Copper alloy, copper alloy plastic processing material, component for electronic and electrical equipment, component for flexible device, heat dissipation component, and metal sealing material

Abstract

A copper alloy according to the present invention has a composition comprising 15-57 mass% of Zn and 12 mass% or less of Al, with the remainder being Cu and inevitable impurities, and when the content of Zn is denoted by A mass% and the content of Al is denoted by B mass%, the composition satisfies A+5×B ≥ 30 and A+3.5×B ≤ 57. A volume fraction of a β-phase is 50% or more, and when a measurement area of 8 mm2 or more is measured at a measurement interval of 8 μm steps by an EBSD method and analyzed except at measurement points at which an CI value analyzed by data analysis software OIM is 0.1 or less, and a boundary between measurement points at which an orientation difference between adjacent measurement points is 5º or greater is defined as a crystal grain boundary, the ratio of each corresponding grain boundary length of 3 ≤ Σ ≤ 29 to all crystal grain boundary lengths L where the measured β-phases contact each other is 4% or more. The copper alloy has excellent conductivity, has a low Young's modulus and a sufficiently large elastic deformation amount, and does not easily undergo plastic deformation even when subjected to large deformation.

Description

Copper alloys, copper alloy plastic processing materials, electronic and electrical equipment parts, flexible device parts, heat dissipation parts, metal sealing materials

[0001] The present invention relates to a copper alloy suitable for, for example, home appliances, semiconductor components such as lead frames, printed wiring boards, heat sinks, switch components, bus bars, connectors, and other electrical and electronic equipment components, as well as to a copper alloy plastically processed material made of this copper alloy, electronic and electrical equipment components, flexible device components, heat dissipation components, and metal sealing materials. This application claims priority based on Japanese Patent Application No. 2023-193585 filed in Japan on November 14, 2023, the contents of which are incorporated herein by reference.

[0002] Conventionally, copper or copper alloys having excellent electrical and thermal conductivity have been used for electronic and electrical equipment components such as terminals, bus bars, lead frames, and heat dissipation members. For example, Cu-Zn alloys (so-called brass) have been used as copper alloys for the above-mentioned various applications, as shown in Patent Documents 1 to 3. In these Patent Documents 1 to 3, various elements other than Cu and Zn are added to ensure strength and workability.

[0003] Japanese Unexamined Patent Publication No. 2001-164328 (A) Japanese Unexamined Patent Application No. 2002-088428 (A) Japanese Unexamined Patent Application No. 2009-062610 (A) Japanese Unexamined Patent Application No. 2000-169920 (A)

[0004] In recent years, efforts have been made to make electronic and electrical device components more flexible in order to improve the ease of use of electronic and electrical devices. Therefore, materials for electronic and electrical device components are required to have a low Young's modulus to facilitate elastic deformation, while also having a large amount of elastic deformation so that they can return to their original shape without undergoing plastic deformation even when subjected to large deformation. Conventional copper alloys, such as those described in Patent Documents 1-3, do not have a low Young's modulus and are unable to sufficiently increase the amount of elastic deformation, which could easily lead to plastic deformation when subjected to large deformation. Patent Document 4 reports a copper-based alloy that exhibits large pseudoelastic deformation due to shape memory properties and superelastic properties while maintaining excellent workability. However, the Young's modulus is not sufficiently low, making it difficult to deform. Furthermore, electrical conductivity is not disclosed, and when electrical conductivity is low, there is the problem of large heat generation and large energy loss when electricity is applied.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a copper alloy that has excellent electrical conductivity, a low Young's modulus, a sufficiently large amount of elastic deformation, and is resistant to plastic deformation even when subjected to large deformation, as well as a copper alloy plastically processed material made from this copper alloy, a component for electronic and electrical equipment, a component for flexible devices, a heat dissipation component, and a metal sealing material.

[0006] To solve the above problems, the inventors conducted extensive research and discovered the following. It became clear that in order to obtain a copper material with a low Young's modulus, it is important to "obtain a large amount of β phase" and "reduce the grain boundary energy of the β phase." The β phase that appears in copper alloys has a lower Young's modulus than the α phase used in ordinary copper alloys, so obtaining a large amount of β phase can reduce the Young's modulus. Furthermore, random grain boundaries with large grain boundary energy inhibit each other from deforming, but the presence of many grain boundaries with small grain boundary energy facilitates deformation, allowing for a low Young's modulus. Therefore, it was discovered that creating a β phase structure containing many coincidence grain boundaries and grain boundaries with small misorientation is important for reducing the Young's modulus of a copper alloy.

[0007] The present invention has been made based on the above findings, and a copper alloy according to a first aspect of the present invention contains 15% by mass or more and 57% by mass or less of Zn, 12% by mass or less of Al, and has a composition that satisfies A+5×B≧30 and A+3.5×B≦57, where A is A% by mass of Zn and B is B% by mass of Al, with the balance being Cu and inevitable impurities, and has a volume fraction of β phase of 50% or more, and has a thickness of 8 mm or less by EBSD. ２ The above measurement area is measured at measurement intervals of 8 μm, and analysis is performed excluding measurement points where the CI value analyzed by the data analysis software OIM is 0.1 or less. Measurement points where the orientation difference between adjacent measurement points is 5° or more are defined as grain boundaries, and the ratio of the length of each corresponding grain boundary in the range of 3≦Σ≦29 to the length of all grain boundaries where the measured β phases contact each other is 4% or more.

