Flexible terminal and production method therefor

Abstract

A flexible terminal in which a metal terminal member is joined with a flexible member that is either a twisted or a braided wire having a plurality of aluminum wires, wherein: in the plurality of aluminum wires, the arithmetic mean value of the total content of Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, which are the main impurities, is 0.00005 mass% to 0.1 mass% inclusive; and in the joined portion of the flexible member, in a cross section perpendicular to the longitudinal direction of the flexible member, the area ratio of a region in which the KAM value measured using EBSD is less than 1° is 88% or higher.

Description

Flexible terminal and manufacturing method thereof

[0001] The present disclosure relates to a flexible terminal and a method for manufacturing the same.

[0002] Conventionally, flexible terminals including flexible members that are twisted or braided wires containing multiple conductors have been made of copper-based materials such as copper or copper alloys, which have high electrical conductivity. However, from the perspective of reducing workloads through weight reduction, a shift from copper-based materials to aluminum-based materials has been considered.

[0003] Patent Document 1 discloses an aluminum-based twisted wire having sufficient conductivity, etc., in which, when crystal orientation analysis is performed on a cross section perpendicular to the longitudinal direction by electron backscatter diffraction (EBSD) analysis, the area ratio of regions having a KAM value of less than 2° in the measurement region is in the range of 30% to 60%.

[0004] International Publication No. WO2024 / 043284

[0005] Cryogenic heat transfer materials are used for cooling, for example, superconducting magnets for MRI and NMR, superconducting quantum computers, etc. In recent years, there has been a demand for aluminum wires to be used as such cryogenic heat transfer materials. However, in the prior art disclosed in Patent Document 1, thermal conductivity at cryogenic temperatures has not been considered.

[0006] An object of the present disclosure is to provide a flexible terminal that includes an aluminum wire and has sufficient thermal conductivity even at extremely low temperatures, and a method for manufacturing the same.

[0007] A first aspect of the present invention is a flexible terminal in which a flexible member which is a twisted or braided wire containing a plurality of aluminum wires is joined to a metal terminal member, wherein the arithmetic mean value of the total content of major impurities, Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, in the plurality of aluminum wires is 0.00005 mass% or more and 0.1 mass% or less, and the area ratio of regions in the joined portion of the flexible member, in a cross section perpendicular to the longitudinal direction of the flexible member, where the KAM value measured by the EBSD method is less than 1°, is 88% or more.

[0008] A second aspect of the present invention is the flexible terminal according to the first aspect, wherein the average KAM value is 0.7° or less.

[0009] A third aspect of the present invention is the flexible terminal according to the first or second aspect, wherein an average GOS value measured by an EBSD method in the cross section is 2° or less.

[0010] A fourth aspect of the present invention is the flexible terminal according to any one of the first to third aspects, wherein the arithmetic mean value of the total content of the major impurities is 0.00005% by mass or more and 0.003% by mass or less.

[0011] Aspect 5 of the present invention is a method for manufacturing a flexible member having a cross-sectional area of ​​1 to 1000 mm, wherein the arithmetic mean diameter of the aluminum wires is 0.2 to 5 mm. ２ The flexible terminal according to any one of Aspects 1 to 4, wherein

[0012] A sixth aspect of the present invention is the flexible terminal according to any one of the first to fifth aspects, wherein the metal terminal member includes at least one selected from the group consisting of copper and aluminum.

[0013] A seventh aspect of the present invention is the flexible terminal according to any one of the first to sixth aspects, wherein the metal terminal member contains 90 mass % or more of copper or aluminum.

[0014] Aspect 8 of the present invention is the flexible terminal according to any one of aspects 1 to 7, wherein the metal terminal member contains 99.5 mass % or more of copper or aluminum.

[0015] A ninth aspect of the present invention is the flexible terminal according to any one of the first to eighth aspects, which is a heat transfer material for cryogenic temperatures.

[0016] A tenth aspect of the present invention includes ultrasonically bonding a flexible member that is a twisted or braided wire containing a plurality of aluminum wires to a metal terminal member, wherein the arithmetic mean value of the total content of Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, which are major impurities, in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the ultrasonic bonding is performed using ultrasonic energy of 0.1 to 20 J / mm ２and the height of the flexible member in the joining direction is reduced by 30 to 90%.

[0017] An eleventh aspect of the present invention is the manufacturing method according to the tenth aspect, further comprising heating the flexible terminal to 250 to 550° C. after the ultrasonic bonding.

