TWI871484B - Contact probe - Google Patents

Abstract

[Topic] Provide a contact probe that can reliably contact the tip of the probe with the inspection point of the object to be measured without scratching or damaging the inspection point of the object to be measured. [Solution] A contact probe 10 comprises: a body 14 having an insulating film 12 on the outer periphery of a metal conductor 11; and end portions 16 formed at both ends of the metal conductor 11 and not having an insulating film 12, and being bent by applying a load in an axial direction to obtain a contact pressure on a measured object 20 to measure electrical characteristics, wherein the shape of at least the end portion 16 on the side in contact with the measured object 20 is a curved surface, and when the curvature radius of the curved surface is set to R and the diameter of the metal conductor 11 is set to D, R is within a range of greater than 0.5D and less than 5D.

Description

Contact probe

The present invention relates to a contact probe used for inspecting the electrical characteristics of electronic components and substrates.

In recent years, various circuit boards have been used, including high-density mounting boards for smartphones and portable phones, and IC packaging boards such as BGA (Ball Grid Array) and CSP (Chip Size Package) for personal computers. These circuit boards are tested for electrical characteristics such as DC resistance measurement and continuity testing before and after installation.

For example, as shown in Patent Document 1, the inspection of the quality of electrical characteristics is performed using an inspection device jig (hereinafter, sometimes referred to as a probe unit) connected to the inspection device. Specifically, the inspection is performed by making the front end of the pin-shaped contact probe mounted on the front end of the probe unit contact the electrode (hereinafter, sometimes referred to as an inspection point) of the circuit substrate (hereinafter, sometimes referred to as a measured object) as the measurement object.

Patent document 2 states that the shape of the front end portion of the contact probe can be appropriately selected from any of a hemispherical shape, a cone shape, a cone shape with a hemispherical front end, and a cone shape with a flat front end.

Patent document 3 states that the front end of the contact probe has a flat shape. [Prior art document] [Patent document]

Patent document 1: Japanese Patent Publication No. 2002-131334 Patent document 2: Japanese Patent Publication No. 2007-322369 Patent document 3: Japanese Patent Publication No. 2013-024716

[Problems to be solved by the invention]

As described in the aforementioned Patent Documents 1 and 2, if the front end of the contact probe is hemispherical, the front end of the contact probe may slide excessively from the inspection point of the object to be measured, so that the front end of the contact probe does not contact the inspection point, and thus a correct inspection may not be performed.

Furthermore, as described in Patent Document 2, when the shape of the front end of the contact probe is a cone, a cone with a hemispherical front end, or a cone with a flat front end, since the contact area with the inspection point of the object to be measured becomes smaller, it may become difficult to make the front end of the contact probe contact each inspection point for inspection as the electrode spacing has been narrowing in recent years.

Furthermore, as described in Patent Document 3, when the front end of the contact probe is flat, the contact area with the inspection point of the object to be measured can be sufficiently ensured, but since a right-angled edge is generated at the front end of the contact probe, the inspection point may be removed or scratched when the edge contacts the inspection point.

Therefore, the present invention is completed to solve the above-mentioned problem, and its purpose is to provide a contact probe that can make the front end of the contact probe contact the inspection point of the object to be measured reliably and can reduce the damage or scratches caused to the inspection point of the object to be measured. [Means for solving the problem]

According to the contact probe of the present invention, a contact probe comprises: a body having an insulating film on the outer periphery of a needle-shaped metal conductor; and end portions formed at both ends of the metal conductor and not having the insulating film, and being bent by applying a load in the axial direction to obtain a contact pressure on a measured object to measure electrical characteristics, wherein the shape of the end portion of at least the side in contact with the measured object is a curved surface, and when the curvature radius of the curved surface is set to R and the diameter of the metal conductor is set to D, R is within a range of greater than 0.5D and less than 5D. By adopting this structure, the end portion that contacts the object to be measured can be made into a curved surface that is roughly flat, so it will not slide excessively when contacting the inspection point of the object to be measured. In addition, since the edge is not a right angle, it can contact the inspection point surface, protecting the inspection point from being cut or scratched.

In addition, the feature is that the aforementioned curvature radius R can also be greater than D.

In addition, the invention is characterized in that the diameter of the metal conductor can be greater than 8 μm and less than 180 μm. [Effect of the invention]

According to the present invention, a contact probe can be provided which can reliably contact the inspection point of the object to be measured without cutting or scratching the inspection point of the object to be measured.

[Form used to implement the invention]

The following is a detailed description of the implementation form of the contact probe of the present invention based on the drawings. Figure 1 is a schematic top view of the contact probe, and Figure 2 is an explanatory diagram of using the contact probe to perform an inspection of the electrical characteristics of the object to be measured.

