JP7610667B1 - Copper alloy - Google Patents

Abstract

The present invention provides a long copper alloy that has high hardness, can suppress material damage over a long period of time, and has a good yield during mass production.
[Solution] A long copper alloy having 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 relational ratio of Si, Al, Sn and B satisfying 120≦(1.7Si+1.2Al+Sn)/3.9B≦300.
[Selected Figure] Figure 1

Description

The present invention relates to a copper alloy having a long shape such as a wire or rod.

Beryllium copper has been known as a copper alloy with high hardness, with a Vickers hardness of 350 HV or more. Beryllium copper is widely used in applications requiring high hardness, such as contact probe pins used in semiconductor inspection, connector pins, and sliding shaft bearings for industrial high-speed sewing machines. However, since beryllium has problems such as toxicity and availability, there has been a demand in recent years for copper alloys that do not contain beryllium. Examples of copper alloys that do not contain beryllium are proposed in Patent Documents 1 and 2.

Patent No. 5743165 Patent No. 7145070

In Patent Document 1, Ni and Si precipitate quickly and high hardness can be achieved relatively easily, but large precipitates tend to be generated. When such precipitates fall off the surface of the copper alloy, they cause material defects such as breaks and fractures starting from the defect points. In particular, when this type of copper alloy is used for the pins of contact probes, the defect points on the pin surface come into contact with the silicon wafer, causing damage to the silicon wafer to be inspected. In addition, when the copper alloy of Patent Document 1 is processed to mass-produce long products (line or rod-shaped products), there is a problem that the above-mentioned precipitates cause breaks and fractures during the production process, reducing the yield.

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

The present invention was devised in consideration of the above-mentioned circumstances, and aims to provide a long copper alloy that has high hardness, can suppress material loss over a long period of time, and has a good yield rate during mass production.

The present invention is a copper alloy in a long form with 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%, with the balance being Cu and unavoidable impurities, has a Vickers hardness of 350HV or more, an electrical conductivity of 8%IACS or more, and the relative ratios of Si, Al, Sn, and B satisfy 120≦(1.7Si+1.2Al+Sn)/3.9B≦300.

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

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

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

By adopting the above-mentioned configuration, the copper alloy of the present invention has high hardness, can suppress material loss over a long period of time, and has a good yield during mass production.

FIG. 2 is a schematic cross-sectional view of a contact probe. 1 is an enlarged photograph of the tip of a pin for a contact probe of comparative material 1. 1 is an enlarged photograph of the tip of a pin for a contact probe of comparative material 2. 1 is a cross-sectional photograph of a pin for a contact probe of comparative material 3. 1 is an enlarged photograph of the surface of a pin for a contact probe of comparative material 3.

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 intended to facilitate understanding of the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

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

[Equivalent wire diameter]
The copper alloy of this embodiment is in a long form with an equivalent wire diameter of 0.5 to 5.0 mm. In this specification, the term "long form" refers to a thin and long wire, rod, or the like that can define the longitudinal direction and the direction of the cross section perpendicular thereto. The cross section of the long form is not limited to a circular shape, and may be a non-circular cross section such as an ellipse or a rectangle. In this specification, the term "equivalent wire diameter" refers to the diameter of the cross section when the cross section of the long form is a perfect circle, but when the cross section is a non-circular shape such as an ellipse or a rectangle, it refers to the diameter of a perfect circle that is equal to the area of the cross section. Copper alloys having such an equivalent wire diameter are suitable as product materials that require high hardness, such as contact probe pins, connector pins, and industrial high-speed sewing machine sliding shaft bearings.

Figure 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.

In this embodiment, the reasons for specifying the amounts of each element as above (unit: mass%) are as follows:

[Nickel (Ni)]
Ni is added in an amount of 9.00% or more to combine with Si, Al, and Sn, precipitate Ni ₂ Si, Ni ₃ Al, and Ni ₃ Sn ₂ , and improve the hardness of the copper alloy. If the Ni content is less than 9.00%, the amount of combination with each of the above elements is also reduced, and high hardness cannot be obtained. From this viewpoint, Ni is preferably set to 11.00% or more. On the other hand, if the Ni content exceeds 15.00%, Ni is added in an amount that exceeds the amount that combines with Si, Al, and Sn, which may lead to a decrease in electrical conductivity. From this viewpoint, Ni content is preferably set to 13.00% or less.

[Silicon (Si)]
Si is added in an amount of 0.30% or more to combine with Ni to precipitate Ni ₂ Si and improve the hardness of the copper alloy. If the content of Si is low, the amount of combination with Ni decreases, and sufficient improvement in hardness cannot be obtained. From this viewpoint, Si is preferably set to 0.40% or more. On the other hand, addition of a large amount of Si generates coarse Ni ₂ Si compounds. Although this compound increases the hardness of the copper alloy, it may reduce the toughness of the copper alloy, and may be prone to cause breakage during wire drawing. In addition, there is a risk of increasing the risk of material chipping due to the falling off of coarse precipitates. From this viewpoint, the content of Si 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.

