JP2001337118A - Probe for measuring impedance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance measuring probe, capable of being readily brought into contact with a circuit to be measured or a ground circuit, without taking much time to make contact, while stabilizing the state of contact between them. SOLUTION: The probe includes an inner conductor 2, having a contact pin 6 for making the circuit 4 to be measured make contact with a circuit board 3, and an outer conductor 1 having a contact part 8 for making contact with the ground circuit 7 of the circuit board 3. The inner conductor 2 is inserted into a probe body 40 and the end of the contact pin 6 is made to protrude from the probe body 40. The outer conductor 1 is provided on the outside of the probe body 40, and the outer conductor 1, and the inner conductor 2 are arranged in the form of coaxial lines. The outer conductor 1 is formed freely movable, relative to the probe body 40 in a direction approximately parallel to the direction along which the contact pin 6 protrudes from the probe body 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe for measuring impedance used for measuring the impedance of a circuit board such as a multilayer printed wiring board.

[0002]

2. Description of the Related Art In a circuit board used for electronic equipment, etc.,
The impedance matching between a circuit provided on a circuit board and a signal transmitted through the circuit is performed. Particularly, in the case of a circuit for transmitting a high-frequency signal (high-speed signal), this impedance matching is important. is there. Therefore, the circuit of the circuit board is designed so that impedance matching with a signal to be transmitted can be obtained, and the circuit board is checked whether the impedance (value) of the circuit is within an allowable range from the design value. Products that have been commercialized and whose circuit impedance falls outside a certain allowable range are discarded as defective products.

Conventionally, when measuring the impedance of a circuit on a circuit board, mainly TDR (Time Domain Ref) is used.
rectometry) method is used. In this method, a pulse or step signal is transmitted to a transmission circuit including a signal circuit (circuit under test) whose impedance is to be measured and a reference ground circuit, and a reflection signal in the transmission circuit is detected and a reflection signal is detected. The impedance value of the transmission circuit (circuit under test) is obtained by using the reflection coefficient obtained from the above.

When transmitting a signal to a transmission circuit, a probe is used as an intermediary for electrically connecting a cable derived from a signal source to the transmission circuit. Such an impedance measuring probe mainly includes a contact pin for a circuit to be measured for contacting a circuit to be measured and a contact pin for a ground circuit for contacting a ground circuit. A macrostrip structure in which a plate-shaped dielectric layer is sandwiched between circuit contact pins, an inner conductor and an outer conductor are arranged in a coaxial line shape, and a contact pin for a circuit under test is drawn from the inner conductor. And a coaxial line structure formed by extracting a ground circuit contact pin from the outer conductor. In any of the impedance measurement probes described above, the tip of the contact pin for the circuit to be measured and the tip of the contact pin for the ground circuit are simultaneously brought into contact with the signal circuit and the ground circuit, respectively, to measure the impedance. Do it.

[0005]

As described above, in the TDR measurement, a signal is input by simultaneously bringing a contact pin for a circuit under test and a contact pin for a ground circuit into contact with a signal circuit (circuit under test) and a ground circuit, respectively. There is a need. Therefore, in a conventional probe having two contact pins, the tip of the contact pin for the circuit to be measured contacts the signal circuit, and the tip of the contact pin for the ground circuit contacts the ground circuit. It is necessary to perform position control by rotating the probe or the like, and there is a problem that it takes time to make contact or the contact state becomes unstable.

In particular, when the area of the portion where the contact pin for the circuit to be measured or the contact pin for the ground circuit is small is small, for example, the signal circuit or the ground circuit is exposed on the end face of the circuit board and the portion for the circuit to be measured When contacting the contact pin or the contact pin for the ground circuit, it is necessary to control the probe position very finely.
The above problem became remarkable.

The present invention has been made in view of the above points, and can easily make contact with a circuit to be measured or a ground circuit, does not require much time to make contact, and stabilizes the state of contact. It is an object of the present invention to provide a probe for impedance measurement that can perform the measurement.

[0008]

According to a first aspect of the present invention, there is provided an impedance measuring probe, comprising: an inner conductor having contact pins for contacting a circuit to be measured on a circuit board; 3, an outer conductor 1 having a contact portion 8 for making contact with the ground circuit 7, the inner conductor 2 is inserted inside the probe body 40, and the tip of the contact pin 6 protrudes from the probe body 40;
The outer conductor 1 is provided outside the probe main body 40, the outer conductor 1 and the inner conductor 2 are arranged in a coaxial line shape, and the outer conductor 1 is probed in a direction substantially parallel to the direction in which the contact pins 6 protrude from the probe main body 40. It is characterized by being formed movably with respect to the main body 40.

