WO2015000749A1

WO2015000749A1 - Connector for high frequency coaxial cable

Info

Publication number: WO2015000749A1
Application number: PCT/EP2014/063295
Authority: WO
Inventors: Franz Manser; Josef Fuchs
Original assignee: Huber and Suhner AG
Current assignee: Huber and Suhner AG
Priority date: 2013-07-04
Filing date: 2014-06-24
Publication date: 2015-01-08
Anticipated expiration: 2016-01-04

Abstract

The invention is directed to a coaxial connector (1) comprising an outer conductor (3) and an inner conductor (2) positioned with respect to the outer conductor (3) by an insulator (4). The coaxial connector (1) comprises a first soldering depot (12), which is arranged behind a first opening (7) of a rear section (6) of the inner conductor (2). During soldering, the first opening (7) is foreseen to receive soldering material of the first soldering depot (12).

Description

CONNECTOR FOR HIGH FREQUENCY COAXIAL CABLE

FIELD OF THE INVENTION

The present invention relates to a connector for coaxial cables as they are used for the transmission of high frequency signals. The connector has a deposit of cold solder metal to join the connector to a coaxial cable.

BACKGROUND OF THE INVENTION

From the prior art several high frequency connectors are known, which comprise a deposit of cold solder metal by which a coaxial cable can be interconnected to the connector by soldering.

DE1 0355779B3 was published in June 2005 in the name of I MS Connector Systems GmbH . It describes a two-part connector which links two lengths of high-frequency coaxial cable. The connector consists of an inner bush and a push- fit outer sleeve. The inner bush has an aperture to the core interface through which solder metal is surrendered . The aperture holds a solder metal holding zone that surrenders the metal on heating to the interface between the wire core and the surrounding contact surface.

WO03061075A1 was published in J uly 2003 in the name of Rosenberger Hochfrequenztechnik GmbH & Co. It relates to a coaxial connector with an inner and an outer conductor piece which each comprises a cable inlet for connecting the coaxial connector to a coaxial cable. A moulded solder piece made from a soldering agent is arranged in the cable inlet of the inner conductor piece. The inner conductor piece is pre-assembled on the coaxial connector before the coaxial connector is attached to the coaxial cable.

EP1 31 31 70A1 (DE10251 905A1 ) was published in May 2003 in the name of Spinner GmbH Elektrotechnische Fabrik. It describes a coaxial solder connector, which has a plug head with a cable-side opening . A solder deposit is arranged in an axial bore of the plug connector's inner conductor. The solder deposit may be heated by means of an induction loop to produce a solder connection.

EP1 562266A1 was first published in August 2005 in the name of Tyco Electronics U K Ltd. It describes a connector for terminating a coaxial cable. The connector comprises a centre contact having a soldering end for soldering to an exposed end portion of a centre conductor of the coaxial cable. The soldering end of the centre contact has a contact surface with an opening formed therein for receiving and soldering to the exposed end portion of the centre conductor. At least one notch is formed in the contact surface to provide a passage through which trapped air may escape so that the flow of the solder is not impeded .

EP0838880A2 was first published in April 1 998 in the name of Andrew AG . It describes a method of attaching a connector to a coaxial cable. An insulative disc of the connector is installed onto an exposed portion of the inner conductor. An inner contact of the connector is installed onto the exposed portion of the inner conductor. A solder preform is installed onto the exposed portion of the outer conductor. A body member of the connector is installed over the solder preform onto the exposed portion of the outer conductor. To complete the cable assembly, the solder preform is melted to firmly attach the body member of the connector to the exposed portion of the outer conductor of the cable.

The connectors known from the prior art bear the disadvantage that they are relatively complicate to assemble. Furthermore, difficulties occur when the connectors shall be mounted fully automatically. Furthermore, the known designs result in relatively expensive connectors.

SUMMARY OF THE INVENTION

One aim of the invention is to provide an improved coaxial connector, which offers the possibility to be assembled fully automatically in a reliable manner. Furthermore, it is an aim to provide a coaxial connector with high performance regarding return loss, passive intermodulation stability and dielectric strength. In addition it is an aim to provide a coaxial connector which can be produced in a cost efficient manner.

The usability of the connectors known from the prior art is often limited due to several aspects. One aspect is the design related variation in the soldering process especially between an inner conductor of the connector and a core of a coaxial cable. The connectors known from the prior art in principle suffer from the following disadvantages.

In the connectors known from the prior art, the shield (outer conductor of coaxial cable) is contacted in a radial and in a frontal manner. Furthermore, the soldering 5 depot is arranged such that due to capillary action the soldering material tends to flow along the front of the cable in the direction of the core of the cable. As a result thereof, the dielectric strength is reduced and in worst case a short-circuit may occur which renders the connector useless.

