EP0970547B1

EP0970547B1 - Coaxial connector for circuit board

Info

Publication number: EP0970547B1
Application number: EP98905591A
Authority: EP
Inventors: Dieter Bozzer; Sébastien Kempter; Blaise Rithener; Lionel Thomas
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1997-03-25
Filing date: 1998-03-18
Publication date: 2002-02-20
Anticipated expiration: 2018-03-18
Also published as: CN1252899A; DE69803920T2; AU6111998A; GB9706155D0; JP2001518231A; EP0970547A1; DE69803920D1; CN1104064C; WO1998043323A1

Abstract

A coaxial connection assembly for interconnecting printed circuit boards (8, 10) comprises a first connector (4) and a second connector (6). The first connector (4) comprises an axially resiliently movable inner contact (12) that abuts directly against a conductive circuit trace on the mating board (10). The second connnector (6) comprises a single piece conductive part surface mounted on the board (10) for plugging connection with the first connector outer conductor (16). A compact, cost-effective and simple coaxial connection assembly is thus achieved.

Description

This invention relates to a coaxial connection assembly for interconnection to a circuit board.
Coaxial interconnection systems typically comprise an inner conductor concentrically surrounded by an outer conductor and separated therefrom by a dielectric. Such interconnection systems permit transmission of high speed electrical signals. The concentric arrangement of the outer conductor has a shielding effect that limits the radiation of electro-magnetic noise. When interconnecting a coaxial conductor to circuit traces on a printed circuit board, it is no longer possible to maintain the coaxial arrangement on the printed circuit board in view of its planarity.
It is nevertheless desirable to maintain the coaxial concentric arrangement of the conductors as far as possible in the interconnection system in order to reduce the emission of electro-magnetic noise. It is also desirable to produce a cost-effective interconnection that is also compact but nevertheless adjusts for dimensional tolerance. The latter is important in connections to circuit boards, or interconnections between circuit boards where the miniaturization of components is a continuous requirement, the relative tolerances in positioning between mating components thereby increasing.
In the US-A-5,180,315, an assembly is disclosed from which the subject matter of the pre-characterizing portion of claim 1 is known. A surface mounted, high frequency coaxial connector is described that includes a housing with an inner terminal defining the central contact and an outer terminal made of a cylinder providing the ground contacts. This coaxial connector can be mounted on an printed circuit board by surface mount technology.
US-A-5,145,382 discloses an electrical connector for interconnecting to a printed circuit board surface and a second coaxial connector for connecting with the first electrical socket. The electrical socket comprises a plated center contact portion and can be surface mounted on the printed circuit board. The electrical socket also has a plated ground contact portion. The inner and outer conductors of the second coaxial connector can be connected to the plated contact portions of the first electrical socket that is surface mounted on the printed circuit board.
It is an object of this invention to provide an improved coaxial connection assembly for coupling a coaxial conductor to a circuit board. It would be advantageous for such connection system to be cost-effective, compact and reliable, particularly to ensure effective electrical interconnection to a circuit board.
It would also be advantageous to provide such a coaxial connection assembly for interconnecting a pair of circuit boards in a particularly compact and effective manner.
Objects of this invention have been achieved by providing the coaxial connection assembly according to claim 1. Disclosed herein is an electrical coaxial connection assembly comprising a first coaxial connector having a center conductor and concentrically therearound an outer conductor separated therefrom by a dielectric housing, and a second connector comprising an outer conductor for pluggably mating with the outer conductor of the first connector, the second connector comprising an outer contact mounted on a circuit board for electrical connection to an outer circuit trace thereon, wherein the inner conductor of the first connector is resiliently biasable against an inner circuit trace of the circuit board arranged substantially centrally with respect to the outer conductor of the second connector.
Advantageously, few parts are required as the inner conductor of the first connector contacts directly on the circuit board. Also, as the inner conductor is resiliently biasable, tolerances in the distance between connectors can be absorbed.
The outer conductors, for example the outer conductor of the second connector may be provided with a plurality of flexible cantilever beam arms arranged concentrically, that absorb a certain tolerance in the radial direction of the connectors.
The outer conductor of the second connector may be formed of a single piece conductive material directly mounted, for example surface mounted and soldered, or alternatively with compliant pins, to the conductive circuit trace of the circuit board, such that a particularly cost-effective arrangement is achieved. The flexible contact arms of the outer conductor may be provided upstanding substantially orthogonally from a circular shaped base with a substantially uninterrupted connection surface, except for a portion allowing passage of the circuit board inner conductive trace therepast. The base may serve as an electrical and mechanical connection to a substantially circular circuit pad on the circuit board. A strong mechanical connection, as well as a good electrical connection with reduced electro-magnetic noise emission is thus achieved.
The outer conductor of the first connector may also be provided as a substantially cylindrically shaped (tubular) conductor for example stamped and formed from sheet metal, having a substantially circular connection surface or contact pad for electrical and mechanical connection against a substantially circular foot print of a circuit trace on a circuit board. The foot print could be interrupted to allow passage of the inner conductor from the inside to the outside of the circle. The inner conductor may be a substantially cylindrical part slidably movable within the housing in the mating direction of the connectors, a separate stamped and formed spring member abutting thereagainst in order to provide the spring force and additionally electrical connection to a circuit trace on a circuit board.
Further advantageous aspects of the invention are described in the claims, or will be apparent from the following description and drawings.
An embodiment of this invention will now be described by way of example, with reference to the drawings, in which;
Figure 1 is a cross-sectional isometric view of a connection assembly in a fully mated condition;
Figure 2 is a cross-sectional view similar to that of Figure 1 of the connection assembly in an unmated condition;
Figure 3 is a cross-sectional view of a first connector of the connection assembly;