A probe A for impedance measurement according to a second aspect of the present invention is the same as the first aspect, except that a front member 42 is provided at the front end of the connecting member 44 having a cushioning property and the rear end of the connecting member 44 is provided at the rear end. The outer conductor 1 is formed by providing the rear member 43.

According to a third aspect of the present invention, in addition to the configuration of the second aspect, the impedance measuring probe A is characterized in that the connecting member 44 is formed by a spring.

A probe A for impedance measurement according to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, further comprises a contact portion 8 formed in a frame shape continuous in the circumferential direction of the outer conductor 1. It is characterized by comprising.

A probe A for impedance measurement according to a fifth aspect of the present invention is characterized in that, in addition to any one of the first to fourth aspects, the contact portion 8 is formed of pressurized conductive rubber. Things.

A probe A for impedance measurement according to a sixth aspect of the present invention is characterized in that, in addition to any one of the first to fourth aspects, the contact portion 8 is formed of conductive rubber. It is.

A probe A for impedance measurement according to a seventh aspect of the present invention, in addition to the configuration according to any one of the first to sixth aspects, is configured such that the contact pin 6 is formed so as to be insertable into and removable from the probe main body 40. It is characterized by the following.

An impedance measuring probe A according to an eighth aspect of the present invention is characterized in that, in addition to any one of the first to seventh aspects, the contact pin 6 has a cushioning property. is there.

A probe A for impedance measurement according to a ninth aspect of the present invention is characterized in that, in addition to any one of the first to eighth aspects, the contact pin 6 is formed so as to be expandable and contractable by a spring 23. Is what you do.

According to a tenth aspect of the present invention, there is provided an impedance measuring probe A in which, in addition to any one of the first to ninth aspects, the tip of the contact portion 8 is formed to have a substantially triangular cross section. It is assumed that.

According to an eleventh aspect of the present invention, in addition to the configuration of any one of the first to tenth aspects, the probe A for impedance measurement is formed by forming the tip of the contact portion 8 into a substantially semicircular cross section. It is a feature.

A probe A for impedance measurement according to a twelfth aspect of the present invention, in addition to any one of the first to eleventh aspects, further comprises a dielectric layer 9 between the inner conductor 2 and the outer conductor 1.
And the dielectric layer 9 is formed of a material having a low dielectric constant and a low dielectric loss tangent.

[0020]

Embodiments of the present invention will be described below.

The probe A for impedance measurement of the present invention
As shown in FIG. 1, is formed to include an outer conductor 1, an inner conductor 2, and a probe main body 40, and is designed to have the same impedance as a coaxial cable described later to achieve impedance matching.

As shown in FIG. 2A, the outer conductor 1 includes a front member 42 forming a front portion, a rear member 43 forming a rear portion, and a connecting member 4 provided between the front member 42 and the rear member 43.
4. The front member 42 is made of any conductive metal material such as copper, stainless steel, and nickel, which is generally used for electric components, or any material having the same conductivity and the same shape stability as the metal material. Can be formed. The front member 42 is formed in a substantially cylindrical shape with a front insertion hole 56 penetrating in the front-rear direction substantially at the center thereof. A rear portion of the front member 42 is formed as a connecting portion 53, and a plurality of ridges 54 having a substantially triangular cross section are provided on the outer peripheral surface of the connecting portion 53 over the entire circumference.

The rear member 43 is formed of the above-described conductive metal material or the like, and has a rear insertion hole 57 penetrating in the front-rear direction at a substantially central portion thereof and is formed in a substantially cylindrical shape. Have been. Also, the front part of the rear member 43 is
A plurality of ridges 59 having a substantially triangular cross section are provided on the outer peripheral surface of the coupling portion 58 so as to protrude over the entire circumference. Further, on the outer peripheral surface of the rear member 43, a mounting piece 18 for mounting the present invention to another member (for example, a cylinder described later) is provided so as to protrude over the entire circumference. The connecting member 44 is formed of the above-described conductive metal material or the like,
In addition, a coil-shaped spring having cushioning properties (elasticity) can be used as the connecting member 44.

Then, the connecting portion 53 of the front member 42 is inserted and fitted inside the front end of the connecting member 44, and the connecting portion 58 of the rear member 43 is inserted and fitted inside the rear end of the connecting member 44. By providing the front member 42 at the front end of the connecting member 44 and the rear member 43 at the rear end of the connecting member 44, the outer conductor 1 in which the front member 42 and the rear member 43 are connected by the connecting member 44 can be formed. it can. At this time, the ridges 54 and 59 bite into the connecting member 44, so that the front member 42 and the connecting member 44 and the rear member 43 and the connecting member 44 can be firmly engaged. The front insertion hole 56, the rear insertion hole 57, and the space inside the connecting member 44 communicate with each other, so that an insertion hole 60 penetrating in the front-rear direction is formed inside the outer conductor 1. Further, the front member 42 and the rear member 43 are electrically connected by a connecting member 44.

