Conductive wire for electrical characteristic inspection, insulated wire, and probe card

Abstract

A conductive wire for electrical characteristic inspection according to the present invention is composed of a copper alloy that contains 0.1-30 mass% silver, with the remainder being copper and unavoidable impurities. The diameter of the conductive wire for electrical characteristic inspection is 0.2 mm or less. In a cross section of the conductive wire for electrical characteristic inspection, the ratio of the Vickers hardness of the center portion with respect to the Vickers hardness of the outer peripheral portion is in the range of 0.90-1.10. The Vickers hardness of the center portion and the Vickers hardness of the outer peripheral portion are both 250 HV or greater.

Description

Conductive wire for electrical property inspection, insulated wire, and probe card

[0001] The present invention relates to a conductive wire for electrical property inspection, an insulated wire, and a probe card.

[0002] In recent years, with the miniaturization of electronic devices, high-density mounting of various circuit boards used therein has been required. On the other hand, for various circuit boards such as these various mounting boards and IC package boards, it is common to perform inspections of various electrical properties such as measurement of DC resistance values and conduction inspections during manufacturing. Such inspections of electrical properties usually consist of a contact probe for contacting the electrodes of a circuit board and an inspection device (signal processing device) for measuring resistance values and the like through the contact probe. And for the conductive wires (metal wires) used in such inspection devices and contact probes, high straightness and appropriate wear resistance may be required.

[0003] Patent Document 1 describes a method for manufacturing a suspension wire having high straightness. In the manufacturing method described in Patent Document 1, a suspension wire is manufactured by continuously twisting a metal spring wire in a high-temperature atmosphere.

[0004] Japanese Patent Application Laid-Open No. 2003-94111

[0005] Since the contact probe is used continuously, for example, when adopting a suspension wire manufactured by the method described in Patent Document 1, it is necessary to frequently replace the contact probe due to wear, and the inspection cost tends to increase. Thus, when using a thin conductive wire for the above contact probe, there is room for consideration regarding wear resistance.

[0006] The main object of the present invention is to provide a conductive wire for electrical property inspection having appropriate wear resistance regardless of the tip shape. Another object of the present invention is to provide an insulated wire having the conductive wire for electrical property inspection and a probe card having the conductive wire for electrical property inspection or the insulated wire.

[0007] To solve the above problems, according to one aspect of the present invention, there is an electrical properties testing conductor made of a copper alloy containing 0.1 to 30% by mass of silver, with the remainder being copper and unavoidable impurities, wherein the diameter of the electrical properties testing conductor is 0.2 mm or less, the ratio of the Vickers hardness of the central part to the Vickers hardness of the outer part in the cross-section of the electrical properties testing conductor is in the range of 0.90 to 1.10, and both the Vickers hardness of the central part and the Vickers hardness of the outer part are 250 HV or more.

[0008] To solve the above problems, according to one aspect of the present invention, an insulated wire is provided, characterized by comprising: an electrical characteristic test conductor of the present invention; and an insulating coating covering the electrical characteristic test conductor.

[0009] To solve the above problems, according to one aspect of the present invention, a probe card is provided having a probe card body including a plurality of probe pins, and a plurality of lead wires connected to each of the plurality of probe pins, wherein at least a portion of the plurality of probe pins and the plurality of lead wires are the electrical characteristic testing conductor of the present invention or the insulated wire of the present invention.

[0010] According to the present invention, it is possible to provide electrical characteristic testing conductors, insulated wires, and probe cards that have appropriate wear resistance regardless of the tip shape.

[0011] Figure 1 is a schematic diagram illustrating a contact probe that can use the electrical characteristic testing wire of the present invention. Figures 2A and 2B are schematic diagrams illustrating the twisting process in the manufacturing method of the electrical characteristic testing wire of the present invention.

[0012] The following describes an electrical characteristic testing wire (hereinafter also simply referred to as "wire") according to one embodiment of the present invention, and a method for manufacturing the same. However, the wire and method for manufacturing the present invention are not limited to the embodiments shown below. In this specification, the "~" indicating a numerical range includes both an upper and lower limit.

