Patent Application
20180261938
The present invention relates to a unitary RF connector.
Such a unitary connector can be used in particular to link two parallel printed circuit boards, usually called a board-to-board connection or even a printed circuit board (PCB) to another component such as a module or a filter.
The invention applies, for example, to a connection used to link boards inside RRU/RRH (remote radio unit/remote radio head) transmitter modules for the wireless communications market.
The invention also relates generally to the connection in the medical domain, the aeronautical or transport domain, the space domain or even the telecommunications domain.
By “RF connector”, it is to be understood a connector able to transmit signals from the Direct Current (DC) range to the radiofrequency (RF) range, including the hyperfrequency (HF) range, the signals being high speed digital signals (HSDL for High Speed Data Link) or radiofrequency (RF) signals.
With the continuous development of wireless communication technology, board to board connectors are becoming more and more widely used in wireless system module interconnection, such as communication base station, RRH, repeater, GPS devices, and other similar applications. Three major trends of wireless devices are smaller dimension, lower cost, and easier installation. For a board to board connection, the market also requires them to be smaller, cheaper and more modularized.
In particular, there are already on the market and in the prior art examples of connection assemblies dedicated to the telecommunications sector for cellular radiotelephony infrastructures. In fact, the trend in this market is to minimize the losses of the RF (radiofrequency) part in order to reduce the amplifying elements of the base stations. For this, on the one hand, the actual radio part of the stations is being increasingly relocated as close as possible to the transmission-reception antennas, in the RRU/RRH transmitter modules, and on the other hand, the RF leads internal to the radio unit are being replaced by direct interconnections.
So-called board-to-board connections have thus been developed according to the successive generations of the last decade.
A first generation of connection assemblies is thus known, for directly interconnecting boards, for example marketed under the names SMP, SMP-Com, MMBX from Radiall. Such connection assemblies respectively consist of a first socket of snap-fitting (or “snap”) type, a second socket of “sliding” (or smooth bore) type with a guiding cone (“slide on receptacle”), and a connection coupling called adaptor, with the first and second sockets respectively fastened to the ends thereof. The connection is therefore made blind by the re-centring of the connection coupling by means of the guiding cone of the sliding socket. The major drawback is the great limitation on the axial and radial misalignments allowed for these connections. In practice, the axial misalignment is limited to a few tenths of a millimetre, of the order of 0.3 mm to 0.6 mm, in order to keep the impedance of the coaxial line at a value equal to 50 Ohm. The radial misalignment is obtained by a rotation of the coupling in the groove of the snap-fitting socket, this rotation being in fact relatively small to avoid damaging the central contact and the elastic means with which the connection coupling is provided.
A second generation of connection assemblies is also known, for example marketed under the names SMP-MAX by the company Radiall or else marketed under the names MBX by the company Suhner or else marketed under the name AFI by the company Amphenol RF, or else marketed under the name Long Wipe SMP and P-SMP by the company Rosenberger.
Such connections, to link two printed circuit boards, generally consist of three elements, namely: a first socket of sliding type, a second socket with snap-fitting or of retention type and a connection coupling with the first and second sockets respectively fastened to the ends thereof.
The first and second sockets are conventionally made of brass and have no elastic functions. The connection coupling is typically made of an expensive noble elastic metallic material, for example CuBe2 or BZ4, and provided at each of its ends with elastic means (petals and slots for example) that cooperate with the first and second sockets.
This second generation of connections made it possible to increase the accepted axial misalignment value. Thus, as described in particular in the patent application WO 2010/010524, this increase can result from an impedance compensation at the coupling end, which makes it possible to obtain a trade-off in mechanical and electrical efficiency regardless of the inclination of the coupling relative to the sockets.
All the known board-to-board connections do however present a significant number of drawbacks.
On the one hand, because the couplings of these connections have elastic means generally consisting of petals at their ends, they can be fragile. Thus, it is commonplace, when connecting blind, for the coupling to be damaged when it comes into contact with the guiding cone of a sliding socket.
