4 is 10 μm or less. This allows the coating layer 10 to deform in accordance with the deformation of the copper member 2 and the aluminum member 3 during the forging process, thereby preventing voids from being generated between the copper member 2 and the coating layer 10, and between the aluminum member 3 and the coating layer 10.

[0053] In this embodiment, preheating is performed in an air atmosphere, followed by hot forging in an air atmosphere in the forging process. The provision of the coating layer 10 on the copper member 2 prevents the formation of a brittle, thick oxide film on the surface of the copper member 2 during preheating. Therefore, it is possible to prevent the oxide film formed on the surface of the copper member during preheating from interfering with the bonding between the copper member 2 and the aluminum member 3. This eliminates the need for a large-scale device for preheating and hot forging in an inert gas atmosphere to prevent the formation of an oxide film on the surface of the copper member 2. Therefore, atmospheric control is not required during the forging process, and hot forging can be performed in air, reducing manufacturing costs and facilitating production, thereby improving mass productivity. Furthermore, the forging process in this embodiment is completed in one second, making it highly suitable for mass production.

[0054] For example, in this embodiment, the coating layer 10 is provided only on the copper member 2, but the coating layer 10 may also be provided on the aluminum member 3. Even in this embodiment, substantially the same effects as those in the above-described embodiment can be obtained.

[0055] [2. Second Embodiment] [2-1. Heat Sink] Next, a heat sink and a method for manufacturing a heat sink according to a second embodiment will be described. As shown in Fig. 5, a heat sink 30 according to this embodiment includes a copper member 2, an aluminum member 3A, and an intermediate layer 4. The copper member 2 and the intermediate layer 4 are the same as those in the first embodiment.

[0056] The aluminum member 3A includes a base 31 and a plurality of fins 32. The base 31 is a plate-shaped portion and is joined to the copper member 2 via the intervening layer 4. The plurality of fins 32 are provided on the base 31 with gaps therebetween and are integrally formed with the base 31. There are no particular limitations on the method for forming the plurality of fins 32, and they can be formed, for example, by cutting.

[0057] [2-2. Heat sink manufacturing method] In the heat sink manufacturing method according to this embodiment, a preparation step, a coating step, a lamination step, a heating step, a forging step, and a fin forming step are performed in this order. The preparation step, coating step, lamination step, heating step, and forging step of the heat sink manufacturing method are the same as those of the copper aluminum clad material manufacturing method according to the first embodiment described above. In this embodiment, a case where a cutting fin forming step is performed as the fin forming step will be described as an example.

[0058] The cut fin forming process is a process of cutting the aluminum member 3A of the copper-aluminum clad material to form a plurality of fins 32. In the cut fin forming process, for example, the plurality of fins 32 can be formed by cutting using a multi-cutter having a plurality of cutting teeth arranged in a row.

[0059] [2-3. Effects] According to the heat sink and the method for manufacturing a heat sink according to the present embodiment described above, the same effects as those of the first embodiment can be achieved with respect to the bonding of the copper member 2, the aluminum member 3A, and the intervening layer 4. Furthermore, according to the present embodiment, gaps are unlikely to occur between the copper member 2 and the intervening layer 4 and between the intervening layer 4 and the aluminum member 3A, which increases the thermal conductivity from the copper member 2 to the aluminum member 3A and improves the heat dissipation efficiency of the heat sink 30. Furthermore, the cutting fin forming process allows the plurality of fins 32 to be easily formed.

[0060] [3. Third Embodiment] [3-1. Copper-aluminum clad material] Next, a copper-aluminum clad material and a manufacturing method thereof according to a third embodiment will be described. As shown in Fig. 6, a copper-aluminum clad material 101 includes a copper member 102, an aluminum member 103, and an intermediate layer 104. The copper-aluminum clad material 101 according to this embodiment differs from the first embodiment in that the intermediate layer 104 includes a plurality of continuous portions 105 and divided portions 106. The material types of the copper member 102 and the aluminum member 103 are the same as those of the first embodiment.

