Probe pin material formed of ag-pd-cu-based alloy, and probe pin

Abstract

A probe pin material according to the present invention comprises an Ag-Pd-Cu-based alloy containing Ag, Pd, Cu, Zn, Sn, and B. Regarding the concentrations of additional elements Zn, Sn, and B, the Zn concentration is 0.5-2.5 mass%, the Sn concentration is 0.5-2.5 mass%, and the B concentration is 0.05-0.5 mass%. Regarding the Ag-Pd-Cu-based alloy according to the present invention, when X represents the Ag concentration, Y represents the Pd concentration, and Z represents Cu concentration + Zn concentration + Sn concentration + B concentration, X, Y, and Z are located within a range enclosed by straight lines connecting points A1 to A4 in an X-Y-Z pseudo ternary phase diagram. Point A1 (X: 24 mass%, Y: 40 mass%, Z: 36 mass%) Point A2 (X: 34 mass%, Y: 40 mass%, Z: 26 mass%) Point A3 (X: 17 mass%, Y: 57 mass%, Z: 26 mass%) Point A4 (X: 7 mass%, Y: 57 mass%, Z: 36 mass%)

Description

Probe pin material and probe pin made of Ag-Pd-Cu alloy

[0001] The present invention relates to an alloy material suitable for probe pins used in testing electrical and electronic devices, semiconductor devices, etc. More specifically, the present invention relates to a probe pin material made of an Ag-Pd-Cu alloy containing predetermined additive elements, which can be made even harder than before by optimized age hardening.

[0002] Probe testing equipment equipped with a probe card is used to test the continuity and operating characteristics of elements mounted on the circuit boards of various electronic devices and the semiconductor wafers of semiconductor devices. The probe card supports a large number of probe pins, and testing is performed by contacting the probe pins with the electrodes of the elements to send and receive electrical signals between the electrodes.

[0003] Probe pins are used in harsh environments where they repeatedly contact and separate from the electrode while electricity is being applied. Therefore, probe pin materials must have low electrical resistance as a conductive material, as well as mechanical properties such as hardness and springiness, corrosion resistance, chemical stability, etc. Of these properties, hardness is particularly important, as it is the main property that affects the wear resistance of the probe pin.

[0004] Several alloys have been proposed as probe pin materials. For example, the present applicant has proposed a precious metal-based alloy whose main component is a precious metal such as Pt or Au. These precious metal alloys are particularly excellent in wear resistance and are known as probe pin materials with high hardness due to plastic processing and precipitation effects (Patent Documents 1 and 2).

[0005] Additionally, Ag-Pd-Cu alloys are known as alloys that are frequently used as probe pin materials. The Ag-Pd-Cu alloy, which is the basis of this alloy, has relatively low resistance and can exhibit increased hardness due to the PdCu phase (bcc structure), an intermetallic compound formed by aging precipitation. Furthermore, Ag-Pd-Cu alloys can be improved in properties such as oxidation resistance and workability by adding various additive elements (hereinafter, alloys with additive elements added to Ag-Pd-Cu alloys will be referred to as Ag-Pd-Cu alloys). Due to these advantages, Ag-Pd-Cu alloys have been widely used as probe pin materials.

[0006] Examples of Ag-Pd-Cu alloy probe pin materials include Ag-Pd-Cu alloys containing In as an additive element (Patent Document 3), Ag-Pd-Cu alloys containing B as an additive element (Patent Document 4), and Ag-Pd-Cu alloys containing In and / or Zn as additive elements (Patent Document 5). These Ag-Pd-Cu alloys aim to improve resistivity, hardness, and processability by specifying the additive element and optimizing the composition ratio of the constituent metals (Pd and Cu). The present applicant has also reported on Ag-Pd-Cu alloys (Patent Document 6). In this prior art, the present applicant discloses an Ag-Pd-Cu alloy containing B as a first additive element and at least one of Sn, Bi, and Zn as a second additive element. The Ag-Pd-Cu alloy developed by the present applicant takes into consideration required properties such as resistance value and hardness, while improving bending resistance when processing probe pins.

[0007] Japanese Patent No. 4176133 Japanese Patent No. 4216823 International Publication WO2019 / 194322 International Publication WO2019 / 130511 Japanese Patent No. 4878401 Japanese Patent No. 7072126

[0008] As described above, probe pin materials have been developed to date while taking into consideration basic required characteristics such as hardness and low resistance, while also striving to provide added value such as improved processability and a better balance between these. However, as mentioned above, the primary requirement for probe pin materials is hardness to ensure wear resistance. Therefore, focusing on hardness, the probe pin materials made of Ag-Pd-Cu alloys described in the prior art described above have a maximum hardness of approximately 550 Hv, even after age hardening. In this regard, the applicant believes that there is still room for improvement in the hardness of Ag-Pd-Cu alloys.

[0009] Therefore, the present invention provides a probe pin material made of an Ag-Pd-Cu alloy that has a hardness higher than conventional materials. Specifically, the present invention provides a probe pin material made of an Ag-Pd-Cu alloy that can exhibit a Vickers hardness of 580 Hv or more by undergoing aging heat treatment. In achieving this objective, the present invention also takes into consideration the workability when processing the Ag-Pd-Cu alloy into the shape and dimensions required for the probe pin.

