Abstract:
The invention relates to a high frequency board-to-board connector for interconnecting electronic sub-assemblies. The high frequency board-to-board connector includes a row of conductive pins received in an insulative housing for connecting with receptacles of a design. Two discrete electronic sub-assemblies, for example PCBs, can be mechanically and electrically connected without the need for a gender male connector on one PCB and a corresponding gender female connector on the other PCB. A plurality of follower arms spaced apart along the grounding plate facilitates contact with a ground plane in the design to form a ground path. The ground path reduces electromagnetic coupling between any pair of conductive pins and consequentially lowering cross-talk noise. Furthermore, inductive parasitics of the conductive pins is reduced, further facilitating high frequency operations.

Description:
FIELD OF INVENTION 
     The present invention relates generally to an electrical connector. In particular, the invention relates to an electrical connector for interconnecting electronic sub assemblies, for example printed circuit boards, for use in high-frequency operations. 
     BACKGROUND 
     Electronic sub-assemblies, for example printed circuit boards (‘PCBs’), are interconnected using electrical connectors. Conventionally, the electrical connector is designed to address mechanical and reliability issues. The electrical connector typically comprises an array of pins connecting the signal bearing tracks of one PCB to another PCB. Due to technological advances, higher speed circuitries have arisen, in turn giving rise to higher speed digital signal transmissions. If not properly implemented, the reduction in the rise and fall time of high-frequency digital signals propagating on the PCB may lead to a compromise in signal integrity, for example cross-talk noise and signal distortions due to impedance mismatch. As the clock frequency of the signal increases, more energy is distributed over the higher frequency spectrum which consequently creates a greater demand for a larger bandwidth. 
     Since the electrical connector bridges the signal propagation paths between PCBs, it therefore affects the total bandwidth required for the entire interconnected paths. 
     Therefore, there is a need to design a high frequency board-to-board connector for replacing electrical connectors. It is important that the high frequency board-to-board connector should include a construction that provides a low insertion loss and the capability to reduce crosstalk noise between neighbouring pins. 
     Hence, this clearly affirms a need for a high frequency board-to-board connector. 
     SUMMARY 
     A high frequency board-to-board connector based on an embodiment of the invention, includes an array of conductive pins received in an insulative housing for connecting with a design. The conductive pins are conventional connecting pins that includes but are not limited to a type of encirclement compression (ECOM) pin for insertion into receptacles formed by plated vias in the design. As the conductive pins connects directly to vias, also known as through-holes, in the design, two discrete electronic sub-assemblies, for example PCBs, can be mechanically and electrically connected without the need for a connector on one PCB and a corresponding connector on the other PCB. 
     A grounding plate is coupled to the insulative housing. One or more arms extend from the grounding plate. The independent bending motion of each arm facilitates contact with the ground plane. The grounding plate and the ground plane are connected to form a ground path for reducing electromagnetic coupling between conductive pins during high frequency operations. 
     Therefore in accordance with a first aspect of the invention, there is disclosed a high frequency board-to-board connector for connecting with a design comprising: 
     an insulative housing having a design-mounting face; 
     a first conductive element received in the insulative housing for connecting to a corresponding second conductive element in the design, the first conductive element having a tail for coupling to a corresponding conductive pad on an electronic sub-assembly, the high frequency board-to-board connector being connectable to the electronic sub-assembly; and 
     a grounding element for mounting onto the insulative housing, the grounding element comprising: 
     a grounding body; and 
     one or more follower arms coupled to the grounding body, each follower arm being resiliently biased and for connecting to a ground plane in the design. 
     In accordance with a second aspect of the invention, there is disclosed a high frequency board-to-board connector for connecting with a design comprising: 
     an insulative housing having a design-mounting face; 
     a first conductive element received in the insulative housing for connecting to a corresponding second conductive element in the design, the first conductive element having a tail for coupling to a corresponding conductive pad on an electronic sub-assembly, the high frequency board-to-board connector being connectable to the electronic sub-assembly; and 
     a grounding element for mounting onto the insulative housing, the grounding element comprising one or more follower arms for connecting to a ground plane in the design. 
