EP0971441A1

EP0971441A1 - Cable adapter

Info

Publication number: EP0971441A1
Application number: EP98112886A
Authority: EP
Inventors: Walter Methe; Jens Dungs; Klaus Dr. Helmreich
Original assignee: Advantest Europe GmbH
Current assignee: Advantest Europe GmbH
Priority date: 1998-07-10
Filing date: 1998-07-10
Publication date: 2000-01-12
Also published as: KR20000011531A; TW434955B; JP2000040543A

Abstract

The invention relates to a cable adapter (1) for a connection between a printed circuit board (2) and a coaxial cable (3) with only an ground pin (10) and means (11) for receiving the coaxial cable (3) which are constructed in such a way that the inner conductor (30) of the received coaxial cable (3) is spaced from the ground pin (10) so that - when the cable adapter is assembled - the inner conductor (30) and the ground pin (10) can be inserted into two correspondingly spaced pin holes (20, 21) on the printed circuit board (2).

Description

The invention relates to the connection between a printed circuit board and a coaxial cable.
There is a requirement to make a connection between a coaxial cable and a single-layer or multi-layer printed circuit board, where high-frequency signals of up to several GHz are to be transmitted via the coaxial cable. A solution according to Figure 2 is known in the art, in which the inner conductor 30 of the coaxial cable 3 is inserted into a corresponding bore 20 on the printed circuit board 2 and soldered. The ground connection is created by baring the shield 32 of the coaxial cable 3 above the printed circuit board, twisting it together into a cord and inserting and soldering it into a corresponding bore 21 for the ground connection on the printed circuit board. Another construction which is known in the art provides first of all for a cable to be soldered onto the shield and then to be inserted and soldered with its other end in the printed circuit board.
However, both variants have the disadvantage that the coaxial cable is not shielded above the printed circuit board over a relatively long length, which has a disadvantageous effect on the transmission properties.
A further disadvantage is also to be seen in the fact that the coaxial cable which is soldered on can easily bend, thereby further impairing the transmission properties, or even break.
The object of the invention, therefore, is to create a connection between coaxial cable and printed circuit board which has better transmission properties and improved mechanical stability than the known solutions described above.
According to the invention this object is achieved by the features of Claim 1. Further embodiments of the invention are the subject matter of the subordinate claims.
According to the invention a cable adapter for the connection between a printed circuit board and a coaxial cable is provided which has only an ground pin and means for receiving the coaxial cable, the receiving means being constructed in such a way that the inner conductor of the received coaxial cable is spaced from the ground pin so that - when the cable adapter is assembled - the inner conductor and the ground pin can be inserted into two correspondingly spaced pin holes on the printed circuit board and then will be soldered.
With the aid of the cable adapter the unshielded region of the coaxial cable can be reduced to a minimum, resulting in corresponding improvement in the transmission and crosstalk properties. Moreover, reproducible connections with high mechanical stability can be created with the cable adapter.
Further advantages and embodiments of the invention are explained in greater detail with reference to the description of two embodiments and to the drawings, in which:
Figure 1 shows a sectional representation of the cable adapter according a first embodiment, assembled on a printed circuit board,
Figure 2 shows a sectional representation of the connection between coaxial cable and printed circuit board according to the prior art,
Figure 3 shows a side view of the cable adapter according to the first embodiment,
Figure 4 shows a sectional representation along the line IV-IV of Figure 3,
Figure 5 shows a bottom view of the cable adapter according to Figure 3,
Figure 6 shows a top view of the material blank for a cable adapter according to a second embodiment,
Figure 7 shows a front view of the cable adapter according to the second embodiment and
Figure 8 shows a bottom view of the table adapter according to Figure 7.
In Figures 1, 3, 4 and 5 a cable adapter 1 according to a first embodiment is shown which serves as connection between a printed circuit board 2 and a coaxial cable 3.
The cable adapter 1 has in particular an ground pin 10 and means 11 for receiving the coaxial cable 3, the receiving means 11 being constructed in such a way that the inner conductor 30 of the received coaxial cable 3 is spaced from the ground pin 10, so that - when the cable adapter 1 is assembled - the inner conductor 30 and the ground pin 10 can be inserted into to correspondingly spaced pin holes 20, 21 on the printed circuit board 2.
The cable adapter 1 is also provided with a support surface 12 with which it is supported on the printed circuit board 2 and which enables vertical fitting of the cable adapter on the printed circuit board, the support surface is advantageously provided in the region of the ground pin 10. In the illustrated embodiment the ground pin projects approximately centrally and vertically out of the support surface 12.
The means 11 for receiving the coaxial cable 3 are constructed as a sleeve with a through bore 13 into which the coaxial cable 3 can be inserted. The through bore 13 has a first region 13a with a first diameter and a second region 13b with a smaller second diameter.
From the inside outwards, the coaxial cable consists in a known manner of an inner conductor 30, a dielectric 31, a shield 32 and a jacket 33. The two regions 13a, 13b of the through bore 13 are dimensioned in such a way that the first diameter of the first region 13a is slightly greater than the diameter of the shield and the second diameter of the second region 13b is slightly greater than the diameter or the dielectric 31.