Connectors known from the prior art comprise an insulator which may expand in i o axial direction during the soldering process due to thermal expansion . This often results in a negative change of relevant dimensions of the connector. This thermal sensitivity should be avoided . Furthermore, existing connectors suffer from impedance mismatch between the inner conductor of the connector and the core of the coaxial cable. This impedance mismatch should be avoided. A further 1 5 disadvantage of the connectors known from the prior art results from the fact that for each dimension of connector a separate insulator part is needed which for best results must be adopted to the high-frequency performance. This fact has a negative impact on the price of the product.

A connector according to the present invention is suitable to overcome the above- 20 mentioned disadvantages known from the prior art. An embodiment of a coaxial connector according to the invention comprises an outer conductor and an inner conductor positioned with respect to the outer conductor by an insulator. The inner conductor comprises a front section suitable to be interconnected to an opposite connector and a rear section suitable to be 5 interconnected to a core of a coaxial cable by soldering . A first soldering depot is arranged behind a first opening of the rear section of the inner conductor. The first opening is shaped such that during soldering the soldering material of the first soldering depot enters in the first opening . In an embodiment, the soldering depot is arranged inside a passage of the insulator. Good results are achieved if i o the soldering depot is in thermal contact with the inner conductor. The soldering depot may be clamped between the rear section and the insulator to improve thermal contact. Alternatively or in addition, the soldering depot may be interconnected to the rear section by a sleeve that is e.g. attached to the rear section and that at least partially may encompass the rear section of the inner

1 5 conductor. Alternative methods to interconnect are possible. Such an additional sleeve-like element may be advantageous in order to ensure a pre-defined contact between the first soldering depot and the rear section of the inner conductor and improve heat transfer. Thereby a more accurate and reproducible soldering process can be achieved . The interconnection between the sleeve and the

20 soldering depot may comprise a clamping of the soldering depot to the rear section of the inner conductor. In one embodiment, the soldering depot has an annular shape. Depending on the field of application, other designs are possible. If appropriate, the soldering depot may comprise several parts arranged lateral and/or adjacent to each other. The inner conductor may be clamped in the insulator. In a preferred embodiment having good performance with respect to return loss an outer diameter of the rear section of the inner conductor is about 0.5 mm to 2.5 mm larger then the diameter of the core of the coaxial cable.

Depending on the interface to be connected, the inner conductor may comprise a front section having a female or a male plug . With respect to return loss, good results may be achieved when the diameter of the rear section in general is smaller then the diameter of the front section. In one embodiment, the insulator is inserted from a cable side into a bore of the outer conductor and the inner conductor is inserted from the opposite side.

The connector normally has a bore having a section suitable to receive a coaxial cable. The diameter of the section suitable to receive the coaxial cable is adopted to an (inner) diameter of a shield of the coaxial cable. In the bore a stop, e.g . in the form of rear surface of wall may foreseen, which defines the inner position of the coaxial cable inserted into the bore. At least one second depot of soldering material may be present foreseen to interconnect the shield of the cable to the outer conductor of the coaxial connector. Good results may be achieved when the second soldering depot is arranged in axial direction at a certain distance from the stop. E.g . the second soldering depot is arranged at a distance, which is in the range of 50-200% of the diameter of the bore. If required the inner conductor and/or the insulator may comprise a venting opening to allow to discharge air trapped in the first opening . Furthermore vacuum may be applied to support flow of the soldering material. To attach a connector according to the invention to a coaxial cable in general the following method steps are executed . First the outer shield and the dielectric isolator are removed from the coaxial cable such that the core stands free over a defined length which depends on the design of the connector. The coaxial cable is then inserted into the bore of the outer conductor until the front end of the shield and/or the dielectric insulator get in contact with the stop e.g . formed by a rear wall of the insulator arranged between the inner and the outer conductor. At the same time the core of the coaxial cable reaches its position in the first opening of the inner conductor. Then at least the first soldering depot is heated until the soldering material is melted and flows inside the space between the core and the inner wall of the first opening supported by capillary effect. Heating preferably takes place by an inductive coil which is placed around or adjacent to the inner conductor and after activation thereby provides quick inductive heating of the relevant parts. Simultaneously or at a different time the second soldering depot is heated . Also this heating preferably takes place by an inductive coil placed around or adjacent to the second soldering depot. If appropriate a vacuum is applied to support entering of soldering material into the space between the core and the inner wall of the first opening .

