Abstract:
Opto-electric on-board including opto-electronic elements on a substrate and an optical coupling, device for transferring optical signals between the opto-electronic elements and a complementary optical cable connector. The optical coupling device includes a prism with a contact face and a lower face and two or more supports spacing each the lower face from the oppositely arranged opto-electronic elements. Each support includes one or more feet attached to the substrate.

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Stage of and claims priority to and the benefit of International Patent Application No. PCT/IB2012/002649, entitled “BOARD CONNECTOR” filed on Oct. 29, 2012, which is herein incorporated by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The invention relates to a board connector for connecting a complementary second connector, such as an optical cable connector, to a substrate, such as a printed circuit board. The connector comprises one or more elements mounted on the printed circuit board, such as an optical coupling device for receiving light signals to be guided to a transducer on the substrate. 
     BACKGROUND OF THE DISCLOSURE 
     When the complementary second connector is brought into engagement with the board connector, the internals of the board connector can be dislocated. Small changes of the position of internal elements involved in signal transfer, can result in substantial loss of signal integrity. These internals can for instances be mounted to the board by means of an adhesive. This results in shear stresses in the adhesive. 
     This problem particularly occurs with optical cable connectors, which must be pressed against a light receiving element in order to achieve accurate positioning and reliable fixation. 
     It is an object of the present invention to provide a more reliable way of fixating the positions of board connector elements in a reliable and stable manner. 
     SUMMARY OF THE DISCLOSURE 
     An opto-electric on-board connector is disclosed comprising:
         opto-electronic elements, such as VCEL&#39;s and/or pin-diodes and associated drivers and circuitry;
           an optical coupling device for guiding optical signals between the opto-electronic elements on a substrate, such as a transceiver board, and a complementary optical cable connector
               wherein the optical coupling device comprises a prism with a contact face and a lower face;   wherein the optical coupling device further comprises two or more supports spacing each the lower face from the oppositely arranged opto-electronic elements;   wherein each support comprises one or more feet attached to the substrate.   
               
               

     The supports accurately space the lower face at a desired distance of the opto-electronic elements. The feet enable a firm and reliable attachment to the substrate, also during mating or unmating of a complementary connector. 
     In use, each lens of the first array faces a terminal end of an associated optical fiber of the complementary optical cable connector. 
     The opto-electronic elements can for instance be positioned on a bottom surface of the transceiver, such as an inner connector board or substrate. 
     Each support can for example comprise two oppositely extending feed to define an H-shape of the optical coupling device in plan view. Such feet can be used to balance forces exerted by pushing a complementary connector against the optical coupling device. 
     The connector will typically comprise a housing encasing the optical coupling device and the opto-electronic elements. To improve heat dissipation, the housing may be made of an thermoconductive material. 
     The opto-electronic elements can for example include VCEL&#39;s VCEL&#39;s (Vertical-cavity surface-emitting lasers), which can receive and emit light signals, and/or PIN photo-diodes which can only receive light signals from the oppositely arranged array of lenses of the optical coupling device. VCEL&#39;s and PIN diodes are controlled by drivers, which generate heat. If the drivers are positioned between the feet of the optical coupling device supports, the drivers are at short distance of the associated opto-electronic elements while the generated heat can be dissipated effectively. 
     Heat dissipation can be further optimized if the housing comprises an interior surface profiled to provide a tight contact with the upper surfaces of the drivers, in such a way that there are no substantial in gaps left. Air gaps substantially reduce heat dissipation. In order to avoid the presence of air gaps, thermally conductive gap filling material can be applied between the drivers and the interior housing surface. Suitable gap filling materials are for example Tpli® and Tflex® of Laird Technologies. 
     The support and the feet of the optical coupling device can for example be bonded to the substrate by an adhesive, such as UV-curable or thermally curable adhesives, e.g., a UV-curable or thermally curable epoxy adhesive or mixtures thereof. 
