WO2001073451A1

WO2001073451A1 - High frequency circuit impedance measuring probe for inner-layer-containing laminated sheet used for multi-layer printed board

Info

Publication number: WO2001073451A1
Application number: PCT/JP2001/002570
Authority: WO
Inventors: Toru Nakashiba; Yukio Matsushita; Tatsumi Iwaishi; Masanobu Takedomi; Mitsuhide Nagaso; Motoyuki Akamatsu
Original assignee: Matsushita Electric Works, Ltd.
Priority date: 2000-03-28
Filing date: 2001-03-28
Publication date: 2001-10-04
Also published as: AU4458801A; TWI271521B

Abstract

A probe capable of simply being positioned with respect to a laminated sheet and measuring a high impedance reliably, comprising a probe needle for contacting an internal conductor layer forming a high frequency circuit inside the laminated sheet, and a ground electrode for contacting another conductor layer separate from this internal conductor layer, wherein the probe needle is connected to an external impedance measuring instrument and is used to send a high-frequency signal to the internal conductor layer from the instrument and transmit a high-frequency signal reflected off the layer to the measuring instrument. A contact end edge of the ground electrode to contact the other conductor layer is formed into an annular shape coaxially surrounding the probe needle to allow some portion of the annular contact end edge surrounding the probe needle to contact the other conductor layer when the probe needle is allowed to contact a portion of the internal conductor layer.

Description

Description Probe for measuring high frequency circuit impedance of laminated board with inner layer circuit used for multilayer printed circuit board

The present invention relates to a probe used for measuring a high-frequency circuit impedance of a laminated board containing an inner circuit used for a multilayer printed board.

Background art

In recent years, multilayer printed circuit boards have been widely used to realize high-frequency circuits incorporated in electronic devices such as mobile telephone terminals, and various types of basic circuits are formed by processing a laminated board having an inner layer circuit formed in advance in an inner layer. A multilayer printed board is manufactured. The laminated board with the inner layer circuit is prepared as follows. First, the first conductor layer and the second conductor layer are laminated over the entire upper and lower surfaces of the insulating base material, a basic high-frequency circuit is formed on the first conductor layer, and the second conductor layer is used as a ground layer. Then, the third conductor layer is formed on the entire surface of the first conductor layer via the first insulating layer. Alternatively, when the second conductor layer is a ground layer having a predetermined circuit pattern, a fourth conductor layer is formed over the entire surface of the ground layer via a second insulating layer. The laminated board with the inner layer circuit of the outermost unprocessed conductor layer manufactured in this manner is then formed with a circuit on the unprocessed conductor layer in accordance with various circuit design requirements. Therefore, in order to improve the yield, it is necessary to inspect non-defective products of the laminated board with the inner layer circuit before the final circuit formation. In particular, in high-frequency circuits, impedance matching with high-frequency signals flowing through the circuit is required, and it is necessary to check that the predetermined impedance is within the allowable range of the design value. . If the impedance of the circuit is out of a certain allowable range, it is discarded as defective. In particular, since the manufacture of the laminated board with the inner circuit and the final circuit formation are often performed by different manufacturers, it is required that such non-defective inspection be performed.

Conventionally, when measuring the impedance of a circuit on a circuit board, the main TDR (Time Domain Refrectometry) method has been used. According to this method, a high-frequency incident signal such as a pulse or a step signal is transmitted to a test conductor formed on an inner conductor layer using this conductor layer and another conductor layer as a ground, and the test conductor (inner signal circuit) is formed. Then, the impedance value of the cost conductor (inner layer signal circuit) is obtained by using the reflection coefficient obtained from the reflection signal while detecting the reflection signal. What is required for the above impedance measurement is a measuring instrument for TDR, a cable for signal transmission, and a probe. The probe is used as an intermediary for electrically connecting the measuring instrument and the cable connected to the test conductor to the test conductor. Electrical design is performed by matching impedance with cables and test conductors.

