Sheet material, joined body, sheet material joining method, and sheet material manufacturing method

Abstract

To provide a plate material onto which a laser beam by which welding can be performed can be outputted in a wider range so that welding can be executed stably, a jointed body in which the plate material is jointed to a plate material to be jointed, a jointing method for a plate material, and a manufacturing method for a plate material.SOLUTION: A plate material 11 made of copper or copper alloy, which is overlapped with a member 13 to be jointed made of copper or copper alloy and is subjected to laser welding, has, at least in a portion, a roughened surface 21, where an arithmetic average mean roughness Ra of the roughened surface is equal to 4 μm or more and maximum height roughness Rz thereof is 20 μm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a plate material, a joined body, a method for joining plate materials, and a method for manufacturing a plate material.

[0002] For example, when joining copper alloy plates to produce a heat dissipation member such as a vapor chamber or an electronic component, the copper alloy plates are often joined by brazing or caulking. However, these joining methods have the disadvantages of low productivity and high equipment costs. On the other hand, according to a joining method of laser welding copper alloy plates, high-speed welding is possible and high productivity can be obtained.

[0003] Patent Document 1 discloses a vapor chamber in which a light beam is irradiated from one plate-like member side of a container having a cavity portion and the outer peripheral portion is sealed by welding. The other plate-like member of the container has a large plate thickness so that the light beam does not penetrate in the plate thickness direction, thereby reducing the energy density of the light beam and suppressing the heat generated during welding. As a result, it is described that the distortion of the container is reduced and the generation of pinholes in the molten portion can be prevented.

[0004] Further, Patent Document 2 discloses that a surface layer made of a metal material such as nickel, which has a high absorption rate of laser light and a higher breaking strength than the metal material, is formed on one surface of the metal members overlapped with each other, and by irradiating laser light from above the surface layer, a re-solidified portion is formed from the surface of the surface layer to the inside of the metal member to join both metal members.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Laser welding can achieve high productivity because it can weld at high speed, and there is an increasing interest in it as a joining method for sealing the gaps between plate materials. By the way, copper or copper alloy plates used for heat dissipation members and the like are required to be thinned, for example, to a total thickness of 0.3 mm or less, from the viewpoint of miniaturization and weight reduction. Further, as a characteristic of copper, it is known that the absorption rate of laser light is low in the solid state and rapidly increases when it becomes in the molten state. Therefore, when joining copper or copper alloy plates by laser welding, the molten pool is unstable and defects such as blow holes are likely to occur. In particular, defects such as melting away may occur in thin plate materials.

[0007] When laser welding thin copper or copper alloy plates as in Patent Document 1, simply increasing the thickness of a part of the plate thickness or forming a surface layer on the laser light irradiation surface as in Patent Document 2 cannot sufficiently suppress the occurrence of defects such as blow holes and melting away. Moreover, in Patent Document 1, since the plate thickness in the molten part of the other plate-like member is increased, the weight increases. Further, in Patent Document 2, it is difficult to join members on which a surface layer cannot be plated.

[0008] Therefore, an object of the present invention is to provide a plate material capable of expanding the output range of laser light suitable for welding and stably welding, a joined body in which this plate material is joined to a member on the joined side, a method for joining plate materials, and a method for manufacturing plate materials.

Means for Solving the Problems

[0009] The present invention has the following configuration. (1) A plate material made of copper or a copper alloy that is superposed on a member on the joined side made of copper or a copper alloy and is laser welded, having a surface roughened at least in part, wherein the roughened surface has an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more, the plate material. (2) A joined body including the plate material according to (1) and a member on the joined side joined to the plate material. (3) Overlay the plate material described in (1) on the member to be joined, A method for joining a plate material, which comprises irradiating laser light along the roughened surface formed on the plate material to laser-weld the plate material to the member to be joined. (4) A method for manufacturing a plate material made of copper or a copper alloy, which is overlaid on a member to be joined made of copper or a copper alloy and laser-welded, A method for manufacturing a plate material, which comprises forming a roughened surface having an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more on an irradiated portion irradiated with laser light during laser welding by rolling or pressing. [Advantages of the Invention]

[0010] According to the present invention, when laser-welding copper or copper alloys to each other, the output range of laser light suitable for welding can be expanded, and stable welding can be performed. [Brief Description of the Drawings]

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view schematically showing a state of laser welding a plate material 11 and a member 13 on the side to be joined.

