Abstract:
An electrical connector includes an insulative housing with a number of passageways, a number of electrical contacts received in the passageways and a number of solder balls disposed on the electrical contacts respectively. The electrical contact or together with the insulative housing form a retention feature for pre-setting the solder balls thereon.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to an electrical connector and, more particularly, to an electrical connector with solder balls secured to the contacts thereof. 
     2. Description of Related Art 
     Central processing unit (CPU) sockets are used to transmit signals between a CPU and a printed circuit board in computer device. Generally, the CPU socket comprises an insulative housing and a plurality of conductive terminals. Each of the conductive terminals electrically connects with the printed circuit board through surface mounting technology (SMT) by pre-setting solder balls on one end thereof. 
     Chinese patent issue No. 2610515Y issued to Lotes on Apr. 7, 2004 discloses one type of electrical connector which includes an insulative housing 12 and a number of electrical contacts 14. The insulative housing 12 defines a number of straight passageways 120 for receiving the electrical contacts 14 therein and a projection 122 is disposed in a lower end of the passageways 120. The electrical contact 14 is configured to a U shaped configuration and has a pair of solder ends at a lower end thereof for receiving a solder ball. The electrical contacts are used to pre-set the solder balls before surface mounting to the PCB. 
     Chinese patent issue No. 2872630Y issued to Lotes on Feb. 21, 2007 discloses another type of electrical connector for pre-setting solder balls. The electrical connector includes an insulative housing 1 with passageways 10 therein and a plurality of electrical contacts 2 received in the passageways 10. The insulative housing 1 defines a number of solder ball receiving portions 12. Bottom end 21 of the contact 2 and side wall 14 of the solder receiving portion 12 jointly define a receiving space 16 for the solder ball 3 moveably received therein. The solder balls are hold by the side wall 14 and the bottom end 21 of the contact 2 whereby to be pre-set on the electrical connector. 
     The above electrical connectors are two schemes to locate the solder balls thereon before surface mounting to the PCB. The present invention provides a different method to locate and connect the solder ball. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an electrical connector with improved retention feature for pre-setting solder balls on the electrical contacts thereof. 
     An electrical connector comprises an insulative housing with a plurality of passageways extending therethrough and a plurality of electrical contacts retained in the passageways. Each electrical contact comprises a plate portion interfering with the insulative housing, a pair of upper arms extending upwardly from the plate portion and a pair of lower arms extending downwardly from the plate portion. The upper and lower arms are twisted so as to have free ends thereof run out of a vertical plane defined by the plate portion. 
     According to one of the embodiments, an electrical connector comprises an insulative housing defining a plurality of passageways extending therethrough and having a top surface and a bottom surface opposite to each other. A plurality of electrical contacts are retained in the passageways and each comprises a plate portion interfering with the insulative housing, a contact portion extending upwardly from the plate portion and a solder portion extending downwardly from the plate portion. The insulative housing comprises a plurality of retention features projecting from the bottom surface thereof which define a receiving space together with the solder tail of the contact for receiving a solder ball therein and form four supporting points contacting with the solder balls. 
     Still yet according to one of the embodiments, an electrical connector comprises an insulative housing defining a plurality of passageways extending therethrough and having a top surface and a bottom surface opposite to each other. A plurality of electrical contacts are retained in the passageways and each comprises a plate portion interfering with the insulative housing, a contact portion extending upwardly from the plate portion and a solder portion extending downwardly from the plate portion. The solder portion projects out of the bottom surface of the insulative housing and has an annular portion. The annular portion has a gap penetrating therethrough and has a supporting portion adjacent to the gap. The annular portion is expanded for securing a solder ball with the supporting portion limited by the insulative housing in a vertical direction. 
     Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective, assembly view of the electrical connector of a preferred embodiment according to the present invention; 
         FIG. 2  is another perspective view of the electrical connector shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of the electrical contact shown in  FIG. 2  with a solder ball disposed thereon; 
         FIG. 4  is a top view of the electrical connector shown in  FIG. 1 ; 
         FIG. 5  is a bottom view of the electrical connector shown in  FIG. 1 ; 
         FIG. 6  is a perspective, assembly view of an electrical connector according to a second embodiment of the present invention; 
         FIG. 7  is another perspective view of the electrical connector shown in  FIG. 6 ; 
         FIG. 8  is a perspective view of the insulative housing shown in  FIG. 6 ; 
         FIG. 9  is a cross-sectional view of the electrical connector shown in  FIG. 6 ; 
         FIG. 10  is a perspective, assembly view of the electrical connector according to a third embodiment of the present invention; 
         FIG. 11  is another perspective view of the electrical connector shown in  FIG. 10 ; 
         FIG. 12  is a bottom view of the electrical connector before the solder ball inserter therein; 
         FIG. 13  is a bottom view of the electrical connector shown in  FIG. 1 ; and 
         FIG. 14  is a cross-sectional view of the electrical connector shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will be made to the drawing figures to describe the present invention in detail, wherein depicted elements are not necessarily shown to scale and wherein like of similar elements are designated by same or similar reference numeral through the several views and same or similar terminology. 
     Please referring  FIGS. 1-2 , an electrical connector  100  according to a prefer embodiment of the present invention comprises an insulative housing  10  with a plurality of passageways  12  extending therethrough and a plurality of electrical contacts  20  retained in the passageways  12 . The insulative housing  10  has a top surface  101  and a bottom surface  102  opposite to each other. 
     Please also referring to  FIGS. 3-5 , each electrical contact  20  comprises a plate portion  21  interfering with the insulative housing  10 , a pair of upper arms  22  extending upwardly from the plate portion  21  and a pair of lower arms  23  extending downwardly from the plate portion  21 . The upper and lower arms  22 ,  23  are twisted so as to make free ends thereof run out of a vertical plane defined by the plate portion  21 . 
     The upper arms  22  are twisted to opposite directions whereby forms a pair of twist portion  223  connecting with the plate portion  21  and a pair of contact portions  221  at the free ends thereof. The contact portions  221  are located at an upper end of the passageways  12  and define an upper space  25  therebetween. The pair of contacting portions  221  each has a guiding section  222  bent outwardly therefrom and defines an enlarged entrance (not labeled) which is communicated with the upper space  25 . The contact portions  221  are perpendicular to the plate portion  21 . 
     The pair of lower arms  23  is twisted to a same direction and define a lower space  24  therebetween. The lower arm  23  each has a twist portion  232  connecting with the plate portion  21 . The free ends of the pair of lower arms  23  form a pair of solder portions  231  to clip a solder ball  30  therebetween. The solder portions  231  project out of the bottom surface  102  of the insulative housing  10 . The solder portions  231  are perpendicular to the plate portion  21 . 
       FIGS. 6-9  illustrates a second embodiment according to the present invention. An electrical connector  100 ′ comprises an insulative housing  10 ′ defining a plurality of passageways  12 ′ extending therethrough and having a top surface  101 ′ and a bottom surface  102 ′ opposite to each other. A plurality of electrical contacts  20 ′ are retained in the passageways  12 ′ and each comprises a plate portion  21 ′ interfering with the insulative housing  10 ′, a contact portion  22 ′ extending upwardly from the plate portion  21 ′ and a solder portion  23 ′ extending downwardly from the plate portion  21 ′. 
     Please refer to  FIGS. 7 and 8 , the insulative housing  10 ′ comprises a plurality of retention features  14 ′ projecting from the bottom surface  102 ′ thereof. The retention feature  14 ′ and the solder tail  23 ′ of the contact  20 ′ together define a receiving space  15 ′ for receiving a solder ball  30 ′ therein. 