Two types of this probe have been proposed. One is a microstrip structure, which has a signal pin that contacts a test conductor (signal circuit) and a ground pin that contacts a conductor layer, which is a different layer from the test conductor. The probe is separated by a dielectric layer, and the other is of a coaxial structure, in which the center conductor is surrounded by an outer conductor via a dielectric layer, and the signal pin and the ground are respectively separated from the center conductor and the outer conductor. The pins protrude. Both types of probes require that the signal pin be in contact with the test conductor and the ground pin be in contact with another conductor layer at the same time, so that the test conductor and the other conductor must match the distance between the pins. layer It is necessary to determine the position of the probe in advance, and to precisely control the position of the probe accordingly.If the distance between the test conductor and another conductor layer shifts or the position control of the probe shifts even slightly, However, there is a problem that accurate impedance measurement cannot be performed. This problem is particularly important when the laminated board is small and thin, making accurate impedance measurement difficult. Disclosure of the invention

The present invention has been made in order to solve the above problems, and has as its object to provide a probe that can easily perform positioning with respect to a laminate and that enables highly reliable impedance measurement. Things.

The impedance measuring probe according to the present invention is for measuring the high-frequency circuit impedance of a laminated board containing an inner-layer circuit used for a multilayer printed circuit board, and comes into contact with an internal conductor layer forming a high-frequency circuit in the laminated board. And a ground electrode for contacting the inner conductor layer and another conductor layer.The probe needle is connected to an external impedance measuring instrument, and a high-frequency signal from the probe needle is transmitted to the inner conductor layer. It is used to transmit the high-frequency signal transmitted and reflected from it to the measuring instrument. The contact edge of the ground electrode that comes into contact with another conductor layer has an annular shape that surrounds the probe needle coaxially. Therefore, if the probe needle is brought into contact with a part of the inner conductor layer, it can be brought into contact with another conductor layer somewhere on the annular contact edge surrounding the probe needle. As a result, if the distance between the measurement point of the inner conductor layer and another conductor layer is within the range of the diameter of the annular contact edge, impedance measurement will be possible, and the probe will be controlled to rotate around its axis. Not only can the probe be easily positioned at the measurement point without performing, but also accurate impedance measurement can be performed on the laminated board with different dimensions between the inner conductor layer and another conductor layer. Has advantages.

The probe has a socket at the rear end to which the coaxial cable extending from the impedance measuring instrument is connected.The center conductor of the coaxial cable inserted into the socket is connected to the probe needle, and the coaxial cable connected to the outer periphery of the socket. Outer conductor is connected to the ground electrode.

When the contact edge of the ground electrode is made of conductive rubber, it can make close contact with the conductor layer with irregularities on the surface by utilizing the deformability of the conductive rubber, providing a highly reliable impedance. Measurement can be performed.

It is desirable that the probe needle be detachable from the probe body holding the ground electrode, so that the probe needle having a relatively short life can be easily replaced. Further, it is preferable that the probe needle is movable with respect to the ground electrode along the axial direction and is supported by a float, so that an impact when the probe needle is brought into contact with the inner conductor layer can be absorbed, and Damage to the needle and the inner conductor layer can be minimized.

A dielectric made of a material having a low dielectric constant and a low dielectric loss tangent is provided between the probe needle and the ground electrode to reduce loss in a high frequency region and improve the reliability of impedance measurement.

In a preferred embodiment, the probe needle is self-moving between a forward position in which the probe needle projects forward in the axial direction by the force of the spring and a retracted position in which the probe needle is pushed backward by being piled on the spring. A part of the probe needle comes into contact with the ground electrode, and the probe needle is separated from the ground electrode when in the retracted position. For this reason, only by first bringing the probe needle into contact with the inner conductor, static electricity charged on the inner conductor can be removed through the ground electrode, and subsequently, the probe needle is brought into contact with the inner electrode at a predetermined contact pressure. Pushing the probe needle away from the ground electrode Impedance measurement is effective, and static electricity removal and impedance measurement can be performed continuously. '

In this case, the ground electrode is composed of a ground electrode body and a detachable cover at the front end thereof, and it is desirable to form a contact edge of the ground electrode on the cover. This allows the probe to be maintained by replacing the cover if the contact edge is worn or damaged. The temporary electrical connection between the probe needle and the ground electrode is achieved by bringing the flange provided on the probe needle into contact with the inner surface of the cover.

