Patent Publication Number: US-6908328-B2

Title: Electrical connector with accurately secured contacts

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electrical connector for electrically connecting an electronic package such as a pin grid array (PGA) chip with a circuit substrate such as a printed circuit board (PCB), and more particularly to an electrical connector providing accurate positioning of conductive contacts therein. 
   2. Description of the Related Art 
   Conventional central processing unit (CPU) sockets have contacts received in passageways of an insulative housing, for electrically connecting CPUs to PCBs. The contacts have engaging portions extending from one or two side edges thereof. The thickness of one whole engaging portion is approximately equal to the width of a fastening recess of each passageway. Thus the engaging portions are firmly held in the passageway, and the contact is securely fixed in the housing. 
   The trend toward miniaturization of electrical connectors and the development of surface mount technology (SMT) both require precise positioning of the contacts in the passageways. Coplanarity of soldering portions of all contacts in a CPU socket is very important for achieving precise soldering by way of SMT, especially for a ball grid array (BGA) connector. Conventional contacts are too small to be accurately inserted into the passageways of a housing of a BGA socket. Small gaps remain between interferential engaging portions of each contact and walls of the housing at a fastening recess of each passageway. In addition, the contacts may be inaccurately installed in the corresponding passageways during assembly of the BGA connector. For example, some contacts may be inserted at incorrect angles. This causes soldering portions of the contacts to be tilted relative to a PCB. The above-mentioned small gaps can be eliminated by ensuring that a thickness of the engaging portion of the contact is exactly equal to a width of the fastening recess of the passageway. However, insertion of the contact into the passageway is difficult and problematic. Forced insertion can result in plastic deformation of the housing at the passageway, and damage to the contact itself. Retaining the contacts in correct positions while still ensuring coplanarity of the soldering portions of the contacts has not yet been satisfactorily achieved. There remains unduly high risk of unstable connection between the contacts and the PCB. Contacts such as those disclosed in the U.S. Pat. Nos. 6,319,038, 5,797,774 and 5,299,950 bear out the above-described problems. 
   An improved CPU socket is desired to overcome the above-described shortcomings of conventional CPU sockets. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an electrical connector having precisely positioned contacts for ensuring reliable electrical connection between soldering portions of the contacts and a printed circuit board (PCB). 
   To achieve the above object, a connector of the present invention is for electrically connecting pins of a central processing unit (CPU) with a PCB. The connector comprises an insulative housing, a multiplicity of passages defined in the housing, and a multiplicity of conductive contacts secured in corresponding passages. Each passage comprises a receiving portion and a fastening recess. The fastening recess comprises a flared upper portion. Each contact comprises a soldering portion for being soldered to the PCB, a pair of contact portions for engaging with a corresponding output pin of the CPU, and a body portion interconnecting the soldering portion and the contact portions. Two pairs of engaging portions are formed on opposite lateral edges of the body portion respectively. Each engaging portion comprises an upper fixing part and a lower guiding part. Each guiding part is tapered such that a bottom end thereof is narrower and thinner than a top end thereof. When the contact is engaged in the corresponding passage of the housing, the tapered guiding parts and the flared upper portion cooperate to facilitate correct insertion of the contact. That is, even if the contact is initially inserted imprecisely or at an incorrect angle, the guide portions and the flared upper portion can gradually lead the contact to a correct final position and orientation in the passage. Thus the contacts can be precisely fixed in the passages of the housing. This ensures reliable connection between the soldering portions and the PCB, and between the contact portions and the output pins of the CPU. 
   Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded isometric view of the electrical connector in accordance with the preferred embodiment of the present invention, but showing only one contact thereof; 
       FIG. 2  is an enlarged view of a circled portion II of  FIG. 1 , showing details of one passage of a housing of the connector; 
       FIG. 3  is an enlarged isometric view of the contact of  FIG. 1 ; 
       FIG. 4A  is an enlarged side plan and partly cross-sectional view of the contact and of the housing at the passage, showing the contact ready to be insert into the passage; 
       FIG. 4B  is similar to  FIG. 4A , but showing the contact partly insert into the passage; 
       FIG. 4C  is similar to  FIGS. 4A and 4B , but showing the contact fully inserted into the passage; and 
       FIG. 5  is an enlarged isometric view of part of the connector of  FIG. 1 , showing the contact fully inserted into the passage. 
   

   DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
   Reference will now be made to the drawings to describe the present invention in detail. 
   Referring to  FIGS. 1 ,  2  and  3 , an electrical connector  1  in accordance with a preferred embodiment of the present invention is for electrically connecting a central processing unit (CPU) to a printed circuit board (PCB). The connector  1  comprises an insulative housing  2 , a multiplicity of conductive contacts  3  secured in the housing  2 , a cover  4  slidably mounted on the housing  2 , and an actuation device  5  for actuating the cover  4  to slide along the housing  2 . The housing  2  defines a multiplicity of passages  20  respectively receiving the contacts  3 . Each passage  20  comprises a receiving portion  201  and a fastening recess  202 . Each fastening recess  202  comprises a flared upper portion  2021 . That is, the fastening recess  202  is largest at a top surface of the housing  2 , for facilitating insertion of a corresponding contact  3  into the passage  20 . 
   Each contact  3  comprises a soldering portion  31  for being soldered to the PCB, a pair of contact portions  33  for engaging with a corresponding output pin (not shown) of the CPU, and a body portion  32  interconnecting the soldering portion  31  and the contact portions  33 . The soldering portion  31  is perpendicular to the body portion  32 , and parallel to the PCB. Two pairs of engaging portions  340  are formed on opposite lateral edges of the body portion  32  respectively. Each engaging portion  340  comprises a lower guiding part  3401  and an upper fixing part  3402 . Each guiding part  3401  is tapered such that a bottom end thereof is narrower and thinner than a top end thereof. A thickness of each fixing part  3402  is slightly greater than a width “a” of the fastening recess  202  of each passage  20 , as shown in FIG.  2 . Each fixing part  3402  has a distal end  35 . The contact portions  33  extend from respective opposite lateral edges of the body portion  32  between corresponding engaging portions  340 . 
   Referring to  FIGS. 4   a ,  4   b ,  4   c  and  5 , the contacts  3  are engaged in the passages  20  of the housing  2 . The body portion  32  of each contact  3  is inserted into the corresponding fastening recess  202 , and the soldering and contact portions  31 ,  33  of the contact  3  are received in the corresponding receiving portion  201 . The tapered guiding parts  3401  and the flared upper portion  2021  cooperate to facilitate correct insertion of the contact  3 . That is, even if the contact  3  is initially inserted imprecisely or at an incorrect angle, the guide portions  3401  and the flared upper portion  2021  can gradually lead the contact  3  to a correct final position and orientation in the passage  20 . Thus the contacts  3  can be precisely fixed in the passages  20  of the housing  2 . This ensures reliable connection between the soldering portions  31  and the PCB, and between the contact portions  33  and the output pins of the CPU. 
   When each contact  3  is finally fixed in its corresponding passage  20 , the distal ends  35  of the fixing parts  3402  press corresponding side walls of the housing  2  at the fastening recess  202 . In addition, opposite faces of the fixing parts  3402  interferentially engage with corresponding side walls of the housing  2  at the fastening recess  202 , because the thickness of each fixing part  3402  is slightly greater than the width of the fastening recess  202 . Thus the contact  3  is firmly and reliably secured in the passage  20 . 
   Although the present invention has been described with reference to a particular embodiment, it is not to be construed as being limited thereto. Various alterations and modifications can be made to the embodiment without in any way departing from the scope or spirit of the present invention as defined in the appended claims.