     The retention feature  14 ′ comprises three spring arms  141 ′ integrally formed on the insulative housing  10 ′ and located at three sides of the passageway  12 ′. The solder portion  23 ′ of the electrical contact  20 ′ is located at another side of the passageway  12 ′. Each spring arm  141 ′ has a clip portion  142 ′ extending inwardly to the receiving space  15 ′ at free end thereof and the clip portion  142 ′ has an arc contour corresponding to the solder ball  30 ′. The insulative housing  10 ′ comprises a plurality of stand-offs  16  on the bottom surface  102 ′ and the stand-offs  16 ′ are extending downwardly beyond the retention features  14 ′. 
     Please refer to  FIGS. 7 and 9 , the retention feature  14 ′ and the electrical contacts  20 ′ provide retention force for the solder ball  30 ″ at four sides thereof. After the solder ball  30 ′ is located in the receiving space  15 ′, there are four supporting points contacting with the solder ball  30 ′. One of the supporting points is formed on the solder portion  23 ′ of the electrical contact  20 ′ and the other three supporting points are formed on the retention feature  14 ′. 
       FIGS. 10-14  illustrates a third embodiment according to the present invention. An electrical connector  100 ″ comprises an insulative housing  10 ″ defining a plurality of passageways  12 ″ extending therethrough and having a top surface  101 ″ and a bottom surface  102 ″ opposite to each other; and a plurality of electrical contacts  20 ″ retained in the passageways  12 ″. 
     Please refer to  FIGS. 10 and 11 , each electrical contact  20 ″ comprises a plate portion  21 ″ interfering with the insulative housing  10 ″, a contact portion  22 ″ extending upwardly from the plate portion  21 ″ and a solder portion  23 ″ extending downwardly from the plate portion  21 ″. The plate portion  21 ″ had a plurality of J-legs  211 ″ at opposite edges thereof for engaging with the insulative housing  10 ″. The solder portion  23 ″ projects out of the bottom surface  102 ″ of the insulative housing  10 ″ and has an annular portion  230 ″ with a gap  232 ″ penetrating therethrough and breaking the annular portion  230 ″. The solder portion  23 ″ further has a supporting portion  231 ″ adjacent to the gap  232 ″. 
     The supporting portion  231 ″ is located in the contour of the passageway  12 ″ before the solder ball  30 ″ inserted therein as shown in  FIG. 12  and expands out of the contour of the passageway  12 ″ as shown in  FIG. 13 . The annular portion  230 ″ is round which also could be triangular, square or other polygon. The annular portion  230 ″ defines a lead-in chamfer  233 ″ at lower edge thereof for guiding a solder ball  30 ″ inserted into the annular portion  230 ″. The annular portion  230 ″ is smaller than the passageways  12 ″ of the insulative housing  10 ″ and turns to be larger than the passageway  12 ″ after the solder ball  30 ″ inserted therein. The annular portion  230 ″ is expanded to the biggest radius of the solder ball  30 ″ thereby securing the solder ball  30 ″ both in three directions. Furthermore, the supporting portion  231 ″ is limited by the insulative housing  10 ″ in a vertical direction thereby ensuring co-planarity of the solder balls  30 ″ as shown in  FIG. 14 . 
     The solder balls  30 ″ are retained in the vertical annular portion  230 ″. Since the diameter of the annular portion  230 ″ is smaller than the solder ball&#39;s  30 ″ diameter which can hold the solder ball  30 ″ in place. The smaller diameter of the annular portion  230 ″ also can reduce the thickness of the insulative housing  10 ″, which is specifically important for fine pitch applications. Moreover, when the annular portion  230 ″ are opened with the solder ball  30 ″ seated in, two supporting portions  231 ″ are engaging with the bottom surface  102 ″ in a vertical direction and prevent tilting or bending of the solder ball  30 ″ in the electrical contact  20 ″. The solder ball  30 ″ could be set to the required depth by co-planarity. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.