On the other hand, the configuration of the connections does not make it possible to obtain a sufficiently great radial and/or axial misalignment. In particular, significant rotation angles, typically greater than 3.5°, cannot be reached without causing an undesirable permanent deformation of the elastic means of the coupling. This permanent deformation causes a significant degradation of the electrical performance levels (electrical continuity), which de facto limits the radial misalignment allowed, in particular for a small distance between boards to be connected.
At last, the cost of producing these connections is relatively high, thus constituting a brake for this type of market. In particular, producing the connection coupling from a noble material, in particular when the coupling has a significant length, and producing possible slots in this coupling results in not-inconsiderable production costs.
In the case of the connection assembly according to the patent application WO 2010/010524, said connection needs in fact three different pieces which are connector elements, namely two receptacles which are each soldered on a PCB and one elongated rigid coupling to connect together the two receptacles. When applied in massive board to board connection, it might result of this type of solution a very big insertion force and make the connection between two PCB difficult.
Another current solution to realize a board to board connection is described in U.S. Pat. No. 6,231,352B1. Though it adopts only one connector to realize the board to board connection, it still needs soldering process to fix each longitudinal end of the connector on the PCB. This solution is not convenient for maintenance, when applied in different board to board heights. Besides, once the maintenance is done, the connector needs to be redesigned, with an impedance that is not necessarily well controlled. This solution is not good for applications which require some modularization and standardization.
There is therefore a need to further improve the board to board connections, in particular by providing the minimum of pieces required for the connection, by allowing an installation with less solder in order to improve the installation efficiency, an easy maintenance with the possibility to easily extract the connection, a certain misalignment tolerance, a controlled impedance line with good RF performances, the possibility of an easy standardization and modularization and, at low cost.
The invention aims to address all or part of these needs.
Thus, the subject of the invention, according to one of its aspects, is a unitary RF connector, intended in particular to link two printed circuit boards, comprising:
In other words, the invention consists in defining a one-piece connector with an electrically insulating block which serves as a rigid support for flexible conductive elements whose central portions are rigidly respectively held therein and/or on the outer wall of the block.
In the preferred embodiment, the central rigid RF line is constituted by at least:
According to this embodiment, the flexible RF line may be constituted by at least one free end of the first and the second strips.
In a variant, both free ends of each of the ground and the central contacts of the flexible RF line are incurved toward an end face the insulating body and being flexible such as they are each configured as a spring.
Alternatively, only one free end of each of the ground and the central contacts being flexible spring, the other free end of each of the ground and the central contacts being configured as a rigid tab in order to be weld to a contact of a complementary connection element.
According to an advantageous feature, each flexible end of the ground or central contact strip comprises an embossment forming a contact point.
The unitary RF connector according to the invention may comprise
According to an advantageous variant, each of the end faces of the insulating body comprises grooves, each groove being capable of accommodating a flexible end of the conductive element(s) of the flexible line in order to mechanically protect said element(s) even in case of a high pressure force of the complementary connection element.
The unitary RF connector may comprise advantageously an electromagnetic shield, which is retained outside the insulating body.
The central portion of the ground contact(s) may be shaped as a shell surrounding the insulating body and forming the electromagnetic shield.
According to an advantageous variant, the shield comprising flexible cuts or tabs allowing a floating mounting of the unitary connector into a holder.
The central contact may be made of high strength bronze, such as CuBe2
The ground contact(s) and eventually the electromagnetic shield may be made of stainless steel.
The main advantages obtained by the RF unitary connector according to the invention are numerous and can be itemized as follows:
According to another aspect, the invention concerns a connection module, intended to be used to link two printed circuit boards comprising:
Advantageously, the frame comprises a plurality of openings arranged in a single plane in each of which a unitary connector is accommodated according to a floating mounting.
The frame may comprise also a plurality of openings arranged in at least two stacked planes in each of which the unitary connector is accommodated according to a floating mounting.
According to another aspect, the invention concerns the use of the unitary RF connector described above or a connection module described above, to transmit RF (radiofrequency) signals or HSDL (High Speed Data Link) signals.
