Copper alloy

Abstract

[Problem] To provide a copper alloy having a long form with which it is possible to suppress loss of material over a long period of time and that has good yield in mass production, while being provided with a high hardness.　[Solution] A copper alloy having a long form in which the equivalent line diameter is 0.5-5.0 mm, the copper alloy including, 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%, with the balance made up by Cu and unavoidable impurities. The copper alloy has a Vickers hardness of 350 HV or above, a conductivity of 8% IACS or above, and a relationship ratio of Si, Al, Sn, and B satisfying 120 ≤ (1.7Si + 1.2Al + Sn) / 3.9B ≤ 300.

Description

copper alloy

[0001] The present invention relates to a copper alloy in a long form such as a wire rod or a bar.

[0002] Beryllium copper has been known as a copper alloy having a high hardness of 350 HV or more in Vickers hardness. Beryllium copper is widely used in applications requiring high hardness, such as pins of contact probes used in semiconductor inspection, pins for connectors, and sliding shaft bearings for industrial high-speed sewing machines. However, because beryllium has problems such as toxicity and availability, there has been a demand in recent years for copper alloys that do not contain beryllium. Beryllium-free copper alloys have been proposed, for example, in Patent Documents 1 and 2.

[0003] Patent No. 5743165 Patent No. 7145070

[0004] In the copper alloy disclosed in Patent Document 1, Ni and Si precipitate rapidly and high hardness can be achieved relatively easily, but large precipitates tend to form. When such precipitates fall off the surface of the copper alloy, they can cause material defects, such as wire breakage or breakage originating from the defected areas. In particular, when this type of copper alloy is used for the pins of contact probes, the defected areas on the pin surface can come into contact with the silicon wafer, causing damage to the silicon wafer being inspected. Furthermore, when the copper alloy disclosed in Patent Document 1 is processed into mass-produced long products (wire- or rod-shaped products), the above-mentioned precipitates can cause wire breakage or breakage during the production process, resulting in a problem of reduced yield.

[0005] The copper alloy of Patent Document 2 contains Sn, which refines precipitates and solves the problems of Patent Document 1. However, since Sn has a relatively low melting point, precipitates tend to gather at grain boundaries. This makes it difficult for the precipitates to be uniformly dispersed within the grains, and there is room for improvement in improving hardness when the alloy is formed into a long shape.

[0006] The present invention has been devised in view of the above-mentioned circumstances, and an object of the present invention is to provide a long copper alloy that has high hardness, can suppress material damage over a long period of time, and has a good yield when mass-produced.

[0007] The present invention relates to a copper alloy in a long form having an equivalent wire diameter of 0.5 to 5.0 mm, which 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 being Cu and unavoidable impurities, and which has a Vickers hardness of 350 HV or more, an electrical conductivity of 8% IACS or more, and a relationship between Si, Al, Sn, and B that satisfies 120≦(1.7Si+1.2Al+Sn) / 3.9B≦300.

[0008] The copper alloy of the present invention may contain, in mass %, 11.00%≦Ni≦15.00%, 0.40%≦Si≦0.90%, and 1.00%≦Al≦2.00%.

[0009] In the copper alloy of the present invention, the relationship ratio may satisfy 160≦(1.7Si+1.2Al+Sn) / 3.9B≦250.

[0010] Any of the copper alloys of the present invention may be used as pins for contact probes.

[0011] By adopting the above-mentioned constitution, the copper alloy of the present invention has high hardness, can suppress material chipping over a long period of time, and has a good yield in mass production.

[0012] Fig. 1 is a schematic cross-sectional view of a contact probe; Fig. 2 is an enlarged photograph of the tip of a pin for a contact probe of comparative material 1; Fig. 3 is an enlarged photograph of the tip of a pin for a contact probe of comparative material 2; Fig. 4 is a cross-sectional photograph of a pin for a contact probe of comparative material 3; Fig. 5 is an enlarged photograph of the surface of a pin for a contact probe of comparative material 3.

