Probe pin, thin wire for thermocouple, thin wire for electron tube heater, and manufacturing method thereof

Abstract

To provide a tungsten wire for improving variations in wire diameter.SOLUTION: According to an embodiment, a tungsten wire includes a tungsten alloy containing rhenium. The tungsten wire includes a protrusion peak density (Spd) of 7000 or more and 11000 or less as a surface roughness parameter.SELECTED DRAWING: Figure 6a

Description

[Technical Field]

[0001] The embodiments described below relate to a tungsten wire, a tungsten wire processing method using the same, an electrolytic wire, a probe pin, a thin wire for a thermocouple, a thin wire for an electron tube heater, and methods for manufacturing these. [Background technology]

[0002] A device called a probe card is used to test the electrical characteristics of an IC chip that forms a semiconductor device. Figure 1 shows a schematic diagram of an example of a vertical probe card 10. Probe pins 12 are connected to lead wires 11. After the test section 13 rises and the tip of the probe pin 12 makes contact, the test section 13 rises further by several tens to several hundred microns to ensure complete contact, and the test section 13 and the tip of the probe pin 12 are pressed together (this is called overdrive). This causes the probe pin 12 to bend (elastic deformation).

[0003] The shape of the probe pin 12 is shown in FIG. 2. The probe pin 12 may be, for example, a type (a) consisting of a straight portion 120 and a tapered portion 121, or a type (b) in which the tip of the tapered portion 121 is bent to form a bent portion 121a. The straight portion 120 may be treated with an insulating coating or the like. (a) is used in a vertical probe card, while (b) is used in a cantilever probe card. The standard dimensions of the pin are a diameter of the straight portion of approximately 0.05 to 0.20 mm and a total length of approximately 20 to 100 mm. Common materials conventionally used for probe pins include tungsten (W), rhenium-tungsten alloy (ReW), palladium (Pd) alloy, and beryllium copper (Cu-Be), and are selected depending on the type of electrode pad. There are two main types of electrode pads: aluminum pads and gold pads. For aluminum pads, probe pins made of W or ReW, which have high hardness and excellent electrical resistance and wear resistance, are mainly used because it is necessary to break through the insulating coating formed by oxidation on the surface of the electrode pad.

[0004] As semiconductor integration density and miniaturization technology advances, probe cards are also required to have narrower pin pitches and smaller pin diameters. Currently, ReW pins with diameters of 0.02mm to 0.04mm are being used. By reducing the probe pin diameter and increasing the number of pins per unit area, it is possible to test highly integrated LSIs. As the pin diameter decreases, the pressing force of each probe pin due to elastic deformation during overdrive, for example, becomes more susceptible to dimensional variations. Furthermore, increasing the number of probe pins requires a smaller spacing between the probe pins, which in turn significantly affects the number of pins. As such, the demand for pin dimensional accuracy is also increasing.

[0005] Probe pins are made by cutting small-diameter tungsten wire (thin wire) to a fixed length, then mechanically or chemically polishing the surface to determine the diameter. If the diameter of the thin wire varies, a larger cutting allowance is required. Alternatively, there is a risk that the cutting allowance may be insufficient, resulting in portions that cannot be used as a product. The smaller the wire diameter, the greater the impact on yield loss. The processing of the thin wire material begins with the sintered compact undergoing primary processing such as rolling and wire drawing (wire drawing) to produce wire in a diameter range (0.3–1.0 mm) that can be divided into various applications and product types. The appropriate amount of wire is then subjected to additional processes such as wire drawing and heat treatment to produce the desired tungsten wire.

