Patent Publication Number: US-2012040546-A1

Title: Very High Frequency Electrical Connector

Description:
The invention concerns an electrical connector for electric cables operating at very high frequencies, for example from 30 to 300 GigaHertz (GHz). The invention can be applied to the connector technology field, and can also be applied in other fields. 
     Such an electrical connector, which permits connecting a complementary connection device to an electrical cable, usually has an insulating frame forming a box, a board coated with a printed circuit (or PCB board), and first electrical contacts. The printed circuit has electrically conductive tracks, a first end of which is connected to a corresponding first electrical contact and the other end is connected to a corresponding electrical wire. 
     In order to compensate for the electrical impedance of the cable, which impedance is, among other things, a function of the cable length, the addition of passive electronic components (resistor, capacitor, etc.) to the PCB board is known. However, depending on the length of the cable and due to the very high frequencies, it may be necessary to add a large number of these components. The increase in the number of these components can lead to excess space requirements of the box that can disrupt the connections between each of the first contacts and each of the corresponding printed tracks, among other things. Therefore, it may become difficult to obtain an optimal electronic data transmission for electrical connectors of very high frequencies. 
     One object of the invention is to propose a connector for electrical cables whose manufacturing cost is reduced, whose dimensions are compact and that can also assure an optimal high-frequency electronic data transmission. 
     For this purpose, an electrical connector according to claim  1  is provided. 
     In fact, the electrical connector is obtained at least by means of molding a plastic in order to form a box, which is then partially metal-coated to form the conductive tracks. The box thus molded, forms a single support unit holding the board and the frame. 
     Creating such an electrical connector does not require assembling a printed circuit board onto a frame, which permits reducing not only manufacturing costs, but also the dimensions of the box without harming the electronic data transmission. 
     The box is made in such a way that it has at least one cavity to receive the first electrical contacts capable of receiving the second electrical contacts of a complementary connection device, at a site near the front face of the connector. 
     According to a variant, the first electrical contacts are inserted in the molded box. In an advantageous manner, these first contacts are formed from a metal plate and have an extension designed to be connected to a conductive track, for example, by soldering. 
     According to another variant, the first electrical contacts can be made by molding a plastic in order to form at least one elastic “blade”. This blade can be made an integral part of the box or can even be glued or embedded in the box. This blade is partially metal-coated so as to electrically connect a second electrical contact to the corresponding track. 
     The box can also comprise at least one means of positioning the electrical wire in order to assure its alignment relative to the plane formed by the bottom of the box. These positioning means can be a groove or an anvil-shaped piece. This groove and this anvil piece are made in such a way that they have a shape that is partially adapted to that of the electrical wire. Thus this groove and this anvil piece advantageously permit receiving at least one electrical wire while assuring a stable hold of this wire in the box. In an advantageous manner, the surface designed to be in contact with the electrical wire can be at least partially covered with an abrasion product so as to reinforce the holding of the wire in the box. 
     The box can comprise at least one longitudinal channel positioned between at least two electrical wires. This channel is advantageously metal-coated so as to form an electromagnetic screen relative to these two electrical wires. 
     Other variants and embodiments corresponding to the characteristics according to claims  2  to  11  are described hereunder. 
    
    
     
       The invention will be better understood upon reading the description that follows and examining figures that accompany it. These latter are only given by way of indication and do not at all limit the invention. The figures show: 
         FIG. 1 : A perspective view of an electrical connector, according to the invention; 
         FIG. 2 : A view of an electrical connector viewed from the bottom, according to the invention; 
         FIG. 3 : A three-dimensional view of a first electrical contact, according to the invention; 
         FIG. 4 : A schematic diagram of a first electrical contact, according to a variant of the invention; 
         FIGS. 5   a  and  5   b : schematic sectional diagrams of a first electrical contact, according to a variant of the invention; 
         FIGS. 6   a  and  6   b : Schematic diagrams of a protection cover, according to the invention; 
         FIGS. 7   a  and  7   b : Views of at least one anvil-shaped piece for receiving an electrical wire, according to the invention; 
         FIG. 8 : A schematic diagram of a grapple piece according to the invention, 
         FIG. 9 : A schematic diagram of a cross section of a connector at a site near the rear face of the connector, according to the invention; 
         FIG. 10 : A schematic diagram of a cross section of a connector at an area near the rear face of the connector, according to a variant of the invention; 
         FIGS. 11   a  to  11   d : Perspective views of a manufacturing process for an electrical connector, according to the invention; 
     
    
    
       FIG. 1  illustrates an electrical connector  1 , according to the invention; Electrical connector  1  has an insulating box  2 , electrically conductive tracks  7 ,  9 ,  10  and  11  connected to a plurality of deformable first electrical contacts  8 ,  12 ,  13 ,  14 , arranged parallel relative to one another along a lengthwise or elongation axis  15  of the connector. Each of the first electrical contacts is designed to be connected to a corresponding second electrical contact  20 ,  83 ,  84 ,  85 . These second contacts are formed by a complementary connection device  5 . 