[0010] As described above, Ag—Pd—Cu alloys are age-hardening alloys whose hardness increases due to precipitation hardening caused by aging heat treatment. The reason why such age-hardening alloys are suitable as probe pin materials is that the timing of hardening the alloy can be adjusted during the process from manufacturing (casting) to processing into probe pins. Probe pins are manufactured from wire-shaped materials with thin wire diameters, and even the tip of the probe pin may be finely processed. For such high processing rates and processing requiring fine precision, it is preferable that the workpiece be somewhat soft. In the case of age-hardening alloys, high hardness can be achieved while maintaining a near-shape state by processing them in a soft state before aging and then performing aging heat treatment.

[0011] Therefore, in order to achieve high hardness, which is the object of the present invention, while taking workability into consideration, it is necessary to increase the difference in hardness before and after aging heat treatment. In other words, it is necessary to increase the increase in hardness due to precipitation hardening caused by aging heat treatment. Furthermore, in order to maximize the effect of precipitation hardening, it is necessary to promote the formation and dispersion of intermetallic compounds, which are precipitates.

[0012] Based on the above viewpoints, the present inventors have attempted to optimize the additive elements in order to promote the precipitation of intermetallic compounds in Ag-Pd-Cu alloys. As a result, they have found that it is preferable to simultaneously add both Zn and Sn as essential additive elements. They then attempted to optimize the ranges of the constituent elements and their composition ranges for Ag-Pd-Cu alloys containing Zn and Sn, and arrived at the present invention.

[0013] That is, the present invention, which solves the above-mentioned problems, is a probe pin material made of an Ag-Pd-Cu alloy containing Ag, Pd, Cu, and essential additive elements Zn, Sn, and B, wherein the Zn concentration is from 0.5 to 2.5 mass%, the Sn concentration is from 0.5 to 2.5 mass%, and the B concentration is from 0.05 to 0.5 mass%, and X, Y, and Z are located within a first region indicated by a polygon (A1-A2-A3-A4) formed by straight lines connecting the following four points A1, A2, A3, and A4 in an X-Y-Z pseudo ternary phase diagram, where X is the Ag concentration, Y is the Pd concentration, and Z is the Cu concentration + Zn concentration + Sn concentration + B concentration.・First area Point A1 (X: 24% by mass, Y: 40% by mass, Z: 36% by mass) Point A2 (X: 34% by mass, Y: 40% by mass, Z: 26% by mass) Point A3 (X: 17% by mass, Y: 57% by mass, Z: 26% by mass) Point A4 (X: 7% by mass, Y: 57% by mass, Z: 36% by mass)

[0014] The structure and properties of the probe pin material according to the present invention will be described in detail below. In this specification, an alloy consisting of only the three elements Ag, Pd, and Cu will be referred to as an "Ag-Pd-Cu alloy." Additionally, an alloy containing Ag, Pd, Cu, and one or more other elements will be referred to as an "Ag-Pd-Cu-based alloy."

[0015] I. Composition of the Probe Pin Material According to the Present Invention As described above, the probe pin material according to the present invention is made of an Ag-Pd-Cu alloy. This Ag-Pd-Cu alloy is a six-element or higher alloy in which the essential additive elements Zn, Sn, and B are added to an Ag-Pd-Cu alloy (ternary alloy). Below, the constituent elements of the Ag-Pd-Cu alloy that constitutes the probe pin material according to the present invention and their composition ranges will be described.

[0016] I-1. Constituent Elements of the Probe Pin Material According to the Present Invention (1) Ag, Pd, Cu The probe pin material according to the present invention uses an Ag-Pd-Cu alloy because the Ag-Pd-Cu alloy, which is its basic constituent, is expected to increase in hardness due to age hardening as described above, and is also a conductive material with lower resistance compared to precious metal-based alloys, etc. Therefore, Ag, Pd, and Cu are essential constituent elements that are fundamental for ensuring the strength, hardness, electrical conductivity, etc. of the probe pin material.

[0017] (2) Zn, Sn In the present invention, both Zn and Sn are essential additive elements to enhance the age-hardening effect of Ag—Pd—Cu alloys. Zn and Sn form intermetallic compounds with Pd (PdZn, PdSn), respectively. As described above, Ag—Pd—Cu alloys exhibit precipitation hardening due to the PdCu phase (bcc), but the formation of intermetallic compounds (PdZn, PdSn) with Zn and Sn further enhances hardness. In other words, the addition of both Zn and Sn improves the efficiency of precipitation hardening due to aging heat treatment. As a result, in the present invention, the increase in hardness due to aging heat treatment is greater than that of conventional Ag—Pd—Cu alloys, allowing for hardness greater than that achieved by conventional techniques.

[0018] As described above, the Ag—Pd—Cu alloy of the present invention requires the simultaneous addition of both Zn and Sn; the addition of only one of them does not significantly increase the hardness. The prior art (Patent Document 6) by the applicant of the present application also includes the addition of Zn and Sn to the Ag—Pd—Cu alloy, but does not require the simultaneous addition of Zn and Sn. Furthermore, the composition range of the basic Ag—Pd—Cu alloy differs from that of the prior art. This is because the prior art places more importance on improving bending resistance than on hardness after aging heat treatment.