Figure 4 is a view in the direction of arrow 4, Figure 3;
Figure 5 is a view in the direction of arrow 5 of Figure 3;
Figure 6 is a plan view of a portion of printed circuit board showing the circuit traces for connection to the first connector;
Figure 7 is a cross-sectional view through a second connector of the assembly;
Figure 8 is a cross-sectional view through lines 8-8 of Figure 7;
Figure 9 is a view in the direction of arrow 9 of Figure 8;
Figure 10 is a plan view of a portion of a portion of a printed circuit board with circuit traces thereon for connection to the second connector.
Referring to the Figures, and particularly Figures 1 and 2, an electrical connection assembly 2 comprises a first coaxial connector 4 and a second connector 6 matable therewith. The first coaxial connector 4 is mounted on a first circuit board 8, and the second coaxial connector 6 is mounted on a second circuit board 10.
The first connector 4 comprises an inner conductor 12, a dielectric housing 14, and an outer conductor 16. The inner conductor is a substantially cylindrical part slidably mounted in a cavity 18 of the housing, and having a contact 20 protruding beyond a mating end 22 of the connector housing. The inner conductor 12 extends in an axial direction A, which is the direction of coupling of the connectors 4,6, towards a connection end 24 of the connector, the connection end proximate or in abutment with the circuit board 8. The mounting end 26 of the inner conductor 12 has an enlargened portion that forms a retention shoulder 28 for abutment against a shoulder 30 of the housing 2 limit the outward extension of the contact 20 beyond the mating face 22. An abutment surface 32 of the contact mounting end 26 is in abutment with a spring member 34 that urges the inner contact towards the mating connector.
In this embodiment, the spring member 34 stamped and formed from resilient sheet metal having a retention section 36 for fixing to the housing, and a resilient cantilever beam spring arm 38 extending therefrom for abutment against the inner contact. The spring member 34 is also a contact member and has a contact section 40 in the shape of a surface mount contact pad extending from the retention section 36 on an opposed side to the spring arm 38 for surface mount solder connection to a corresponding circuit trace of the circuit board 8. The contact member 34 thus interconnects the inner contact 12 electrically to the circuit board. It would also be conceivable to integrally stamp and form an inner contact extending from the contact arm 38 in the axial direction A through the cavity 18 and having an arcuate formed contact portion. It may be that such construction is more cost-effective than providing the two-part construction shown in the present embodiment.
The retention section 36 comprises a pair of lances 42 for engaging in opposed side walls 44,46 of an axially extending slot 48 in the housing 14, such that the contact member 34 can be assembled by simply pushing it in the axial direction into the housing from the mounting face 24. As best seen in Figure 4, the oblique opposed lances 42 of the retention section 36 extend laterally from either edge of the contact arm 34.
The outer conductor 16 may also be stamped and formed from sheet metal and have a substantially cylindrical shape extending from proximate the mating face 22 to the mounting face 24, and comprising a substantially circular contact pad 50 extending orthogonally from the cylindrical portion 52. The contact pad 50 is for a surface mount solder connection to a conductive circuit trace 54 (see Figure 6) for electrical and mechanical connection thereto. The circuit trace 54 forms the outer circuit trace, and there is also an inner circuit trace 56 for solder connection to the inner contact pad 40. The outer circuit trace 54 flanks either side of the inner trace 56 and provides some shielding effect thereby. The outer contact 50 does not form a full circle as it is interrupted by the portion of housing 54 within which the inner contact arm 34 is received and extends through the outer conductor. The outer conductor 52, is, at the mating end, inwardly bent or tapered 60 forming a guide surface for locating the mating connectors and simultaneously retaining the housing firmly within the outer conductor.
Referring to Figure 2 and Figures 8-10, the second connector 6 comprises an outer conductor 61 extending from a mounting end 62 to a mating end 64 in the axial direction A, and comprising a substantially cylindrical shaped wall 66 having a circular contact pad 68 at the mounting end 62. The contact pad 68 extends substantially orthogonally (radially) from the wall 66 and is for surface mount electrical and mechanical connection to a circular contact trace 70 on the second circuit board 10. The contact pad 68 is interrupted by a recess 72 in order to allow passage of the inner circuit trace 74 on the board 70 therethrough. The inner circuit trace forms the inner conductor or contact of the second connector.
The outer wall 66 is interrupted by slots 76 extending axially from the mating end 64 such that the outer wall is formed into a plurality of cantilever shaped spring arms 78 for resilient contact with the outer conductor 16 of the mating connector 4. At the mating end 64, the outer conductor is provided with inwardly extending protrusions 80 to form the contact surfaces with the complementary connector. The protrusions 80 also have a tapered surface 82 for guiding the mating connectors during the initial phase of coupling. Due to the flexibility of the arms 78, a certain amount of radial tolerance between the mating connectors is acceptable.
The second connector 6 can thus be formed from a single conductive member for a particularly cost-effective arrangement, whereby the center contact 12 of the mating connector abuts directly against a central pad 84 of the inner circuit trace 74 that forms the centre contact of the second connector. As the inner contact 12 is resiliently axially movable, adjustment for certain tolerances in the position of coupling in the axial direction A can be absorbed. Furthermore, the contact end 20 of the inner contact abuts against the circuit trace 84 with a defined and controlled contact force in view of the flexible contact arm 34. The latter arrangement also ensures that a particularly compact arrangement both in the height (i.e. in the axial direction A) and also in the radial direction (i.e. orthogonal to the direction A) of the connection assembly is achieved. In particular, the latter is achieved by direct contact of the inner contact with the circuit board, and the provision of the second contact 6 as a simple cylindrical part that is mounted directly on the circuit board and contacts directly the mating connector without provision of a housing structure.
It would also be conceivable to provide the first connector 4 connected to a cable or other structure whilst maintaining the advantages of compact and cost effective connection to the second board 10, therefore it is not necessary for the invention to provide the first connector 4 on a circuit board although the advantages described above are particularly applicable to the parallel board-to-board arrangement shown in the particular embodiment.