In another preferred embodiment, a ground electrode is movably held along the axial direction of the probe needle on the outer periphery of a support cylinder that surrounds and supports the probe needle. Thereby, the movement of the probe for bringing the probe needle into contact with the inner conductor and the movement of the probe with the ground electrode for bringing the contact edge of the ground electrode into contact with another conductor layer can be performed separately. Accurate positioning of the probe can be performed. That is, after confirming that the probe needle has contacted the internal conductor, the ground electrode can be moved, and both can contact the corresponding conductor at the correct position.

In this connection, the ground electrode is connected to a rear member provided on the rear side of the support cylinder in the axial direction by a spring member. By the action of this spring member, the contact edge of the ground electrode is brought into contact with the conductor by a sufficient contact pressure. Layer, and a stable electrical connection can be made even if the contact surface of the conductor layer is irregular. This rear member is used to be connected to an external actuator overnight, and is moved axially forward by the actuator to bring the contact edge of the ground electrode into contact with the target conductor layer at a predetermined contact pressure. Can be.

The above-mentioned features of the present invention and other features are described below with reference to the accompanying drawings. Will be apparent from the detailed description of BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an exploded perspective view showing a laminated board with an inner circuit measured by a high-frequency circuit impedance measuring probe of the present invention.

FIG. 2 is a plan view showing an inner layer circuit formed in the laminated plate of the above.

FIGS. 3, 3B, 3C, 3D, and 3E are perspective views showing a process of forming a multilayer printed board formed from the laminated board using the same.

FIG. 4 is a cross-sectional view showing the impedance measurement probe of the present invention.

FIG. 5 is a side view showing the front end surface of the probe.

FIG. 6 is a partial cross-sectional view showing a partially modified example of the above probe.

FIG. 7 is a perspective view showing a usage form of the above probe.

FIG. 8 is a front view showing a usage form of the above probe.

FIG. 9 is a cross-sectional view showing a usage form of the above probe.

FIG. 10 is a cross-sectional view showing another usage form of the probe of the above.

FIGS. 11 and 12 are cross-sectional views showing an impedance measurement probe according to another embodiment of the present invention.

FIGS. 13 and 14 are cross-sectional views showing an impedance measuring probe according to still another embodiment of the present invention.

FIG. 15 is a perspective view showing a part of the probe of the above. BEST MODE FOR CARRYING OUT THE INVENTION

The impedance measurement probe according to the present invention is designed for measuring the impedance of a high-frequency circuit of a laminated board containing an inner circuit used for a multilayer printed board. Things. The target laminated board L with an inner layer circuit is an intermediate product that is finally finished as a multilayer printed board, and has a basic high-frequency circuit (hereinafter referred to as an inner layer circuit) 12 in the inner layer, and the outermost This is an external conductor layer to be formed later as a circuit. FIG. 1 shows the first and second insulating layers 10 and 20 as inner layers on the upper and lower surfaces of the insulating substrate 1, and the first and second insulating layers 11 and 20, respectively, outside these inner layers. An example is shown in which the third conductor layer 30 and the fourth conductor layer 40 are provided via the interface 12. In this case, the inner circuit 12 is formed on the first conductor layer 10, and the second conductor layer 20 is Although not shown, when this intermediate product is configured to have three conductor layers, an inner circuit is formed on the inner conductor layer and two outer layers are formed. A final signal circuit is formed on one of the conductor layers, and a grant circuit is formed on the other one.

As shown in FIGS. 3A-3C, the laminated board L with the inner layer circuit is formed by forming the first conductor layer 10 and the second conductor layer 20 on the entire surface of both sides of the insulating base material 1 and then forming the first conductor layer 10 An inner layer circuit 12 is formed in the second conductor layer 20, and a ground circuit of a high-frequency circuit to be completed later is formed in the second conductor layer 20. On the first conductor layer 10, a test conductor 13 for measuring circuit impedance is formed in addition to the inner layer circuit 12. After that, the third conductor layer 30 and the fourth conductor layer 40 are formed on the first conductor layer 10 and the second conductor layer 20 via the first insulation layer 11 and the second insulation layer 12, respectively, over the entire surface of the laminate. It is formed over.