[0019] (3) B In the present invention, in addition to Zn and Sn, B is also an essential additive element. B is added to ensure the basic strength and hardness of the alloy regardless of whether or not aging heat treatment is performed. Furthermore, B, when present near the grain boundaries of the alloy, imparts ductility to the alloy and contributes to ensuring workability.

[0020] (4) Other Additive Elements and Inevitable Impurities The probe pin material according to the present invention is essentially composed of an Ag-Pd-Cu alloy composed of Ag, Pd, Cu, Zn, Sn, and B. However, the probe pin material according to the present invention may contain other elements to the extent that the effects of the above-mentioned constituent elements are not impaired. Examples of such other elements include Ti. Furthermore, the probe pin material according to the present invention may contain unavoidable impurities. Unavoidable impurities are elements that are mixed in from raw materials and manufacturing / processing equipment. Such elements may include, in addition to the above-mentioned other additive elements, Au, Co, Cr, Fe, Ir, Mg, Ni, Pt, Rh, Ru, Si, Zr, Al, Ca, etc.

[0021] I-2. Alloy composition of the probe pin material according to the present invention In the Ag-Pd-Cu alloy of the present invention, the concentrations of the essential additive elements Zn, Sn, and B are set so as to optimize the increase in hardness due to aging heat treatment, and the concentrations of Ag, Pd, and Cu are determined taking these ranges into consideration. The concentration ranges of each additive element and the composition of the Ag-Pd-Cu alloy of the present invention are explained below.

[0022] (1) Zn Concentration and Sn Concentration The Zn and Sn concentrations in the Ag—Pd—Cu-based alloy of the present invention are 0.5% by mass to 2.5% by mass, and 0.5% by mass to 2.5% by mass, respectively. If either of these is less than 0.5% by mass, it becomes difficult to form an intermetallic compound in an amount effective for exhibiting precipitation hardening. Furthermore, even if either of these exceeds 2.5% by mass, there is no significant difference in hardness after aging heat treatment. Furthermore, if excessive amounts of Zn and Sn are added, intermetallic compounds may form before aging heat treatment (casting stage), potentially resulting in reduced workability. The preferred concentrations of these additive elements are 0.7% by mass to 1.5% by mass for the Zn concentration and 1.0% by mass to 2.0% by mass for the Sn concentration.

[0023] (2) B Concentration The B concentration is set to 0.05% by mass or more and 0.5% by mass or less. If the B concentration is less than 0.05% by mass, the above-mentioned effect is not exhibited, and if it exceeds 0.5% by mass, workability tends to decrease. The B concentration is more preferably set to 0.1% by mass or more and 0.3% by mass or less. Note that B does not have the effect of accelerating age hardening, but has the above-mentioned auxiliary effect, so the amount of B added is lower than that of Zn and Sn.

[0024] (3) Ag Concentration (X), Pd Concentration (Y), Cu Concentration The Ag concentration, Pd concentration, and Cu concentration of the Ag—Pd—Cu alloy of the present invention are set within optimal ranges for ensuring hardness, electrical conductivity, and the like, while keeping the Zn, Sn, and B concentrations within the above-mentioned ranges. Specifically, in the Ag—Pd—Cu alloy of the present invention, X, Y, and Z are located within a first region defined by a polygon (A1-A2-A3-A4) drawn by straight lines connecting four points A1, A2, A3, and A4 in an X-Y-Z pseudo-ternary phase diagram, where X is the Ag concentration, Y is the Pd concentration, and Z is the Cu concentration + Zn concentration + Sn concentration + B concentration. Note that "within the range of the polygon drawn by straight lines connecting the points" includes cases where the concentrations of each element are located on the lines (on the sides) and vertices of the polygon. In the Ag-Pd-Cu alloy of the present invention, the sum of the concentrations of Ag, Pd, and Cu in the first region (A1-A2-A3-A4) and the concentrations of the added elements Zn, Sn, and B is 100 mass %. Figure 1 shows the X-Y-Z pseudo-ternary phase diagram defined above and the first region (A1-A2-A3-A4).

[0025] ・First area Point A1 (X: 24% by mass, Y: 40% by mass, Z: 36% by mass) Point A2 (X: 34% by mass, Y: 40% by mass, Z: 26% by mass) Point A3 (X: 17% by mass, Y: 57% by mass, Z: 26% by mass) Point A4 (X: 7% by mass, Y: 57% by mass, Z: 36% by mass)

[0026] The reason why X (Ag concentration), Y (Pd concentration), and Z (Cu concentration + Zn concentration + Sn concentration + B concentration) including Cu concentration are set within the above range is to make the hardness of the Ag-Pd-Cu alloy after age hardening conform to the objective of the present invention (580 Hv or more) and to sufficiently precipitate the PdCu phase and the intermetallic compounds of PdZn and PdSn. If X, Y, and Z are outside the above range, the precipitation of the PdCu phase and the intermetallic compounds of PdZn and PdSn will be insufficient, making it difficult to achieve the desired hardness.

