Insulated wire, twisted wire, and probe card

Abstract

An insulated wire 10 according to the present invention comprises: a conductor 12 composed of a Cu-Ag alloy that contains 5-20 mass% Ag, with the remainder being Cu and unavoidable impurities; and an insulating coating film 14 that covers the conductor 12. The wire diameter of the conductor 12 is within the range of 0.01-0.1 mm. The elongation of the insulated wire 14 is less than 3%.

Description

Insulated Wire, Stranded Wire and Probe Cards

[0001] The present invention relates to an insulated wire, a stranded wire, and a probe card.

[0002] When testing the electrical characteristics of an object under test, such as an integrated circuit, a probe card with an array of multiple probe pins is sometimes used. One end of each of the multiple probe pins is brought into contact with a target location on the object under test, and the other end is connected to a testing device via lead wires. The testing device can test the electrical characteristics of the object under test by moving at least one of the probe card and the object under test to bring one end of each of the multiple probe pins into contact with a target location on the object under test. The lead wires are often insulated wires (also called enameled wires) that have a conductor made of copper or a copper alloy and a resin insulating coating that covers the conductor.

[0003] For example, Patent Document 1 discloses a lead wire used in such an inspection device. The lead wire described in Patent Document 1 is characterized by having a conductor portion made of a copper alloy wire having a conductor diameter in the range of 0.018 to 0.18 mm, a tensile strength in the range of 700 to 1500 MPa, a micro Vickers hardness in the range of 200 to 350 HV (0.04), and a conductivity in the range of 60 to 85% IACS. Patent Document 1 explains that this lead wire may further have an insulating coating that covers the conductor portion. Examples of resins that can be used to form the insulating coating include polyurethane, nylon, and polyester.

[0004] Japanese Patent Application Laid-Open No. 2019-143981

[0005] As integrated circuits continue to become increasingly miniaturized in recent years, the diameters of probe pins and insulated wires (lead wires) are also becoming thinner. Wiring between probe cards and testing equipment is often performed manually. In this process, thin insulated wires are prone to stretching due to the tension applied during wiring. Stretching of the insulated wire can cause crazing in the insulation coating. Crazing can cause localized insulation defects in the insulated wires connecting the probe card and testing equipment, resulting in short circuits between the insulated wires during testing, preventing proper testing. While it is possible to check for breaks after wiring, it is difficult to determine whether crazing has occurred.

[0006] An object of the present invention is to provide an insulated wire that can suppress short circuits caused by crazing while maintaining wiring workability, and a stranded wire and a probe card that include the insulated wire.

[0007] The insulated wire for solving the above-mentioned problems has a conductor made of a Cu-Ag alloy containing 5 to 20 mass% Ag and the remainder being Cu and unavoidable impurities, and an insulating coating covering the conductor, wherein the wire diameter of the conductor is within a range of 0.01 to 0.1 mm, and the elongation of the insulated wire is less than 3%.

[0008] A stranded wire for solving the above problem includes the above insulated wire.

[0009] A probe card for solving the above problem has a probe card body including a plurality of probe pins, and a plurality of lead wires respectively connected to the plurality of probe pins, and is characterized in that at least some of the plurality of lead wires are the above-mentioned insulated wire or the above-mentioned twisted wire.

[0010] According to the present invention, it is possible to provide an insulated wire that can suppress short circuits caused by crazing while maintaining wiring workability, as well as a stranded wire and a probe card that include the insulated wire.

[0011] Fig. 1 is a cross-sectional view of an insulated wire according to an embodiment. Fig. 2 is a cross-sectional view of a stranded wire according to an embodiment. Figs. 3A and 3B are cross-sectional views showing a configuration around a probe card of an inspection device. Fig. 4 is a flowchart showing an example of a method for manufacturing an insulated wire according to an embodiment.

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In numerical ranges described in stages in this specification, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.

[0013] (Configuration of Insulated Wire) Fig. 1 is a cross-sectional view of an insulated wire 10 according to an embodiment of the present invention. As shown in Fig. 1, the insulated wire 10 has a conductor 12 and an insulating coating 14.

