Probe

Abstract

To provide a probe with which it is possible to suppress a barrel and a coil spring from coming into contact.SOLUTION: A probe 1 comprises: a tubular barrel 10; a first plunger 20 that slides along the axial direction of the barrel 10 while the base end part 21 is inserted from one opening end of the barrel 10 and the tip is exposed; and a coil spring 40 arranged inside of the barrel 10, for urging the first plunger 20 in the axial direction of the barrel 10. The base end part 21 of the first plunger includes an insertion part 211 for extending the inside of the coil spring 40 from one end of the coil spring 40, and a head part 212 connected to the insertion part 211 and, with its outside diameter larger than the outside diameter of the coil spring 40, coming into contact with one end of the coil spring 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a probe used for measuring the characteristics of an object to be inspected.

Background Art

[0002] Probes are used to measure the characteristics of objects to be inspected, such as integrated circuits, in a wafer state. In the measurement using a probe, one end of the probe is brought into contact with the electrode of the object to be inspected, and the other end of the probe is brought into contact with a terminal (hereinafter referred to as a "land") arranged on a printed circuit board or the like. The land is electrically connected to a tester.

[0003] For the probe, a configuration in which a part of a plunger having a small diameter that contacts the object to be inspected is inserted into a barrel having a large-diameter tubular shape is used. For example, the plunger is urged by a coil spring disposed inside the barrel, and the probe is brought into contact with the object to be inspected at a predetermined needle pressure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Due to the narrowing of the pitch of the electrode arrangement and the increase in the number of electrodes of the object to be inspected, the probe has become thinner and has more pins. For this reason, the outer diameter of the probe becomes thinner, and accordingly, it is necessary to make the wire diameter of the coil spring thinner. However, the thinner the wire diameter, the more likely the coil spring is to meander, and the coil spring contacts the inner wall surface of the barrel. As a result, there has been a problem that the barrel and the coil spring are damaged.

[0006] In view of the above problems, an object of the present invention is to provide a probe capable of suppressing contact between a barrel and a coil spring.

Means for Solving the Problem

[0007] According to one aspect of the present invention, there is provided a tubular barrel, a first plunger whose base end is inserted from the open end of the barrel and slides along the axial direction of the barrel, a second plunger whose base end is inserted from the other open end of the barrel and is fixed to the barrel with its tip exposed, and a coil spring disposed inside the barrel and biasing the first plunger in the axial direction of the barrel. The first plunger is provided with an insertion portion provided at the base end portion and extending inside the coil spring from one end of the coil spring inside the barrel, Provided at the base end portion, a head connected to the insertion portion, having an outer diameter larger than that of the coil spring and abutting against one end of the coil spring, a neck connected to the head and thinner in diameter than the head and extending in a direction opposite to the insertion portion inside the barrel, a first body portion connected to the neck and thicker in diameter than the neck and connected inside the barrel, a flange connected to the first body portion, having a diameter thicker than that of the first body portion and abutting against the probe head when installed on the probe head, and a second body portion connected to the flange, having a diameter thinner than that of the flange and protruding from the probe head when installed on the probe head. The inner diameter of the barrel is the same in the region through which the base end portion and the first body portion of the first plunger pass and the region through which the coil spring passes. The barrel has a first joint portion with an inner diameter through which the head cannot pass but the neck can pass, and supports the first plunger at two points, namely, the head and the first body portion of the first plunger. and the probe has a maximum stroke amount of 450 μm to secure a maximum value of the overdrive amount of 300 μm when a load of 7 gf or less is applied, and the length extending inside the coil spring of the insertion portion is equal to or greater than the maximum value of the overdrive amount applied during measurement of the semiconductor device which is the measurement object A probe is provided.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a probe that can suppress the contact between the barrel and the coil spring.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0010] Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the ratio of the thickness of each part is different from the actual one. Also, it goes without saying that there are parts where the dimensional relationships and ratios are different between the drawings. The embodiments shown below illustrate devices and methods for embodying the technical idea of the present invention, and the embodiments of the present invention do not specify the materials, shapes, structures, arrangements, etc. of the components as follows.

