JP3439457B2 - Coaxial cable for board connection - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial cable for connecting to a board, and more particularly to suppressing the fluctuation of the characteristic impedance at the connection terminal to achieve matching of the characteristic impedance with the wiring board, and further, it is small and excellent. The present invention relates to a coaxial cable for connecting a substrate, which has strength.

[0002]

2. Description of the Related Art In a semiconductor test apparatus, as a mode of transmitting a signal to a wiring board serving as an interface with a device under test, a coaxial cable is connected to a through hole of the wiring board and a signal is transmitted from the cable. Is adopted. In the wiring board, a through hole for a signal and a through hole for a ground are usually formed at intervals of 2.54 mm, and a plurality of channels, each pair of which is one channel, are formed. A coaxial cable for substrate connection having a pair of pin terminals at its tip is connected to each channel, and a predetermined test is performed based on this configuration.

FIG. 2 shows the structure of a coaxial cable for connecting a board, which has been widely used in the past, and the relationship between the cable and the wiring board. In the figure, reference numeral 1 denotes a coaxial cable in which an inner conductor 2, an insulator 3 and an outer conductor 4 are exposed by a predetermined length. A signal terminal 5 and a ground terminal 6 are attached to the exposed inner conductor 2 and outer conductor 4, respectively, and the periphery thereof is covered with a resin-molded cover member 7. Reference numeral 8 denotes a cable jacket.

Reference numeral 9 is a wiring board, 10 is a through hole as a signal electrode formed through the board 9, and 11 is a similarly formed through hole as a ground electrode. The through holes 10 and 11 have a mutual spacing of 2.54 mm, and although not shown in the drawing, the wiring board 9 is formed with a large number of channels as a set thereof, and the coaxial cable for board connection is formed. C is the terminal 5 at the tip
And 6 are inserted into through holes 10 and 11 to connect to each channel.

By the way, the characteristic impedances of the coaxial cable 1 and the wiring board 9 used in the above-described connection configuration are usually designed to be at the same level. However, according to the board connecting coaxial cable C having the configuration shown in the figure, the arrangement of the inner conductor 2 and the outer conductor 4 is changed from the coaxial cable 1 portion to the two-wire parallel portion including the terminals 5 and 6. Further, since the material and shape are also changed in this process, the characteristic impedance often increases due to these unstable factors, and as a result, the characteristic impedance does not match the wiring board. . The mismatch of the characteristic impedance causes a reflection phenomenon in the mismatched portion, and thus acts to reduce the transmission fidelity due to the adverse effect of the reflection on the transmission signal.

[0006] Japanese Patent Application No. 2000-108 discloses a coaxial cable for connecting a substrate, which eliminates the above-mentioned instability factors of the internal structure.
No. 109 has been proposed. FIG. 3 shows the configuration.
The features of this coaxial cable for board connection are that the insulator 3 is projected to the position of the tip surface 13 of the cover member 7 including the insulating base material 12 formed by resin molding, and the internal conductor 2 is projected from the tip of the insulator 3. Signal terminal 5
And the structure in which the grounding terminal 6 is attached to the outer conductor 4 which is converged and bent at a right angle to the side. The insulating base material 12 constitutes the front end surface 13 of the cover member 7 and its vicinity, and the internal conductor 2 (signal terminal 5) and the ground terminal 6 are inserted through the insulating base material 12. It projects through the holes 14 and 15.

According to the board connecting coaxial cable C of this structure, since the insulator 3 is projected to the position of the tip surface 13 of the cover member 7, the characteristic impedance variation at the connection terminal with the wiring board 9 is prevented. Can be suppressed and thus
As a result, impedance matching with the wiring board 9 can be achieved.

However, although it is the coaxial cable for board connection of FIG. 3 having improved performance as described above, strictly speaking, it still has the following problems. (1) When the signal terminal 5 and the ground terminal 6 are connected to the signal through hole 10 and the ground through hole 11 of the wiring board 9, the through holes 10 and 11 are formed.
The characteristic impedance changes due to the addition of the capacitance between them, which causes a mismatch of the characteristic impedance with the wiring board 9.

(2) Since the exposed insulator 3 is covered by the cover member 7 including the insulating base material 12, the capacitance of these components acts on the insulator 3.
Therefore, the characteristic impedance on the side of the coaxial cable C changes, causing a mismatch of the characteristic impedance with the wiring board 9.