[0013] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. Note that the specific configurations shown in the following embodiments and drawings are for the purpose of understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0014] The copper alloy of this embodiment is a long copper alloy having 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%, with the balance being Cu and inevitable impurities, and has an electrical conductivity of 8%IACS or more, a Vickers hardness of 350HV or more, and a relative ratio of Si, Sn, and B that satisfies 120≦(1.7Si+1.2Al+Sn) / 3.9B≦300. These components will be described in detail below.

[0015] [Equivalent Wire Diameter] The copper alloy of this embodiment is in a long form having an equivalent wire diameter of 0.5 to 5.0 mm. In this specification, "long form" refers to a thin wire, rod, or the like, which can define a longitudinal direction and a cross-sectional direction perpendicular to the longitudinal direction. The cross section of the long form is not limited to a circular shape, and may be a non-circular cross-sectional shape such as an ellipse or rectangle. Furthermore, in this specification, "equivalent wire diameter" refers to the diameter of a cross section of a long form when the cross section is a perfect circle. However, in the case of a non-circular cross section such as an ellipse or rectangle, it refers to the diameter of a perfect circle having an area equal to the cross section. Copper alloys having such an equivalent wire diameter are suitable as materials for products requiring high hardness, such as contact probe pins, connector pins, and sliding shaft bearings for industrial high-speed sewing machines.

[0016] 1 shows a schematic cross-sectional view of a contact probe 1. The contact probe 1 is used to test the electrical characteristics of ICs, wafers, sockets, etc. In a conductivity test, the tip of the pin 2 is brought into contact with the surface to be tested, and the electrical characteristics at that surface are tested. The copper alloy of this embodiment is suitable for use as a pin for such a contact probe.

[0017] In this embodiment, the reason why the amounts of the elements are specified as above (unit: mass %) is as follows.

[0018] [Nickel (Ni)] Ni combines with Si, Al, and Sn to precipitate NiSi, NiAl, and NiSn, thereby improving the hardness of the copper alloy. Ni content less than 9.00% reduces the amount of Ni combined with the above elements, making it impossible to achieve high hardness. From this perspective, the Ni content is preferably 11.00% or more. Conversely, if the Ni content exceeds 15.00%, the Ni content exceeds the amount that combines with Si, Al, and Sn, which may result in a decrease in electrical conductivity. From this perspective, the Ni content is preferably 13.00% or less.

[0019] [Silicon (Si)] Si is added in an amount of 0.30% or more to combine with Ni to precipitate NiSi and improve the hardness of the copper alloy. If the Si content is low, the amount of Si combined with Ni decreases, and sufficient hardness improvement effect cannot be obtained. From this perspective, the Si content is preferably 0.40% or more. On the other hand, adding a large amount of Si generates coarse NiSi compounds. Although these compounds increase the hardness of the copper alloy, they may reduce the toughness of the copper alloy, which may ultimately lead to wire breakage during wire drawing. Furthermore, they may increase the risk of material chipping due to the detachment of coarse precipitates. From this perspective, the Si content is set to 0.90% or less, but taking into account the effect of improving heat resistance, it is preferably set to 0.80% or less.

[0020] [Aluminum (Al)] Al is added in an amount of 0.50% or more to combine with Ni to precipitate NiAl or NiAl, thereby improving the hardness of the copper alloy. A low Al content reduces the amount of Al combined with Ni, preventing sufficient improvement in hardness. From this perspective, the Al content is preferably 1.00% or more. On the other hand, adding a large amount of Al generates excessive NiAl compounds. While these compounds increase the hardness of the copper alloy, they also reduce the toughness of the copper alloy, potentially making it more susceptible to wire breakage during wire drawing. From this perspective, the Al content is set to 2.00% or less, but taking into account the effect of improving heat resistance, it is preferably set to 1.80% or less.