[0027] Furthermore, in the Ag-Pd-Cu alloy of the present invention, where X (Ag concentration), Y (Pd concentration), and Z (Cu concentration + Zn concentration + Sn concentration + B concentration) are within the first region, the increase in hardness after aging can be further increased by adjusting the concentrations of each constituent element. That is, it is preferable to set X (Ag concentration), Y (Pd concentration), and Z (Cu concentration + Zn concentration + Sn concentration + B concentration) within the second region, which is represented by a polygon (B1-B2-B3-B4) drawn by straight lines between the four points B1, B2, B3, and B4 in the same X-Y-Z pseudo-ternary phase diagram as above. This X-Y-Z pseudo-ternary phase diagram and the second region (B1-B2-B3-B4) are shown in FIG. 2.

[0028] ・Second area Point B1 (X: 22% by mass, Y: 43% by mass, Z: 35% by mass) Point B2 (X: 30% by mass, Y: 42% by mass, Z: 28% by mass) Point B3 (X: 18% by mass, Y: 54% by mass, Z: 28% by mass) Point B4 (X: 11% by mass, Y: 54% by mass, Z: 35% by mass)

[0029] Furthermore, it is particularly preferable to set X (Ag concentration), Y (Pd concentration), and Z (Cu concentration + Zn concentration + Sn concentration + B concentration) within the range of a third region shown by a polygon (C1-C2-C3-C4) formed by straight lines surrounding the following four points C1, C2, C3, and C4 in the X-Y-Z pseudo ternary phase diagram. This X-Y-Z pseudo ternary phase diagram and the third region (C1-C2-C3-C4) are shown in Figure 3.

[0030] - Third area Point C1 (X: 20% by mass, Y: 46% by mass, Z: 34% by mass) Point C2 (X: 25% by mass, Y: 46% by mass, Z: 29% by mass) Point C3 (X: 20% by mass, Y: 51% by mass, Z: 29% by mass) Point C4 (X: 15% by mass, Y: 51% by mass, Z: 34% by mass)

[0031] (4) Concentration of Other Additive Elements and Inevitable Impurities In the Ag-Pd-Cu alloy of the present invention, considering the inclusion of the aforementioned additional element Ti, its concentration is preferably 0.1% by mass or more and 1.3% by mass or less. Furthermore, the total concentration of unavoidable impurities is preferably 0.02% by mass or less, more preferably 0.005% by mass or less. When the aforementioned additional elements and unavoidable impurities are detected in the probe pin material of the present invention, the sum of the concentrations of the essential constituent elements (Ag, Pd, Cu, Zn, Sn, B) and the concentrations of the other additional elements and unavoidable impurities is 100% by mass, but X (Ag concentration), Y (Pd concentration), and Z (Cu concentration + Zn concentration + Sn concentration + B concentration) are within the ranges of the first to third regions described above.

[0032] The method for measuring the concentrations of each constituent element (Ag concentration, Pd concentration, Cu concentration, Zn concentration, Sn concentration, and B concentration) of the Ag—Pd—Cu alloy according to the present invention is not particularly limited. Examples of applicable measurement methods include inductively coupled plasma (ICP) emission spectroscopy and X-ray fluorescence analysis (XRF analysis). Furthermore, analytical methods such as energy dispersive X-ray analysis (EDX, EDS), electron probe microanalysis (EPMA), and energy dispersive wavelength dispersive X-ray analysis (WDX, WDS) can also be applied. These analytical methods allow the Ag concentration, Pd concentration, Cu concentration, Zn concentration, Sn concentration, and B concentration to be measured, respectively, and X, Y, and Z can be calculated. The same applies to the measurement of the concentrations of other additive elements and inevitable impurities.

[0033] II. Hardness and Morphology of the Probe Pin Material According to the Present Invention The Ag—Pd—Cu alloy constituting the probe pin material according to the present invention exhibits higher hardness than conventional Ag—Pd—Cu alloys by subjecting it to aging treatment due to the promotion of precipitation of intermetallic compounds by Zn and Sn as described above. Specifically, Ag—Pd—Cu alloys having a composition within the first region have a Vickers hardness of 580 Hv or more after aging treatment. Furthermore, Ag—Pd—Cu alloys having a composition within the second region have a hardness of 600 Hv or more after aging treatment. Furthermore, Ag—Pd—Cu alloys having a composition within the first region have a hardness of 620 Hv or more after aging treatment. The upper limit of hardness after aging treatment is preferably about 700 Hv. This is because even after the aging heat treatment, simple bending or the like may be performed, and in consideration of this workability, it becomes difficult to use an excessively hard probe pin material.

[0034] The hardness of the probe pin material according to the present invention is due to the particle dispersion effect of the precipitates made of the intermetallic compounds described above. Here, the detailed composition (proportion of each metal atom) of the intermetallic compounds precipitated in the Ag—Pd—Cu alloy of the present invention is not clear. However, the intermetallic compounds precipitated in the Ag—Pd—Cu alloy of the present invention are presumed to be PdCu phases containing Zn and Sn, i.e., intermetallic compounds composed of Zn, Sn, Pd, and Cu. Cu in the Ag—Pd—Cu alloy forms a PdCu phase with Pd, and Zn and Sn each bond with Pd to form intermetallic compounds (PdZn, PdSn). Therefore, the probe pin material according to the present invention has intermetallic compounds containing all of Pd, Cu, Zn, and Sn in its structure.