[0018] A twelfth aspect of the present invention is a method for manufacturing a flexible terminal, comprising crimping a flexible member that is a twisted wire or braided wire including a plurality of aluminum wires to a metal terminal member, and heating the member to 250 to 550°C after the crimping, wherein the arithmetic mean value of the total content of major impurities, Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the crimping is performed so that the height of the flexible member in the joining direction is reduced by 30 to 90%.

[0019] A thirteenth aspect of the present invention is the flexible terminal according to the twelfth aspect, wherein the metal terminal member includes copper or aluminum.

[0020] A fourteenth aspect of the present invention is a method for manufacturing a flexible terminal, comprising crimping a flexible member that is a twisted or braided wire containing a plurality of aluminum wires to a metal terminal member that contains copper, wherein the arithmetic mean value of the total content of Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, which are major impurities, is 0.00005 mass% or more and 0.1 mass% or less, and the crimping is performed so that the height of the flexible member in the joining direction is reduced by 30 to 90%.

[0021] According to the present embodiment, it is possible to provide a flexible terminal that includes an aluminum wire and has sufficient thermal conductivity even at extremely low temperatures, and a method for manufacturing the same.

[0022] 3 shows an example of a photograph of a top view of a flexible terminal according to the present embodiment.

[0023] The inventors conducted extensive research to develop a flexible terminal that includes aluminum wires and has sufficient thermal conductivity even at extremely low temperatures. As a result, they found that ultrasonically bonding a flexible member including multiple aluminum wires with an impurity content below a predetermined value to a metal terminal member under predetermined conditions results in the formation of many regions with a low KAM value, an index of strain, in the bonded flexible member. They also found that crimp-bonding a flexible member including multiple aluminum wires with an impurity content below a predetermined value to a metal terminal member under predetermined conditions and then heating the bonded flexible member to a predetermined temperature results in the formation of many regions with a low KAM value in the bonded flexible member. Furthermore, they found that crimp-bonding a flexible member including multiple aluminum wires with an impurity content below a predetermined value to a metal terminal member containing copper under predetermined conditions results in the formation of many regions with a low KAM value in the bonded flexible member. Furthermore, they found that the flexible terminal manufactured in this manner has sufficient thermal conductivity even at extremely low temperatures. On the other hand, when an aluminum wire having an impurity content exceeding a predetermined value is used, it is not possible to form many low KAM value regions even with ultrasonic bonding, and it has also been found that the thermal conductivity at extremely low temperatures is insufficient.

[0024] The flexible terminal according to this embodiment is a flexible terminal in which a flexible member which is a twisted or braided wire containing a plurality of aluminum wires is joined to a metal terminal member, wherein the arithmetic mean value of the total content of major impurities, Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and in the joined portion of the flexible member (hereinafter simply referred to as the "joint portion"), the area ratio of regions where the KAM value measured by the EBSD method is less than 1° in a cross section perpendicular to the longitudinal direction of the flexible member is 88% or more. The flexible terminal has sufficient thermal conductivity even at extremely low temperatures.

[0025] Fig. 1 shows an example of a photograph of the top surface of a flexible terminal according to this embodiment. The flexible terminal 1 includes a flexible member 2, which is a twisted or braided wire (twisted wire in Fig. 1 ) containing multiple aluminum wires, and a metal terminal member 3. The flexible member 2 is joined to the metal terminal member 3 at a joint 4. The joint 4 can be formed, for example, by ultrasonic bonding, as described below. Here, the joint 4 includes not only the portion (surface) of the flexible member 2 that is in contact with the metal terminal member 3, but also the portion of the flexible member 2 that is present in a direction perpendicular to the joint (surface) (in the direction of the paper in Fig. 1 ).

[0026] The flexible member 2 is a twisted or braided wire including a plurality of aluminum wires. The twisted or braided wire including a plurality of aluminum wires can be made more flexible than a solid aluminum wire having the same cross-sectional area as the twisted or braided wire.

[0027] The plurality of aluminum wires have an arithmetic mean value (hereinafter also referred to as "major impurity amount X") of the total content of Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, which are major impurity elements (also referred to as "major impurities") inevitably introduced due to conditions such as raw materials, materials, and manufacturing equipment, of 0.00005% by mass to 0.1% by mass. This allows sufficient strain relief even with the relatively low energy of ultrasonic bonding described below, making it possible to form many low KAM value regions in the bonded portion 4. The major impurity amount X is preferably 0.00005% by mass to 0.003% by mass. Here, the "arithmetic mean value" of the physical property values ​​of the plurality of aluminum wires (including the arithmetic mean diameter described below) refers to the arithmetic mean value of the physical property values ​​measured for each aluminum wire. Note that if the plurality of aluminum wires are prepared using the same method (including the same raw materials), the physical property value of one of the aluminum wires may be used as the "arithmetic mean value of the physical property value."