     The connector has a front face  3  and a rear face  4 . Front face  3  of the connector, for example, is a face by means of which the second electrical contacts of complementary connection  5  are inserted into connector  1 . Rear face  4  of the connector is a face by means of which electrically conductive wires  6 , formed by an electrical cable (not shown), are inserted into this same connector  1 . In the example of  FIG. 1 , the cable has four electric wires such as  6 ,  91 ,  92 , and  93 . Each of these wires is formed by a strand  65  and a protective sheath  66 . The protective sheath surrounds the strand. The electrical wire assembly can be surrounded by a woven metal piece (not shown) to form the electrical cable. Each of these wires is designed to be connected to a corresponding conductive track. 
     According to the invention, the first electrical contacts are connected to corresponding conductive tracks by joining. Here, “joining” is meant to be a superimposition of the first contact with a corresponding zone of the conductive track to form an electrical connection between the first contact and the track. 
     According to the invention, such a connector  1  is made by means of molding a plastic material in order to form box  2 , which box is partially metal-coated to form electrically-conductive tracks  7 ,  9 ,  10  and  11 . Molding can be done by an MID (Molded Interconnection Device) technique. This MID technique involves at least one plastic molding in order to form case  2 . 
     Molded box  2  has a bottom  16  and a wall  17  at least partially peripheral. This wall  17  extends perpendicularly to a plane formed by bottom  16 . The tracks, for example of copper, are formed on the inner surface  32  of bottom  16  of box  2 . 
     Each of the tracks extends longitudinally along elongation axis  15  of the connector from front face  3  in the direction of rear face  4  of the connector. Each of the tracks has a first termination  40  near the front face  3  and a second termination  41  near the rear face  4 . The first termination and the second termination are connected to one another by an elongated section  42 . Each of these terminations  40  and  41  has a flared shape relative to the elongated central section  42 . This flared shape advantageously permits increasing the contact surface, which facilitates the positioning of the first electrical contacts and the electrical wires on the conductive tracks. 
     The box forms at least one cavity  18  to receive at least one electrical contact  8  at a site near front face  3 . This cavity facilitates the insertion of the first contact into the box and permits assuring a stable positioning of the first contact in the box. In the embodiment described in  FIG. 1 , box  2  has a first cavity  18 , a second cavity  21 , a third cavity  22  and a fourth cavity  23 . Each of these cavities  18 ,  21 ,  22  and  23  receives first contacts  8 ,  12 ,  13  and  14 , respectively. 
     First cavity  18  is separated from second cavity  21  by a first partition  24 . Second cavity  21  is separated from third cavity  22  by a second partition  25 . Third cavity  22  is separated from fourth cavity  23  by a third partition  26 . 
     Partitions  24 ,  25 , and  26  according to  FIG. 1  are made in such a way that they extend perpendicularly relative to the plane formed by bottom  16  of box  2  and partially along the box, from front face  3  in the direction of rear face  4 . These partitions  24 ,  25  and  26  can, of course, extend over the entire length L of the box. Such partitions extending along the entire length can advantageously serve as an insertion guide to facilitate the insertion of the electrical wires into the box. 
     Each of the cavities  18 ,  21 ,  22  and  23 , respectively, has an opening  19 ,  27 ,  28  and  29  formed through wall  17  of front face  3  of the connector. These openings  19 ,  27 ,  28  and  29  each allow the passage of a corresponding second electrical contact. 