A contact portion 8 is provided on the front surface of the outer conductor 1 so as to protrude therefrom. The contact portion 8 is formed in a substantially circular frame shape (substantially cylindrical shape) using conductive rubber.
By inserting a rear portion of the contact portion 8 into a groove 55 formed in the front surface of the outer conductor 1 so as to surround the front opening of the outer conductor 1, the contact portion 8 extends outward so as to surround the front opening of the insertion hole 60. It is attached to the front member 42 of the conductor 1. Therefore, the contact portion 8 is formed in a substantially circular frame shape continuous in the circumferential direction of the outer conductor 1. The conductive rubber has a lower resistance value than the normal rubber and has the same conductivity as the conductive metal even when there is no distortion due to pressure or the like, and the change in the resistance value due to compression is small. Things. Specifically, "EC-A" manufactured by Shin-Etsu Chemical Co., Ltd.
Etc. can be used. Further, the contact portion 8 can be formed by using a pressurized conductive rubber instead of the conductive rubber. Pressurized conductive rubber usually has the same conductive properties as general rubber, but when compressed, the resistance value decreases, leading to the same conductivity as conductive metals. is there. Specifically, Nippon Synthetic Rubber Co., Ltd.
"PCR" or the like can be used. When the contact portion 8 is formed of pressurized conductive rubber, a sufficient pressure (contact pressure) is applied to the ground portion 7 so that the resistance value of the contact portion 8 decreases to a sufficiently small value in order to obtain high measurement accuracy. It is necessary to push with.

In the embodiment shown in FIG. 1, the contact portion 8 is formed to have a substantially rectangular cross section, and the tip end surface of the contact portion 8 is made flat. However, as shown in FIG. The contact portion 8 can be formed in a substantially triangular shape, so that the tip of the contact portion 8 can be sharpened and the area can be reduced. Ground circuit 7
And the contact portion 8 and the ground circuit 7 can be contacted with a relatively strong force. Further, as shown in FIG.
Can be formed in a substantially semicircular cross section, so that the tip of the contact portion 8 has a curved surface, so that even when the contact portion 8 comes into contact with the ground circuit 7, damage such as damage to the ground circuit 7 is relatively reduced. Can be.

It is to be noted that the contact portion 8 may not be protruded from the front surface of the outer conductor 1 as described above, and a flat surface around the insertion hole 60 on the front surface of the outer conductor 1 may be formed as the contact portion 8. Good. In this case, the risk of damaging (damaging) the ground circuit 7 is reduced as compared with the case where the contact portions 8 are formed so as to protrude. However, in order to easily and stably contact the contact portion 8 to the ground circuit 7 (in the case of the ground circuit 7 in which the contact portion 8 is in contact with a narrow portion), the contact portion 8 is improved.
Is preferably formed to project from the front surface of the outer conductor 1. Also, if the contact portion 8 made of conductive rubber is protruded and provided integrally with the outer conductor 1, the characteristic impedance deviates from the design value at the contact portion 8 and impedance mismatch occurs, leading to a decrease in the measurement accuracy of the TDR measurement. Therefore, it is preferable that the contact portion 8 is formed as thin as possible (with a small protrusion size). Also, instead of forming the contact portion 8 with conductive rubber or pressurized conductive rubber,
The same material as the front member 42 may be formed integrally with the front surface of the front member 42.

The probe body 40 is formed of the above-mentioned conductive metal material or the like. As shown in FIG.
The probe main body 40 has a front portion formed as an outer conductor mounting portion 50 that is long in the front-rear direction.
0 is formed as a cable connection portion 51 having a larger outer diameter than the outer conductor attachment portion 50. Probe body 4
0 has a through-hole 11 formed so as to penetrate the outer conductor mounting portion 50 and the cable connecting portion 51,
The opening of the through hole 11 at the front end face of the outer conductor mounting portion 50 is formed as a pin protrusion 15, and the opening of the through hole 11 at the rear end face of the cable connection portion 51 of the probe body 40 is formed as a cable insertion port 16. Have been. A thread 17 is formed on the outer peripheral surface of the rear part of the probe main body 40, and a connector provided at an end of a coaxial cable described later can be screwed into the thread 17. Can be easily connected.