     In accordance with a third aspect of the invention, there is disclosed a high frequency board-to-board connector for interconnecting a pair of designs comprising: 
     an insulative housing; 
     a first conductive element received in the insulative housing, the first conductive element having first and second distal ends, the first distal end for connecting to a corresponding second conductive element in one design, and the second distal end for connecting to a corresponding third conductive element in the other design; and 
     a grounding element for mounting onto the insulative housing, the grounding element comprising: 
     a grounding body; 
     one or more first follower arms coupled to the grounding body for connecting to a ground plane in one design; and one or more second follower arms coupled to the grounding body for connecting to a ground plane in the other design. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention are described hereinafter with reference to the following drawings, in which: 
     FIG. 1 is a front view of a high frequency board-to-board connector with a partial sectional view of an insulative housing; 
     FIG. 2 is a reverse view of the high frequency board-to-board connector of FIG. 1, with a grounding element exposed; 
     FIG. 3 is a front view of the grounding element of FIG. 2; 
     FIG. 4 is a partial perspective view of the high frequency board-to-board connector of FIG. 1; 
     FIG. 5 is a plan view of a printed circuit board on which the high frequency board-to-board connector of FIG. 1 is mounted onto; 
     FIG. 6 is a plan view of a design for interconnecting with the high frequency board-to-board connector of FIG. 1; 
     FIG. 7 is a reverse plan view of the design of FIG. 6; 
     FIG. 8 is a plan view of the high frequency board-to-board connector of FIG. 1; 
     FIG. 9 is a partial side sectional view of the high frequency board-to-board connector of FIG. 1; 
     FIG. 10 is a partial side sectional view of the high frequency board-to-board connector of FIG. 1 mounted to the design of FIG. 6; 
     FIG. 11 is a plan view of the high frequency board-to-board connector of FIG. 1 with two transverse rows of conductive pins; 
     FIG. 12 is a partial side sectional view of the high frequency board-to-board connector of FIG. 1 with two transverse rows of conductive pins; 
     FIG. 13 is a plan view of a design for interconnecting with the high frequency board-to-board connector of FIG. 1 with two transverse rows of receptacles; 
     FIG. 14 is a plan view of the high frequency board-to-board connector of FIG. 1 with one conductive pin and a cube shape; 
     FIG. 15 is a plan view of the high frequency board-to-board connector of FIG. 1 with one conductive pin and a cylindrical shape; and 
     FIG. 16 is a plan view of the high frequency board-to-board connector of FIG. 1 with an array of insulative housing arranged in transverse rows and columns. 
    
    
     DETAILED DESCRIPTION 
     A high frequency board-to-board connector for interconnecting printed circuit boards is described hereinafter for addressing the foregoing problems. 
     A first embodiment of the invention, a high frequency board-to-board connector  20  for connecting to a design  22  (as shown in FIG. 6) is described with reference to FIG. 1, which shows a front view of the high frequency board-to-board connector  20  with a partial sectional view of an insulative housing  24 , and FIG. 2, which shows a reverse view of the high frequency board-to-board connector of FIG. 1, with a grounding element  26  exposed. The design  22  includes a matrix of electrical tracks found on a conventional printed circuit board (PCB). The high frequency board-to-board connector  20  comprises of three main elements: the insulative housing  24 , the grounding element  26  and a transverse row of conductive pins  34  as shown in FIG.  3 . 
     Referring to FIGS. 1 and 2, the insulative housing  24  has a design-mounting face  28 , a board-mounting face  30  generally parallel to the design-mounting face  28  and a periphery  32  being perpendicular to and constituting the circumference of the design-mounting face  28  and the board mounting face  30 . The board-mounting face  30  is shown in FIG.  4 . 
     The transverse row of conductive pins  34  is received in the insulative housing  24 . The transverse row of conductive pins  34  protrudes from the design-mounting face  28  of the insulative housing  24  with each conductive pin  34  being generally perpendicular to the design-mounting face  28 . The conductive pins  34  are spaced apart. Each conductive pin  34  has a tail  36  for connecting to a corresponding conductive pad  38  on a printed circuit board (PCB) or the like electronic sub-assemblies shown in FIG. 5 which shows a plan view of a printed circuit board. The tail  36  is connectable to the corresponding conductive pad  38  by one of surface mount technology (SMT) or through-hole mounting. 
     FIG. 6 shows a plan view of the design  22  which includes a transverse row of receptacles  40  corresponding in quantity and positional arrangement to the row of conductive pins  34 . FIG. 7 shows a reverse plan view of the design of FIG.  6 . Each receptacle  40  is preferably a through-hole via, shaped and dimensioned for receiving the corresponding conductive pin  34  inserted therethrough. Referring to FIGS. 6 and 7, each conductive pin  34  comprises a pair of leads  42  terminating with a free end  44  of the conductive pin  34 . The pair of leads  42  is circum-resiliant along a portion of the conductive pin  34  proximal to the free end  44 . The outer side of each lead  42  includes a bump  45 . The bump  45  facilitates contact with the receptacle  40  when the conductive pin  34  is received into the receptacle  40 . The conductive pin  34  and receptacle  40  described above are conventional connecting pins that include but are not limited to those utilised in encirclement compression (ECOM) connectors. Each conductive pin  34  is preferably tapered at the free end  44  for facilitating insertion of the conductive pin  34  into a corresponding receptacle  40 . 
