Abstract:
An electrical connector including dielectric housing; and a plurality of arrays of terminals disposed in respective portions of the dielectric housing, wherein at least two of the arrays of terminals have different pitches; and wherein at least one of the respective portions of the housing is partially removed such that a value of the dielectric constant between terminals of the array of terminals in said portion of the dielectric housing is controlled.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates broadly to the field of connectors, such as connectors used in printed circuit boards (PCB) and to a method of controlling electrical characteristics of an electrical connector. 
       BACKGROUND 
       [0002]    Electrical Connectors are often used in electronic devices to connect a PCB to another PCB or external devices. A PCB connector usually comprises a receiving member or a receptacle that is mounted to the PCB and a plug member. Each of the receptacle and plug members comprise arrays of electrical terminals. The housing of the receptacle and plug members are designed to cooperably mate with each other such that in an engaged position electrical connections are established between the respective electrical terminals of the receptacle and plug member. 
         [0003]    A typical connector comprises a dielectric housing containing an assembly of a plurality of electrical terminals of dimensions and pitch which are designed according to the specific usage. Often, electrical terminals are grouped in a plurality of arrays. Each array usually has a plurality of electrical terminals of the same pitch. 
         [0004]      FIG. 1  illustrates a perspective view of an existing SAS (serially attached SCSI) receptacle  10 . The elongate receptacle  10  comprises a dielectric housing which is moulded to accommodate the electrical terminals  7 . The receptacle  10  has three sets of arrays,  1 ,  2 , and  3 , of terminals  7  arranged on different planes of the receptacle. The terminals  7  are housed in respective chambers  5 . 
         [0005]    When designing a connector as shown in  FIG. 1 , factors such as signal integrity are of concern especially for fine pitched (e.g. 0.8 mm pitch) terminals. Parameters, such as cross-talk, are a problem especially in high frequency data transfer application. In particular, cross-talk is significant between fine-pitched terminals. 
       SUMMARY 
       [0006]    In accordance with a first aspect of the present invention there is provided an electrical connector comprising a dielectric housing; and a plurality of arrays of terminals disposed in respective portions of the dielectric housing, wherein at least two of the arrays of terminals have different respective pitches; and wherein at least one of the respective portions of the dielectric housing is partially removed such that a value of the dielectric constant between terminals of the array of terminals in said portion of the dielectric housing is controlled. 
         [0007]    The portion of the dielectric housing in which the array having a smaller pitch is disposed may be partially removed. 
         [0008]    The arrays of terminals may comprise one or more power terminal arrays and one or more signal terminal arrays. 
         [0009]    At least the portion of the dielectric housing in which one signal terminal array may be disposed is partially removed. 
         [0010]    At least one of the respective portions of the dielectric housing may be partially removed such that the terminals are partially exposed. 
         [0011]    The at least one of the respective portions of the dielectric housing may be partially removed such that an opening is formed in a wall of the dielectric housing in said portion, and the terminals extend across the opening. 
         [0012]    The at least one of the respective portions of the dielectric housing which is partially removed may comprise a protruded housing section of the dielectric housing. 
         [0013]    The connector may comprise a Serial Attached SCSI Receptacle. 
         [0014]    The terminals may comprise one or more of a group comprising through-hole, surface mount, press fit, and compression fit terminals. 
         [0015]    The value of the dielectric constant between terminals of the array of terminals in said portion of the dielectric housing may be reduced. 
         [0016]    In accordance with a second aspect of the present invention there is provided a method of controlling electrical characteristics of an electrical connector having a plurality of arrays of terminals disposed in respective portions of a dielectric housing, wherein at least two of the arrays of terminals have different respective pitches, the method comprising partially removing at least one of the respective portions of the dielectric housing of the connector such that a value of the dielectric constant between terminals of the array of terminals in said portion of the dielectric housing is controlled. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Non-limiting embodiments of the invention are described hereinafter with reference to the drawings, in which: 
           [0018]      FIG. 1  is a perspective view of a conventional SAS (serial attached SCSI) receptacle; 
           [0019]      FIG. 2  is a perspective view of an SAS (serial attached SCSI) receptacle according to an example embodiment of the present invention; 
           [0020]      FIG. 3   a  is a perspective view of an SAS (serial attached SCSI) receptacle according to an example embodiment of the present invention; 
           [0021]      FIG. 3   b  is an exemplified view of  FIG. 3   a  with electrical terminals dis-assembled; 
           [0022]      FIG. 4   a  is a perspective view of a plug in accordance with an example embodiment suitable for use with the SAS receptacle of  FIG. 2 ; and 
           [0023]      FIG. 4   b  is a perspective view of an assembly of the plug of  FIG. 4   a  and the SAS (serial attached SCSI) receptacle of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 2  illustrates a perspective view of a SAS (serially attached SCSI) receptacle  20  according to an example embodiment. The elongate receptacle  20  comprises a dielectric housing which is moulded to accommodate electrical terminals  28 ,  30 . The receptacle  20  has three sets of arrays, e.g.  33 , arranged on different planes of the receptacle  20 . A first array  31  consists of twenty-two terminals  28  of 1.27 mm pitch and is located towards one end  22  of the receptacle  20 , along one edge thereof, each terminal  28  being positioned in their respective chambers  36 . The terminals  28  of the first array  31  usually connect power lines. A second array  33  consists of eight terminals  30  of 0.8 mm pitch. The second array  33  is located towards the center  24  of the receptacle  20  and on the edge thereof which is opposite to the edge having the first array  31 . Each terminal  30  is positioned in respective slots  19 . The terminals  30  of the second array  33  usually connect signal lines. A third array  35  consists of seven terminals  28  of 1.27 mm pitch and is located on the other end  26  of the receptacle  20  and on the same edge thereof as that of the first array  31 , each terminal being positioned in their respective chambers  36 . The terminals  28  of the third array  35  usually connect signal lines. 
