Copper plate and conjugate

Abstract

To provide a copper plate suitable for laser processing and laser welding, by sufficiently improving a light absorption rate of a wavelength in an infrared region.SOLUTION: A Cu content is 99 mass% or more, the surface roughness Sdq (root mean square slope) is within the range of 0.05 to 0.50, and the surface roughness Sdr (developed interfacial area ratio) is within the range of 0.15% to 5.00%. In a cross-section perpendicular to the rolling width direction, the crystal grain size is 100 μm or less. The grain boundaries are classified as follows: those with an orientation difference of 2° to 15° between adjacent grains are low-angle grain boundaries; special grain boundaries (Σ3, 9, 27); and those with an orientation difference exceeding 15°(excluding special grain boundaries) are high-angle grain boundaries. The lengths of the low-angle grain boundaries (X), special grain boundaries (Y), and high-angle grain boundaries (Z) satisfy the condition (X+Z) / (X+Y+Z)>30%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper plate that has excellent laser light absorption properties and is suitable for laser processing and welding, and a joined body using this copper plate. [Background technology]

[0002] Conventionally, copper sheets made of highly conductive pure copper have been used as materials for electronic and electrical equipment components such as terminals, connectors, relays, switches, sockets, bus bars, lead frames, and heat sinks. In recent years, development of processes such as machining and welding using fiber lasers has been underway, and attempts have been made to perform laser machining on the above-mentioned copper plates.

[0003] However, copper has a low light absorption rate in the near-infrared wavelength range (near 1000 nm) used by fiber lasers, resulting in problems such as low processing efficiency. Furthermore, when copper melts and enters a liquid phase, its light absorption rate in the near-infrared wavelength range increases rapidly, resulting in unstable welding quality. In particular, copper materials with a Cu content of 99 mass% or more have low light absorption rate in the infrared wavelength range, making it difficult to perform stable laser processing and laser welding. It is possible to stably process and weld copper using a laser with a wavelength of around 500 nm (so-called blue or green laser) that has a high light absorption rate, but the equipment for blue or green lasers is more expensive than fiber lasers, which increases costs.

[0004] Therefore, Patent Document 1 proposes a method of improving the light absorptance of wavelengths in the infrared region by forming a white metal layer on a substrate made of copper or a copper alloy. Furthermore, Patent Document 2 proposes a method for improving laser weldability by controlling the surface roughness Rz (maximum height) and Ra (arithmetic mean height) of the copper material, and the surface glossiness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5537751 [Patent Document 2] Japanese Patent Publication No. 2023-032936 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 requires the formation of a white metal layer on a copper substrate, which poses a problem of increased costs. Furthermore, the method described in Patent Document 2 does not sufficiently improve the light absorptance of wavelengths in the near-infrared region, and further improvement in the light absorptance is desired.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a copper plate that has a sufficiently improved light absorptance in the infrared wavelength range and is suitable for laser processing and laser welding, and a bonded body that includes this copper plate. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors conducted extensive research and discovered that by controlling the structure as well as the shape of the material surface, it is possible to utilize the exothermic reaction that accompanies the change in structure for laser processing (laser welding) while improving the laser absorption, thereby enabling more efficient laser processing (laser welding).

[0009] The present invention has been made based on the above findings, and a copper plate according to a first aspect of the present invention has a Cu content of 99 mass% or more, a surface roughness Sdq (root mean square slope) in the range of 0.05 to 0.50, and a surface roughness Sdr (developed interface area ratio) in the range of 0.15 to 5.00%, and in a cross section perpendicular to the rolling width direction, the crystal grain size is 100 μm or less, and when crystal grain boundaries are defined as low-angle grain boundaries where the misorientation of adjacent crystal grains is 2° to 15° and special grain boundaries (Σ3,9,27), and high-angle grain boundaries where the misorientation of adjacent crystal grains is more than 15° (excluding special grain boundaries), the length X of the low-angle grain boundaries, the length Y of the special grain boundaries, and the length Z of the high-angle grain boundaries are (X+Z) / (X+Y+Z)>30% It is characterized in that the following is satisfied.