[0006] Methods for suppressing variations in wire diameter during the wire drawing process include managing the lubricant and strictly controlling the wire drawing conditions. For example, the lubricant applied to the surface of the W wire contains graphite (C) powder and a thickener, and has a specific gravity of 1.0 to 1.1 g / cm. 3 The change in specific gravity during processing is 0.05 g / cm 3The following is a list of the tungsten wires that are produced by the wiredrawing process: a tungsten wire temperature of 500°C to 1300°C, a wiredrawing die temperature of 300°C to 650°C, a wiredrawing speed of 10 m / min to 70 m / min, and an area reduction rate of 5% to 15% in the final wiredrawing process (see Patent Document 1). Furthermore, one method for preventing seizure during wiredrawing, which causes variations in wire diameter, is to appropriately roughen the surface to improve the lubricity of the lubricant. For example, there is a stainless steel wire that is produced by wiredrawing to correct the wire into a perfect circle, followed by a skinning process to remove surface defects, and then adjusting the surface roughness to 0.8 to 2.5 μm in arithmetic mean roughness (Ra) defined by JIS B0601 using a shot blasting device (see Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent No. 5578852 [Patent Document 2] Japanese Patent Publication No. 7-233447 Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 1 lists the following causes of wire diameter variation after wiredrawing: a decrease in lubricity due to excessive heating of the lubricant in each wiredrawing process, a change in deformation resistance due to overheating of the wire, and a decrease in workability due to changes in the supply of lubricant (C content). It states that a change in the supply of carbon content changes lubricity, and that lubricity is extremely important for suppressing wire diameter variation. The lubricant is a liquid that is applied (adhered) to the wire surface, heated, and then subjected to the wiredrawing process. If the lubricant is not uniformly adhered to the wire surface, lubricity may fluctuate during wiredrawing, resulting in wire diameter variation, even when the above conditions are met.

[0009] In contrast, Patent Document 2 adjusts Ra to improve lubricant adhesion. Here, Ra is a parameter of wire roughness, and measurement is performed on a cross-sectional curve determined by a cross-section perpendicular to the material surface, as shown in Figure 3, for example. Ra is calculated using the formula shown in Figure 4. Therefore, evaluation using Ra requires that the surface roughness be uniform across the entire surface, including the circumferential and axial directions. In Patent Document 2, the surface is cleaned and then mechanically processed by shot blasting, resulting in uniform surface roughness throughout the entire length. In contrast, W wire is much harder than stainless steel wire and is susceptible to surface adhesion of impurities, which can cause embrittlement, so processing such as shot blasting is not used. Therefore, even tungsten wires with the same Ra may have different roughness shapes and therefore different lubricant adhesion.

[0010] The problem to be solved by the present invention is to provide a tungsten wire that improves the variation in wire diameter. [Means for solving the problem]

[0011] In order to solve the above problems, the tungsten wire according to the embodiment is a tungsten wire made of a tungsten alloy containing rhenium, and has a peak density (Spd) of 7000 or more and 11000 or less as a surface roughness parameter (see ISO 25178-2:2012 and JIS B0681). According to an embodiment, the method comprises the steps of: drawing a tungsten wire made of a tungsten alloy containing 1 wt% or more and 30 wt% or less of rhenium; and having a peak density (Spd) of 7000 or more and 11000 or less as a surface roughness parameter; cutting the tungsten wire; and polishing the surface of the tungsten wire. According to an embodiment, there is provided a method for manufacturing a thin wire for a thermocouple, the method comprising a step of wiredrawing a tungsten wire made of a tungsten alloy containing 1 wt% to 30 wt% of rhenium and 30 wtppm to 90 wtppm of potassium, and having a surface roughness parameter peak density (Spd) of 7000 to 11000. According to an embodiment, there is provided a method for manufacturing a thin wire for an electron tube heater, comprising a step of wiredrawing a tungsten wire made of a tungsten alloy containing 1 wt% to 30 wt% of rhenium and 30 wtppm to 90 wtppm of potassium, and having a surface roughness parameter peak density (Spd) of 7000 to 11000. According to the embodiment, there are provided a probe pin, a thin wire for a thermocouple, and a thin wire for an electron tube heater manufactured by the method according to the embodiment. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a vertical probe card. [Figure 2] FIG. 3 is a schematic diagram showing the shape of a probe pin. [Figure 3] Conceptual diagram of line roughness measurement. [Figure 4] FIG. 2 is a diagram schematically showing an example of arithmetic mean roughness Ra. [Figure 5a] Schematic diagram showing an example of a sample taken from a W wire for wire drawing. [Figure 5b] Schematic diagram showing a cross section perpendicular to the axis of a W wire for wire drawing. [Figure 6a] Schematic diagram explaining the measurement concept of Spd. [Figure 6b] Schematic diagram explaining the Spc measurement concept. [Figure 7] Schematic diagram explaining the Sdr measurement concept. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a tungsten wire for wire drawing according to an embodiment will be described with reference to the drawings. Hereinafter, the tungsten wire for wire drawing will also be referred to as a W wire for wire drawing. Note that the drawings are schematic, and for example, the dimensional ratios of each part are not limited to those shown in the drawings.