(3) Since the cover member 7 is provided on top of both the signal terminal 5 and the ground terminal 6, the connection space to the wiring board 9 becomes large, which hinders high-density mounting.

FIG. 4 shows a structure of a coaxial cable for connecting a substrate, which can solve the problems (1) to (3) described above. It is disclosed in Japanese Patent Application Laid-Open No. 2000-134783, and is characterized in that the drain wire is used as a ground terminal. FIG. 4A shows the structure of the coaxial cable 1 used, in which the drain wire 16 is vertically arranged between the insulator 3 and the outer conductor 4.

As shown in FIG. 4B, the structure of the board connecting coaxial cable C is such that the inner conductor 2, the insulator 3, the outer conductor 4 and the jacket 8 are stripped by a predetermined length. While the inner conductor 2 is used as the signal terminal 5, the outer conductor 4 formed by tape-shaped winding is fixed onto the insulator 3 by soldering 17 at its end to fix the insulator 3 and the outer conductor 4. Drain wire 16 pulled out from between
Is used as the ground terminal 6. Reference numeral 18 denotes a heat-shrinkable tube fitted to the end of the cable.

According to the substrate connecting coaxial cable having the above structure, since the drain wire 16 is used as the ground terminal 6 , the terminal structure is simple and small, and the cover member as shown in FIGS. 2 and 3 is used. There is no influence of the electrostatic capacitance due to 7. Therefore, this cable can solve the problems (2) and (3) described above, and is evaluated as a useful coaxial cable for connecting a substrate.

[0014]

However, according to the conventional coaxial cable for connecting a substrate of this type, the above-mentioned (1) is used.
The problem of (1) is still unsolved, and the structure is insufficient in strength, so that the structure may be destroyed during the connection to the wiring board by the action of external force such as catching. The latter problem may occur frequently when mounting on a wiring board becomes highly dense, and it is necessary to focus on it.

Therefore, an object of the present invention is to achieve the matching of the characteristic impedance with the wiring board by suppressing the variation of the characteristic impedance including the above-mentioned (1), and also to connect the board with the small size and the excellent strength. To provide a coaxial cable for use.

[0016]

In order to achieve the above object, the present invention comprises an inner conductor, an insulator, an outer conductor, and an outer cover, which are formed in this order. The inner conductor and the outer conductor are arranged in this order. In a board connecting coaxial cable to be connected to a wire board, a signal which is composed of the inner conductor coaxially protruding from the tip of the insulator, is inserted into a through hole of the wiring board, and is directly connected to the through hole. Terminal, a ground terminal electrically connected to the outer conductor, and directly connected to a ground circuit of the wiring board, and the outer cover .
From the insulator to the tip of the insulator,
It was exposed out of the signal terminals at the distal end surface and the same surface, and provide a coaxial cable for board connection, characterized in that it comprises a cover member formed with void portion to the periphery of the distal end portion of the insulator from the front end surface To do.

Although the entire cover member may be formed of one resin mold body, it is also effective to form the tip surface contacting the wiring board and its vicinity with another insulating base material. In that case, the insulating base material is usually constructed so as to be integrated with the ground terminal and exposed from the tip end surface, and is also provided with a through hole for inserting the insulator of the coaxial cable. Then, the through hole is provided with an internal dimension necessary for forming the above-mentioned void portion with the inserted insulator.

The above construction incorporating the insulating base material is
This prevents the occurrence of inconveniences such as displacement of the ground terminal due to resin flow when forming the cover member or inflow of the resin film onto the ground terminal, thereby exposing the ground terminal from the tip surface of the cover member. It produces the effect of stabilizing the state. As a constituent material of the insulating base material, in order to ensure further stabilization of the characteristic impedance, it is preferable that the constituent material is a porous resin molded body having a small relative dielectric constant. Then, a foamed body of fluororesin or PBT (polybutylene terephthalate) resin is applied.

The form of conduction between the outer conductor and the ground terminal in the present invention is, for example, a coaxial cable.
When provided with the rain wires, connect the drain wire to the ground terminal, thereby forming grains through electrically between the external conductor and the ground terminal is employed. In such a case, the internal structure of the cable terminal portion is stabilized, so that it is possible to provide a highly useful coaxial cable for connecting a substrate in which variation in characteristic impedance is further suppressed.