[0010] According to the copper plate of the first aspect of the present invention, the Cu content is set to 99 mass % or more, and therefore the copper plate has excellent electrical and thermal conductivity. Furthermore, the surface roughness Sdq (root mean square slope) is within the range of 0.05 to 0.50, and the surface roughness Sdr (developed interface area ratio) is within the range of 0.15% to 5.00%, so that the surface area for absorbing the laser can be secured and the number of times the laser is reflected can be increased, thereby improving the light absorption rate for wavelengths in the infrared region. Furthermore, in a cross section perpendicular to the rolling width direction, the grain size is 100 μm or less, and the length X of the low-angle grain boundary, the length Y of the special grain boundary, and the length Z of the high-angle grain boundary satisfy the above-mentioned formulas. Therefore, recrystallization can be performed quickly under low-temperature conditions using laser energy, and laser processing (laser welding) can be performed efficiently by utilizing the exothermic reaction that occurs during recrystallization.

[0011] The copper plate of the second aspect of the present invention is the copper plate of the first aspect of the present invention, characterized in that the Ag content is within the range of 5 massppm to 20 massppm. According to the copper sheet of the second aspect of the present invention, the Ag content is set to the range of 5 mass ppm to 20 mass ppm, so that the added Ag segregates near the grain boundaries, preventing the movement of atoms at the grain boundaries during the copper sheet manufacturing process, thereby enabling the crystal grain size to be refined, and thus promoting recrystallization by laser energy.

[0012] The copper plate of embodiment 3 of the present invention is characterized in that, in the copper plate of embodiment 1 or embodiment 2 of the present invention, it contains one or more elements selected from Mg, Zr, Ca, Ni, and Sn in a total amount ranging from 10 massppm to 1500 massppm. According to the copper plate of the third aspect of the present invention, one or more elements selected from Mg, Zr, Ca, Ni, and Sn are contained in a total amount ranging from 10 massppm to 1500 massppm, and therefore an oxide film of these elements is formed on the surface of the copper plate, which further improves the light absorptance of wavelengths in the infrared region.

[0013] The copper plate of a fourth aspect of the present invention is the copper plate of any one of the first to third aspects of the present invention, characterized in that the O concentration is 1000 mass ppm or less. According to the copper alloy of the fourth aspect of the present invention, the O concentration is limited to 1000 mass ppm or less, so that embrittlement of the copper plate during laser irradiation can be suppressed, and laser processing and laser welding can be performed more stably.

[0014] The copper plate of the fifth aspect of the present invention is the copper plate of any one of the first to fourth aspects of the present invention, characterized in that the thickness is in the range of 0.10 mm or more and 5 mm or less. According to the copper plate of the fifth aspect of the present invention, the thickness is set within the range of 0.10 mm or more and 5 mm or less, and therefore it is particularly suitable as a material for parts of electronic and electric devices.

[0015] A joined body according to a sixth aspect of the present invention is characterized in that the copper plate according to any one of the first to fifth aspects of the present invention is laser-welded to a material to be joined. According to the joined body of the sixth aspect of the present invention, the copper plates of any one of the first to fifth aspects of the present invention are laser welded, and therefore the weld quality is excellent. [Effects of the Invention]

[0016] It is possible to provide a copper plate that has a sufficiently improved light absorptance for wavelengths in the infrared region and is suitable for laser processing and laser welding, and a bonded body that includes this copper plate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a flow diagram of a method for manufacturing a copper plate according to an embodiment of the present invention. [Figure 2] FIG. 10 is an explanatory diagram showing a method for evaluating laser scratches in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0018] A copper plate according to one embodiment of the present invention will be described below. The copper plate of this embodiment is used as a material for electronic and electrical equipment components such as terminals, connectors, relays, switches, sockets, bus bars, lead frames, and heat sinks, and more specifically, is intended to be laser welded to other components to form electronic and electrical equipment components.