     In a specific embodiment, the prism of the optical coupling device, may comprise a light-reflective back face under an angle to guide optical signals from each lens of the first array of the contact face to an associated lens of the second array at the prisms lower surface. 
     To align the optical coupling device and a complementary cable connector, the optical coupling device can for example comprise alignment features, such as alignment pin, flanking the first array of lenses, the alignment features matching with corresponding alignment features of a complementary cable connector. The alignment features of the optical coupling device may for instance include parallel alignment pins extending in a direction under right angles with the contact face. 
     Optionally, the supports have side faces profiled to cooperate with latches of a complementary cable connector. 
     In an specific embodiment, the supports of the optical coupling device can be provided with flat top faces to enable using vacuum nozzle pick and place systems for positioning the optical coupling device during the assembling process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be further explained under reference to the accompanying drawings. 
         FIG. 1A : shows an exemplary embodiment of a connector with a complementary second connector; 
         FIG. 1B : shows the two connectors of  FIG. 1A  in an assembled state; 
         FIG. 2A : shows the second connector of  FIG. 1  in exploded view; 
         FIG. 2B : shows in perspective cross section a cable connection of the connector of  FIG. 2A ; 
         FIG. 3A : shows in perspective view the internal configuration with an optical coupling device member of the connector of  FIG. 1 ; 
         FIG. 3B : shows the configuration of  FIG. 3A  in exploded view; 
         FIG. 3C : shows in detail a mounting section of the optical coupling device member of  FIG. 3A ; 
         FIG. 4A : shows a detail of the optical coupling device member of  FIG. 3A ; 
         FIG. 4B : shows in perspective rear view the optical coupling device member of  FIG. 3A ; 
         FIG. 4C : shows the optical coupling device member of  FIG. 3A  in top view; 
         FIG. 4D : shows the optical coupling device member of  FIG. 3A  in bottom view; 
         FIG. 5A : shows the second connector in front view; 
         FIG. 5B : shows the second connector in front view during connection with the first connector; 
         FIG. 6A : shows in cross section the connector and the complementary connector of  FIG. 1  just before being mated; 
         FIG. 6B : shows the connector and the complementary connector of  FIG. 1  just after being mated in cross section along a vertical plane; 
         FIG. 7A : shows the two connectors in a cross section along a horizontal plane during mating; 
         FIG. 7B : shows the two connectors in a cross section along a horizontal plane after being mated; 
         FIG. 8A : shows the two connectors in a cross section along a horizontal plane during disconnection; 
         FIG. 8B : shows the two connectors in a cross section along a horizontal plane after being disconnected; 
         FIG. 9A : shows an alternative embodiment of an optical coupling device; 
         FIG. 9B : shows an alternative embodiment of an optical coupling device; 
         FIG. 9C : shows an alternative embodiment of an optical coupling device. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIGS. 1A and 1B  show an exemplary embodiment of a connector assembly  1  of a board connector  2  and a complementary optical cable connector  3 . In  FIG. 1A , the optical cable connector  3  is moved in a mating direction A to be connected to the board connector  2 , as shown in  FIG. 1B . 
     The optical connector  3  comprises a plug  4  at the end of an optical cable (not shown). The plug  4  is shown in exploded view in  FIG. 2A  and comprises a rectangular cable bent relief  7  of a rubber-like material holding the end of the optical cable to protect the fibers from overstressing by bending. The cable holder  7  is partly inserted into a matching rectangular opening  8  in a ferrule  9 . The rectangular opening  8  is flanked by two cylindrical openings  11 , each holding one end of a compression spring  12 . Openings  13  of a smaller diameter extend coaxially from the cylindrical openings  11  to the opposite end  14  of the ferrule  9 . This end exposes the terminal ends of the optical fibers  15  (see  FIG. 5B ). A shoulder  16  is formed between the larger openings  11  and the smaller openings  13 . The compression springs  12  abut the shoulder  16 . 