Thereafter, as shown in FIGS. 3D and 3E, the laminated board is formed with predetermined high-frequency circuits 32 and 42 of the third and fourth conductor layers 30 and 40, which are the outermost layers. The connection is made by through holes 33 to obtain a final multilayer printed board.

As shown in FIG. 2, a plurality of identical inner-layer circuits 12 are formed on the first conductor layer 10, and a plurality of circuits are also formed on the other conductor layers at the same time. By cutting out into a plurality, a plurality of circuit components are formed at the same time. Shown in the figure As described above, a plurality of test conductors 13 are formed, and each test conductor 13 extends over the entire length in the longitudinal direction of the laminated plate, and the ends thereof are exposed at both end surfaces of the laminated plate L. In this connection, the edge of the second conductor layer 20 after the formation of the ground circuit is exposed on the end face of the laminate, and when measuring the circuit impedance, the reference potential for the test conductor 13, that is, the ground potential Function to give.

To measure impedance, a probe P specially designed according to the laminated board above, a measuring instrument that applies a high-frequency signal to the test conductor 13 via the probe and analyzes the reflected wave from it, a measuring instrument and a probe A coaxial cable connecting P is used. The probe P has a probe needle 111 and a ground electrode 120.As shown in FIGS. 7 and 9, the probe P contacts the one end of the test conductor 13 and the front end of the ground electrode 120. The impedance of the inner layer circuit is measured by bringing the annular contact edge 121 formed in the above into contact with the second conductor layer 20 or the third conductor layer 30. The measuring instrument has an input signal generator that generates a high-frequency signal for oscilloscope II measurement. FIG. 4 shows a probe according to an embodiment of the present invention. The probe P includes a metal main body tube 100 provided with a socket 101 into which a center pin of a coaxial cable is inserted at a rear end, and a needle unit 110 housed in the main body tube 100. The needle unit 1 10 is composed of a holder 1 1 2 that supports the probe fl 1 1 to move forward and backward along the axial direction. The spring 1 1 3 housed inside the holder 1 urges the probe needle 11 forward. Has been done. The holder 1 1 2 is electrically connected to the probe needle 1 1 1 and is electrically connected to the socket 1 01 into which the center pin of the coaxial cable is inserted. 04 and 105 are electrically isolated from the main body cylinder 100. A screw portion 102 is formed at the rear end of the main body tube 100, and a nut integrated with the outer conductor of the coaxial cable is coupled to the screw portion 102 here. In this way, a book electrically connected to the outer conductor (shield) of the coaxial cable used to connect to the measuring instrument The body cylinder 100 defines the ground electrode 120, and an annular projection is formed on the front end surface of the body cylinder 100 to define an annular contact edge 121 concentrically surrounding the probe needle 111. A mounting flange 106 is formed at the center of the main body cylinder 100 in the axial direction, and an actuator of a moving mechanism for moving the probe P is connected to the mounting flange 106.

The probe P is held by the moving mechanism so as to come close to the end face of the laminate L placed on the XY table. The laminate is moved in the horizontal direction by the XY table, and horizontal positioning is performed between the probe 13 and the conductor 13 exposed at the end face of the laminate. Thereafter, the position of the probe P is adjusted in the Z direction by another moving mechanism, and the alignment between the probe needle 11 and the test conductor 13 is completed. Then, the probe P is moved closer to the end face of the laminated plate L by the moving mechanism, and as shown in FIGS. 7, 8, and 9, the probe needle 11 comes in contact with the test conductor 13 and the ground electrode 120 The annular edge 121 contacts the edges of the second conductor 20 and the third conductor 30 which are another layer around the test conductor 1. In this state, a high-frequency signal is sent from the measuring instrument to the test conductor 13, and the high-frequency signal reflected therefrom is analyzed to measure the impedance of the test conductor 13, that is, the impedance of the inner layer circuit. The probe P is designed to have the same impedance as the coaxial cable 69 (for example, a pass characteristic of 10 GHz: Ζ-50 Ω ± 1 Ω), and is impedance-matched. Here, since the test conductor 13 is provided over the entire length of the laminate, the impedance at each point of the length of the test conductor is measured by analyzing the reflected high-frequency signal in consideration of time. Can be determined. In addition, since the test conductor is exposed on both end faces of the laminate L, impedance measurement can be performed on any end face of the laminate L.