[0019] In the copper plate of this embodiment, the Cu content is 99 mass% or more, and the surface shape is controlled so that the surface roughness Sdq (root mean square slope) is in the range of 0.05 to 0.50, and the surface roughness Sdr (developed interface area ratio) is in the range of 0.15% to 5.00%. In the copper plate of this embodiment, the crystal grain size is 100 μm or less in a cross section perpendicular to the rolling width direction, and when the crystal grain boundaries are defined as low-angle grain boundaries where the misorientation between adjacent crystal grains is 2° or more and 15° or less, special grain boundaries (Σ3,9,27), and high-angle grain boundaries where the misorientation between adjacent crystal grains is more than 15° (excluding special grain boundaries), the length X of the low-angle grain boundaries, the length Y of the special grain boundaries, and the length Z of the high-angle grain boundaries are controlled to satisfy (X + Z) / (X + Y + Z) > 30%.

[0020] Here, in the copper plate of this embodiment, the Ag content is preferably within the range of 5 massppm to 20 massppm. Furthermore, the copper plate of this embodiment preferably contains one or more selected from Mg, Zr, Ca, Ni and Sn in a total amount in the range of 10 massppm to 1500 massppm.

[0021] Furthermore, in the copper plate of this embodiment, the O concentration is preferably 1000 mass ppm or less. Furthermore, the copper plate of this embodiment preferably has a thickness in the range of 0.10 mm to 5 mm.

[0022] The reasons for specifying the component composition, surface shape, crystal structure, and thickness of the copper plate of this embodiment as described above will be explained below.

[0023] (Cu) The Cu content is set to 99 mass% or more, ensuring high electrical and thermal conductivity, making it suitable as a material for electronic and electrical equipment parts. The Cu content is preferably 99.9 mass% or more, and more preferably 99.95 mass% or more.

[0024] (Ag) The trace amounts of Ag added to Cu segregate near the grain boundaries, preventing the movement of atoms at the grain boundaries and preventing the crystal grain size from coarsening during the copper sheet manufacturing process. This refines the crystal grain size in the copper sheet, further promoting recrystallization. Here, by setting the Ag concentration to 5 massppm or more, the above-mentioned effects can be achieved, while by setting the Ag content to 20 massppm or less, it is possible to suppress a decrease in conductivity and an increase in manufacturing costs. Therefore, in this embodiment, when Ag is contained, the Ag concentration is preferably set to 5 massppm or more and 20 massppm or less.

[0025] In order to reliably achieve a finer crystal grain size, the lower limit of the Ag content is more preferably 6 massppm or more, more preferably 7 massppm or more, and even more preferably 8 massppm or more. On the other hand, in order to further suppress a decrease in conductivity and an increase in manufacturing costs, the upper limit of the Ag content is more preferably 18 massppm or less, more preferably 16 massppm or less, and even more preferably 14 massppm or less.

[0026] (One or more selected from Mg, Zr, Ca, Ni, Sn) By including the easily oxidizable elements Mg, Zr, Ca, Ni, and Sn, an oxide film made of oxides of these elements is formed on the surface of the copper plate. This further improves the light absorption rate in the infrared wavelength range. On the other hand, if the copper plate contains a large amount of these elements, electrical and thermal conductivity may decrease. Therefore, in this embodiment, when Mg, Zr, Ca, Ni, and Sn are contained, it is preferable that the total content of one or more selected from Mg, Zr, Ca, Ni, and Sn is within the range of 10 massppm to 1500 massppm.

[0027] In order to reliably further improve the light absorptance of the oxide film at wavelengths in the infrared region, the lower limit of the total content of one or more selected from Mg, Zr, Ca, Ni, and Sn is more preferably 12 massppm or more, more preferably 15 massppm or more, and even more preferably 20 massppm or more. On the other hand, in order to reliably suppress a decrease in conductivity, the upper limit of the total content of one or more selected from Mg, Zr, Ca, Ni, and Sn is more preferably 1400 massppm or less, more preferably 1200 massppm or less, and even more preferably 1000 massppm or less.