[0028] The composition of the aluminum wires may be composed of Al and unavoidable impurities. The unavoidable impurities may include elements introduced due to the conditions of raw materials, materials, manufacturing equipment, etc. In addition to the eight major impurity elements described above, the unavoidable impurities may include V, Cr, Zr, Li, Be, B, Na, K, Ca, Ni, Co, As, Mo, Ag, Cd, In, Sn, Sb, Ba, La, Ce, Pt, Hg, Pb, Bi, Th, and U (also referred to simply as "27 elements"). The arithmetic mean value of the total content of the 27 elements may be equal to or less than half of the major impurity amount X. Note that, because the amount of unavoidable impurities other than the major impurities and the 27 elements is extremely small, the total content of the unavoidable impurities may be the total content of the major impurities and the 27 elements. That is, the arithmetic mean value of the total content of the unavoidable impurities may be equal to or less than 2 times or 1.5 times the major impurity amount X.

[0029] The above-mentioned component composition (amount of impurities) is measured by the method described in the examples below.

[0030] The multiple aluminum wires may have the same or different wire diameters. The arithmetic mean diameter of the multiple aluminum wires is preferably 0.2 to 5 mm, more preferably 0.2 to 2 mm, and may be 0.25 to 1.0 mm. By making the arithmetic mean diameter 0.2 mm or more, the thermal conductivity of the flexible member 2 (and flexible terminal 1) at extremely low temperatures can be further improved. By making the arithmetic mean diameter 5 mm or less (more preferably 2 mm or less), the flexibility of the flexible member 2 (and flexible terminal 1) can be improved.

[0031] The cross-sectional area of ​​the flexible member 2 is 1 to 1000 mm ２ It is preferable that the length is 10 to 1000 mm ２ It is more preferable that the cross-sectional area is 1 mm ２ or more (more preferably 10 mm ２ By making the cross-sectional area 1000 mm or more, the thermal conductivity of the flexible member 2 (and the flexible terminal 1) at extremely low temperatures can be further improved. ２The flexibility of the flexible member 2 (and the flexible terminal 1) can be improved by doing the following.

[0032] The flexible member 2 mainly includes the above-described plurality of aluminum wires, and may further include other conductors (such as copper wires). In the flexible member 2, the number of the above-described plurality of aluminum wires is preferably 80% or more of the total number of conductors, more preferably 90% or more, and most preferably 100% (i.e., the flexible member 2 is made up of the above-described plurality of aluminum wires).

[0033] The metal terminal member 3 is not particularly limited in shape or size, and any known metal terminal member can be used as long as it can be subjected to ultrasonic bonding, as described below. The metal terminal member 3 preferably contains at least one selected from the group consisting of copper and aluminum. This can further improve the thermal conductivity of the flexible terminal 1 at cryogenic temperatures. In one embodiment of the present invention, the metal terminal member 3 preferably contains aluminum (Al), with the Al content preferably being 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more. In another embodiment of the present invention, the metal terminal member 3 preferably contains copper (Cu), with the Cu content preferably being 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, even more preferably 99.5% by mass or more, and particularly preferably 99.9% by mass or more.

[0034] In the joint portion 4, the area ratio of the region where the KAM value measured by the EBSD method is less than 1° in a cross section perpendicular to the longitudinal direction of the flexible member 2 is 88% or more. This ensures sufficient thermal conductivity even at extremely low temperatures. The KAM value is measured using the method described in the examples below, and the "cross section perpendicular to the longitudinal direction of the flexible member 2" refers to a cross section perpendicular to the longitudinal direction in the central 1 / 5 region when the longitudinal direction of the flexible member 2 is divided into 5 equal parts.

[0035] The KAM (Kernel Average Misorientation) value represents the average value of the misorientation between a measurement point and its surrounding measurement points. A large misorientation results in a large KAM value, which may indicate the presence of a large amount of distortion. The KAM value is an evaluation index of distortion that is less affected by the grain size than the GOS value described below. While the grain size can also change depending on the amount of impurities, the KAM value can evaluate the influence of distortion while ignoring the influence of changes in the grain size, and therefore can be said to be an evaluation index suitable for the present disclosure.