[0061] The intermediate layer 104 is a layer-like portion formed between the copper member 102 and the aluminum member 103. The intermediate layer 104 has a plurality of continuous portions 105 where the intermediate layer 104 is present and a plurality of divided portions 106 where the intermediate layer 104 is not present.

[0062] The intermediate layer 104 is formed of a metal material, such as at least one metal selected from the group consisting of titanium, vanadium, chromium, manganese, cobalt, nickel, molybdenum, rhodium, palladium, silver, platinum, and gold, or an alloy thereof. The thickness of the intermediate layer 104 may be set appropriately, but is, for example, 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and particularly preferably 5 μm or less.

[0063] The intermediate layer 104 can be formed, for example, by plating the copper member 102, but may also be formed by other methods. When the intermediate layer 104 is formed by plating, Ni electroplating, electroless Ni—P plating, Ni—Cr electroplating, or the like can be performed.

[0064] The dividing portions 106 of the intervening layer 104 are portions formed by dividing the intervening layer 104. The size of the dividing portions 106 may be uniform, but in this embodiment they are non-uniform. The spacing between adjacent dividing portions 106, 106 may also be uniform, but in this embodiment they are non-uniform.

[0065] There is no oxide film between the copper member 102 and one surface of the continuous portion 105, and they are joined in a tight contact state. There is also no oxide film between the other surface of the continuous portion 105 and the aluminum member 103, and they are joined in a tight contact state. More specifically, a new surface of the intervening layer 104 formed by breaking the oxide film of the continuous portion 105 and a new surface formed by breaking the oxide film of the aluminum member 103 are joined in a tight contact state by hot forging.

[0066] 7, the aluminum member 103 is densely packed into each separation portion 106, and the copper member 102 and the aluminum member 103 are bonded in an intimate contact state without an oxide film interposed between them. More specifically, the newly formed surface of the copper member 102 exposed by the separation of the intervening layer 104 and the newly formed surface of the aluminum member 103 formed by the destruction of the oxide film thereon are bonded in an intimate contact state by hot forging. The "intimate contact" in the claim "by flowing the aluminum member into the separation portion, the newly formed surface of the copper member exposed at the separation portion and the newly formed surface of the aluminum member are bonded in an intimate contact state" is defined as above.

[0067] The ratio of the dividing portion 106 to the area of ​​the interface between the copper member 102 and the aluminum member 103 is preferably 15 to 65%, more preferably 20 to 60%, and even more preferably 25 to 55%.

[0068] [3-2. Manufacturing Method of Copper Aluminum Clad Material] Next, a manufacturing method of the copper aluminum clad material according to this embodiment will be described. In the manufacturing method of the copper aluminum clad material according to this embodiment, a preparation step, a covering step, a lamination step, a heating step, and a forging step are performed in this order.

[0069] The preparation process to the heating process of this embodiment are generally the same as those of the first embodiment. As shown in Fig. 8, in the coating process, a coating layer 110 is formed around the entire periphery of the copper member 102. There are no particular limitations on the method for forming the coating layer 110, but in this embodiment, it is formed by plating.

[0070] As shown in Figure 8, the forging process is a process in which hot forging is performed in the air (under the atmospheric atmosphere) by pressing the copper member 102 and the aluminum member 103 in a direction toward each other with a predetermined pressure P. The pressing time in the forging process may be set appropriately, but may be approximately 1 to 3 seconds, and in this embodiment, it is set to 1 second. The predetermined pressure P is preferably a pressure at which, during the forging process, the coating layer 110 is divided, the oxide film (not shown) of the coating layer 110 is removed to expose the new surface 110a, and the oxide film (not shown) of the aluminum member 103 is removed to expose the new surface 103a.

[0071] Furthermore, the predetermined pressure P is preferably a pressure at which, during the forging process, the coating layer 110 is divided to expose the newly formed surface 102a of the copper member 102, and the oxide film (not shown) of the aluminum member 103 is torn to expose the newly formed surface 103a. Furthermore, the predetermined pressure P is preferably a pressure at which, during the forging process, the oxide film of the continuous portion 105 of the coating layer 110 is torn to expose the newly formed surface 105a, and the oxide film (not shown) of the aluminum member 103 is torn to expose the newly formed surface 103a. The pressure P in the forging process according to this embodiment is equivalent to the pressure P described in the first embodiment.