The contact probe 10 is composed of a very fine cylindrical (needle-shaped) metal conductor 11 with a circular cross section, and has a body 14 having an insulating film 12 on the outer periphery of the metal conductor 11. Ends 16 without the insulating film 12 are formed at both ends of the metal conductor 11. The contact probe 10 is constructed in such a way that a load is applied in the axial direction to bend it to obtain a contact pressure on the object to be measured to check the electrical characteristics.

(Inspection method of electrical characteristics using contact probe) The use of the contact probe is described based on FIG. 2. In the example shown here, an IC package substrate or the like is used as the object to be measured 20, a plurality of electrodes formed on the surface of the object to be measured 20 are used as inspection points 22, and the end 16 of the contact probe 10 is brought into contact with the inspection points 22.

The jig for inspection, i.e., the probe unit 30, has a plurality of contact probes 10. The probe unit 30 has an upper plate 32 for holding the upper ends of the plurality of contact probes 10, and a lower plate for guiding the lower ends of the contact probes 10, and the upper plate 32 and the lower plate 34 are supported by support columns 36. A guide hole having a diameter slightly larger than the lower end of the contact probe 10 is formed on the lower plate 34, and the lower end of the contact probe 10 can move axially in the guide hole. In addition, a plurality of leads 37 electrically connected to each upper end of the plurality of contact probes 10 are arranged on the upper plate 32. The plurality of leads 37 are connected to a measuring machine (not shown) or a power source (not shown).

As shown in the right figure of FIG. 2 , the probe unit 30 is arranged above the object 20 to be measured so that the lower end of each contact probe 10 is opposite to the position of each inspection point 22 of the object 20 to be measured. Furthermore, the probe unit 30 is lowered so that the lower end of each contact probe 10 contacts the inspection point 22 of the object 20 to be measured, and, as shown in the right figure of FIG. 2 , the probe unit 30 is pressurized from the top to the bottom. Thus, a load is applied along the axial direction of the contact probe 10 to bend the contact probe 10. At this time, the end 16 of the contact probe 10 contacts the inspection point 22 with a predetermined contact pressure formed by the elastic force generated by the bending of the contact probe 10.

(Metal conductor) As the metal conductor 11, a metal wire (also called a metal spring wire) having high electrical conductivity and high elastic modulus is used. As the metal material used for the metal conductor 11, copper alloys such as tungsten, tungsten rhodium, and benzene copper, palladium alloys, and copper-silver alloys can be appropriately used.

In order to suppress the increase in the contact resistance value between the metal conductor 11 and the inspection point 22 of the object to be measured 20 or the lead 37 of the detection device, a plating layer can be provided on the surface of the aforementioned metal material of the metal conductor 11 as needed. Examples of metals forming the plating layer include metals such as nickel, gold, and rhodium, and alloys such as gold alloys. The plating layer can be a single layer or multiple layers. As a multi-layer plating layer, it is preferred that a gold plating layer is formed on a nickel plating layer. There is no particular limitation on the thickness of the plating layer, and for example, it can be set to be greater than 1 μm and less than 5 μm.

In recent years, the metal conductor 11 has a tendency to be finer in diameter due to the demand for narrower pitch. The conductor diameter of the metal conductor 11 of this embodiment can be preferably 8 μm or more and 180 μm or less. Preferably, the conductor diameter can be within the range of 10 μm or more and 110 μm or less. The metal conductor 11 is manufactured by plastic working such as cold stretching or hot stretching to become a needle-shaped conductor of a predetermined diameter.

Furthermore, in order to easily install the contact probe 10 on the probe unit 30 and prevent it from getting stuck in the guide hole of the lower plate 34 of the probe unit 30 and hindering the movement of the contact probe 10, it is preferred to use a metal conductor 11 with high straightness. Specifically, it is preferred that the straightness is a curvature radius of 1000 mm or more. The metal conductor 11 with high straightness is obtained by performing a straightness correction process on the thin and long metal wire before the insulating film 12 is provided. The straightness correction process is performed, for example, by a rotary die type straightness correction device.

(End) One end 16 of the two ends of the metal conductor 11 contacts the inspection point 22 of the object 20 to be measured. As shown in FIG3 , the contact probe 10 of the present embodiment is a contact probe 10 in which at least the shape of the end 16 of the two ends of the metal conductor 11 that contacts the inspection point 22 of the object 20 to be measured is formed into a curved surface. In addition, when the radius of curvature of the curved surface is set to R and the diameter of the metal conductor 11 is set to D, a configuration in which R is greater than 0.5D and less than 5D (hereinafter, it may be expressed as 0.5D＜R≦5D) can be appropriately adopted. However, in order to form a curved surface under the above conditions, not only one end 16 but also both ends can be formed into curved surfaces under the above conditions.