The inner conductor 2 includes the contact pins 6, the connection conductor 30, and the fixed socket 22. The contact pin 6 is formed of a conductive metal such as copper or nickel, and as shown in FIG.
A cylindrical support socket 2 having an open front surface and a closed rear surface
4 and a spring 23 such as a coil spring, which are integrally formed. The pin body 21 is inserted into the support socket 24 with its tip protruding from the front opening of the support socket 24, and is formed in a state where the support socket 24 covers other than the tip of the pin body 21. The spring 23 is provided between the rear end of the pin body 21 and the bottom surface of the support socket 24. Further, the pin body 21 is formed to be slidable in the front-rear direction with respect to the support socket 24. In addition, when the outer peripheral surface of the pin body 21 and the inner peripheral surface of the support socket 24 come into contact with each other,
The pin body 21 and the support socket 24 are electrically connected. The tip of the pin body 21 may be sharply pointed.

The above-mentioned contact pin 6 is
Are formed so as to be slidable in the front-rear direction with respect to the support socket 24, so that the pin body 21 protrudes greatly from the support socket 24 and the pin body 21 is
3 so as to be able to expand and contract with a state in which it is inserted into the support socket 24 deeply against the elastic force of 3. Further, in the contact pin 6 described above, the spring 23 is provided between the rear end of the pin body 21 and the bottom surface of the support socket 24,
Since the pin body 21 has cushioning properties, the pin body 21 can be elastically contacted with the circuit 4 to be measured on the circuit board 3. The cushioning property in the present invention means that when measuring the impedance of the circuit 4 to be measured on the circuit board 3, excessive load is applied to the tip of the pin body 21, the tip of the contact portion 8 or the contact portion of the contact pin 6 of the circuit 4 to be measured. It refers to the property of absorbing a weight above a certain threshold to prevent it. In the contact pin 6, the cushioning property is exhibited by the contraction of the spring 23, and the pin body 2
1 and reduction of damage to circuit under test 4 and pin body 2
1 can improve the contact with the circuit under test 4.

The connection conductor 30 and the fixed socket 22 are for electrically connecting the contact pin 6 and the core wire of the coaxial cable inserted into the through hole 11 from the cable insertion port 16, and include the contact pin 6 and the outer side. It can be formed of the same material as the conductor 1. The connection conductor 30 is provided with a socket connection hole 31 which is opened on the front surface thereof.
The rear part of the fixed socket 22 is inserted into the socket connection hole 31, and the fixed socket 22 is attached to the front side of the connection conductor 30. The fixed socket 22 has a cylindrical shape with an open front surface and a closed rear surface, has an inner diameter slightly larger than the outer diameter of the support socket 24 of the contact pin 6, and has substantially the same length as the support socket 24. It is formed. The connection conductor 30 is provided with a core wire connection hole 32, and the core wire connection hole 32 is formed so as to open to the rear surface of the connection conductor 30. Then, by inserting the rear portion of the contact pin 6 (the portion of the support socket 24) inside the fixed socket 22, the contact pin 6 is removably attached to the fixed socket 22 and connected to the contact pin 6 and the fixed socket 22. Conductor 30
Are electrically connected to each other to form the inner conductor 2.

The probe A for impedance measurement of the present invention is formed by attaching the outer conductor 1 and the inner conductor 2 to a probe body 40. The outer conductor 1 is attached to the outside of the outer conductor attachment portion 50 of the probe main body 40 by inserting the outer conductor attachment portion 50 of the probe main body 40 into the insertion hole 60 from the rear side. At this time, the outer peripheral surface of the outer conductor mounting portion 50 and the front member 4
2, the outer peripheral surface of the outer conductor mounting portion 50 and the inner peripheral surface of the rear member 43 are in close contact with each other, so that the probe body 40 and the outer conductor 1 are electrically connected. Will be. The outer conductor 1 is provided with an outer conductor mounting portion 5.
It is attached to the probe main body 40 so as to slide in the front-rear direction along 0.

On the other hand, as shown in FIG. 2B, the inner conductor 2 is in a state in which the tip of the pin body 21 of the contact pin 6 is projected from the pin protrusion 15 to the outside (front side) of the probe body 40. That is, the fixed socket 22 and the connection conductor 30
Are held in the through-hole 11 of the probe main body 40 in a state where they are arranged in the through-hole 11. The inner conductor 2 is disposed along the center line of the probe main body 40 passing through the through-hole 11, so that the inner conductor 2, the outer conductor 1, and the probe main body 40 have a coaxial line shape (concentric shaft shape). ). Further, the tip of the pin body 21 of the contact pin 6 is made to protrude forward by about 3 mm from the front surface of the probe body 40.
Can be set arbitrarily. Further, since the contact pin 6 is formed so as to be extendable and contractible, when a load is applied from the front side, the pin main body 21 moves in the front-rear direction with respect to the probe main body 40 of the outer conductor 1. The core connection hole 32 of the connection conductor 30 faces the cable insertion port 16 of the through hole 11 and is in communication with the cable insertion port 16.