[0072] In the forging process, the newly formed surface 105a of the continuous portion 105, which is exposed by the rupture of the oxide film, comes into close contact with the newly formed surface 103a of the aluminum member 103, forming a metallurgical bond (diffusion bond). Furthermore, the newly formed surface 102a of the copper member 102, which is exposed by the rupture of the coating layer 110, comes into close contact with the newly formed surface 103a of the aluminum member 103, which is exposed by the rupture of the oxide film, forming a metallurgical bond (diffusion bond). Because the coating layer 110 is formed by a plating process while removing the oxide film, the newly formed surface 102a of the copper member 102, which is exposed by the rupture of the coating layer 110, is free of the oxide film in the forging process. Note that some of the overlapping reference numerals are omitted in FIG. 8 .

[0073] The above steps form the copper-aluminum clad material 101. The presence or absence of the dividing portion 106 in the forging step is determined by changing the following factors: the material type and thickness of the coating layer 110 in the coating step, the temperature in the heating step, and the pressure in the forging step.

[0074] [3-3. Effects] The copper-aluminum clad material 101 and the manufacturing method of the copper-aluminum clad material according to the present embodiment described above can achieve effects substantially equivalent to those of the first embodiment. That is, the copper-aluminum clad material 101 and the manufacturing method of the copper-aluminum clad material according to the present embodiment provide the copper member 102 with the coating layer 110 that suppresses oxide generation, and in the forging process, the copper member 102 and the coating layer 110 are in close contact with each other, and the newly formed surface 110a of the coating layer 110 is closely bonded to the newly formed surface 103a of the aluminum member 103. More specifically, by pressing the heated copper member 102 and the aluminum member 103 together during the forging process, the oxide coatings of the continuous portion 105 of the coating layer 110 and the oxide coating of the aluminum member 103 are destroyed, and the exposed newly formed surfaces 105a and 103a are bonded to each other. This makes it possible to prevent oxides from being generated between the copper member 102 and the coating layer 110, and between the aluminum member 103 and the coating layer 110, thereby forming a copper-aluminum clad material 101 that is difficult to peel off.

[0075] Furthermore, by pressing the heated copper member 102 and aluminum member 103 together during the forging process, the coating layer 110 is separated and the oxide film of the aluminum member 103 is destroyed, and the newly formed surfaces 102a, 103a exposed at the separation portion 106 are bonded together. This makes it possible to suppress the generation of oxide between the copper member 102 and the aluminum member 103, and to form a copper-aluminum clad material 101 that is difficult to peel off. In addition, since the aluminum member 103 is densely embedded in the separation portion 106, it is expected that the bonding strength can be increased by an anchor effect.

[0076] [4. Fourth Embodiment] [4-1. Heat Sink] Next, a heat sink and a method for manufacturing the heat sink according to the fourth embodiment will be described. As shown in Fig. 9, a heat sink 130 according to this embodiment includes a copper member 102, an aluminum member 103A, and an intermediate layer 104. The copper member 102 and the intermediate layer 104 (plurality of continuous portions 105 and divided portions 106) are the same as those in the third embodiment.

[0077] The aluminum member 103A includes a base 131 and a plurality of fins 132. The base 131 is a plate-shaped member that is joined to the copper member 102 via an intervening layer 104. The plurality of fins 132 are provided on the base 131 with gaps between them, and are integrally formed with the base 131. There are no particular limitations on the method for forming the plurality of fins 132, but they can be formed, for example, by cutting.

[0078] [4-2. Heat sink manufacturing method] In the heat sink manufacturing method according to this embodiment, a preparation step, a coating step, a lamination step, a heating step, a forging step, and a fin forming step are performed in this order. The preparation step, coating step, lamination step, heating step, and forging step of the heat sink manufacturing method are the same as those of the copper aluminum clad material manufacturing method according to the third embodiment described above. In this embodiment, a case where a cutting fin forming step is performed as the fin forming step will be described as an example.

