Cu-ag alloy wire manufacturing method

Abstract

Provided is a Cu-Ag alloy wire manufacturing method capable of increasing Vickers hardness. The Cu-Ag alloy wire manufacturing method comprises: a step for preparing a drawn Cu-Ag alloy wire containing 0.1-30 mass % of Ag with the remainder comprising Cu and unavoidable impurities; and a heat treatment step for heating the Cu-Ag alloy wire at 125-275°C to increase the Vickers hardness of the Cu-Ag alloy wire.

Description

Manufacturing method of Cu-Ag alloy wire

[0001] The present invention relates to a method for producing a Cu—Ag alloy wire.

[0002] When testing the electrical characteristics of a test object such as a semiconductor integrated circuit, a probe card with an array of probe pins is sometimes used. In this case, the tips of the probe pins are brought into contact with the test target location of the test object to test the electrical characteristics.

[0003] Since probe pins are used by repeatedly contacting the test target area thousands or tens of thousands of times, the probe pins must have sufficient "hardness." Of course, to ensure reliable input and output of test signals through the probe pins, the probe pins must also have low "resistivity." To meet these requirements, Cu alloys containing Ag are known as metals used for probe pins. It is preferable that such alloys be processed appropriately to have the desired properties.

[0004] For example, Patent Document 1 discloses a technique for appropriately processing a Cu alloy containing Ag to obtain desired properties.

[0005] International Publication No. 2014 / 007259

[0006] A main object of the present invention is to provide a method for producing a Cu--Ag alloy wire capable of increasing the Vickers hardness.

[0007] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a method for manufacturing a Cu—Ag alloy wire, the method comprising: a step of preparing a drawn Cu—Ag alloy wire containing 0.1 to 30 mass% of Ag, with the remainder consisting of Cu and unavoidable impurities; and a heat treatment step of heating the Cu—Ag alloy wire at 125 to 250°C to increase the Vickers hardness of the Cu—Ag alloy wire.

[0008] According to the present invention, a method for producing a Cu—Ag alloy wire capable of increasing Vickers hardness can be provided.

[0009] Fig. 1 is a flowchart showing a method for manufacturing a Cu—Ag alloy wire. Fig. 2 is a flowchart showing an example of a process for preparing a drawn Cu—Ag alloy wire. Fig. 3 is a graph showing the relationship between temperature and time in a heat treatment process in an example.

[0010] A manufacturing method according to a preferred embodiment of the present invention will be described below. In this specification, when a numerical range is indicated by "to", the lower limit and upper limit are included in the numerical range.

[0011] 1 is a flowchart showing an example of a method for manufacturing a Cu—Ag alloy wire according to an embodiment of the present invention. As shown in FIG. 1, the method for manufacturing a Cu—Ag alloy wire includes a step S1 of preparing a drawn Cu—Ag alloy wire and a heat treatment step S2.

[0012] In the step S1 of preparing a drawn Cu—Ag alloy wire, a pre-drawn Cu—Ag alloy wire may be purchased, or a Cu—Ag alloy wire may be manufactured and drawn. For example, as shown in Fig. 2, in the step S1 of preparing a drawn Cu—Ag alloy wire, the drawn Cu—Ag alloy wire may be prepared by performing a melting / casting step s11, a heat treatment step s12, a wiredrawing step s13, a heat treatment step s14, a wiredrawing step s15, and an optional twisting step s16 in this order. By performing a heat treatment step S2 on the prepared drawn Cu—Ag alloy wire at a predetermined temperature and for a predetermined time, a Cu—Ag alloy wire with increased Vickers hardness can be obtained.

[0013] Each step shown in FIGS. 1 and 2 will be described below in order.

[0014] [Step S1 of Preparing a Drawn Cu—Ag Alloy Wire] First, in step S1, a drawn Cu—Ag alloy wire is prepared. As described above, in step S1, a pre-drawn Cu—Ag alloy wire may be purchased, or a Cu—Ag alloy wire may be manufactured and drawn to prepare the wire.

