Patent Publication Number: US-7217143-B2

Title: Electrical connector

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector, and more particularly to an electrical connector for surface mounting on a printed circuit board. 
     2. Description of Related Art 
     Generally, a conventional electrical connector for electrically connecting a chipset to a printed circuit board (PCB) is attached to the PCB by soldering terminals thereof to the PCB via Surface Mounting Technology (SMT). Before the electrical connector is attached to the PCB, solder tails of the terminals should be adjusted to perform a wonderful coplanarity so as to ensure that each of the terminals can be reliably soldered to the PCB. 
     CN. Pat. No. 200320103928.X discloses an electrical connector including a housing with a pair of cantilevered side walls in opposite ends of the housing, a plurality of terminals loaded in the housing and a pair of metallic latches assembled to the housing. Each said latch has a body, which assembled to the side wall, a securing arm downwardly extending from a distal end of the body, a mounting portion formed near a downmost distal end of the securing arm, and a flexing portion joining the securing arm and the mounting portion. The mounting portion includes two slips respectively positioned at frontside and rearside of the flexing portion. There is a cutout defined between the flexing portion and each of the slips. Since the mounting portion is soldered onto the PCB by SMT together with the solder tails of the terminals, it is required that the tails of the terminals and the mounting portion of the latch perform a good coplanarity, or else neither facility nor reliability of soldering operation can&#39;t be ensured. However, since the terminals and the latch are formed from different metal sheets and are assembled on the housing separately, it is difficult to ensure a wonderful coplanarity between said tails and said mounting portion. Thus the latches should adjust the position of a solder surface of the mounting portions thereof for gaining a coplanarity with the tails of the terminals. Therefore, the flexing portion should be compressed if the securing arm is too long to perform a coplanarity with the tails of the terminals, or should be drawn out if the securing arm is too short to perform a coplanarity with the tails of the terminals. However, such compression or drawing operation may causes the mounting portion to slant from the PCB, as a result of which the connecting area between the mounting portion and the PCB is reduced and the capability of connecting is weakened. Moreover, the solder tails of terminals are apt to be twisted by an unintentional and improper operation during adjusting of the latches so that some tails of the terminals may be deformed to destroy the coplanarity. Furtheremore, to adjust the mounting portion coplanarity with the solder tails of the terminals after the adjusting of the coplanarity between the tails increases an additional procedure. 
     Therefore, an improved electrical connector is desired to overcome the disadvantages of the prior arts. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an electrical connector including terminals and mounting portions, wherein solder tails of the terminals can maintenance a good coplanarity, the terminals and the securing portions can both be reliably soldered to a PCB. 
     In order to achieve above-mentioned object, an electrical connector in accordance with a preferred embodiment of the present invention includes an insulative housing; a plurality of terminals disposed in the housing, a plurality of terminals disposed in the housing and having tails extending beyond the housing, all the tails defining a common mounting plane; at least a metallic mounting portion assembled to the housing, said metallic mounting portion defining a bottom plane for soldering to the PCB, said bottom plane located vertically above said mounting plane with a distance therebetween; and a solder ball connecting to the mounting portion, said solder ball being able to be softened to fill said distance during soldering. 
     Other objects, advantages and novel features of the present 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 an assembled perspective view of an electrical connector in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is an exploded, perspective view of the electrical connector shown in  FIG. 1 , wherein metallic latches are detached from a housing thereof; 
         FIG. 3  is a top plan view thereof; 
         FIG. 4  is a right side elevational view thereof; and 
         FIG. 5  is a cross-sectional view of  FIG. 1  taken along line  5 — 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     References will now be made to the drawing figures to describe the preferred embodiment of the present invention in detail. 
     Referring to  FIGS. 1 and 2 , an electrical connector  7  for electrically and mechanically connecting an electronic card (not shown) to a printed circuit board (PCB) (not shown) in accordance with the preferred embodiment of the present invention, comprises a housing  1 , a plurality of terminals  5 , and a pair of metallic latches  4 , wherein the housing  1  includes an elongated body  2  retaining the terminals  5  therein and a pair of cantilevered side walls  3  respectively extending from two opposite longitudinal ends of the body  2 . 