Claims

An electrical coaxial connection assembly (2) comprising a first coaxial connector (4) having a center conductor (12) and concentrically therearound an outer conductor (16) separated therefrom by a dielectric housing (14), and a second connector (6) for pluggably mating with the first connector, the second connector mounted on a second circuit board (10) and having an outer conductor (61,70) for electrical connection to the outer conductor of the first coaxial connector, and an inner conductor (74,84) for connection to the centre conductor (12) of the first connector, wherein the centre conductor (12) of the first connector is resiliently biasable directly against the inner conductor of the second connector, the assembly being characterized in that the inner conductor (74,84) of the second connector is formed as a circuit trace (74,84) on the second circuit board.
The assembly of claim 1, further characterized in that the inner conductor (74,84) of the second connector comprises a circuit trace pad (84) centrally positioned with respect to the outer conductor (61,70) for resilient abutment of the first connector centre conductor (12) thereagainst.
The assembly of claim 1 or 2, further characterized in that the outer conductor (61) of the second connector comprises a substantially cylindrical outer wall (66) extending from a mounting end (62) to a mating end (64), the outer conductor further comprising a contact pad (68) at the mounting end (62) mountable on a circuit trace (70) on the second circuit board (10) for electrical connection thereto.
The assembly of claim 3, further characterized in that the contact pad (68) forms substantially a full circle except for at least one passage (72) to enable the inner circuit trace (74) to pass therethrough.
The assembly of any one of the preceding claims, further characterized in that the second connector outer conductor is formed from a single conductive part mounted on the circuit board, for pluggably receiving and holding the outer conductor of the first connector during coupling.
The assembly of any one of the preceding claims, further characterized in that the first coaxial connector (4) comprises a spring member (34) having a mounting section (36), a contact pad (40), and a spring section (38) for biasing the inner conductor, the contact pad (40) of the spring member (34) for connection to a complementary conductor for electrically interconnecting the inner conductor (12) thereto.
The assembly of the preceding claim, further characterized in that the contact pad (40) of the first coaxial connector is for surface mount connection to an inner circuit trace (56) of a first circuit board (8).
The assembly of either of claims 6 or 7, further characterized in that the spring member (38) is in the shape of a cantilever beam extending from the mounting section (36).
The assembly of any one of the preceding claims, further characterized in that the outer conductor (16) of the first coaxial connector (4) comprises a substantially circular contact pad (50) extending radially from the outer conductor at a mounting end (24) of the connector for electrical and mechanical solder connection to a substantially circular portion (54) of an outer circuit trace on the first circuit board (8).
The assembly of any one of claims 5-7, further characterized in that the spring member (34) has the mounting section (36) intermediate the contact pad (40) and the spring arm (38).