BRIEF DESCRIPTION OF THE DRAWINGS

The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be considered limiting to the invention described in the appended claims. The drawings are showing :

Fig. 1 a connector in a front view;

Fig. 2 the connector according to Figure 1 in a side view; Fig. 3 a section view of the connector along section line AA of Figure 2;

Fig. 4 a perspective view of a further embodiment of a connector;

Fig. 5 Detail E of Figure 3;

Fig. 6 an embodiment of a connector in a side view;

Fig. 7 a section view of the connector according to Figure 6 along section line

DD;

Fig. 8 Detail F of Figure 7;

Fig. 9 Detail H of Figure 8;

Fig. 1 0 a perspective view of an embodiment of a connector. DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a connector 1 according to the present invention in a front view. Figure 2 shows the connector 1 in a side view and Figure 3 shows a section view of the connector along section line AA according to Figure 2. Figure 4 shows a connector 1 according to the present invention in a perspective view and in an exploded manner. In addition, the parts of the connector 1 are partially cut such that the inside of the connector becomes visible. Figure 5 shows in a magnified manner detail E of Figure 3.

Figure 6 shows a connector 1 according to the present invention in a side view and Figure 7 shows a section view of the connector of Figure 6 along section line DD. Figure 8 shows Detail F of Figure 7 and Figure 9 shows Detail H of Figure 8, whereas Figure 10 shows an embodiment of a connector 1 in an exploded manner, parts of the connector 1 being partially cut such that the inside of the connector becomes visible. The displayed connector 1 is a 7/ 1 6-interface. Other designs and dimensions are possible without leaving the scope of the invention. The connector 1 comprises an inner conductor 2 and an outer conductor 3, which are arranged coaxially with respect to each other. The inner and the outer conductor 2, 3 are spaced apart by an insulator 4.

The inner conductor 2 comprises a front section 5, which is suitable to interconnect to a counter part. In the shown embodiment, the front section 5 is of a female connector type, suitable to receive a male pin from a second connector (not shown in detail) . If required, the front section 5 may be of a male type (not shown in detail) . The front section 5 has a diameter D 1 (outer diameter) .

The inner conductor 2 further comprises a rear section 6 with a first opening 7 suitable to receive a core (inner conductor) 9 of a coaxial cable 8. The coaxial cable 9 in general further comprises an outer shield 1 0 and a dielectric insulator 1 1 , which is arranged between the core 9 and the outer shield 1 0. The outer shield 1 0 may normally consist out of a shield woven from wires and/or a foil and/or a corrugated sheath and/or a tube and/or a tube (not shown in detail) .

The rear section 6 has a diameter D2 (outer diameter) . The core 9 of the coaxial cable 8 has a diameter D3 (outer diameter) .

In difference to the prior art and as it can be best seen in Figure 3, the outer diameter D 1 of the female front section 5 is larger then the outer diameter D2 of the rear section 6. In that the outer diameter D2 of the rear section 6 is only about 0.5 mm to 2.5 mm larger compared to the diameter D 1 of the core 9 of the coaxial cable 8, the impedance mismatch can be reduced to an acceptable level.

A first soldering depot 1 2, here in the form of a ring shaped preform, is arranged in a passage 1 3 of the insulator 4 in front of the first opening 7 of the rear section 6. If required, the soldering depot 1 2 may partially reach into the first opening 7. In the shown embodiment, the rear section 6 of the inner conductor 2 is pressed into the passage 1 3 , where it is fixed with respect to the insulator 4 by a first barb 1 4 arranged at the outer surface of the rear section 6. Thereby, unwanted displacement is avoided . Alternatively or in addition, other fixing means (e.g . thread or snap connections) may be foreseen .

The first soldering depot 1 2 is arranged between the rear section 6 and an inwardly projecting first shoulder 1 5. If appropriate, the first soldering depot 1 2 is clamped between the rear section 6 and the first shoulder 1 3 to improve thermal contact between the rear section 6 and the first soldering depot 1 2 during soldering. Alternatively or in addition, further means may be foreseen to improve thermal contact such that the soldering material of the first soldering depot 1 0 is efficiently heated during the soldering process. Alternatively or in addition, the rear section 6 may comprise means which increase capillary effects during soldering such that the soldering material efficiently fills the room between the core 9 and an inner wall 1 9 of the first opening 7. As it can be best seen in Figure 5 the inner wall 1 9 of the first opening 7 may have a variable diameter. In the shown embodiment the inner wall 1 9 has a cylindrical shape with two sections having different diameters. A distal section 23 closer to the open (distal) end has a larger diameter and a dorsal section 24 closer to the closed (dorsal) end has a smaller diameter. A step 25 is arranged between the distal and the dorsal section 23 , 24. The shown arrangement supports capillary effects. As shown in the embodiment according to Figure 4 alternatively or in addition a venting opening 26 may be foreseen to improve capillary effects and to allow to discharge air trapped in the first opening 7. Furthermore, the opening 26 may allow to control the quality of the result of the soldering process. Depending on the design of the connector other arrangements may be appropriate.

