Contact probe

Abstract

To provide a contact probe with an insulating coating film which is resistant to crazing and cracking, the contact probe to be mounted on a probe unit used mainly for continuity tests of electronic components and substrates or the like.SOLUTION: A contact probe 1 comprises: a body part including an insulating coating film 3 on an outer periphery of a pin-shaped metal conductor 2; and ends 2a, 2b without the insulating coating film 3 on both ends of the metal conductor 2. The insulating coating film 3 includes at least a first insulating coating film 4a made of a modified polyester resin provided on the metal conductor 2, and a second insulating coating film 4b made of a polyester resin or a polyesterimide resin provided on the first insulating coating film 4a. A content ratio of unreacted isocyanate compound in the first insulating coating film is 15-45% per 100 g of the modified polyester resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention mainly relates to a contact probe attached to a probe unit used for conduction inspection of electronic components, substrates, and the like.

Background Art

[0002] In recent years, various circuit boards such as high-density mounting boards used in mobile phones and the like, or IC package boards such as BGA (Ball Grid Array) and CSP (Chip Size Package) incorporated in personal computers and the like have been widely used. Such circuit boards are subjected to, for example, measurement of DC resistance values and conduction inspection in the processes before and after mounting, and the quality of their electrical characteristics is inspected. The inspection of the quality of electrical characteristics is performed using a jig for an inspection device (hereinafter referred to as a "probe unit") connected to an inspection device that measures electrical characteristics. For example, it is performed by bringing the tip of a pin-shaped contact probe (also referred to as a probe needle) attached to the probe unit into contact with an electrode of the circuit board (hereinafter also referred to as a "measurement object") (Patent Document 1). A plurality of such contact probes to several thousand are attached to the probe unit, and during the inspection of electrical characteristics, the probe unit is moved up and down, and contact with the electrode of the circuit board is made by utilizing the elastic force of the contact probe.

[0003] Regarding contact probes, for example, Patent Document 2 proposes a probe needle in which an increase in contact resistance value is unlikely to occur even when the contact between the probe needle and the electrode of the measurement object is repeated. This probe needle is provided with a metal plating layer so as to cover the surface of the metal substrate. Further, Patent Document 3 uses polyurethane resin, nylon resin, polyester resin, epoxy resin, polyesterimide resin, polyamide resin, and polyamideimide resin as insulating coatings for coating the probe needle.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-131334 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-241362 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-322369 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] When an insulating film coated on a contact probe is formed of a polyester resin or a polyesterimide resin, residual stress generated during the film formation process (specifically, film formation while applying straightening correction and twisting) and hydrolysis generated through the cleaning process may cause crazing (fine cracks) and cracks (chipping) in the insulating film. When crazing and cracks occur in the insulating film, there is a possibility of short circuit between contact probes. As a countermeasure against crazing, heat treatment is generally performed. However, by performing heat treatment, the color of the insulating film changes due to heat and the heat treatment takes time, which tends to cause problems in terms of quality and cost.

[0006] Examples of resin materials that are less likely to cause crazing due to hydrolysis include urethane resins (including polyurethane resins) and polyester resins. However, since the heat resistance temperature of urethane resins is 130°C, the heat resistance temperature is lower than that of polyester resins (heat resistance temperature: 155°C), and depending on the conduction inspection conditions of electronic components and substrates, etc., the use temperature range may become narrow and it may not be possible to use them. On the other hand, polyamide resins and polyamideimide resins with high heat resistance temperatures have high viscosities, so when coating a fine-diameter contact probe, it may not be possible to coat the film well. In addition, insulating films using nylon resins or epoxy resins have high hardness and the surface is likely to be roughened, so the guide holes of the probe unit may be shaved.

[0007] The present invention has been made to solve the above problems, and its object is to provide a contact probe having an insulating film in which crazing and cracking are less likely to occur, which is mainly mounted on a probe unit used for conduction inspection of electronic components, substrates, etc.