     The ferrule  9  has a central opening  17  filled with a cured adhesive fixating the fiber ends within the ferrule  9 . 
     The ferrule  9  is capped by release member  20 . The release member  20  is a single piece, e.g., of a resilient elastomeric material, and comprises a shutter  21  hiding the end  14  of the ferrule  9 . As shown in  FIGS. 5 a    and  5 B, the shutter  21  is formed by an upper blade  22  and a lower blade  23  which can be separated to expose the optical fibers  15  when the cable connector  3  is connected to the board connector  2 . The upper and lower blades  22 ,  23  face each other with edges provided with spacers  24  creating a split  25 . 
     The release member  20  further comprises a U-shaped resilient bridge  26  at lateral both sides of the ferrule  9 . The U-shaped bridges  26  bias the blades  22 ,  23  towards each other. In this position the shutter  21  closes off the terminal ends of the optical fibers  15 , protecting the fiber ends against moisture, dirt and mechanical impact. 
     An upper web  27  of the release member  20  covers the top side of the ferrule  9 . Similarly, a lower web  28  is provided below the lower side of the ferrule  9 . One end of the upper web  27  is resiliently connected to the upper ends of the two U-shaped bridges  26  and the upper blade  22  by means of two mirrored C-shaped resilient members  29  symmetrically arranged back-to-back in a mirrored manner. Similarly, one end of the lower web  28  is resiliently connected to the lower ends of the two U-shaped bridges  26  and the lower blade  23  by means of two similarly mirrored C-shaped resilient members  31 . 
     At the cable side of the plug  4  the upper web  27  of the release member  20  is connected to a pull tab  32 , which can be pulled by a user to disconnect the cable connector  3 , as will be explained hereinafter. 
     The cable connector  3  further comprises a locking device  36  (see  FIG. 1A ) with a box-shaped main body  37  having an open side  38  receiving the ferrule  9  and a closed side  39  with a cable passage  41 . An upper face  42  of the main body  37  covers the upper web  27  of the release member  20 , while a lower face  43  of the main body  37  covers the lower web  28  of the release member  20 . 
     The locking device  36  has two symmetrically arranged mirrored latches  44  extending from the main body  37  pointing into the mating direction A. The latches  44  cover the side faces of the ferrule  9  and the U-shaped bridges  26  of the release member  20 . 
     The front end  19  of the ferrule  9  is somewhat broader. The open side  38  of the main body  37  is bordered with a collar  45  for enclosing the broadened front end  19  of the ferrule  9  to limit the sliding movement of the ferrule relative to the release member (see  FIG. 8A ). 
     The latches  44  have a free end provided with a cam  46 . The two cams  46  point to each other and project in mating direction A over a distance from the shutter  21 . The upper and lower webs  27 ,  28  of the release member  20  are provided with ridges  40  creating a labyrinth between the shutter and the locking device  36  to protect the internals, in particular the optical coupling device  71  from dust. Internally, the compression springs  12  are compressed between the shoulder  16  and the inner surface of the main body  37  of the locking device  36 . 
     The upper and lower webs  27 ,  28  of the release member  20  are both provided with a central projection  47  moveable in the mating direction A in a slit  48  at the topside and a bottom side of the main body  37 , respectively (see  FIGS. 8A and 8B ). 
     The locking device  36  is formed by two identical angled parts  51 , both having a short side  52  forming the lateral sides of the locking device  36 , and a long side  53 , forming the top and bottom sides of the locking device  36 . The short and long sides  52 ,  53  of the parts  51  are under right angles. The latches  44  extend from the short sides. The short side  52  has one side edge connected to an end of longer side  53 , while the opposite side edge comprises two parallel studs  54 , which can be snapped into matching openings  56  in the longer side  53  of the other angled part  51  to form the assembled locking device  36 . The two parts  51  are held together by an elastic band  57 . 