By setting the curvature radius R of the curved surface of the end portion 16 to 0.5D＜R≦5D, the end portion 16 that contacts the check point 22 of the measured object 20 can be formed into a curved surface that is approximately close to a flat shape. Therefore, when the end portion 16 contacts the check point 22 of the measured object 20, it will not slide excessively. In addition, since the edge of the end portion 16 is not a right angle, it can make surface contact with the check point 22, which can suppress the cutting or scratching of the check point 22. In addition, the contact area with the check point 22 can be fully ensured.

As mentioned above, if the diameter of the metal conductor 11 is set to be greater than 8μm and less than 180μm, then, for example, when D=8μm, the curvature radius R of the end 16 is in the range of 4μm＜R≦40μm, and when D=180μm, the curvature radius R of the end 16 is in the range of 90μm＜R≦900μm.

In addition, as shown in FIG. 4 , the contact probe 10 of this embodiment can be used when it is arranged between two inspection points 22 of the object 20 to be measured. Furthermore, although a hemispherical inspection point 22 is illustrated in FIG. 4 , the shape of the inspection point 22 is not limited to the above-mentioned shape. In this case, the end portion will not slide excessively relative to the hemispherical inspection point 22, and the contact area with the inspection point 22 can be fully ensured. In addition, since the edge of the end portion 16 is not a right angle, it can contact the inspection point 22 surface without cutting or scratching the two inspection points 22.

As a method of forming the end 16 of the metal conductor 11 into the aforementioned shape, the end 16 of the metal conductor 11 is ground. The grinding process can be performed by using abrasive paper or a diamond grinding wheel. In addition, a known grinding machine that can grind needle-shaped metal materials can also be used.

(Insulating film) The insulating film 12 is not particularly limited in material as long as it is an insulating film, but one or more resin materials selected from polyurethane resin, nylon resin, polyester resin, epoxy resin, polyesterimide resin, polyamide resin, polyamideimide resin, etc. can be used appropriately. In addition, the heat resistance of the insulating film 12 composed of these resins varies depending on the type of resin, so it can be arbitrarily selected in consideration of the heat generated during the inspection of the measured body 20 or the ambient temperature.

The thickness of the insulating film 12 can be set appropriately within a range of 1 μm to 30 μm, as long as it can ensure electrical insulation, in consideration of the relationship with the diameter of the metal conductor 11. Preferably, the insulating film 12 is formed on the metal conductor 11 as a baking varnish film. Since the baking varnish film is formed by repeated coating and baking steps, it has good productivity, high adhesion to the metal conductor 11, and can further improve the film strength.

Furthermore, in the present embodiment, a region where the insulating film 12 is removed by a predetermined length is formed from each end portion 16 of the metal conductor 11. The length of the region where the insulating film 12 is removed can be appropriately set according to the structure of the probe unit 30 and the like.

(Example) In the following example, a thin and long tungsten rhodium wire (outer diameter D: 0.025 mm) is used as the metal conductor 11. The insulating film 12 is set to a two-layer structure, and the first insulating film uses a urethane resin-based baking varnish as a coating for the first insulating film, and the first insulating film is formed with a thickness of 1 μm. The second insulating film is formed by using the same baking varnish as the first insulating film, and containing 4 parts by weight of pigment (manufactured by BASF Japan Ltd., trade name: Irgazin (registered trademark)) relative to 100 parts by weight of the baking varnish to form the second insulating film with a thickness of 2.5 μm.

A standard cutting machine is used to cut a thin and long contact probe with an insulating film 12 (total thickness of about 3.5 μm) to cut a contact probe with an insulating film of 10 mm in length, and a predetermined length of both ends of the contact probe with the insulating film is laser stripped to produce a contact probe 10 having the configuration shown in FIG. 1. When the metal conductor 11 is processed by a grinding processing device, the shape of the end 16 is adjusted by appropriately adjusting the grinding angle and time, etc.

Furthermore, a nickel plating layer with a thickness of 1 μm is formed on the surface of the metal conductor 11 exposed by peeling off the insulating film 12, and then a gold plating layer with a thickness of 0.2 μm is formed thereon, so that a plating layer with a total thickness of 1.2 μm is formed.

FIG5 shows the result of evaluating the sliding of the end 16 relative to the inspection point 22 and the damage of the inspection point 22 when the curvature radius R of the curved surface of the end 16 of the contact probe 10 of the aforementioned embodiment is changed. Furthermore, in this embodiment, the diameter D of the metal conductor 11 is constant. Furthermore, the evaluation was performed for the case where the curvature radius R of the end as Comparative Example 1 is 0.5D, the case where the end as Comparative Example 2 is a flat shape, and the case where the end as Comparative Example 3 is a sharp angle.

Incidentally, FIG6 schematically illustrates the shape of the end of the contact probe 10 in the embodiment and the comparative example of FIG5. In FIG6A, the end is a curved surface. In FIG6B, the end is a flat shape. In FIG6C, the end is a sharp angle.