     FIG. 8 shows a plan view of the high frequency board-to-board connector  20  and FIG. 9 shows a partial side sectional view of the high frequency board-to-board connector  20 . The grounding element  26  as shown in FIG.  8  and FIG. 9, is generally planar and being coupled to the insulative housing  24  by slotting thereinto. The grounding element  26  includes a grounding body  46  and an array of follower arms  48  extending from the grounding body  46  as shown in FIG.  2 . The grounding element  26  further includes a plurality of tails  50  for connecting with corresponding grounding pads  52  on the PCB by way of either surface mount technology or through-hole mounting process. Alternatively, each tail  50  is shaped as a follower arm (not shown) and adapted for connecting with the corresponding grounding pads  52  on the PCB by abutting thereto (also not shown). Each follower arm  48  is resiliently biased and bendable. The bending motion of one follower arm  48  is decoupled from and independent of the bending motion of another follower arm  48 . The follower arm  48  is for connecting to a ground plane  54  in the design  22  of FIG. 6 as shown in FIG.  10 . In situations when either the design  22  is oblique relative to the design-mounting face  28  of the insulative housing or the design  22  has an undulating surface, the decoupled motion of each follower arm  48  adapts to these situations to facilitate contact between the array of follower arms  48  and the ground plane  54 . When the high frequency board-to-board connector  20  is displaced along an engagement axis (not shown) relative to the design  22  for engaging and thereby connecting each of the conductive pins  34  with the corresponding receptacle  40 , the follower arms  48  deflect along the engagement axis for structurally adapting to the ground plane  54  in the design  22 . 
     The follower arm  48  has a base end  56  and a free end  58  as shown in FIG.  2 . The base end  56  of the follower arm  48  provides an interface between the follower arm  48  and the grounding body  46  of the grounding element  26 . The follower arm  48  is generally elongated and extends away from the grounding body  46  at the base end  56  initially and overhanging as a cantilever generally transverse to the grounding body  46  subsequently for facilitating bending thereof when a force is applied to the free end  58 . A ridge  60  having a round shape protrudes from the free end  58  for contacting with the ground plane  54 . The grounding element  26  further includes a notch  62  formed adjacent to the base end  56  and free end  58 . The notch  62  is preferably a concavity for reducing stress concentration at the interface when the follower arm  48  is being bent. The notch  62  not only improves the follower arm  48  travel, but also extends the life span of the follower arm  48  by substantially reducing the risk of the follower arm  48  breaking from the grounding body  46  due to stress concentration at the base end  56 . An abutment  70  is formed adjacent to the notch  62  as shown in FIG.  3 . The abutment  70  provides a mechanical limit for preventing the follower arm  48  from over-bending and consequently from being damaged. 
     Referring to FIG. 1, FIG.  2  and FIG. 8, the grounding element  26  is secured to the periphery  32  of the insulative housing  24  parallel to a plane formed by the transverse row of conductive pins  34  by encapsulating a portion of the grounding element  26  within the insulative housing  24  during plastic moulding of the insulative housing  24 . A pair of holes  64  disposed at distal ends of the insulative housing  24  and grounding element  26  allows for a more secured retention of the grounding element  26  by the insulative housing  24 . Alternatively, other forms of fastening means, for example bolts and nuts, can be employed. 
     The grounding element  26  further includes a pair of catches  66  extending perpendicularly from the grounding body  46  of the grounding element  26  as shown in FIG.  2 . The pair of catches  66  is for insertion into a pair of corresponding apertures  68  constituting a portion in the design  22  which are also vias as shown in FIG.  6 . 
     When inserted in the pair of apertures  68 , the pair of catches  66  aligns the conductive pins  34  and follower arms  48  respectively to the receptacles  40  and the ground plane  54 , consequentially securing the high frequency board-to-board connector  20  to the design  22  in the process. The grounding element  26  and the ground plane  54  align to form a ground path (not shown). Controlling the distance between the ground path and the conductive pins  34  permits impedance matching of preferably up to 50 ohms. The ground path reduces electromagnetic coupling between any pair of conductive pins  34  and consequentially lowering cross-talk noise. Inductive attenuation of the conductive pins  34  is also reduced, further facilitating high frequency operations. 