[0079] The cut fin forming process is a process of cutting the aluminum member 103A of the copper-aluminum clad material to form the plurality of fins 132. In the cut fin forming process, the plurality of fins 132 can be formed by cutting using, for example, a multi-cutter having a plurality of cutting teeth arranged side by side.

[0080] [4-3. Effects] According to the heat sink and the method for manufacturing a heat sink according to the present embodiment described above, the same effects as those of the third embodiment can be achieved with respect to the bonding of the copper member 102, the aluminum member 103A, and the intermediate layer 104. In other words, according to the present embodiment, gaps are less likely to occur between the copper member 102 and the continuous portion 105, between the continuous portion 105 and the aluminum member 103A, and between the copper member 102 and the aluminum member 103A at the dividing portion 106, thereby increasing thermal conductivity. Furthermore, the cutting fin forming process allows the multiple fins 132 to be easily formed.

[0081] [5. Other] <Modifications of the Coating Process> In the above-described embodiment, the coating layers 10, 110 are formed by plating. The method for forming the coating layers 10, 110 is not limited to this, and the coating layers 10, 110 may be formed by, for example, vapor deposition, sputtering, cast-in, or the like of a metal material on the copper member 2.

[0082] <Modification of Fin Forming Process> In the second and fourth embodiments, the case where a cutting fin forming process is performed as the fin forming process has been described as an example. However, the fin forming process may be a forging fin forming process in which fins are formed by forging.

[0083] The forged fin forming step is a step of forming a plurality of fins 32, 132 by deforming the aluminum member 3A, 103A of copper aluminum clad material by cold, warm, or hot forging.

[0084] The multiple fins 32, 132 may be formed by forging the aluminum members 3A, 103A in the forging process after forging and joining the laminated body 20 by hot forging. That is, after joining by forging in the forging process, the fins may be formed by forging again in the forged fin forming process. Alternatively, the multiple fins 32, 132 may be formed by forging and joining the laminated body 20 by hot forging in the forging process, and the multiple fins 32 may be formed by hot forging the aluminum members 3A, 103A. That is, joining by forging in the forging process and forming the fins by forging in the forged fin forming process may be performed simultaneously.

[0085] According to the heat sink and the method for manufacturing the heat sink according to the modified fin forming step described above, the plurality of fins 32, 132 can be easily formed by the forged fin forming step.

[0086] [Test 1] Test 1 was carried out to confirm the effects of the present invention. A test specimen was prepared, and a cross section was observed using a scanning electron microscope (SEM).

[0087] <Measurement of Coating Layer Thickness> The thickness of the coating layer (plating layer) was obtained by measuring the film thickness at 10 arbitrary points on the coating layer included in a cross-sectional SEM photograph taken with an SEM and calculating the average value of the 10 points.

[0088] <Porosity Measurement> A cross-sectional SEM photograph of the bonded interface was taken at 1000x magnification using an SEM. In the cross-sectional SEM image, the size (length) of voids present at the interface was measured, and the total length in the interface direction was calculated. The size of each void was measured as the longest length parallel to the interface. The percentage (%) obtained by dividing the total length of the voids by the total length of the bonded interface included in the field of view of the cross-sectional SEM photograph was used to determine the porosity. Specifically, for the interface between the copper member and the continuous portion of the intermediate layer, the porosity was calculated by dividing the total length of voids present at this interface by the total length of the continuous portion of the intermediate layer. Furthermore, for the interface between the continuous portion of the intermediate layer and the aluminum member, the porosity was calculated by dividing the total length of voids present at this interface by the total length of the continuous portion of the intermediate layer. Furthermore, for the interface between the copper member and the aluminum member at the dividing portion of the intermediate layer, the porosity was calculated by dividing the total length of voids present at this interface by the total length of the dividing portion of the intermediate layer.