[0014] Figure 5a) shows an example of a W wire sample taken from a W wire for wire drawing. The sample length should be 100-150 mm, allowing for measurements at multiple locations. W wire for wire drawing has a mixture layer (oxide layer) on its surface. This mixture layer is removed, for example, using a caustic soda solution, and the main body is used as the measurement sample. The sampling location is arbitrary, but taking into account product yield and to check fluctuations over the entire length of the W wire, it is desirable to sample at two or more separate locations on a single W wire. The front and rear ends have unstable conditions, for example, when the wire drawing equipment is started and stopped, so these areas are not included in the sampling. The length of the unstable portion varies depending on the layout and size of the equipment.

[0015] Figure 5b) shows the XX cross section (cross section perpendicular to the axis) of Figure 5a). As shown in the figure, lines are drawn from the center to divide the circumference into five equal parts, and the intersections with the circumference are designated A1 to A5. The shape of the sample surface is measured at any of these five points. The measurement points are illustrative, and any part can be measured, but these points are best for measuring the entire circumference without bias. The number of data points is "5 x n" depending on the number of samples observed (n). Measurements are performed non-contact using a laser microscope. A 10x objective lens is used, with the field of view set so that the sample diameter does not extend beyond the field of view. The entire wire portion in the obtained measurement image is analyzed for surface roughness parameters in accordance with ISO 25178-2:2012.

[0016] Figure 6a illustrates the concept of measuring the peak density (Spd), a surface roughness parameter. The number of peaks per unit area (mm²) is calculated for the areas (B) classified as peaks in the feature image. The W wire of this embodiment has an Spd of 7,000 or more and 11,000 or less. It is more preferably 8,000 or more and 9,000 or less. The presence of surface irregularities ensures uniform adhesion of the lubricant (C) to the W wire surface during application of the lubricant and heating during wiredrawing. It also stabilizes the amount of C drawn into the die along with the W wire during wiredrawing. This stabilizes the drawing force during wiredrawing and enables uniform wiredrawing. If Spd is less than 7,000, the amount of C drawn into the die during wiredrawing becomes unstable, potentially resulting in variations in lubrication. If Spd exceeds 11,000, it becomes difficult for C to penetrate and adhere sufficiently to the W wire surface, especially the valleys, which can lead to partial peeling and variations in lubrication.The density of such peaks cannot be estimated from the line roughness parameters Ra and Rz (maximum height).

[0017] Figure 7 illustrates the concept of measuring the surface roughness parameter, the developed area ratio (Sdr), of the interface. The increase rate is calculated from the surface area F1 of the contour curve in the defined region and the area F0 when that surface is projected onto a plane. In the W wire of this embodiment, for example, Sdr is 0.16 or less. More preferably, it is 0.13 or less. The larger Sdr, the greater the difference in height between the peaks and valleys. If Sdr exceeds 0.16, the amount of carbon drawn into the die varies significantly between the peaks and valleys, potentially destabilizing lubrication. The wire roughness parameter Ra cannot account for such peak height differences. Furthermore, Rz is affected by scratches or dust on the measurement line. The lower limit is not particularly limited, but is, for example, 0.06 or more. A small Sdr may result in insufficient lubricant retention on the W wire surface when applying lubricant or drawing it into the wiredrawing die.

[0018] Figure 6b) illustrates the concept of measuring the arithmetic mean curvature (Spc) of the peaks of the surface roughness parameter. For the peaks (Bp) classified as peaks in Figure 6a), the radius of curvature of the peaks is determined and averaged as shown in Figure 6b). The larger the Spc, the smaller (sharper) the curvature of the protrusions, and the closer the cross section is to a so-called "serrated" shape. The smaller the Spc, the larger (blunter) the curvature, and the closer the cross section is to a so-called "trapezoid" shape. The W wire of the embodiment has an Spc of, for example, 300 or more and 500 or less. More preferably, it is 320 or more and 420 or less. The applied lubricant has an anchoring effect of the protrusion shape, which ensures uniform adhesion of the lubricant (C) to the W wire surface. It also stabilizes the amount of C drawn into the die along with the W wire during wiredrawing. This stabilizes the drawing force during wiredrawing, enabling uniform wiredrawing. If the Spc is less than 300, the top of the protrusion becomes flat and may become the starting point for peeling off of the lubricating layer when drawn into the die.If the Spc exceeds 500, the width of the peak on the tungsten surface becomes too small, reducing the strength of that part, which may cause deformation due to the force during wire drawing, resulting in overhanging (surface defects) on the W wire surface.