In the coaxial cable used in the present invention, the internal conductor forming the signal terminal may be in the form of a single wire or a stranded wire. In the case of a stranded wire, this is formed into a single wire by soldering or the like. It is possible to solidify and use it as a signal terminal. The insulator is made of a resin having a low dielectric constant such as polyethylene or a fluororesin, or a porous body obtained by foaming these, and is formed by extrusion or tape winding. The outer conductor is formed by winding a plurality of fine wires, braiding the same, or winding a metal tape or a resin tape having a metal layer formed on one surface thereof, and the outer cover is made of polyethylene, fluororesin or the like. .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a coaxial cable for connecting a substrate according to the present invention will be described. In FIG. 1A, reference numeral 21 denotes a coaxial cable, which is configured by sequentially providing an insulator 23, a drain wire 24, an outer conductor 25, and an outer jacket 26 on an inner conductor 22. Here, the main specifications of the coaxial cable 21 are as follows. -Inner conductor 22: stranded wire of AWG24 to 32 plated with silver. -Insulator 23: Extruded coating of porous fluororesin. Outer diameter 0.
8 mm-External conductor 25: A wound body having a metal layer on the inside with a resin tape having a metal layer on one side. -Envelope 26: extrusion coating of fluororesin. Outer diameter 1.4 mm. Characteristic impedance between the inner conductor 22 and the outer conductor 25: 50 ± 2Ω.

Reference numeral 27 denotes a cover member formed by molding of PBT resin or the like, 28 denotes an insulating base material provided at the tip of the cover member 27, and the first hole 29 and the second hole 3 are provided.
It has a through hole 31 for inserting the insulator 23 in a combination of 0s. The cover member 27 is formed from the jacket 26 to the periphery of the tip end portion of the insulator 23 by including the insulating base material 28 as a constituent member thereof, and further includes a tip end surface 32 formed of the insulating base material 28. ing.

Reference numeral 33 denotes a ground terminal which is formed so as to straddle both surfaces of the insulating base material 28 and whose terminal surface 34 is exposed from the front end surface 32 of the cover member 27. This ground terminal 33, which is made of solder-plated phosphor bronze having a thickness of 0.4 mm and a width of 2.4 mm, is integrated with the insulating base material 28 so that the effective length L of the terminal surface 34 is 4 mm. Further, the drain wire 24 bent in the direction orthogonal to the insulator 23 is connected by soldering.

Therefore, the outer conductor 25 in this example is
It is electrically connected to the ground terminal 33 through the drain wire 24. Reference numeral 35 denotes a void portion formed around the insulator 23 having an outer diameter of 0.8 mm by giving inner diameters of 1.2 mm and 1.4 mm to the first hole 29 and the second hole 30, respectively. It is formed from the tip surface 32 of 27 to the tip of the insulator 23.

FIG. 1B shows a structure in which the substrate connecting coaxial cable C having the above configuration is connected to a wiring substrate. In the figure, 36 is a wiring board, and 37 is a wiring board 36.
Shows a through hole as a signal electrode, which has the internal conductor 22 of the coaxial cable C for substrate connection, that is, a signal terminal 38 inserted therein and connected thereto. On the other hand, the wiring board 3
The grounding electrode 6 is composed of a grounding circuit on the surface of the substrate 36 (not shown), and the terminal surface 34 of the grounding terminal 33 of the substrate connecting coaxial cable C is brought into contact with the terminal 33. A predetermined connecting portion is formed between the two.

The through hole 37 and the ground electrode constitute one channel by forming a pair with each other, and the wiring board 36 is formed with a large number of channels by these groups, and the coaxial cable C for connecting the board is formed in each of them. Will be connected. In the figure, 39 and 4
Reference numeral 0 indicates solder which is supplied and fixed to fix the connection between the signal terminal 38 and the ground terminal 33.

According to the coaxial cable for board connection according to the present embodiment configured as described above, the following effects can be obtained, and the problems in FIGS. 2 to 4 described above can be effectively solved. You can (1) Since the signal terminal 38 is configured by the internal conductor 22 protruding from the tip of the insulator 23 and the ground terminal 33 is of a contact type, the configuration can be downsized and the configuration inside the cover member 27. Does not become unstable as in the conventional two-wire parallel configuration, and therefore, the connection space to the wiring board can be reduced and the impedance matching with the wiring board 36 can be achieved by suppressing the variation of the characteristic impedance. be able to.