[0011] The probe 1 according to the embodiment of the present invention includes a tubular barrel 10, a rod-shaped first plunger 20 having a base end portion 21 inserted from one open end of the barrel 10, and a coil spring 40 disposed inside the barrel 10. The first plunger 20 slides along the axial direction of the barrel 10 with its tip exposed from the open end of the barrel 10. The coil spring 40 biases the first plunger 20 in the axial direction of the barrel 10.

[0012] Furthermore, the probe 1 has a rod-shaped second plunger 30 with its base end 31 inserted from the other open end of the barrel 10. The second plunger 30 is joined to the barrel 10 with its tip exposed from the open end of the barrel 10. One end of the coil spring 40 abuts against the base end 21 of the first plunger 20, and the other end abuts against the base end 31 of the second plunger 30. In the probe 1 shown in FIG. 1, the coil spring 40 biases the first plunger 20 and the second plunger 30 in a direction away from each other.

[0013] The first plunger 20 shown in FIG. 1 has a configuration in which a base end 21, a neck 22, a first body portion 23, a flange 24, and a second body portion 25 are connected in sequence. The base end 21 of the first plunger 20 has an insertion portion 211 extending inside the coil spring 40 from one end of the coil spring 40, and a head 212 connected to the insertion portion 211. The head 212 having an outer diameter larger than the outer diameter of the coil spring 40 abuts against one end of the coil spring 40.

[0014] The first plunger 20 is prevented from falling out of the barrel 10 and is retained in the barrel 10 so that the base end 21 is not fixed inside the barrel 10. For example, the first joint portion 101 of the barrel 10 is caulked to a depth such that the head 212 of the first plunger 20 does not come out and the neck 22 having a smaller diameter than the head 212 can pass through. As a result, the neck 22 passes through the first joint portion 101, and the base end 21 of the first plunger 20 slides inside the barrel 10 without coming out of the barrel 10.

[0015] The neck 22 is connected inside the barrel 10 to the first body portion 23 having a larger diameter than the neck 22. For this reason, the first plunger 20 inside the barrel 10 is guided at two points, the head 212 and the first body portion 23. Thereby, the inclination of the first plunger 20 inside the barrel 10 can be suppressed. Also, a flange 24 having a larger diameter than the first body portion 23 and the second body portion 25 is disposed between the first body portion 23 and the second body portion 25.

[0016] The second plunger 30 shown in FIG. 1 is configured by connecting a base end portion 31, a neck portion 32, a first body portion 33, and a second body portion 34 in sequence. The base end portion 31 of the second plunger 30 abuts against one end of a coil spring 40 disposed inside the barrel 10.

[0017] The second plunger 30 is joined to the barrel 10 at the second joint portion 102. For example, as shown in FIG. 1, the second plunger 30 is fixed to the barrel 10 by caulking at a position of the neck portion 32 having a smaller diameter than the base end portion 31 and the first body portion 33. Note that the second plunger 30 and the barrel 10 may be joined by crimping, welding, or the like.

[0018] As described above, the probe 1 functions as a single-end sliding type probe in which the second plunger 30 is fixed to the barrel 10 and the first plunger 20 slides inside the barrel 10.

[0019] When measuring the object to be measured, the tip of the second body portion 25 of the first plunger 20 is connected to the object to be measured, and the tip of the second body portion 34 of the second plunger 30 is connected to the land. Then, an electrical signal propagates between the first plunger 20 and the second plunger 30 via the barrel 10 and the coil spring 40. Therefore, a conductive material is used for the barrel 10, the first plunger 20, the second plunger 30, and the coil spring 40.

[0020] For the barrel 10, a conductive metal material such as nickel (Ni), nickel alloy, copper (Cu), or copper alloy is used. Note that the inner wall surface of the barrel 10 may be gold-plated. Also, for the first plunger 20 and the second plunger 30, a conductive metal material such as a palladium (Pd) alloy or copper alloy is used. For the coil spring 40, a conductive material such as hard steel wire, piano wire, or stainless steel wire is used. The surface of the coil spring 40 may be gold-plated.

[0021] Probe 1 is held by probe head 2 as shown in FIG. 2, for example. That is, probe 1 is held by probe head 2 in a state where probe 1 penetrates through a plurality of guide plates constituting probe head 2. Materials such as ceramics are used for probe head 2.