[0008] According to the copper alloy of the first aspect of the present invention, the copper alloy contains 15% by mass or more and 57% by mass or less of Zn and 12% by mass or less of Al, where the Zn content is A% by mass and the Al content is B% by mass, satisfying A + 5 × B ≥ 30 and A + 3.5 × B ≤ 57, with the remainder being Cu and unavoidable impurities. This composition provides excellent strength, electrical conductivity, and good thermal conductivity. Furthermore, the β phase can be sufficiently formed. Since the volume fraction of the β phase is 50% or more, the proportion of the β phase is large, resulting in a sufficiently low Young's modulus. Furthermore, the grain boundaries between adjacent measurement points in the β phase, where the misorientation between the adjacent measurement points is 5° or more, are defined as grain boundaries. The proportion of each corresponding grain boundary length between the measured β phases in the range of 3 ≤ Σ ≤ 29 is 4% or more. This reduces the grain boundary energy of the β phase, sufficiently reduces the Young's modulus, and increases the elastic deformation. Therefore, even if it is subjected to a large deformation, it will not easily undergo plastic deformation, and it can be suitably used in applications where flexibility is required.

[0009] A copper alloy according to a second aspect of the present invention is characterized in that, in the copper alloy according to the first aspect of the present invention, it further contains 0.005% by mass or more and 10% by mass or less of Ni. Since the copper alloy according to the second aspect of the present invention contains 0.005% by mass or more and 10% by mass or less of Ni, the strength can be further improved by solid solution strengthening due to Ni and the formation of precipitates containing Ni and Al.

[0010] A copper alloy according to a third aspect of the present invention is characterized in that, in the copper alloy according to the first or second aspect of the present invention, it further contains one or more C-group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag in a total amount of 0.0005% by mass or more and 2.5% by mass or less. Since the copper alloy according to the third aspect of the present invention contains one or more C-group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag in a total amount of 0.0005% by mass or more and 2.5% by mass or less, it is possible to suppress plastic deformation of the β phase and further increase the amount of elastic deformation while maintaining electrical conductivity.

[0011] A copper alloy according to a fourth aspect of the present invention is characterized in that, in the copper alloy according to any one of the first to third aspects of the present invention, it further contains one or more D-group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM) in a total amount of 0.0005% by mass to 2.5% by mass. Since the copper alloy according to the fourth aspect of the present invention contains one or more D-group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM) in a total amount of 0.0005% by mass to 2.5% by mass, it is possible to suppress plastic deformation of the β phase and further increase the amount of elastic deformation while maintaining electrical conductivity.

[0012] The copper alloy of Aspect 5 of the present invention is characterized in that, in the copper alloy of any one of Aspects 1 to 4 of the present invention, the proportion of grain boundaries where β phases contact each other and have a misorientation of 20° or less is 10% or more. According to the copper alloy of Aspect 5 of the present invention, since the proportion of grain boundaries where the misorientation is 20° or less is 10% or more, adjacent crystal grains are prevented from interfering with each other during deformation, and deformation is facilitated, thereby making it possible to lower the Young's modulus.

[0013] A copper alloy according to a sixth aspect of the present invention is characterized in that, in the copper alloy according to any one of the first to fifth aspects of the present invention, the maximum value of the intensity plot of the crystal orientation in the working direction of the β phase obtained from texture analysis by the EBSD method is equal to or greater than 2. According to the copper alloy according to the sixth aspect of the present invention, the maximum value of the intensity plot of the crystal orientation in the working direction of the β phase is equal to or greater than 2, which prevents adjacent crystal grains from interfering with each other during deformation, making the alloy more susceptible to deformation and thereby enabling a lower Young's modulus.

[0014] A copper alloy according to a seventh aspect of the present invention is characterized in that the maximum value of the intensity plot of the crystal orientation of the β phase in any one of the copper alloys according to the first to sixth aspects of the present invention is within a 30° misorientation from <001> or <101>. According to the copper alloy according to the seventh aspect of the present invention, the maximum value of the intensity plot of the crystal orientation of the β phase is within a 30° misorientation from <001> or <101>, and the crystal orientation of the β phase is concentrated in <001> or <101>, which allows the Young's modulus to be further reduced.

[0015] The copper alloy of Aspect 8 of the present invention is characterized in that the Young's modulus is 100 GPa or less in the copper alloy of any one of Aspects 1 to 7 of the present invention. According to the copper alloy of Aspect 8 of the present invention, since the Young's modulus is 100 GPa or less, the Young's modulus is sufficiently low, elastic deformation is easy, and the copper alloy can be suitably used in applications where flexibility is required.

[0016] A copper alloy according to Aspect 9 of the present invention is characterized in that the copper alloy according to any one of Aspects 1 to 8 of the present invention has a maximum elastic strain of 0.4% or more. According to the copper alloy according to Aspect 9 of the present invention, the maximum elastic strain is set to 0.4% or more, and the copper alloy is resistant to plastic deformation even when subjected to large deformation.

[0017] A copper alloy according to a tenth aspect of the present invention is characterized in that the copper alloy according to any one of the first to ninth aspects of the present invention has an electrical conductivity of 10% IACS or more. Since the copper alloy according to the tenth aspect of the present invention has an electrical conductivity of 10% IACS or more, electrical conductivity is ensured and the copper alloy can be suitably used as a material for current-carrying members.

[0018] A plastically worked copper alloy material according to an eleventh aspect of the present invention is characterized in that it is made of the copper alloy according to any one of the first to tenth aspects of the present invention.