The dielectric layer 9 is formed between the outer peripheral surface of the fixed socket 22 of the inner conductor 2 and the outer peripheral surface of the connection conductor 30 and the inner peripheral surface of the probe body 40 (the wall surface of the through hole 11). Have been. The dielectric layer 9 secures insulation between the outer conductor 1 and the probe main body 40 and the inner conductor 2 adjacent to each other with the dielectric layer 9 interposed therebetween, and also holds the fixed socket 22 and the connection conductor 30 of the inner conductor 2 in the through hole 11. Things. The dielectric layer 9 is preferably formed of a material having a low dielectric constant and a low dielectric loss tangent in order to improve characteristics at high frequencies.
For example, fluorine resin such as PTFE (polytetrafluoroethylene), PPO (polyphenylene oxide),
Although a resin such as PPE (polyphenylene ether) can be used, it is necessary to use any material having a low dielectric constant and a low dielectric loss tangent similar to that of the fluororesin, and having the same shape stability as the fluororesin. it can. When the inner conductor 2 is held by the dielectric layer 9 as described above, the fixed socket 22 and the connection conductor 30 are fixed in the through hole 11, but the contact pins 6 are formed so as to be able to be inserted into and removed from the fixed socket 22. As a result, the contact pin 6 can be inserted and removed from the probe main body 40. Therefore, the contact pin 6 whose life has elapsed due to wear of the pin main body 21 due to contact with the circuit 4 to be measured is pulled out from the fixed socket 22, and a new contact pin 6 is inserted into the fixed socket 22 so that only the contact pin 6 is inserted. Can be replaced. That is, when measuring the impedance, the tip of the contact pin 6 (the pin main body 21) repeatedly contacts the circuit 4 to be measured on the circuit board 3;
Deterioration of the contact pin 6 is unavoidable, and the conventional probe has to be replaced with the entire probe, resulting in a wasteful problem.
Since only one can be replaced, the running cost can be reduced.

A stable cavity in which the contact pin 6 can be directly accommodated by the dielectric layer 9 alone is formed, and the rear portion of the contact pin 6 is securely brought into contact with the connection conductor 30 so that the fixed socket 22 is not used. be able to. Further, a spring 23 may be provided between the contact pin 6 and the connection conductor 30 or the outer conductor 1.

The impedance measuring probe A of the present invention formed as described above is electrically connected via a coaxial cable to an oscilloscope or an impedance measuring instrument provided with an input signal generator for generating a signal for measurement. Things. In connecting the coaxial cable to the impedance measuring probe A, one end of the coaxial cable is inserted into the through hole 11 from the cable insertion port 16, and the core (center conductor) at one end of the inserted coaxial cable is connected to the inner conductor 2.
And the coated conductor (outer conductor) at one end of the coaxial cable inserted into the through-hole 11 is brought into contact with the wall surface of the through-hole 11,
Connect the connector provided at the end of the coaxial cable to the probe body 4
The thread 17 is screwed into the thread 17. By connecting the end of the coaxial cable to the impedance measuring probe A in this manner, the core wire of the coaxial cable can be electrically connected to the pin body 21 of the contact pin 6 and via the probe body 40. The sheath conductor of the coaxial cable can be electrically connected to the outer conductor 1. The other end of the coaxial cable is connected to an impedance measuring device.

Probe A for Impedance Measurement of the Present Invention
Can be used for characteristic impedance measurement by the TDR method or the like. In this case, the end of the circuit 4 to be measured and the end of the ground circuit 7 on the circuit board 3 can be brought into contact with the tip of the contact pin 6 and the tip of the contact portion 8 so that the surface of the circuit board 3 or the circuit board 3 can be contacted. 3 is formed to be exposed from the end face. The circuit under test 4 may be a signal circuit to which a signal is actually transmitted, or may be a test pattern for measuring impedance.

FIG. 5 shows an example of a method for measuring the impedance of the circuit 4 to be measured on the circuit board 3 using the impedance measuring probe A of the present invention. In this method, the circuit under test 4 and the ground circuit 7 are exposed on the surface of the circuit board 3. A ground circuit 7 is formed on the surface of the circuit board 3 and a circuit 4 to be measured is formed inside the circuit board 3, and a measurement opening 33 extending from the surface of the circuit board 3 to the circuit 4 to be measured. Are formed on the circuit board 3.

The measurement of the impedance of the circuit under test 4 on the circuit board 3 is performed as follows. First, as shown in FIG. 5A, the outer conductor 1 is retracted with respect to the probe main body 40. At this time, it is preferable that the outer conductor 1 be retracted until the rear end of the outer conductor 1 comes into contact with the front end of the cable connection portion 51.
A portion of the contact pin 6 protruding from the probe main body 40 can be prevented from being surrounded by the contact portion 8 provided on the outer conductor 1, and a large space for visually recognizing the tip of the contact pin 6 can be secured. Thus, the tip of the contact pin 6 can be easily brought into contact with the circuit 4 to be measured.