[0089] <Conditions> In Test 1, multiple copper-aluminum clad materials 301 (301A to 301M) were prepared as test specimens, and the interfaces (bonding interfaces) were observed. Also, as shown in Fig. 10, in Test 1, test specimens were prepared with different plating types and different thicknesses of the coating layer before forging, and each was observed. Regarding the "bonding results" in the rightmost column, in light of the definition of "adhesion" described above, results in which the porosity at any bonding interface was less than 15% were evaluated as "good" (◯), and results in which the bonding interface had a porosity of 15% or more were evaluated as "poor" (×).

[0090] The manufacturing method of the copper-aluminum clad material of Test 1 includes a preparation process, a coating process, a lamination process, a heating process, and a forging process, in this order. In the preparation process, a copper member made of JIS C1020 was prepared. The copper member had a length of 100 mm, a width of 50 mm, and a thickness of 3 mm. Furthermore, an aluminum member made of JIS A6063 was prepared. The aluminum member 203 had a length of 100 mm, a width of 50 mm, and a thickness of 12 mm.

[0091] In the coating step, a plating treatment was carried out to form a coating layer (finally an intervening layer) on the entire surface of the copper member.

[0092] In the heating step, the copper and aluminum members with the coating layers formed thereon were placed in a heating furnace, set to 500°C, and preheated in the atmosphere for about 1 hour. In the forging step, the pressure was set to 600 (MPa) in the atmosphere, and hot forging was performed for a pressure time of about 1 second. As a result of the above, test specimens were obtained.

[0093] In Case 1 of Test 1 (Examples 1 to 3, Comparative Example 1), electroless Ni—P plating was performed in the coating process. In each example, a coating layer having a thickness of 1.8 μm in Example 1, 3.9 μm in Example 2, 9.5 μm in Example 3, and 15.1 μm in Comparative Example 1 was formed.

[0094] In Case 2 of Test 1 (Examples 4 to 7, Comparative Example 2), electric Ni plating was performed in the coating process. In each example, a coating layer having a thickness of 4.7 μm in Example 4, 5.5 μm in Example 5, 7.4 μm in Example 6, 10.5 μm in Example 7, and 16.4 μm in Comparative Example 2 was formed.

[0095] In Case 3 of Test 3 (Example 8, Comparative Example 3, and Comparative Example 4), electric Ni—Cr plating was performed in the coating process. In each example, a coating layer having a thickness of 4.9 μm in Example 8, 5.9 μm in Comparative Example 3, and 6.5 μm in Comparative Example 4 was formed.

[0096] <Examples 1 to 3, Comparative Example 1> Figure 11 is a scanning electron microscope photograph of Example 1. Figure 11 is an SEM photograph taken at 1000x magnification. In the present specification, photographs with a scale bar of "10 μm" are SEM photographs taken at 1000x magnification, as with Figure 11. As shown in Figure 11, copper-aluminum clad material 301A according to Example 1 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301A, the thickness of the coating layer (intermediate layer 304) after forging is 0.9 μm. In Example 1, the porosity was less than 15% at the interface between the copper member 302 and the continuous portion 305, the interface between the continuous portion 305 and the aluminum member 303, and the interface between the copper member 302 and the aluminum member 303 at the dividing portion 306, and the bonding results were good.

[0097] FIG. 12 is a scanning electron microscope photograph of Example 2. As shown in FIG. 12, copper-aluminum clad material 301B according to Example 2 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301B, the thickness of the coating layer (intermediate layer 304) after forging is 2.7 μm. In Example 2, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306, all of which were in close contact, resulting in good joining results.

[0098] FIG. 13 is a scanning electron microscope photograph of Example 3. As shown in FIG. 13, copper-aluminum clad material 301C according to Example 3 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and divided portions 306 formed therein. In copper-aluminum clad material 301C, the thickness of the coating layer (intermediate layer 304) after forging is 7.9 μm. In Example 3, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306, all of which were in close contact, resulting in good joining results.