[Aluminum (Al)]
Al is added in an amount of 0.50% or more in order to combine with Ni to precipitate Ni ₃ Al or NiAl and improve the hardness of the copper alloy. If the content of Al is low, the amount of combination with Ni decreases, and sufficient improvement in hardness cannot be obtained. From this viewpoint, Al is preferably set to 1.00% or more. On the other hand, addition of a large amount of Al generates an excessive amount of Ni ₃ Al compound. Although this compound increases the hardness of the copper alloy, it reduces the toughness of the copper alloy, and may cause wire breakage during wire drawing or the like. From this viewpoint, the content of Al 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.

[Tin (Sn)]
Sn is added in an amount of more than 2.00% in order to combine with Ni to precipitate Ni ₃ Sn ₂ or Ni ₃ Sn, improve the hardness of the copper alloy, and suppress the increase in the diameter of the precipitate (promote fineness). If the Sn content is low, the amount of combination with Ni decreases, and the effect of improving the hardness is not sufficient, and precipitates with a relatively large diameter tend to precipitate. On the other hand, if a large amount of Sn is added, the excessive Sn may reduce the strength of the grain boundary, which may cause 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.

[Boron (B)]
B is added in an amount of more than 0%, preferably _0.003 % or more, in order to improve corrosion resistance and to disperse precipitates such as _Ni2Si , _Ni3Al , and _Ni3Sn2 more finely and further improve the hardness of the copper alloy. On the other hand, the addition of a large amount of B may not only reduce the toughness and workability of the copper alloy, but may also cause holes (so-called "cavities") in various places in the material. From this perspective, the content of B is set to less than 0.010%, preferably 0.009% or less.

[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 the plastic workability and reduce the electrical conductivity, and S and Fe also form harmful coarse inclusions, so that the total content of these elements is preferably 0.20% or less. In addition, the content of each impurity is preferably about 0.10% or less.

[Relationship ratios of Si, Al, Sn and B]
In order to improve the electrical conductivity and workability of the copper alloy, it is sufficient to increase the Cu content. On the other hand, in order to increase the hardness of the copper alloy, it is necessary to precipitate more Ni ₂ Si, Ni ₃ Al, NiAl, Ni ₃ Sn ₂ and Ni ₃ Sn in the copper alloy. The inventors have focused on the relative ratio of Si, Al and Sn to B (hereinafter, simply referred to as "relative ratio") in copper alloys having a long shape such as wire rods and rods, and have tried experiments with various different relative ratios. As a result, it has been found that, on the premise of the above-mentioned range of the contents of Si, Al and Sn, when the relative ratio is specified within a certain range, it is possible to simultaneously achieve the improvement of the hardness of the copper alloy due to the precipitation of precipitates and the suppression of 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 relational ratio (1.7Si+1.2Al+Sn)/3.9B is less than 120, the content of B becomes excessive relative to the contents of Si, Al, and Sn, which leads to a decrease in the toughness of the copper alloy, and wire breakage and breakage occur during the product processing process, resulting in a decrease in yield. On the other hand, when the value of the relational ratio (1.7Si+1.2Al+Sn)/3.9B exceeds 300, the content of B becomes insufficient relative to the contents of Si, Al, and Sn, and this time, the precipitates of Ni ₂ Si, Ni ₃ Al, NiAl, Ni ₃ Sn ₂ , and Ni ₃ Sn cannot be sufficiently dispersed. And, the non-dispersion of precipitates in a copper alloy having a long shape such as a wire rod or a bar rod causes the occurrence of defects due to the detachment of precipitates due to the continuous impact force received during the product processing process of the copper alloy or after the product is manufactured. From the above viewpoints, the copper alloy of this embodiment specifies the relational 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.

[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 which a large impact force is repeatedly applied, such as in the case of pins for contact probes. From this perspective, the Vickers hardness of the copper alloy is preferably 380 HV or more, more preferably 400 HV or more.

[Electrical conductivity (%IACS)]
The copper alloy of this embodiment has a conductivity of 8% IACS or more. As a result, the copper alloy of this embodiment can be used in various products that require electrical conductivity, such as contact probe pins for semiconductor inspection. In addition, since the copper alloy of the present embodiment is preferably used for the above-mentioned applications, it has an equivalent wire diameter of 0.5 to 5.0 mm, and its electrical properties are as follows: A conductivity of 8% IACS or more is sufficient, but preferably 10% IACS or more. The conductivity of copper alloys is determined according to JIS-C3002 "Test for Electrical Copper Wire and Aluminum Wire." The measurement is performed in a thermostatic chamber at 20°C using a four-terminal method (sample length: 100 mm) in accordance with the "Method of Measurement of Electrical and Electronic Properties of JIS K 1111-1, 1999-2, and 2001-3.

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

More specific examples of the present invention are described below, but the present invention is not limited to these examples.

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

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

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 continuously brought into contact with and out of contact with the inspection surface of a silicon wafer 10,000 times. The condition of the pins after the test (presence or absence of defects, etc.) was then evaluated.

Table 1 shows the chemical composition and evaluation results of the copper alloy of the invention material and the comparative material.