[0019] The formula for calculating the root-mean-square slope (Sdq) of the surface roughness parameter is given by Equation 1. This is an index indicating the root-mean-square slope of the slope at all points in the defined area. For example, the Sdq of a plane with a 45-degree slope is "1." The larger the value, the steeper the surface. In the W wire of the embodiment, for example, Sdq is 0.60 or less. More preferably, it is 0.55 or less. If Sdq is greater than 0.60, uneven adhesion of the lubricant is likely to occur when applying it. Depending on the number of peaks present, the lubricant may not penetrate sufficiently. Furthermore, steep irregularities may cause cracks during wire drawing depending on the conditions. The steepness of such peaks cannot be predicted from the roughness parameters Ra and Rz. The lower limit is not particularly limited, but it is, for example, 0.35 or more. If Sdq becomes small, the retention force of the lubricant on the surface of the W wire may become insufficient when the lubricant is applied or when the W wire is drawn into a wire-drawing die.

[0020]

number

[0021] The Re content contained in the W wire for wire drawing of the embodiment is preferably 1 wt% or more but less than 30 wt%, and more preferably 2 wt% or more but less than 28 wt%. The Re content is a value obtained by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). Re improves the elongation of W at high temperatures and enhances its workability. It also enhances strength through solid solution strengthening. However, if the content is less than 1 wt%, this effect is insufficient. For example, when used as a material for probe pins, the completed probe pins will deform more with increased use, resulting in contact failure and reduced semiconductor inspection accuracy. If the Re content is greater than approximately 28 wt%, the solid solubility limit with W will be exceeded, making it more likely that the σ phase will be unevenly distributed. This phase may become the starting point for fracture during wire drawing, significantly reducing processing yield. By setting the Re content to 1 wt% or more and 30 wt% or less, or 2 wt% or more and 28 wt% or less, for example, electrolysis wires for probe pins made from the material of this embodiment can be produced with good yield while ensuring the mechanical properties (strength and abrasion resistance).

[0022] The W wire for wire drawing according to the embodiment may contain 30 wtppm to 90 wtppm of K as a dopant. The K content is a value obtained by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). The inclusion of K improves tensile strength and creep strength at high temperatures due to the doping effect. If the K content is less than 30 wtppm, the doping effect becomes insufficient. If the K content exceeds 90 wtppm, workability may decrease, resulting in a significant decrease in yield. By containing 30 wtppm to 90 wtppm of K as a dopant, for example, thin wires for thermocouples and electron tube heaters made from the material of this embodiment can be produced with high yield while maintaining high-temperature properties (preventing breakage and deformation during high-temperature use).

[0023] Next, a method for manufacturing a W wire for wire drawing according to this embodiment will be described. The manufacturing method is not particularly limited, but the following method can be mentioned, for example.

[0024] W powder and Re powder are mixed so that the Re content is 1 wt% or more and less than 30 wt%. While there are no particular limitations on the mixing method, a method in which the powders are made into a slurry using water or an alcohol-based solution and mixed is particularly preferred, as this produces a powder with good dispersibility. The Re powder to be mixed has an average particle size of, for example, less than 8 μm. The W powder is either pure W powder excluding unavoidable impurities, or doped W powder containing a K amount that takes into account the yield of the wire rod. The W powder has an average particle size of, for example, less than 16 μm.

[0025] For example, when producing a W-Re mixed powder with an Re content of more than 18 wt%, a ReW alloy with an Re content of 18 wt% or less is first produced by powder metallurgy, melting, or other methods, and then finely pulverized using conventional methods. Another method is to add the necessary amount of Re to achieve the desired composition. Hereafter, tungsten wire containing Re may be referred to as a ReW wire.