       FIG. 2  is a bottom view of the connector in which box  2  has a central channel  30  extending parallelly to elongation axis  15  of the connector. Channel  30  is the result of a deformation of the outer surface of the box in the direction of the inner surface, so that the inner surface projects relative to the plane of bottom  16  of the box. Channel  30  can be communicating, i.e., it communicates by a slot  127  from outer surface  31  towards inner surface  32  of the box. Channel  30  can form a partition as is shown in  FIG. 1 . 
     Outer surface  31  of the box can be at least partially metal-coated so that at least one part of a surface defined by the channel is metal-coated. Such a metal-coated channel thus advantageously permits forming an electromagnetic screen relative to at least two tracks placed on either side of this channel  30 . 
     Bottom  16  of box  2  also has a plurality of communicating holes  33 ,  34 ,  35 ,  36 , such as shown in  FIG. 2 . These communicating holes are distributed two by two on either side of channel  30  along an axis  103  perpendicular to elongation axis  15  of the box. These holes are designed to be at least partially covered by a corresponding first electrical contact. The holes facilitate the positioning of the first contacts in the case. 
     The box comprises attachment means  37 ,  38  ( FIGS. 1 and 2 ). These attachment means  37 ,  38  permit stacking several connectors according to the invention, one below the other. These attachment means can form a depression  37  visible on outer surface  31  of the box and which forms a protuberance  38  visible on inner surface  32  of the box. Thus during the stacking of a first connector on top of a second connector, protuberance  38  of the second connector is engaged in depression  37  of the first connector. 
     Finally, the box is pierced by a central recess  39  ( FIG. 2 ). This central recess  39  is situated at a place close to the rear face  4  of the connector. This recess is communicating and also extends from outer surface  31  to inner surface  32 . 
     Channel  30 , depression  37  as well as recess  39  can be aligned with one another along elongation axis  15  of the connector. 
       FIG. 3  shows one example of embodiment of a first electrical contact  8  according to the invention. First electrical contact  8  of connector  1  can be made from sheet metal by stamping. This sheet metal is cut out to form a clamp comprising a central piece  43  of rectangular shape, a first arm  44 , a second arm  45 , a hook piece  46  and an extension  47 . 
     The two arms  44  and  45  are positioned perpendicularly relative to a plane formed by central piece  43  and are parallel to one another. The two arms  44  and  45  each have an end  48  and  49  converging toward one another without touching. Or, the two arms  44  and  45  may even touch at their ends. More precisely, the two arms  44  and  45  form a clamp designed to receive a second electrical contact. Each of these ends  48  and  49  forms a surface curved in such a way that these rounded curved surfaces are placed facing one another. 
     At the place where ends  48  and  49  join, the two arms define an opening  51  into which the second electrical contact is inserted. During insertion of the second contact into opening  51 , a reversible elastic radial spreading apart of each of arms  44  and  45  is produced relative to the insertion axis at the same time that the second contact comes to be supported against the curved surface of ends  48  and  49 . 
     The hook piece  46  extends from central piece  43  perpendicularly to an axis  50  and in the plane formed by central piece  43 . This hook piece  46  is folded over central piece  43  to form a partially-closed orifice  75 . This hook piece  46  permits elastically receiving an end  52  of second contact  20  while being adapted to the shape of this same end  52 . For example, end  52  of second contact  20  can comprise a constricted circular cylindrical part that is inserted into hook piece  46  by allowing end  76  of second contact  20  to pass. End  76  permits holding the second contact in the box since it can be supported against edges  86  of the hook piece. 
     Extension  47  extends longitudinally from this hook piece  46  relative to axis  50 , from front face  3  in the direction of rear face  4  of connector  1 . The first electrical contact is also made in such a way that one of the two arms is situated in the same plane as that formed by extension  47 . 
     The first electrical contact is positioned in the plane formed by extension  47  parallel to the plane formed by bottom  16  of the box. Extension  47  is positioned on first termination  40  of the track while at least a part of hook piece  46  at least partially covers a corresponding communicating hole of the box. Alternatively, a part of hook piece  46  is inserted partially into the corresponding communicating hole to attach the first contact to the box. The first electrical contact is also positioned with a plane formed by one of the two arms situated in the same plane as the one where extension  47  is formed, supported against the bottom of the box. Extension  47  is positioned on the second termination of the track by joining while being soldered to the track. 
     The hole such as  33 ,  34 ,  35  and  36  previously described facilitates the positioning of the first electrical contact by crimping a sheet metal formed by the first contact in this hole. 