[0019] A part for an electronic / electrical device according to a twelfth aspect of the present invention is characterized in that it is made of the copper alloy according to any one of the first to tenth aspects of the present invention.

[0020] A flexible device component according to a thirteenth aspect of the present invention is characterized in that it is made of the copper alloy according to any one of the first to tenth aspects of the present invention.

[0021] A heat dissipation component according to a fourteenth aspect of the present invention is characterized in that it is made of the copper alloy according to any one of the first to tenth aspects of the present invention.

[0022] A metal sealing material according to a fifteenth aspect of the present invention is characterized in that it is made of the copper alloy according to any one of the first to tenth aspects of the present invention.

[0023] According to the present invention, it is possible to provide a copper alloy that has excellent electrical conductivity, a low Young's modulus, a sufficiently large amount of elastic deformation, and is resistant to plastic deformation even when subjected to large deformation, as well as a copper alloy plastically processed material made of this copper alloy, components for electronic and electrical equipment, components for flexible devices, heat dissipation components, and metal sealing materials.

[0024] 1 is a flow diagram of a method for producing a copper alloy according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of maximum elastic strain in an example.

[0025] A copper alloy according to one embodiment of the present invention will be described below. The copper alloy according to this embodiment is used as a material for various components, such as components for electronic and electrical equipment, components for flexible devices, heat dissipation components, and metal sealing materials. The copper alloy according to this embodiment contains 15% by mass or more and 57% by mass or less of Zn and 12% by mass or less of Al, where the Zn content is A% by mass and the Al content is B% by mass, satisfying A + 5 × B ≧ 30 and A + 3.5 × B ≦ 57, with the balance being Cu and unavoidable impurities. The copper alloy according to this embodiment may further contain 0.005% by mass or more and 10% by mass or less of Ni.

[0026] The copper alloy of this embodiment may further contain one or more C group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag in a total amount of 0.0005% by mass to 2.5% by mass, or one or more D group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM) in a total amount of 0.0005% by mass to 2.5% by mass.

[0027] In the copper alloy of this embodiment, the volume fraction of the β phase is set to 50% or more, and the EBSD method is used to measure the thickness of 8 mm. ２ The above measurement areas were measured at measurement intervals of 8 μm, and analysis was performed excluding measurement points where the CI value analyzed by the data analysis software OIM was 0.1 or less. Measurement points in the β phase where the orientation difference between adjacent measurement points was 5° or more were defined as grain boundaries, and the proportion of each corresponding grain boundary length in the range of 3≦Σ≦29 to the total grain boundary length where the measured β phases contact each other was set to 4% or more.

[0028] In the copper alloy of this embodiment, it is preferable that the proportion of grain boundaries where β phases contact each other and where the misorientation is 20° or less is 10% or more. Furthermore, in the copper alloy of this embodiment, it is preferable that the maximum value of the intensity plot of the crystal orientation of the β phase in the processing direction obtained from the texture analysis by the EBSD method is 2 or more. In the copper alloy of this embodiment, it is preferable that the maximum value of the intensity plot of the crystal orientation of the β phase is within a misorientation of 30° from <001> or <101>.

[0029] Here, in the copper alloy of this embodiment, it is preferable that the Young's modulus is 100 GPa or less, the maximum elastic strain is 0.4% or more, and the electrical conductivity is 10% IACS or more.

[0030] The reasons for specifying the component composition, crystalline structure, and various properties of the copper alloy of this embodiment as described above will be explained below.

[0031] (Zn) The copper alloy of this embodiment is composed primarily of Cu and Zn. If the Zn content is less than 15% by mass, the β phase may be insufficient, the volume fraction of the β phase may be less than 50%, and the Young's modulus may be high. If the Zn content exceeds 57% by mass, a very brittle γ phase may appear, significantly reducing workability. Therefore, in this embodiment, the Zn content is set within the range of 15% by mass to 57% by mass. This allows for excellent strength, electrical conductivity, and good thermal conductivity. The Zn content is preferably 18% by mass or more, and more preferably 20% by mass or more. The Zn content is preferably 56% by mass or less, and more preferably 55% by mass or less.

[0032] (Al) Adding an appropriate amount of Al to a Cu-Zn alloy can further improve strength. Here, to ensure sufficient β-phase while improving strength, it is preferable to set the Al content to 12 mass% or less, and satisfy the following conditions: A + 5 × B ≧ 30 and A + 3.5 × B ≦ 57, where A is the Zn content and B is the Al content. If A + 5 × B is less than 30, sufficient β-phase is not obtained, resulting in a high Young's modulus. If A + 3.5 × B exceeds 57, the proportion of brittle γ-phase increases, making processing difficult. The Al content is more preferably 11 mass% or less, and even more preferably 10 mass% or less. Although not particularly limited, the Al content may be 0.01 mass% or more, 0.1 mass% or more, or 1 mass% or more. Furthermore, A + 5 × B is more preferably 31 or more, and even more preferably 32 or more. Furthermore, A+3.5×B is more preferably 56 or less, and even more preferably 55 or less.

[0033] (Ni) Adding an appropriate amount of Ni to a Cu-Zn alloy not only strengthens the solid solution, but also produces precipitates containing Ni and Al when added together with Al, making it possible to further improve strength. Here, in order to obtain the effect of Ni improving strength without significantly reducing electrical conductivity, it is preferable that the Ni content be in the range of 0.005% by mass or more and 10% by mass or less. The Ni content is more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more. Furthermore, the Ni content is more preferably 9% by mass or less, and even more preferably 8% by mass or less. Furthermore, when Ni is not intentionally added, the Ni content may be less than 0.005% by mass.