[0021] [Tin (Sn)] Sn combines with Ni to precipitate Ni3Sn2 or Ni3Sn, improving the hardness of the copper alloy and suppressing the increase in the diameter of the precipitates (promoting refinement). Therefore, Sn is added in an amount of more than 2.00%. A low Sn content reduces the amount of Sn combined with Ni, resulting in insufficient improvement in hardness and the tendency for relatively large precipitates to precipitate. On the other hand, excessive Sn addition may reduce the strength of the grain boundaries, potentially causing material cracks during wire drawing or forging. From this perspective, the Sn content is set to 4.50% or less, preferably 3.50% or less.

[0022] [Boron (B)] B is added in an amount greater than 0%, preferably 0.003% or more, to improve corrosion resistance and to further improve the hardness of the copper alloy by dispersing precipitates such as NiSi, NiAl, and NiSn. On the other hand, the addition of a large amount of B not only reduces the toughness and workability of the copper alloy, but also may cause holes (so-called "cavities") to form in various places in the material. From this perspective, the B content is set to less than 0.010%, preferably 0.009% or less.

[0023] [Inevitable Impurities] The copper alloy of this embodiment contains the above-mentioned component elements, with the remainder being composed of inevitable impurities and Cu. Examples of inevitable impurities include O, Zn, Mn, Fe, and S. In particular, O forms oxides that deteriorate plastic workability and reduce electrical conductivity, and S and Fe also form harmful coarse inclusions, so the total content of these elements is preferably 0.20% or less. Furthermore, the content of each individual impurity is preferably approximately 0.10% or less.

[0024] [Relational Ratio of Si, Al, Sn, and B] Increasing the Cu content can improve the electrical conductivity and workability of a copper alloy. On the other hand, increasing the hardness of a copper alloy requires the precipitation of larger amounts of NiSi, NiAl, NiAl, NiSn, and NiSn in the copper alloy. The inventors focused on the relative ratio of Si, Al, and Sn to B (hereinafter, simply referred to as the "relative ratio") in copper alloys having a long form such as wire or rod. Experiments were conducted with various variations in this relative ratio, and they found that, assuming the above-mentioned ranges of Si, Al, and Sn contents, specifying the relative ratio within a certain range can simultaneously improve the hardness of the copper alloy through the precipitation of precipitates and suppress the detachment and chipping of precipitates from the material surface during product processing and long-term use of the copper alloy. Specifically, it was found that when the value of the relationship ratio (1.7Si + 1.2Al + Sn) / 3.9B is less than 120, the B content becomes excessive relative to the Si, Al, and Sn contents, resulting in a decrease in the toughness of the copper alloy, causing wire breakage and fracture during product processing, and reducing yield. Conversely, when the value of the relationship ratio (1.7Si + 1.2Al + Sn) / 3.9B exceeds 300, the B content becomes insufficient relative to the Si, Al, and Sn contents, and this in turn results in insufficient dispersion of NiSi, NiAl, NiAl, NiSn, and NiSn precipitates. Furthermore, non-dispersion of precipitates in long copper alloys such as wires and rods can cause defects due to precipitate shedding caused by continuous impact forces during product processing and after the copper alloy is manufactured. From the above viewpoints, the copper alloy of this embodiment specifies the relative ratio (1.7Si+1.2Al+Sn) / 3.9B to be in the range of 120 or more and 300 or less, and more preferably 160 or more and 250 or less.

[0025] [Vickers Hardness (HV)] The copper alloy of this embodiment has a Vickers hardness of 350 HV or more. The Vickers hardness is measured based on JIS-Z2244. The copper alloy of this embodiment is specified to have a Vickers hardness of 350 HV or more as a hardness that can withstand processing into products and repeated use (impact force, etc.). If the Vickers hardness of the copper alloy is less than 350 HV, it is not suitable for use in applications that are repeatedly subjected to large impact forces, such as, for example, pins for contact probes. From this perspective, the Vickers hardness of the copper alloy is preferably 380 HV or more, and more preferably 400 HV or more.