     A second embodiment of the invention, a high frequency board-to-board connector  20  as seen in FIG. 1, FIG. 2, FIGS. 8 to  10  and FIGS. 11 to  13 , comprises of three main elements: an insulative housing  24 , a grounding element  26  and at least a conductive pin  34 . The descriptions in relation to the structural configurations of and positional relationships among the design  22 , conductive pins  34 , receptacles  40  and follower arm  48  with reference to FIGS. 1 to  10  are incorporated herein. 
     FIG. 11 shows a plan view of the high frequency board-to-board connector  20  comprising a pair of insulative housings  24 . FIG. 12 shows the plan view of the high frequency board-to-board connector  20  of FIG.  11 . Referring to FIG.  11  and FIG. 12, it is shown that one insulative housing  24  is mounted to each of two faces of the grounding element  26 . The transverse row of conductive pins  34  received in one insulative housing  24  is parallel to and aligned with the transverse row of conductive pins  34  received in the other insulative housing  24  with the grounding element  26  forming an interface between both insulative housings  24 . The two rows of conductive pins  34  are for connecting with two corresponding rows of receptacles  40  in the design  22  shown in FIG.  13 . The ground plane  54  extends between the two transverse rows of receptacles  40  for connecting with the follower arms  48  of the grounding element  26 . 
     A third embodiment of the invention, a high frequency board-to-board connector  20  as seen in FIG. 1, FIG. 2, FIGS. 8 to  10  and FIG. 14, comprises of three main elements: an insulative housing  24 , a grounding element  26  and at least a conductive pin  34 . The descriptions in relation to the structural configurations of and positional relationships among the design  22 , conductive pins  34 , receptacles  40  and follower arm  48  with reference to FIGS. 1 to  10  are incorporated herein. 
     FIG. 14, shows a plan view of the high frequency board-to-board connector  200  with a single conductive pin  340  and a cube-shaped insulative housing  240 , and FIG. 15, shows a plan view of the high frequency board-to-board connector  2000  with a single conductive pin  340  and a cylindrical insulative housing  2400 . Referring to FIG. 14, one conductive pin  340  is received in the insulative housing [ 24 ]  240  which has a cube shape. The grounding element  260  is planar and is further shaped and dimensioned for mounting along a portion of the periphery  320  of the insulative housing  240  for generally inclosing the insulative housing  24 . The design-mounting face and the board-mounting face (all not shown) are exposed to allow access to the conductive pins  340  and the corresponding tails (not shown). The grounding element  260  of FIG. 14 includes the follower arms  48  of FIG.  1 . The follower arms are not shown in FIG.  14 . 
     Alternatively, the insulative housing  2400  is generally cylindrical with the design-mounting face and the board-mounting face (all not shown) constituting two distal ends of the cylindrical insulative housing  2400  as shown in FIG.  15 . The grounding element  2600  of FIG. 15 extends along the periphery  3200  of the insulative housing  2400  and includes the follower arms  48  of FIG.  1 . The follower arms are not shown in FIG.  15 . 
     A fourth embodiment of the invention, a high frequency board-to-board connector  20  as seen in FIG. 1, FIG. 2, FIGS. 7 to  9  and FIG. 16, comprises of three main elements: an insulative housing  24 , a grounding element  26  and at least a conductive pin  34 . The descriptions in relation to the structural configurations of and positional relationships among the design  22 , conductive pins  34 , receptacles  40  and follower arm  48  with reference to FIGS. 1 to  10  are incorporated herein. 
     FIG. 16, shows a plan view of the high frequency board-to-board connector  2005  comprising an array of insulative housings  2405 . Referring to FIG. 16, it is shown that the insulative housings  2405  are arranged into transverse rows and columns. The grounding element  2605  forms an interface between any pair of insulative housing  2405 . One conductive pin  3405  is received in each insulative housing  2405 . The grounding element  2605  of FIG. 16 extends along the periphery  3205  of the insulative housing  2405  and includes the follower arms  48  of FIG.  1 . The follower arms  48  are not shown in FIG.  16 . 
     In the foregoing manner, a high frequency board-to-board connector is described according to four embodiments of the invention for addressing the foregoing disadvantages of conventional high frequency board-to-board connectors. Although only four embodiments of the invention are disclosed, it will be apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of the invention.