[0015] The Cu—Ag alloy wire preferably contains 0.1 to 30 mass% of Ag, with the remainder being Cu and unavoidable impurities. The Ag content may be within this range, for example, 5 to 30 mass%. The diameter of the drawn Cu—Ag alloy wire is not particularly limited.

[0016] In the following description, an example will be described in which a drawn Cu—Ag alloy wire is prepared by carrying out a melting / casting step s11, a heat treatment step s12, a wiredrawing step s13, a heat treatment step s14, a wiredrawing step s15, and an optional twisting step s16 in this order, as shown in Fig. 2. Note that the procedure for producing a drawn Cu—Ag alloy wire is not limited to the following example.

[0017] (Melting and Casting Step s11) In the melting and casting step s11, the raw materials are melted at 1000 to 1400°C, and the melt (molten metal) is poured into a mold to cast a rod A. The raw materials may be any material that, after melting, becomes a composition (molten metal) containing 0.1 to 30 mass% Ag, with the remainder consisting of Cu and unavoidable impurities. The raw materials may be simple substances in which Ag and Cu exist separately before melting, or may be a compound in which Ag and Cu are integrated. The melt poured into the mold is cooled to room temperature within 0.5 to 60 minutes. This results in a rod A having a certain diameter, in which a Cu-Ag eutectic phase is formed in a network pattern in a Cu base.

[0018] (Heat Treatment Step s12) In the heat treatment step s12, the bar A is heated in a vacuum or inert gas atmosphere at 300 to 700°C for 1 to 60 hours to precipitate Ag solid-solubilized in the Cu base as an Ag precipitate phase. The heating temperature is preferably 400 to 500°C, and the heating time is preferably 5 to 10 hours. N is used as the inert gas. ２ Alternatively, Ar can be used. The heat treatment here induces the precipitation of Ag precipitates, which mainly contributes to improving the hardness and reducing the resistivity of the Cu—Ag alloy wire.

[0019] (Wiredrawing step s13) In the wiredrawing step s13, the bar A is drawn with a cold working ratio of 2.3 or more to produce a wire B1. The "cold working ratio" here is a value expressed by the following formula: Cold working ratio = ln((cross-sectional area of ​​bar A) / (cross-sectional area of ​​wire B1)).

[0020] (Heat Treatment Step s14) In the heat treatment step s14, the wire B1 is annealed by heating it at 300 to 700°C for 1 to 60 hours in a vacuum or inert gas atmosphere. The heating temperature is preferably 300 to 500°C, more preferably 300 to 400°C, and the heating time is preferably 5 to 50 hours. As the inert gas, N ２ Alternatively, Ar can be used.

[0021] (Wiredrawing step s15) In the wiredrawing step s15, the wire B1 is drawn with a cold working ratio of more than 7.2 to produce a wire B2. The "cold working ratio" here is a value expressed by the following formula: Cold working ratio = ln((cross-sectional area of ​​wire B1) / (cross-sectional area of ​​wire B2)). Note that the heat treatment step s14 and the wiredrawing step s15 may be repeated multiple times.

[0022] (Twisting Process S16) In the twisting process S16, the wire B2 is twisted. The twisting process S16 is an optional process, and in this embodiment, the process S1 of preparing a drawn Cu—Ag alloy wire may or may not include the twisting process S16. In the twisting process S16, the wire B2 is twisted by rotating a master bobbin (supply bobbin) around which the wire B2 is wound, and winding the wire B2 fed from the supply bobbin onto a recovery bobbin. The twisting process of the wire B2 mainly contributes to adjusting (improving) the final hardness while maintaining the electrical conductivity of the Cu—Ag alloy wire. In particular, the twisting process S16 is performed without applying heat treatment, which can suppress a decrease in Vickers hardness while ensuring the linearity required for the probe pin.

[0023] A drawn Cu—Ag alloy wire can be prepared by the processes from the melting and casting step s11 to the wire drawing step s15, or by these processes plus the twisting step s16.