[0028] (O concentration) If the amount of O (oxygen) contained in the copper plate is large, the copper plate may become embrittled when irradiated with a laser. For this reason, in this embodiment, it is preferable to limit the O concentration of the copper plate to 1000 mass ppm or less. The upper limit of the O concentration in the copper plate is more preferably 900 mass ppm or less, and even more preferably 800 mass ppm or less. There is no particular restriction on the lower limit of the O concentration in the copper plate.

[0029] (surface roughness) Sdq (root mean square slope), a parameter that indicates surface roughness, represents the average magnitude of the local gradient of the surface irregularities, i.e., the value equivalent to the differential of the shape. The larger Sdq, the steeper the surface. Here, by setting Sdq within the range of 0.05 to 0.50, it is possible to increase the number of times the laser is reflected on the surface.

[0030] Sdr (developed interface area ratio), a parameter indicating surface roughness, is an index that indicates the rate of increase in surface area. It can be calculated using the following formula from the surface area A1 of the contoured surface including the surface irregularities and the area A0 when that surface is projected onto the XY plane. Sdr = ((A1 / A0)-1) x 100(%) Here, by setting Sdr within the range of 0.15% to 5.00%, the surface area is sufficiently increased in accordance with the surface properties, and the surface area where laser absorption occurs can be increased.

[0031] By setting these surface roughness parameters Sdq (root mean square slope) and Sdr (developed interface area ratio) within the proposed ranges described above, it is possible to synergistically improve the laser light absorption performance (light absorptivity for wavelengths in the infrared region). The lower limit of Sdq is preferably 0.06 or more, more preferably 0.07 or more, and the upper limit of Sdq is preferably 0.48 or less, more preferably 0.46 or less. The lower limit of Sdr is preferably 0.16% or more, and more preferably 0.17% or more, and the upper limit of Sdr is preferably 4.9% or less, and more preferably 4.8% or less.

[0032] (crystal grain size) In the copper plate of this embodiment, recrystallization occurs due to the energy of the laser light, and the exothermic reaction of strain relief caused by this recrystallization is utilized. Here, when the crystal grain size in the cross section perpendicular to the rolling width direction is 100 μm or less, it is possible to cause recrystallization earlier and at a lower temperature using the energy of the laser light, and the exothermic reaction that occurs during recrystallization can be used for laser processing (laser welding), allowing for efficient laser processing (laser welding). The upper limit of the grain size in a cross section perpendicular to the rolling width direction is preferably 90 μm or less, and more preferably 80 μm or less. There is no particular lower limit to the grain size in a cross section perpendicular to the rolling width direction.

[0033] (grain boundary) As described above, in the copper plate of this embodiment, recrystallization occurs due to the energy of the laser light, and the exothermic reaction of strain relief caused by this recrystallization is utilized. Here, low-angle grain boundaries, where the misorientation of adjacent crystal grains is between 2° and 15°, and high-angle grain boundaries, where the misorientation of adjacent crystal grains is greater than 15° (excluding special grain boundaries), are crystal grain boundaries with higher energy than special grain boundaries. Therefore, by reducing the proportion of special grain boundaries, it becomes possible to cause recrystallization earlier and at lower temperatures, and the exothermic reaction that occurs during recrystallization can be used for laser processing (laser welding). Therefore, in the copper plate of this embodiment, the length X of the low-angle grain boundary, the length Y of the special grain boundary, and the length Z of the high-angle grain boundary satisfy (X+Z) / (X+Y+Z)>30%. It is preferable that (X+Z) / (X+Y+Z) is 32% or more, and more preferably 34% or more.