[0013] The plate material 11 according to the present embodiment is joined to the member 13 on the side to be joined by laser welding. The member 13 on the side to be joined shown here is also referred to as "the plate material on the side to be joined" for the purpose of explaining it as a plate material of the same material as the plate material 11. A part of each of the plate material 11 and the plate material 13 on the side to be joined overlaps with each other, and the overlapping part becomes the irradiated portion 15 of the laser beam L. Then, when the laser beam L is irradiated to this irradiated portion 15 by the laser irradiation device 100, the plate material 11 and the plate material 13 on the side to be joined are laser welded. The laser beam L is irradiated to at least a part of the above-described irradiated portion 15 and does not protrude from the irradiated portion 15.

[0014] The plate material 11 and the plate material 13 on the side to be joined are made of copper or a copper alloy. In the case of a copper alloy, components contained in copper (Cu) include tin (Sn), nickel (Ni), zinc (Zn), magnesium (Mg), phosphorus (P), or the like. The plate material 11 and the plate material 13 on the side to be joined shown here are thin plates with a thickness of 0.10 mm to 1.0 mm, and the plate thicknesses of the plate material 11 and the plate material 13 on the side to be joined may be equal, or either one may be thicker than the other.

[0015] The plate material 11 has a surface 21 that is roughened at least in part. In the present embodiment, a roughened surface 21 is formed at a position corresponding to the irradiated portion 15 of the plate material 11. The roughened surface 21 is formed along the scanning direction A of the laser beam and is preferably formed in the entire region of the irradiated portion 15. The shape and size of the range in which the roughened surface 21 is formed are not particularly limited. The roughened surface 21 may be formed at least in part of the plate material 11, and in the present embodiment, it may be formed in the irradiated portion 15.

[0016] As the laser irradiation device 100 for irradiating the irradiated portion 15 with the laser beam L, an example is a device equipped with a galvanometer scanner unit. In the laser irradiation device 100 equipped with a galvanometer scanner unit, the laser from the fiber laser oscillator is reflected by the galvanometer mirror, condensed by the lens, and irradiated onto the irradiated portion 15. According to this laser irradiation device 100, by controlling the angle of the galvanometer mirror attached to the rotation axis, the laser beam L can be scanned at high speed and with high precision. However, the laser irradiation device 100 is not limited to this, and other types of irradiation devices may also be used.

[0017] Next, the procedure of the joining method for laser-welding the plate material 11 and the plate material 13 on the joined side according to the present embodiment will be described.

[0018] (Roughening treatment) First, a roughened surface 21 is formed on the plate material 11. The roughened surface 21 can be formed, for example, by press working using a general press die. In this case, the press die has a roughened surface equivalent to the roughened surface 21 to be formed, and by pressing the plate material 11 against this press die, a roughened surface is transferred to at least a part of the plate material 11 as the surface 21. Also, the roughened surface 21 can be formed by rolling processing such as rolling a roller having irregularities formed on the surface by sandblasting or the like on the surface of the plate material 11. The roughening method of the surface 21 shown here is an example, and the roughening method is not particularly limited.

[0019] The roughened surface 21 is processed so that the arithmetic mean roughness Ra is 4 μm or more and the maximum height roughness Rz is 20 μm or more. The arithmetic mean roughness Ra and the maximum height roughness Rz are values compliant with JIS B 0601 etc. By the arithmetic mean roughness Ra being 4 μm or more and the maximum height roughness Rz being 20 μm or more, it can be said that unevenness with undulations having a size equal to or more than a predetermined value is averagely included over the entire surface of the roughened surface 21.

[0020] (Laser welding) Next, the plate material 11 with the roughened surface 21 formed thereon is superposed on the plate material 13 on the side to be joined. Then, the laser beam L emitted from the laser irradiation device 100 is scanned from one end 15a to the other end 15b of the irradiated portion 15 of the plate material 11 superposed on the plate material 13 on the side to be joined. As a result, the laser beam L is irradiated to the irradiated portion 15 along the scanning direction A, and a bead 23 formed by laser welding of the plate material 11 and the plate material 13 on the side to be joined is formed.

[0021] When laser welding is performed with the laser beam L of the laser irradiation device 100, the irradiated portion of the laser beam L in the joint portion (irradiated portion 15) between the plate material 11 and the plate material 13 on the side to be joined melts, and from the irradiation surface side to the back surface of the plate material 13 on the side to be joined opposite to the irradiation side of the laser beam L melts. By cooling and solidifying and hardening this melted portion, the bead 23 is continuously formed along the scanning direction A. As a result, a joined body 25 in which the plate material 11 and the plate material 13 on the side to be joined are well joined is obtained.

