JPH07113821A - Terminal and method for measuring electric characteristic - Google Patents

Abstract

PURPOSE:To make it easy to measure electric characteristics by providing a needle-shaped or drill-like terminal and a rotating mechanism for the terminal, and insulating and coating other parts than a front end part. CONSTITUTION:A female screw and a male screw are formed in an inner periphery of a cylindrical body 1 and in an outer periphery of a rotation body 2, respectively. The screws are meshed with each other. A needle-shaped terminal 3 of copper is built in at the center of the rotation body 2, which projects from a bottom of the rotation body 2. A GND layer 5 is provided in an outer periphery of the terminal 3 via an insulating layer 4. The terminal 3 and insulating layer 4, GND layer 5 are connected to a measuring apparatus by a coaxial cable 6. In order to measure electric characteristics of a printed board having an insulating protective layer on a measuring circuit, the terminal 3 is placed on the board and set on the measuring circuit while a front end of the terminal 3 is observed from a peephole. The rotation body 2 is rotated and descended to bring the front end of the terminal 3 into the insulating protective layer to be in touch with the measuring circuit. If an insulating film is coated at other parts than the front end part of the terminal 3, the terminal 3 is allowed to penetrate the protective layer and a circuit not to be subjected to measurement to be in touch with the measuring circuit even when the not-to-be-measured circuit is on the measuring circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal and method for measuring electric characteristics of a printed circuit or the like.

[0002]

2. Description of the Related Art Conventionally, as a terminal of this type, as shown in FIG. 6, a method of sandwiching a lead wire 21 drawn from a measuring circuit end or a measuring circuit 20 with a clip 22 or the like,
As shown in FIG. 7, a method is used in which the terminal 23 having a rod-shaped or needle-shaped tip is brought into direct contact with the measuring circuit.

[0003]

However, in the case of the sandwiching type, it is necessary to pull out the lead wire by soldering or the like when the measurement is performed on a flat plate-shaped circuit. Further, when a lead wire or the like is used, the influence of noise also becomes a problem when measuring electrical characteristics at high frequencies. Furthermore, impedance mismatch may occur between the lead wire and the cable between the measuring terminal and the measuring device, which causes inconvenience depending on the measurement content.

On the other hand, in the case where the terminal is brought into direct contact with the measuring circuit, when the protective layer is provided on the circuit, the terminal cannot be brought into contact with the measuring circuit unless part of it is removed beforehand. Therefore, it is necessary to previously form a portion where the protective layer is not provided as the measuring terminal when the measurement sample is prepared, or to remove the protective layer of the measuring terminal portion. However, in the former case, it is complicated to form a portion where the protective layer is not provided. In addition, in the latter case, in addition to the complexity of removing the protective layer, the surface of the measurement circuit may be damaged or the structure may be changed, resulting in a decrease in measurement accuracy. That is, in any case, measurement requires time, labor, special technique, and the like, and in some cases, the measurement accuracy is deteriorated, so that the measurement of electrical characteristics is difficult.

[0005]

The present invention has been made to solve the above problems, and is characterized by having a needle-shaped or drill-shaped terminal and a rotating mechanism therefor.
Here, by covering an area other than the tip end portion of the terminal with an insulator, it is possible to cope with a case where there is a circuit (non-measurement circuit) different from the measurement circuit on the measurement circuit. Further, the measuring method using such a terminal is characterized in that the terminal is rotated and the insulator on the measuring circuit is penetrated to bring the terminal into contact with the measuring circuit. In particular, in the case of a terminal in which a portion other than the tip end portion of the terminal is covered with an insulator, not only the insulating layer on the measurement circuit but also the non-measurement circuit can be penetrated, and the terminal can reach the measurement circuit for measurement.

[0006]

By using the needle-like or drill-like measuring terminal as described above, accuracy can be obtained without the need for pretreatment such as lead wire extraction, protective layer removal, and sample preparation process change for any circuit. High measurement can be performed. That is,
If there is a protective layer on the measuring circuit, fix the measuring terminal on top of the point you want to measure and apply load while rotating the terminal to penetrate this into the protective layer and reach the measuring circuit. I do. Here, when the terminal is needle-shaped, it is possible to reach the measurement circuit by simply applying a load without rotating the terminal, but the periphery of the contact portion of the terminal with the measurement target may be compressed and damaged. Therefore, the terminals are smoothly intruded by the rotation, and the frictional heat generated thereby damages only the contact portions to minimize the influence on the surroundings.
Moreover, since the terminal can reach the measuring circuit without applying an unreasonable load by this rotation, the work is efficient and the positional accuracy can be improved. Further, when the terminal is in the form of a drill, the cutting waste can be easily discharged from the groove of the drill in addition to being able to easily enter the object to be measured by rotation.