[0036] The average KAM value is preferably 0.7° or less, which can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures.

[0037] In the cross section perpendicular to the longitudinal direction of the flexible member 2 at the joint portion 4, the average GOS value measured by the EBSD method is preferably 2° or less. The GOS value is measured using the method described in the Examples below. Here, the GOS (Grain Orientation Spread) value is the average value of the orientation difference between the average orientation of a crystal grain and all measurement points within that crystal grain, and is expressed for each crystal grain. The GOS value is an evaluation index of strain that is easily affected, for example, if there is even one localized point of large strain within a crystal grain. It is believed that the smaller the local strain, the fewer the points of locally low thermal conductivity. Therefore, in addition to the desired KAM value described above, it is preferable that the average GOS value is also low as described above.

[0038] The average crystal grain size measured by EBSD in a cross section perpendicular to the longitudinal direction of the flexible member 2 at the joint portion 4 is not particularly limited, but may be, for example, 1 μm or more and 1000 μm or less. The average crystal grain size is measured by the method described in the examples below.

[0039] The flexible terminal 1 has sufficient thermal conductivity even at extremely low temperatures, and is therefore suitable for use as, for example, a heat transfer material for extremely low temperatures. In particular, it is preferable to use the flexible terminal 1 as a heat transfer material for extremely low temperatures in contact with an extremely low temperature part, for example, between 1 K and 60 K, since the effect of this embodiment is significant.

[0040] One aspect of the manufacturing method of the flexible terminal 1 includes ultrasonically bonding the flexible member 2 and the metal terminal member 3, and the ultrasonic bonding is performed with ultrasonic energy of 0.1 to 20 J / mm ２ The process is performed so that the height of the flexible member 2 in the joining direction is reduced by 30 to 90%, preferably by 50 to 90%, and more preferably by 70 to 90%. This results in the flexible terminal 1. Each step in one embodiment of the method for manufacturing the flexible terminal 1 will be described in detail below.

[0041] First, the flexible member 2 and the metal terminal member 3 are prepared. The preparation method is not particularly limited, and they may be prepared by a known method or commercially available products. For example, the twisted or braided wire can be prepared by twisting or braiding the above-mentioned multiple aluminum wires using a twisting or braiding machine.

[0042] Next, the flexible member 2 and the metal terminal member 3 are ultrasonically bonded together. The ultrasonic bonding is performed with an ultrasonic energy of 0.1 to 20 J / mm ２ The ultrasonic energy is 0.1 J / mm, and the height of the flexible member 2 in the joining direction (the paper surface direction in FIG. 1) is reduced by 30 to 90% (preferably 50 to 90%, more preferably 70 to 90%). This relieves distortion in the joining portion 4, and the desired metal structure can be obtained. ２ If it is less than 20 J / mm, the strain may not be sufficiently alleviated. ２ If the reduction rate in height of the flexible member 2 in the joining direction is less than 30%, the ultrasonic energy may not be transmitted sufficiently, and if it exceeds 90%, new distortion may be generated. There are no particular restrictions on the ambient temperature during ultrasonic joining, and ultrasonic joining can be performed at room temperature.

[0043] Before ultrasonic bonding, it is preferable to heat the flexible member 2 to 250 to 550°C. This can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures. It is thought that heating can contribute to improving thermal conductivity by reducing crystal defects (dislocations) introduced during processing steps such as wire drawing, twisting, or braiding, and / or point defects that do not affect the KAM value, etc. The holding time at the above heating temperature is not particularly limited and may be, for example, 1 to 180 minutes. The heating atmosphere is not particularly limited and may be either air or a nitrogen atmosphere. After heating, the flexible terminal 1 may be allowed to cool, for example, to room temperature.

[0044] After ultrasonic bonding, it is preferable to heat the flexible terminal 1 to 250 to 550°C. This can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures. The cause of this heating effect is not clear, but it is thought that, for example, point defects (which may also occur due to ultrasonic bonding) that do not affect the KAM value, etc., are reduced by heating, contributing to improved thermal conductivity. The holding time at the above heating temperature is not particularly limited, and may be, for example, 1 to 300 minutes or 1 to 180 minutes. The heating atmosphere is not particularly limited, and may be either air or a nitrogen atmosphere. After heating, the flexible terminal 1 may be allowed to cool, for example, to room temperature.

