Abstract:
An electrical connector, comprising: a housing; and a plurality of modules received in said housing. Each module comprises: a printed circuit board assembly; and a plurality of contact secured to ends of traces located on outer surfaces of the printed circuit board assembly. The printed circuit board assembly also includes at least one shield layer located between the outer surfaces. A first group of the contacts engage a mating electrical component, and a second group of the contacts engage a circuit board to which the electrical connector mounts.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 08/784,744, filed on Jan. 16, 1997 and now U.S. Pat. No. 6,183,301, herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical connectors. More specifically, the present invention relates to high speed, shielded electrical connectors having one or more integrated PCB assemblies. 
     2. Brief Description of Earlier Developments 
     U.S. Pat. No. 4,571,014 shows an approach for the manufacturing of backplane connectors using one or more PCB assemblies. Each of the PCB assemblies comprises one insulated substrate, one spacer, and one cover plate, all of which are attached to one another. The insulating substrate is provided with a predetermined pattern of conducting tracks, while ground tracks are provided between the conducting tracks. The conducting tracks are connected at one end to a female contact terminal for connection to the backplane and at the other end to a male through-hole contact terminal. 
     PCT Patent Application Serial No. US96/11214 filed Jul. 2, 1996 also discloses connectors employing side-by-side circuit substrates. The connectors disclosed in that application also employ through-hole terminals to make a mechanically and electrically secure connection to the circuit board on which the connector is to be mounted. The disclosure of the above-mentioned application is incorporated herein by reference. 
     While both of the above-mentioned connector arrangements can yield useful interconnection systems, many manufacturers of electronic equipment prefer to surface mount components on printed circuit boards. Surface mounting provides enhanced opportunities for miniaturization and the potential for mounting components on both sides of the circuit board. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide high speed electrical connectors with one or more integrated PCB assemblies. 
     It is a further object of the present invention to provide electrical connectors having relatively low manufacturing costs. 
     These and other objects of the present invention are achieved in one aspect of the present invention by an electrical connector, comprising: a housing; and a plurality of modules received in said housing. Each module comprises: a printed circuit board assembly; and a plurality of contact secured to ends of traces located on outer surfaces of the printed circuit board assembly. The printed circuit board assembly also includes at least one shield layer located between the outer surfaces. A first group of the contacts engage a mating electrical component, and a second group of the contacts engage a circuit board to which the electrical connector mounts. 
     These and other objects of the present invention are achieved in another aspect of the present invention by a right angle receptacle, comprising: a housing; and a plurality of modules received in the housing. Each module comprises: a printed circuit board assembly and a plurality of contacts secured to traces located on outer surfaces of the printed circuit board assembly. The printed circuit board assembly also has: a first edge locatable adjacent a mating connector; a second edge locatable adjacent a circuit board to which the receptacle mounts; and at least one shield layer between said outer surfaces. A first group of contacts are located at the first edge and engage the mating connector. A second group of contacts are located at said second edge and engage the circuit board. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which: 
     FIG. 1 shows in partial cross-section a connector illustrating the principles of the present invention; 
     FIG. 1 a  is an enlargement of the circled area of FIG. 1; 
     FIG. 2 shows a rear view of the connector shown in FIG. 1; 
     FIG. 3 is a partial bottom view of the connector shown in FIG. 1; 
     FIG. 4 is a partial isometric view of a PCB assembly according to the invention; 
     FIG. 4 a  is a fragmentary view of a PCB assembly having a shield layer on the obverse side of the PCB; 
     FIG. 5 is a partial cross-sectional view showing an alternative mounting of shield terminals on the PCB assembly of the connector shown in FIG. 1; 
     FIG. 5 a  is an illustration of the circled area in FIG. 5 with the shield/hold down terminal in an actual surface mount orientation; 
     FIG. 6 is a rear view of the connector of FIG. 5; 
     FIG. 7 is a front view of a hold down terminal used with the connector in FIG. 5; 
     FIG. 8 is a side view of the hold down terminal shown in FIG. 7; and 
     FIG. 9 illustrates a second form of mounting interface terminal. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It is to be understood that, although the figures illustrate right angle connectors, the principles of the present invention equally apply to other connector configurations. 
     Electronic components E, such as resistors, capacitors and inductors, could be associated with the traces  16 ,  18  on PCB  10  for filtering purposes. These filtering elements could be easily incorporated into the PCB  10  using known manufacturing processes, such as thin film techniques. 
     Referring to FIG. 1, the PCB assembly  10  comprises an insulating substrate  12  of a material commonly commercially used for making PCBs. The substrate  12  can be a substantially planar resin impregnated fiber assembly, such as is sold under the designation FR4, having a thickness 0.4 mm, for example. 
     On a first surface of the substrate  12 , a plurality of circuit or signal traces  16  are formed by conventional PCB techniques. Each trace  16  extends from a first portion of the substrate  10 , for example adjacent the front edge as shown in FIG. 1, to a second area or region of the substrate  10 , such as the bottom edge as shown in FIG.  1 . The traces  16  may include contact pads at one end adapted to have metal terminals secured to them, as by conventional surface mounting techniques using solder or welding. 