[0034] (Thickness) The copper plate of this embodiment is used to form electronic and electrical equipment components by laser processing (laser welding). Here, by setting the thickness of the copper plate within the range of 0.10 mm to 5 mm, it becomes possible to manufacture parts for electronic and electric devices satisfactorily by laser processing (laser welding). The lower limit of the thickness of the copper plate of this embodiment is more preferably 0.12 mm or more, and even more preferably 0.14 mm or more, while the upper limit of the thickness of the copper plate of this embodiment is more preferably 4.5 mm or less, and even more preferably 4 mm or less.

[0035] Next, an example of a method for producing a copper plate according to this embodiment will be described with reference to the flow chart shown in FIG.

[0036] (Melting and casting process S01) First, the aforementioned elements are added to the molten copper obtained by melting an oxygen-free copper raw material to adjust the composition, thereby producing a molten copper alloy. The various elements can be added as simple elements or master alloys. Alternatively, a raw material containing the aforementioned elements may be melted together with the copper raw material. Here, each element preferably has a purity of 99.9 mass% or more, known as 3N, or 99.99 mass% or more, known as 4N. In the melting process, in order to reduce the hydrogen concentration, atmospheric melting is preferably performed in an inert gas atmosphere (e.g., Ar gas) with a low HO vapor pressure, and the holding time during melting is preferably minimized. The molten copper alloy with the adjusted composition is then poured into a mold to produce an ingot. For mass production, continuous or semi-continuous casting is preferably used.

[0037] (Hot rolling process S02) The resulting ingot is then hot-rolled to introduce strain and deform the shape to the desired size. By introducing strain, high strain can be applied to the coarse crystals, which increases the homogeneity of the material. The total rolling reduction here requires a certain processing rate to destroy the cast structure, so the total rolling reduction must be 50% or more, preferably 55% or more, and more preferably 60% or more. Although the plastic processing method is not particularly limited, it is preferable to use rolling when the final shape is a plate or strip, extrusion or groove rolling when the final shape is a wire or rod, and forging or pressing when the final shape is a bulk shape. Although there are no regulations regarding the starting temperature of hot rolling, the maximum temperature during the final three passes of hot rolling must be 600°C or less. This makes it possible to make the grain size uniform and fine after hot rolling, and by combining this with the subsequent rolling and heat treatment processes, it becomes possible to obtain the desired crystal structure. After the hot rolling, it is preferable to perform facing to remove the oxide film formed during the hot rolling.

[0038] (Cold rolling process S03) Next, cold rolling is carried out. Here, the processing method is not particularly limited, but when the final form is a plate or strip, rolling is adopted. Alternatively, forging, pressing, or groove rolling may be adopted. The temperature is also not particularly limited, but -200 to 400°C is preferable. In addition, the total rolling reduction must be kept at 80% or less. If the total rolling reduction exceeds 80% in this cold rolling step S03, recrystallized grains having a (100) orientation are likely to be formed in the subsequent heat treatment step, and strain introduction in the subsequent rolling step may become non-uniform, making it difficult to obtain the desired structure. The total rolling ratio in the cold rolling step S03 is preferably 75% or less, and more preferably 70% or less.

[0039] (First heat treatment step S04) The material is heat-treated and water-quenched to homogenize and solubilize it. While the heat treatment method is not particularly limited, it is preferably performed in a non-oxidizing or reducing atmosphere. The heat treatment temperature is preferably 500°C or higher and 900°C or lower, more preferably 550°C or higher. Furthermore, to form a uniform structure, the heating rate is preferably 10°C / min or higher. The cold rolling step S03 and the first heat treatment step S04 may be carried out repeatedly.

[0040] (First wet rolling process S05) Next, wet rolling is performed under conditions of a rolling ratio of 20% or less. Wet rolling can reduce friction between the material surface and the rolling rolls. Rolling is performed in only one pass. The surface roughness Ra (arithmetic mean roughness) of the rolling roll surface is preferably in the range of 0.05 to 0.20. Dry rolling increases the friction between the material surface and the rolls, preventing proper transfer of the roll surface and worsening the surface roughness. By performing one pass of wet rolling on the softened material in the first heat treatment step S04, it is possible to transfer the surface shape of the roll to the material surface. Furthermore, by limiting the rolling ratio to 20% or less, it is possible to suppress recrystallization in the subsequent second heat treatment step.

