BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a shielding shell structure for an electrical connector, more particularly to a shielding shell structure for an electrical connector having flanges, which could engage with the circuit board to prevent the shielding shell from deforming for the outer force during plug/unplug process. 
   2. Description of Related Art 
   With the advancement of technology, digital products are filled in our daily life gradually, but digital products with large volume are not convenient to the users. Therefore, because of the advancement of technology, more and more digital products make reduction in size to provide more light service to the users. Consequentially, the electrical connectors connecting the digital product and its peripheral device are also miniaturized in size constantly with the development of digital products; the applying range of the Mini-USB receptacle connector is wider and wider. For its high using value and large demand quantities, there are still issues of how to enlarge its applying range and how to heighten its using effect in creating or manufacturing the product. And there are still issues of how to achieve a convenient and stable plug/unplug applying effect. These issues are always the problems to be solved when manufacturers enlarge the product markets and are also objects when manufacturers seek for being to heighten competitive ability. 
   The existing Mini-USB receptacle connector usually comprises a housing, a terminal seat and a shielding shell enclosing around the housing. For the volume of the Mini-USB connector is small, the range enclosed by the shielding shell is consequentially small, relatively the engaging portion thereof is inevitably small, but the received plug/unplug force doesn&#39;t reduce with the reduction of the connector volume. Therefore its durability is tested considerably and the engaging portion of the shielding shell also confronts with an embarrassment of less engaging force. A general convention Mini-USB connector as shown in  FIG. 1 , although there are fastening leg structures on the peripheral, the matching insertion hole area still doesn&#39;t get appropriate reliable structure support. After times of plug/unplug, the insertion portion of the shielding shell may deform and shorten the using life of the product if there is no stable structure. 
   As the mentioned above, the Mini USB receptacle connector is used extensively and frequently, therefore, to strengthen the engaging force of the shielding shell life of the product when the connector volume is reduced is particularly needed. 
   SUMMARY OF THE INVENTION 
   The main object of the present invention is to provide a shielding shell structure for an electrical connector, which has bent flanges on the engaging portion of the shielding shell by engaging the flanges with the circuit board to prevent the shielding shell of the connector from deforming as the outer force applied during plug/unplug process. 
   To achieve the above object, the shielding shell for an electrical connector in the present invention comprises at least one first flange and at least one second flange. The first flange is located on the lower edge of the first engaging piece of the shielding shell, and the second flange is located on the lower edge of the second engaging piece of the shielding shell. The first and second flanges form a flange portion when the first and second engaging pieces interlock with each other to form a bottom engaging portion, and the flange portion bends downward and engages with the circuit board by soldering. 
   In order to have the structure and technical features of the present invention become more apparent to those skilled in the arts, detailed descriptions taken with accompanying drawings are given hereafter. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a section view of the shielding shell of the known electrical connector; 
       FIG. 2  is a perspective view of the preferred embodiment of the present invention; and 
       FIG. 3  is a perspective view of another preferred embodiment of the present invention. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 2 , there is a perspective view of the preferred embodiment of the present invention. The present embodiment is a Mini-USB receptacle connector. In the present invention the electrical connector  100  has a shielding shell  10  enclosing the terminal seat  20  constituted by a housing  20 A and terminals  22 . It has an insertion hole  30  for the mating connector to insert thereinto, so as to achieve electrical connecting effect. In the present embodiment, the connector  100  could be mounted onto the circuit board of the SMT (surface mounting technology) type as an input/output port with the mating connector. The Mini-USB receptacle connector is a conventional structure and the basic structure of the connector in the present invention is similar to the conventional one. Therefore the relevant portions are not described any more. 
   As shown in  FIG. 2 , the housing  20 A is enclosing the terminals  22  therein, and has two downward extending legs  21  to insert into a hole on the circuit board of the Surface Mounting Technology (SMT) type and at least one side block  23  disposed on an either side of the legs  21  in which the thickness of the block  23  is substantial same as that of the terminals  22  so that the bottom position of the block  23  is substantial flush with that of the terminals  22 . The terminals  22  expose from the rear bottom of the housing  20 A each including a vertical portion  221  extending from the rear bottom of the housing  20 A and a horizontal portion  222  bending from the vertical portion  221 . 
   The shielding shell  10  is provided with an upper plane piece  101 , and two front side plane pieces  103 , two middle side plane pieces  104 , two rear side plane piece  105 , two projecting members  104 A and  105 A downward extending from the lower edge of each side plane pieces  104  and  105  so as to enable the bottom portion of the terminal seat  20  to expose to the bottom of the shielding shell  10 , a first engaging piece  103 A and a second engaging piece  103 B on the edge of each side plane pieces  103  respectively. On the lower edge of the first engaging piece  105  extending a bent first flange  107 , and on the lower edge of the second engaging piece  103 B extending a bent second flange  108 . The first engaging piece  103 A and the second engaging piece  103 B could be interlocked with each other by dovetail grooves to form a front bottom engaging portion and along with the upper plane piece  101  as well as the two side plane pieces  103  to define a space for the insertion hole  30 . 
   After the first engaging piece  103 A and the second engaging piece  103 B are interlocked with each other to form an engaging portion, the first flange  107  and the second flange  108  are juxtaposed to form a flange portion. When the connector is mounted onto the circuit board of the SMT type, the flange portion can be inserted into the predetermined hole on the circuit board of the SMT type, with the leg  21  of the housing  20 A and two pairs of downward extending projecting members  104 A  105 A inserted into the respective holes in the SMT circuit board. As a result, the bottom of the horizontal portion  222  of each terminals  22  will be well connected to the respective contacts in the SMT type circuit board and can achieve an excellent electrical connection by soldering. It results in the insertion hole  30  on the front part of the connector being well supported, as well. As a result, the receptacle can endure repeating plug/unplug actions from the mating connector. 
   The present invention still has other various embodiments. As shown in  FIG. 3 , it is a perspective view of another preferred embodiment of the present invention. In the present embodiment, on the appropriate position of the first flange  107  and the second flange  108  respectively having a protrusion  107 A– 108 A which can clasp the hole on the circuit board so that the connector does not detach from the circuit board when the connector is mounted on the circuit board. Therefore the soldering process is reduced but it still achieves the structure of stabilizing the insertion hole space. 
   The structures of the embodiments disclosed in the present invention are illustrative only and not limitative to the scope of the present invention. Any changes or modifications made by those skilled in the art via the description of the present invention without departing from spirits of the invention are considered as like structures of the invention and covered by the claims of the present invention.
The present invention provides a shielding shell structure for an electrical connector. The shielding shell encloses the terminal seat formed by a housing and terminals to constitute the electrical connector. The shielding shell has flanges on its bottom, which could engage with the circuit board so as to intensify the shielding shell and to prevent the shielding shell of the electrical connector from deforming for the outer force during plug/unplug process.