The sliding evaluation method is to conduct a contact test of 10,000 times between the end 16 of the contact probe 10 and the measured object 20. Among them, if the number of sliding times is less than 9 times, evaluation A is adopted, if the number of sliding times is more than 10 times and less than 99 times, evaluation B is adopted, and if the number of sliding times is more than 100 times, evaluation C is adopted.

The damage evaluation method is to conduct a contact test of 10,000 times between the end 16 of the contact probe 10 and the object 20 to be measured, wherein the evaluation A is adopted for the case of no damage, and the evaluation B is adopted for the case of damage.

Each embodiment is described below. The end of embodiment 1, R=5D, the corresponding model is Figure 6A. The sliding evaluation of embodiment 1 is A, and the damage evaluation is A.

The end of Example 2, R=4D, the corresponding model is Figure 6A. The sliding evaluation of Example 2 is A, and the damage evaluation is A.

The end of Example 3, R=3D, the corresponding model is Figure 6A. The sliding evaluation of Example 3 is A, and the damage evaluation is A.

The end of Example 4, R=2D, the corresponding model is Figure 6A. The sliding evaluation of Example 4 is A, and the damage evaluation is A.

The end of Example 5, R=1.5D, the corresponding model is Figure 6A. The sliding evaluation of Example 5 is A, and the damage evaluation is A.

The end of Example 6, R=D, the corresponding model is Figure 6A. The sliding evaluation of Example 6 is A, and the damage evaluation is A.

The end of Example 7 has R=0.9D, and the corresponding model is Figure 6A. The sliding evaluation of Example 7 is B, and the damage evaluation is A.

The end of Example 8, R=0.7D, the corresponding model is Figure 6A. The sliding evaluation of Example 8 is B, and the damage evaluation is A.

Furthermore, the end portion of Comparative Example 1, R=0.5D, has the same shape as that of Examples 1 to 8, but the radius of curvature is larger than that of Examples 1 to 8. The sliding evaluation of Comparative Example 1 is C, and the damage evaluation is A.

The end of Comparative Example 2 is flat, and the corresponding model is Figure 6B. The sliding evaluation of Comparative Example 2 is A, and the damage evaluation is B.

The tip of Comparative Example 3 is a sharp corner at the front end, and the corresponding model is Figure 6C. The sliding evaluation of Comparative Example 3 is A, and the damage evaluation is B.

From the results of FIG. 5 , it is clear that when the end of the contact probe 10 is a curved surface and the curvature radius R is R≦0.5D as in Comparative Example 1, it is easy to slide, so the sliding evaluation becomes poor. In addition, if the end of the contact probe is flat as in Comparative Example 2, although there is no problem with the sliding evaluation, damage will occur. Furthermore, if the end of the contact probe is sharp as in Comparative Example 3, although there is no problem with the sliding evaluation, damage will occur. Therefore, it can be determined that when the end of the contact probe 10 is a curved surface and the curvature radius R is 0.5D＜R≦5D, it becomes difficult to slide and will not be damaged, so it is better.

Furthermore, both the sliding evaluation and the damage evaluation of Examples 1 to 6 were A. Therefore, as shown in Examples 1 to 6, it was also found that the range of R of D≦R≦5D was more excellent.

10: Contact probe 11: Metal conductor 12: Insulation coating 14: Main body 16: End 20: Measured object 22: Inspection point 30: Probe unit 32: Upper plate 34: Lower plate 36: Support column 37: Lead wire

FIG1 is a schematic top view of the contact probe. FIG2 is an explanatory diagram showing the use of the contact probe. FIG3 is an enlarged view of the end of the contact probe. FIG4 is an explanatory diagram showing the end of the contact probe in contact with two inspection points. FIG5 is a table summarizing the results of the sliding test and the damage test when the shape of the end is changed. FIG6A to FIG6C are explanatory diagrams of the corresponding end shapes shown in the table of FIG5.

16: End

D: Diameter of metal conductor

R: Radius of curvature

Claims (2)

A contact probe comprises: a body having an insulating film on the outer periphery of a cylindrical metal conductor; and end portions formed at both ends of the metal conductor and not having the insulating film, and is bent by applying a load in an axial direction to obtain a contact pressure on a measured object to measure electrical characteristics. The contact probe is characterized in that: the metal conductor is of length 10mm, 0.025mm diameter tungsten tungsten, the end portion is nickel-plated on the surface of the metal conductor, and gold-plated on the nickel plating, and the shape of at least the end portion of the end portion that contacts the object to be measured is a curved surface, and when the radius of curvature of the curved surface is set to R, and the diameter of the metal conductor is set to D, R is greater than D and less than 5D. For example, the contact probe of claim 1, wherein the thickness of the insulating film is 3.5 μm.