Copper alloy

Abstract

The present invention addresses the problem of providing a long-strip-shaped copper alloy which has high hardness, is capable of suppressing material defects over a long period of time, and has excellent yield during mass production. The present invention is a long copper alloy having an equivalent line diameter of 0.5-5.0 mm, containing, in mass%, 9.00% < = Ni < = 15.00%, 0.30% < = Si < = 0.90%, 0.50% < = Al < = 2.00%, 2.00% < Sn < = 4.50%, and 0% < B < 0.010%, the remainder being Cu and unavoidable impurities, and having a Vickers hardness of 350 HV or more and an electrical conductivity of 8% IACS or more, the relationship ratio of Si, Al, Sn, and B satisfying 120 < = (1.7 Si + 1.2 Al + Sn) / 3.9 B < = 300.

Description

Technical Field

[0001] The present invention relates to a copper alloy having a long strip shape such as a wire or a rod. Background Art

[0002] Conventionally, as a copper alloy having a high hardness with a Vickers hardness of 350 HV or more, beryllium copper has been known. Beryllium copper is widely used for applications requiring high hardness such as needles of contact probes used in semiconductor inspections, needles for connectors, and bearings of sliding shafts of industrial high-speed sewing machines. On the other hand, beryllium has problems such as toxicity and availability, and therefore, in recent years, a beryllium-free copper alloy has been desired. As a beryllium-free copper alloy, for example, Patent Documents 1 and 2 have been proposed.

[0003] [Background Art Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 5743165

[0006] [Patent Document 2] Japanese Patent No. 7145070 Summary of the Invention

[0007] [Problems to be Solved by the Invention]

[0008] In Patent Document 1, the precipitation of Ni or Si is relatively fast, and high hardness can be relatively easily achieved, but there is a tendency to form precipitates with a relatively large diameter. If such precipitates fall off from the surface of the copper alloy, wire breakage or breakage may occur starting from the defective part, which becomes a cause of material defect. In particular, when such a copper alloy is used for the needle of a contact probe, the defective part on the needle surface comes into contact with the silicon wafer, which also becomes a cause of damaging the silicon wafer or the like to be inspected. Further, when the copper alloy of Patent Document 1 is processed to mass-produce a long strip shape (linear or rod-shaped product), there is a problem that the above-mentioned precipitates become a cause of wire breakage or breakage during its production process, resulting in a reduction in yield.

[0009] The copper alloy of Patent Document 2 makes the precipitates finer by containing Sn, and can solve the problems such as those of Patent Document 1. However, since the melting point of Sn is relatively low, the precipitates tend to aggregate at the grain boundaries. Therefore, the precipitates are not easily uniformly dispersed in the grains, and there is room for improvement in enhancing the hardness when forming a long strip shape.

[0010] The present invention has been made in view of the above actual situation, and its subject is to provide a long strip-shaped copper alloy having a relatively high hardness, capable of suppressing material defects for a long time, and having a good yield during mass production.

[0011] [Technical Means for Solving the Problems]

[0012] The present invention relates to a copper alloy, which is in the form of a long strip with an equivalent wire diameter of 0.5 to 5.0 mm. In terms of mass percentage, it contains 9.00% ≤ Ni ≤ 15.00%, 0.30% ≤ Si ≤ 0.90%, 0.50% ≤ Al ≤ 2.00%, 2.00% < Sn ≤ 4.50%, 0% < B < 0.010%. The balance is composed of Cu and inevitable impurities, and the Vickers hardness is 350 HV or more, and the conductivity is 8% IACS or more. The relational ratio of Si, Al, Sn, and B satisfies 120 ≤ (1.7Si + 1.2Al + Sn) / 3.9B ≤ 300.

[0013] In terms of mass percentage, the copper alloy of the present invention may contain 11.00% ≤ Ni ≤ 15.00%, 0.40% ≤ Si ≤ 0.90%, 1.00% ≤ Al ≤ 2.00%.

[0014] The above relational ratio of the copper alloy of the present invention may satisfy 160 ≤ (1.7Si + 1.2Al + Sn) / 3.9B ≤ 250.

[0015] Any of the above copper alloys of the present invention can be used as a needle for a contact probe.

[0016] [Effects of the Invention]

[0017] By adopting the above composition, the copper alloy of the present invention has high hardness, can suppress material defects for a long time, and has a good yield during mass production. Description of the Drawings

[0018] Figure 1 is a schematic cross-sectional view of a contact probe.