     The exemplary embodiment of the board connector  2  as shown in the drawings is a transceiver with a top cover  61  with four corners bolted onto a rectangular lower housing section  62  holding an internal transceiver board  63  carrying the opto-electronic elements  91  and the feet  72  of the optical coupling device  71  (see  FIG. 3A ). The board connector  2  is mounted into a socket  65  mounted on a substrate  70 , such as a printed circuit board (see  FIG. 1A ). The top cover  61  comprises a casing  64  with one side having a receiving opening  66  for receiving the cable connector  3 . The top side  67  of the casing  64  slants downwardly from the side with the receiving opening  66  to the opposite side of the casing  64 . A locking ring  68  with two opposite pinching grips  69  is put over the casing  64  to lock the board connector  2  in the socket  65 . 
     The internals of the board connector  2  are shown in  FIGS. 3 a    and  3 B. An optical coupling device or optical coupling device  71  is positioned on the substrate  63  to face the optical fibers  15  of the optical connector  3  when it is received in the board connector  2 . The optical coupling device  71  comprises two feet  72 . Both feet  72  have two openings  73  filled with a cured adhesive  74  embedding an anchoring element  76  mounted on an internal connector substrate  63  (see  FIG. 3C ). Forces exerted to the optical coupling device  71  when the connectors  2 ,  3  are connected or disconnected, are absorbed as compression stresses and bending stresses by the anchoring elements besides internal shear stresses in the adhesive and peel stresses between the adhesive and the substrate. This way, the anchoring elements  76  contribute to a more reliable fixation of the optical coupling device member  71 . In the embodiment shown in  FIG. 3C , the anchoring element  76  is a capacitor  77  mounted on the board by two capacitor feet  78 . 
     Between the feet  72  the optical coupling device member  71  carries two rectangular columns  79  sandwiching a prism  81 . The prism  81  has a flat front face  82  with an array of lenses  83  facing the respective optical fiber ends  16  of the cable connector  3  when the connectors  2 ,  3  are connected. The array of lenses  83  is flanked by two symmetrically arranged parallel pegs  84  extending from the columns  79 . The pegs  84  serve to open the shutter  21  of the optical cable connector  3  when the optical cable connector  3  is connected to the board connector  2 . 
     The back side of the prism  81  (see  FIG. 4B ) has a vertical lower part  86  and a light reflective upper part  87  which slants under an angle to deflect light entering the prism  81  via the lenses  83  downwardly to the bottom  88 , where the light leaves the optical coupling device  71  via a second array of lenses  89  (see  FIG. 4D ). Each lens  83  of the first array transfers light signals to a single lens  89  of the second array. The light is then received by an opto-electronic element  91 , such as a VCEL or a PIN photo diode, located on the substrate  63  below the bottom side of the prism  81  (see  FIG. 3A ). The opto-electronic element  91  translates the light signals into electronic signals to be transferred via circuitry (not shown) printed on the substrate  63 . 
     The tops  80  of the columns are configured as flat, substantially horizontal surfaces and are suitable for use with automated vacuum nozzles pick and place systems. 
     At the side of the feet  72  both columns  79  have a vertical ridge  94  (see  FIGS. 4C and 7A ) for cooperation with the latches  44  of the locking device  36  when the optical connector  3  is connected to the board connector  2 , as will be explained hereinafter. 
       FIG. 6A  shows in cross section the cable connector  3  approaching the board connector  2  just before being connected. The receiving opening  66  of the top cover  61  is closed by a flap  100  connected to the lower edge of the receiving opening  66  by means of a hinge  101 , allowing movement of the flap  100  between a first position closing off the receiving opening  66 , as shown in  FIG. 6A , and a second position, where the flap  100  is folded backwards towards the optical coupling device  71 . A torsion spring  110  biases the flap  100  to the closing position, where it abuts a stop  102  at the edge of the receiving opening  66 . 