     By way of example, hook piece  46  forms an open tube with a first end  87  and a second end  88  situated facing one another. Each of ends  87  and  88  forms, at a site far from front face  3 , a first and second clutching piece  53 ,  54 . The first contact can also be held by while coming to be partially inserted in hole  33  made in the box, while being slightly bent in this same hole. 
     In a variant of the invention ( FIG. 4 ) at least one plastic elastic blade  55  is molded and then partially metal-coated to form a first electrical contact. The blade according to the variant can be made by the MID technique as previously mentioned. 
     Blade  55  comprises a base  61  and an elongated body  126 . The blade can be inserted in a fixed manner into the box by embedding the base in wall  17  of the box. 
     Alternatively, the box can also be molded so as to form the blade connected to a single support at wall  17 . 
     Blade  55  is partially coated with a metal strip  80  that has the function of electrically connecting a second contact to the corresponding track ( FIG. 5   b ). This metal strip  80  is shown by the shading of  FIG. 4 . 
       FIGS. 5   a  and  5   b  are plan views of an electrical connector according to the invention before and after insertion of second contacts. In this example, the connector comprises a first elastic blade  55 , a second elastic blade  94  and a third elastic blade  95 . Each of these blades is designed to electrically connect a corresponding second contact  56 ,  60 ,  79 . The three blades define four compartments  58 ,  59 ,  96  and  97 . Each of the compartments respectively communicates by an opening  63 ,  64 ,  98 ,  99  that permits the passage of the corresponding second contact into the box. The opening is made passing through edge  61 . When a second contact is inserted into the box through the opening, it is found held between two adjacent blades. Second contact  60  is supported against metal-coated part  121  of a first blade on one side, and against the non-metal-coated part  124  of a second adjacent blade on the other side. It should be noted that for the second contact  56  situated at the end, the non-metal-coated part is made up by wall  17  of box  2 . 
     Such an embodiment of the metal-coated blade advantageously permits preventing the second contacts from short-circuiting each other. 
     Each blade has a bent surface  62  tending to partially obstruct a portion of compartment  58 ,  59 ,  96 , on the inside of which the second contact  56 ,  60 ,  79  is inserted. 
     The blade can advantageously be metal-coated at the level of curve  62 . By being in contact with curve  62 , the second contact is supported elastically against the blade, which assures a continuous and reliable contact of the second contact. 
     The insertion of the second contacts into constricted compartment  58 ,  59 ,  96  beyond curve  62  leads to a radial separation of the blade relative to insertion axis  50  of the second contact. This radial separation is obtained by sliding the blade along bottom  16  of the box in order to allow the passage of the second contact into the compartment. 
     It can notably be provided that when the blade is separated relative to the axis of insertion of the second contact, the blade is at least temporarily in contact with printed track  7 ,  40 . In particular, it can be provided that the blade is in contact with the printed track by its metal strip  80  when it is or is not in contact with the second contact. 
     Each of the blades is ribbed in such a way that at an area of the compartment where curve  62  is situated, a width  100  of the compartment defined between two blades positioned next to one another is less than the thickness  101  of the second contact ( FIGS. 5   a  and  5   b ). Each of the blades is made in such a way that during the insertion of the second contact into the box, the blade is separated elastically and radially relative to insertion axis  50  and defines another width  102  corresponding to the thickness  101  of the second contact so as to assure that the contact is held in the box. 
     The electrical wires designed to be inserted into the connector are each formed by an electric strand  65  and a protection sheath  66 , the sheath surrounding the strand ( FIG. 1 ). Electric wire  6  is inserted into box  2  through rear face  4  by means of stripped strand  65  which is placed in contact with the corresponding electrically conductive track. In an example,  FIG. 1 , a first electric wire  6 , a second electric wire  91 , a third electric wire  92  and a fourth electric wire  93  are placed in direct contact with first track  7 , second track  9 , third track  10  and fourth track  11 . Each of the stripped strands is soldered to second termination  41  of the corresponding track. The woven metal piece of the cable can be grounded at a metal-coated area near recess  39 . 