[0019] Figure 2 is an enlarged photograph of the tip of the needle for a contact probe of Comparative Material 1.

[0020] Figure 3 is an enlarged photograph of the tip of the needle for a contact probe of Comparative Material 2.

[0021] Figure 4 is a cross-sectional photograph of the needle for a contact probe of Comparative Material 3.

[0022] Figure 5 is an enlarged photograph of the surface of the needle for a contact probe of Comparative Material 3. Detailed Embodiments

[0023] Hereinafter, several embodiments of the present invention will be described based on the drawings.

[0024] Furthermore, the specific configurations shown in the following embodiments and drawings are for understanding the content of the present invention, and the present invention is not limited to the specific configurations of the drawings.​​​​​

[0025] The copper alloy of the present embodiment is a strip-shaped copper alloy with an equivalent wire diameter of 0.5 to 5.0 mm, and contains, by mass%, 9.00% ≤ Ni ≤ 15.00%, 0.30% ≤ Si ≤ 0.90%, 0.50% ≤ Al ≤ 2.00%, 2.00% < Sn ≤ 4.50%, 0% < B < 0.010%, and the balance is composed of Cu and inevitable impurities, and the conductivity is 8% IACS or more, the Vickers hardness is 350 HV or more, and the relational ratio of Si, Sn, and B satisfies 120 ≤ (1.7Si + 1.2Al + Sn) / 3.9B ≤ 300. Hereinafter, the above composition will be described in detail.

[0026] [Equivalent wire diameter]

[0027] The copper alloy of the present embodiment is provided in a strip shape with an equivalent wire diameter of 0.5 to 5.0 mm. In this specification, "strip shape" means an elongated wire, rod, etc. whose length direction and the direction of the cross section orthogonal thereto can be specified. The cross section of the strip shape is not limited to a circle, and may be, for example, a non-circular cross section shape such as an ellipse or a rectangle. Further, in this specification, "equivalent wire diameter" means the diameter of the cross section when the cross section of the strip shape is a true circle, and means the diameter of a true circle having the same area as the cross section in the case where the cross section is a non-circular shape such as an ellipse or a rectangle. The copper alloy having such an equivalent wire diameter is suitably used, for example, as a material for products requiring high hardness such as needles of contact probes, needles for connectors, and bearings of sliding shafts of industrial high-speed sewing machines.

[0028] Figure 1 A schematic cross-sectional view of the contact probe 1 is shown. The contact probe 1 is used to inspect the electrical characteristics of ICs, wafers, sockets, etc. In the conductivity test, the front end of the needle 2 is brought into contact with the inspection object surface to inspect the electrical characteristics at that location. The copper alloy of the present embodiment is suitably used as such a needle for a contact probe.

[0029] In the present embodiment, the reasons for specifying each element to the above components (unit: mass%) are as follows.

[0030] [Nickel (Ni)]

[0031] Ni of 9.00% or more is added to precipitate Ni2Si or Ni3Al and Ni3Sn2 in combination with Si, Al, and Sn, thereby increasing the hardness of the copper alloy. When the content of Ni is less than 9.00%, the amount of combination with the above elements also decreases, and a high hardness cannot be obtained. From this point of view, Ni is preferably set to 11.00% or more. On the contrary, if the content of Ni exceeds 15.00%, it is added beyond the range of the amount combined with Si, Al, and Sn, and there is a concern that the conductivity may decrease. From this point of view, the content of Ni is preferably set to 13.00% or less.

[0032] [Silicon (Si)]

[0033] Add more than 0.30% of Si to combine with Ni to precipitate Ni2Si, improving the hardness of the copper alloy. If the content of Si is low, the amount of combination with Ni decreases, and sufficient hardness improvement effect cannot be obtained. In terms of this view, Si is preferably set at 0.40% or more. On the other hand, adding a large amount of Si will form coarse Ni2Si compounds. Although this compound will improve the hardness of the copper alloy, it will reduce the toughness of the copper alloy, and there is even a concern that wire breakage is likely to occur during wire drawing processing or the like. Also, there is a concern about the risk of material defects caused by the shedding of coarse precipitates. In terms of this view, the content of Si is set at 0.90% or less, but if the effect of improving heat resistance is also considered, it is preferably set at 0.80% or less.