[0026] [Electrical Conductivity (%IACS)] The copper alloy of this embodiment has an electrical conductivity of 8%IACS or more. This allows the copper alloy of this embodiment to be used as a material for various products requiring electrical conductivity, such as contact probe pins for semiconductor testing. Since the copper alloy of this embodiment is preferably used for the above-mentioned applications, it has an equivalent wire diameter of 0.5 to 5.0 mm. It is sufficient for the copper alloy to have an electrical conductivity of 8%IACS or more, but preferably 10%IACS or more. The electrical conductivity of the copper alloy is measured by a four-terminal method (sample length: 100 mm) in a thermostatic chamber at 20°C in accordance with JIS-C3002, "Test Methods for Electrical Copper Wire and Aluminum Wire."

[0027] The copper alloy of this embodiment can be produced in the same manner as a general alloy wire. For example, first, a copper alloy material having the above-described chemical composition is melted using a continuous casting machine, and a long rod material is produced by continuous casting. Next, this rod material is thinned to a predetermined wire diameter by, for example, repeatedly performing annealing and cold wiredrawing, thereby producing a long copper alloy (wire material).

[0028] More specific examples of the present invention will be described below, but the present invention is not limited to these examples.

[0029] Copper alloy materials having the chemical compositions shown in Table 1 were melted and continuously cast using a continuous casting machine to produce rod materials. The rod materials were then annealed and cold drawn at least twice to produce copper alloy wire materials with equivalent wire diameters ranging from 1.0 to 5.0 mm. Annealing was performed at temperatures ranging from 600°C to 1000°C.

[0030] The copper alloy wire was evaluated for electrical conductivity, Vickers hardness, and production yield.

[0031] Furthermore, pins for contact probes were manufactured using the above copper alloy wire, and a continuous conductivity test (burn-in test) was performed on these pins in an atmosphere at a temperature of 250°C. In the continuous conductivity test, these pins were repeatedly brought into contact with and out of contact with the inspection surface of a silicon wafer 10,000 times. Then, the condition of the pins after the test (presence or absence of defects, etc.) was evaluated.

[0032] Table 1 shows the chemical compositions and evaluation results of the copper alloys of the invention material and the comparative material.

[0033]

[0034] [Inventive Materials] As is clear from Table 1, Inventive Materials 1 to 30 have a Vickers hardness of 350 HV or more and a conductivity of 8% IACS or more, confirming their excellent hardness and conductivity. Furthermore, none of the inventive materials experienced breakage or fracture during the manufacturing and processing of long objects such as wire, and no defects such as scratches were found on the surface or inside of the wire after processing. Furthermore, the pins of contact probes manufactured using the inventive materials did not experience any cracks, defects, or thermal deformation during the continuous conductivity test.

[0035] [Comparative Material 1] Comparative Material 1 is an example that does not meet the chemical component contents specified by the present invention with respect to Ni, Si, Sn, and B, and also does not meet the relative ratios. Specifically, Comparative Material 1 is an example that contains low Ni, high Si, low Sn, and high B, and also has a small relative ratio value. It can be seen that Comparative Material 1 has satisfactory electrical conductivity, but does not achieve sufficient Vickers hardness. Furthermore, the low relative ratio value indicates that breakage occurred due to the influence of precipitates during the wire processing process. Furthermore, after a continuous conductivity test, damage was confirmed at the tip of the contact probe pin manufactured using Comparative Material 1. Figure 2 shows an enlarged photograph of the pin tip of Comparative Material 1 after the continuous conductivity test. It was confirmed that the damage at the pin tip was caused by the presence of precipitates with a particle size of approximately 10 μm to approximately 17 μm.