The insulating sleeves 104 and 105 are preferably formed of a material having a low dielectric constant and a low dielectric loss tangent in order to improve the characteristics at high frequencies. For example, PTFE (polytetrafluoride) The ability to use fluororesins such as ethylene) and resins such as PPO (polyphenylene oxide) and PPE (polyphenylene ether). It has the same low dielectric constant and low dielectric loss tangent as fluororesins, and Any material having the same shape stability as fluororesin can be used.

Since the probe needle 1 1 1 is formed so that it can be inserted and removed from the holder 1 1 2, it can be replaced when the probe needle is worn. For example, when the thickness of the test conductor 13 is 18 im, a probe needle having a diameter of 100 jUm and a diameter other than the tip of 300 jUm can be used as the probe needle 111. Since the probe needle 1 1 1 is slidable forward and backward with respect to the holder 1 1 1 2 and is urged forward by the spring 1 1 3, the probe needle 1 1 1 is pressed with an appropriate contact pressure. A reliable electrical connection is made by contacting the test conductor 13. At the same time, the action of the spring prevents an excessive impact on the laminated plate L and the tip of the probe needle 111 during impedance measurement.

As shown in FIG. 6, an annular contact edge 121 made of conductive rubber may be fitted into the ground electrode 120. An appropriate contact pressure can be obtained by the elastic deformability of the rubber, and the contact edge 121 and the corresponding conductor layer can be prevented from being damaged. Conductive rubber has a lower resistance value than normal rubber and has the same conductivity as conductive metal even when there is no distortion due to pressure, etc., and the change in resistance value due to compression is small Things. For example, “EC-A” manufactured by Shin-Etsu Chemical Co., Ltd. can be used. Further, the contact edge 121 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. For example, rpCRJ manufactured by Nippon Synthetic Rubber Co., Ltd. can be used.

In FIG. 9, the probe P is brought into contact with the end face of Although an example in which impedance measurement is performed by destructive inspection has been described, the probe P of the present invention also has the third conductor 30 and a part of the first insulating layer 11 cut away as shown in FIG. It is also possible to make impedance measurement by bringing the probe needle 1 1 1 directly into contact with the test conductor 13 and the internal circuit, and by bringing the ground electrode 1 20 into contact with the external conductor layer 30 exposed on the top surface of the laminate L. It is.

11 and 12 show a probe according to another embodiment of the present invention. This probe P has basically the same structure as the above embodiment, except that a detachable force par is provided at the front end of the main body cylinder 100A and this is used as a ground electrode 120A. Identical parts are indicated by the same reference numerals with the reference symbol ΓΑ ”added. An annular contact edge 121 この is formed on the front end face of the cover 120Α, and a rear end thereof is coupled to the main body cylinder 100A with a screw to form a space 124 between itself and the main body cylinder. ing. A flange 1 14 located in this space 1 24 is integrally formed with the probe 1 11 A, and as shown in Fig. 11, the probe 1 "ΠA is urged forward by a spring 1 13A. In this position, the flange 114 contacts the inner surface of the cover 120A, and as shown in Fig. 12, when the probe needle 111A is pushed in, the flange 114 moves away from the cover 120A. The insulation sleeve 104A comes into contact with the end face of the insulation sleeve 104A.An insulation ring 108 is provided at the center of the cover 120A to provide insulation from the probe needle 111A. Therefore, if the test conductor 13 is charged with static electricity, the static electricity can be released from the flange 114 to the ground electrode 120A when the probe needle 11A comes into contact with the test conductor 13 and then the ground electrode 1 As the contact edge of 20A 1 21A is pressed against the end face of the laminate L, By lobe needle 1 1 1 A is pressed, the flange 1 1 4 away from the ground electrode 1 20A, Ru immediately impedance measurement is performed.