[0022] As described above, the plate material 11 of this configuration has a surface 21 that is roughened at least in part. In this roughened surface 21, the absorption rate of the laser beam L increases, and compared with the case where it is not roughened, the portion of the irradiated portion 15 can be melted with a lower power of the laser beam L. Therefore, the output range of the laser beam suitable for welding is widened, and more stable welding can be performed. As a result, while sufficiently suppressing the occurrence of defects such as blowholes and melting drops, the plate material and the plate material on the side to be joined can be surely joined by smoothly performing laser welding. In addition, high-quality laser welding is possible even at low output, and the degree of freedom in selecting equipment can be improved.

[0023] Here, the increase in the absorption rate of the laser beam L can be speculated as follows. In copper or copper alloys, the absorption rate of laser light in the solid state is as low as 5% or less, but when it becomes molten, it rapidly increases to several tens of percent or more. Therefore, once melted, the molten pool becomes unstable, and defects such as sputtering and blowholes are likely to occur, and in thin plates, melting and dropping are likely to occur. However, by forming the surface 21 roughened in advance on the plate material 11 as described above and irradiating the laser light L onto the surface 21, rapid melting is suppressed. That is, in this configuration, in the irradiation range of the laser light L, by having a roughness with minute irregularities on the surface of the plate material 11, thin portions with minute protruding irregularities are mixed and arranged. As a result, the heat input within the irradiation region of the laser light L starts to melt from the thin portions by heat conduction, and the heat is conducted toward the periphery of the formed molten pool. As a result, a wider range than the laser irradiation region is heated. In the molten portion, the energy absorption of the laser light L increases, but combined with heat diffusion to the surroundings, the rapid progress of melting is suppressed. Therefore, melting starts even when the output of the laser light L is low, and even when the output is high, excessive heat input is suppressed by the heat diffusion of the portion where melting started first. In this way, the output range of the laser light suitable for welding can be expanded.

[0024] Also, by providing the roughened surface 21 extending in the scanning direction A of the laser light, continuous laser welding can be performed along the roughened surface 21. As a result, a high-quality joined body 25 in which the plate material 11 and the plate material 13 on the joined side are joined by a uniform bead 23 is obtained. Also, the plate material 11 and the plate material 13 on the joined side can be joined well while suppressing melting and dropping. Furthermore, due to the formation of the continuous bead 23, high sealing performance is exhibited at the joint surface.

[0025] The manufacturing process of the above-described plate material 11 includes a process of forming a roughened surface 21 having an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more on the irradiated portion for irradiating the laser light L during laser welding by rolling or pressing.

[0026] According to the manufacturing method of this plate material 11, by forming the roughened surface 21 through rolling or pressing, manufacturing lines including general rolling and pressing can be diverted, enabling manufacturing with reduced production costs. Note that the roughening treatment may also be performed by other methods such as etching.

Example

[0027] Figure 2 is an explanatory diagram showing magnified photographs and surface roughness of the roughened surface 21 in the plate materials 11 of Test Examples 1 to 4. The magnified photograph and surface roughness of Test Example 1 show the results for the plate material 11 in a mirror-like state without surface roughening. The plate material 11 is a thin copper alloy plate with a thickness of 0.2 mm, and the welding speed is 10 mpm.

[0028] The roughened surface of Test Example 2 shows a fine dull pattern, the roughened surface of Test Example 3 shows a thick dull pattern, and the roughened surface of Test Example 4 shows a convex circular mark pattern.

[0029] The roughened surface of each test example can be formed, for example, by rolling, pressing, etc. The roughened surfaces of Test Example 2 and Test Example 3 were formed by transferring the shape of the roller surface with adjusted surface roughness. Also, the roughened surface of Test Example 4 was formed by providing minute circular recesses on the roller surface and transferring that shape.

[0030] Furthermore, Figure 2 also shows the arithmetic mean roughness Ra and the maximum height roughness Rz of each test example. The arithmetic mean roughness Ra and the maximum height roughness Rz will be described later.

[0031] Figure 3 is a graph showing the output range of the laser light capable of welding when joining the plate material 11 of each test example to the plate material 13 on the side to be joined. On the other hand, Figure 4 shows a graph of the arithmetic mean roughness Ra and the maximum height roughness Rz of each test example shown in Figure 2.