[0022] The probe head 2 illustrated in FIG. 2 has a bottom guide plate 201, a middle guide plate 202, and a top guide plate 203. The first plunger 20 penetrates through the guide hole of the bottom guide plate 201, and the second plunger 30 penetrates through the guide hole of the top guide plate 203. Then, the barrel 10 penetrates through the guide hole of the middle guide plate 202 disposed between the bottom guide plate 201 and the top guide plate 203. The outer diameter of the flange 24 is thicker than the inner diameter of the guide hole of the bottom guide plate 201, and the flange 24 abuts against the bottom guide plate 201. Thereby, probe 1 is prevented from falling out of probe head 2.

[0023] When measuring using probe 1, as shown in FIG. 3, the tip of the second body portion 34 of the second plunger 30 is connected to the land 301 of the printed circuit board 3. At this time, a preload for pressing the second plunger 30 against the land 301 is applied to probe 1 so that the second plunger 30 contacts the land 301 with a certain pressing force. Due to the preload, the portion of the second plunger 30 exposed from the upper surface of the probe head 2 becomes shorter. At this time, the flange 24 of the first plunger 20 is pressed against the bottom guide plate 201, and the coil spring 40 contracts.

[0024] Then, as shown in FIG. 4, the tip of the second body portion 25 of the first plunger 20 is connected to the electrode 401 of the measurement object 4 such as a semiconductor device. At this time, an overdrive for pressing the first plunger 20 against the electrode 401 is applied to probe 1 so that the first plunger 20 contacts the electrode 401 with a predetermined needle pressure. Due to the overdrive, the first plunger 20 is pushed into the inside of the barrel 10, and the coil spring 40 contracts.

[0025] The specifications of the probe 1 are set such that the maximum stroke amount of the probe 1 is longer than the distance that the first plunger 20 slides due to preload or overdrive. Here, the "stroke" of the probe 1 is the difference between the overall length of the probe 1 when the coil spring 40 is at its free length and the overall length of the probe 1 when the coil spring 40 is contracted. For example, the total amount of contraction of the coil spring 40 due to preload and overdrive is the stroke. Note that the maximum stroke amount is determined by the load maintenance (durability) of the coil spring 40. The maximum value of the stroke amount for which there is no load degradation even when the coil spring 40 repeatedly expands and contracts (for example, 1,000,000 times or more) is the maximum stroke amount.

[0026] An electrical signal propagates between the land 301 and the measurement object 4 via the probe 1. That is, via the probe 1, an electrical signal from the tester is transmitted to the measurement object 4, and the electrical signal output from the measurement object 4 is transmitted to the tester. After measurement, by separating the probe 1 from the measurement object 4, the contracted coil spring 40 extends.

[0027] By the way, due to factors such as the narrowing of the pitch of the electrode arrangement of the measurement object 4 or the increase in the number of electrodes, the following requirements arise for the probe 1.

[0028] That is, as the pitch of the electrode arrangement of the measurement object 4 narrows, it is necessary to reduce the outer diameter of the probe 1. For example, when the pitch of the electrode arrangement is 150 μm or less, the outer diameter of the probe 1 is around 100 μm. To reduce the outer diameter of the probe 1, the outer diameter of the coil spring 40 housed inside the barrel 10 is also reduced. For this reason, it is necessary to reduce the wire diameter of the coil spring 40. For example, the outer diameter of the coil spring 40 inserted into the barrel 10 with an outer diameter of around 100 μm is around 80 μm, and the wire diameter of the coil spring 40 is around 20 μm.

[0029] On the one hand, the thinner the wire diameter of the coil spring 40, the lower the rigidity of the coil spring 40. For this reason, the coil spring 40 is more likely to bend inside the barrel 10. As a result, there is a drawback that the coil spring 40 contacts the inside of the barrel 10.

[0030] In addition, due to the increase in the number of electrodes of the measurement object 4 and the multiplexing of the inspection for simultaneously inspecting a plurality of measurement objects 4, the probe card has multiple pins. As a drawback of this multi-pinning, the total load of the probes 1 arranged on the probe card may increase. Here, the "load" is the pressure when the probe 1 is pressed against the electrode 401 of the measurement object 4.