For the connection of the coaxial cable 3 to the cable adapter 1 and the printed circuit board 2 the coaxial cable 3 is prepared in accordance with Figure 1 so that the end or the coaxial cable 3 is formed by a bared inner conductor 30, the length of the bared inner conductor being somewhat greater than the thickness of the printed circuit board 2. As the next section there follows a region in which the inner conductor 30 is cladded with the dielectric 31 which, when the cable adapter 1 is assembled, extends from the beginning of the second region 13b as far as the surface of the printed circuit board. Moreover, in the first region 13b of the through bore 13 the shielding is still present. Outside the cable adapter 1 the coaxial cable also still has the jacket 33.
For fixing the coaxial cable 3 in the cable adapter 1, the receiving means 11 have a transverse bore 14 which opens in the first region 13a of the through bore 13. Thus the transverse bore 14 opens in the region in which the shield of the coaxial cable 3 is bared. Thus by way of this transverse bore 14 the coaxial cable 3 can be soldered to the cable adapter 1. The cable adapter 1, which is made from electrically conductive material, hereby produces the electrical connection between shield 32 and ground pin 10.
The cable adapter 1 is advantageously produced in one piece from electrically conductive material, and between the receiving means 11 and the ground pin 10 there is provided a transverse piece 15, at one end of which the ground pin 10 extends perpendicular thereto in one direction and at the other end the receiving means 11 extend perpendicular thereto in the other direction.
With the support surface 12 provided in the region of the ground pin 10 the cable adapter 1 is supported on the printed circuit board 2 in such a way that between the printed circuit board 2 and the opposing end of the receiving means 11 a slot with a defined slot height a remains. This slot ensures that the soldering does not cause a short circuit between inner conductor 30 and ground.
The size of the support surface 12 with which the cable adapter 1 is supported on the printed circuit board 2 is advantageously at least 25%. preferably at lest 30% of the total area of the cable adapter, as can be seen from Figure 5. In this way it can be ensured that by light pressing the cable adapter 1 can be vertically aligned above the support surface and can be soldered on in this position.
In this way it is also ensured that the slot height a is fixed by the geometry of the cable adapter 1 and can be reproduced again and again during soldering. With a suitable choice of the slot height a the connection impedance of the connection can be adapted for example to 50 Ω for a specific application.
The cable adapter 1 illustrated in Figures 1, 3, 4 and 5 is produced as a turned/milled part.
Figures 7 and 8 shows a cable adapter according to a second embodiment which has been produced as bent sheet material part from a flat material blank (see Figure 6). For ease of understanding, the same reference numerals are used for equivalent components.
This cable adapter also consists of only an ground pin 10 and means 11 for receiving the coaxial cable which are constructed in such a way that the inner conductor of the received coaxial cable is spaced from the ground pin so that - when the cable adapter is assembled - the inner conductor and the ground pin can be inserted into two correspondingly spaced pin holes on the printed circuit board.
In the construction as a bent sheet material part, the through bore 13 has no inner graduation. Nevertheless a lateral opening corresponding to the transverse bore 14 is provided, via which the inserted coaxial cable can be soldered to the receiving means 11.
The cable adapter illustrated in Figures 6, 7 and 8 should be regarded merely as an example. Especially when it is produced as a bent sheet material part a large number of variants are conceivable.
However, a significant aspect is also again the construction of a support surface 12, which makes possible a defined vertical alignment of the cable adapter on the printed circuit board 2. In the illustrated embodiment the support surface 12 is formed by two clips which are bent in opposite directions (see Figure 8). Also in this embodiment in the assembled state of the cable adapter a slot with a slot height a remains between the printed circuit board and the lower end of the receiving means 11.
The cable adapter according to the invention can also be produced by transfer moulding or sintering.
The cable adapters according to the invention have substantially better transmission and crosstalk properties than the known solution according to Figure 2. In a transmission measurement (S21 parameter) it was possible to improve the -3 dB limit from 2 GHz to 4GHz.
In addition, the cable adapter offers a substantially higher stability of the cable/printed circuit board connection, so that bending or breaking of the cable can be avoided. The means for receiving the coaxial cable also act as shielding in the region where the dielectric 31 is exposed, so that it is only in the region of the slot between the means 11 and the printed circuit board 2 that there is no shielding. The substantially improved shielding which results from this by comparison with the embodiment according to Figure 2 also results in a lower inductance of the connection.
When the coaxial cable 3 is assembled on the printed circuit board 2 this latter is first of all soldered on the cable adapter 1 via the opening 14. Then the ground pin 10 and the inner conductor 30 are inserted into the corresponding pin holes 20, 21 on the printed circuit board 2. By gentle pressing on of the cable adapter above the support surface 12 the cable adapter is aligned and can he soldered on.

