JP2003121462A - Coaxial cable type probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coaxial cable type probe capable of effectively preventing the infiltration of noise and setting an impedance to 50 Ω. SOLUTION: In this coaxial probe, an external conductor is formed in the outer circumference of a central conductor via an insulator (dielectric body). A clearance with a predetermined length from the needle part side is formed between the outer circumference of the insulator and the inner circumference of the external conductor so that the central conductor can be moved backward and forward with the insulator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial cable type probe which is mainly used in a high frequency range and is brought into contact with a device under test when measuring the transmission characteristic of a transmission line and the characteristic of an electronic circuit component.

[0002]

2. Description of the Related Art Conventionally, as a coaxial probe mainly used in a high frequency region, a cylindrical body which is a metal wire or a thin wire and has a tapered needle-shaped central conductor at an end thereof as an external conductor via a dielectric substance. There has been known a coaxial probe which is housed inside and is formed into an elongated cylindrical shape as a whole.

In this coaxial probe, the needle portion at the tip of the central conductor comes into contact with the first signal terminal of the DUT, and the connecting pin for connecting to the ground side of the cylindrical body serving as the external conductor is
The ground terminal or the second signal terminal is simultaneously contacted.

However, in this conventional coaxial probe, since the tip needle portion projects from the outer conductor, a large amount of unnecessary signals, noises, etc. enter from the gap between the outer conductor and the tip of the needle portion. This is a cause of increased transmission loss of high frequency signals.

For this reason, there are commercially available probes in which a protrusion is separately provided on the outer conductor (ground side) and noise is cut by the protrusion, but this has a drawback that noise and the like cannot be sufficiently cut.

In order to solve such a problem, the applicant of the present invention has devised a coaxial probe in which the center conductor can be moved forward and backward by a spring probe. In this probe, the needle portion moves backward during measurement. Therefore, since no gap is formed between the outer conductor and the outer conductor, it is possible to prevent the intrusion of noise, but the center conductor slightly shifts with the movement, so that the impedance required for this type of coaxial cable probe is 50Ω or 75Ω There was a problem that could not be made almost constant.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem, and it is possible to effectively prevent the intrusion of noise and to make the impedance substantially constant such as 50Ω or 75Ω. It is an object of the present invention to provide a coaxial cable type probe that can be used.

[0008]

In order to achieve the above object, as a result of earnest research, the present inventor has conducted a backward movement of a central conductor together with an insulator to effectively prevent the intrusion of noise and reduce the impedance. The present invention has been accomplished by finding that it can be made approximately constant such as 50Ω or 75Ω.

That is, the present invention provides a coaxial probe in which an outer conductor is formed on the outer periphery of a center conductor via an insulator (dielectric), and the center conductor together with the insulator moves backward
In order to be able to move forward, a gap having a predetermined length is formed from the needle portion side between the outer circumference of the insulator and the inner circumference of the outer conductor.

It is particularly preferable to use polyfluorinated ethylene (Teflon) as the insulator (claim 2). The insulator has a diameter of 2 mm or less, preferably 1 mm or less (claim 3).

By partially enlarging the inner diameter of the outer conductor, a gap is formed between the insulator and the outer conductor.
This is preferable because the insulators can have the same thickness (claim 4).

In the probe of the present invention, when the needle portion of the center conductor hits the object to be measured, the insulator and the center conductor move backward together, and the outer conductor hits the object to be measured. ).

The coaxial cable type probe of the present invention is particularly suitable for a coaxial cable type probe used in a high frequency region (claim 6).

As a condition required for the high frequency probe,
There are impedances such as 50Ω and 75Ω, but 50Ω ± 5Ω is predominant for general electronic devices. According to the present invention, the outer conductor has an inner diameter of two steps, the front outer conductor is made slightly larger than the outer diameter of the 50Ω derivative to have an impedance larger than 50Ω, and the rear outer conductor has an impedance smaller than 50Ω. 50 in total
The impedance can be set to Ω ± 5Ω.

Next, an embodiment of the present invention will be described with reference to the drawings.

[0016]

1 shows an embodiment of the present invention, in which an outer conductor 3 is formed on a central conductor 1 with a polyfluorinated ethylene (insulator) 2 interposed therebetween. The outer conductor 3 is externally fitted and fixed to the insulator 2 except for the upper portion 3'of FIG.

The upper portion 3'of the outer conductor 3 is formed to have a slightly larger diameter, and a slight gap 4 is formed between the outer conductor 3 and the insulator 2.

The center conductor 1 and the outer conductor 3 may be made of the same materials as in the prior art and are not particularly limited. It is preferable to use, for example, tungsten, a hard copper alloy or the like as the central conductor, and to use, for example, a copper alloy or copper as the outer conductor.