[0031] For example, when the load of one probe 1 is 10 gf, the total load of 10,000 probes 1 is 100 kgf. The higher the total load of the probes 1, the higher the pressure applied to the probe card and the members supporting the probe card. For this reason, when the total load of the probes 1 increases, various inspection facilities used for inspecting the measurement object 4 may be damaged exceeding the load capacity. In addition, it is necessary to complicate the shape of the structure or use an expensive material to increase the rigidity of the probe card.

[0032] Therefore, it is required to achieve both stable contact between the measurement object 4 and the probe 1 with a low load and a high stroke sufficient to absorb variations in the inspection for the probe 1. Here, the "variations" include variations in the height of bumps when the electrode 401 of the measurement object 4 is a bump such as solder, and variations in the interval between the electrode 401 of the measurement object 4 and the probe 1 caused by distortion of the inspection facility and the probe card due to the total load of the probe 1.

[0033] As described above, there is a need for a probe 1 that can cope with the narrowing of the electrode pitch of the object to be measured 4 and that can meet the requirements of low load and high stroke. For example, the probe 1 is required to have characteristics corresponding to an electrode arrangement with a pitch of 150 μm or less, a load of 7 gf or less, and a stroke amount of 400 μm or more. If the load is 7 gf or less, it becomes easy to keep the load applied to the inspection equipment and the probe card within the allowable load range. If the stroke amount is 400 μm or more, a sufficient 300-μm overdrive amount can be ensured for the contact between the probe 1 and the electrode 401 of the object to be measured 4 in order to suppress a decrease in measurement accuracy.

[0034] Here, in order to compare with the probe 1 shown in FIG. 1, the probe 1A of the comparative example shown in FIG. 5 is examined. The probe 1A of the comparative example shown in FIG. 5 has a configuration in which a coil spring 40A is disposed inside a barrel 10A, and the base end portion 21A of the first plunger 20A and the base end portion 31A of the second plunger 30A abut against the end portion of the coil spring 40A inside the barrel 10A. The first plunger 20A slides inside the barrel 10, and the second plunger 30A is fixed to the barrel 10A. Note that the base end portion 21A of the first plunger 20A does not have a portion extending inside the coil spring 40.

[0035] As a method for realizing low load and high stroke with respect to the probe 1A of the comparative example, it is conceivable to increase the effective number of turns of the coil spring 40A. However, by reducing the diameter of the coil spring 40A and increasing the effective number of turns, as shown in FIG. 6, when the coil spring 40A contracts inside the barrel 10A, the coil spring 40 greatly meanders. If the meandering of the coil spring 40A is large, the coil spring 40A comes into contact with the inner wall surface of the barrel 10A, and problems such as damage to the coil spring 40A and the barrel 10A occur.

[0036] That is, due to strong rubbing of the coil spring 40A against the inner wall surface of the barrel 10A, the surface of the coil spring 40A is scraped or the inner wall surface of the barrel 10A is peeled off. As a result, the electrical resistance value of the probe 1A increases.

[0037] For example, as a result of a probe durability test in which the over-drive amount is set to 300 μm and the sliding of the first plunger 20A is repeated 500,000 times, the electrical resistance value of the entire probe 1A increases to several tens to a hundred times the initial value. In addition, due to the meandering of the coil spring 40A, the coil spring 40A strongly rubs against the inner wall surface of the barrel 10A, causing the barrel 10A to wear out, and holes may occur on the side surface of the barrel 10A.

[0038] Note that damage to the coil spring 40A or the barrel 10A due to the meandering of the coil spring 40A is likely to occur on the first plunger side of the coil spring 40A. This is due to the difference in the sliding amount of each part of the coil spring 40A as follows.

[0039] The position where the sliding amount of the coil spring 40A is the largest is the contact point with the first plunger 20A of the coil spring 40A. The sliding amount at this contact point is equivalent to the over-drive amount. On the other hand, the position where the sliding amount of the coil spring 40A is the smallest is the contact point with the second plunger 30A of the coil spring 40A, and the sliding amount at this contact point is zero. Using the over-drive amount OD and the effective number of turns n of the coil spring 40A, the sliding amount S(i) at the position of the i-th turn from the contact point with the first plunger 20A is approximately expressed by the following formula (1) (1 ≤ i ≤ n): S(i)=OD - i×(OD / n) ···(1) Thus, since the sliding amount of the coil spring 40A is large on the first plunger side, damage to the coil spring 40A and the barrel 10A occurs on the first plunger side.