[0024] [Heat Treatment Step S2] In step S2, the drawn Cu—Ag alloy wire prepared in step S1 is heated at 125 to 250° C. so as to increase the Vickers hardness. The heating temperature and time may be appropriately set so as to increase the Vickers hardness of the Cu—Ag alloy wire. The heat treatment step S2 is preferably carried out in a vacuum or in an inert gas atmosphere. The inert gas is N ２ Alternatively, Ar can be used.

[0025] The reason why the Vickers hardness increases in the heat treatment step S2 is presumed to be as follows. Note that this reason is merely presumed, and the present invention is not limited to this. That is, it is presumed that the heat treatment step S2 increases hardness due to extremely fine precipitates, increases hardness due to the interaction between dislocations and solute atoms, and increases hardness because mobile dislocations introduced into the grains of fine crystal grains are reduced by the relatively low-temperature heat treatment and become deformation resistance.

[0026] The heating temperature is preferably 125°C or higher, and more preferably 150°C or higher. The heating temperature is preferably 250°C or lower. If the heating temperature is lower than 125°C, the Vickers hardness of the Cu—Ag alloy wire may not be increased sufficiently even if the heating time is extended. On the other hand, if the heating temperature exceeds 250 to 300°C, the Vickers hardness of the Cu—Ag alloy wire may be reduced due to recovery and recrystallization. The heating temperature in the heat treatment step S2 is usually lower than those in the heat treatment steps s12 and s14. That is, a low-temperature heat treatment is performed in the heat treatment step S2.

[0027] The heating time is preferably 0.05 hours (3 minutes) or more, more preferably 0.1 hours (6 minutes) or more. The heating time is preferably 50 hours or less, more preferably 24 hours or less. If the heating time is less than 0.05 hours, the Vickers hardness of the Cu—Ag alloy wire may not be sufficiently increased even if the heating temperature is increased. On the other hand, if the heating time exceeds 50 hours, the Vickers hardness of the Cu—Ag alloy wire may be reduced due to recovery and recrystallization. Furthermore, if the heating time exceeds 50 hours, the tensile strength or elongation of the Cu—Ag alloy wire may be reduced.

[0028] When the heating temperature is high and the heating time is long, the Vickers hardness of the Cu—Ag alloy wire is likely to decrease. On the other hand, when the heating temperature is high but the heating time is short, or when the heating time is long but the heating temperature is low, such a problem is unlikely to occur. Therefore, it is preferable that the heating temperature and the heating time are adjusted to each other from the viewpoint of increasing the Vickers hardness of the Cu—Ag alloy wire.

[0029] For example, in the heat treatment step S2, it is preferable to heat the Cu—Ag alloy wire at a heating temperature of X° C. for a heating time of Y hours so as to satisfy the following formulas 1 and 2: (Formula 1) X≧125 (Formula 2) 0.05≦Y≦(−0.3925X+98.875)

[0030] Alternatively, in the heat treatment step S2, it is more preferable to heat the Cu—Ag alloy wire so as to satisfy the following formulas 3 and 4: (Formula 3) X≧150 (Formula 4) 0.1≦Y≦(−0.235X+59.25)

[0031] Alternatively, in the heat treatment step S2, it is particularly preferable to heat the Cu—Ag alloy wire so as to satisfy the following formulas 5 and 6: (Formula 5) X≧150 (Formula 6) (−0.3925X+62)≦Y≦(−0.3925X+83)

[0032] In the manufacturing method of the Cu—Ag alloy wire of this embodiment, it is preferable not to perform the wiredrawing step and the wrapping step after the heat treatment step S2. That is, it is preferable that all the wiredrawing steps and the wrapping step are performed before the heat treatment step S2. Even if the wiredrawing step is performed after the heat treatment step S2, it is difficult to properly wiredraw the Cu—Ag alloy wire after the Vickers hardness has increased.