[0014] The conductor 12 is a Cu-Ag alloy wire containing a predetermined amount of Ag (silver) with the remainder being Cu (copper) and unavoidable impurities. For example, the conductor 12 has a structure in which a Cu-based solid solution phase, a Cu-Ag eutectic phase, and an Ag precipitate phase are stretched into a fibrous form by cold working. The cross-sectional shape of the conductor 12 is not particularly limited, but is usually circular. The cross-sectional shape of the conductor 12 may also be elliptical, rectangular, or the like.

[0015] The wire diameter of the conductor 12 is preferably within the range of 0.010 to 0.100 mm, more preferably within the range of 0.013 to 0.070 mm, and particularly preferably within the range of 0.015 to 0.050 mm. By setting the wire diameter of the conductor 12 to 0.100 mm or less, it can be used for wiring of probe cards in which fine probe pins are densely arranged to accommodate the miniaturization of test locations on test objects such as integrated circuits. By setting the wire diameter of the conductor 12 to 0.010 mm or more, it is possible to reduce the occurrence of breaks during wiring. Note that if the cross-sectional shape of the conductor 12 is not circular, the wire diameter of the conductor 12 refers to the circle-equivalent diameter.

[0016] The Ag content in the conductor 12 is preferably within the range of 5 to 20% by mass, more preferably within the range of 8 to 17% by mass, and particularly preferably within the range of 10 to 15% by mass. For example, the Ag content in the conductor 12 may be within the range of 10 to 20% by mass, or may be greater than 10% by mass and less than or equal to 20% by mass. By setting the Ag content to 5% or greater, the increase in elongation of the insulated wire 10 can be suppressed. Furthermore, by setting the Ag content to 5% or greater, the breaking load of the insulated wire 10 can be increased. As a result, even when the wire diameter of the conductor 12 is small, the insulated wire 10 is less likely to break, improving the wiring workability of the insulated wire 10. Although the Ag content may exceed 20% by mass, this results in a significant increase in cost relative to the effect. Furthermore, when the wire diameter of the conductor 12 is relatively large (e.g., 0.05 mm), the Ag content may be approximately 3 to 5% by mass.

[0017] The insulating coating 14 is a resin coating that covers the conductor 12. The type of resin constituting the insulating coating 14 is not particularly limited, and examples include polyvinyl acetal (e.g., polyvinyl formal, polyvinyl butyral, etc.), polyurethane, nylon, polyester, epoxy resin, polyesterimide, polyamide, and polyamideimide. The insulating coating 14 preferably contains one or more resins selected from the group consisting of polyvinyl formal, polyurethane, polyester, and polyesterimide. For example, the insulated wire 10 according to this embodiment may be a polyvinyl formal wire (PVF), a polyurethane wire (UEW), a polyester wire (PEW), or a polyesterimide wire (EIW). Insulating coatings 14 containing polyvinyl formal, polyurethane, polyester, and / or polyesterimide are prone to crazing when elongated by 3 to 5%, but rarely crazing occurs even when elongated by less than 3%. From the viewpoint of solderability, polyurethane wires (UEW) are preferred. The insulating coating 14 may contain other components in addition to the above resins. Examples of other ingredients include pigments, dyes, antioxidants, and various additives.

[0018] The thickness of the insulating film 14 is not particularly limited and may be appropriately selected depending on the configuration of the probe card, etc., but is, for example, 2 μm to 10 μm. The insulating film 14 may have a single-layer structure or a layer structure of two or more layers.

[0019] One feature of the insulated wire 10 according to this embodiment is that the elongation of the insulated wire 10 is less than 3%. Here, the elongation of the insulated wire 10 refers to the percentage (%) of increase in the length of the insulated wire 10 when the insulated wire 10 is stretched until the conductor 12 breaks, as measured in accordance with JIS C 3216-3:2011. The tensile test is performed at a tensile speed (elongation rate: 5±1 mm / sec) of 25 mm / min. As mentioned above, crazing is likely to occur when the insulating coating 14 stretches by 3 to 5%. Therefore, if the elongation of the insulated wire 10 is less than 3%, the conductor 12 will break before crazing occurs. For example, if tension sufficient to cause crazing is applied to the insulated wire 10 during wiring to a probe card or the like, not only will crazing occur but the conductor 12 will also break. While it is difficult to determine whether crazing has occurred after wiring, it is easy to determine whether a break has occurred. Therefore, if a break is found, the wiring can be rewired with a new insulated wire, thereby preventing a short circuit caused by the crazing phenomenon.