     The electrical wire is inserted into the box by rear face  4  parallel to bottom  16  of case  2 . In order to do this, the box comprises at least one metal anvil piece  69  ( FIGS. 7   a  and  7   b ) positioned in contact with a corresponding track. The anvil piece has a shape partially adapted to this stripped strand of the electric wire. For this purpose, the anvil piece has a height H corresponding to the thickness E of sheath  66 . Height H and thickness E are measured along an axis  82  perpendicular to the plane of bottom  16 . 
     In another variant of the invention, the box comprises at least one groove  72  at an area of the box near rear face  4  ( FIG. 10 ). In order to form this groove, the box has a hole of a height h corresponding to thickness E of sheath  66  ( FIGS. 1 and 10 ) measured along axis  82  and which extends along elongation axis  15 . The stripped strand is then placed in contact with the track coming out from the groove parallel to the plane of bottom  16 . 
     In another variant of the invention, the connector can comprise at least one grapple piece  70  ( FIG. 8 ). Grapple piece  70  is formed by an open metal tube having a sharp valve piece  71 . Grapple piece  70  can be soldered to the second termination of the track. The grapple piece permits receiving the electrical wire which is positioned longitudinally relative to axis  15  inside the open tube while being gripped by valve piece  71 . This valve piece is designed to cut through the protective sheath of the wire in order to come into contact with the strand. The strand is then connected to the track by means of the grapple piece. 
     In order to assure that the electrical wire is held in box  2 , this box can be partially covered by an insulating cover  67  in an area of the box where electrical wire  6  penetrates ( FIGS. 6   a  and  6   b ).  FIG. 6   a  shows a cover  67  viewed from the top, and  FIG. 6   b  shows a cover  67  viewed from the bottom This cover  67  is also molded in such a way that it is adapted to the shape of electrical wire  6 , with a first section mated to the shape of stripped strand  65  and a second section adapted to that of strand  65  with its sheath  66 . 
     This cover  67  is molded so as to also form at least one setback portion  68  that is gripped on sheath  66  of electrical wire  6 . This setback portion  68  permits holding the electrical wire in the case. This cover also has an opening  81  that allows a part of the stripped strand of the electrical wire to appear. Cover  67  can also have a shape adapted to that of anvil piece  69  ( FIG. 6   b ). 
     According to another variant of the invention, electrical connector  1  can be made by several moldings. In  FIGS. 7   a  to  7   b , an insulating box  2  is shown, which is formed by a first molding of plastic, and by a second molding of a metal-coated plastic. This second plastic molding is designed to be partially metal-coated to form the future electrically conductive tracks. The first plastic molding permits electrically separating the tracks from one another. The second molding is shown by shading in  FIGS. 7   a  and  7   b.    
     The outer surface of the box is advantageously partially metal-coated to form an electromagnetic screen. 
     The metallization of the outer surface also comprises a metallization of the outer edges of peripheral wall  17 . In fact, the peripheral wall forms an outer edge  104  and an inner edge  105 , the inner edge being a part of the inner surface of the box and the outer edge forming a part of the outer surface of the same box. 
     The manufacturing process for such an electrical connector is described in regard to  FIGS. 11   a  to  11   d . First of all, at least one plastic molding is made in order to form the box as previously described ( FIG. 11   a ). Then this box is metal-coated to form at least one electrically conductive track ( FIG. 11   b ). A part of inner surface  32  of the box situated in the vicinity of recess  39  can also be metal-coated. 
     Then each of the tracks obtained can be partially coated with a layer of tin by tin-plating of first termination  40  and of second termination  41  ( FIG. 11   c ). This layer of tin, shown by the shading of  FIG. 11   c  permits soldering the first electrical contacts to the corresponding track, on the one hand, and soldering electrical wire  6  to the track, on the other hand. Recess  39  and the zone having a metal-coated surface in the vicinity of recess  39  can also be coated with a layer of tin. 
     Then outer surface  31  of the box is metal-coated. Then the first electrical contacts are inserted into the box ( FIG. 11   d ). 
     It is then sufficient to insert the electrical wires through rear face  4  of the connector, in order to position them in contact with the corresponding conductive track. The electrical wires can then be placed in an anvil piece, or even in a groove as previously described. A surface of the anvil piece or the groove designed to be in contact with the wire can be coated with an abrasion product which has the purpose of increasing the hold of the wire in the box once heated. The electrical cable can be connected to a metal-coated site near recess  39  in order to ground the cable. 
     Then the second contact is inserted into the corresponding cavity to connect it to a corresponding first electrical contact.