[0013] (Composition of the Conductor for Electrical Characteristics Testing) The conductor in this embodiment is made of an alloy. The alloy contains silver, with the remainder being copper and unavoidable impurities. Examples of unavoidable impurities include tin, beryllium, zinc, nickel, magnesium, aluminum, titanium, zirconium, indium, silicon, and phosphorus. The unavoidable impurities may be one type or two or more types. The silver content is appropriately selected according to the desired characteristics of the conductor, but is 0.1 to 30% by mass, with 3 to 15% by mass being more preferable. When the amount of silver is within this range, it is easier to set the hardness and conductivity of the conductor to the desired range.

[0014] The diameter of the conductor is selected appropriately depending on the application of the conductor, but it is 0.2 mm or less, and more preferably within the range of 0.01 to 0.1 mm. When the diameter of the conductor is within this range, the conductors can be arranged at a narrow pitch, for example, when used in electrical characteristic testing equipment or probe pins.

[0015] The shape of the conductor tip is not particularly limited. The conductor tip may be flat or needle-shaped (conical). The conductor tip shape is set appropriately according to the intended use.

[0016] The ratio of the Vickers hardness of the center to the Vickers hardness of the outer periphery in the cross-section of the conductor is within the range of 0.90 to 1.10. Here, "cross-section" refers to the cross-section in a direction perpendicular to the longitudinal direction of the conductor. "Center" refers to the region near the center of the conductor, for example, the region on the central side when the radius of the conductor is divided in two from the center. The center is the centroid of the cross-section of the conductor. "Outer periphery" refers to the region near the circumferential surface of the conductor, for example, the region from the outer circumferential surface of the conductor to a depth of half the radius of the conductor. Furthermore, the Vickers hardness of both the center and the outer periphery is 250 HV or higher. In this embodiment, there are no particular upper limits on the Vickers hardness of the center and the outer periphery, but it is generally preferable that both be 450 HV or lower. The Vickers hardness of the center is HV 250 or higher, and HV 400 or lower is preferable. Furthermore, the Vickers hardness of the outer circumference is HV250 or higher, preferably HV400 or lower. When the Vickers hardness is within the above range, it is easier to use as a conductor for electrical characteristic testing. Also, when the Vickers hardness is within the above range, if the tip shape of the conductor is flat, it will wear uniformly, and if the tip shape of the conductor is needle-shaped, the tip will not easily be crushed. The Vickers hardness in this specification is a value measured in accordance with JIS Z 2244 2009. Alternatively, the hardness may be measured by the nanoindentation method, and a relationship of Vickers hardness, which is a general indicator of hardness, is known to exist between nanoindentation hardness and Vickers hardness, for example, Vickers hardness = (76.2 × nanoindentation hardness) + 6.3 (Non-patent Literature 1: Metals, Vol. 78 (2008) No. 9, p. 47).

[0017] The wire drawing pitch is not particularly limited, but is preferably 2.0 mm or less. Here, "wire drawing pitch" refers to the distance that an alloy wire having unavoidable shallow scratches that occur parallel to the longitudinal direction during the wire drawing process (described later) advances in the longitudinal direction when the shallow scratches complete one rotation after twisting. If the wire drawing pitch is 2.0 mm or less, the Vickers hardness can be kept within a predetermined range.

[0018] Furthermore, the conductivity of the conductor is preferably 50% IACS or higher, and more preferably 57% IACS or higher. When the conductivity of the conductor is 50% IACS or higher, it becomes easier to use the conductor as a conductor for electrical characteristic testing. There is no particular upper limit to the conductivity of the conductor, but the upper limit is approximately 85% IACS.

[0019] The elongation of the conductor is preferably 1-5%. This elongation can be determined using a precision universal testing machine (for example, one manufactured by Shimadzu Corporation). If the elongation of the conductor is 5% or less, for example, even if the end of the conductor comes into repeated contact with other components, sagging is less likely to occur at the end.