[0020] There is no particular limitation on the method for making the elongation of the insulated wire 10 less than 3%. For example, by controlling the annealing temperature of the conductor 12 and / or the baking temperature of the insulating coating 14 during the manufacture of the insulated wire 10, it is possible to suppress softening of the conductor 12 while maintaining the breakdown voltage, thereby making the elongation of the insulated wire 10 less than 3%. More specifically, it is possible to make the elongation of the insulated wire 10 less than 3% by setting the annealing temperature of the conductor 12 and / or the baking temperature of the insulating coating 14 to a somewhat lower value.

[0021] The breaking load of the insulated wire 10 is not particularly limited, but is preferably 0.2 N or more from the viewpoint of reducing the number of breaks in the wiring. The breaking load of the insulated wire 10 means the tensile force (N) at the time of breakage of the conductor 12 when the insulated wire 10 is elongated until the conductor 12 breaks, as measured in accordance with JIS C 3216-3:2011. However, the tensile speed (elongation speed: 5±1 mm / sec) during the tensile test is 25 mm / min.

[0022] The insulated wire 10 according to the present embodiment can be used for various purposes. For example, the insulated wire 10 can be used for wiring various devices. Specifically, as will be described later, the insulated wire 10 can be suitably used for wiring a probe card.

[0023] (Stranded Wire) The insulated wire 10 according to the present embodiment may be used in the form of a twisted wire (also referred to as a Litz wire). FIG. 2 is a cross-sectional view of a twisted wire 20 according to an embodiment of the present invention. As shown in FIG. 2, the twisted wire 20 includes a plurality of insulated wires 10. The twisted wire 20 may be a primary twisted wire formed by twisting a plurality of insulated wires 10 together, or may be a secondary twisted wire formed by further twisting the primary twisted wires together. The number, arrangement, twisting direction, etc. of the insulated wires 10 are not particularly limited. The twisted wire 20 may also be covered with an outer sheath.

[0024] (Probe Card) Figures 3A and 3B are cross-sectional views showing the configuration of a probe card 30 and its surroundings in an inspection device. As shown in Figures 3A and 3B, the probe card 30 has a probe card main body 32 and lead wires. Figure 3A shows an example in which the insulated wire 10 according to this embodiment is used as the lead wire, and Figure 3B shows an example in which the twisted wire 20 according to this embodiment is used as the lead wire. Figures 3A and 3B show how one end of a probe pin 34 of the probe card main body 32 is brought into contact with an inspection target portion 42 of an inspection target 40 (e.g., an integrated circuit) to inspect the electrical characteristics of the inspection target 40.

[0025] The probe card body 32 has a plurality of probe pins 34 , a first guide plate 36 , and a second guide plate 38 .

[0026] The probe pin 34 is a rod-shaped member having one end (the lower end in FIGS. 3A and 3B ) and the other end (the upper end in FIGS. 3A and 3B ) electrically connected. By moving at least one of the probe card body 32 and the test object 40, one end of the probe pin 34 is brought into contact with the test target location 42 of the test object 40. The other end of the probe pin 34 is connected to a test device (not shown) via a lead wire (insulated electric wire 10 or stranded wire 20). The configuration of the probe pin 34 is not particularly limited as long as it can electrically connect the test target location 42 and the test device. The probe pin 34 may be made solely of a conductor such as a metal, or may be made of a combination of a conductor and an insulator. The surface of the probe pin 34, except for the area that contacts the test target location 42 and the area that is connected to the lead wire (insulated electric wire 10 or stranded wire 20), may be covered with an insulating coating or the like. Furthermore, since the probe pin 34 is pressed against the inspection target portion 42, it is preferable that the probe pin 34 has elasticity. For example, the probe pin 34 may be made of a highly elastic material, or may have an elastic structure including a spring or the like.