[0034] (C-group element: one or more selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag) In the copper alloy of this embodiment, by containing one or more C-group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag, plastic deformation of the β phase is suppressed and the amount of elastic deformation is further increased. On the other hand, if these C-group elements are contained in large amounts, electrical conductivity may be reduced. Therefore, in the copper alloy of this embodiment, it is preferable that the total content of one or more C-group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag is within the range of 0.0005% by mass to 2.5% by mass. Co, Fe, Sn, Mg, and Ag are elements suitable for strengthening the β phase, and their optimal composition is 0.0005% to 1% by mass in total. Mn, Si, and Be are elements effective not only for strengthening the β phase but also for obtaining a larger amount of the β phase, and their optimal composition is 0.0005% to 1% by mass in total. Sb, Cd, and As are elements suitable for strengthening the β phase, and their optimal composition is 0.0005% to 0.5% by mass in total. The total content of C-group elements is preferably 0.001% by mass or more, and more preferably 0.005% by mass or more. The total content of C-group elements is preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. If C-group elements are not intentionally added, the total content of C-group elements may be less than 0.0005% by mass.

[0035] (D-group element: one or more selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal) In the copper alloy of this embodiment, by containing one or more D-group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM), precipitates and compounds are formed, thereby suppressing plastic deformation of the β phase and further increasing the amount of elastic deformation. On the other hand, if these D-group elements are contained in large amounts, electrical conductivity may be reduced. Therefore, in the copper alloy of this embodiment, it is preferable that the total content of one or more D-group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM) is within the range of 0.0005% by mass to 2.5% by mass. Ti, V, Cr, Zr, and MM are elements suitable for strengthening the β phase by reacting with oxygen, sulfur, P, B, C, etc. in the material to form compounds, and their optimal composition is a total of 0.0005 to 0.8 mass%. Nb, Mo, and W are elements suitable for strengthening the β phase, and their optimal composition is a total of 0.0005 to 0.5 mass%. P and C are elements suitable for deoxidizing the material and forming compounds with other elements to strengthen the β phase, and their optimal composition is a total of 0.0005 to 1 mass%. B is an element suitable for suppressing embrittlement of the material and forming compounds with other elements to strengthen the β phase, and its optimal composition is 0.0005 to 1 mass%. The total content of D group elements is preferably 0.001 mass% or more, and more preferably 0.005 mass% or more. The total content of the D group elements is more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less. When the D group elements are not intentionally added, the total content of the D group elements may be less than 0.0005% by mass.

[0036] In addition, examples of inevitable impurities other than the above-mentioned elements include Ba, Ca, rare earth elements, Ta, Re, Ru, Sr, Os, Rh, Ir, Pb, Pd, Pt, Au, Hf, Hg, Ga, In, Ge, Tl, N, and Li. These impurity elements may be contained to the extent that they do not affect the characteristics. Since these inevitable impurities may reduce the conductivity, the total amount is preferably 1 mass % or less, more preferably 0.7 mass % or less, and even more preferably 0.5 mass % or less.

[0037] (Volume Fraction of β Phase) In Cu—Zn alloys, in addition to the β phase, there is a possibility that the α phase and the γ phase may appear. Here, since the Young's modulus decreases due to deformation of the β phase, if the volume fraction of the β phase is less than 50%, the β phase cannot be sufficiently deformed, resulting in a high Young's modulus. Therefore, in the copper alloy of this embodiment, the volume fraction of the β phase is set to 50% or more. The volume fraction of the β phase is preferably 60% or more, and more preferably 70% or more. Although not particularly limited, the volume fraction of the β phase may be 100% or less, 98% or less, or 95% or less.

[0038] (Proportion of the Corresponding Grain Boundary Length of 3≦Σ≦29) Since the corresponding grain boundaries of 3≦Σ≦29 have low grain boundary energy, when the ratio of the length of the corresponding grain boundaries of 3≦Σ≦29 (Σ3, 5, 7, 9, 11, 13a, 13b, 15, 17a, 17b, 19a, 19b, 21a, 21b, 23, 25a, 25b, 27a, 27b, 29a, 29b) to the length of all the measured grain boundaries where β phases contact each other is 4% or more, the deformation inhibition between adjacent grains is reduced, and deformation becomes easier, resulting in a decrease in Young's modulus. Therefore, in this embodiment, the ratio of the corresponding grain boundary length of 3≦Σ≦29 to the length of all the measured grain boundaries where β phases contact each other is set to 4% or more. Note that the ratio of the corresponding grain boundary length of 3≦Σ≦29 to the length of all the measured grain boundaries where β phases contact each other is preferably 5% or more, and more preferably 6% or more. Although not particularly limited, the ratio of the length of the coincident grain boundaries of 3≦Σ≦29 to the length of all the measured grain boundaries between adjacent β phases may be 50% or less, 40% or less, or 30% or less.

[0039] (Proportion of grain boundary length where misorientation is 20° or less) When the proportion of grain boundary length where misorientation is 20° or less at the grain boundary where β phases contact each other is 10% or more, adjacent crystal grains are prevented from interfering with each other during deformation, making deformation easier and allowing the Young's modulus to be lowered. Therefore, the proportion of grain boundary length where misorientation is 20° or less is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. Although not particularly limited, the proportion of grain boundary length where misorientation is 20° or less may be 100% or less, 85% or less, or 70% or less.