[0034] [Aluminum (Al)]

[0035] Add 0.50% or more of Al to combine with Ni to precipitate Ni3Al or NiAl, improving the hardness of the copper alloy. If the content of Al is low, the amount of combination with Ni decreases, and sufficient hardness improvement effect cannot be obtained. In terms of this view, Al is preferably set at 1.00% or more. On the other hand, adding a large amount of Al will form an excessive amount of Ni3Al compounds. Although this compound will improve the hardness of the copper alloy, it will reduce the toughness of the copper alloy, and there is even a concern that wire breakage is likely to occur during wire drawing processing or the like. In terms of this view, the content of Al is set at 2.00% or less, but if the effect of improving heat resistance is also considered, it is preferably set at 1.80% or less.

[0036] [Tin (Sn)]

[0037] Add more than 2.00% of Sn to combine with Ni to precipitate Ni3Sn2 or Ni3Sn, improving the hardness of the copper alloy and suppressing the enlargement of the diameter of the precipitates (promoting micro-refinement). If the content of Sn is low, the amount of combination with Ni decreases, and in addition to not obtaining sufficient hardness improvement effect, precipitates with relatively large diameters are likely to precipitate. On the other hand, adding a large amount of Sn raises concerns about material fracture during wire drawing or forging due to the reduction of the strength of the grain boundaries by excessive Sn. In terms of this view, the content of Sn is set at 4.50% or less, preferably set at 3.50% or less.

[0038] [Boron (B)]

[0039] Adding more than 0% of B can improve the corrosion resistance and make precipitates such as Ni2Si, Ni3Al, and Ni3Sn2 disperse more finely, thereby improving the hardness of the copper alloy. It is preferably set at 0.003% or more. On the other hand, adding a large amount of B will not only reduce the toughness or workability of the copper alloy, but also there is a concern that pores (so-called "nests") will be generated everywhere in the material. From this point of view, the content of B is set to be less than 0.010%, preferably set to be 0.009% or less.

[0040] [Inevitable impurities]

[0041] The copper alloy of this embodiment contains the above component elements, and the remaining part is composed of inevitable impurities and Cu. As inevitable impurities, for example, O, Zn, Mn, Fe, S, etc. can be cited. In particular, O will form oxides and deteriorate the plastic workability, and also reduce the electrical conductivity. Also, S and Fe will also form harmful coarse inclusions. Therefore, the total of these is preferably set to 0.20% or less. Also, the content of each impurity is preferably set to about 0.10% or less respectively.

[0042] [Relationship ratio of Si, Al, Sn, and B]

[0043] In order to improve the electrical conductivity and workability of copper alloys, it is only necessary to increase the content of Cu. On the other hand, in order to increase the hardness of copper alloys, it is necessary to precipitate more Ni2Si, Ni3Al, NiAl, Ni3Sn2 and Ni3Sn in the copper alloy. Regarding copper alloys in the form of long strips such as wire rods or bars, the inventors focused on the relational ratio of Si, Al and Sn to B (hereinafter, there will be cases where it is simply referred to as the "relational ratio"). And by setting this relational ratio to various different relational ratios and attempting experiments, it was found that: if the content ranges of the above-mentioned Si, Al and Sn are taken as a premise and the above-mentioned relational ratio is specified within a fixed range, the hardness of the copper alloy can be increased by the precipitation of precipitates, while suppressing the shedding and defect of precipitates from the surface of the copper alloy during the processing of copper alloy products or during long-term use. Specifically, it was proven that when the value of the above-mentioned relational ratio (1.7Si + 1.2Al + Sn) / 3.9B is less than 120, the content of B is excessive relative to the contents of Si, Al and Sn, resulting in a decrease in the toughness of the copper alloy, causing wire breakage or breakage during the processing of products and a decrease in the yield rate. On the contrary, it can be seen that if the value of the above-mentioned relational ratio (1.7Si + 1.2Al + Sn) / 3.9B exceeds 300, the content of B is insufficient relative to the contents of Si, Al and Sn. At this time, the precipitates of Ni2Si, Ni3Al, NiAl, Ni3Sn2 and Ni3Sn cannot be sufficiently dispersed. And the non-dispersion of precipitates in copper alloys in the form of long strips such as wire rods or bars will cause "the shedding of precipitates due to the continuous impact force during the processing of copper alloy products or after product formation, resulting in defects". From the above viewpoints, the relational ratio (1.7Si + 1.2Al + Sn) / 3.9B of the copper alloy of this embodiment is specified within the range of 120 or more and 300 or less, and more preferably within the range of 160 or more and 250 or less.