Means for Solving the Problems

[0008] The contact probe according to the present invention is a contact probe having a body portion with an insulating film on the outer periphery of a pin-shaped metal conductor and end portions without the insulating film at both ends of the metal conductor, wherein the insulating film has at least a first insulating film made of a modified polyester resin provided on the metal conductor and a second insulating film made of a polyester resin or a polyesterimide resin provided on the first insulating film, and the content ratio of the unreacted isocyanate compound in the first insulating film is 15 to 45% by mass ratio with respect to 100 g of the modified polyester resin.

[0009] According to this invention, the first insulating film made of the modified polyester resin provided on the metal conductor is hardly hydrolyzed, so that the occurrence of crazing and cracking of the insulating film can be suppressed, and it can be used even under inspection conditions with a high heat-resistant temperature.

[0010] In the contact probe according to the present invention, the modified polyester resin is formed of a modified polyesterimide resin and an isocyanate compound. According to this invention, since the modified polyester resin contains an isocyanate compound, the isocyanate compound reacts with moisture to suppress the hydrolysis of the insulating film, so that the hydrolysis of the insulating film, which has been a problem in the past, can be suppressed.

[0011] In the contact probe according to the present invention, it is preferable that the thickness of the first insulating film is in the range of 0.4 to 2 μm and the thickness of the second insulating film is in the range of 1 to 30 μm.

[0012] In the contact probe according to the present invention, the metal conductor is any one selected from tungsten, rhenium tungsten, beryllium copper, palladium alloy, and copper silver alloy, and preferably has a conductor diameter in the range of 8 to 180 μm.

Effect of the Invention

[0013] According to the contact probe of the present invention, it is possible to provide a contact probe having an insulating film in which crazing and cracking are less likely to occur. In particular, the first insulating film made of a modified polyester resin provided on the metal conductor is less likely to be hydrolyzed, so that the occurrence of crazing and cracking of the insulating film can be suppressed, and it can be used even under inspection conditions with a high heat-resistant temperature.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0015] Hereinafter, the contact probe according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments.

[0016] [Contact Probe] As shown in FIGS. 1 and 2, the contact probe 1 according to the present invention has a body portion having an insulating film 3 on the outer periphery of a pin-shaped metal conductor 2, and end portions 2a and 2b having no insulating film 3 at both ends of the metal conductor 2. In the contact probe 1, the insulating film 3 includes at least a first insulating film 4a made of a modified polyester resin provided on the metal conductor 2 and a second insulating film 4b made of a polyester resin or a polyesterimide resin provided on the first insulating film 4a, and the content ratio of the unreacted isocyanate compound in the first insulating film is 15 to 45% by mass with respect to 100 g of the modified polyester resin. This is the gist of the invention.

[0017] In this invention, since the first insulating film 4a made of the modified polyester resin provided on the metal conductor 2 is hardly hydrolyzed, it is possible to suppress the occurrence of crazing and cracks in the insulating film 3, and it can be used even under inspection conditions with a high heat-resistant temperature, which has an advantageous effect.

[0018] In FIG. 2, the end portion 2a is the end portion of the metal conductor 2 on the "tip" side that is arranged on the side of the object to be measured and contacts the electrode 12 of the object to be measured 11 shown in FIG. 3, and the end portion 2b is the end portion of the metal conductor 2 on the "rear end" side that is arranged on the inspection device side and contacts the lead wire 50 of the inspection device (not shown). Further, the end portion 3a (also referred to as the insulating film end portion 3a) is the processed end portion of the insulating film 3 on the tip side, and the end portion 3b (also referred to as the insulating film end portion 3b) is the processed end portion of the insulating film 3 on the rear end side. In the present application, the single end portion refers to a specific end portion of the contact probe 1 of the present invention, and the both end portions refer to the end portions on both sides of the contact probe 1 of the present invention. In the example of FIG. 2, the metal conductor 2 on the tip side (end portion 2a side) of the contact probe 1 has an exposed portion where the insulating film 3 is not provided with a predetermined length, and the metal conductor 2 on the rear end side (end portion 2b side) has hardly any exposed portion where the insulating film 3 is not provided. However, the rear end side (end portion 2b side) may be made to have a predetermined length of the exposed portion of the metal conductor 2 in the same manner as the tip side, or may have a different length.