[0033] [Obtained Cu—Ag Alloy Wire] The obtained Cu—Ag alloy wire has an increased Vickers hardness compared to the Cu—Ag alloy wire before the heat treatment step S2. The Vickers hardness is preferably increased by 10 HV or more, more preferably by more than 10 HV, and more preferably by 15 HV or more. The Vickers hardness of the obtained Cu—Ag alloy wire is preferably 300 or more.

[0034] The resistivity and conductivity of the obtained Cu—Ag alloy wire are preferably increased compared to those of the Cu—Ag alloy wire before the heat treatment step S2. The tensile strength of the obtained Cu—Ag alloy wire is preferably increased compared to those of the Cu—Ag alloy wire before the heat treatment step S2. The 0.2% proof stress of the obtained Cu—Ag alloy wire is preferably increased compared to those of the Cu—Ag alloy wire before the heat treatment step S2. The elongation of the obtained Cu—Ag alloy wire may decrease compared to those of the Cu—Ag alloy wire before the heat treatment step S2, but is preferably maintained at 1.8% or more, more preferably 1.9% or more, and even more preferably 2.0% or more.

[0035] (Effect) According to the manufacturing method of the Cu—Ag alloy wire of this embodiment, the Vickers hardness of the Cu—Ag alloy wire is increased by heat treatment. Conventionally, in manufacturing methods of Cu—Ag alloy wire, it is known that the conditions of the intermediate heat treatment are adjusted and the hardness is finally increased by work hardening such as wire drawing. However, increasing the hardness by wire drawing makes the Cu—Ag alloy wire thinner, and there is a limit to obtaining a large-diameter, hard Cu—Ag alloy wire. According to the manufacturing method of the Cu—Ag alloy wire of this embodiment, the Vickers hardness can be increased in the heat treatment step S2 without wire drawing. Therefore, it is possible to obtain a Cu—Ag alloy wire having a diameter of 50 μm or more (preferably 60 μm or more) and increased hardness.

[0036] The drawn Cu—Ag alloy wires were prepared as follows, and then subjected to heat treatment to obtain the Cu—Ag alloy wires of the examples and comparative examples. First, step S1 of preparing the drawn Cu—Ag alloy wire will be described, and then step S2 of performing heat treatment on the prepared alloy wire will be described.

[0037] (1) Step S1 of preparing a Cu—Ag alloy wire In step S1 of preparing a drawn Cu—Ag alloy wire, two types of Cu—Ag alloy wires B2-1 and B2-2, which differ from each other in Ag content and cold working degree, were prepared as follows. Each will be described below.

[0038] (i) Cu—Ag alloy wire B2-1 The raw material was heated to 1000 to 1400°C to melt it, and a melt (molten metal) consisting of 24 mass% Ag and the remainder Cu and unavoidable impurities was prepared. The melt (molten metal) was poured into a mold and cooled to room temperature within 10 minutes, and a rod A1-1 with a diameter of 17.5 mm was cast. The rod A1-1 was then heated to 1000 to 1400°C to melt it, and a melt (molten metal) consisting of 24 mass% Ag and the remainder Cu and unavoidable impurities was prepared. The melt (molten metal) was poured into a mold and cooled to room temperature within 10 minutes, and a rod A1-1 with a diameter of 17.5 mm was cast. ２ The bar A1-1 was then drawn from a diameter of 17.5 mm to a diameter of 3.4 mm to produce a wire B1-1 with a cold working ratio of 3.3. ２ The wire rod B1-1 was heated in a gas atmosphere at 350° C. for 30 hours. Thereafter, the wire rod B1-1 was drawn from a diameter of 3.4 mm to a diameter of 0.06 mm to produce a wire rod B2-1 with a cold working ratio of 8.1.