[0041] (Second heat treatment step S06) To soften the material, the material is heat-treated and water-quenched. While there are no particular limitations on the heat treatment method, it is best to perform the heat treatment in a non-oxidizing or reducing atmosphere. The heat treatment temperature is preferably between 300°C and 500°C. Heat treatment at temperatures above 500°C can lead to rapid grain coarsening.

[0042] (Second wet rolling process S07) Next, wet rolling is performed at a predetermined rolling ratio. Wet rolling can reduce friction between the material surface and the rolling rolls. Rolling is performed in only one pass. The surface roughness Ra (arithmetic mean roughness) of the rolling roll surface is set to a range of 0.10 to 0.50. Here, the surface roughness Ra of the rolling roll surface in the second wet rolling step S07 is greater than the surface roughness Ra of the rolling roll surface in the first wet rolling step S05, with the difference being 0.05 or more. Here, the difference is preferably 0.07 or more, and more preferably 0.10 or more.

[0043] By performing one pass of wet rolling on the softened material in the second heat treatment step S06, it becomes possible to transfer the surface shape of the roll to the material surface. Also, by making the surface roughness Ra of the rolling roll surface in the second wet rolling step S07 larger than the surface roughness Ra of the rolling roll surface in the first wet rolling step S05, and by making the difference 0.05 or more, it becomes possible to form multiple types of irregularities on the surface of the material. If necessary, pickling and buffing may be performed after the second wet rolling step S07. By performing pickling and buffing, an oxide film on the surface can be removed.

[0044] The copper plate of this embodiment is manufactured through the above-described steps.

[0045] The joined body of this embodiment is formed by laser welding the copper plate obtained as described above to a material to be joined, and is used as a part for an electronic or electric device.

[0046] According to the copper plate of this embodiment configured as described above, the Cu content is 99 mass% or more, so it has excellent electrical and thermal conductivity and is suitable as a material for electronic and electrical device components. Furthermore, the surface roughness Sdq (root mean square slope) is within the range of 0.05 to 0.50, and the surface roughness Sdr (developed interface area ratio) is within the range of 0.15% to 5.00%, so that the surface area for absorbing the laser can be secured and the number of times the laser is reflected can be increased, thereby improving the light absorption rate for wavelengths in the infrared region. In the cross section perpendicular to the rolling width direction, the grain size is 100 μm or less, and the length X of the low-angle grain boundaries, the length Y of the special grain boundaries, and the length Z of the high-angle grain boundaries satisfy the above-mentioned formula. Since the proportion of special grain boundaries is low, recrystallization can be achieved quickly under low-temperature conditions using laser energy, and laser processing (laser welding) can be performed efficiently by utilizing the exothermic reaction that occurs during recrystallization.

[0047] In the copper sheet of this embodiment, when Ag is contained in the range of 5 mass ppm to 20 mass ppm, Ag segregates near the grain boundaries, which prevents the movement of atoms at the grain boundaries during the copper sheet manufacturing process (first heat treatment step S04 and second heat treatment step S06), thereby making it possible to refine the crystal grain size, and thus promoting recrystallization by laser energy.

[0048] In the copper plate of this embodiment, when one or more elements selected from Mg, Zr, Ca, Ni, and Sn are contained in a total amount ranging from 10 massppm to 1500 massppm, an oxide film of these elements is formed on the surface of the copper plate, thereby further improving the light absorptance of wavelengths in the infrared region. In the copper plate of this embodiment, when the O concentration is 1000 mass ppm or less, embrittlement of the copper plate during laser irradiation can be suppressed, and laser processing and laser welding can be performed more stably. In the copper plate of this embodiment, when the thickness is within the range of 0.10 mm or more and 5 mm or less, it is particularly suitable as a material for parts of electronic and electric devices.