[0019] Each component will be described.

[0020] <Metal Conductor> The metal conductor 2 is a pin-shaped conductor processed to a predetermined length, and is formed by cutting a metal wire (also referred to as a "metal spring wire") having high conductivity and a high elastic modulus. Examples of the metal used for the metal conductor 2 include metals having a wide elastic range, and any one selected from, for example, tungsten, rhenium tungsten, beryllium copper, palladium alloy, copper-silver alloy, etc. can be preferably used.

[0021] The metal conductor 2 is usually subjected to plastic working such as cold or hot wire drawing until the above metal becomes a linear conductor of a predetermined diameter. The outer diameter of the metal conductor 2 can be arbitrarily selected within the range of 8 to 180 μm, preferably within the range of 15 to 90 μm, according to the interval between adjacent contact probes 1 in the probe unit 10 (see FIG. 3) due to the recent requirement for narrow pitch.

[0022] From the viewpoint of facilitating the attachment of the contact probe 1 to the probe unit 10 and preventing the movement of the contact probe 1 from being hindered by the tip 2a of the contact probe 1 being caught in the guide hole of the guide plate 20 during the use of the probe unit 10, it is preferable that the straightness of the metal conductor 2 is high. Specifically, it is preferable that the straightness has a curvature radius R of 1000 mm or more. The metal conductor 2 with high straightness is usually performed by pre-straightening the long metal wire before the insulating coating 3 is provided. The straightening process here is performed by, for example, a rotary die type straightening device.

[0023] The shape of the end 2a on the tip side and / or the end 2b on the rear end side of the metal conductor 2, although not shown in the figure, can be any one selected from a hemispherical shape, a conical shape, a conical shape having a hemispherical shape at the tip, a conical shape having a flat shape at the tip, etc. The "hemispherical shape" and "conical shape" referred to here include accurate hemispheres and cones, but also include approximate cones and approximate hemispheres.

[0024] At the end portions 2a and 2b of the metal conductor 2, a plating layer may be provided on the end portions 2a and 2b in order to suppress an increase in the contact resistance value between the metal conductor 2 and the electrode 12 of the object to be measured 11 or the lead wire 50 of the inspection apparatus. Examples of the metal for forming the plating layer include metals such as nickel, gold, and rhodium, and alloys such as gold alloys. The plating layer may be a single layer or a multilayer. As the multilayer plating layer, preferably, a gold plating layer is formed on a nickel plating layer. The plating layer is usually formed after cutting the metal conductor 2 on which the insulating film 3 is formed, and then performing the peeling process of the insulating film 3 and the end portion process of the metal conductor 2. The thickness of the plating layer is not particularly limited, but is preferably in the range of, for example, 1 to 5 μm.

[0025] <Insulating film> As shown in FIG. 1, the insulating film 3 has at least a first insulating film 4a provided on the metal conductor 2 and a second insulating film 4b provided on the first insulating film 4a. This insulating film 3 basically acts to prevent contact between contact probes when inspecting the electrical characteristics of the object to be measured 11 provided on the metal conductor 2 and prevent short circuits. Generally, the insulating film 3 is selected from polyurethane resin, polyester resin, polyesterimide resin, polyamideimide resin, polyimide resin, etc. In the present invention, the first insulating film 4a constituting the insulating film 3 is made of a modified polyester resin, and the second insulating film 4b is made of a polyester resin or a polyesterimide resin.