Next, with the tip of the contact pin 6 directed downward, the entire probe A for impedance measurement is advanced to approach the circuit board 3 from above, and contacts the measurement opening 33 from the surface side of the circuit board 3. The pin 6 is inserted and the tip of the contact pin 6 is brought into contact with the surface of the end of the circuit 4 to be measured. Next, as shown in FIG. 5B, the outer conductor 1 is advanced (moved downward) with respect to the probe main body 40, and the tip of the contact portion 8 is connected to the ground circuit 7 at the periphery of the measurement opening 33. Touch the edges. In this way, the impedance of the circuit under test 4 can be measured.

FIG. 6 shows another example of a method for measuring the impedance of the circuit 4 to be measured on the circuit board 3 using the impedance measuring probe A of the present invention. In this method, the end of the circuit under test 4 and the end of the ground circuit 7 are exposed on the end surface (side surface) of the circuit board 3. A ground circuit 7 is formed on the surface of the circuit board 3 and a circuit under test 4 is formed inside the circuit board 3. The ground circuit 7 may be provided inside the circuit board 3.

The measurement of the impedance of the circuit under test 4 on the circuit board 3 is performed as follows. First, as shown in FIG. 6A, the outer conductor 1 is retracted with respect to the probe main body 40. Next, the entirety of the probe A for impedance measurement is advanced while the tip of the contact pin 6 is directed to the side surface of the circuit board 3 so that the circuit board 3
And the tip of the contact pin 6 is brought into contact with the surface of the end of the circuit 4 to be measured. Next, as shown in FIG. 6B, the outer conductor 1 is moved forward (moved to the circuit board 3 side) with respect to the probe main body 40 so that the tip of the contact portion 8 contacts the surface of the end of the ground circuit 7. Let it. In this way, the impedance of the circuit under test 4 can be measured.

The entire movement of the impedance measuring probe A and the movement of the outer conductor 1 as described above may be operated by hand, or a driving device such as a cylinder may be used. Further, since the impedance measurement probe A is brought into contact with the very small end faces of the circuit under test 4 and the ground circuit 7, the position of the impedance measurement probe A and the outer conductor 1 is adjusted while observing the contact portion in an enlarged manner using a camera or the like. Is preferably performed. In the TDR measurement, it is preferable to treat all conductive parts of the circuit board 3 other than the circuit under test 4 as grounds (circuits) in order to perform impedance measurement with high accuracy and stability.
Since the contact portion 8 is formed so as to surround the entire circumference of the contact pin 6, the tip of the contact portion 8 can be simultaneously contacted with a plurality of conductive portions near the end of the circuit 4 to be measured. A highly stable impedance measurement can be performed. Therefore, the pitch (interval) between the pin body 21 of the contact pin 6 and the contact portion 8
Is preferably formed to coincide with the pitch between the circuit under test 4 and the ground circuit 7.

In the impedance measuring probe A of the present invention, the inner conductor 2 having the contact pins 6 for contacting the circuit under test 4 and the outer conductor 1 are arranged in a coaxial line shape. Is the circuit under test 4
In order to bring the contact portion 8 into contact with the ground circuit 7, it is sufficient to perform only horizontal or vertical position control without performing position control in the rotation direction with the contact pin 6 as an axial direction. The circuit 4 and the ground circuit 7 can be easily brought into contact with each other, and it does not take much time to make the contact, and the contact state can be stabilized.

Further, the inner conductor 2 is inserted inside the probe main body 40 and the tip of the contact pin 6 protrudes from the probe main body 40, and the outer conductor 1 is provided outside the probe main body 40 to form the outer conductor 1 and the inner conductor 2. Are arranged in a coaxial line shape, and the outer conductor 1 is formed movably with respect to the probe main body 40 in a direction substantially parallel to the direction in which the contact pins 6 protrude from the probe main body 40. The movement of the probe body 40 when contacting the measurement circuit 4 and the movement of the external conductor 1 when the tip of the contact portion 8 contacts the ground circuit 7 can be performed separately, and the tip of the contact pin 6 is covered. The timing for making contact with the measuring circuit 4 and the timing for bringing the tip of the contact portion 8 into contact with the ground circuit 7 are easily and separately controlled. It is intended that easy to perform the measurement of the impedance can.

Further, by forming the contact portion 8 with rubber of pressurized conductive rubber or conductive rubber, the contact portion 8 is formed.
Has a cushioning property, whereby even if the ground circuit 7 of the circuit board 3 has roughness such as unevenness, the contact portion 8 can be deformed and brought into close contact with the roughness, and no contact failure occurs. And the damage to the ground circuit 7 can be reduced. Further, since the contact portion 8 is formed over substantially the entire front surface of the outer conductor 1 from which the contact pins 6 are projected, the change in the pitch between the end of the circuit 4 to be measured and the end of the ground circuit 7 can be prevented. It is possible to respond with a certain width.