[0044] [Vickers hardness (HV)]

[0045] The Vickers hardness of the copper alloy of this embodiment is set to 350 HV or more. The Vickers hardness is measured based on JIS-Z2244. Regarding the copper alloy of this embodiment, as the hardness that can withstand the processing and repeated use (impact force, etc.) of products, it is specified to be 350 HV or more in terms of Vickers hardness. When the Vickers hardness of the copper alloy is less than 350 HV, for example, it is not suitable for applications that repeatedly withstand a large impact force represented by the needle for contact probes. From this viewpoint, the Vickers hardness of the copper alloy is preferably set to 380 HV or more, and more preferably set to 400 HV or more.

[0046] [Electrical conductivity (%IACS)]

[0047] Set the conductivity of the copper alloy of this embodiment to 8% IACS or more. Thus, the copper alloy of this embodiment can be used, for example, as various product materials requiring conductivity, represented by the needles of contact probes for semiconductor inspection. Also, regarding the copper alloy of this embodiment, in terms of being suitably used for the above-mentioned uses, as long as the equivalent wire diameter is 0.5 to 5.0 mm and its electrical property has a conductivity of 8% IACS or more, it is sufficient, and it can preferably be set to 10% IACS or more. Furthermore, the conductivity of the copper alloy is measured by the four-terminal method (specimen length 100 mm) in a constant temperature bath at 20°C in accordance with JIS-C3002 "Test Methods for Copper and Aluminum Wires for Electrical Use".

[0048] The copper alloy of this embodiment can be manufactured in the same manner as general alloy wire rods. For example, first, a copper alloy material having the above chemical composition is melted using a continuous casting machine, and a long bar-shaped rod is manufactured by continuous casting. Subsequently, for this rod, for example, annealing and cold drawing are repeatedly performed while reducing the diameter to a specific wire diameter, thereby manufacturing a long bar-shaped (wire) copper alloy.

[0049] [Examples]

[0050] Hereinafter, more specific examples of the present invention will be described, but the present invention is not limited to these examples.

[0051] Copper alloy materials having the chemical compositions shown in Table 1 are melted respectively using a continuous casting machine, and rods are manufactured by continuous casting. Subsequently, annealing and cold drawing are performed on the rods two or more times to manufacture copper alloy wires having an equivalent wire diameter range of 1.0 to 5.0 mm. The annealing is performed in the range of 600°C to 1000°C.

[0052] And the conductivity, Vickers hardness, and yield rate during production of the above copper alloy wires are evaluated.

[0053] Also, needles for contact probes are manufactured using the above copper alloy wires, and for these needles, a continuous conduction test (burn-in test) is performed in an environment at a temperature of 250°C. In the continuous conduction test, on the inspection surface of a silicon wafer, these needles are continuously repeatedly contacted and non-contacted 10,000 times. Subsequently, the state (presence or absence of defects, etc.) of the needles after the test is evaluated.

[0054] Table 1 shows the chemical compositions and evaluation results of the copper alloys of the inventive materials and comparative materials

[0055]

[0056]

[0057]

[0058] [Invention Materials]

[0059] It can be clearly confirmed from Table 1 that the Vickers hardness of the invention materials 1 to 30 is above 350 HV, and the conductivity is above 8% IACS, which has excellent hardness and conductivity. In addition, the invention materials did not break or break during the production process of long objects such as wires, and no defects such as flaws were found on the surface or inside of the wires after processing. Furthermore, in the continuous conductivity test, the needle of the contact probe made of the invention material did not have defects such as breakage, defect, and thermal deformation during the test.

[0060] [Comparison material 1]

[0061] Comparative material 1 is an example in which Ni, Si, Sn and B do not satisfy the contents of the chemical components specified by the present invention and do not satisfy the relationship ratio. Specifically, Comparative material 1 is an example in which Ni is added less, Si is added more, Sn is added less, B is added more, and the value of the relationship ratio is also smaller. It can be seen that although this type of comparative material 1 satisfies the conductivity, it cannot obtain sufficient Vickers hardness. In addition, since the value of the relationship ratio is small, the wire is broken due to the influence of precipitates during the processing into wire. In addition, after the continuous conductivity test, the contact probe needle made using Comparative material 1 was confirmed to be defective at the front end of the needle. Figure 2 An enlarged photograph of the tip of the needle of Comparative Material 1 after the continuous conduction test is shown. It was confirmed that the defect at the tip of the needle was caused by the presence of precipitates with a particle size of about 10 μm to about 17 μm.