[0026] The modified polyester resin constituting the first insulating film 4a is preferably formed from a modified polyesterimide resin and an isocyanate compound. In the insulating film 3 made of the modified polyester resin thus formed, unreacted isocyanate compound is present. The content ratio of such unreacted isocyanate compound is 15 to 45% by mass based on 100 g of the modified polyester resin. The presence of the unreacted isocyanate compound within such a range in the modified polyester resin has the role of reacting with the moisture adhering to the metal conductor 2 after the cleaning step and the moisture remaining after the plating step to form a urethane bond. As a result, the moisture that hydrolyzes the modified polyester resin does not exist or becomes extremely small, so that it is possible to prevent the conventional problem of hydrolysis of the insulating film (hydrolysis occurs in the cleaning for contamination removal and the plating step). Such suppression of hydrolysis can suppress the occurrence of crazing and cracks in the insulating film and has the advantageous effect that it can be used even under high heat resistance temperature inspection conditions.

[0027] The content ratio of the unreacted isocyanate compound present in the insulating film can be measured from the result of quantifying the unreacted isocyanate groups by the infrared total reflection absorption spectrometry. The amount of isocyanate can be measured by the measuring method of JIS K 6806. If the content ratio of the unreacted isocyanate compound is less than 15% by mass, crazing and cracks may occur in the insulating film due to hydrolysis. On the other hand, if the content ratio of the unreacted isocyanate compound exceeds 45% by mass, the heat resistance may decrease. In order to make the content ratio of the unreacted isocyanate compound 15 to 45% by mass based on 100 g of the modified polyester resin, it can be made to fall within the above range by adjusting the blending ratio of the polyester resin and the isocyanate compound when formulating the modified polyester resin raw material.

[0028] The method using the infrared total reflection absorption spectrometry is a method for quantifying isocyanate groups in an insulating film by the Siggia-Hanna method, which is a chemical analysis method utilizing the reaction between an amine and an isocyanate. In this case, the insulating film is peeled off, and an anhydrous dioxane solution of η-butylamine is added thereto to react with the isocyanate groups in the insulating film. By using the infrared total reflection absorption spectrum, the characteristic absorptions of the isocyanate group and the methyl group at 2260 cm -1 and 2950 cm -1 can be directly measured from the surface of the insulating film. The amount of unreacted isocyanate groups present in the insulating film can be obtained more quickly from the absorbance ratio by using a calibration curve between the amount of isocyanate determined by the Siggia-Hanna method and the absorbance ratio ANCO / ACH2 of 2260 cm -1 and 2950 cm -1 .

[0029] The first insulating film 4a preferably has a thickness in the range of 0.4 to 2 μm. By setting it within this range, hydrolysis of the insulating film can be effectively suppressed, and a decrease in heat resistance can also be suppressed. When the thickness of the first insulating film 4a is less than 0.4 μm, it is too thin and film formation of the insulating film 4a becomes difficult, or the absolute amount of the unreacted isocyanate compound that suppresses hydrolysis is too small to react completely with moisture, and suppression of hydrolysis of the insulating film may be insufficient. When the thickness of the first insulating film 4a exceeds 2 μm, the first insulating film 4a becomes thick and the content ratio of the unreacted isocyanate compound increases, and heat resistance may not be obtained. Note that the isocyanate compound can be said to be a urethane substrate.

[0030] The polyester resin or polyesterimide resin constituting the second insulating film 4b has good heat resistance and is preferably applied. In addition, such resin materials also have the advantage of good compatibility with the modified polyester resin constituting the first insulating film 4a and excellent adhesion. The second insulating film 4b preferably has a thickness in the range of 1 to 30 μm.

[0031] Note that the first insulating film 4a is preferably provided directly on the metal conductor 2 in order to make it difficult to change the color of the insulating film 3 composed of the first insulating film 4a and the second insulating film 4b and to improve the adhesion. The phrase "at least has" means that third and fourth insulating films other than the first insulating film 4a and the second insulating film 4b may be provided, but considering cost and other factors, it is preferably composed of two layers, namely the first insulating film 4a and the second insulating film 4b.

[0032] The total thickness of the insulating film 3 composed of the first insulating film 4a and the second insulating film 4b is arbitrarily set in consideration of the type and outer diameter of the metal conductor 2, and further considering how much strength and withstand voltage to give to the final contact probe 1. Additionally, it is set based on factors such as the thickness that ensures the end face 3a on the side of the object to be measured 11 shown in FIG. 3 abuts against the guide hole of the lower guide plate 20 and the probe 1 does not fall through the guide hole. However, due to the recent requirements for smaller diameters and narrower pitches of contact probes, it is preferably within the range of 2 to 15 μm, more preferably within the range of 3 to 14 μm.