[0045] Another aspect of the method for manufacturing the flexible terminal 1 includes crimping and joining the flexible member 2 and the metal terminal member 3 together, and heating the members to 250 to 550°C after the crimping and joining, where the crimping and joining is performed so that the height of the flexible member 2 in the joining direction is reduced by 30 to 90%. This results in the flexible terminal 1. Each step in this another aspect of the method for manufacturing the flexible terminal 1 will be described in detail below.

[0046] First, prepare the flexible member 2 and the metal terminal member 3. There are no particular limitations on the preparation method, and they may be prepared by a known method or may be commercially available.

[0047] Next, the flexible member 2 and the metal terminal member 3 are crimped together. The crimping is performed so that the height of the flexible member 2 in the joining direction is reduced by 30 to 90% (preferably 50 to 90%, more preferably 70 to 90%). This alleviates strain at the joining portion 4, resulting in a desired metal structure. If the height reduction rate in the joining direction of the flexible member 2 is less than 30%, gaps may occur between the multiple aluminum wires and / or between the multiple aluminum wires and the terminal member, and / or the flexible member 2 and the metal terminal member 3 may not be joined sufficiently. If the height reduction rate exceeds 90%, new strain may occur. The ambient temperature during crimping is not particularly limited, and crimping can be performed at room temperature. The crimping method may be performed, for example, at a pressure of 20 to 70 kg / cm. ２ For example, the flexible member 2 and the metal terminal member 3 are pressed together under a pressure of 1000 kJ / cm for several seconds.

[0048] Before crimping, the flexible member 2 is preferably heated to 250 to 550°C. This can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures. It is believed that heating contributes to improving thermal conductivity by reducing, for example, crystal defects (dislocations) introduced during processing steps such as wire drawing, twisting, or braiding, and / or point defects that do not affect the KAM value. The holding time at the above heating temperature is not particularly limited, and may be, for example, 1 to 180 minutes. The heating atmosphere is not particularly limited, and may be either air or a nitrogen atmosphere. After heating, the flexible terminal 1 may be allowed to cool, for example, to room temperature.

[0049] After the crimping and joining, the crimped and joined flexible member 2 and metal terminal member 3 are heated to 250 to 550°C. This results in a flexible terminal 1. The holding time at the above heating temperature is not particularly limited, and may be, for example, 1 to 300 minutes or 1 to 180 minutes. The heating atmosphere is not particularly limited, and may be air or a nitrogen atmosphere. After heating, the mixture may be allowed to cool, for example, to room temperature.

[0050] Yet another aspect of the method for manufacturing the flexible terminal 1 includes crimping a flexible member 2 and a metal terminal member 3 containing copper together, the crimping being performed so that the height of the flexible member 2 in the joining direction is reduced by 30 to 90%, thereby obtaining the flexible terminal 1. Each step in this yet another aspect of the method for manufacturing the flexible terminal 1 will be described in detail below.

[0051] First, the flexible member 2 and the copper-containing metal terminal member 3 are prepared. There are no particular limitations on the preparation method, and they may be prepared by a known method or may be commercially available.

[0052] Next, the flexible member 2 and the copper-containing metal terminal member 3 are crimped together. The crimping is performed so that the height of the flexible member 2 in the joining direction is reduced by 30 to 90% (preferably 50 to 90%, more preferably 70 to 90%). This alleviates strain at the joining portion 4, resulting in a desired metal structure. If the height reduction rate of the flexible member 2 in the joining direction is less than 30%, gaps may occur between the multiple aluminum wires and / or between the multiple aluminum wires and the terminal member, and / or the flexible member 2 and the copper-containing metal terminal member 3 may not be sufficiently joined. If the height reduction rate exceeds 90%, new strain may occur. The ambient temperature during crimping is not particularly limited, and crimping can be performed at room temperature. The crimping method may be performed, for example, at a pressure of 20 to 70 kg / cm. ２ For example, the flexible member 2 and the metal terminal member 3 containing copper are pressed together under a pressure of 1000 kJ / cm for several seconds.

[0053] Before crimping, the flexible member 2 is preferably heated to 250 to 550°C. This can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures. It is believed that heating contributes to improving thermal conductivity by reducing, for example, crystal defects (dislocations) introduced during processing steps such as wire drawing, twisting, or braiding, and / or point defects that do not affect the KAM value. The holding time at the above heating temperature is not particularly limited, and may be, for example, 1 to 180 minutes. The heating atmosphere is not particularly limited, and may be either air or a nitrogen atmosphere. After heating, the flexible terminal 1 may be allowed to cool, for example, to room temperature.