[0040] (Maximum Value of Intensity Plot of Crystal Orientation of β Phase) The intensity plot of the crystal orientation of the β phase is obtained by plotting the orientation distribution of the observed sample on an inverse pole figure. The intensity is a value representing how many times the intensity of each orientation is, assuming that a state in which all orientations appear with the same probability is 1. By setting the maximum value of the intensity plot of the crystal orientation of the β phase to 2 or more, it is possible to prevent adjacent crystal grains from interfering with each other during deformation, making deformation easier and thereby reducing the Young's modulus. Therefore, in this embodiment, the maximum value of the intensity plot of the crystal orientation of the β phase in the processing direction obtained from texture analysis by the EBSD method is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3 or more. Although not particularly limited, the maximum value of the intensity plot of the crystal orientation of the β phase in the processing direction obtained from texture analysis by the EBSD method may be 30.0 or less, 28.5 or less, or 27.0 or less.

[0041] (Orientation of maximum value of intensity plot of β phase crystal orientation) By concentrating the β phase crystal orientation to <001> or <101>, the Young's modulus can be further reduced. If the orientation deviates significantly from <001> or <101>, the Young's modulus becomes high. Therefore, it is preferable that the maximum value of the intensity plot of the β phase crystal orientation is within 30° from <001> or <101>, more preferably within 25°. Even more preferably within 20°.

[0042] (Young's modulus) The copper alloy of this embodiment is required to have a low Young's modulus so as to be easily elastically deformed. Specifically, the copper alloy of this embodiment preferably has a Young's modulus of 100 GPa or less. The Young's modulus is more preferably 90 GPa or less, and even more preferably 80 GPa or less.

[0043] (Maximum Elastic Strain) In the copper alloy of this embodiment, it is required to ensure an elastic deformation amount so that plastic deformation does not easily occur even when subjected to large deformation. Specifically, in the copper alloy of this embodiment, the maximum elastic strain is preferably 0.4% or more. The maximum elastic strain is more preferably 0.45% or more, and even more preferably 0.5% or more.

[0044] (Electrical Conductivity) In the copper alloy of this embodiment, when the electrical conductivity is 10% IACS or more, it is particularly suitable as a material for current-carrying members that are parts for electric and electronic devices. Note that the electrical conductivity of the copper alloy of this embodiment is preferably 12% IACS or more, and more preferably 14% IACS or more.

[0045] Next, an example of a method for producing the copper alloy according to this embodiment will be described with reference to the flow chart shown in FIG.

[0046] (Melting and Casting Step S01) First, the above-mentioned 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. Note that, for adding various elements, single elements or master alloys, etc. can be used. Furthermore, raw materials containing the above-mentioned elements may be melted together with the copper raw material. Here, it is preferable that each element has a purity of 99.9 mass% or more, so-called 3N, or 99.99 mass% or more, so-called 4N. In the melting step, in order to reduce the hydrogen concentration, H ２ It is preferable to perform atmospheric melting in an inert gas atmosphere (e.g., Ar gas) with a low O vapor pressure, and to minimize the holding time during melting. The molten copper alloy with the adjusted composition is then poured into a mold to produce an ingot. Note that, when mass production is taken into consideration, it is preferable to use a continuous casting method or a semi-continuous casting method.

[0047] (Hot Working Step S02) The obtained ingot is subjected to hot working to homogenize the structure and to deform the shape to a predetermined size. By introducing strain during hot working, high strain can be applied to the coarse crystals, thereby improving the homogeneity of the material. In the hot working step S02, a certain processing rate is required to destroy the cast structure, and the total processing rate must be 50% or more, preferably 55% or more, and more preferably 60% or more. While the plastic processing method is not particularly limited, rolling is preferred when the final shape is a plate or strip. For wire or rod, extrusion or groove rolling is preferred, while forging or pressing is preferred for bulk shapes.

[0048] (Lightly processed step S03) Next, light processing is performed with a total processing rate of 40% or less. Here, the processing method is not particularly limited, but rolling is used when the final form is a plate or strip. Other methods that may be used include forging, pressing, and groove rolling. The temperature is also not particularly limited, but it is preferably within the range of -200°C to 400°C, which corresponds to cold or warm processing. Here, by setting the processing rate to 40% or less, a large amount of strain is introduced into the crystal grains that are easily processed, resulting in a non-uniform strain distribution. This non-uniformity of strain suppresses the simultaneous grain growth of all crystal grains and allows crystal grains with similar crystal orientations to grow, resulting in a structure with a high frequency of presence of specific crystal orientations.

[0049] (Heat Treatment Step S04) Heat treatment is performed to homogenize and obtain a large amount of β phase. While the heat treatment method is not particularly limited, it is preferable to perform the heat treatment in a non-oxidizing or reducing atmosphere. Here, heat treatment must be performed at a high temperature. Because a sufficient amount of β phase cannot be obtained at a low temperature, the heat treatment temperature is preferably 600°C or higher, more preferably 700°C or higher. Furthermore, because too high a temperature exceeds the melting point of the material, the heat treatment temperature must be 1000°C or lower. Furthermore, the heating rate must be slow, at 10°C / min or lower. By slowing the heating rate, simultaneous grain growth of all crystal grains can be suppressed, allowing crystal grains with similar crystal orientations to grow, resulting in a structure with a high frequency of specific crystal orientations. A cooling method with a cooling rate of 200°C / min or higher, such as water quenching, is required. If the cooling rate is slow, many phases other than β phase may appear during cooling, resulting in a decrease in the β phase fraction. Furthermore, hot working may be performed after heat treatment to improve the efficiency of rough processing and homogenize the structure. The processing method is not particularly limited, but rolling is used when the final form is a plate or strip, and extrusion or groove rolling is used when the final form is a wire or rod. The combination of low processing and heat treatment is repeated three or more times to obtain many coincidence grain boundaries.