[0033] (Inspection method for electrical characteristics using a contact probe) Next, an inspection method for electrical characteristics using the contact probe according to the present invention described above will be explained. FIG. 3 is a schematic cross-sectional view for explaining a method of inspecting the electrical characteristics of an object to be measured using a probe unit equipped with the contact probe according to the present invention. It goes without saying that the inspection method here is an example and is not limited to the illustrated device configuration.

[0034] The contact probe 1 according to the present invention is mounted on a probe unit 10 and used for inspecting the quality of the electrical characteristics of a measurement object 11 such as a circuit board. As shown in FIG. 3, the probe unit 10 includes a plurality of to several thousand contact probes 1, a guide plate 20 for guiding the contact probes 1 to the electrodes 12 of the measurement object 11, and a guide plate 30 for guiding the contact probes 1 to the lead wires 50 of the inspection device. The guide plate 30 on the inspection device side has a guide hole slightly larger than the outer diameter of the contact probe 1, and the guide hole guides the metal conductors 2 of the individual contact probes 1 to the lead wires 50. In the probe unit 10 in the form shown in FIG. 3, the guide plate 20 on the measurement object side has a guide hole slightly larger than the diameter of the metal conductor 2, and the guide hole guides the metal conductors 2 of the individual contact probes 1 to the electrodes 21.

[0035] When inspecting the electrical characteristics of the measurement object 11, the probe unit 10 and the measurement object 11 are position-controlled so that the contact probes 1 and the electrodes 12 correspond. The inspection of the electrical characteristics is performed by moving the probe unit 10 up and down and pressing the tip 2a of the contact probe 1 against the electrode 12 of the measurement object 11 with a predetermined pressure upward or downward using the elastic force of the contact probe 1. At this time, the rear end 2b of the contact probe 1 contacts the lead wire 50, and the electrical signal from the measurement object 11 is sent to an inspection device (not shown) through the lead wire 50. In FIG. 3, reference numeral 40 indicates a holding plate for the lead wire. Such a contact probe 1 is inserted into a guide hole provided in at least one upper guide plate 30 and then inserted into a guide hole provided in at least one lower guide plate 20.

Example

[0036] Hereinafter, the present invention will be described based on examples and comparative examples. Note that the present invention is not limited thereby.

[0037] (Example 1) As the metal conductor 2, a long rhenium tungsten wire (outer diameter 0.035 mm) was used. As shown in Fig. 1, the insulating coating 3 was formed by laminating a first insulating coating 4a with a thickness of 1.5 μm and a second insulating coating 4b with a thickness of 6 μm in order from the metal conductor side. As the paint for the first insulating coating 4a, a modified polyester resin paint (manufactured by Tohto Paint Co., Ltd., trade name: TSF4 series) was used. As the paint for the second insulating coating 4b, a polyester resin paint was used. At this time, the modified polyester resin paint for forming the first insulating coating 4a contains a modified polyester imide resin and an isocyanate compound, and the modified polyester resin coating after film formation was prepared by formulating the modified polyester resin paint so that the content ratio of the unreacted isocyanate compound is 30% by mass with respect to 100 g of the modified polyester resin. The content ratio of the unreacted isocyanate compound is the result confirmed by the infrared total reflection absorption spectrometry.

[0038] First, the contact probe 1 washes the wire made of the above-mentioned rhenium tungsten wire fed out from a wire supply device such as a bobbin, and then applies and bakes the above-mentioned paint for the first insulating coating in the first paint tank to form a first insulating coating 4a with a thickness of 1.5 μm. Subsequently, the paint for the second insulating coating was applied and baked on the first insulating coating 4a to form a second insulating coating 4b with a thickness of 7.5 μm. In the present application, the thicknesses of the first insulating coating 4a, the second insulating coating 4b, and the insulating coating 3 were evaluated as average film thicknesses based on the outer diameter measurement results continuously measured in-line using a LASER SCAN MICROMETER (manufactured by Mitutoyo Corporation, measurement unit model number: LSM-500S, display unit model number: LSM-6200).

