Abstract:
A surface-mount connector ( 100 ) comprises an insulating housing ( 1 ) defining passageways thereon and a plurality of contacts ( 2 ) arranged in the passageways. Each contact comprises a soldering section ( 33 ) extending out the housing, an engagement point ( 321 ) and a middle portion connecting the soldering section and the engagement point. The middle portion touches at least one sidewall of each passageway, and a cutout ( 17 ) is formed on said at least one sidewall of the passageway to space the middle portion from said at least one sidewall.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a surface-mount connector, and more particularly to a surface-mount connector with anti-wicking structures. 
     2. Description of the Related Art 
     Conventional surface-mount connectors, such as board-to-board connectors and DDR connectors, generally are fixed to a board by soldering a plurality of contacts which are retained in the connector. Each contact comprises a soldering leg extending out of an insulating housing of the connector at one end thereof, a contacting portion at another end and the middle portion between said two. The middle portion usually is embedded in the passageways of the housing. When soldering the soldering leg to traces of the board through an appropriate heat means, such as infrared oven, a combination of solder paste and flux will climb up along a slight clearance between the middle portion and sidewalls of the passageways by capillary effect, which is named as wicking in technology. The climbed combination will contaminate the contacting portions of the contacts and decrease performance of the connector. The wicking is more serous in low-profile, height-density connectors. 
     Hence, an improved surface-mount connector is desired to overcome above problems. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a surface-mount connector, which has improved anti-wicking characteristics during process of mounting the connector to a circuit board. 
     In order to obtain the objective above, a surface-mount connector comprises an insulating housing defining passageways thereon and a plurality of contacts arranged in the passageways. Each contact comprises a soldering section extending out the housing, an engagement point and a middle portion connecting the soldering section and the engagement point. The middle portion touches at least one sidewall of each passageway, and a cutout is formed on said at least one sidewalls to space the middle portion from said at least one sidewall. 
     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 view of a surface-mount connector according to an embodiment of the invention; 
         FIG. 2  is an elevational view of a contact of upper row; 
         FIG. 3  is an elevational view of a contact of lower row; 
         FIG. 4  is an sectional view taken along line  4 — 4  of  FIG. 1 ; and 
         FIG. 5  is an enlarged perspective view of the electrical connector showing in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a surface-mount connector  100  according to one embodiment of the present invention is adapted for receiving an electrical card, such as DDR. 
     The connector  100  includes an elongated insulating housing  1 . The housing  1  defines a longitudinal card-receiving slot  10  and two rows of contact-receiving passageways  11  along the opposite top and bottom inner surfaces of the slot  10  to receive a plurality of contacts  2 . A key  12  is defined in the slot  11  at predetermined place to prevent from anti-mating of the card. A pair of arm portions  13  respectively extends from two opposite ends of the housing  1  and a metal portion  14  is disposed on each arm portion  13 . The metal portions  14  mainly abut against the outmost walls of the arm portions  13 . A semi-circular locking portion  144 , extending from the front top edge of the metal portion  14 , spans the front top portion of the arm portion  13  to lock the card in the connector. A L-shaped portion  142  is formed with extending inward from the front bottom portion of the metal portion  14  and then vertically backwards bending. One end  143  of a solder pad  146  is retained in the arm portion and another end  145  is upright to encounter the distal end of the L-shaped portion  142 . The distal end of the L-shaped portion  142  and the upright end  145  can prevent excessive out-movement of the arm portion  13 . A rib  141  extends downwards from the locking portion  144  to clip the front top portion of the am portion  13  with the metal portion  14 . 
     Referring to  FIG. 3 , each lower contact  3  includes an elongated retention section  30  with tabs  35  on its upper edge, a cantilever resilient contact section  32  extending from one end of the retention section  30 , and a soldering section  33  extending from the lower edge of said one end of the retention section  30 . As  FIG. 4  shown, the lower contacts  3  are retained in the contact-receiving passageways with its tabs  35  secured in the a retention slit  16 . Two block portions  31  on the retention section encounter the front of the retention slit  16  to prevent the contact from turning. The contacting sections  32  extend into the slot  10  with an engagement point  321 . The solder sections  33  extend out of the insulating housing  1  and each comprises a parallel portion  332  and a downward-slanting portion  331  connecting the parallel portion  332  with the retention section  30 . The parallel portion  333  defines its bottom surface as a soldering face  333  to solder its on a circuit board. 
     Referring to  FIG. 2 , each upper contact  4  is similar to the lower contact  3  and also includes a retention section  41  with tabs  45 , a cantilever resilient contacting portion  42  and a solder section  43  extending out the housing. 
     Referring to  FIGS. 4–5 , two neighboring passageways  11  are separated by a partition  15 . The retention sections  30 ,  40  retain the contacts in the passageways  11 , and the engagement points  321  extend beyond top faces  151  of the partitions  15 . The insertion of the card into the card-receiving slot  10  will resiliently press downwards the contacts, especially the cantilever resilient contacting portion  32 . So the contacts are accommodated in the passageways with its sides close to the sidewalls  152  of the passageways/the partitions, but separate with slight clearance, which result in wicking sometimes. The improvement of this invention is that each partition  15  is partially cut out. A part of each partition  15  adjacent to the soldering section  33  is taken away to form a cutout  17  as  FIG. 5  shown, and parts of the neighboring retention sections  31  are exposed to face each other, i.e. a bottom face  153  of each partition is beyond a corresponding jointing line at which the soldering section connects with the retention section of the contact in a direction that opposite to that the soldering section extends. Therefore the enlarged distance between the sides of the contacts and the sidewalls of the passageways prevents the solder paste and flux from climbing up by capillary effect, i.e. anti-wicking. Alternatively, the cutouts  16  may be recessed into the sidewalls  152  of the partition  15  and throughout the middle portion transversely, not throughout when width of the partitions is enough. Or the cutouts are defined correspondingly to a middle portion thereinto, the middle portion including parts between the engagement portion  321  and the soldering section of the contacts. All cutouts cut off the climbing traces of solder paste, and the function of anti-wicking is obtained. 
     The wicking of soldering paste might occur in conventional low profile BTB connector. Plate middle portions of contacts are embedded in shallow recesses in the outer/inner sidewalls of the BTB connector with soldering section extending out of the sidewalls. The solder paste will climb up along clearances between the sidewalls and the contacts. As improvement, a part of each sidewall near to the soldering section is partially cut off to increase width of the clearance, and the middle portions of the neighboring contacts partially exposed to each other, which obtain anti-wicking function. 
     It is to be understood, however, that even though numerous, characteristics and advantages of the present invention have been set fourth in the foregoing description, together with details of the structure and function of the invention, the disclosed is illustrative only, and changes may be made in detail, especially in matters of number, 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.