[0054] After crimping and bonding, the flexible terminal 1 is preferably heated to 250 to 550°C. This can further improve the thermal conductivity of the flexible terminal 1 at extremely low temperatures. The cause of this heating effect is not clear, but it is thought that, for example, point defects (which can also occur due to ultrasonic bonding) that do not affect the KAM value, etc., are reduced by heating, contributing to improved thermal conductivity. The holding time at the above heating temperature is not particularly limited, and may be, for example, 1 to 300 minutes or 1 to 180 minutes. The heating atmosphere is not particularly limited, and may be either air or a nitrogen atmosphere. After heating, the flexible terminal 1 may be allowed to cool, for example, to room temperature.

[0055] Within the scope of achieving the object of the embodiment of the present invention, the manufacturing method of the flexible terminal 1 may include other steps.

[0056] Although the manufacturing method of the flexible terminal 1 has been described above, a person skilled in the art who understands the desired characteristics of the flexible terminal 1 may, through trial and error, find a manufacturing method for the flexible terminal 1 other than the above-described manufacturing method.

[0057] A flexible member was fabricated as a 180 mm long stranded wire using nine high-purity aluminum wires (φ0.5 mm). The composition of the high-purity aluminum wire was measured by glow discharge mass spectrometry. The composition consisted of Al and inevitable impurities, the total content of major impurities was 0.00005% by mass or more and 0.003% by mass or less, and the total content of 27 elements was 0.5 times or less the total content of the major impurities.

[0058] The flexible member was heated to 350° C. in an air atmosphere and held there for 15 minutes, and then allowed to cool to room temperature.

[0059] An Al terminal member (Al content: 99.5% by mass) was prepared as the metal terminal member. The metal terminal member was ultrasonically bonded to both ends of the flexible member to obtain the flexible terminal of Test No. 1. The ultrasonic bonding was performed with ultrasonic energy of 2.4 J / mm. ２ The test was carried out so that the height of the flexible member in the joining direction was reduced by 71%.

[0060] Ultrasonic energy 3.1 J / mm２ A flexible terminal of Test No. 2 was obtained in the same manner as Test No. 1, except that the height reduction rate in the joining direction of the flexible member was changed to 73%.

[0061] Ultrasonic energy 2.8 J / mm ２ A flexible terminal of Test No. 3 was obtained in the same manner as Test No. 1, except that the height reduction rate in the joining direction of the flexible member was changed to 80%, and after ultrasonic joining, the flexible member was heated to 350°C in an air atmosphere and held for 15 minutes.

[0062] A flexible terminal of Test No. 4 was obtained in the same manner as Test No. 1, except that the metal terminal member was changed to an Al-Mn alloy (3000 series alloy) terminal member and the height reduction rate in the joining direction of the flexible member was set to 59%.

[0063] The metal terminal member was changed to Cu terminal member A (Cu content: 99.96 mass%), and the ultrasonic energy was set to 2.2 J / mm ２ A flexible terminal of Test No. 5 was obtained in the same manner as Test No. 1, except that the height reduction rate in the joining direction of the flexible member was changed to 81%.

[0064] The metal terminal member was changed to Cu terminal member B (Cu content: 99.9 mass%), and the ultrasonic energy was set to 2.2 J / mm ２ A flexible terminal of Test No. 6 was obtained in the same manner as Test No. 1, except that the height reduction rate in the joining direction of the flexible member was changed to 88%.

[0065] A flexible terminal of Test No. 7 was obtained in the same manner as Test No. 1, except that the metal terminal member was changed to Cu terminal member A (Cu content: 99.96% by mass), ultrasonic bonding was changed to crimp bonding, the height reduction rate in the bonding direction of the flexible member was set to 78%, and after crimp bonding, the flexible terminal was heated to 500°C in a nitrogen atmosphere and held for 180 minutes.

[0066] The aluminum wire was changed to a pure aluminum wire (alloy number: A1080, Al content 99.8 mass%, total content of major impurities: more than 0.1 mass%, φ0.5 mm), and the ultrasonic energy was set to 3.2 J / mm ２A flexible terminal of Test No. 8 was obtained in the same manner as Test No. 1, except that the height reduction rate in the joining direction of the flexible member was changed to 78%.

[0067] A flexible terminal of Test No. 9 was obtained in the same manner as Test No. 1, except that the metal terminal member was changed to an Al-Mg alloy terminal member, ultrasonic bonding was changed to crimp bonding, and the height reduction rate in the bonding direction of the flexible member was set to 57%.

[0068] The flexible terminals of Test Nos. 1 to 9 were evaluated as follows.