     Referring to  FIGS. 2 ,  4  and  5 , the housing  1  made from the insulative material further includes two positioning posts  23  on the bottom of the body  2  to position the housing  1  to the PCB. The body  2  define an elongated slot  21  along the longitudinal direction thereof for retaining one end of the electronic card and a plurality of passageways  22  communicating with the slot  21 . Each side wall  3  includes a first portion  32  and a second portion  33  which define a gap therebetween, wherein said first portion  32  includes a latching portion  321  and a retaining portion  322  at a free end thereof, and said second portion  33  defines a mating groove  331 . As best shown in  FIG. 3 , the terminals  5  are respectively inserted into the passageways forwardly or rearwardly in two rows, each said terminal  5  is loaded in a corresponding passageway  22 , with one end thereof extending into the slot  21 , and the other end  51  thereof, called as solder tail  51 , extending beyond the body  2  for mechanically and electrically connecting to the PCB, as best shown in  FIG. 5 . Since the two rows of terminals are assembled on the housing separately, the solder tails of terminals should be adjusted to form a common mounting plane  52  performing a wonderful coplanarity. The electronic card is inserted into the slot  21  to have conductors thereof mechanically and electrically connected to the end of the corresponding terminal  5  so as to form an electrical connection between the electronic card and the PCB. 
     Referring to  FIGS. 1 and 2 , each metallic latch  4  comprises an elongated base portion  41  with some protuberances  411  in one end thereof, a jointing portion  43  vertically extending down from the other end thereof, and a mounting portion  42  horizontally and laterally extending from the jointing portion  43 , which defines a hole  422  in a center thereof and will be soldered to the PCB. The metallic latch further comprises a connecting piece  44  extending vertically from the base portion  41  between the protuberances  411  and the jointing portion  43 , and a latching piece  45  extending from the connecting piece  44 . The latching piece  45  includes an upright portion  451  connecting to the connecting piece  44 , a guiding portion  452 , a retaining portion  455 , a first position piece  453  and a second piece  454 . The aforementioned guiding portion, the retaining portion, the first position piece and the second position piece all are located at the distal end of the upright portion  451 . 
     Referring to  FIG. 1 , in assembly, each metallic latch  4  is fastened to the side wall  3  via the base portion  41  with the protuberances  411  thereof inserted into the groove  331 . The retaining portion  455  firmly catches hold of the first portion  32 , and the guiding portion  452  cover a top face of the latching portion  321  for protecting the latching portion  321  from being scraped during insertion of the electronic card. The upright portion  451  tightly abuts on exterior surface of the first portion  32  for enhancing the first portion  32 , while the first position piece  453  and the second piece  454  are positioned respectively at two opposite sides of the second portion  33 . The aforementioned first position piece  453 , second position piece  454  and second portion  33  prevent the first portion  32  from being excessively bended and broken when the first portion  32  and the upright portion  451  move associatively for releasing the electronic card. 
     As best shown in  FIGS. 4 and 5 , after assembled, the bottom plane  421  of the mounting portion parallels to the mounting plane  52  and forms a distance D therebetween. As seen, H 1  is the distance between the top portion  431  of the jointing portion  43  and the mounting plane  52 , and H 2  is the distance between the top portion  431  of the jointing portion  43  and the bottom plane  421  of the mounting portion  42 , deviation of which defines the dimension of the distance D which is about 0.005˜0.1 millimeters preferably. A solder ball  6  is pre-welded to the mounting portion  42  on the bottom plane  421 , and has a dimension vertically extending from the bottom plane  421  a little larger than the distance D. When the aforementioned connector with solder balls  6  is positioned to the PCB by means of positioning the positioning post  23 , the connector slightly inclines up at the side of the side walls  3  (left side as shown in  FIG. 4 ) because the dimension of the solder balls  6  is a little larger than the distance D. Since the heated solder balls  6  are optionally deformable in configuration, during surface soldering process, the slightly inclined connector becomes aclinic to make the mounting plane  52  and the bottom plane  421  of the mounting portion  42  be parallel to the PCB. Because the solder ball  6  is big enough, the distance D is filled with solder, while the excessive solder can overflow through the hole  422  of the mounting potion  42 . As a result, the coplanarity of the solder tails  51  can be maintained, and the terminals  5  and the mounting portions  42  are reliably soldered to the PCB with facility. 
     In fact, the coplanarity of the solder tails  51  can also be maintained if the solder ball  6  extending from said bottom plane  421  is a little smaller than the distance D between said bottom plane  421  and said mounting plane  52 , since the heated solder balls  6  will downwards flow to the PCB and fill the distance D, during surface soldering process. As a result, the coplanarity of the tails  51  can be maintained, and the terminals  5  and the mounting portions  42  are reliably soldered to the PCB. Likely, the solder ball  6  also can be placed above on the mounting portion  42 , then during surface soldering process, the heated solder downwards flows through the holes  422  and fills the distance D, so the coplanarity of the tails  51  can be maintained. 
     However, the disclosure is illustrative only, changes may be made in detail, especially in matter of shape, size, and arrangement of parts within the principles of the invention.