[0040] In order to suppress damage to the coil spring 40A and the barrel 10A caused by the sliding of the coil spring 40A, measures to reduce the overdrive amount and the stroke amount can also be considered. For example, for the probe 1A with a narrow pitch (150 μm or less) and a low load (7 gf or less), the overdrive amount is set to 200 μm and the maximum stroke amount is set to 300 μm. By reducing the overdrive amount and the stroke amount, the wear amount (rubbing distance, rubbing amount) between the coil spring 40A and the inner wall surface of the barrel 10A can be reduced. Thereby, damage to the coil spring 40A and the barrel 10A can be suppressed. However, when the overdrive amount and the stroke amount are reduced, it is difficult to absorb variations in the inspection of the measurement object 4.

[0041] On the other hand, according to the probe 1 shown in FIG. 1, by providing the insertion portion 211 at the base end portion 21 of the first plunger 20, as shown in FIG. 7, the meandering of the coil spring 40 can be suppressed. As a result, damage to the coil spring 40 and the barrel 10 can be suppressed.

[0042] As shown in FIG. 8, when the difference between the inner diameter of the coil spring 40 and the outer diameter of the insertion portion 211 is the clearance C1, and the difference between the inner diameter of the barrel 10 and the outer diameter of the coil spring 40 is the clearance C2, it is preferable to set the outer diameter of the insertion portion 211 such that C1 < C2. This is to suppress the meandering of the coil spring 40 by reducing the clearance C1, and to suppress the contact between the barrel 10 and the coil spring 40 by making the clearance C2 as large as possible.

[0043] For example, when the clearance C2 between the inner diameter of the barrel 10 and the outer diameter of the coil spring 40 is 10 μm, if the inner diameter of the coil spring 40 is 40 μm, the outer diameter of the insertion portion 211 is set to 31 μm or more. However, the outer diameter of the insertion portion 211 is made smaller than the minimum diameter including the tolerance of the inner diameter of the coil spring 40.

[0044] Also, the length along the axial direction of the barrel 10 that extends inside the coil spring 40 of the insertion portion 211 (hereinafter simply referred to as "length") is preferably as long as possible to suppress the meandering of the coil spring 40. For example, in order to cover the range in which the coil spring 40 contracts due to over-drive, it is preferable that the length of the insertion portion 211 is equal to or greater than the maximum value of the over-drive amount.

[0045] For example, in the case of the probe 1 with the maximum specification of the over-drive amount being 300 μm, the length of the insertion portion 211 is set to 300 μm or more. However, the length of the insertion portion 211 is set so that the insertion portion 211 does not contact the base end portion 31 of the second plunger 30 when the maximum stroke amount is applied to the probe 1.

[0046] Also, the size of the head 212 of the first plunger 20 is set so as to maintain a stable contact resistance between the head 212 and the barrel 10 and to avoid damage to the inner wall surface of the barrel 10 due to contact with the head 212.

[0047] Specifically, the outer diameter of the head 212 is made larger than the outer diameter of the coil spring 40. For example, when the outer diameter of the coil spring 40 is 80 μm, the outer diameter of the head 212 is set to 81 μm or more. However, the outer diameter of the head 212 is made smaller than the minimum value including the tolerance of the inner diameter of the barrel 10.

[0048] Note that the range in which the coil spring 40 may rub against the inner wall surface of the barrel 10 due to over-drive corresponds to the over-drive amount. Therefore, when the length of the head 212 is shorter than the over-drive amount, it is conceivable that the head 212 contacts only the region where the coil spring 40 rubs against the inner wall surface of the barrel 10. Therefore, it is preferable that the length of the head 212 is equal to or greater than the maximum value of the over-drive amount. As a result, the head 212 surely contacts the inner wall surface of the barrel 10 in a region where the coil spring 40 does not rub. As a result, the contact between the barrel 10 and the first plunger 20 is stabilized, and the contact resistance is also stabilized.

[0049] For example, in the case of the probe 1 with the specification of the maximum value of the overdrive amount being 300 μm, the length of the head 212 shall be 300 μm or more. However, the length of the head 212 shall be within the range where the length of the neck 22 can ensure a length equal to or greater than the maximum stroke amount. If the length of the neck 22 is not equal to or greater than the maximum stroke amount, there is a possibility that the first body portion 23 contacts the first joint portion 101 and the stroke is inhibited.