In the shown embodiment, the insulator 4 is pressed into a bore 1 6 of the outer conductor 3 from the cable sided rear end up to a second shoulder 1 7 , which acts as a stop element to prevent unwanted displacement of the insulator 4 with respect to the outer connector 3. In the shown embodiment, the insulator 4 is further secured by a second barb 1 8 arranged at the inside of which grabs into the material of the insulator 4. For fixing the insulator 4 in the bore 1 6 other means can be foreseen, if required . At the rear end, the bore 1 6 ends into a flange 20 having an inner diameter D4 which is suitable to receive an outer shield 1 0 of the coaxial cable 8. A rear surface 2 1 (wall) of the insulator 4 of the connector 1 acts as a stop for the insulator 1 1 and/or the outer shield 1 0 of the coaxial cable 8. Depending on the field of application, the rear surface 21 may be flat as shown . Alternatively the rear surface 2 1 may have an annular shape which only is in partial contact with the insulator 1 1 and or the outer shield 1 0 of the coaxial cable 8. The rear surface 2 1 is preferably shaped such that it seals and actively prevents flow of soldering material in the direction of the core 9 of the coaxial cable 8.

In the shown embodiment, a second soldering depot 22 is attached to the rear end of the flange 20. The second soldering depot 22 at least partially reaches into the bore 1 6. The second soldering depot 22 is arranged spaced apart from the rear surface 2 1 by a distance L1 . Normally, the length of the distance L1 is in the range of 50-200% of the diameter D4. The distance L1 is chosen that under normal circumstances no soldering material contaminates the connector on the inside while attaching the connector 1 to the cable 8.

In an embodiment of a connector 1 as shown in Figures 6 to 1 0, the connector comprises a sleeve 27 which is located at a rear section 6 of an inner conductor 2 and in an assembled position at least partially encompasses a first soldering depot 1 2. The first soldering depot 1 2 is arranged inside a passage 1 3 of an insulator 4 of the connector 1 . The first soldering depot 1 2 is aligned such that it is in thermal contact with the rear section 6 of the inner conductor 2. This thermal contact may by a direct contact or may alternatively or in addition include thermal conduction in the sleeve 27. Further, the sleeve 27 comprises a third shoulder 28 which extends in radial direction inwards to the centre of the sleeve 27, as shown in Figures 7 to 1 0. As shown in Figure 9, the first soldering depot 1 2 is clamped between the shoulder 28 of the sleeve 27 and the rear section 6 of the inner conductor. Protrusion of melted soldering metal into the space between the core 9 of the coaxial cable 8 and the inner conductor 2 of the connector 1 may be promoted by blending or chamfering the edges of the rear section 6 and/or the first soldering depot 1 2, as shown in Figure 9. One advantage of a sleeve 27 that encompasses a first soldering depot 1 2 is, that the first soldering depot 1 2 is not in direct contact with the insulator 4 and hence wetting of the insulator 4 by melted soldering metal as well as thermal damage of the insulator or mechanical damage due to thermal expansion can be prevented . Furthermore a pre-defined contact pressure between the first soldering depot 1 2 and the rear section 6 may be applied by the sleeve 27, which increases the reproducibility of the soldering process.

In order to obtain an electrical connection between the shield 1 0 of the coaxial cable 8 and the outer conductor of the connector 1 , the jacket 30 of the coaxial cable 8 can partially be removed prior to the assembly of the connector 1 and the coaxial cable 8, as e.g . shown in Figure 7. An electrical connection between the shield 1 0 and the outer conductor then is established by heating a second soldering depot 22 arranged at the interface between the coaxial connector 1 and the jacket 30.

In the embodiment shown in Figures 6 to 1 0, the coaxial connector 1 comprises a projection 3 1 arranged at the outer conductor 3 which at least partially overlaps the second soldering depot 22 in mounted state. Such a projection is advantageous in order to keep the second soldering depot 22 in place while being heated, as well as it promotes protrusion of melted soldering material into the space between the shield 1 0 and the outer conductor 3. As shown in Figures 6 to 1 0, the inner conductor 2 may comprise a venting opening (bore) 26 which is aligned in radial direction at the rear section 6 of the inner conductor 2. This venting opening may be foreseen to improve capillary effects and to allow to discharge air trapped in the first opening 7.