Claims

Cable adapter (1) for a connection between a printed circuit board (2) and a coaxial cable (3) with only an ground pin (10) and means (11) for receiving the coaxial cable (3) which are constructed in such a way that the inner conductor (30) of the received coaxial cable (3) is spaced from the ground pin (10) so that - when the cable adapter is assembled - the inner conductor (30) and the ground pin (10) can be inserted into two correspondingly spaced pin holes (20, 21) on the printed circuit board (2).
Cable adapter as claimed in Claim 1, characterised in that a support surface (12) is provided with which the cable adapter (1) is supported on the printed circuit board (2) and which makes possible vertical fitting of the cable adapter on the printed circuit board.
Cable adapter as claimed in Claim 1, characterised in that a support surface (12) is provided with which the cable adapter (1) is supported on the printed circuit board, wherein the ground pin projects vertically out of the support surface (12).
Cable adapter as claimed in Claim 1, characterised in that the means (11) for receiving the coaxial cable (3) are constructed as a sleeve with a through bore (13) into which the coaxial cable (3) can be inserted.
Cable adapter as claimed in Claim 1, characterised in that a support surface (12) is provided with which the cable adapter is supported on the printed circuit board (2) in such a way that between the printed circuit board (2) and the opposing end of the receiving means (11) a slot with a defined slot height (a) remains.
Cable adapter as claimed in Claim 1, characterised in that the means (11) for receiving the coaxial cable (3) are constructed as a sleeve with a through bore (13) into which the coaxial cable (3) can be inserted, wherein the through bore (13) has a first region (13a) with a first diameter and a second region (13b) with a smaller second diameter.
Cable adapter as claimed in Claim 1, characterised in that the means (11) for receiving the coaxial cable (3) are constructed as a sleeve with a through bore (13) into which the coaxial cable (3) can be inserted, wherein the sleeve has a transverse bore (14) for soldering on of the coaxial cable (3) inserted into the sleeve.
Cable adapter as claimed in Claim 1 , characterised in that the cable adapter is produced in one piece from electrically conductive material.
Cable adapter as claimed in Claim 1, characterised in that the cable adapter is produced as a turned/milled part.
Cable adapter as claimed in Claim 1, characterised in that the cable adapter is produced as a bent sheet material part.
Cable adapter as claimed in Claim 1, characterised in that a support surface (12) is provided with which the cable adapter is supported on the printed circuit board (2), wherein the support surface advantageously amounts to at least 25%, preferably at least 30% of the total area of the cable adapter.
Cable adapter as claimed in Claim 1, characterised in that the means (11) for receiving the coaxial cable (3) are constructed as a sleeve with a through bore (13) into which the coaxial cable (3) can be inserted, wherein the through bore (13) has a first region (13a) with a first diameter and a second region (13b) with a smaller second diameter and wherein the coaxial cable consists of jacket (33), shield (32) dielectric (31) and inner conductor (30) and the first diameter of the first region (13a) is slightly greater than the diameter of the shield (32) and the second diameter of the second region (13b) is slightly greater than the diameter of the dielectric (31).
Cable adapter as claimed in Claim 1, characterised in that the means (11) for receiving the coaxial cable (3) are constructed as a sleeve with a through bore (13) into which the coaxial cable (3) can be inserted, wherein the through bore (13) has a first region (13a) with a first diameter and a second region (13b) with a smaller second diameter and wherein the sleeve also has a transverse bore (14) which opens in the first region (13a) of the through bore (13).
Cable adapter as claimed in Claim 1, characterised in that a transverse piece (15) is also provided, at one end of which the ground pin (10) extends perpendicular thereto in one direction and at the other end the means (11) for receiving the coaxial cable (3) extend perpendicular thereto in the other direction.