[0020] The straightness of the conductor is preferable. The radius of curvature of the conductor is preferably 300 mm or more, and more preferably 1000 mm or more. When the conductor is straight, it is possible to suppress contact or entanglement between adjacent conductors when the conductor is used in equipment for electrical characteristic testing, etc. Furthermore, when the conductor is straight, it is easier to use the conductor for various applications. The radius of curvature can be calculated by selecting three points arbitrarily from the arc of the sample using a Keyence VHX-6000 digital microscope.

[0021] Conductors are primarily used in devices and equipment for testing electrical properties. Examples of applications for conductors include lead wires in electrical property testing equipment and probe pins in contact probes.

[0022] Here, we will explain the case where a conductive wire is used as a contact probe. Figure 1 shows a contact probe 20 for inspecting the electrical characteristics of a circuit board 10 having a substrate 11 and electrodes 12, and a part of the inspection device 30 connected thereto.

[0023] As shown in Figure 1, the contact probe 20 has a probe pin 22 and a support part 21 that supports it. The inspection device 30 has a lead wire 32, a holding part 31 that supports it, and a signal processing unit (not shown) connected to the lead wire 32. In the contact probe 20 and the inspection device 30, an electrical signal from the circuit board 10 is transmitted to the inspection device 30 by pressing the probe pin 22 against the electrodes 12 and lead wire 32 of the circuit board 10. The signal processing unit then detects the electrical signal, enabling measurement of the DC resistance of the circuit board 10, continuity testing, and other operations.

[0024] The conductor can be used for either the probe pins 22 of the contact probe 20 or the lead wires 32 of the inspection device 30. The probe pins 22 and lead wires 32 are subjected to repeated contact. Therefore, if the hardness of the conductor used for these is low, it may wear down due to repeated contact. Conventional conductors for electrical characteristic testing have a hard outer circumference but a soft core. In contrast, the conductor of this embodiment is hard not only at the outer circumference but also at the core, thus possessing appropriate wear resistance. Therefore, the conductor of this embodiment is very useful for the probe pins 22 and lead wires 32.

[0025] When conductors are used as probe pins 22 and lead wires 32, an insulating coating may be placed around the conductors (insulated wire). Placing an insulating coating around the conductors can suppress contact between adjacent lead wires 32. The insulating coating is a resin coating, similar to the insulating coatings of general conductors. Examples of resins that can be used for the insulating coating are not particularly limited as long as they have insulating properties. Examples of resins include parylene resin, acrylic resin, polyurethane resin, nylon resin, polyester resin, epoxy resin, polyesterimide resin, polyamide resin, and polyamideimide resin. The thickness of the insulating coating is also appropriately selected depending on the application. The thickness of the insulating coating is, for example, in the range of 1.0 to 10 μm.

[0026] Although not specifically shown in the diagrams, conductors and insulated wires can also be used for the probe pins and lead wires of a probe card. The probe card comprises a probe card body containing a plurality of probe pins and a plurality of lead wires connected to each of the plurality of probe pins. At least some of the plurality of probe pins and the plurality of lead wires are the conductors or insulated wires described above. One end of the probe pin is brought into contact with the inspection target area of ​​the object being inspected. The other end of the probe pin is connected to the inspection device via the lead wire.

[0027] (Method for manufacturing electrical characteristic test wires) The electrical characteristic test wire according to this embodiment can be manufactured, for example, by the following method. The manufacturing method according to this embodiment includes a step of preparing an alloy wire containing copper and silver (hereinafter also referred to as the "preparation step") and a step of rotating the alloy wire in the circumferential direction while conveying the alloy wire in one direction (hereinafter also referred to as the "twisting step").

[0028] In the preparation step, an alloy wire containing copper and silver is prepared. The composition of the alloy wire is the same as that of the alloy contained in the conductor wire described above. The alloy wire may be manufactured by any method, for example, by drawing a wire made from a cast material of any diameter. The diameter of the alloy wire to be prepared is 0.2 mm or less, and more preferably in the range of 0.01 to 0.1 mm.