     A plurality of ground or shielding traces  18  may also be applied to the substrate  10 . The shielding traces  18  may be disposed between each of the circuit traces  16  or between groups of such traces. A terminal, such as a contact terminal  20  is mounted at the first end of each trace  16 . Board mounting terminals  22 , described in greater detail below, are disposed at the second end of each circuit trace  16 . An additional shielding or ground layer  24  may be applied to the remainder of the trace bearing side of substrate  12 . A ground or shield terminal  28  is fixed onto the ground layer  24 . 
     Electronic components, such as resistors, capacitors and inductors, could be associated with the traces  16 ,  18  on PCB  10  for filtering purposes. These filtering elements could be easily incorporated into the PCB  10  using known manufacturing processes, such as thin film techniques. 
     The contact structures  22  comprise surface mount terminals for electrically interconnecting each of the traces  16  with a circuit trace printed on the circuit substrate (not shown) onto which the connector is to be mounted. In a preferred arrangement, the contact structures  22  include a compressible or deformable element  30  formed of an elastomeric material. The element  30  may be circular in cross-section (as shown), D-shaped or another appropriate shape. The member  30  can be a continuous, elongated member that extends between several PCB modules, as shown (in FIG.  3 ), along aligned edges. In this case, the member has alternating non-conductive regions  32  and conductive regions  34 , which can be formed by metallized coatings. The conductive regions are generally aligned with the centerlines of the contacts  20 . In this manner, the row pitch of the connector at the mating interface is carried through to the contact pitch at the mounting interface. 
     Along an edge  38  of the PCB  12  adjacent the ends of tracks  16 , are suitably shaped recesses or notches  36 , that may, for example, have a trapezoidal form as in FIG. 1 a  or a circular form, as shown in FIG. 4 a . The compressible member  30  is received in and retained, as by a push fit, in the notches  36  with a portion extending beyond edge  38 . This arrangement provides a mounting interface with good coplanarity. The inside surfaces  36   a  of each notch  36  are metallized, preferable by a coating that is continuous with the circuit trace  16 . 
     If a shield or ground layer  37  (FIG. 4 a ) is present on the obverse side of PCB  12 , the shield should be spaced from the notch  36 , so that the notch remains electrically isolated from the shield layer, as is shown in more detail below. The covers  14  are similarly notched to accept the compressible member  30 . The conductive sections  34  are arranged so that one end portion extends into the notch  36  and is in electrical contact with the plating on the interior surfaces  36   a  of the notch. 
     Each PCB module  10  preferable includes a hold-down for holding a connector formed from a plurality of such modules on a circuit substrate. In FIG. 1, the press-fit terminal  28  comprises such a hold-down. As well, the location peg  71  and hold-down pegs  73  of the housing  70  can be utilized to provide hold down or board retention functions. When the connector is pressed onto the receiving circuit substrate and the terminals  28  are pressed into holes on the circuit substrate, the portion of each element  30  extending beyond edge  38  is compressed. This compression creates normal forces that press the conductive portions  34  against the conductive traces on the mounting substrate and the surfaces  36   a  of the notches. As a result, a secure electrical connection is made between signal traces  16  and corresponding circuit traces on the mounting substrate. 
     The compressible members  30  can also comprise metallic elements, for example, elastically deformable spring contacts or non-elastically deformable metal contacts. Further, the compressible members  30  can comprise individual conductive elements, each one being associated with one of the notches  36 . For example, the member  30  may comprise an elastically deformable, conductive spherical element or a heat deformable element, such as a solder ball (described below). 
     A locating hole  40  may be placed in the substrate  12 . The locating hole  40  preferably comprises a plated through-hole for establishing electrical connection with a metallic shield layer  37  (see FIG. 4 a ) extending across the back surface of the substrate  12 . As also previously described, small vias (not shown) forming plated through-holes may be disposed in each of the ground traces  18  so that the ground traces  18 , the shield layer  24  and the back shield layer  37  form a shielding structure for the signal traces  16  and associated terminals. 
     As shown in FIG. 1, contact terminals  20  are formed as a one-piece stamping and can comprise a dual beam, contact defining an insertion axis for a mating terminal, such as a pin from a pin header. 
     A terminal module  10  is formed by associating a PCB assembly  12  with a cover  14 . The cover  14  and PCB  12  are configured and joined substantially in the same manner as described in the above-referenced PCT patent application. The terminals  28  are located in the contact recesses  42  in covers  14 . 
     If the board mounting terminal  28  is of a type that is likely to have a relatively high axial insertion force applied to it as the terminal is pushed into a through hole on the mounting substrate, such as a press-fit terminal, the surface  42   a  (FIG. 1) of the recess  42  is advantageously located so that it bears against the upturned tang  28   a  of the terminal  28 . As previously noted in the above-identified PCT application, this arrangement allows the insertion force applied to the connector to be transmitted to terminal  28  through cover  14  in a manner that minimizes shear stress on the connection between terminal  28  and PCB  12 . 