     The VCEL&#39;s or photo PIN diodes  91  comprise drivers  105  generating heat. The interior of the top cover  61  is profiled to tightly contact the top surfaces of the drivers  105  in such a way that no air gap remains between the top cover  61  and these respective surfaces. This enables effective dissipation via the top cover  61 . The top cover  61  comprises an inwardly protruding vertical brim  111  fitting against the back face of the optical coupling device and covering the drivers  105 . Air gaps and inclusions can be avoided by applying an air gap filler material between the drivers and the inner surface of the top cover. 
     When the cable connector  3  is inserted into the receiving opening  66  of the board connector  2 , the flap  100  is folded down and the plug  4  is pushed towards the optical coupling device  71  until the shutter  21  hits the pegs  84 . The pegs  84  are cylindrical with flattened upper and lower sides (see  FIG. 4A ) dimensioned to wedge the split  25  between the upper and lower blades  22 ,  23  of the shutter. As a result the upper and lower blades  22 ,  23  are forced apart against the action of the resilient U-shaped bridges  26  of the release member  20 . In this position, the fiber ends  15  are exposed (see  FIG. 5B ). Pushing the plug  4  further into the board connector  3  will insert the pegs  84  into the smaller diameter opening  13  in the ferrule  9  (see also  FIG. 7A ). The pegs  84  are dimensioned to snugly fit within the openings  13  to enable very accurate positioning of the fiber ends  15  relative to the lenses  83  of the optical coupling device  71  (see  FIG. 7A ). 
     The mating process is shown from above in  FIGS. 7 a    and  7 B. During positioning respective contact faces  103  of the cams  46  of the latches  44  encounter parallel contact faces  114  the vertical lateral ridges  94  of the optical coupling device  71 . Meanwhile, the outer end of the ferrule  9  encounters spacers  106  of the optical coupling device  71  right next to the pegs  84 . The spacers  106  are dimensioned to space the fiber ends  15  very accurately at a desired distance from the lenses  83  of the optical coupling device  71 , forming a gap  107  of uniform width. Although the ferrule  9  is stopped by the spacers  106 , the locking device  36  can be pushed further inwardly against the action of the compression springs  12  until the cams  46  of the latches  44  hook behind the ridges  94 , preventing unintentional disconnection of the connectors  2 ,  3 . In this position, the compression springs  12  exert a continuous pressure pressing the plug  4  against the optical coupling device  71 , fixating the fibers ends  15  relative to the lenses  83 , which contributes to the overall reliability of the connector system. 
     The connectors  2 ,  3  can be disconnected by pulling the pull tab  32 . In the locked position the contact end of the connector  2  is fit between the inner surfaces of the board connector  3  in such way that the shutter blades cannot be moved apart by pulling the pull tab  32 . The mirrored pair of C-shaped resilient members  29 ,  31  is stretched, while the locking device  36  and the ferrule  9  stay in place. The latches  44  have a slanting base  108  forming a contact face of a pushing section  109  of the release member  20 . The pushing section  109  is positioned at a point where the C-shaped resilient member  29 ,  31  is linked to the upper web  27 , or to the lower web  28  respectively. The pushing section  109  projects over a lateral distance from the upper and lower webs  27 ,  28 . The pushing section  109  presses against the contact face  108  of the latches  44 . As a result, the latches  44  are pushed aside and eventually unhooked from the ridges  94 . The compression springs  12  and the C-shaped resilient members  29 ,  31  are now allowed to relax. The locking device  36  is pushed backwardly by the springs  12 . This contributes to easier removal of the cable connector  3 . 
     Alternative embodiments of the optical coupling device are shown in  FIGS. 9A-C . These embodiments have feet extending at only one side of the respective support. In  FIG. 9A  the coupling device  120  comprises oppositely extending feet. In  FIGS. 9B and 9C  the feet extend in the direction of the contact face ( FIG. 9C ) and in the opposite direction ( FIG. 9B ), respectively.