At last, the invention is related to a process for manufacturing a unitary connector described above, comprising the following steps:
The invention will be able to be better understood on reading the following description of exemplary and non limiting implementations thereof, and on studying the appended figures in which:
A strip 3 forming a central contact comprises a central portion 30 which is retained inside the insulating body 2 and two free ends 31, 32 which are arranged outside the insulating body. Both free ends 31, 32 of the central contact 3 are each incurved toward an end face 21, 22 of the insulating body 2. Both free ends 31, 32 are flexible such as they are each configured as a spring. Each flexible end 31, 32 of the central contact strip 3 comprises an embossment 33, 34; forming a contact point.
Two other strip 4; 5 forming together the ground contact, are entirely arranged and retained outside the insulating body 2. The two free ends 41, 42; 51, 52 of each ground contact 4, 5 are incurved toward an end face 21, 22 the insulating body. They are arranged parallel to the free ends 31, 32 of the central contact strip 3. Both free ends 41, 42; 51, 52 are also flexible such as they are each configured as a spring.
From a RF point of view, each side of the flexible portions of the strips, 31, 41 and 51 on one hand, 32, 42 and 52 on the other hand, delimits a flexible RF line B1 or B2, such as shown on
In a preferred embodiment; the central RF line A is dimensioned such that it can be described as a micro-strip line type. The conductive strips 3, 4, 5 have a typical thickness from 0.05 up to 0.25 mm and a typical width from 0.5 to 2.5 mm.
According to the invention, each of the contact springs 31, 32; 41, 42; 51, 52 is able to flex toward one of the end face 21, 22 of the insulating body 2 taking any closer position when acted upon by the pressure force of a complementary connection element.
As shown in detail on
In an advantageous way, each flexible end 31, 32; 41, 42; 51, 52 of the ground or central contact strip comprises an embossment 33, 34; 43, 44; 53, 54 forming a contact point. This contact point defines a precise electrical contact with a contact of a complementary connection element, such as a conductive track of a PCB.
Preferably, the central portion of the ground contacts 4, 5 are shaped as a shell 6 surrounding the insulating body 2 and forming an electromagnetic shield of the central rigid RF line A. In other words, the ground contacts 4, 5 are made in a single piece 6 in which not only the free ends 41, 42; 51, 52 are cut but also a protective shield.
According to an advantageous variant shown on
By “floating mounting”, it is to be understood the usual technological meaning, i.e. a mounting allowing a certain displacement in translation of the unitary connector(s) into the frame.
In the illustrated example of
In the illustrated example of
The functions of this holder 7 are as follows:
The holder 7 is preferably in plastics material but it can also be in metal.
As shown on
As a sum-up, two parallel PCB1, PCB2 can realize a good electrical contact through compression of the contact points. The coplanar signal transmission between PCB1 and PCB2 can be realized by controlling the width of the free ends 31, 32; 41, 42; 51, 52 as well as their gap. As a result, good RF or HSDL signal performances are guaranteed. The floating mounting of the unitary connectors enables the equilibrium of forces and divides equally the compression of the spring in each free end.
The height of the holder 7 could be up to 20 or 25 mm, whereas the height of a unitary connector 1 may be of 4 mm, 5 mm and 7 mm.
A same holder 7 may accommodate a large number of unitary connectors 1.
Thus, as shown on
As shown on
A second embodiment of a unitary connector 1 is shown on
On the contrary, the other free ends 32, 42, 52 are each configured as a rigid tab in order to be welded S to a contact of a complementary connection element PCB2.
In this second embodiment according to which one end 22 of the unitary connector is to be welded on the PCB, there is provided a picking pad 24 which is used to position the unitary connector on the PCB2 with a conventional “pick and place” equipment.
On
Another variant is shown on
The variant shown of the
Other variants and enhancements can be provided without in any way departing from the framework of the invention.
The expression “comprising a” should be understood to be synonymous with “comprising at least one”, unless otherwise specified.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2015/090933 | 9/28/2015 | WO | 00 |