[0049] According to the joined body of this embodiment, the copper plate of this embodiment is laser welded to the joined material, so the welding quality is excellent and it is possible to form high-quality parts for electronic and electrical equipment.

[0050] Although the copper plate and the joined body according to the embodiment of the present invention have been described above, the present invention is not limited thereto and can be appropriately modified within the scope of the technical idea of ​​the invention. In the above embodiment, an example of a method for manufacturing a copper plate has been described, but the method for manufacturing a copper plate is not limited to the one described in the embodiment and an existing manufacturing method may be appropriately selected for manufacturing the copper plate. [Example]

[0051] The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0052] A copper raw material consisting of oxygen-free copper with a purity of 99.9999 mass% was prepared and placed in a high-purity graphite crucible. It was then high-frequency melted in an atmospheric furnace with an Ar gas atmosphere. Various additive elements were added to the resulting molten copper using master alloys made from oxygen-free copper with a purity of 99.99 mass% or higher and each element with a purity of 99 mass% or higher, resulting in the composition shown in Table 1. The molten copper was then poured into a water-cooled copper mold to produce an ingot. The ingot measured approximately 25 mm thick, 70 mm wide, and 100 mm long. It was then faceted and cut to adjust the thickness as needed.

[0053] Next, copper plates having a thickness of 0.5 mm for the present invention and comparative examples were obtained by performing the hot rolling step, cold rolling step, first heat treatment step, first wet rolling step, second heat treatment step, and second wet rolling step under the conditions shown in Tables 2 and 3. In the first heat treatment step, a salt bath furnace was used, and a temperature rise rate of 10°C / min or more was ensured. The copper plates of the invention examples and comparative examples obtained as described above were evaluated as follows.

[0054] (Alloy composition) Measurement samples were taken from the resulting ingots and subjected to component analysis. Ag, Mg, Ca, Zr, Ni, and Sn were measured by inductively coupled plasma optical emission spectrometry, O was analyzed by infrared absorption spectrometry, and other elements were measured using a glow discharge mass spectrometer (GD-MS).

[0055] (surface roughness) Using a Hitachi High-Technologies scanning white light interference microscope (R5500HML-A150-AC), images were observed using a 5x objective lens, and the images were joined together to create an area of ​​4mm x 4mm or more. The roughness of the material surface was analyzed, and the developed interface area ratio Sdr and root mean square slope Sdq were determined.

[0056] (grain size and grain boundaries) After mechanical polishing using waterproof polishing paper and diamond abrasive grains, the specimen was polished using colloidal silica solution. Electron beam diffraction (EBSD) measurements were performed using Hitachi High-Technologies SU7000, EDAX / AMETEK Velocity Super, and APEX EBSD Ver. 2.9 with analysis software (EDAX / AMETEK OIM Analysis Ver. 8.6) at an electron beam acceleration voltage of 15 kV and a scanning electron microscope (TEM) of 10,000 μm. 2 The misorientation of each grain was analyzed for the above measurement area, excluding measurement points where the CI value was 0.1 or less at measurement intervals of 0.1 μm. Measurement points where the misorientation between adjacent measurement points was 15° or more were considered to be grain boundaries, and the grain size was calculated using the area fraction data analysis software OIM. Additionally, the ratio (X+Z) / (X+Y+Z) was calculated by defining the intervals between adjacent measurement points where the misorientation between them was between 2° and 15° as low-angle grain boundaries, the total length of the low-angle grain boundaries as X, the total length of the special grain boundaries (Σ3,9,27) as Y, and the intervals between measurement points (excluding special grain boundaries) where the misorientation between them was more than 15° as high-angle grain boundaries, the total length of the high-angle grain boundaries as Z.