[0027] The first guide plate 36 positions one ends of the multiple probe pins 34. The first guide plate 36 has a plurality of through holes, and a probe pin 34 is inserted into each of the through holes. The second guide plate 38 positions the other ends of the multiple probe pins 34. The second guide plate 38 also has a plurality of through holes, and a probe pin 34 is inserted into each of the through holes. The first guide plate 36 and the second guide plate 38 are preferably made of an insulator having the necessary strength. The first guide plate 36 and the second guide plate 38 may be integral rather than separate members. There may also be no space between the first guide plate 36 and the second guide plate 38. In other words, a single thick guide plate may have a plurality of through holes, and the probe pins 34 may be inserted into each of the through holes, thereby simultaneously positioning one end and the other end of the multiple probe pins 34.

[0028] The plurality of lead wires are respectively connected to the plurality of probe pins 34 of the probe card body 32. Meanwhile, the plurality of lead wires are also respectively connected to an inspection device (not shown). That is, the plurality of lead wires connect the plurality of probe pins 34 of the probe card body 32 to the inspection device. At least some of the plurality of lead wires are insulated wires 10 (see FIG. 3A) or stranded wires 20 (see FIG. 3B). It is preferable that the plurality of lead wires (insulated wires 10 or stranded wires 20) are fixed to the corresponding probe pins 34. In the example shown in FIGS. 3A and 3B, the lead wires (insulated wires 10 or stranded wires 20) are fixed to the probe pins 34 by soldering.

[0029] There are no particular limitations on the inspection object 40. Examples of the inspection object 40 include electronic components such as integrated circuits, semiconductor chips, and connectors, and wiring boards such as printed circuit boards, flexible boards, multilayer boards, and semiconductor package boards.

[0030] (Method of Manufacturing Insulated Wire) There is no particular limitation on the method of manufacturing the insulated wire 10 according to the present embodiment. For example, the insulated wire 10 can be manufactured by the following procedure.

[0031] Fig. 4 is a flowchart showing an example of a method for manufacturing the insulated wire 10. In the example shown in Fig. 4, the insulated wire 10 is manufactured by performing a casting step S1, a heat treatment step S2, a wire drawing step S3, a varnish application step S4, and a baking step S5 in this order.

[0032] In the casting step S1, a molten metal containing 5 to 20% by mass of Ag, with the remainder consisting of Cu and unavoidable impurities, is poured into a mold and cooled to room temperature within 0.5 to 60 minutes to cast a rod having a certain diameter. Specifically, the raw material is first melted at 1000 to 1400°C to prepare a composition (molten metal) containing 5 to 20% by mass of Ag, with the remainder consisting of Cu and unavoidable impurities. This melt (molten metal) is then poured into a mold and cooled to room temperature within 0.5 to 60 minutes to cast a rod having a Cu-Ag eutectic phase formed in a network pattern in a Cu matrix. The raw material is not particularly limited as long as it contains 5 to 20% by mass of Ag and the remainder consisting of Cu and unavoidable impurities after melting. The raw material may be composed of Ag and Cu as separate simple substances before melting, or it may be an integrated Ag and Cu compound.

[0033] In the heat treatment step S2, the rod material is heated in a vacuum or inert gas atmosphere at 300 to 700°C for 1 to 60 hours to precipitate Ag dissolved in the Cu base as an Ag precipitate phase. The heat treatment in this step induces the precipitation of the Ag precipitate phase, which mainly contributes to improving the tensile strength and electrical conductivity of the Cu-Ag alloy wire. As the inert gas, N ２ Alternatively, Ar can be used. The heat treatment step S2 may be performed only once or multiple times. When the heat treatment step S2 and the wire drawing step S3 are performed multiple times alternately, the second and subsequent heat treatment steps are appropriately adjusted depending on the characteristics of the conductor 12 before the baking step S5.

[0034] In the wire-drawing step S3, the heat-treated rod is drawn to produce the conductor 12 (Cu—Ag alloy wire). The wire-drawing step S3 may be performed once or multiple times. For example, the heat-treatment step S2 and the wire-drawing step S3 may be performed alternately multiple times.