As shown in FIG. 2, when the needle portion 1'of the central conductor 1 hits the object to be measured 5, the central conductor 1 and the insulator 2
Becomes a slightly looser S-shape and moves backward, and the center conductor tip 1
′ And the outer conductor tip 3 ′ are in contact with each other at the same time and are flush with each other, so that no gap is formed, so that noise cannot enter as indicated by the arrow. The contact is over,
When the needle part is separated from the object to be measured (object to be inspected), the needle part 1'returns to the original protruding shape. As described above, according to the present invention, the center conductor 1 and the outer conductor 3 together hit the object to be measured, so that a ground is not particularly required unlike the conventional probe.

In the above embodiment, as shown in FIG. 1, the difference between the upper end of the outer conductor tip 3'and the upper end of the insulator 2 is about 0.1 m.
the outer conductor tip 3'and the needle 1
The difference from ′ is about 0.1 mm to 0.2 mm. The gap 4 between the outer conductor 3'and the insulator 2 has a tip of 0.2
Since it may be less than or equal to mm, a minute gap is sufficient, and in the case of FIG. 1, the width of the gap is preferably 5 to 10 μm. The length of the large-diameter portion 3'is about 8 to 10 times the outer diameter of the insulator, and about 10 mm in the embodiment of FIG. In addition, when the tip portion is projected beyond 0.2 mm, the large diameter portion 3 '
The length may be longer than the above.

The reason why the needle portion 1 ′ of the central conductor and the insulator 2 move backward by pressing is that the insulator meanders slightly. To make the insulator 2 meander, the width of the gap 4 ( Depending on the length (between the insulator 2 and the outer conductor 3 ') and the length, the diameter of the insulator 2 is particularly preferably 1 mm or less.

The outer conductor preferably has a diameter of 1 mm or less,
Particularly preferably, the diameter is about 1 mm to 0.2 mm, and if it is larger than this, a strong pressing force is required due to the hardness of the material of polyfluoroethylene (Teflon), and therefore a fine pitch electrode for electronic devices. Not desirable for measurement.

FIG. 3 shows a state in which the insulator 2 moves backward during contact, and FIG. 4 shows an extremely meandering state in order to make it easier to understand. Actually, as shown in FIG. 3, the insulator slightly meanders and retracts, and returns to its original position by the meandering torque.

Next, an example of manufacturing the probe of the present invention will be shown.
The central conductor 1 and the dielectric material (Teflon) 2 are adhered to each other based on a predetermined specification known in advance (B in FIGS. 3 and 4).
make.

A pipe material which will be the outer conductor 3 (see FIGS. 3 and 4).
A) is, from the predetermined dimensions of the center conductor and the dielectric (B),
It has a large diameter (preferably a diameter of 5 to 10 microns) as long as the meandering is required.

The pipe material (A) and the central conductor and the dielectric (B)
After inserting, the pipe material (A) is reduced and fixed in the C portion of FIGS. 3 and 4 by a mold or a die so as to match the determined impedance. Figure 3
As shown in FIG. 4 and FIG. 4, the above-described meandering expansion / contraction operation is performed in the non-reduced portion B.

In the above embodiment, the B section is 52Ω and the C section is 4Ω.
As the calculated value of 8Ω, the impedance was set within the range of 50Ω ± 5Ω.

[0028]

As described above, according to the present invention, a gap is formed between the insulator and the outer conductor, and the needle portion is moved forward and backward, which has never been done in the past. The present invention has solved the problem that the coaxial cable type probe of this kind, which can maintain the impedance of 50Ω and effectively prevent the intrusion of noise, which could not be solved in the past, and therefore is an extremely innovative invention. Is. Moreover, according to the present invention, it is possible to obtain an advantage that a ground is not required unlike the conventional case.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the contact probe of the present invention is brought into contact with an object to be measured.

FIG. 3 is a partial cross-sectional view showing an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view showing a state in which an insulator meanders.

[Explanation of symbols]

1 .......... Center conductor 1 '... 2 ... Insulator 3 ... External conductor 3 '... The large diameter part of the outer conductor 4 ......... Gap 5 ......... DUT

Claims (6)

[Claims] 1. A coaxial probe having an outer conductor formed on the outer periphery of a central conductor via an insulator (dielectric) so that the central conductor can move backward and forward together with the insulator.
A coaxial cable type probe, wherein a gap having a predetermined length is formed from the needle portion side between the outer circumference of the insulator and the inner circumference of the outer conductor. 2. The probe according to claim 1, wherein the insulator is polyfluorinated ethylene (Teflon). 3. The probe according to claim 1, wherein the insulator has a diameter of 1 mm or less. 4. The probe according to claim 1, wherein a gap is formed between the insulator and the outer conductor by partially enlarging the inner diameter of the outer conductor. 5. When the needle portion of the central conductor hits the object to be measured, the insulator and the central conductor move backward together, and the outer conductor hits the object to be measured. The coaxial cable probe according to any one of Items 1 to 4. 6. The coaxial cable type probe according to claim 1, which is used in a high frequency region.