[0050] (Tempering Process Step S05) The copper material after the recrystallization heat treatment may be subjected to tempering process to adjust the material strength. If a low material strength is required, tempering process may not be performed. The final thickness and wire diameter are not particularly limited. In this tempering process step S05, there is no particular limitation on the processing method, and for example, rolling, wire drawing, extrusion, groove rolling, forging, pressing, etc. can be used.

[0051] The copper alloy (plastically worked copper alloy material) of this embodiment is manufactured by the above-mentioned steps. The means for adjusting the volume fraction of the β phase and the proportion of each corresponding grain boundary length in the range of 3≦Σ≦29 to fall within the above-mentioned ranges is not limited to a specific method, but can be achieved, for example, by controlling the total working rate of the low working, the heating rate and cooling rate of the heat treatment, the number of repetitions of the low rolling and the heat treatment, etc., as described above.

[0052] The copper alloy of this embodiment, configured as described above, contains 15% by mass or more and 57% by mass or less of Zn and 12% by mass or less of Al, where the Zn content is A% by mass and the Al content is B% by mass, satisfying A + 5 × B ≥ 30 and A + 3.5 × B ≤ 57, with the remainder being Cu and unavoidable impurities. This composition provides excellent strength, electrical conductivity, and thermal conductivity. Furthermore, the grain boundaries between adjacent measurement points in the β phase, where the misorientation between the measurement points is 5° or more, are defined as grain boundaries. The proportion of each corresponding grain boundary length between the measured β phases in the range of 3 ≤ Σ ≤ 29 to the total grain boundary length between the measured β phases is 4% or more. This reduces the grain boundary energy of the β phase, sufficiently reduces the Young's modulus, and increases the amount of elastic deformation. Therefore, even when subjected to large deformation, the alloy is not easily plastically deformed, making it suitable for applications requiring flexibility.

[0053] In this embodiment, when the alloy further contains 0.005 mass % or more and 10 mass % or less of Ni, in addition to solid solution strengthening, precipitates containing Ni and Al are generated, thereby making it possible to further improve the strength.

[0054] In the present embodiment, when one or more C group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As, and Ag are further contained in a range of 0.0005 mass % or more and 2.5 mass % or less in total, it is possible to suppress plastic deformation of the β phase and further increase the amount of elastic deformation while maintaining electrical conductivity.

[0055] In this embodiment, when one or more D group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C, and misch metal (MM) are further contained in a range of 0.0005 mass % or more and 2.5 mass % or less in total, the electrical conductivity can be maintained while suppressing plastic deformation of the β phase, thereby further increasing the amount of elastic deformation.

[0056] In this embodiment, when the proportion of grain boundaries where the misorientation between β phases is 20° or less is 10% or more, adjacent crystal grains are prevented from hindering each other during deformation, making deformation easier, thereby further reducing the Young's modulus.

[0057] In this embodiment, when the maximum value of the intensity plot of the crystal orientation of the β phase in the processing direction obtained from the texture analysis by the EBSD method is 2 or more, the Young's modulus can be further reduced by preventing adjacent crystal grains from interfering with each other during deformation and facilitating deformation.

[0058] In this embodiment, when the maximum value of the intensity plot of the β phase crystal orientation is within an orientation difference of 30° from <001> or <101>, the β phase crystal orientation is concentrated toward <001> or <101>, and the Young's modulus can be further reduced.

[0059] In this embodiment, when the Young's modulus is 100 GPa or less, the Young's modulus is sufficiently low and the film can be easily elastically deformed, and the film can be suitably used in applications requiring flexibility, such as flexible devices and printed wiring used therein, and further, metal sealing materials.

[0060] In this embodiment, when the maximum elastic strain is 0.4% or more, the amount of elastic deformation is sufficiently secured, and even if subjected to a large deformation, the material will not easily undergo plastic deformation, making it suitable for use in applications requiring flexibility.

[0061] In this embodiment, when the electrical conductivity is 10% IACS or more, the electrical conductivity is ensured, and the material can be suitably used as a material for electronic and electrical device components such as terminals, current-carrying members, probe needles, thermal interface materials, and heat dissipation components.

[0062] Although the copper alloy according to the embodiment of the present invention has been described above, the present invention is not limited thereto and can be appropriately modified within the scope of the technical concept of the invention. In the above embodiment, an example of a method for manufacturing a copper alloy has been described, but the method for manufacturing a copper alloy is not limited to that described in the above embodiment and may be manufactured by appropriately selecting an existing manufacturing method.

[0063] The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0064] First, a raw material consisting of pure copper with a purity of 99.999% by mass or higher and each additive element with a purity of 99.9% or higher was prepared. This was then placed in a high-purity graphite crucible and subjected to high-frequency melting in an atmospheric furnace with an Ar gas atmosphere. The resulting mixture was adjusted to the composition shown in Table 1, and poured into a mold made of insulating material (Isowool) to produce an ingot. The size of the ingot was approximately 20 mm thick, 100 mm wide, and 150-200 mm long.