[0069] <Metal Structure Evaluation> The metal structure was observed by electron backscatter diffraction imaging (EBSD) in a cross section perpendicular to the longitudinal direction of the flexible member at the joined portion of the flexible member (hereinafter also simply referred to as the "joint portion"). Specifically, each flexible terminal was first cut at the cross section. The cut-out sample was embedded in resin and further polished to a mirror finish so that the longitudinal center of the joint portion of the flexible member could be observed. An EBSD pattern was then obtained from the polished cross section. A JSM-7900F scanning electron microscope manufactured by JEOL Ltd. was used, and a Symmetry backscatter electron diffraction detector manufactured by Oxford Instruments Ltd. was used.

[0070] The method for acquiring the EBSD pattern will be described. First, the EBSD pattern read into the device was imported into a computer, and the sample surface was scanned while performing crystal orientation analysis using analysis software. This allowed for indexing of the crystals at each measurement point, and the crystal orientation at each measurement point was determined. In this process, a continuous region having the same crystal orientation was defined as one crystal grain, and a mapping image of the crystal grain distribution, i.e., a grain map, was acquired. Note that, in defining one crystal grain, adjacent crystals were considered to have the same crystal orientation when the difference in the crystal orientation angle between them was 10° or less. Images of the crystal grains were then recorded in the computer based on the crystal orientation calculated at each measurement point.

[0071] The obtained EBSD pattern was analyzed using analysis software AZtec to obtain the area ratio of regions where the KAM value was less than 1°, the average KAM value, the average GOS value, and the average crystal grain size, as follows.

[0072] (Area ratio of regions with KAM values ​​less than 1° and average KAM values) The KAM value represents the average value of the orientation difference between a measurement point (pixel) and its surrounding measurement points (pixels). Here, in order to obtain a reproducible KAM value, it is desirable to appropriately adjust the magnification so that multiple crystal grains are included in the measurement range. For example, when the maximum crystal grain size in the measurement range is 200 μm or more, the magnification is set to 100x, and when it is less than that, the magnification is set to 850x. In addition, to improve measurement accuracy, the measurement step size was selected so that the number of pixels was 350,000 or more. Specifically, when the magnification was 100x, the measurement step size was set to 1.0 μm, and when the magnification was 850x, the measurement step size was set to 0.2 μm. In this way, the area ratio of regions with KAM values ​​less than 1° (i.e., the ratio of the area of ​​regions with KAM values ​​less than 1° when the measurement area is 100%) was determined. In order to exclude grain boundaries, if the KAM value is 10° or more, it is recognized as a grain boundary and is excluded from the calculation of the area ratio. The average KAM value was calculated as [Σ(area of ​​pixel i × KAM value of pixel i)] / measured area. The measurement location was any location, excluding the end, on the polished cross section of the joint (i.e., the jointed portion of the flexible member), and the measurement area was approximately 0.92 mm at a magnification of 100 times. ２ At a magnification of 850, it is approximately 0.015 mm ２ It was decided.

[0073] (Average GOS Value) The GOS value is the average value of the orientation differences between the average orientation of a crystal grain and all measurement points (pixels) within that crystal grain, and is expressed for each crystal grain. Here, in order to obtain a reproducible GOS value, it is desirable to appropriately adjust the magnification so that multiple crystal grains are included in the measurement range. For example, when the maximum crystal grain size within the measurement range is 200 μm or more, the magnification is set to 100x, when it is 100 μm or more but less than 200 μm, the magnification is set to 150x, and when it is less than that, the magnification is set to 850x. In addition, to improve measurement accuracy, the measurement step size was selected so that the number of pixels was 350,000 or more. Specifically, when the magnification was 100x, the measurement step size was set to 1.0 μm, when the magnification was 150x, the measurement step size was set to 0.5 μm, and when the magnification was 850x, the measurement step size was set to 0.2 μm. In this way, the average GOS value was calculated as [Σ(area of ​​crystal grain i × GOS value of crystal grain i)] / measurement area. The measurement point is any point on the polished cross section of the joint (i.e., the jointed part of the flexible member) excluding the end, and the measurement area is approximately 0.92 mm at a magnification of 100 times. ２ At a magnification of 150, it is approximately 0.48 mm ２ At a magnification of 850, it is approximately 0.015 mm ２ It was decided.

[0074] (Average Crystal Grain Size) The circle-equivalent diameters of the crystal grains were measured, and the average of the circle-equivalent diameters was calculated as an area-weighted average, which was defined as the average crystal grain size.