[0035] Regarding the confirmation of the presence of intermetallic compounds in the material structure of Ag-Pd-Cu alloys, when the material structure of Ag-Pd-Cu alloys is observed using a scanning electron microscope (SEM) or the like, dispersed phases of different hues are often observed, and these dispersed phases can be assumed to be intermetallic compound phases. As a detailed identification method, elemental mapping is created using analytical tools capable of area analysis, such as EDX, EDS, and EPMA. If all of the elements Zn, Sn, Pd, and Cu are present in the same location, this indicates the presence of an intermetallic compound containing all of Pd, Cu, Zn, and Sn in that location. In particular, with regard to Zn and Sn, if there is a region where higher concentrations of Zn and Sn are observed than in the entire alloy, this region can be identified as an intermetallic compound phase.

[0036] As described above, probe pin materials made of age-hardenable alloys are melt-cast and then cold-worked to form wire or rod material into the shape of a probe pin or a shape similar thereto. They are then hardened by aging heat treatment. The present invention is well suited to such processing and heat treatment processes. This is because the Ag—Pd—Cu-based alloy of the present invention has a hardness appropriate for workability before aging heat treatment. Specifically, the probe pin material made of the Ag—Pd—Cu-based alloy of the present invention preferably has a Vickers hardness of 360 Hv or more and 450 Hv or less, more preferably 360 Hv or more and 410 Hv or less, before aging treatment.

[0037] The probe pin material processed in the above steps before aging has the form of a straight wire or rod. In processing steps such as cold wire drawing, materials with poor workability will break in the worst case, but even if this does not happen, deformation such as bending is likely to occur. The present invention, which has good workability, minimizes not only wire breakage but also bending deformation during processing. Specifically, the probe pin material according to the present invention can have a straightness of 2 mm / 1000 mm or less when in the form of a wire or rod. The straightness is defined as the maximum value l of the distance l between the sample and the horizontal plane when a wire or rod of a predetermined length L is used as a sample and both ends of the sample are placed on a horizontal plane and the distance l between the sample and the horizontal plane is measured. ｍａｘ and the ratio of the sample length L (l ｍａｘ In the present invention, the maximum distance l when the predetermined length L is 1000 mm is ｍａｘ is preferably 2 mm or less (2 mm / 1000 mm or less).

[0038] The Ag-Pd-Cu alloy of the present invention is naturally used for probe pin applications, but is often used in the form of a wire or rod. The dimensions of these forms are not particularly limited, but the alloy is often used as a wire with a diameter of 50 μm or more and 1000 μm or less. The hardness of 580 Hv or more is preferably achieved when the alloy is made into a wire.

[0039] III. Manufacturing Method of Probe Pin Material According to the Present Invention The probe pin material according to the present invention can be manufactured by producing an alloy ingot of the Ag-Pd-Cu alloy having the above-described composition by melt casting, cold working the alloy ingot to a size and shape suitable for a probe pin, and then performing an aging heat treatment. In the melt casting method, the alloy ingot can be produced by casting after vacuum melting (reduced pressure melting) or atmospheric melting (atmosphere melting). Continuous casting and arc melting can also be applied. Furthermore, the cast alloy may be hot worked and then cold worked.

[0040] The cold working process is a process for forming the Ag-Pd-Cu alloy ingot into a desired shape and size, and for introducing processing strain into the alloy to obtain the strength and hardness required for a probe pin. The cold working method can be appropriately selected from rolling (including groove rolling), wire drawing, drawing / extrusion, etc., and these can be repeated multiple times or combined. The processing temperature is preferably 100°C or less.

[0041] The aging heat treatment is a process for obtaining a desired hardness by subjecting the Ag—Pd—Cu alloy after cold working to a heat treatment to precipitate a PdCu ordered phase. The temperature for the aging heat treatment is preferably 300° C. or higher and 580° C. or lower. The treatment time is preferably 10 minutes or higher and 4 hours or lower.

[0042] The aging heat treatment is preferably performed in combination with a solution heat treatment. The solution heat treatment is a treatment in which the Ag—Pd—Cu alloy is heat-treated at a high temperature to bring it into a homogeneous supersaturated solid solution state, and is a treatment for optimizing the precipitation of a PdCu ordered phase by the subsequent aging heat treatment. The heating temperature of the solution heat treatment for the Ag—Pd—Cu alloy of the present invention is preferably 650°C or higher and 950°C or lower. Cooling after heating is preferably performed by rapid cooling, such as water cooling.

[0043] The solution treatment can be performed multiple times. In the cold working step described above, wire drawing and the like can be performed multiple times, but an Ag—Pd—Cu-based alloy with optimal properties can be obtained by performing the solution treatment between these multiple cold working steps and then performing aging heat treatment after the final cold working. When performing a combination of cold working and solution treatment multiple times in this way, it is preferable to perform the solution heat treatment while controlling, for example, the working rate (cross-sectional area reduction rate) in each cold working step to 12% or more and 99.99% or less.