[Invention materials]
As is clear from Table 1, the inventive materials 1 to 30 have a Vickers hardness of 350 HV or more and a conductivity of 8% IACS or more, and it was confirmed that they have excellent hardness and conductivity. In addition, for any of the inventive materials, no breakage or breakage occurred during the production and processing of long objects such as wires, and no defects such as scratches were found on the surface or inside of the wires after processing. Furthermore, the pins of the contact probes manufactured using the inventive materials did not experience any defects such as cracks, defects, or thermal deformation during the continuous conductivity test.

[Comparative material 1]
Comparative material 1 is an example that does not satisfy the content of the chemical components specified by the present invention with respect to Ni, Si, Sn, and B, and does not satisfy the related ratio. Specifically, comparative material 1 is an example in which less Ni, more Si, less Sn, and more B are added, and the value of the related ratio is also small. It can be seen that such comparative material 1 has a satisfactory electrical conductivity, but does not obtain sufficient Vickers hardness. In addition, since the value of the related ratio is small, disconnection occurred due to the influence of precipitates during the processing into wire. In addition, after the continuous electrical conductivity test, a defect was confirmed at the tip of the pin for the contact probe manufactured using comparative material 1. Figure 2 shows an enlarged photograph of the tip of the pin of comparative material 1 after the continuous electrical conductivity test. It was confirmed that the defect at the tip of the pin occurred due to the presence of precipitates with a particle size of about 10 μm to about 17 μm.

[Comparative material 2]
Comparative material 2 satisfies the numerical range of the relation ratio specified by the present invention, but the content of Si, Sn, and B, which is the premise of the ratio, is outside the range specified by the present invention. Specifically, comparative material 2 is an example in which less Si, more Sn, and more B are added. Comparative material 2 has a slightly higher Vickers hardness than comparative material 1, but does not reach 350 HV, and it was confirmed that the electrical conductivity is also low. In addition, comparative material 2 did not break or break during the production process, but the pin of the contact probe using comparative material 2 had a crack as shown in FIG. 3 near the tip of the pin (contact point with the silicon wafer) after the continuous electrical conductivity test.

[Comparative material 3]
Comparative material 3 is an example that does not satisfy the contents of chemical components specified by the present invention with respect to Si and B, and does not satisfy the relevant ratio. Specifically, comparative material 3 is an example in which Si is low, Sn is high, and B is high, and the value of the relevant ratio is small. It was confirmed that comparative material 3 has low electrical conductivity and Vickers hardness. It was also confirmed that comparative material 3 broke during and after wire drawing and after the continuous electrical conductivity test. When the cross section of comparative material 3 was observed in more detail, it was confirmed that several cavities a (micropores) with a width of about 10 to 350 μm were formed inside the cross section, as shown in FIG. 4. It was also confirmed in FIG. 5 that cavities a with a width of 10 to 50 μm were generated in various places on the surface of the material. It is presumed that the breakage of the material occurred from these cavities a.

[Comparative material 4]
Comparative material 4 is an example that does not meet the contents of chemical components specified by the present invention with respect to Si, Sn, and B, and does not meet the relative ratios either. Specifically, comparative material 4 is an example in which a small amount of Si, a large amount of Sn, and a large amount of B are added, and the relative ratios cannot be calculated. In comparative material 4, breakage occurred during the wire drawing process. In addition, 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.

[Comparative material 5]
Comparative material 5 satisfies the numerical range of the relation ratio specified by the present invention, but the content of Al and Sn, which is the premise of the relation ratio, is outside the range specified by the present invention. Specifically, comparative material 5 is an example in which the content of Al is small and the content of Sn is large. Comparative material 5 has sufficient electrical conductivity, but does not have sufficient Vickers hardness. Furthermore, although comparative material 5 did not suffer from disconnection or breakage during the production process, a continuous electrical conductivity test confirmed that the contact probe pin was thermally deformed, making continuous use difficult.

[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 electrical conductivity and Vickers hardness, but broke due to the presence of precipitates during processing into wire, similar to comparative material 1. In addition, a contact probe pin was made from comparative material 5, and a continuous electrical conductivity test was performed, confirming that the tip was chipped as shown in Figure 2, similar to comparative material 1.

As is clear from the above discussion, it has been confirmed that in order to solve the problems of the present invention, it is important to satisfy both the content and the relative ratio of the chemical components of the present invention.

1 Contact Probe 2 Pins

Claims (4)

A copper alloy in a long form having an equivalent wire diameter of 0.5 to 5.0 mm,
In mass%, the alloy 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%, and the balance is Cu and inevitable impurities;
Vickers hardness is 350 HV or more,
The electrical conductivity is 8% IACS or more;
The relative ratios of Si, Al, Sn and B satisfy 120≦(1.7Si+1.2Al+Sn)/3.9B≦300;
Copper alloy. The copper alloy according to claim 1, containing, by mass%, 11.00%≦Ni≦15.00%, 0.40%≦Si≦0.90%, and 1.00%≦Al≦2.00%. The copper alloy according to claim 1 or 2, wherein the relationship ratio satisfies 160≦(1.7Si+1.2Al+Sn)/3.9B≦250. A pin for a contact probe made of the copper alloy described in claim 1 or 2.