[0099] FIG. 14 is a scanning electron microscope photograph of Comparative Example 1. FIG. 15 is an enlarged photograph of FIG. 14. As shown in FIGS. 14 and 15, the copper-aluminum clad material 301D according to Comparative Example 1 includes a copper member 302, an aluminum member 303, and an intervening layer 304. The intervening layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306. The copper-aluminum clad material 301D has a coating layer (intervening layer 304) with a thickness of 14.4 μm after forging. In Comparative Example 1, the porosity at the interface between the copper member 302 and the continuous portion 305 was 0%. However, voids Q were observed at the interface between the continuous portion 305 and the aluminum member 303 and at the interface between the copper member 302 and the aluminum member 303 at the divided portion 306. The porosity at the interface between the copper member 302 and the aluminum member 303 in the divided portion 306 was less than 15%, and they were in close contact, but the porosity at the interface between the continuous portion 305 and the aluminum member 303 was 35%, and they were not in close contact, and the joining results were poor.

[0100] As described above, in Case 1 of Test 1 (Examples 1 to 3, Comparative Example 1), electroless Ni—P plating was performed in the coating process. When the thickness of the coating layer before forging was 1.8 to 9.5 μm, good joining results were obtained. However, when the thickness of the coating layer before forging was 15.1 μm, defects occurred and the joining results were poor. In other words, if the coating layer is too thick, it is presumed that the coating layer cannot follow the deformation of the copper member 302 and the aluminum member 303, resulting in the formation of voids at the interface. It was also found that the forging process reduced the thickness of the intermediate layer (coating layer) compared to before forging. It was also found that the forging process reduced the thickness of the intermediate layer (coating layer) and also formed a dividing portion 306.

[0101] Examples 4 to 7, Comparative Example 2 Figure 16 is a scanning electron microscope photograph of Example 4. As shown in Figure 16, copper aluminum clad material 301E according to Example 4 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper aluminum clad material 301E, the thickness of the coating layer (intermediate layer 304) after forging is 1.9 µm. In Example 4, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306, all of which were in close contact, resulting in good joining results.

[0102] FIG. 17 is a scanning electron microscope photograph of Example 5. As shown in FIG. 17 , copper-aluminum clad material 301F according to Example 5 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301F, the thickness of the coating layer (intermediate layer 304) after forging is 3.8 μm. In Example 5, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306, all of which were in close contact, resulting in good joining results.

[0103] Fig. 18 is a scanning electron microscope photograph of Example 6. As shown in Fig. 18, copper aluminum clad material 301G according to Example 6 includes copper member 302, aluminum member 303, and intermediate layer 304. In Example 6, no divided portion is formed in intermediate layer 304. In copper aluminum clad material 301G, the thickness of the coating layer (intermediate layer 304) after forging is 3.9 µm. In Example 6, the porosity was less than 15% at the interface between copper member 302 and intermediate layer 304 and at the interface between intermediate layer 304 and aluminum member 303, and the interfaces were in close contact, resulting in good joining results.

[0104] 19 is a scanning electron microscope photograph of Example 7. As shown in FIG. 19 , copper-aluminum clad material 301H according to Example 7 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has continuous portion 305 and dividing portion 306 formed therein. In copper-aluminum clad material 301H, the thickness of the coating layer (intermediate layer 304) after forging is 8.4 μm. In Example 7, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at dividing portion 306, all of which were in close contact, resulting in good joining results.

[0105] FIG. 20 is a scanning electron microscope photograph of Comparative Example 2. FIG. 21 is an enlarged photograph of FIG. 20. As shown in FIGS. 20 and 21, copper-aluminum clad material 301I according to Comparative Example 2 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301I, the thickness of the coating layer (intermediate layer 304) after forging is 14.9 μm. In Comparative Example 2, a plurality of voids Q were observed at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306. The porosity at the interface between the continuous portion 305 and the aluminum member 303 and the porosity at the interface between the copper member 302 and the aluminum member 303 in the dividing portion 306 were less than 15%, indicating adhesion, but the porosity at the interface between the copper member 302 and the continuous portion 305 was 21%, indicating no adhesion, and the joining results were poor.