[0039] (ii) Cu—Ag alloy wire B2-2 The raw material was heated to 1000 to 1400°C to melt it, and a melt (molten metal) consisting of 10 mass% Ag and the remainder Cu and unavoidable impurities was prepared. The melt (molten metal) was poured into a mold and cooled to room temperature within 10 minutes, and a rod A1-2 with a diameter of 11.5 mm was cast. The rod A1-2 was then heated to 1000 to 1400°C to melt it, and a melt (molten metal) consisting of 10 mass% Ag and the remainder Cu and unavoidable impurities was prepared. The melt (molten metal) was poured into a mold and cooled to room temperature within 10 minutes, and a rod A1-2 with a diameter of 11.5 mm was cast. ２ The bar A1-2 was then drawn from a diameter of 11.5 mm to a diameter of 2.2 mm to produce a wire B1-2 with a cold working ratio of 3.3. ２ The wire rod B1-2 was heated in a gas atmosphere at 350° C. for 30 hours. Thereafter, the wire rod B1-2 was drawn from a diameter of 2.2 mm to a diameter of 0.06 mm to prepare a wire rod B2-2 with a cold working ratio of 7.2.

[0040] (2) Heat Treatment Step S2 The drawn Cu—Ag alloy wire B2-1 prepared as described above was subjected to a heat treatment using N ２ The Cu—Ag alloy wires of Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-8 were obtained by heating in a gas atmosphere using a hot air circulating furnace at the temperatures and times shown in Table 1. Similarly, the drawn Cu—Ag alloy wire B2-2 prepared as described above was heated in a N ２ The wires were heated in a gas atmosphere at the temperatures and times shown in Table 1 to obtain Cu—Ag alloy wires of Examples 2-1 to 2-3 and Comparative Example 2-1.

[0041] (3) Measurement and Evaluation The obtained Cu—Ag alloy wires of the examples and comparative examples were measured and evaluated for Vickers hardness, resistivity, conductivity, tensile strength, 0.2% yield strength, and elongation as follows. The measurement results are shown in Table 1. The change in each measurement value before and after the heat treatment step S2 is also shown in Table 2. For reference, the measurement values ​​of Cu—Ag alloy wires B2-1 and B2-2 before the heat treatment step S2 are also shown in Table 1.

[0042] <Vickers hardness> Vickers hardness was measured according to JIS Z 2244-1 (2020). A Matsuzawa Vickers hardness measuring device (AMT-X7AFS) was used as the measuring device. The measurement conditions were as follows: Load: 25 gf Holding time: 15 seconds The measurement results are shown in Table 1.

[0043] <Specific Resistivity and Conductivity> Using the double bridge method, the electrical resistance of each of five samples was measured in a room controlled at 20°C (±2°C), and the average values ​​of the specific resistance (μΩ cm) and conductivity (% IACS) were calculated. The distance between the voltage terminals was 500 mm. The calculation results are shown in Table 1.

[0044] <Tensile Strength> Tensile strength was measured for five samples according to JIS Z 2241 (2022), and the average value (MPa) was calculated. The calculation results are shown in Table 1.

[0045] <0.2% Yield Strength> In accordance with JIS Z 2241 (2022), the 0.2% yield strength of each of five samples was measured by the offset method, and the average value (MPa) was calculated. The calculation results are shown in Table 1.

[0046] <Elongation> According to JIS Z 2241 (2022), the total elongation at break of five samples was measured and the average value (%) was calculated. The calculation results are shown in Table 1.

[0047]

[0048]

[0049] As can be seen from the results of the examples in Tables 1 and 2, it was found that the Vickers hardness can be increased by performing the heat treatment step S2 in which the Cu-Ag alloy wires B2-1 and B2-2 are heated at a relatively low temperature of 125 to 250°C.