[0026] Next, the mixed powder is placed in a predetermined mold and press-molded. The pressing pressure is preferably 150 MPa or higher. For ease of handling, the molded body may be pre-sintered at 1200-1400°C in a hydrogen furnace. The resulting molded body is sintered in a hydrogen atmosphere, an inert gas atmosphere such as argon, or a vacuum. The sintering temperature is preferably 2500°C or higher. At temperatures below 2500°C, the diffusion of Re and W atoms during sintering is insufficient. The upper limit of the sintering temperature is 3400°C (below the melting point of W, 3422°C). If the upper limit of the sintering temperature exceeds the melting point of W (3422°C), the molded body may not maintain its shape and may become defective. The relative density after sintering is preferably 90% or higher. By achieving a relative density of 90% or higher, it is possible to reduce the occurrence of cracks, chips, breaks, etc. during the subsequent rolling (SW) process.

[0027] Molding and sintering may be performed simultaneously by hot pressing in a hydrogen atmosphere, an inert gas atmosphere such as argon, or in a vacuum. The pressing pressure is preferably 100 MPa or more, and the heating temperature is preferably 1700°C to 2825°C. This hot pressing method can produce a dense sintered body even at a relatively low temperature.

[0028] The sintered body obtained in this sintering step is subjected to a first rolling (SW) process. The first SW process is preferably carried out at a heating temperature of 1300 to 1600°C. The reduction rate of the cross-sectional area (area reduction rate) in one heat treatment (one heat) is preferably 5 to 15%.

[0029] Instead of the first SW process, rolling (RM process) may be performed. The RM process is preferably performed at a heating temperature of 1200 to 1600°C. The area reduction rate per heat is preferably 40 to 75%. As the rolling mill, a two-way roller rolling mill, a four-way roller rolling mill, a die roll rolling mill, or the like can be used. The RM process can significantly improve manufacturing efficiency. The first SW process and the RM process may be combined.

[0030] The sintered body (ReW bar) that has undergone the first SW process, RM process, or a combination of these processes is subjected to the second SW process. The second SW process is preferably performed at a heating temperature of 1200 to 1500°C. The area reduction rate per heat is preferably about 5 to 20%.

[0031] The ReW bar that has undergone the second SW process is then subjected to a recrystallization treatment, which can be carried out using, for example, a high-frequency heating device in a hydrogen atmosphere, an inert gas atmosphere such as argon, or a vacuum at a treatment temperature in the range of 1800 to 2600°C.

[0032] The ReW bar that has completed the recrystallization treatment is subjected to a third SW process. The third SW process is preferably carried out at a heating temperature of 1200 to 1500°C. The area reduction rate per heat is preferably about 10 to 30%. The third SW process is carried out until the ReW bar has a diameter that can be drawn (preferably 2 to 4 mm).

[0033] After the third SW process, the ReW rod material is subjected to the first wiredrawing process, which involves repeatedly applying a lubricant to the surface to enable smooth wiredrawing, drying the lubricant, heating the rod to a workable temperature, and drawing the rod using a drawing die. This process is repeated until the wire reaches a diameter of 0.7 to 1.2 mm. A C-based lubricant with excellent heat resistance is preferable. The processing temperature is preferably 800°C to 1100°C. The workable temperature varies depending on the wire diameter, with the larger the diameter, the higher the temperature. If the processing temperature is lower than the workable temperature, cracks and wire breakage frequently occur. If the processing temperature is higher than the workable temperature, seizure between the ReW wire and the die occurs, the deformation resistance of the ReW wire decreases, and the drawing force causes diameter fluctuations (thinning) after wiredrawing. The area reduction ratio is preferably 15 to 35%. If it is less than 15%, differences in the internal and external structure and residual stresses occur during processing, which can lead to cracks. If it is more than 35%, the drawing force will be too large, causing the diameter after drawing to fluctuate significantly and resulting in breakage.The drawing speed is determined by the balance between the capacity of the heating device, the distance from the device to the die, and the area reduction rate.

[0034] The ReW wire drawn to a diameter of 0.7 to 1.2 mm is then polished. This process eliminates any irregularities on the surface that may have developed during the rolling process, as well as the influence of the mixture layer applied to the surface. Furthermore, the shape of the surface of the ReW wire itself is adjusted. Polishing is performed, for example, by electrochemical polishing (electrolytic polishing) in a sodium hydroxide solution. In this case, the current (polarity) used is a very important factor. Electrolysis using direct current (DC) has the effect of leveling out the surface irregularities. Furthermore, electrolysis using alternating current (AC) creates appropriate surface irregularities by changing the polarity with frequency. The surface condition can be adjusted by combining DC and AC electrolysis.

