Patent Publication Number: US-9837772-B2

Title: Electrical receptacle connector

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims priority under 35 U.S.C. §119(a) to Patent Application No. 201520953468.2 filed in China, P.R.C. on Nov. 26, 2015, the entire contents of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The instant disclosure relates to an electrical connector, and more particular to an electrical receptacle connector. 
     BACKGROUND 
     Generally, Universal Serial Bus (USB) is a serial bus standard to the PC architecture with a focus on computer interface, consumer and productivity applications. The existing Universal Serial Bus (USB) interconnects have the attributes of plug-and-play and ease of use by end users. Now, as technology innovation marches forward, new kinds of devices, media formats and large inexpensive storage are converging. They require significantly more bus bandwidth to maintain the interactive experience that users have come to expect. In addition, the demand of a higher performance between the PC and the sophisticated peripheral is increasing. The transmission rate of USB 2.0 is insufficient. As a consequence, faster serial bus interfaces such as USB 3.0, are developed, which may provide a higher transmission rate so as to satisfy the need of a variety devices. 
     The appearance, the structure, the contact ways of terminals, the number of terminals, the pitches between terminals (the distances between the terminals), and the pin assignment of terminals of a conventional USB type-C electrical connector are totally different from those of a conventional USB electrical connector. A conventional USB type-C electrical receptacle connector includes a plastic core, upper and lower receptacle terminals held on the plastic core, and an outer iron shell circularly enclosing the plastic core. Normally, the plastic core of a conventional USB type-C electrical receptacle connector is an assembly of several plastic components, and the upper receptacle terminals and the lower receptacle terminals are respectively assembled with the plastic components. 
     SUMMARY OF THE INVENTION 
     The flat contact portions of the receptacle terminals of the conventional receptacle connector are originally attached on the surface of a front portion of the tongue portion. However, when the tongue portion is deflected upward or downward due to swaying of the plastic core, the flat contact portions might be detached from the tongue portion. Hence, in operation, the receptacle terminals of the electrical receptacle connector would not contact the plug terminals of an electrical plug connector efficiently due to the flat contact portions of the receptacle terminals are detached from the tongue portion. Therefore, how to solve the aforementioned problem is an issue. 
     In view of this, an embodiment of the instant disclosure provides an electrical receptacle connector. The electrical receptacle connector comprises a metallic shell, a mount member, a tongue portion, a plurality of first receptacle terminals, a plurality of second receptacle terminals, and a shielding plate. The metallic shell comprises a receptacle cavity. The mount member is received in the receptacle cavity of the metallic shell. The tongue portion is integrally formed on one of two sides of the mount member. The tongue portion comprises a plurality of terminal grooves and a plurality of recesses. The terminal grooves are formed on a first surface of the tongue portion. Each of the recesses is recessed toward a tip of the tongue portion from an inner sidewall in the corresponding terminal groove. Each of the recesses comprises two lateral surfaces and a bottom surface therein. For each of the recesses, a first lateral surface of the two lateral surfaces is extending from the inner sidewall toward an interior of the recess and connected to one of two opposite edges of the bottom surface, and a second lateral surface of the two lateral surfaces is extending from an inner surface of the corresponding terminal groove toward the interior of the recess and connected to the other edge of the bottom surface. The first receptacle terminals are on a first side of the mount member. Each of the first receptacle terminals comprises a first flat contact portion and a first tail portion extending from one end of the first flat contact portion and protruding from the mount member. The first flat contact portions are held in the terminal grooves. End portions of the first flat contact portions are received in the recesses. Abutting surfaces of the end portions of the first flat contact portions are abutted against the first lateral surfaces of the recesses. The second receptacle terminals are on a second side of the mount member opposite to the first side. Each of the second receptacle terminals comprises a second flat contact portion and a second tail portion extending from one end of the second flat contact portion and protruding from the mount member. The second flat contact portions are held on a second surface of the tongue portion opposite to the first surface. The shielding plate is on the mount member and the tongue portion. The shielding plate is between the first flat contact portions and the second flat contact portions. 