[0050] As described above, in the probe 1 according to the embodiment of the present invention, the proximal end portion 21 of the first plunger 20 has an insertion portion 211 inserted inside the coil spring 40 and a head portion 212 connected to the insertion portion 211 and abutting against the coil spring 40. According to the probe 1, the meandering during the contraction of the coil spring 40 is suppressed. And by setting the sizes of the insertion portion 211 and the head portion 212 as described above, damage to the inner wall surface of the coil spring 40 and the barrel 10 can be suppressed. For example, for the probe 1 corresponding to a narrow pitch of 150 μm or less and a low load of 7 gf or less, a high stroke with a maximum stroke amount of 450 μm can be realized while ensuring 300 μm as the maximum value of the overdrive amount.

[0051] According to the probe 1, in the probe durability test in which the sliding with an overdrive amount of 300 μm is repeated one million times, the electrical resistance value of the entire probe 1 does not change from the initial state. In this way, a probe 1 with improved durability can be realized.

[0052] (Other Embodiments) As described above, the present invention has been described by way of embodiments, but it should not be understood that the discussions and drawings forming a part of this disclosure limit this invention. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

[0053] For example, in the above description, a configuration in which plungers are inserted into the open ends at both ends of the barrel 10 is shown, but a configuration in which only the first plunger 20 is inserted into the barrel 10 may also be used. That is, the probe 1 may be structured such that the tip of the first plunger 20 inserted into one end of the barrel 10 contacts the measurement object 4, and the other end of the barrel 10 contacts the land 301.

[0054] Thus, the present invention naturally includes various embodiments and the like not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specific matters according to the legitimate claims based on the above description.

Description of Reference Numerals

[0055] 1…probe 10…barrel 20…first plunger 21…base end portion 30…second plunger 40…coil spring 211…insertion portion 212…head

Claims

1. A barrel having a tubular shape, a first plunger inserted with its base end from one open end of the barrel and sliding along the axial direction of the barrel with its tip exposed, a second plunger inserted with its base end from the other open end of the barrel and fixed to the barrel with its tip exposed, a one-end sliding type probe disposed inside the barrel and including a coil spring that biases the first plunger in the axial direction of the barrel, wherein the first plunger has an insertion portion provided at the base end and extending inside the coil spring from one end of the coil spring inside the barrel, has a head provided at the base end, connected to the insertion portion, having an outer diameter larger than that of the coil spring, and abutting against the one end of the coil spring, has a neck connected to the head and extending in a direction opposite to the insertion portion inside the barrel, the neck having a diameter thinner than that of the head, has a first body portion connected to the neck inside the barrel, the first body portion having a diameter thicker than that of the neck, has a flange connected to the first body portion, the flange having a diameter thicker than that of the first body portion and abutting against a probe head when installed on the probe head, and has a second body portion connected to the flange, the second body portion having a diameter thinner than that of the flange and protruding from the probe head when installed on the probe head, and the inner diameter of the barrel is the same in a region through which the base end portion and the first body portion of the first plunger pass and a region through which the coil spring passes, the barrel has a first joint portion having an inner diameter through which the head cannot pass but the neck can pass, and supports the first plunger at two points, i.e., the head and the first body portion of the first plunger, the probe has a maximum stroke amount of 450 μm to ensure a maximum value of the overdrive amount of 300 μm when a load of 7 gf or less is applied, and the length of the insertion portion extending inside the coil spring is equal to or greater than the maximum value of the overdrive amount applied during measurement of a semiconductor device as the object to be measured, characterized in that it is a probe.

2. The probe according to claim 1, characterized in that the coil spring biases the first plunger and the second plunger in a direction away from each other.

3. The probe according to claim 1, characterized in that the length of the head along the axial direction of the barrel is equal to or greater than the maximum value of the overdrive amount applied during measurement of the object to be measured.

4. The probe according to any one of claims 1 to 3, characterized in that a clearance between an inner diameter of the coil spring and an outer diameter of the insertion portion is smaller than a clearance between an inner diameter of the barrel and an outer diameter of the coil spring.

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