[0057] (Laser mark size) As shown in Figure 2, a YAG laser welding machine (ML-2350AF manufactured by Amada Weld Tech) was used to irradiate the material surface with 50 J of laser light using a 0.6 mm optical fiber, creating a laser mark on the surface of the material. The laser light was incident at an angle of 75° to the direction perpendicular to the rolling direction on the rolled surface. The laser mark was observed with an optical microscope and its diameter was measured. The larger the laser mark, the higher the laser light absorption performance (light absorptivity in the infrared wavelength range). When laser light was irradiated, laser marks with a diameter of less than 0.4 mm were marked with an "x", those with a diameter of 0.4 mm or more but less than 0.55 mm were marked with an "o", and those with a diameter of 0.55 mm or more were marked with an "◎".

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] In Comparative Example 1, the surface roughness Sdq of the copper plate was 0.009 and Sdr was 0.050%, both of which were outside the range of the present invention, and the laser marks were evaluated as "X". In Comparative Example 2, the surface roughness Sdr of the copper plate was 0.128%, which was outside the range of the present invention, and the grain boundary length ratio (X+Z) / (X+Y+Z) was low at 28%, and the laser marks were evaluated as "×". In Comparative Example 3, the copper plate had a surface roughness Sdq of 0.049 and Sdr of 0.144%, both outside the range of the present invention, and the crystal grain size was large at 132 μm, resulting in an evaluation of the laser marks as "x". In Comparative Example 4, the crystal grain size of the copper plate was as large as 102 μm, and the crystal grain boundary length ratio (X+Z) / (X+Y+Z) was as low as 29%, resulting in an evaluation of the laser marks as "poor."

[0063] In Comparative Example 5, the surface roughness Sdq of the copper plate was 0.046, which was outside the range of the present invention, and the laser marks were evaluated as "X". In Comparative Example 6, the surface roughness Sdq of the copper plate was 0.049, which was outside the range of the present invention, and the laser marks were evaluated as "x". In Comparative Example 7, the surface roughness Sdq of the copper plate was 0.510 and Sdr was 5.030%, both of which were outside the range of the present invention, and the laser marks were evaluated as "X".

[0064] In contrast, in Examples 1 to 16 of the present invention, the surface roughness Sdq, Sdr of the copper plate, the grain size, and the grain boundary length ratio (X+Z) / (X+Y+Z) were within the range of the present invention, and the laser marks were evaluated as "○" or "◎".

[0065] As described above, it was confirmed that the present invention can provide a copper plate that is suitable for laser processing and laser welding, with a sufficiently improved light absorptance in the infrared wavelength region.

Claims

1. The Cu content is 99 mass% or more, The surface roughness Sdq (root mean square slope) is in the range of 0.05 to 0.50, and the surface roughness Sdr (developed interface area ratio) is in the range of 0.15% to 5.00%, In a cross section perpendicular to the rolling width direction, the crystal grain size is 100 μm or less, and crystal grain boundaries are defined as low-angle grain boundaries where the misorientation of adjacent crystal grains is 2° or more and 15° or less, special grain boundaries (Σ3,9,27), and high-angle grain boundaries where the misorientation of adjacent crystal grains is more than 15° (excluding special grain boundaries), and the length X of the low-angle grain boundaries, the length Y of the special grain boundaries, and the length Z of the high-angle grain boundaries are (X+Z) / (X+Y+Z)>30% A copper plate characterized by satisfying the above.

2. 2. The copper plate according to claim 1, wherein the Ag content is in the range of 5 ppm by mass to 20 ppm by mass.

3. The copper plate according to claim 1, characterized in that it contains one or more elements selected from Mg, Zr, Ca, Ni, and Sn in a total amount of 10 ppm by mass or more and 1500 ppm by mass or less.

4. 2. The copper plate according to claim 1, wherein the O concentration is 1000 mass ppm or less.

5. 2. The copper plate according to claim 1, wherein the thickness is in the range of 0.10 mm to 5 mm.

6. A joined body, characterized in that the copper plate according to any one of claims 1 to 5 is laser-welded to a workpiece.

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