Further, the connecting member 44 having cushioning properties
Is provided in the middle to form the outer conductor 1, so that even if the surface or side end surface of the circuit board 3 is distorted by cutting or polishing when the circuit board 3 is formed, the contact portion 8 can be brought into contact with the ground circuit 7. The outer conductor 1 is elastically deformed at the connecting member 44 so that the front member 42 and the contact portion 8 can follow the above-described distortion, and the state of contact between the contact portion 8 and the ground circuit 7 is stabilized. Can be done.

When the contact portion 8 is made of a conductive rubber or a conductive rubber, the resistance value of the contact portion 8 is an important parameter for increasing the measurement accuracy.
When the contact portion 8 is formed of pressurized conductive rubber, it is possible to reduce the resistance value by applying sufficient contact pressure. However, when the conductive rubber is used, the rate of change of the resistance value is small. It is preferable to use a conductive rubber having a contact portion 8 originally having a resistance value as small as possible. In order to measure impedance with sufficiently high accuracy, the resistance value of the contact portion 8 must be at least 1 Ω or less. However, since the resistance value of the contact portion 8 also depends on its thickness, it is preferable to make the contact portion 8 as thin as possible in consideration of the balance with the reduction in cushioning property.

The contact portion 8 is provided on the front surface of the outer conductor 1.
Is provided integrally with each other, in a time axis region corresponding to a region extending from a tip of the contact pin 6 of the probe to a shallow portion of the circuit under test 4 in a waveform obtained by TDR measurement, a waveform disturbance due to impedance mismatch occurs. Sometimes. The disturbance of the waveform is attenuated as the reference time axis coordinate becomes deeper in the measuring circuit 4. Therefore, when reading the characteristic impedance of the circuit under test 4, the value is read at a stable portion of the waveform in the time axis coordinate corresponding to a slightly deeper portion in the circuit under test 4, and the impedance value of the circuit 4 to be measured is read. It is preferred that

[0050]

As described above, according to the first aspect of the present invention, an inner conductor having a contact pin for making contact with a circuit to be measured on a circuit board and a contact for making contact with a ground circuit of the circuit board are provided. And an outer conductor having a portion, wherein the inner conductor is inserted inside the probe main body, the tip of the contact pin protrudes from the probe main body, the outer conductor is provided outside the probe main body, and the outer conductor and the inner conductor are coaxial. Since the outer conductor is formed movably with respect to the probe body in a direction substantially parallel to the direction in which the contact pins protrude from the probe body in the line shape, the contact pins are attached to the circuit to be measured on the circuit board in the TDR measurement. , When contacting the contacts with the ground circuit,
Only horizontal or vertical position control is required without position control in the rotation direction with the contact pin as the axial direction, and the circuit to be measured and the ground circuit can be easily contacted. And the contact state can be stabilized.
Further, when the contact is made from the end face of the circuit board, it is possible to make contact with a plurality of conductors of the circuit board, which are grounds, so that more accurate impedance measurement can be performed. In addition, the movement of the probe body when the tip of the contact pin contacts the circuit to be measured and the movement of the external conductor when the tip of the contact portion contacts the ground circuit can be performed separately. Can be easily controlled separately from the timing at which the contact is brought into contact with the circuit to be measured and the timing at which the tip of the contact portion is brought into contact with the ground circuit, so that the impedance can be easily measured.

According to the invention of claim 2 of the present invention, the outer conductor is formed by providing the front member at the front end of the connecting member having cushioning property and providing the rear member at the rear end of the connecting member. Even if the surface or side end surface is distorted due to cutting or polishing during the production of the circuit board, when the contact portion is brought into contact with the ground circuit, the outer conductor is elastically deformed at the connecting member and the front member and the contact portion Can follow the above-mentioned distortion, and the state of contact between the contact portion and the ground circuit can be stabilized.

According to the third aspect of the present invention, since the connecting member is formed by a spring, the connecting member having cushioning properties can be easily formed.

According to the fourth aspect of the present invention, since the contact portion is formed in a frame shape continuous in the circumferential direction of the outer conductor, the contact area of the contact portion with the ground circuit can be increased, and the TDR measurement can be performed. In this case, the contact between the ground circuit and the contact portion can be performed more stably.

Further, according to the invention of claim 5 or 6 of the present invention, since the contact portion is formed of pressurized conductive rubber or conductive rubber, even if the ground circuit of the circuit board has roughness such as irregularities, it can cope with it. The contact portion of the ground circuit can be deformed and brought into close contact, so that contact failure does not occur. In addition, the change in the pitch between the end of the circuit to be measured and the end of the ground circuit can be prevented. Can be handled with a certain width.