[0035] For example, DC electrolysis is first performed to cancel the effects of previous processing on the ReW wire surface, and then AC electrolysis is performed to adjust the surface to the desired condition. The concentration of the sodium hydroxide aqueous solution is, for example, 3 to 15 wt%. The processing speed is preferably 0.4 to 2.0 m / min. If it is slower than 0.4 m / min, the processing time will increase significantly. If it exceeds 2.0 m / min, the amount of electrolysis per unit time must be increased, making it difficult to adjust the surface condition. The electrolysis current is preferably in the range of 20 to 50 A.

[0036] The electrolysis may be performed multiple times. The combinations may be arbitrary. However, the more combinations there are, the larger the device capacity becomes, the more complicated the condition management becomes, and the more labor required. Therefore, it is preferable to perform the electrolysis less. Between electrolysis steps, a very thin oxide film layer may be formed by, for example, burner heating. This may facilitate the adjustment of the surface shape.

[0037] After polishing, the ReW wire is heated in an atmospheric furnace to form a dense, uniform oxide layer conforming to the surface shape. The heating temperature is preferably 700 to 1100°C. If the temperature is lower than 700°C, oxide formation is difficult. If the temperature is higher than 1100°C, variations in the oxide composition occur. The processing speed is preferably 5 to 20 m / min. If it is less than 5 m / min, the processing time increases significantly. If it exceeds 20 m / min, a large amount of heat is required to raise the temperature, which makes the oxide layer more likely to become non-uniform. Alternatively, the equipment must be very large.

[0038] After this, a second wiredrawing process is performed. The area reduction rate of the second wiredrawing process is preferably 15 to 35%. The heating temperature is preferably 1000°C or less. By the second wiredrawing process, a W wire for wiredrawing with a diameter of 0.3 to 1.0 mm is obtained. Furthermore, a proper amount of the W wire for wiredrawing is subjected to necessary processes such as wiredrawing and heat treatment under known conditions to obtain a W wire with the required characteristics (strength, hardness, etc.) at the specified wire diameter. This is then electrolytically polished to obtain an electrolytic wire.

[0039] (Example) Example 1: After the first wire drawing, DC electrolysis and AC electrolysis were repeated in sequence, and a ReW wire having a diameter of 1.0 mm was obtained by the second wire drawing. Example 2: After the first wire drawing, DC electrolysis was performed, and then burner heating was used to provide an oxide film that gave the surface a golden color, followed by AC electrolysis and a second wire drawing to produce a ReW wire with a diameter of 1.0 mm. Examples 3 to 5: After the first wiredrawing, DC electrolysis and AC electrolysis were performed once each, and a ReW wire having a diameter of 1.0 mm was obtained by a second wiredrawing. Comparative Examples 1 to 4: After the first wiredrawing, only DC electrolysis or only AC electrolysis was performed, and a ReW wire having a diameter of 1.0 mm was obtained by a second wiredrawing. Comparative Examples 5 to 6: No electrolysis was performed, and a ReW wire having a diameter of 1.0 mm was prepared.

[0040] Re and K were analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES). Table 1 shows the electrolytic treatment and Re and K analytical values ​​for each sample. The lower detection limit for K is 5 wtppm, and cases where the analytical value was below 5 wtppm without addition are indicated by "-".

[0041] For each example, 1 kg of ReW wire was used as the wire. Samples for measuring surface roughness were taken from both ends of the wire and boiled in a 25% caustic soda solution for 5 minutes to remove the oxide layer. A Keyence VK-X1100 laser microscope was used to observe the surface profile. After sampling, the wire was drawn to a diameter of 0.08 mm. The finished ReW wire was evaluated for diameter variation relative to the 0.08 mm diameter. The wire diameter was measured using a laser diameter measuring instrument (Mitutoyo Laser Scan Micrometer) with a measurement interval of 0.01 s, a minimum display of 0.01 μm, and a wire speed of 100 m / min. After measurement, the yields for wire diameter variations of 1.0% or less (range: 0.0008 mm) and 0.5% or less (range: 0.0004 mm) were calculated as a ratio of the length. The results are shown in Table 1. As can be seen from the table, the ReW wire according to the embodiment can significantly reduce variations in wire diameter, and can significantly improve the yield in probe pin processing.