[0035] In the application step S4, a varnish for forming the insulating coating 14 is applied to the conductor 12. The composition of the varnish is not particularly limited and can be selected appropriately. For example, the varnish includes one or more resins selected from the group consisting of polyvinyl formal, polyurethane, polyester, and polyesterimide, and a solvent. The varnish may also contain other components, such as an antioxidant, as needed. Examples of solvents include aprotic polar organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone. One type of solvent may be used, or two or more types may be used. The varnish can be applied using a known method. An example of a method for applying the varnish includes inserting the conductor 12 into a die having an opening slightly larger than the cross-section of the conductor 12 and roughly similar in shape to the cross-section of the conductor 12, and applying the varnish within the die while moving the conductor 12 in one direction.

[0036] In the baking step S5, the conductor 12 is heated in an annealing furnace, and then the varnish applied to the conductor 12 is baked in the baking furnace. Baking of the varnish can be performed using a known method. For example, the varnish-coated conductor 12 may be heated in a vertical furnace or a horizontal furnace. The annealing temperature is preferably in the range of 50 to 500°C to prevent excessive softening of the conductor 12. The annealing time is appropriately selected depending on the elongation and breaking load of the insulated wire 10. The baking temperature is appropriately selected depending on the composition of the varnish so that the insulating coating 14 can be properly formed, but a relatively low temperature is preferable to prevent softening of the conductor 12. For example, the baking temperature is approximately 200 to 400°C. The baking time is appropriately selected depending on the composition of the varnish so that the insulating coating 14 can be properly formed. The thickness of the film formed by one application and baking of the varnish is preferably in the range of 0.1 to 1 μm. Therefore, it is preferable to apply and bake the varnish multiple times (for example, two or more times) (by repeating the application step S4 and the baking step S5) to form the insulating coating 14 of the desired thickness.

[0037] The insulated wire 10 can be manufactured by the above-described procedure.

[0038] (Effects) Insulated wire 10 according to the present embodiment has an elongation of less than 3%, and conductor 12 breaks before crazing occurs when elongated, thereby suppressing short circuits caused by crazing during wiring. Furthermore, insulated wire 10 according to the present embodiment, conductor 12 is made of a Cu—Ag alloy containing 5% by mass or more of Ag, so it does not break even when pulled to a certain extent, and wiring workability is maintained at the same level as that of conventional insulated wires.

[0039] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0040] 1. Manufacturing of insulated wires A raw material containing a predetermined amount of Ag and the remainder Cu was heated at 1000 to 1400°C to prepare a molten metal. The molten metal was poured into a mold and cooled to room temperature within 10 minutes, and rods with a diameter of 11.5 mm were cast. Each rod was composed of a Cu-Ag alloy containing 0 mass%, 3 mass%, 10 mass%, or 15 mass% Ag, with the remainder being Cu and unavoidable impurities. Each rod was then heated in a N ２ The rods were heated at 500°C for 10 hours in a gas atmosphere. Each rod was drawn from a diameter of 11.5 mm to a diameter of 2.2 mm to obtain a wire. ２ The wires were heated and annealed in a gas atmosphere at a wire speed of 100 m / min or 200 m / min and at annealing furnace temperatures of 50°C, 200°C, 300°C, 400°C, 500°C, or 600°C. Each annealed wire was drawn from a diameter of 2.2 mm to a diameter of 0.015 mm or 0.050 mm to obtain wires to be used as conductors for insulated wires.

[0041] The conductor was inserted into a die for applying varnish, and while the conductor was moved in one direction, polyurethane varnish was applied and baked inside the die. The wire speed was 100 m / min or 200 m / min, and the temperature of the baking oven was 300°C. The application of varnish and baking were repeated 2 to 10 times to obtain an insulated electric wire (UEW) with an insulating coating 2 μm (0.002 mm) thick.

[0042] The manufacturing conditions for the 48 types of insulated wires manufactured are shown in Tables 1 and 2.

[0043] 2. Evaluation of Insulated Wires (Tensile Test) A tensile test was performed on the 48 types of insulated wires produced in accordance with JIS C 3216-3:2011, except that the tensile speed (elongation speed: 5±1 mm / sec) was changed to 25 mm / min, and the elongation, tensile strength, and tensile force at break were measured.