[0029] Figure 2A is a schematic diagram showing an example of the configuration of a processing apparatus 200 that performs a twisting process, and Figure 2B is a schematic diagram showing the configuration of another processing apparatus 200 that performs a twisting process. In the twisting process, the alloy wire 130 prepared in the preparation process is twisted inside the processing apparatus 200. The configuration of the processing apparatus 200 that performs the twisting process is not particularly limited.

[0030] As shown in Figure 2A, the processing apparatus 200 has a pair of rotating plates (a first rotating plate 211a and a second rotating plate 211b) arranged opposite each other with the alloy wire 130 in between. The pair of rotating plates (the first rotating plate 211a and the second rotating plate 211b) are connected to a motor (not shown) and are configured to rotate together at a predetermined speed in the circumferential direction of the alloy wire 130, with the alloy wire 130 as the central axis. One of the rotating plates (the first rotating plate 211a in this embodiment) has a first support portion 212a and a third support portion 212c for supporting the alloy wire 130 at a predetermined height. The other rotating plate (the second rotating plate 211b in this embodiment) has a second support portion 212b for pushing the alloy wire 130 to a predetermined position. The ends of each support portion 212a, 212b, and 212c each have grooves (not shown) for supporting the alloy wire 130.

[0031] In the twisting process, the alloy wire 130 is first supported by the first support section 212a, the second support section 212b, and the third support section 212c of the processing device 200. At this time, the height and position of the first support section 212a, the second support section 212b, and the third support section 212c are adjusted so that the angle (α and β in Figure 2A) between the alloy wire 130, which is pushed in by the second support section 212b, and the transport direction is 10 to 70°. The angles α and β between the alloy wire 130 and the transport direction are more preferably 20 to 50°. The angles α and β may be different values, but it is preferable that they be the same value. Next, while the alloy wire 130 is transported from one bobbin 100 to the other bobbin 160 at a constant speed, the rotating plates of the processing device 200 (first rotating plate 211a, second rotating plate 211b) are rotated in the circumferential direction of the alloy wire 130 at a speed such that the wire drawing pitch is 2.0 mm or less. The twisting process is usually performed at room temperature.

[0032] Furthermore, as shown in Figure 2B, the processing apparatus 200 may be configured to transport the alloy wire 130 from one bobbin 100 to the other bobbin 160 at a constant speed while rotating one bobbin 100 at a constant speed in the circumferential direction of the alloy wire 130. In this case, it is preferable that the rotation speed of the bobbin 100 relative to the transport speed is within a range that results in a wire drawing pitch of 2.0 mm or less.

[0033] Furthermore, a straightening process may be included after the twisting process. The straightening process straightens the alloy wire 130 after the twisting process. The method of straightening is not particularly limited. Examples of straightening methods include rotary blade type and die rotation type. The radius of curvature of the conductor after straightening is preferably 300 mm or more, and more preferably 1000 mm or more. Furthermore, the drawing pitch after the straightening process is preferably 2.0 mm or less.

[0034] (Effects) As described above, according to the present invention, the diameter of the conductor is 0.2 mm or less, the ratio of the Vickers hardness of the center to the Vickers hardness of the outer circumference in the cross-section of the conductor is in the range of 0.90 to 1.10, and both the Vickers hardness of the center and the Vickers hardness of the outer circumference are 250 HV or more, and since both the center and the outer circumference are hard, it has appropriate wear resistance.

[0035] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way by these examples, and the embodiments can be modified without departing from the spirit of the invention.

[0036] (Manufacturing of electrical characteristic testing wires) Alloy wires containing 3, 10, or 15% by mass of silver, with the remainder being copper and unavoidable impurities, and having diameters of 0.05, 0.12, or 0.20 mm were prepared (preparation step). After drawing each copper alloy wire, it was twisted using the method shown in Figure 2 so that the drawing pitch was 0.2 to 3 mm (twisting step). Alloy wires that were not twisted were also prepared. None of the electrical characteristic testing wires underwent straightening.