[0042] [Table 1]

[0043] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. Modifications of these embodiments are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. The invention as originally claimed is as follows: [1] A tungsten wire made of a tungsten alloy containing rhenium, having a surface roughness parameter peak density (Spd) of 7000 or more and 11000 or less. [2] The tungsten wire according to [1], wherein the Spd is 8000 or more and 9000 or less. [3] A tungsten wire made of a tungsten alloy containing rhenium, wherein the developed area ratio (Sdr) of the interface, which is a surface roughness parameter, is 0.16 or less. [1] The tungsten wire according to any one of [1] and [2]. [4] A tungsten wire made of a tungsten alloy containing rhenium, wherein the surface roughness parameter, arithmetic mean peak curvature (Spc), is 300 or more and 500 or less. [1] The tungsten wire according to any one of [1] to [3]. [5] A tungsten wire made of a tungsten alloy containing rhenium, wherein the surface roughness parameter root mean square slope (Sdq) is 0.60 or less. [1] The tungsten wire according to any one of [1] to [4]. [6] The tungsten wire according to any one of [1] to [5], wherein the rhenium content is 1 wt% or more and less than 30 wt%. [7] The tungsten wire according to any one of [1] to [6], wherein the rhenium content is 2 wt% or more and 28 wt% or less. [8] The tungsten wire according to any one of [1] to [7], wherein the tungsten alloy has a potassium (K) content of 30 wtppm or more and 90 wtppm or less. [9] The tungsten wire according to any one of [1] to [8], wherein the diameter of the tungsten wire is 0.3 mm or more and 1.0 mm or less.

[10] A tungsten wire processing method, comprising drawing the tungsten wire according to any one of [1] to [9].

[11] An electrolytic wire using a tungsten wire that has been drawn using the tungsten wire processing method described in

[10] .

[12] The tungsten wire according to any one of [1] to [9], which is for wire drawing. [Explanation of symbols]

[0044] XX: cross section perpendicular to the drawing direction of the W wire sample for wire drawing (radial cross section), B: location classified as a mountain, B(n): number of mountain peaks, Bp: one of the peaks of the mountain, E: area where the mountain exists (projected area), r: radius of curvature of peak Bp, F0: projected area of ​​F1, F1: surface area of ​​the contour curve.

Claims

1. A step of wiredrawing a tungsten wire made of a tungsten alloy containing 1 wt% or more and 30 wt% or less of rhenium, and having a peak density (Spd) of 7,000 or more and 11,000 or less as a surface roughness parameter; cutting the tungsten wire; and polishing the surface of the tungsten wire.

2. A method for manufacturing a thin wire for a thermocouple, comprising a step of wiredrawing a tungsten wire made of a tungsten alloy containing 1 wt% or more and 30 wt% or less of rhenium and 30 wtppm or more and 90 wtppm or less of potassium, and having a peak density (Spd) of 7,000 or more and 11,000 or less as a surface roughness parameter.

3. A method for manufacturing a thin wire for an electron tube heater includes a step of wiredrawing a tungsten wire made of a tungsten alloy containing 1 wt% or more and 30 wt% or less of rhenium and 30 wtppm or more and 90 wtppm or less of potassium, and having a peak density (Spd) of 7,000 or more and 11,000 or less as a surface roughness parameter.

4. The manufacturing method according to claim 1 , wherein the Spd is 8,000 or more and 9,000 or less.

5. 4. The manufacturing method according to claim 1, wherein the surface roughness parameter of the tungsten wire is a developed area ratio (Sdr) of the interface of 0.16 or less.

6. 4. The manufacturing method according to claim 1, wherein the surface roughness parameter of the tungsten wire has an arithmetic mean peak curvature (Spc) of 300 or more and 500 or less.

7. 4. The manufacturing method according to claim 1, wherein the root mean square slope (Sdq) of the surface roughness parameter of the tungsten wire is 0.60 or less.

8. 4. The method according to claim 1, wherein the diameter of the tungsten wire is 0.3 mm or more and 1.0 mm or less.

9. 4. The method of claim 1, wherein the ratio of the length of the tungsten wire having a diameter variation of 1.0% or less to the total length is 95% or more.

10. 10. A probe pin manufactured by the manufacturing method of claim 1, having a straight portion with a diameter of 0.05 mm or more and 0.20 mm or less, and a total length of 20 mm or more and 100 mm or less, wherein the proportion of the length in which the wire diameter variation is 1.0% or less is 95% or more of the total length.

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