[0039] A long contact probe element wire with such an insulating film 3 (total thickness of about 9 μm) formed thereon was cut by a fixed-length cutting machine to cut out a contact probe with an insulating film having a length of 20 mm, and both ends of the contact probe with the insulating film were processed into a hemispherical shape by a grinding device. Then, the insulating film 3 on the tip side was laser-peeled off by a predetermined length, and strong cleaning was performed to remove contaminants generated by the laser processing, and then plating was performed to fabricate the contact probe 1 of Example 1 having the mode shown in FIG. 2.

[0040] [Example 2] The modified polyester resin coating film after film formation was prepared by formulating a modified polyester resin paint so that the content ratio of the unreacted isocyanate compound was 15% by mass ratio with respect to 100 g of the modified polyester resin. Otherwise, in the same manner as in Example 1, the contact probe of Example 2 was fabricated.

[0041] [Example 3] The modified polyester resin coating film after film formation was prepared by formulating a modified polyester resin paint so that the content ratio of the unreacted isocyanate compound was 45% by mass ratio with respect to 100 g of the modified polyester resin. Otherwise, in the same manner as in Example 1, the contact probe of Example 3 was fabricated.

[0042] [Example 4] The thickness of the first insulating film 4a was set to 0.4 μm. Otherwise, in the same manner as in Example 1, the contact probe of Example 4 was fabricated.

[0043] [Example 5] The thickness of the first insulating film 4a was set to 2 μm. Otherwise, in the same manner as in Example 1, the contact probe of Example 5 was fabricated.

[0044] [Example 6] The thickness of the second insulating film 4b was set to 5 μm. Otherwise, in the same manner as in Example 1, the contact probe of Example 6 was fabricated.

[0045] [Example 7] The thickness of the second insulating film 4b was set to 10 μm. Other than that, in the same manner as in Example 1, the contact probe of Example 7 was fabricated.

[0046] [Example 8] The second insulating film 4b having the same thickness was formed using a polyesterimide resin paint. Other than that, in the same manner as in Example 1, the contact probe of Example 8 was fabricated.

[0047] [Comparative Example 1] A contact probe of Comparative Example 1 was fabricated in the same manner as in Example 1, except that the first insulating film 4a was not provided and the thickness of the second insulating film 4b was set to 9 μm.

[0048] [Comparative Example 2] A modified polyester resin paint was prepared such that the content ratio of the unreacted isocyanate compound in the modified polyester resin film after film formation was 13% by mass with respect to 100 g of the modified polyester resin. Other than that, in the same manner as in Example 1, the contact probe of Comparative Example 2 was fabricated.

[0049] [Comparative Example 3] A modified polyester resin paint was prepared such that the content ratio of the unreacted isocyanate compound in the modified polyester resin film after film formation was 47% by mass with respect to 100 g of the modified polyester resin. Other than that, in the same manner as in Example 1, the contact probe of Comparative Example 3 was fabricated.

[0050] [Comparative Example 4] The thickness of the first insulating film 4a was set to 0.2 μm. Other than that, in the same manner as in Example 1, the contact probe of Comparative Example 4 was fabricated.

[0051] [Comparative Example 5] The thickness of the first insulating film 4a was set to 2.5 μm. Other than that, in the same manner as in Example 1, the contact probe of Comparative Example 5 was fabricated.

[0052] [Measurement and Evaluation of Each Property] (Effect of Suppressing Hydrolysis) As the hydrolysis inhibition effect, the presence or absence of crazing (fine cracks) and cracks (chips) was confirmed. Also, the film strength (adhesion) was evaluated. After 2 days had passed since the obtained contact probe was fabricated, the insulating film 3 was observed with an optical microscope. As a result of the observation, it was evaluated based on the presence or absence of the occurrence of crazing or cracks in the insulating film 3. Note that FIG. 4 is a surface photograph of the contact probe obtained in Example 1, and FIG. 5 is a surface photograph of the contact probe obtained in Comparative Example 1. In FIG. 4, there was no occurrence of crazing or cracks, but in FIG. 5, they occurred.