         [0025]    The first  31  and the third  35  arrays are located on the same edge of the receptacle  20  and are flush with the outer surface of the receptacle  20 , whilst the centre portion  24 , housing the second array  33 , protrudes out of the wall  22  of the receptacle  20 . 
         [0026]    Each of the ends  20 ,  26  of the receptacle  20  are terminated with a vertically positioned pillar  38  and a horizontally positioned base  40 . On one edge of each of the base  40 , a metallic terminal  42  is formed in a vertical direction to enable the receptacle to be inserted on to a PCB thereby providing rigidity to the receptacle  20 . The tail portions of the electrical terminals  28 ,  30  protrude the receptacle  20  and are of the press-fit type i.e. the tail portions of these terminals are resilient in a lateral direction to provide support to the receptacle connector and the PCB when the receptacle connector is inserted in to a PCB during assembly. 
         [0027]    The center portion  24  comprises the array  33  of electrical terminals  30  that are seated in slots  19 . Since the center portion  24  is used for electrically connecting signal lines, the pitch of the terminals  30  are usually lower than the pitch of those electrical terminals  28  that carry other lines e.g. power lines. The design of the low pitched electrical terminals  30  should be aimed at improving signal integrity and parameters, such as reduction of cross-talk. One way of achieving such an object is to reduce the dielectric constant of the dielectric material of the housing. Reducing or removing the dielectric material at the center portion  24  reduces the value of dielectric constant between the terminals  30 . This results in reduced capacitance, which is very important in high frequency applications. 
         [0028]    The reduction in dielectric material is achieved in the example embodiment by partially removing or reducing the dielectric material of the protruded center portion  24 . The protruded center portion  24  has upper and lower portions  200 ,  2020  respectively. The width  29  of the protrusion of the lower portion  202  is greater that of the width  27  of the upper portion  200 . 
         [0029]    The upper and lower portions  200 ,  202  are connected by an intersecting portion  21 , which is shown to be inclined in the example embodiment. The intersecting portion  21  may also be perpendicular to the edge of the receptacle  20 . The construction of the upper portion is a set of recesses  23 . The electrical terminals  30  are seated in the recesses  23 . 
         [0030]    The body of the electrical terminals  30  is seen partially embedded inside the slots  21  in the lower portion  202  of the centre portion  24  of the receptacle  20 . The tail of each of the electrical terminals  30  protrudes the receptacle  20 , to enable electrical connection with a PCB. The tail portions of the electrical terminals  30  are of the press-fit type. i.e. these terminals are resilient in a lateral direction to provide support to the receptacle connector and the PCB when the receptacle connector is inserted into a PCB during assembly. 
         [0031]    The receptacle  20  is designed to receive a plug  500 , as shown in  FIGS. 4   a  and  4   b , of a cable or another PCB, and as the plug co-operably mates with the receptacle  20 , electrical connections between the respective terminals  28 ,  30  of the receptacle  20  and the plug are established. 
         [0032]      FIG. 3   a  illustrates a perspective view of a SAS (serially attached SCSI) receptacle  30  according to the second embodiment. When compared to the first embodiment, the construction of the receptacle differs in the construction of the centre portion  24 . 
         [0033]    As in the second embodiment, the center portion  24  comprises an array  33  of electrical terminals  30  that are received in slots  49 . The protruded center portion  24  has upper and lower portions  302 ,  304  respectively. The width  50  of the lower portion  304  is greater than the width  52  of the upper portion  302 . The upper and lower portions  302 ,  304  are connected by an intersecting portion  48 , which is shown to be inclined in the example embodiment. The intersecting portion  48  may also be perpendicular to the edge of the receptacle  300 . 
         [0034]    Unlike the second embodiment, the part of the upper portion  302  lacks entirely the dielectric material resulting in an opening  46  in wall  22 . The slots  47  are present in the bottom portion  304  for receiving the terminals  30 , which extend across the opening formed in wall  22 . The heads of the electrical terminals  30  are positioned in their respective slots  49 . The tails of the electrical terminals  30  protrude the receptacle  300  to enable physical contact with a PCB. 
         [0035]      FIG. 3   b  is a view of  FIG. 3   a  with electrical terminals of  30  of the array  33  dis-assembled, fully exposing the opening  46  in wall  22 . Slots  49  can be seen on the top surface of the upper portion. Further, slots  47  are also present on the bottom surface of the upper portion. 
         [0036]    Each electrical terminal  30  has a head  54 , a body  56  and a tail  58 . The head  54  has a compression tip to enable physical connection with electrical terminals of a plug. The body  56  is elongate and is bent at appropriate positions for achieving resiliency. The tail portion  58  is press-fit type having resilience in the lateral direction of the terminal. This is to effectively insert a receptacle onto a PCB during assembly. 
         [0037]    The number of arrays and shown above can be less or more than three. The position and designation of the arrays for carrying signal and power lines can be altered. The number and pitch of electrical terminals of the arrays can be varied with a corresponding variation in the length of the receptacle. 
         [0038]    The dimensions of the arrays can be varied. The dimension and pattern of the removal of dielectric material may be altered. 
         [0039]    The tail portions of the electrical terminals  28 ,  38  are shown to be press-fit. Other types, such as compression, through hole, surface mount etc. may also be employed 
         [0040]    It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.