[0106] As described above, in Case 2 of Test 1 (Examples 4 to 7, Comparative Example 2), electroplating with Ni was performed in the coating process. When the thickness of the coating layer before forging was 4.7 to 10.5 μm, good joining results were obtained. However, when the thickness was 16.4 μm, defects occurred, resulting in poor joining results. In other words, if the coating layer is too thick, it is presumed that the coating layer cannot follow the deformation of the copper member 302 and the aluminum member 303, resulting in the formation of voids at the interface. Furthermore, it was found that the forging process reduces the thickness of the intermediate layer (coating layer) compared to before forging. Furthermore, it was found that the forging process in Examples 4, 5, and 7 reduces the thickness of the intermediate layer (coating layer) and also forms a dividing portion 306. On the other hand, it was found that the forging process in Example 6 reduces the thickness of the intermediate layer (coating layer), but does not form a dividing portion. In other words, even if a dividing portion is not formed in the intermediate layer as in Example 6, the respective interfaces can be joined well.

[0107] Example 8, Comparative Examples 3 and 4 Fig. 22 is a scanning electron microscope photograph of Example 8. As shown in Fig. 22, copper-aluminum clad material 301J according to Example 8 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301J, the thickness of the coating layer (intermediate layer 304) after forging is 2.3 µm. In Example 8, the porosity was less than 15% at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306, all of which were in close contact, resulting in good joining results.

[0108] FIG. 23 is a scanning electron microscope photograph of Comparative Example 3. FIG. 24 is an enlarged photograph of FIG. 23. As shown in FIGS. 23 and 24, copper-aluminum clad material 301K according to Comparative Example 3 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301K, the thickness of the coating layer (intermediate layer 304) after forging is 3.9 μm. In Comparative Example 3, a plurality of point-like voids Q were observed at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306. The porosity at the interface between the continuous portion 305 and the aluminum member 303, and the porosity at the interface between the copper member 302 and the aluminum member 303 in the dividing portion 306 were less than 15%, indicating adhesion, but the porosity at the interface between the copper member 302 and the continuous portion 305 was 26%, indicating no adhesion, and the joining results were poor.

[0109] FIG. 25 is a scanning electron microscope photograph of Comparative Example 4. FIG. 26 is an enlarged photograph of FIG. 25. As shown in FIGS. 25 and 26, copper-aluminum clad material 301L according to Comparative Example 4 includes copper member 302, aluminum member 303, and intermediate layer 304. Intermediate layer 304 has a plurality of continuous portions 305 and a plurality of divided portions 306 formed therein. In copper-aluminum clad material 301L, the thickness of the coating layer (intermediate layer 304) after forging is 5.4 μm. In Comparative Example 4, a plurality of point-like voids Q were observed at the interface between copper member 302 and continuous portion 305, the interface between continuous portion 305 and aluminum member 303, and the interface between copper member 302 and aluminum member 303 at divided portion 306. The porosity at the interface between the continuous portion 305 and the aluminum member 303 and at the interface between the copper member 302 and the aluminum member 303 in the dividing portion 306 was less than 15%, indicating adhesion, but the porosity at the interface between the copper member 302 and the continuous portion 305 was 26%, indicating no adhesion, and the joining results were poor.

[0110] As described above, in Case 3 of Test 1 (Example 8, Comparative Examples 3 and 4), electroplating with Ni—Cr was performed in the coating process. When the thickness of the coating layer before forging was 4.9 μm, good joining results were obtained. However, when the thickness was 5.9 to 6.5 μm, defects occurred, resulting in poor joining results. In other words, if the coating layer was too thick, it is presumed that the coating layer could not follow the deformation of the copper member 302 and the aluminum member 303, resulting in the formation of voids at the interface. It was found that the forging process reduced the thickness of the intervening layer (coating layer) compared to before forging. Furthermore, it was found that the forging process in Example 8 reduced the thickness of the intervening layer (coating layer) and also formed a dividing portion 306.