(2) Since the gap 35 is formed from the front end surface 32 of the cover member 27 to the periphery of the front end of the insulator 23, the insulator 23 causes the electrostatic charge of the cover member 27 (insulating base material 28). Since there is no influence of the capacitance, it is possible to prevent the impedance mismatch with the wiring board 36 due to the change of the characteristic impedance due to this influence.

(3) Since the whole is covered with the cover member 27 including the insulating base material 28, it has sufficient strength, and therefore, it is structured by the action of external force when connecting to the wiring board. There is no fear of destroying the result.

(4) The ground terminal 33 is connected to the wiring board 36.
Since the connecting portion is formed by contacting the circuit for grounding, it is not necessary to form the through hole as the electrode for grounding in the wiring board 36. Therefore, the through holes for signals and the grounding formed on the wiring board are not necessary. It is possible to prevent the variation of the characteristic impedance due to the addition of the electrostatic capacitance between the holes and the mismatch of the characteristic impedance with the wiring board due to the variation.

[0031]

As described above, according to the substrate connecting coaxial cable of the present invention, the signal terminal is formed by the inner conductor protruding from the tip of the insulator.
Since the ground terminal for contacting with the ground circuit of the wiring board to make a predetermined connection is provided, it is possible to eliminate the instability factor of the internal structure as in the conventional two-wire parallel structure, and to use the ground terminal of the wiring board. Through holes can be eliminated, and therefore fluctuations in characteristic impedance due to unstable internal structure and addition of capacitance between through holes of the wiring board can be effectively suppressed. The space can be reduced when connecting to a substrate.

Further, since the cover member is formed from the jacket of the coaxial cable to the tip of the insulator, sufficient mechanical strength can be ensured, and further, the tip of the insulator can be provided from the tip surface of the cover member. Since a void is formed around the periphery of the part, it is possible to prevent the influence of the electrostatic capacity of the cover member on the insulator, and as a whole, there is no risk of the structure being destroyed by the action of external force, and more stable. It is possible to provide a substrate-connecting coaxial cable having an improved characteristic impedance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a substrate connecting coaxial cable according to the present invention, in which FIG.
Shows a connection structure to the wiring board.

FIG. 2 is an explanatory view showing a conventional board connecting coaxial cable.

FIG. 3 is an explanatory view showing another conventional coaxial cable for substrate connection.

4A and 4B are explanatory views showing still another conventional coaxial cable for connecting a substrate, wherein FIG. 4A is a sectional view of the coaxial cable used, and FIG.

[Explanation of symbols]

21 coaxial cable 22 Inner conductor 23 Insulator 24 drain wire 25 outer conductor 26 Jacket 27 Cover member 28 Insulation base material 29 First hole 30 second hole 31 through hole 32 Tip surface 33 Ground terminal 34 Terminal surface 35 void 36 wiring board 37 Through hole 38 Signal terminal 39, 40 solder

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01R 9/09 H01R 17/04

Claims (4)

(57) [Claims] 1. An inner conductor and an outer conductor are formed in this order on an inner conductor, and the inner conductor and the outer conductor are formed.
A coaxial cable for board connection which connects to the wiring substrate, the insulator tip is constructed from the inner conductor is projected coaxially from, is directly connected to the through hole is inserted into the through holes of the wiring board that a signal terminal, wherein the conduction with the outer conductor, and the ground terminal directly connected to the grounding circuit of the circuit board, are formed to the tip portion of the casing collar the insulator, before
A cover member that exposes the signal terminal on the same surface as the tip surface of the insulator and forms a void portion from the tip surface to the periphery of the tip portion of the insulator. A coaxial cable for board connection. 2. The cover member has an end surface and its vicinity made of an insulating base material, and the insulating base material has a through hole in which the leading end portion of the insulator is inserted to form the void portion. The coaxial cable for board connection according to claim 1, wherein the coaxial cable is integrated with the terminal for ground and exposes the terminal for ground from a position of the tip surface. 3. The coaxial cable for connecting a substrate according to claim 2, wherein the insulating base material is made of a porous resin molded body. 4. The outer conductor has a drain wire between the outer conductor and the insulator, and the drain wire is connected to the ground terminal to be electrically connected to the ground terminal via the drain wire. The coaxial cable for connecting to a substrate according to claim 1, wherein