[0075] <Evaluation of Thermal Conductivity at Cryogenic Temperatures> Thermal conductivity at cryogenic temperatures was evaluated by measuring the residual resistance ratio (RRR). The higher the RRR, the higher the thermal conductivity at cryogenic temperatures. As a specific evaluation method, the resistivity at 300 K (ρ300 K) (Ω·m) and the resistivity at 4.2 K (ρ4.2 K) (Ω·m) were measured using the four-terminal method, and the residual resistance (RRR) was calculated using the following formula: RRR=ρ ３００Ｋ / ρ ４．２ＫThe above results are summarized in Table 1. Note that the "area ratio of KAM values ​​< 1.0°" in Test No. 7 was measured after bonding and before heat treatment, but it is believed that heat treatment alleviates the disorder in crystal orientation and reduces the amount of strain, so it can be said that even after heat treatment after bonding, it was equal to or greater than the measured value before heat treatment (94%).

[0076]

[0077] The results in Table 1 are examined. Samples Nos. 1 to 7, which met all the requirements of this embodiment, had sufficient thermal conductivity (RRR of 1000 or more) at cryogenic temperatures. On the other hand, Test Nos. 8 and 9 did not meet the requirements of this embodiment and had insufficient thermal conductivity at cryogenic temperatures.

[0078] This application claims priority from Japanese Patent Application No. 2024-119649, filed July 25, 2024. Japanese Patent Application No. 2024-119649 is incorporated herein by reference.

[0079] 1 Flexible terminal 2 Flexible member 3 Metal terminal member 4 Joint portion

Claims

1. A flexible terminal in which a flexible member that is a twisted or braided wire containing multiple aluminum wires is joined to a metal terminal member, wherein the arithmetic mean value of the total content of major impurities, Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, in the multiple aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the area ratio of regions in the joined portion of the flexible member where the KAM value measured by the EBSD method is less than 1° in a cross section perpendicular to the longitudinal direction of the flexible member is 88% or more.

2. The flexible terminal according to claim 1, wherein the average KAM value is 0.7° or less.

3. A flexible terminal according to claim 1, wherein the average GOS value measured by the EBSD method in said cross section is 2° or less.

4. A flexible terminal according to claim 1, wherein the arithmetic mean value of the total content of the major impurities is 0.00005% by mass or more and 0.003% by mass or less.

5. The arithmetic mean diameter of the aluminum wires is 0.2 to 5 mm, and the cross-sectional area of ​​the flexible member is 1 to 1000 mm. ２ 2. The flexible terminal according to claim 1, wherein:

6. The flexible terminal according to claim 1, wherein the metal terminal member includes at least one material selected from the group consisting of copper and aluminum.

7. The flexible terminal according to claim 6, wherein the metal terminal member contains 90 mass % or more of copper or aluminum.

8. A flexible terminal according to claim 6, wherein the metal terminal member contains 99.5% by mass or more of copper or aluminum.

9. The flexible terminal according to any one of claims 1 to 8, which is a heat transfer material for cryogenic temperatures.

10. A method for ultrasonically bonding a flexible member that is a twisted or braided wire containing a plurality of aluminum wires to a metal terminal member, wherein the arithmetic mean value of the total content of Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, which are major impurities, in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the ultrasonic bonding is performed with ultrasonic energy of 0.1 to 20 J / mm ２ and the height of the flexible member in the joining direction is reduced by 30 to 90%.

11. The method of claim 10, further comprising heating the flexible terminal to 250 to 550°C after the ultrasonic bonding.

12. A method for manufacturing a flexible terminal, comprising crimping a flexible member, which is a twisted or braided wire containing a plurality of aluminum wires, to a metal terminal member, and heating the member to 250 to 550°C after the crimping, wherein the arithmetic mean value of the total content of the major impurities Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the crimping is performed so that the height of the flexible member in the joining direction is reduced by 30 to 90%.

13. The flexible terminal of claim 12, wherein said metal terminal member comprises copper or aluminum.

14. A method for manufacturing a flexible terminal, comprising crimping a flexible member that is a twisted or braided wire containing a plurality of aluminum wires to a metal terminal member that contains copper, wherein the arithmetic mean value of the total content of major impurities, Fe, Si, Cu, Mg, Ti, Mn, Zn, and Ga, in the plurality of aluminum wires is 0.00005% by mass or more and 0.1% by mass or less, and the crimping is performed so that the height of the flexible member in the joining direction is reduced by 30 to 90%.

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