5 As shown in Figures 6 to 1 0, the outer conductor 3 may in some embodiments also comprise a bushing 29 which is formed as a separate element subsequently connected to the outer conductor 2, e.g. by pressfit technology. The bushing 29 may comprise resilient tongues 3 1 .

Rather, the words used in the specification are words of description rather than i o limitation, and it is understood that various changes may be made without departing from the Spirit and scope of the invention .

LIST OF DESIGNATIONS

D 1 First diameter (front section 5) 1 5 First shoulder (of insulator 4)

D2 Second diameter ( rear section 6) 1 6 Bore (of outer conductor 3 )

D3 Third diameter (core of cable 8) 1 7 Second shoulder (of insulator 4)

D4 Fourth diameter (outer 1 8 Second barb (outer conductor conductor 3 ) 25 3 )

1 Connector 1 9 Inner wall (first opening 7 )

2 Inner conductor 20 Flange

3 Outer conductor 2 1 Rear surface

4 Insulator 22 Second soldering depot

5 Front section ( inner conductor) 30 23 Distal section (first opening 7 )

6 Rear section (inner conductor) 24 Dorsal section (first opening 7 )

7 First opening 25 Step (first opening 7 )

8 Coaxial cable 26 Opening (inner conductor 2)

9 Core (coaxial cable 8) 27 Sleeve

1 0 Shield (coaxial cable 8) 35 28 Third shoulder (of sleeve 27 )

1 1 Insulator (coaxial cable 8) 29 Bushing

1 2 First soldering depot 30 Jacket

1 3 Passage (insulator 4) 3 1 Projection

1 4 First barb (at rear section 6) 32 Tongues

Claims

PATENT CLAIMS

1. Coaxial connector ( 1 ) comprising: a. an outer conductor (3) and an inner conductor (2) positioned with respect to the outer conductor (3) by an insulator (4), wherein b. a first soldering depot (12) is arranged behind a first opening (7) of a rear section (6) of the inner conductor (2) and wherein c. said first opening (7) is foreseen to receive the soldering material of the first soldering depot (12).

2. The coaxial connector ( 1 ) according to claim 1 , wherein the first soldering depot (12) is arranged inside a passage (13) of the insulator (4).

3. The coaxial connector (1 ) according to claim 2, wherein the first soldering depot (12) is clamped between the rear section (6) and the insulator(4).

4. The coaxial connector ( 1 ) according to one of the previous claims, wherein the first soldering depot (12) has an annular shape.

5. The coaxial connector ( 1 ) according to one of the previous claims, wherein inner conductor (2) is clamped in the insulator (4).

6. The coaxial connector ( 1 ) according to one of the previous claims, wherein an outer diameter (D2) of the rear section (6) of the inner conductor (2) is about 0.5 mm to 2.5 mm larger then the diameter (D3) of the core (9) of the coaxial cable (8).

7. The coaxial connector ( 1 ) according to one of the previous claims, wherein the inner conductor (2) comprises a front section (5) having a female or a male plug.

8. The coaxial connector ( 1 ) according to claim 7, wherein the diameter (D2) of the rear section (6) is smaller then the diameter (D1 ) of the front section (5).

9. The coaxial connector ( 1 ) according to one of the previous claims, wherein the insulator (4) is inserted from a cable side into a bore (16) of the outer conductor (3).

10. The coaxial connector (1 ) according to claim 9, wherein the connector (1 ) comprises a stop arranged in the bore (16) having a diameter D4.

11. The coaxial connector (1) according to claim 10, wherein a second soldering depot (22) is arranged at a distance L1 from the stop.

12. The coaxial connector ( 1 ) according to claim 11 , wherein the distance L1 is in the range of 50-200% of the diameter D4 of the bore (16).

13. The coaxial connector ( 1 ) according to one of the previous claims, wherein the inner conductor (2) and/or the insulator (4) comprise a venting opening.

14. The coaxial connector ( 1 ) according to one of the previous claims, wherein the coaxial connector (2) further comprises a sleeve (27) that interconnects the first soldering depot (12) with the rear section (6) of the inner conductor (2).

15. The coaxial connector (1) according to claim 14, wherein the sleeve (27) at least partially encompasses the first soldering depot (12) and at least partially encompasses the rear section (6) of the inner conductor (2).

16. The coaxial connector ( 1 ) according to claim 14, wherein the first soldering depot (12) is clamped between the rear section (6) of the inner conductor (2) and the sleeve (27).

17. The coaxial connector ( 1 ) according to any of claims 14 to 16, wherein the sleeve (27) is located inside a passage (13) of the insulator (4).