[0032] Figure 3 shows that in Test Examples 2 to 4, the output range of the laser beam suitable for welding is expanded particularly on the low-output side compared to Test Example 1. That is, the plate material 11 having the roughened surface 21 can be joined even with a laser beam at a lower output level than the plate material having no roughened surface 21. Particularly in Test Example 2, the output range of the laser beam suitable for welding was expanded about 1.5 times compared to Test Example 1.

[0033] Figure 4 shows the arithmetic mean roughness Ra and the maximum height roughness Rz of each test example. Test Examples 2 to 4 have a larger arithmetic mean roughness Ra and maximum height roughness Rz than Test Example 1. From this, it is presumed that the absorption rate of the laser beam L is increased in the portion of the roughened surface 21. Thereby, even a laser beam at a low output level can melt the portion of the irradiated portion 15, so that the output range of the laser beam suitable for welding is widened and stable welding work becomes possible.

[0034] As described above, the roughened surface 21 can increase the absorption rate of the laser beam L by having an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more. Further, the arithmetic mean roughness Ra is preferably 10 μm or less, and the maximum height roughness Rz is preferably 35 μm or less. By setting the arithmetic mean roughness Ra and the maximum height roughness Rz within the above ranges, the output range of the laser beam suitable for welding can be surely widened particularly on the low-output side.

[0035] Here, regarding defining the surface roughness of the roughened surface 21 by both the arithmetic mean roughness Ra and the maximum height roughness Rz, there are the following reasons. When the arithmetic mean roughness Ra has a predetermined value, there are irregularities on the surface. However, since the arithmetic mean roughness Ra is an averaged value over the entire surface to be calculated, the convexities larger than the average value and the concavities lower than the average value may cancel each other out and the value may become small. Therefore, by adding the condition of the maximum height roughness Rz, the condition of the minimum irregularities that scatter the laser light over the entire surface is ensured. However, if the arithmetic mean roughness Ra and the maximum height roughness Rz are too large, it may be difficult to obtain good joining depending on the state of the plate surface. Therefore, it is preferable that the upper limit of the arithmetic mean roughness Ra is 30 μm and the upper limit of the maximum height roughness Rz is 100 μm.

[0036] FIG. 5 shows an enlarged photograph of the irradiated portion when irradiated with a laser beam having an output exceeding 2.6 kW. When irradiating with a laser beam having an output larger than the output range of the laser beam suitable for welding shown in FIG. 3, in the irradiated portion, both the plate material 11 and the plate material 13 on the joined side are melted and dropped.

[0037] FIG. 6 shows an enlarged photograph of the irradiated portion when irradiated with a laser beam having an output less than 1.8 kW. When irradiating with a laser beam having an output smaller than the output range of the laser beam suitable for welding shown in FIG. 3, in the irradiated portion, the laser beam does not penetrate the plate material 13 on the joined side, and sufficient joining strength cannot be obtained.

[0038] Also, laser welding performed by scanning the laser beam can select at least any one of linear welding, spot welding, and screw welding. Laser welding may be spot welding in which the laser beam from the laser irradiation device 100 is irradiated while being scanned linearly or curvilinearly as shown in FIG. 1, or the laser beam is stopped at a predetermined position and irradiated. Further, laser welding may be screw welding in which the laser beam is irradiated while being scanned in a spiral shape, circular shape, triangular shape, etc. Such a scanning pattern of the laser beam can be appropriately selected according to the types of the plate material 11 and the plate material 13 on the joined side, the size and shape of the irradiated portion 15, and the joining mode.

[0039] The beam spot diameter of the laser light used here is preferably 0.1 mm to 0.7 mm, and particularly preferably 0.3 mm. When the beam spot diameter is within this range, the effects of preventing the above-mentioned melting and dropping and incomplete penetration of the laser light become remarkable. Also, the welding speed is preferably 2 mpm to 20 mpm.

[0040] Thus, the present invention is not limited to the above-described embodiments, and it is also contemplated by the present invention that those skilled in the art can combine each configuration of the embodiments with each other, make changes, and apply based on the description in the specification and well-known techniques, and it is included in the scope for which protection is sought.

[0041] For example, the joined member 13 on the joined side is not limited to a thin plate, and may be a thick member. Even in that case, by providing a roughened surface on the plate material to be joined, the output of the laser light can be spread to the low-output side.