[0065] Next, the obtained ingots were subjected to hot working (hot rolling) in an Ar gas atmosphere under the conditions shown in Table 2. After the thermal working, the surfaces were ground to remove the oxide film, and the ingots were cut to a predetermined size. The size was then adjusted appropriately to obtain the final shape. Then, light working, heat treatment, and tempering were performed under the conditions shown in Table 2, and strip materials for property evaluation made of the copper alloys of the present invention examples and comparative examples with plate thicknesses of 1 mm to 5 mm were produced.

[0066] The copper alloys of the invention examples and comparative examples obtained as described above were evaluated as follows. The evaluation results are shown in Table 3. Note that the columns in which evaluation was not possible because the β phase was not obtained are marked with "NA" (Not Applicable).

[0067] (Composition analysis) Measurement samples were taken from the obtained ingots and measured using an inductively coupled plasma (ICP) analyzer. Measurements were performed at two locations, the center and the widthwise end of the sample, and the content of the higher content was recorded as the content of the sample.

[0068] (Volume fraction of β phase) A sample of 10 mm × 20 mm was cut out from the strip material for property evaluation, and the cross section perpendicular to the processing direction was mechanically polished using waterproof abrasive paper and diamond abrasive grains, and then finished by polishing using a colloidal silica solution. This sample was analyzed using an EBSD measuring device (Quanta FEG 450 manufactured by FEI, OIM Data Collection manufactured by EDAX / TSL (now AMETEK)) and analysis software (OIM Data Analysis ver. 8.6 manufactured by EDAX / TSL (now AMETEK)) at an electron beam acceleration voltage of 15 kV, a measurement interval of 1 μm, and a measurement interval of 1 mm. ２ In the above measurement areas, except for measurement points where the CI value was 0.1 or less, the misorientation of each crystal grain was analyzed to identify the crystalline phase, and the ratio of the area identified as the β phase in each measurement field was taken as the area fraction of the β phase. Measurements were carried out in three or more fields, and the average value of the area fractions was taken as the volume fraction of the β phase.

[0069] (Ratio of corresponding grain boundary length) A sample of 10 mm x 20 mm was cut out from the strip material for characteristic evaluation, and the cross section perpendicular to the processing direction was mechanically polished using waterproof abrasive paper and diamond abrasive grains, and then finished by polishing using colloidal silica solution. This sample was measured using an EBSD measuring device (FEI Quanta FEG 450, EDAX / TSL (now AMETEK) OIM Data Collection) and analysis software (EDAX / TSL (now AMETEK) OIM Data Analysis ver. 8.6) at an electron beam acceleration voltage of 15 kV, a measurement interval of 8 μm, and a measurement interval of 8 mm. ２ In the above measurement area, the misorientation of each crystal grain was analyzed, excluding measurement points where the CI value was 0.1 or less. Measurement points where the misorientation between adjacent measurement points was 5° or more were considered to be crystal grain boundaries, and the correspondence relationship between adjacent crystal grains was measured. Measurements were performed in three or more fields, and the average value was used as the proportion of the corresponding grain boundary.

[0070] (Proportion of grain boundary length with misorientation of 20° or less) As with the proportion of coincident grain boundaries, measurements and analysis were performed using SEM-EBSD and OIM (registered trademark), and measurement points between adjacent measurement points where the misorientation between the adjacent measurement points was 5° or more were regarded as grain boundaries, and the misorientation between adjacent grains was measured. Measurements were performed in three or more fields, and the proportion of grain boundary lengths with misorientation of 20° or less in each field was determined, and the average value was taken as the proportion of grain boundaries with misorientation of 20° or less.

[0071] (Intensity plot of the crystal orientation of the β phase) Electron beam acceleration voltage 15 kV, measurement interval 8 μm step 8 mm ２ Measurements were made in the direction perpendicular to the processing in the above measurement areas, and the misorientation of each β-phase crystal grain was analyzed, excluding measurement points where the CI value was 0.1 or less. The crystal orientation in the processing direction at each measurement point was plotted on an inverse pole figure to create an intensity plot. Measurements were made in three or more fields, and the maximum value was used as the intensity plot value. In addition, in Table 3, if the maximum value of the intensity plot of the β-phase crystal orientation was within 30° of <001>, it was marked "Satisfied" in the "Within 30° of <001>" column, and if the maximum value of the intensity plot of the β-phase crystal orientation was not within 30° of <001>, it was marked "Not-Satisfied." Furthermore, in Table 3, if the maximum value of the intensity plot of the β phase crystal orientation is within 30° from <101>, it is marked as "Satisfied" in the "Within 30° from <101>" column, and if the maximum value of the intensity plot of the β phase crystal orientation is not within 30° from <101>, it is marked as "Not-Satisfied."

[0072] (Conductivity) Test pieces measuring 10 mm wide x 60 mm long were taken from the strip material for property evaluation, and the electrical resistance was measured using a four-terminal method. The dimensions of the test pieces were measured using a micrometer, and the volume of the test pieces was calculated. The electrical conductivity was calculated from the measured electrical resistance and volume. The test pieces were taken so that their longitudinal direction was parallel to the processing direction of the strip material for property evaluation.