[0111] REFERENCE SIGNS LIST 1 copper aluminum clad material 2 copper member 3 aluminum member 3a new surface 4 intermediate layer 10 coating layer 10a new surface 20 laminate 30 heat sink 31 base 32 fin 101 copper aluminum clad material 102 copper member 103 aluminum member 103a new surface 104 intermediate layer 105 continuous portion 106 divided portion 110 coating layer 110a new surface

Claims

1. A method for producing a copper-aluminum clad material, in which a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are forged together to produce a clad material, the method comprising: a lamination process in which the copper member is provided with a coating layer, which is formed of a metal material in close contact with the aluminum member and which suppresses the generation of oxides, on a surface of the copper member that faces the aluminum member, and the coating layer and the aluminum member are laminated together to form a laminate in a state in which the coating layer and the aluminum member face each other; and a forging process in which the laminate is forged together by hot forging, the forging process being characterized in that a new surface of the coating layer and a new surface of the aluminum member are bonded in close contact with each other while the copper member and the coating layer are in close contact with each other.

2. A method for producing a copper-aluminum clad material as set forth in claim 1, wherein in the forging process, the coating layer is divided to form a divided portion between the divided coating layers where the coating layer is not present, and the aluminum member is caused to flow into the divided portion, thereby bringing a new surface of the copper member exposed at the divided portion into close contact with the new surface of the aluminum member, thereby joining the copper member and the aluminum member.

3. The method for producing a copper-aluminum clad material according to claim 1, wherein the metal material is at least one metal selected from the group consisting of titanium, vanadium, chromium, manganese, cobalt, nickel, molybdenum, rhodium, palladium, silver, platinum, and gold, or an alloy thereof.

4. The method for producing a copper-aluminum clad material according to claim 1, further comprising a coating step of forming the coating layer on the copper member.

5. The method for producing a copper-aluminum clad material according to claim 4, wherein the coating layer is a plating layer, and in the coating step, the plating layer is formed by subjecting the copper member to a plating treatment.

6. The method for producing a copper-aluminum clad material according to claim 5, wherein the plating treatment is Ni electric plating, electroless Ni-P plating, or Ni-Cr electric plating.

7. The method for producing a copper-aluminum clad material according to claim 5, wherein the plating layer has a thickness of 15 μm or less.

8. The method for producing a copper aluminum clad material according to claim 1, further comprising a heating step of preheating the laminate in an atmospheric atmosphere, wherein in the forging step, the laminate preheated in the heating step is hot forged in an atmospheric atmosphere.

9. A method for manufacturing a heat sink, which comprises carrying out the method for manufacturing a copper aluminum clad material according to any one of claims 1 to 8 while forming fins on the aluminum member, characterized in that in the forging step, hot forging is carried out on the laminate to forge and join the laminate, and fins are formed on the aluminum member.

10. A method for manufacturing a heat sink, comprising the steps of: carrying out the method for manufacturing a copper-aluminum clad material according to any one of claims 1 to 8; and then carrying out a cutting fin formation process for forming fins by subjecting the aluminum member to a cutting process.

11. A copper-aluminum clad material in which a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are bonded together, characterized in that the copper member and the aluminum member are bonded together with an intervening layer made of a metal material, the copper member and the intervening layer are in close contact with each other, and the intervening layer and the aluminum member are in close contact with each other and bonded together, and the intervening layer has a thickness of 10 μm or less.

12. The copper-aluminum clad material according to claim 11, wherein the intermediate layer has a continuous portion where the intermediate layer is present and a divided portion where the intermediate layer is not present, one surface of the continuous portion is closely joined to the copper member and the other surface of the continuous portion is closely joined to the aluminum member, and at the divided portion, the copper member exposed from the intermediate layer and the aluminum member are closely joined to each other.

13. The copper aluminum clad material according to claim 11, wherein the metallic material comprises nickel.

14. A heat sink comprising a copper-aluminum clad material in which a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are bonded together, the aluminum member having fins formed thereon, the copper member and the aluminum member are bonded together with an intervening layer made of a metal material, the copper member and the intervening layer are in close contact with each other, and the intervening layer and the aluminum member are in close contact with each other, and the intervening layer has a thickness of 10 μm or less.

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