[0044] The Ag—Pd—Cu alloy that has undergone the aging heat treatment has a suitable hardness of at least 580 Hv. It can then be made into a probe pin by performing final processing (cutting, bending, etc.) to obtain a detailed product shape. There are no limitations on the shape or dimensions of the probe pin, and it can be applied to vertical probe pins, cantilever probe pins, and probe pins with a shape known as pogo pins.

[0045] As explained above, the probe pin material according to the present invention is based on an Ag-Pd-Cu alloy, but contains additional elements (Zn, Sn) that have a significant effect of increasing hardness through precipitation, thereby making it possible to produce probe pins with a higher hardness than conventional materials.

[0046] 1 is a diagram showing an X-Y-Z pseudo ternary phase diagram (X: Ag concentration, Y: Pd concentration, Z: Cu concentration + Zn concentration + Sn concentration + B concentration) of the Ag—Pd—Cu alloy of the present invention, and a first region range (A1-A2-A3-A4). 2 is a diagram showing an X-Y-Z pseudo ternary phase diagram (X: Ag concentration, Y: Pd concentration, Z: Cu concentration + Zn concentration + Sn concentration + B concentration) of the Ag—Pd—Cu alloy of the present invention, and a second region range (B1-B2-B3-B4). 3 is a diagram showing an X-Y-Z pseudo ternary phase diagram (X: Ag concentration, Y: Pd concentration, Z: Cu concentration + Zn concentration + Sn concentration + B concentration) of the Ag—Pd—Cu alloy of the present invention, and a third region range (C1-C2-C3-C4). FIG. 1 is a diagram showing the composition of the Ag—Pd—Cu-based alloy produced in the first embodiment in an X-Y-Z pseudo ternary phase diagram. FIG. 2 is a diagram explaining a method for measuring the straightness of the Ag—Pd—Cu-based alloy wire produced in the first embodiment. FIG. 3 is a diagram showing the composition of the Ag—Pd—Cu-based alloy produced in the second embodiment in an X-Y-Z pseudo ternary phase diagram. FIG. 4 is an SEM image of the Ag—Pd—Cu-based alloy No. 37 produced in the second embodiment. FIG. 5 is a diagram showing the EDS analysis results (element mapping) of the Ag—Pd—Cu-based alloy No. 37 produced in the second embodiment. FIG. 6 is a diagram showing the EDS analysis results (point analysis) of the Ag—Pd—Cu-based alloy No. 37 produced in the second embodiment.

[0047] First Embodiment: A preferred embodiment of the present invention will be described below. In this embodiment, probe pin materials made of Ag-Pd-Cu alloys of various compositions were manufactured, and their hardness was measured.

[0048] In this embodiment, Ag—Pd—Cu—Zn—Sn raw metals (purity 99.9% or higher) were mixed with 99.5% pure B powder, and the mixture was melt-cast to produce Ag—Pd—Cu alloy ingots (6 mm in diameter). The concentrations of each constituent element in the produced alloy ingots of various compositions were analyzed using ICP. The compositions of the Ag—Pd—Cu alloys produced in the examples of this embodiment in the X-Y-Z pseudo-ternary phase diagram are shown in FIG. 4 . Note that FIG. 4 is a partially enlarged view of the X-Y-Z pseudo-ternary phase diagram (X: 0% to 50% by mass, Y: 30% to 80% by mass, Z: 20% to 70% by mass).

[0049] Next, Ag-Pd-Cu alloy ingots of various compositions were heat-treated at 850°C for 30 minutes, and then processed into 4 mm square rods by cold groove rolling. These rods were heated at 850°C for 30 minutes, and then water-cooled for solution treatment. The rods were then cold-drawn into wires with a diameter of 0.7 mm, which were then subjected to aging treatment. The aging treatment was performed at a temperature of 320 to 420°C for 60 minutes.

[0050] In this embodiment, as comparative examples for the Ag-Pd-Cu alloys of each example, wire rods were also produced: an Ag-Pd-Cu ternary alloy without the addition of Zn, Sn, or B, and an Ag-Pd-Cu alloy with only Zn or Sn added. Furthermore, wire rods were also produced of Ag-Pd-Cu alloys with In, Zr, Bi, or Cr added instead of Sn. The manufacturing process for these comparative wire rods was the same as that of the above examples.

[0051] [Hardness Measurement] The hardness of the Ag—Pd—Cu alloy wires of various compositions produced above was measured. Hardness measurements were performed using a micro Vickers hardness tester (HM-200, manufactured by Mitutoyo Corporation) with a load of 100 gf and an indentation time of 10 seconds. Measurements were performed at a total of 13 locations on vertical and horizontal lines intersecting the center of the wire cross section, and the average value was used as the hardness value. Furthermore, hardness measurements were performed on wires (diameter 0.7 mm) after cold wire drawing before and after aging heat treatment, and the increase in hardness due to aging heat treatment was calculated from each hardness value.

[0052] [Workability Evaluation] In this embodiment, the workability of the Ag—Pd—Cu alloy was also evaluated. The workability was evaluated based on the presence or absence of cracks during groove rolling and wire breakage during cold wire drawing in the wire processing step described above. Specifically, a wire (0.7 mm diameter) that could be processed without any cracks or breakage was evaluated as pass (◯); a wire that broke once or twice during cold wire drawing but could be processed into a sample was evaluated as fail (Δ); and a wire that could not be produced at all due to frequent breakage was evaluated as fail (×).