[0050] Fig. 3 is a graph showing the relationship between temperature and time in the heat treatment step S2. Specifically, Fig. 3 is a graph in which the horizontal axis X represents temperature (°C) and the vertical axis Y represents time (h), with the heat treatment conditions of the Examples in Table 1 above plotted as black circles and the heat treatment conditions of the Comparative Examples plotted as crosses. Fig. 3 also shows the following (Equations i) to (Equations vi-ii), which serve as the basis for the above (Equations 1) to (Equations 6) showing the relationship between temperature X and time Y in the heat treatment step S2. (Formula i) X=125 (Formula ii-i) Y=0.05 (Formula ii-ii) Y=-0.3925X+98.875 (Formula iii) (Formula vi-ii) Y=-0.3925X+83

[0051] As shown in Figure 3, Examples 1-1 to 1-12 and Examples 2-1 to 2-3 are within the range enclosed by (Formula i) X = 125, (Formula ii-i) Y = 0.05, and (Formula ii-ii) Y = -0.3925X + 98.875. On the other hand, the Comparative Examples are outside this range. That is, from the viewpoint of increasing Vickers hardness, it is preferable that the heat treatment step S2 satisfy (Formula 1) X ≥ 125 and (Formula 2) 0.05 ≤ Y ≤ (-0.3925X + 98.875).

[0052] More specifically, Examples 1-1 to 1-12 and Examples 2-1 to 2-3 are present within the range surrounded by (formula iii) X = 150, (formula iv-i) Y = 0.1, and (formula iv-ii) Y = -0.3925X + 83. That is, it is preferable that the heat treatment step S2 satisfies (formula 3) X ≥ 150 and (formula 4) 0.1 ≤ Y ≤ (-0.235X + 59.25).

[0053] Furthermore, as can be seen from Tables 1 and 2, in Examples 1-3 to 1-5 and 1-6 to 1-8, the Vickers hardness increased by more than 10 HV, the tensile strength increased by 15 MPa or more, and the elongation decrease was within 0.5%. These Examples are within the range surrounded by (Formula v) X = 150, (Formula vi-i) Y = -0.3925X + 62, and (Formula vi-ii) Y = -0.3925X + 83. In other words, it is preferable that the heat treatment step S2 satisfy (Formula 5) X ≥ 150 and (Formula 6) (-0.3925X + 62) ≤ Y ≤ (-0.3925X + 83).

[0054] According to the present invention, the Vickers hardness of a Cu—Ag alloy wire can be increased. The Cu—Ag alloy wire according to the present invention can be used for various purposes, such as contact probes and lead wires for electrical characteristic testing devices.

[0055] S1: Step of preparing drawn Cu-Ag alloy wire S2: Heat treatment step s11: Melting and casting step s12: Heat treatment step s13: Wire drawing step s14: Heat treatment step s15: Wire drawing step s16: Twisting step

Claims

1. A method for manufacturing a Cu-Ag alloy wire, comprising: a step of preparing a drawn Cu-Ag alloy wire containing 0.1-30 mass% Ag with the remainder being Cu and unavoidable impurities; and a heat treatment step of heating the Cu-Ag alloy wire at 125-250°C to increase the Vickers hardness of the Cu-Ag alloy wire.

2. The method for producing a Cu-Ag alloy wire according to claim 1, characterized in that in the heat treatment step, the Cu-Ag alloy wire is heated at a heating temperature of X°C for a heating time of Y hours so as to satisfy the following formulas 1 and 2: (Formula 1) X≧125 (Formula 2) 0.05≦Y≦(-0.3925X+98.875) 3. The method for producing a Cu-Ag alloy wire according to claim 2, wherein in the heat treatment step, the Cu-Ag alloy wire is heated so as to satisfy the following formulas 3 and 4. (Formula 3) X≧150 (Formula 4) 0.1≦Y≦(-0.235X+59.25) 4. A method for producing a Cu-Ag alloy wire according to claim 2, characterized in that in the heat treatment step, the Cu-Ag alloy wire is heated so as to satisfy the following formulas 5 and 6. (Formula 5) X≧150 (Formula 6) (-0.3925X+62)≦Y≦(-0.3925X+83) 5. A method for producing a Cu-Ag alloy wire according to any one of claims 1 to 4, characterized in that in the heat treatment step, the Vickers hardness of the Cu-Ag alloy wire is increased by 10 HV or more.

6. A method for producing a Cu-Ag alloy wire according to any one of claims 1 to 4, characterized in that a wire drawing step is not carried out after the heat treatment step.

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