[0037] The Vickers hardness of the central part and the outer peripheral part of the obtained wire for electrical property inspection was measured with a Vickers hardness tester in accordance with JIS Z 2244 2009. The Vickers hardness was measured with a test force of 25 gf and a holding time of the test force of 15 seconds. However, for a wire diameter of 0.05 mm, the test force was 10 gf and the holding time was the same as that for other wire diameters. From the measured Vickers hardness of the central part and the outer peripheral part, the ratio of the Vickers hardness of the central part to the Vickers hardness of the outer peripheral part was calculated.

[0038] (Evaluation) The tip shapes of the obtained wires for electrical property inspection were formed into a flat shape and a needle shape (a conical shape with the tip at the center). For each wire for electrical property inspection with a flat tip and each wire for electrical property inspection with a needle tip, the abrasion resistance was evaluated by the following method.

[0039] The abrasion resistance was visually observed for the shape of each wire for electrical property inspection after pressing it against the electrode of the circuit board in the apparatus for electrical property inspection 10,000 times. The abrasion resistance evaluation was judged according to the following criteria. Evaluation criteria for the wire for electrical property inspection with a flat tip ○: Uniform abrasion occurred. ×: Abrasion occurred from the center or the surface side. Evaluation criteria for the wire for electrical property inspection with a needle tip ○: The needle tip was difficult to be crushed. ×: The needle tip was easily crushed.

[0040] The comprehensive evaluation was judged according to the following criteria. ○: All of the evaluation results were "○". ×: Any of the evaluation results was "×".

[0041] The parameters of each wire for electrical property inspection and the evaluation results are shown in Tables 1 to 3.

[0042]

[0043]

[0044]

[0045] As shown in Tables 1 to 3, the diameter of the wire for electrical property inspection is 0.2 mm or less, and the ratio of the Vickers hardness of the central portion to the Vickers hardness of the outer peripheral portion in the cross section of the wire for electrical property inspection is within the range of 0.90 to 1.10, and the Vickers hardness of both the central portion and the outer peripheral portion is 250 HV or more. The wire for electrical property inspection had good abrasion resistance for both flat and needle-shaped tip portions.

[0046] On the other hand, the wire for electrical property inspection that was not subjected to twisting had poor abrasion resistance for the flat tip portion. Also, the wire for electrical property inspection with a ratio of the Vickers hardness of the central portion to the Vickers hardness of the outer peripheral portion in the cross section less than 0.90 had poor abrasion resistance for the flat tip portion.

[0047] The wire for electrical property inspection of the present invention can be used for various applications such as contact probes and lead wires of electrical property inspection devices.

[0048] 10 Circuit board 11 Substrate 12 Electrode 20 Contact probe 21 Support portion 22 Probe pin 30 Inspection device 31 Holding portion 32 Lead wire 100 Bobbin 130 Alloy wire 160 Bobbin 200 Processing device 211a First rotating plate 211b Second rotating plate 212a First support portion 212b Second support portion 212c Third support portion

Claims

1. An electrical properties testing wire comprising a copper alloy containing 0.1 to 30% by mass of silver, with the remainder being copper and unavoidable impurities, wherein the diameter of the electrical properties testing wire is 0.2 mm or less, the ratio of the Vickers hardness of the central part to the Vickers hardness of the outer part in the cross-section of the electrical properties testing wire is in the range of 0.90 to 1.10, and both the Vickers hardness of the central part and the Vickers hardness of the outer part are 250 HV or higher.

2. An electrical properties testing wire according to claim 1, characterized in that the silver content in the copper alloy is in the range of 3 to 15% by mass.

3. An insulated electric wire comprising: an electrical characteristic test wire according to claim 1 or claim 2; and an insulating coating covering the electrical characteristic test wire.

4. A probe card comprising: a probe card body including a plurality of probe pins; and a plurality of lead wires connected to each of the plurality of probe pins, wherein at least a portion of the plurality of probe pins and the plurality of lead wires are the electrical characteristic testing conductors described in claim 1 or claim 2, or the insulated wires described in claim 3.

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