[0036] [Comparative Material 2] Comparative Material 2 satisfies the numerical range of the relational ratio specified by the present invention, but the contents of Si, Sn, and B, which are the prerequisites for the ratio, are outside the range specified by the present invention. Specifically, Comparative Material 2 is an example in which low Si, high Sn, and high B are added. Comparative Material 2 has a Vickers hardness slightly higher than Comparative Material 1, but does not reach 350 HV, and it was confirmed that its conductivity is also low. Furthermore, Comparative Material 2 did not suffer from breakage or disconnection during the production process, but after a continuous conductivity test, the pin of a contact probe using Comparative Material 2 developed a crack near the tip of the pin (the point of contact with the silicon wafer), as shown in Figure 3.

[0037] [Comparative Material 3] Comparative Material 3 is an example that does not satisfy the chemical component contents specified by the present invention with respect to Si and B, and also does not satisfy the relevant ratios. Specifically, Comparative Material 3 is an example that contains low Si, high Sn, and high B, resulting in a small value for the relevant ratios. It was confirmed that Comparative Material 3 had low electrical conductivity and low Vickers hardness. Furthermore, it was confirmed that Comparative Material 3 experienced breakage during and after wiredrawing and after continuous electrical conductivity testing. Further detailed observation of the cross section of Comparative Material 3 revealed the formation of several voids a (micropores) approximately 10 to 350 μm wide within the cross section, as shown in FIG. 4. Furthermore, as shown in FIG. 5, it was confirmed that voids a, 10 to 50 μm wide, were present in various locations on the surface of the material. It is presumed that the breakage of the material originated from these voids a.

[0038] [Comparative Material 4] Comparative Material 4 is an example that does not satisfy the chemical component contents specified by the present invention with respect to Si, Sn, and B, and also does not satisfy the relevant ratios. Specifically, Comparative Material 4 contains little Si, much Sn, and much B, making it an example where the relevant ratios cannot be calculated. In Comparative Material 4, wire breakage occurred during the wire drawing process. Furthermore, in the contact probe pin using Comparative Material 4, cracks occurred as shown in Figure 3 in the continuous conductivity test, similar to Comparative Material 2.

[0039] [Comparative Material 5] Comparative Material 5 satisfies the numerical range of the relational ratio specified by the present invention, but the content of Al and Sn, which are the prerequisites for the ratio, is outside the range specified by the present invention. Specifically, Comparative Material 5 is an example in which the Al content is low and the Sn content is high. Comparative Material 5 has sufficient conductivity, but does not have sufficient Vickers hardness. Furthermore, although Comparative Material 5 did not experience any breakage or fracture during the production process, a continuous conductivity test revealed that the contact probe pin was thermally deformed, making continuous use difficult.

[0040] [Comparative Material 6] Comparative Material 6 contains beryllium and is an example that does not satisfy the chemical composition and related ratios specified by the present invention. Comparative Material 5 had sufficient conductivity and Vickers hardness, but like Comparative Material 1, breakage occurred during the processing into wire due to the presence of precipitates. In addition, a contact probe pin was made using Comparative Material 5 and a continuous conductivity test was conducted, and it was confirmed that the tip was chipped as shown in Figure 2, just like Comparative Material 1.

[0041] As is clear from the above considerations, it has been confirmed that in order to solve the problems of the present invention, it is important to satisfy both the contents and the relative ratios of the chemical components of the present invention.

[0042] 1 Contact probe 2 pins

Claims

1. A copper alloy in a long form with an equivalent wire diameter of 0.5 to 5.0 mm, containing, 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%, with the balance being Cu and unavoidable impurities, having a Vickers hardness of 350HV or more, an electrical conductivity of 8%IACS or more, and a relationship ratio of Si, Al, Sn, and B that satisfies 120≦(1.7Si+1.2Al+Sn) / 3.9B≦300.

2. The copper alloy of claim 1, comprising, by weight, 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 relationship ratio satisfies 160≦(1.7Si+1.2Al+Sn) / 3.9B≦250.

4. A pin for a contact probe using the copper alloy according to claim 1 or 2.

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