[0073] (Young's Modulus) Young's modulus E was determined from the gradient in the elastic region of the stress-strain curve by attaching a contact extensometer to a test piece having the same shape as above and conducting a mechanical test in accordance with JIS Z 2241. The strain rate was 5×10―４ s ―１ The test pieces were taken so that the tensile direction of the tensile test was parallel and perpendicular to the processing direction of the strip material for property evaluation, and the lower value is shown in the table.

[0074] (Maximum elastic strain) In the same tensile test as above, as shown in Figure 2, stress was repeatedly applied and unloaded so that the applied strain increased by 0.5%, and the difference between the applied strain and the residual strain when the first residual strain occurred was taken as the maximum elastic strain. Note that the maximum elastic strain was measured by taking samples parallel and perpendicular to the processing direction, and the larger value is shown in the table. Maximum elastic strain = applied strain - residual strain

[0075]

[0076]

[0077]

[0078] In Comparative Example 1, the volume fraction of the β phase was 100%, but the proportion of the corresponding grain boundary length was low at 3.8%, the Young's modulus was high at 112 GPa, and the maximum elastic strain was small at 0.3%. In Comparative Example 2, the composition was inappropriate, so the volume fraction of the β phase was 0%, the Young's modulus was high at 110 GPa, and the maximum elastic strain was small at 0.1%. In Comparative Example 3, the volume fraction of the β phase was 100%, but the proportion of the corresponding grain boundary length was low at 3.2%, the Young's modulus was high at 120 GPa, and the maximum elastic strain was small at 0.2%. In Comparative Example 4, the volume fraction of the β phase was 95%, but the proportion of the corresponding grain boundary length was low at 3.5%, the Young's modulus was high at 105 GPa, and the maximum elastic strain was small at 0.3%. In Comparative Example 5, the composition was inappropriate, resulting in a β-phase volume fraction of 0%, resulting in a high Young's modulus of 115 GPa and a small maximum elastic strain of 0.1%. In Comparative Examples 6, 7, and 8, the composition was inappropriate, resulting in the appearance of a large amount of γ-phase, making both hot working and cold working difficult and making it impossible to produce the material.

[0079] In contrast, in Inventive Example 1-18, the volume fraction of the β phase was 50% or more, the proportion of the corresponding grain boundary length was 4% or more, the Young's modulus was 100 GPa or less, and the maximum elastic strain was large, at 0.4% or more.

[0080] As a result of the above confirmatory experiments, it was confirmed that the present invention can provide a copper alloy that has excellent electrical conductivity, a low Young's modulus, a sufficiently large amount of elastic deformation, and is resistant to plastic deformation even when subjected to large deformation.

[0081] According to the present invention, it is possible to provide a copper alloy that has excellent electrical conductivity, a low Young's modulus, a sufficiently large amount of elastic deformation, and is resistant to plastic deformation even when subjected to large deformation.

Claims

1. Contains 15% by mass or more and 57% by mass or less of Zn and 12% by mass or less of Al, where the Zn content is A% by mass and the Al content is B% by mass, A+5×B≧30 and A+3.5×B≦57, with the balance being Cu and unavoidable impurities; the volume fraction of the β phase is 50% or more; and the EBSD method has a thickness of 8 mm or less. ２ The above measurement area is measured at measurement intervals of 8 μm, and analysis is performed excluding measurement points having a CI value of 0.1 or less as analyzed by data analysis software OIM. Measurement points between adjacent measurement points having an orientation difference of 5° or more are defined as grain boundaries, and the ratio of the length of each corresponding grain boundary in the range of 3≦Σ≦29 to the length of all grain boundaries where the measured β phases are in contact with each other is 4% or more.

2. The copper alloy according to claim 1, further comprising 0.005% by mass or more and 10% by mass or less of Ni.

3. A copper alloy according to claim 1 or 2, further comprising one or more C group elements selected from Co, Fe, Mn, Si, Sn, Mg, Be, Sb, Cd, As and Ag in a total amount of 0.0005% by mass or more and 2.5% by mass or less.

4. The copper alloy according to claim 1 or 2, further comprising one or more D group elements selected from Ti, V, Cr, Nb, Mo, W, P, Zr, B, C and misch metals in a total amount of 0.0005% by mass or more and 2.5% by mass or less.

5. A copper alloy according to claim 1 or 2, characterized in that the proportion of grain boundary lengths where the misorientation is 20° or less in the grain boundaries where the β phases contact each other is 10% or more.

6. A copper alloy according to claim 1 or 2, characterized in that the maximum value of the intensity plot of the crystal orientation of the β phase in the processing direction obtained from texture analysis by EBSD method is 2 or more.

7. A copper alloy according to claim 1 or 2, characterized in that the maximum value of the intensity plot of the crystal orientation of the β phase is present within an orientation difference of 30° from <001> or <101>.

8. The copper alloy according to claim 1 or 2, characterized in that the Young's modulus is 100 GPa or less.

9. A copper alloy according to claim 1 or 2, characterized in that the maximum elastic strain is 0.4% or more.

10. The copper alloy according to claim 1 or 2, characterized in that the electrical conductivity is 10% IACS or more.

11. A plastically worked copper alloy material comprising the copper alloy according to claim 1 or 2.

12. A part for electronic or electrical equipment, comprising the copper alloy according to claim 1 or 2.

13. A part for a flexible device, comprising the copper alloy according to claim 1 or 2.

14. A heat dissipation part made of the copper alloy according to claim 1 or 2.

15. A metal sealing material comprising the copper alloy according to claim 1 or 2.

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