[0053] The strength (adhesion) of the insulating film was evaluated by a peel test (adhesion test) using a precision universal testing machine (manufactured by Shimadzu Corporation, model number: AG-I). Specifically, the tip 2a of each contact probe 1 was passed through a die with a hole diameter of 44 μm (the same diameter as the stopper part of the unit), which is the median value between the conductor diameter of the metal conductor and the overall outer diameter, and the test load when a load was applied from the rear end 2b was detected by the above device, and the obtained values were compared with each other to evaluate the adhesion. The greater the strength, the better the adhesion, and the smaller the strength, the worse the adhesion.

[0054] (Heat resistance) The heat resistance of the insulating film 3 was evaluated. The measurement of the heat resistance was performed by a method of putting the contact probe into a constant temperature bath at 140°C for 30 minutes and measuring the straightness before and after putting it into the constant temperature bath. Those with a change in straightness of less than ±10 μm were evaluated as having heat resistance "yes", and those with a change in straightness of ±10 μm or more were evaluated as having insufficient heat resistance.

[0055] (Dielectric voltage withstand) The dielectric voltage withstand was evaluated based on the results measured under the conditions of the "dielectric breakdown test of JIS C 3003 Enameled Wire Test Method" using an automatic AC dielectric voltage withstand tester (manufactured by Tokyo Seiden Co., Ltd., model number: ITS-20005T.SP). If the dielectric voltage withstand was 1 kV or more, it was rated as "good", and if it was less than 0.5 kV, it was rated as "bad".

[0056] (Color development) The color development was visually evaluated as the "hue" of the insulating film after manufacturing the contact probe. The original hue was defined as "normal", a darker hue as "dark", and a lighter hue as "light".

[0057] [Results] For Examples 1 to 8 and Comparative Examples 1 to 5, the presence or absence of crazing and cracks and the film strength (adhesion) were evaluated as the hydrolysis suppression effects, and the results are shown in Table 1. Also, the heat resistance and withstand voltage were evaluated, and the results are shown in Table 1. The contact probes of Examples 1 to 8 all had good results for all characteristics.

[0058]

Table 1

Explanation of Symbols

[0059] 1 Contact probe 2 Metal conductor 2a End (tip) 2b End (rear end) 3 Insulating film 3a, 3b End (end face) 4a First insulating film 4b Second insulating film 10 Probe unit 11 Object to be measured 12 Electrode 20 Guide plate on the object - to - be - measured side 30 Guide plate on the inspection - device side 40 Holding plate for lead wires 50 Lead wire

Claims

1. In a contact probe having a body portion with an insulating coating on the outer periphery of a pin-shaped metal conductor and end portions without the insulating coating at both ends of the metal conductor, the insulating coating has at least a first insulating coating made of a modified polyester resin provided on the metal conductor and a second insulating coating made of a polyester resin or a polyesterimide resin provided on the first insulating coating, and the content ratio of the unreacted isocyanate compound in the first insulating coating is 15 to 45% by mass with respect to 100 g of the modified polyester resin. A contact probe characterized by this.

2. The contact probe according to claim 1, wherein the modified polyester resin is formed of a modified polyesterimide resin and an isocyanate compound.

3. The contact probe according to claim 1 or 2, wherein the thickness of the first insulating coating is in the range of 0.4 to 2 μm, and the thickness of the second insulating coating is in the range of 1 to 30 μm.

4. The contact probe according to claim 1 or 2, wherein the outer diameter of the metal conductor is in the range of 8 to 180 μm.

5. The contact probe according to claim 1 or 2, wherein the metal conductor is any one selected from tungsten, rhenium tungsten, beryllium copper, palladium alloy, and copper silver alloy.

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