According to the invention of claim 7 of the present invention, since the contact pins are formed so as to be able to be inserted into and removed from the probe main body, only the contact pins having a relatively short life can be replaced, and the replacement of the entire probe is reduced. As a result, the running cost can be reduced.

According to the invention of claim 8 of the present invention, since the contact pin has a cushioning property, the pressure at the time of contact with the circuit to be measured can be absorbed by the cushioning property of the contact pin, and the contact pin has a cushioning property. It is possible to reduce damage and damage to a contact portion of a circuit to be measured.

According to the ninth aspect of the present invention, since the contact pins are formed to be extendable and contractible by a spring, cushioning properties can be easily imparted to the contact pins.

According to the tenth aspect of the present invention, since the tip of the contact portion is formed to have a substantially triangular cross section, the area of the tip of the ground circuit contact portion can be reduced, and a relatively strong contact can be obtained. Can be done.

According to the eleventh aspect of the present invention, since the tip of the contact portion is formed in a substantially semicircular cross section, damage to the ground circuit can be reduced.

According to a twelfth aspect of the present invention, since a dielectric layer is provided between the inner conductor and the outer conductor and the dielectric layer is formed of a material having a low dielectric constant and a low dielectric loss tangent, loss in a high frequency region is reduced. Can be reduced, and the characteristics of the probe can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

FIG. 2A is a perspective view showing an outer conductor according to the embodiment, and FIG.
FIG. 2 is a perspective view showing a probe main body and contact pins of the same.

FIGS. 3 (a) and 3 (b) are cross-sectional views showing a contact portion of the above.

FIG. 4 is a sectional view showing the contact pin according to the first embodiment;

FIGS. 5A and 5B are cross-sectional views showing an example of the measuring method according to the first embodiment.

FIGS. 6A and 6B are cross-sectional views showing another example of the measuring method according to the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer conductor 2 Inner conductor 3 Circuit board 4 Circuit under test 6 Contact pin 7 Ground circuit 8 Contact part 9 Dielectric layer 23 Spring 40 Probe body 42 Front member 43 Rear member 44 Connecting member A Impedance measurement probe

Continued on the front page (72) Inventor Tatsumi Iwaishi 1048 Kadoma Kadoma, Osaka Pref.Matsushita Electric Works, Ltd. (72) Inventor Masanobu Taketomi 1048 Odaka Kadoma, Kadoma, Osaka Pref.Matsushita Electric Works, Ltd. (72) Invention Person Mitsuhide Nagaso 1048 Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Works Co., Ltd.

Claims (12)

[Claims] The probe body includes an inner conductor having a contact pin for making contact with a circuit to be measured on a circuit board, and an outer conductor having a contact portion for making contact with a ground circuit of the circuit board. The inner conductor is inserted inside and the tip of the contact pin protrudes from the probe main body.The outer conductor is provided outside the probe main body, and the outer conductor and the inner conductor are arranged in a coaxial line shape, and the contact pin protrudes from the probe main body. An impedance measuring probe, wherein an outer conductor is formed to be movable relative to a probe body in a direction substantially parallel to the direction. 2. The impedance according to claim 1, wherein an outer conductor is formed by providing a front member at a front end of the connection member having cushioning properties and providing a rear member at a rear end of the connection member. Measurement probe. 3. The impedance measuring probe according to claim 2, wherein the connecting member is formed by a spring. 4. The impedance measuring probe according to claim 1, wherein the contact portion is formed in a frame shape continuous in the circumferential direction of the outer conductor. 5. The impedance measuring probe according to claim 1, wherein the contact portion is formed of pressurized conductive rubber. 6. The impedance measuring probe according to claim 1, wherein the contact portion is formed of conductive rubber. 7. The method according to claim 1, wherein the contact pins are formed so as to be able to be inserted into and removed from the probe main body.
7. The impedance measuring probe according to any one of items 1 to 6. 8. The impedance measuring probe according to claim 1, wherein the contact pin has a cushioning property. 9. The impedance measuring probe according to claim 1, wherein the contact pin is formed to be expandable and contractable by a spring. 10. The impedance measuring probe according to claim 1, wherein a tip of the contact portion is formed in a substantially triangular cross section. 11. The impedance measuring probe according to claim 1, wherein a tip of the contact portion is formed in a substantially semicircular cross section. 12. The method according to claim 1, wherein a dielectric layer is provided between the inner conductor and the outer conductor, and the dielectric layer is formed of a material having a low dielectric constant and a low dielectric loss tangent. The probe for measuring impedance described in 1.