[0044] (Pinhole Test) The 48 types of insulated wires manufactured were subjected to a pinhole test in accordance with JIS C 3216-5:2019, except that they were not subjected to heat treatment (125°C ± 3°C, 10 minutes) before the test, and the number of pinholes per unit length was measured. Furthermore, each insulated wire stretched by 4% was also subjected to a pinhole test using the same procedure, and the number of pinholes per unit length was measured. The reason for not performing heat treatment before the test in this pinhole test is to reproduce the situation where insulated wires are typically not subjected to heat treatment after wiring on a probe card or the like.

[0045] (Evaluation of Crazing Resistance) Based on the results of the pinhole test on the insulated wires stretched by 4%, the crazing resistance of each insulated wire was evaluated as follows: ◯: Pass. ◯: The number of pinholes after 4% stretch was 8 or less / m, or the conductor broke before 4% stretch, making it impossible to measure the number of pinholes. ×: The number of pinholes after 4% stretch was 9 or more / m.

[0046] (Evaluation of wiring workability) Each insulated wire was manually wired to a probe card, and the ease of wiring was evaluated as follows: ◎ and ◯ are acceptable. ◎: No breaks occurred. ◯: Although breaks occurred, the wiring work could be completed by replacing the broken insulated wire. ×: Breaks occurred frequently, and the wiring work could not be completed.

[0047] (Lead Wire Evaluation) Based on the evaluation results of the crazing resistance and wiring workability of each insulated wire, the performance of each insulated wire as a lead wire was evaluated as follows: ◯: Excellent in crazing resistance and wiring workability, suitable as a lead wire. ×: Not suitable as a lead wire.

[0048] The test results and evaluation results of the 48 types of insulated wires produced are shown in Tables 3 and 4.

[0049] The results in Tables 3 and 4 show that by setting the Ag concentration of the Cu-Ag alloy constituting the conductor to 5% or more, the conductor is less likely to break, even when the wire diameter is small, and wiring workability can be improved. Furthermore, by setting the elongation of the insulated wire to less than 3%, the conductor breaks before crazing occurs. As mentioned above, while it is difficult to confirm whether crazing occurs after wiring, it is easy to confirm whether a break occurs. Therefore, by rewiring with a new insulated wire when a break is detected, short circuits due to crazing can be prevented. In this example, the elongation of the insulated wire was adjusted by controlling the temperature of the annealing furnace. However, by setting the Ag concentration to more than 10%, it is possible to keep the elongation of the insulated wire to less than 3%, even when the annealing furnace temperature is high (e.g., 500°C). Similar test and evaluation results were obtained when formal (polyvinyl formal) varnish, polyester varnish, or polyesterimide varnish was used instead of polyurethane varnish.

[0050] The insulated wire, stranded wire, and probe card according to the present invention are useful when testing electrical characteristics of an object to be tested, such as an integrated circuit, using a testing device including a probe card. The insulated wire and stranded wire according to the present invention are also useful for wiring in various devices.

[0051] REFERENCE SIGNS LIST 10 insulated wire 12 conductor 14 insulating coating 20 stranded wire 30 probe card 32 probe card body 34 probe pin 36 first guide plate 38 second guide plate 40 inspection object 42 inspection object location

Claims

1. An insulated wire having a conductor made of a Cu-Ag alloy containing 5 to 20 mass% Ag, with the remainder being Cu and unavoidable impurities, and an insulating coating covering the conductor, wherein the conductor has a wire diameter within the range of 0.01 to 0.1 mm, and the elongation of the insulated wire is less than 3%.

2. An insulated wire according to claim 1, wherein the Ag content of the conductor is within the range of 10 to 20 mass %.

3. An insulated wire according to claim 1, wherein the insulating coating contains one or more resins selected from the group consisting of polyvinyl formal, polyurethane, polyester, and polyesterimide.

4. An insulated wire according to claim 1, characterized in that the breaking load of said insulated wire is 0.2 N or more.

5. A stranded wire comprising the insulated wire according to claim 1.

6. A probe card comprising: a probe card body including a plurality of probe pins; and a plurality of lead wires connected to said plurality of probe pins, wherein at least some of said plurality of lead wires are the insulated wires described in any one of claims 1 to 4 or the twisted wires described in claim 5.

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