FIGS. 13, 14, and 15 show a probe according to still another embodiment of the present invention. This probe P has basically the same structure as the above embodiment, except that a ground electrode 120B is supported on the main body cylinder 100B so as to be slidable along the axial direction of the main body cylinder. The same members are denoted by the same reference numerals with the reference symbol "BJ" attached. The ground electrode 120B holds the annular contact edge 121B made of conductive rubber, and the rear end in the axial direction of the main body cylinder 100B. Attached to the mounting flange 106B, which is also slidably supported by the coil, is a coil panel 126. In this embodiment, the threaded portion 102B at the rear end of the main body tube 10OB is coupled to the outer conductor of the coaxial cable with a nut. In addition, it is used to be fixed to a moving mechanism for controlling the position of the probe P. In this case, the mounting flange 106B is connected to an actuator provided in the moving mechanism, and the moving mechanism is used for the drawing. As shown in 13, after the probe needle 1 1 1B is brought into contact with the test conductor 13 on the end face of the laminated plate L, the mounting flange 106B is pushed forward by an actuator, thereby causing the coil spring 1 Joined at 26 The land electrode 120B is moved forward, and as shown in Fig. 14, the annular contact edge 121B is laminated and brought into contact with the conductor layers 20, 40 on the end faces, whereby impedance measurement is performed. In this case, an appropriate contact pressure is applied by the coil panel 126, and an excessive impact on the contact edge 121 against the laminated plate is also prevented.

Claims

The scope of the claims

1. A high frequency circuit impedance measurement probe for a laminated board with an inner layer circuit used for a multilayer printed board,

The probe includes a probe needle for contacting an internal conductor layer forming a high-frequency circuit in the laminate, and a ground electrode for contacting the internal conductor layer and another conductor layer.

The probe needle is connected to an external impedance measuring instrument and is used to send the high-frequency signal from this to the inner conductor and transmit the high-frequency signal reflected from it to the measuring instrument,

The contact edge force of the ground electrode that comes into contact with another conductor layer << the coaxial shape surrounding the probe needle.

2. In the probe according to claim 1,

The probe has a socket at the rear end to which a coaxial cable extending from the impedance measuring instrument is connected, and the center conductor of the coaxial cable inserted into the socket is connected to the probe needle and connected to the outer periphery of the socket. The outer conductor of the coaxial cable is connected to the ground electrode.

3. In the probe according to claim 1,

The contact edge of the ground electrode is made of conductive rubber _c

4. In the probe according to claim 1,

The probe needle is now detachable from the probe body that supports the ground electrode.

5. The probe according to claim 1, wherein

The probe needle was movable with respect to the ground electrode along the axial direction, and was float supported.

6. In the probe according to claim 5,

Probe needle float supported by spring against ground electrode _c

7. In the probe according to claim 1,

The dielectric interposed between the probe needle and the ground electrode was formed of a material with a low dielectric constant and a low dielectric loss tangent.

8. In the probe according to claim 5,

The probe needle can move freely between the forward position where it protrudes forward in the axial direction by the force of the spring, and the retracted position where it is piled on the spring and pushed backward. The probe needle touches the electrode, and the probe needle _C came away from the electrode

9. In the probe according to claim 8,

The ground electrode was composed of a ground electrode body and a detachable cover at the front end thereof, and a contact edge of the ground electrode was formed on the cover.

10.In the probe according to claim 9,

When the probe needle is in the forward position, the flange provided on the probe needle contacts the inner surface of the cover, and the flange comes off the cover when it moves to the retracted position.

11.The probe according to claim 1,

A ground electrode was movably held along the axial direction of the probe needle on the outer periphery of a support cylinder surrounding and supporting the probe needle.

1 2. In the probe according to claim 11,

The ground electrode was connected to a rear member provided at the rear of the support cylinder in the axial direction by a spring member.

1 3.Claim 1 2 (In the probe of this description, The above spring member is a coil panel c

1 4. The probe according to claim "12,

The above-mentioned rear member is movable along the axial direction of the support cylinder, and is used to be connected to an external actuator. The rear member is moved forward in the axial direction by an actuator, thereby forming the contact edge of the ground electrode. The target conductor layer is brought into contact with a predetermined contact pressure.