Patent Publication Number: US-2003232523-A1

Title: Electrical connector having reliable soldering configuration

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an electrical connector for electrically connecting an electronic package such as a central processing unit (CPU) with a circuit substrate such as a printed circuit board (PCB), and particularly to an electrical connector with solder balls for soldering to the PCB.  
       [0003] 2. Description of Related Art  
       [0004] Ball grid array (BGA) sockets are widely used in personal computer (PC) systems to electrically connect CPUs with PCBs. A BGA socket comprises a plurality of terminals, with each terminal having a solder ball attached thereon.  
       [0005] A conventional soldering procedure for fixing the socket on the PCB comprises the following steps. Firstly, the socket is positioned on the PCB. Secondly, the socket together with the PCB is put into an infrared (IR) oven. Thirdly, the solder balls on the terminals of the socket are heated, melted and fixed on the PCB. The socket is thereby fixed on the PCB via the solder balls. This conventional procedure is disclosed in “BGA sockets: a dendritic solution” (P460-466, 1996 IEEE 46th electronic Components &amp; Technology Conference).  
       [0006] Referring to FIGS. 5, 6 and  7 , a conventional electrical connector  9  for electrically connecting a CPU (not shown) with a PCB  8  comprises an insulative base  91 , a rectangular cover  92  slidably engaged on the base  91  and adapted to have the CPU seated thereon, and a cam actuator  93  for actuating the cover  92  to slide along the base  91  to electrically connect or disconnect the CPU with the PCB. The base  91  comprises a thick first portion  94  defining a mounting surface  941  for mounting on the PCB  8 , and a thin second portion  95  defining a plurality of receiving holes for receiving corresponding electrical terminals therein. Each terminal comprises a solder ball  954  fused on one end thereof that faces toward the PCB  8 . The cover  92  has a pair of protrusions  96  formed on two bottom corner portions thereof respectively. Bottom extremities of the first portion  94  and the protrusions  96  are at a same level, such level being parallel to a bottom surface of the second portion  95 . This helps ensure that the electrical connector  9  and the PCB  8  are coplanar when the solder balls  954  are soldered to the PCB  8 .  
       [0007] When the electrical connector  9  is soldered on the PCB  8 , the solder balls  954  are heated and melted. The mounting surface  941  of the first portion  94  of the base  91  in cooperation with the protrusion  96  of the cover  92  control an extent to which the melted solder balls  954  deform. This helps ensure that the electrical connector  9  and the PCB  8  are coplanar. However, the first portion  94  prevents heating airflow from reaching certain areas of the second portion  95 , especially a central area of the second portion  95  close to the first portion  94 . As a result, solder balls  954  located in said central area cannot be adequately and uniformly heated. As a result, the solder balls  954  cannot be accurately fused with the PCB  8  at one time. This can lead to faulty performance or even failure of the electrical connector  9 .  
       [0008] A new electrical connector that overcomes the above-mentioned disadvantages is desired.  
       SUMMARY OF THE INVENTION  
       [0009] Accordingly, an object of the present invention is to provide an electrical connector for electrically connecting a CPU with a PCB which can ensure that all solder joints of the connector are adequately and uniformly heated when the connector is soldered to the PCB.  
       [0010] To achieve the above-mentioned object, an electrical connector in accordance with a preferred embodiment of the present invention is for electrically connecting a CPU with a PCB. The connector comprises an insulative base, a rectangular cover slidably engaged on the base, and a cam actuator for actuating the cover to slide along the base. The base comprises a thick first portion for partially receiving the cam actuator therein, and a thin second portion defining a plurality of receiving holes receiving corresponding electrical terminals therein. Each terminal has a solder ball fused on one end thereof that faces toward the PCB. The first portion has a mounting surface for mounting on the PCB. A recess is defined in the first portion at a middle of the mounting surface, to provide an additional path for heating airflow to reach the solder balls when the connector is soldered to the PCB. This helps ensure that every solder ball is adequately and uniformly heated, so that all the solder balls are accurately fused with the PCB at one time, thereby providing reliable electrical connection of the terminals to the PCB.  
       [0011] Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a simplified isometric view of an electrical connector in accordance with the present invention, viewed from a bottom aspect;  
     [0013]FIG. 2 is an isometric view of the electrical connector of FIG. 1 mounted on a PCB, viewed from a top aspect;  
     [0014]FIG. 3 is a left side plan view of FIG. 2.  
     [0015]FIG. 4 is a bottom plan view of part of the electrical connector of FIG. 1, showing heating airflow paths in and around the electrical connector;  
     [0016]FIG. 5 is a simplified isometric view of a conventional electrical connector, viewed from a bottom aspect;  
     [0017]FIG. 6 is an isometric view of the electrical connector of FIG. 5 mounted on a PCB, viewed from a top aspect; and  
     [0018]FIG. 7 is a bottom plan view of part of the electrical connector of FIG. 5, showing heating airflow paths around the electrical connector. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION  
     [0019] Reference will now be made to the drawings to describe the present invention in detail.  
     [0020] Referring to FIGS. 1 and 2, an electrical connector  1  in accordance with a preferred embodiment of the present invention comprises an insulative base  2 , a rectangular cover  3  slidably engaged on the base  2 , and a cam actuator  4  for actuating the cover  3  to slide along the base  2 . The base  2  includes a thick first portion  21  for partially receiving the cam actuator  4  therein, and a thin second portion  22  defining a plurality of receiving holes  223  for receiving a plurality of corresponding electrical terminals  224  therein. Each terminal  224  comprises a solder ball  222  fused on one end thereof that faces toward a printed circuit board (PCB)  5 . The first portion  21  has a mounting surface  212  for mounting on the PCB  5 . A recess  211  is defined in the first portion  21  at a middle of the mounting surface  212 .  
     [0021] Referring also to FIG. 2, the cover  3  comprises a holding portion  31  and a receiving portion  32 . The holding portion  31  receives the cam actuator  4  and the first portion  21  of the base  2 . The receiving portion  32  corresponds to the second portion  22  of the base  2 , and receives a central processing unit (CPU, not shown) thereon. The receiving portion  32  defines a plurality of through holes  321  therein for receiving lead pins of the CPU, so that the lead pins can further extend into the receiving holes  223  of the base  2  and engage with the terminals  224  therein. The cover  3  has a pair of protrusions  33  respectively formed on two bottom corner portions thereof that are distal from the first portion  21  of the base  2 . Bottom extremities of the first portion  21  and the protrusions  33  are at a same level, such level being parallel to a bottom surface of the second portion  22  of the base  2 . This helps ensure that the electrical connector  1  and the PCB  5  are coplanar when the solder balls  222  are soldered to the PCB  5 .  
     [0022] Referring also to FIG. 3, when the electrical connector  1  is soldered on the PCB  5 , the solder balls  222  are heated and melted. The mounting surface  212  of the first portion  21  of the base  2  in cooperation with the protrusions  33  of the cover  3  control an extent to which the melted solder balls  222  deform. This helps ensure that the electrical connector  1  and the PCB  5  are coplanar.  
     [0023] Referring to FIG. 4, the recess  211  of the first portion  21  provides an additional path for heating airflow to reach the solder balls  222 . This helps ensure that every solder ball  222  is adequately and uniformly heated, so that all the solder balls  222  are accurately fused with the PCB  5  at one time, thereby providing reliable electrical connection of the terminals  224  to the PCB  5 .  
     [0024] While a preferred embodiment in accordance with the present invention has been shown and described, equivalent modifications and changes known to persons skilled in the art according to the spirit of the present invention are considered within the scope of the present invention as defined in the appended claims.