     FIG. 2 shows a rear view of a connector comprising a molded plastic housing  70  and a plurality of PCB modules  10  in side-by-side relationship. In the connector shown in FIG. 2, the circuit boards  12  are located in back to back relationship, so that corresponding signal pairs (the location of which is shown schematically by small squares  11 ) can be arranged in twinax pairs. However, other shielded or non-shielded signal contact arrangements can be used. The PCB modules  10  are secured in housing  70 , preferably by upper and lower dove tail ribs  66  and  64 , respectively, formed in each of the covers  14 . The ribs  66  and  64  are received in upper and lower dove tail grooves  68  and  65 , respectively, formed on the inner top and bottom surfaces of housing  70 . 
     As illustrated in FIG. 2, each circuit board includes a press fit terminal  28 . The region of the bottom side of the connector at which the surface contact members  30  are located in flanked at one end by the retention pegs  73  and at the other by the press fit terminals  28 , to ensure adequate compressive force for urging the members  30  against contact pads (not shown) on the mounting substrate. 
     FIG. 4 is an fragmentary isometric view of a rear bottom corner of PCB  12  before terminals or conductive elements are associated with notches  36 . It shows signal traces  16  that terminate at an edge of the board  12 . Recesses  36  are formed at the edge of the PCB  12  and the surfaces  36   a  of the recesses are plated, so that there is electrical continuity between traces  16  and recesses  36 . Referring to FIG. 4 a , if the PCB carries a shield layer  37  on the side opposite the side on which signal traces  16  and shield traces  18  are printed, the shield layer is spaced from recesses  36 , for example, by the unplated regions  39 . 
     FIG. 5 shows a partial cross-sectional view of a connector having a convertible form of hold-down terminal  50 . FIGS. 5 and 6 show the terminal  50  positioned for press fitting into a mounting substrate and FIG. 5 a  shows how the terminal is positioned for surfacing mounting by being bent 90°. The terminals  50 , shown in greater detail in FIGS. 7 and 8, have a mounting section  52  and compliant through-hole sections  54 . 
     The mounting section  52  includes a base  55  and a solder tab  56  disposed in substantially a right angle relationship with base  55 . The mounting section  52  is joined to the compliant sections  54  by a reduced width neck section  53 . 
     The compliant section  54  comprises a pair of legs  58  that are movable inwardly when forces in the compliance direction of arrows F are imparted to legs  58  as it is inserted in a through-hole. As is known, elastic deformation of legs  58  creates a normal force that in turn creates a frictional force that opposes movement in the direction of the longitudinal axis of terminal  50  for retaining the terminal in a through-hole. 
     Each terminal  50  is mounted on an associated PCB by solder tab  56 . Such mounting positions the planes of base  55  and compliant section  54  substantially transverse to the plane of the PCB. If the angle between base  52  and solder tab  56  is 90°, then the planes of base  52  and compliant section  54  will be substantially normal to the plane of PCB  12 . 
     An advantage of this positioning is that the terminal can readily be converted to a surface mount terminal by bending the section  54  with respect to the base section  52  in the region of neck  53  as shown in FIG. 5 a . As a result, the section  54  can be bent 90° to be positioned substantially parallel to the surface of the circuit board to which the connector is mounted. This places the compliant section  54  in an orientation to be surface mounted on the connector-receiving circuit board. A strong solder attachment can be made because the solder meniscus can extend along and through the opening  57 . 
     Another advantage of the terminal  50  is that it can be used as normal press fit terminals by soldering the base  55  onto the PCB  12 , to position the compliant section  54  in the same orientation as terminal  28  shown in FIGS. 1 and 2. In this orientation the tab  56  functions in the same manner as tab  28   a  (FIG. 1) to take the axial force applied to the terminals during board insertion. 
     In the foregoing description, the mounting interface terminals  22  have been described principally as elements that are deformable upon the application of force. The terminals  22  (FIG. 1) can also comprise elements that are deformable upon the application of heat. In this regard, FIG. 9 illustrates an embodiment wherein the conductive recesses or notches  36  in edge  38  of PCB  12  receive a heat deformable element  60 . 
     The element  60  as shown is a generally cylinderical body of solder. Alternatively, the body  60  may be other shapes, for example, a spherical solder ball. The element  60  can be retained in recess  36  by a snap or friction fit, by solder paste, or by fusing the element  60  into notch  36 , as by a reflow operation. An advantage of this embodiment is that connectors using this form of terminal at the mounting interface can be mounted without the need for a hold down arrangement that must maintain compressive forces, as in the previously described embodiment. 
     The term “surface mount” when used in the specification and claims with respect to the board mounting terminals or contacts  22  is meant to connect the absence of a through-hole type of connection and is not meant to refer solely to interconnections using solder or solder paste. 
     The foregoing constructions yield connectors with excellent high speed characteristics at low manufacturing costs. Although the preferred embodiment is illustrated in the context of a right angle connector, the invention is not so limited and the techniques disclosed in this application can be utilized for many types of high density connectors systems wherein signal contact are arranged in rows and columns. 
     While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.