On the other hand, even when a non-measurement circuit exists on the measurement circuit, the measurement terminal covered with an insulating material except the contact portion between the measurement circuit and the measurement terminal rotates the terminal in the same manner as described above so as to enter the measurement object. . In this case, the penetration depth of the terminal may be adjusted so that only the tip of the terminal without the insulating coating reaches the measuring circuit and the portion with the insulating coating corresponds to the non-measuring circuit. As a result, the electrical characteristics of the desired circuit can be measured without being affected by the presence of other circuits on the measurement circuit.

In any case, since the tip of the terminal and the measuring circuit are in point contact with each other by adjusting the depth of penetration of the terminal, highly accurate measurement is possible. Furthermore, since the characteristic impedance of the measuring terminal can be matched with the characteristic impedance of the cable between the measuring terminal and the measuring device due to its structure, the impedance mismatch at the connecting portion can be eliminated. That is, as shown in FIG. 5, the conductor 24, the insulator 25, the GND circuit 26, and the protective layer 27 are sequentially arranged from the center.
In the case of a coaxial cable equipped with, the characteristic impedance Zo
Is represented by Zo = 138 log (b / a) / √ε _S (ε _S : relative permittivity of insulator, a: conductor radius, b: insulator radius). Therefore, if the characteristic impedance of the cable between the measuring terminal and the measuring device is known, the characteristic impedance of the terminal can be matched to the characteristic impedance of the cable between the measuring terminal and the measuring device by design adjustment of the conductor diameter and the insulator diameter of the terminal. You can do it.

Regarding the material of the terminal, if the object to be measured is limited to the printed circuit, it is not necessary to use a special material, and the conductor at the tip of the measuring terminal is made of copper, iron, stainless steel or the like for the protective layer of the measuring circuit. Any material that has excellent wear resistance and hardness can be used. However, when a coaxial cable is used as the cable between the measuring terminal and the measuring device and impedance matching with it is strictly performed, copper is desirable. However, if it is not strictly necessary, changing only the advanced material does not have a great influence. When the tip end is coated with an insulator, the insulator may be made of a material such as titanium oxide, which has excellent wear resistance and hardness as compared with the non-measurement circuit.

[0010]

EXAMPLES Examples of the present invention will be described below. (Structure of Terminal) As shown in FIG. 1, the terminal of the present invention comprises a cylindrical body 1 having an internal thread formed on the inner circumference and a rotating body 2 having an external thread formed on the outer circumference to be screwed into the cylindrical body 1. The rotating body 2 can be raised and lowered in the cylindrical body by turning the rotating body 2, and a copper terminal 3 is axially built in the center thereof. And terminal 3
Has a needle-like shape and protrudes from the bottom of the rotating body 2. In addition, GN is provided on the outer periphery of the terminal 3 through the insulating layer 4.
A D layer 5 is provided, and the terminals and 3 of these layers 4, 5 are connected by a coaxial cable 6 to a measuring device (not shown). On the other hand, the cylindrical body 1 holding the rotating body 2 is provided with a plurality of viewing windows 7 (see FIG. 2) on the outer periphery thereof, and the terminal tips are aligned by looking through them.

(Measurement Method) A printed circuit board 9 having an insulating protective layer formed on the measurement circuit 8 by means of such terminals 3
2 is measured, the terminals are placed on the substrate as shown in FIG. 2, and the tips of the terminals are arranged so as to be positioned above the measuring circuit 8 through the viewing window 7. Next, the rotating body 2 is rotated and lowered, and the tip of the terminal 3 is inserted into the insulating protective layer 10 as shown in FIG. Then, when the tip of the terminal comes into contact with the measuring circuit 8, the lowering of the rotating body 2 is stopped and the measurement is performed.

Although the needle-shaped terminal is simply used in the above-mentioned example, as shown in FIG. 3B, the needle-shaped terminal 2 may be provided with the insulating coating 11 other than the tip portion. In this case, even if there is a non-measurement circuit 12 on the measurement circuit as shown in the figure,
The protective layer 10 and the non-measurement circuit 11 are penetrated through the terminal 3, the insulation coating 11 corresponds to the position of the non-measurement circuit 12, and the terminal tip is penetrated to a depth such that the measurement circuit 8 is reached. The electrical characteristics of the measuring circuit can be measured. Moreover, even if the tip shape of the terminal is not a needle shape but a drill shape, the electrical characteristics can be easily measured by the same operation. In this case, if the drill penetrates into the insulating protective layer, cutting chips are generated, which can be easily discharged from the drill groove.