[0053] [Straightness Evaluation] Furthermore, the straightness of the wire (diameter 0.7 mm) after cold wire drawing (before aging heat treatment) was evaluated. The straightness was measured as shown in Figure 5. The wire was cut to a length L of 1000 mm as a sample, and the sample was placed so that both ends were in contact with a horizontal table. The distance l between the horizontal table and the sample was measured, and the maximum value l was ｍａｘ In this embodiment, the evaluation standard for straightness is ｍａｘ ≦2 mm / 1000 mm, and cases where this evaluation criterion was met were rated as pass (◯), and cases where this criterion was not met were rated as fail (×).

[0054] Table 1 shows the evaluation results of the hardness, workability, and straightness of the probe pin materials of the Ag-Pd-Cu ternary alloy and the Ag-Pd-Cu alloy manufactured in this embodiment.

[0055]

[0056] It can be seen from Table 1 that the probe pin materials made of Ag—Pd—Cu-based alloys of Examples 1 to 8 manufactured in this embodiment exhibit high hardness, with Vickers hardness of 580 Hv or more after age hardening. The probe pin materials of these Examples showed an increase in hardness of 200 Hv or more due to age hardening. Furthermore, it was confirmed that the workability before aging heat treatment was good and that wire rods with good straightness could be manufactured.

[0057] However, if the concentration of either Zn or Sn exceeds 2.5 mass%, the workability of the wire rod decreases, so the upper limit of these elements should be 2.5 mass% (Comparative Examples 1 and 2). Furthermore, when only one of Zn and Sn is added in an appropriate amount, as in Comparative Examples 3 to 7, a hardness of approximately 570 Hv is exhibited, so a certain degree of high hardness can be expected. However, the increase in hardness due to age hardening in these comparative examples is less than 200 Hv, which is insufficient in terms of maximizing the effect of intermetallic compound precipitation. Furthermore, it has been confirmed that B is an additive element that affects workability. Since workability deteriorates without the addition of B and also deteriorates with excessive addition of B, the addition of B should also be essential.

[0058] Furthermore, the probe pin materials made of Ag-Pd-Cu ternary alloys containing no additive elements had low hardness overall, remaining at around 500 Hv (Comparative Examples 9 to 12). In these comparative examples, the increase in hardness due to age hardening was large, just like in the examples, but the hardness before aging was low, so the final hardness was significantly insufficient.

[0059] Furthermore, for Ag-Pd-Cu alloys in which In, Zr, Bi, or Cr was added together with Zn, some were expected to have high hardness, but the hardness increase was small and did not reach that of the respective examples (Comparative Examples 13 and 16). Furthermore, some alloys could not be processed due to cracking during groove rolling or breakage during cold wiredrawing (Comparative Examples 14 and 15). Therefore, it can be said that the combination of Zn and Sn is preferable.

[0060] Second Embodiment: In this embodiment, the effect of increasing hardness of the Ag—Pd—Cu-based alloy of the present invention was confirmed in detail within the composition ranges of the above-mentioned first to third regions. In this embodiment, a probe pin material was manufactured from a wire of an Ag—Pd—Cu-based alloy by adjusting the Zn concentration to about 1.0 mass %, the Sn concentration to about 1.4 mass %, and the B concentration to 0.15 mass %, and adjusting the concentrations of Ag, Pd, and Cu.

[0061] The manufacturing process and manufacturing conditions for the Ag—Pd—Cu alloy wire of this embodiment were the same as those of the first embodiment. The hardness of the wire cross section was measured in the same manner as in the first embodiment. The workability and straightness were also evaluated in the same manner as in the first embodiment. The evaluation results are shown in Table 2. An X-Y-Z pseudo-ternary phase diagram showing the composition of the Ag-Pd-Cu alloy manufactured in this embodiment is shown in FIG. 6. Similarly to FIG. 4, FIG. 6 is a partially enlarged X-Y-Z pseudo-ternary phase diagram. In FIG. 6, the compositions of the samples in the first region shown in Table 2 are indicated by "△", the compositions of the samples in the second region by "◯", and the compositions of the samples in the third region by "●".

[0062]

[0063] Table 2 confirms that all probe pin materials made of Ag—Pd—Cu alloy wires manufactured in the second embodiment achieved hardnesses of 580 Hv or higher after aging. Furthermore, alloys with compositions within the second region exhibited hardnesses of 600 Hv or higher. Furthermore, alloys with compositions within the third region exhibited extremely good hardnesses of 620 Hv or higher. For Ag—Pd—Cu alloys with compositions within the second and third regions, the increase in hardness due to age hardening significantly exceeded 200 Hv. Considering that the hardness before age hardening was not significantly different from that of the first region, it can be said that the effects of age hardening were even more effectively exhibited in the second and third regions. Even with such high-hardness probe pin materials, the hardness before aging heat treatment was not particularly high, making them easy to process. This can also be understood from the evaluation of workability.