[0062] [Comparison material 2]

[0063] Comparative material 2 is an example that satisfies the numerical range of the relationship ratio specified in the present invention, but the contents of Si, Sn and B as its premise are outside the range specified in the present invention. Specifically, Comparative material 2 is an example in which Si is less added, Sn is more added, and B is more added. It was confirmed that Comparative material 2 has a Vickers hardness slightly higher than that of Comparative material 1, but it does not reach 350HV, and the conductivity is also low. In addition, Comparative material 2 did not produce disconnection or breakage during the production process, but the needle of the contact probe using Comparative material 2 produced the following near the tip of the needle (the contact part with the silicon wafer) after a continuous conductivity test. Figure 3 The fracture shown.

[0064] [Comparison material 3]

[0065] Comparative material 3 is an example in which Si and B do not satisfy the content of the specific chemical composition of the present invention and do not satisfy the relational ratio. Specifically, comparative material 3 is an example in which the addition of Si is less, the addition of Sn is more, the addition of B is more, and the value of the relational ratio is small. In comparative material 3, it was confirmed that both the conductivity and the Vickers hardness were low. Also, in comparative material 3, it was confirmed that breakage of the material occurred during wire drawing, after wire drawing, and after the continuous conductivity test. Further observing the cross-section of comparative material 3 in detail, as a result, as shown in Figure 4 shown, it was confirmed that several nests a (micro-pores) with a width of about 10 to 350 μm were formed inside the cross-section. Also, as shown in Figure 5 shown, it was confirmed that nests a were also generated at various locations on the material surface with a size of 10 to 50 μm in width. It is speculated that the breakage of the material occurred starting from these nests a.

[0066] [Comparative material 4]

[0067] Comparative material 4 is an example in which Si, Sn, and B do not satisfy the content of the specific chemical composition of the present invention and do not satisfy the relational ratio. Specifically, comparative material 4 is an example in which the addition of Si is less, the addition of Sn is more, the addition of B is more, and the relational ratio cannot be calculated. In comparative material 4, wire breakage occurred during the wire drawing process. Also, in the continuous conductivity test, the contact probe needle using comparative material 4 broke as shown in Figure 3 shown, in the same manner as comparative material 2.

[0068] [Comparative material 5]

[0069] Comparative material 5 is an example that satisfies the numerical range of the specific relational ratio of the present invention, but the contents of Al and Sn as its premise are outside the specific range of the present invention. Specifically, comparative material 5 is an example in which the addition of Al is less and the addition of Sn is more. Comparative material 5 can obtain sufficient conductivity, but the Vickers hardness is insufficient. Also, no wire breakage or breakage occurred during the production process of comparative material 5, but after the continuous conductivity test was carried out, it was confirmed that the needle of the contact probe was thermally deformed and it was difficult to use continuously.

[0070] [Comparative material 6]

[0071] Comparative material 6 is an example that contains beryllium and does not satisfy the specific chemical composition and relational ratio of the present invention. Comparative material 5 can obtain sufficient conductivity and Vickers hardness, but, like comparative material 1, wire breakage occurred due to the presence of precipitates during the process of processing into wire. Also, a contact probe needle was made using comparative material 5 and the continuous conductivity test was carried out. As a result, it was confirmed that, like comparative material 1, the front end defect as shown in Figure 2 occurred.

[0072] Based on the above discussion, it can also be clearly confirmed that in order to solve the problems of the present invention, it is important to satisfy both the content and the relational ratio of the chemical components of the present invention.

[0073] Reference numeral

[0074] 1: Contact probe

[0075] 2: Needle

Claims

1. A copper alloy in the form of a long strip having an equivalent wire diameter of 0.5 to 5.0 mm, In terms of mass%, it comprises 9.00%≤Ni≤15.00%, 0.30%≤Si≤0.90%, 0.50%≤Al≤2.00%, 2.00%<Sn≤4.50%, 0%<B<0.010%, and the remainder is composed of Cu and unavoidable impurities, and Vickers hardness is 350HV or above. The conductivity is above 8% IACS. The relationship ratio of Si, Al, Sn and B satisfies 120≤(1.7Si+1.2Al+Sn) / 3.9B≤300.

2. The copper alloy according to claim 1, wherein In terms of mass%, the content is 11.00%≤Ni≤15.00%, 0.40%≤Si≤0.90%, and 1.00%≤Al≤2.00%.

3. The copper alloy according to claim 1 or 2, wherein: The above relationship ratio satisfies 160≤(1.7Si+1.2Al+Sn) / 3.9B≤250. 4 . A contact probe needle using the copper alloy according to claim 1 .

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