(Test Example 1) Using the terminals shown in FIG. 1, a printed circuit having an insulating protective layer 10 on the measuring circuit (FIG. 4A,
Regarding B), various impedances were measured with an LCR meter. For comparison, the insulating protective layer 10 on the measurement circuit
For the printed circuit (FIGS. 4C and 4D) from which a part of is removed, the terminals of FIG. 1 were directly brought into contact with the measuring circuit 8 from the position where the insulating protective layer 10 was removed, and the same measurement was performed. Table 1 shows the measurement results of the inductance and resistance of the signal circuit and the leakage capacitance and leakage conductance between the signal circuit and the GND circuit.

[0014]

[Table 1]

As shown in the same table, the method of the embodiment in which the terminals are inserted into the insulating protective layer for measurement has almost no difference from the method of the comparative example in which a part of the protective layer is removed in advance for measurement. Was confirmed.

(Test Example 2) Next, the entire structure is the same as that shown in FIG. 1, and as shown in FIG. 3B, a terminal having an insulating coating 11 other than the tips is used. The same measurement as in Test Example 1 was performed on the substrate of No. 2. The method using the substrate of FIG. 4A is the example method, and the method using the substrate of FIG. 4C is the comparative method. The results are shown in Table 2.

[0017]

[Table 2]

In the case of this example, it was confirmed that there is almost no difference from the method of the comparative example as in the case of Test Example 1.

(Test Example 3) Further, when the reflected wave between the measurement terminal and the cable was measured by the TDR method for the terminal in Test Example 1, almost no reflection was observed between them and impedance matching was achieved. It was also confirmed that

[0020]

As described above, by using the electrical characteristic measuring terminal according to the present invention, highly accurate measurement can be performed without requiring labor, time, and special technique for measurement. It can be carried out. Therefore, it is effective when the electrical characteristics are measured at high frequency or with higher accuracy in a field such as a printed wiring board where the insulating protective layer is not so robust.

[Brief description of drawings]

FIG. 1 is a sectional view showing an overall configuration of a terminal of the present invention.

FIG. 2 is an explanatory diagram showing a method of using the terminal of the present invention.

FIG. 3 is a cross-sectional view showing a state in which the terminal of the present invention penetrates into an object to be measured and reaches a measurement circuit. (A) shows a case where a needle-shaped terminal is used, (B) shows an insulating coating other than the tip. The case where the needle-shaped terminal is applied to a measurement target having a non-measurement circuit is shown.

FIG. 4 shows a printed circuit board to be measured used in a test example, (A) is a sectional view, (B) is a plan view thereof, and (C).
FIG. 3D is a cross-sectional view of the substrate with a part of the protective layer removed, and FIG.

FIG. 5 is a cross-sectional view of a coaxial cable between a terminal and a measuring device.

FIG. 6 is an explanatory diagram showing a measurement situation by a conventional terminal using a clip.

FIG. 7 is an explanatory diagram showing a measurement situation using a conventional terminal having a needle-shaped tip.

[Explanation of symbols]

1 Cylindrical body 2 Rotating body 3 Terminal 4 Insulating layer 5 G
ND layer 6 Coaxial cable 7 Viewing window 8 Measurement circuit 9 Printed circuit board 10 Insulation protection layer 11 Insulation coating 12 Non-measurement circuit 13
Insulation layer 20 Measurement circuit 21 Lead wire 22 Clip 23 Terminal
24 Conductor 25 Insulator 26 GND circuit 27 Protective layer

Claims (4)

[Claims] 1. A terminal for measuring electrical characteristics, comprising a needle-shaped or drill-shaped terminal and a rotating mechanism thereof. 2. The terminal for measuring electrical characteristics according to claim 1, wherein the terminal other than the tip end portion of the terminal is covered with an insulator. 3. A method for measuring electrical characteristics, which comprises rotating the measuring terminal according to claim 1 or 2 to penetrate an insulator on the measuring circuit and bringing the terminal into contact with the measuring circuit. 4. A measuring terminal according to claim 2, wherein the non-measuring circuit on the measuring circuit and the insulating layer are made to penetrate, and the terminal is brought into contact with the measuring circuit. Measuring method.