[0064] The Ag—Pd—Cu alloy produced in this embodiment was observed for its material structure. A scanning electron microscope (SEM: JSM-IT700HR, manufactured by JEOL Ltd.) was used for the structure observation. Simultaneously with the SEM observation, elemental analysis of the observation area was performed using EDS (ULTIM MAX40, manufactured by Oxford Instruments) (accelerating voltage: 15 kV). The structure analysis was performed on the cross section of the wire before and after aging treatment.

[0065] As an example of the observation results, Figure 7 shows an SEM image of the Ag-Pd-Cu alloy No. 37. In Figure 7, the matrix phase and the intermetallic compound phase can be recognized by their different shades, with the dark gray phase being the intermetallic compound. From Figure 7, it can be seen that the intermetallic compound phase increases and disperses due to the aging heat treatment. In this No. 37, intermetallic compounds are formed, albeit in small amounts, even before the aging heat treatment.

[0066] Figure 8 shows the results of elemental mapping analysis by EDS for the material structure of Example 37. Figure 9 also shows the results of point analysis of the matrix phase and intermetallic compound phase. In the elemental mapping of Figure 8, the areas where the four elements Pd, Cu, Zn, and Sn are observed overlapping indicate the presence of intermetallic compounds. This point can be clearly confirmed from the point analysis of Figure 9, where spectral peaks for Zn and Sn are not observed in the matrix phase, but spectral peaks for the four elements Pd, Cu, Zn, and Sn are observed in the intermetallic compounds. This confirms that the Ag-Pd-Cu alloy of the present invention contains intermetallic compounds composed of Pd, Cu, Zn, and Sn.

[0067] As explained above, the probe pin material according to the present invention exhibits a more efficient age hardening effect than ever before, thereby achieving a high hardness. The probe pin material according to the present invention has excellent wear resistance due to this high hardness, and also takes into consideration processability. The present invention is applicable to probe pins of probe cards used for testing various electronic devices, semiconductor devices, power devices, etc. In particular, the present invention, which has excellent bending resistance, can be usefully applied to cantilever-type probe pins and probe pins shaped as known as pogo pins.

Claims

1. A probe pin material made of an Ag-Pd-Cu alloy containing Ag, Pd, Cu, and the essential additive elements Zn, Sn, and B, wherein the Zn concentration is 0.5% by mass or more and 2.5% by mass or less, the Sn concentration is 0.5% by mass or more and 2.5% by mass or less, and the B concentration is 0.05% by mass or more and 0.5% by mass or less, and X, Y, and Z are located within the range of a first region indicated by a polygon (A1-A2-A3-A4) formed by straight lines connecting the following four points A1, A2, A3, and A4 in an X-Y-Z pseudo ternary phase diagram, where X is the Ag concentration, Y is the Pd concentration, and Z is the Cu concentration + Zn concentration + Sn concentration + B concentration.・First area Point A1 (X: 24% by mass, Y: 40% by mass, Z: 36% by mass) Point A2 (X: 34% by mass, Y: 40% by mass, Z: 26% by mass) Point A3 (X: 17% by mass, Y: 57% by mass, Z: 26% by mass) Point A4 (X: 7% by mass, Y: 57% by mass, Z: 36% by mass) 2. The probe pin material according to claim 1, wherein X, Y, and Z are located within a second region defined by a polygon (B1-B2-B3-B4) drawn by straight lines connecting the following four points B1, B2, B3, and B4 in an X-Y-Z pseudo-ternary phase diagram, where X is the Ag concentration, Y is the Pd concentration, and Z is the Cu concentration + Zn concentration + Sn concentration + B concentration. Second region: Point B1 (X: 22 mass%, Y: 43 mass%, Z: 35 mass%) Point B2 (X: 30 mass%, Y: 42 mass%, Z: 28 mass%) Point B3 (X: 18 mass%, Y: 54 mass%, Z: 28 mass%) Point B4 (X: 11 mass%, Y: 54 mass%, Z: 35 mass%) 3. The probe pin material according to claim 1, wherein X, Y, and Z are located within a third region defined by a polygon (C1-C2-C3-C4) formed by straight lines connecting the four points C1, C2, C3, and C4 in an X-Y-Z pseudo-ternary phase diagram, where X is the Ag concentration, Y is the Pd concentration, and Z is the Cu concentration + Zn concentration + Sn concentration + B concentration. Third region: Point C1 (X: 20 mass%, Y: 46 mass%, Z: 34 mass%) Point C2 (X: 25 mass%, Y: 46 mass%, Z: 29 mass%) Point C3 (X: 20 mass%, Y: 51 mass%, Z: 29 mass%) Point C4 (X: 15 mass%, Y: 51 mass%, Z: 34 mass%) 4. The probe pin material according to claim 1, wherein the material structure comprises an intermetallic compound containing all of Pd, Cu, Zn and Sn.

5. The probe pin material according to claim 1, which has a Vickers hardness of 580 Hv or more.

6. A probe pin material according to claim 1, which has a wire or rod shape with a Vickers hardness of 360 Hv or more and 450 Hv or less in cross section before aging treatment and an elongation of 2 mm / 1000 mm or less.

7. A probe pin comprising the probe pin material according to any one of claims 1 to 5.

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