[0042] As described above, the following matters are disclosed in this specification. (1) A plate material made of copper or a copper alloy that is superposed on a joined member made of copper or a copper alloy and is laser welded, having a surface roughened at least in part, wherein the roughened surface has an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more, plate material. According to this plate material, since the absorption rate of the laser light is increased at the roughened surface portion of the plate material, the irradiated portion can be melted even with a lower output of the laser light compared to the case where it is not roughened. As a result, the output range of the laser light that can be welded is widened, and stable welding work becomes possible.

[0043] (2) The plate material according to (1), wherein the roughened surface is formed along the scanning direction of the laser light. (1) The plate material according to (1). According to this plate material, by forming a roughened surface along the scanning direction of the laser beam, laser welding can be continuously performed along the roughened surface. Thereby, a homogeneous and continuous bead is formed, and high-quality joining can be achieved. Further, high sealing performance is exhibited at the joining surface.

[0044] (3) The plate material according to (1) or (2), wherein the arithmetic mean roughness Ra is 10 μm or less. According to this plate material, the output range suitable for welding can be surely expanded to the low-output side.

[0045] (4) The plate material according to any one of (1) to (3), wherein the maximum height roughness Rz is 35 μm or less. According to this plate material, the output range suitable for welding can be surely expanded to the low-output side.

[0046] (5) A joined body including the plate material according to any one of (1) to (4) and a member to be joined joined to the plate material. According to this joined body, by laser-welding the plate material and the member to be joined on the roughened surface, a joined body in which the plate material and the member to be joined are joined with high quality can be obtained.

[0047] (6) A method for joining a plate material, comprising overlapping the plate material according to any one of (1) to (4) on a member to be joined, and irradiating laser light along the roughened surface formed on the plate material to laser-weld the plate material to the member to be joined. According to this method for joining a plate material, the plate material and the member to be joined can be satisfactorily joined while suppressing melting.

[0048] (7) The method for joining a plate material according to (6), wherein the laser welding is at least any one of linear welding, spot welding, and screw welding. According to this method for joining a plate material, an optimal laser welding can be selected according to the joining mode.

[0049] A method for manufacturing a plate made of copper or a copper alloy, which is superposed on a member to be joined made of copper or a copper alloy and is laser-welded, forming a roughened surface with an arithmetic mean roughness Ra of 4 μm or more and a maximum height roughness Rz of 20 μm or more on an irradiated portion irradiated with laser light during laser welding by rolling or pressing, method for manufacturing a plate. According to this method for manufacturing a plate, a manufacturing line including general rolling and pressing can be diverted, and manufacturing with reduced manufacturing costs becomes possible.

Explanation of symbols

[0050] 11 Plate 13 Member to be joined 15 Irradiated portion 21 Roughened surface 23 Bead 25 Joined body 100 Laser irradiation device A Scanning direction L Laser light

Claims

1. A plate made of copper or a copper alloy that is superposed on a member to be joined made of copper or a copper alloy and is laser welded, having a plate thickness of 0.10 mm to 1.0 mm, having a surface roughened on an irradiated portion irradiated with laser light during laser welding, wherein the roughened surface is a processed surface formed by transferring the shape of a roller surface by rolling with a roller having irregularities, and the arithmetic mean roughness Ra is 4 μm or more and 10.44 μm or less, and the maximum height roughness Rz is 20 μm or more and 35 μm or less, plate.

2. The roughened surface is formed along the scanning direction of the laser light, The plate according to claim 1.

3. The arithmetic mean roughness Ra is 10 μm or less, The plate according to claim 1.

4. A joined body comprising the plate according to any one of claims 1 to 3 and a member to be joined joined to the plate. Joined body.

5. Superpose the plate according to any one of claims 1 to 3 on a member to be joined, Irradiate laser light along the roughened surface formed on the plate to laser weld the plate to the member to be joined, Method for joining plates.

6. The laser welding is at least any one of seam welding, spot welding, and screw welding, Method for joining plates according to claim 5.

7. A method for manufacturing a plate made of copper or a copper alloy that is superposed on a member to be joined made of copper or a copper alloy and is laser welded, wherein the plate thickness of the plate is 0.10 mm to 1.0 mm, On the irradiated portion irradiated with laser light during laser welding, a roughened surface with an arithmetic mean roughness Ra of 4 μm or more and 10.44 μm or less and a maximum height roughness Rz of 20 μm or more and 35 μm or less is formed by transferring the shape of the roller surface by rolling with a roller having irregularities, Method for manufacturing a plate.

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