     In one embodiment, the tongue portion comprises a plurality of limiting blocks formed on the first lateral surfaces of the recesses. The end portions of the first flat contact portions are abutted against the limiting blocks, respectively. 
     In one embodiment, the tongue portion comprises a plurality of through holes formed on a front lateral surface of the tongue portion and respectively communicating with the recesses. 
     In one embodiment, each of the first flat contact portions comprises a positioning portion and a slant portion outward extending from the positioning portion, and an end portion of the slant portion is inserted into the corresponding recess. 
     In one embodiment, each of the first flat contact portions comprises a positioning portion and a parallel portion parallel to and outward extending from the positioning portion, and an end portion of the parallel portion is inserted into the corresponding recess. 
     In one embodiment, the tongue portion comprises a plurality of protruding blocks respectively protruding from groove walls of the terminal grooves to abut against bottoms of the first flat contact portions. 
     In one embodiment, the mount member further comprises a first terminal base and a second terminal base. The first terminal base is assembled with the first receptacle terminals. The second base is integrally formed with the tongue portion and is assembled with the second receptacle terminals. The first terminal base is assembled on the second terminal base. 
     In one embodiment, the mount member comprises a plurality of first assembling grooves, and the first receptacle terminals are assembled in the first assembling grooves, respectively. 
     In one embodiment, the mount member comprises a plurality of second assembling grooves, and the second receptacle terminals are assembled in the second assembling grooves, respectively. 
     In one embodiment, the first receptacle terminals are on the first surface of the tongue portion, the second receptacle terminals are on the second surface of the tongue portion. The first receptacle terminals and the second receptacle terminals have 180 degree symmetrical design with respect to a central point of the receptacle cavity as the symmetrical center. 
     As above, recesses are provided in the terminal grooves for receiving end portions of the flat contact portions of the first receptacle terminals, and the abutting surfaces of the end portions are abutted against the first lateral surfaces of the recesses. Therefore, when the tongue portion is inserted into or detached from an electrical plug connector, the end portions are constrainted in the recesses. As a result, upon the tongue portion is deflected, the flat contact portions are not detached from the tongue portion. Accordingly, the connector can provide good stability and reliability in the contact with the electrical plug connector. Moreover, the tongue portion comprises the through holes formed on the front lateral surface thereof and communicating with the recesses, respectively. Therefore, the recesses can be manufactured conveniently, and fixtures can be taken out of the tongue portion through the through holes after the recesses are manufactured. Additionally, the flat contact portions of the first receptacle terminals comprise the slant portions. When the slant portions are received in the terminal grooves, the slant portions continuously abut against the groove walls of the terminal grooves to prevent the flat contact portions from detaching off the tongue portion. 
     Furthermore, the first receptacle terminals and the second receptacle terminals are arranged upside down, and the pin-assignment of the flat contact portions of the first receptacle terminals is left-right reversal with respect to that of the flat contact portions of the second receptacle terminals. Accordingly, the electrical receptacle connector can have a 180-degree symmetrical, dual or double orientation design and pin assignments which enables the electrical receptacle connector to be mated with a corresponding plug connector in either of two intuitive orientations, i.e. in either upside-up or upside-down directions. Therefore, when an electrical plug connector is inserted into the electrical receptacle connector with a first orientation, the flat contact portions of the first receptacle terminals are in contact with upper-row plug terminals of the electrical plug connector. Conversely, when the electrical plug connector is inserted into the electrical receptacle connector with a second orientation, the flat contact portions of the second receptacle terminals are in contact with the upper-row plug terminals of the electrical plug connector. Note that, the inserting orientation of the electrical plug connector is not limited by the electrical receptacle connector of the instant disclosure. 
     Detailed description of the characteristics and the advantages of the instant disclosure are shown in the following embodiments. The technical content and the implementation of the instant disclosure should be readily apparent to any person skilled in the art from the detailed description, and the purposes and the advantages of the instant disclosure should be readily understood by any person skilled in the art with reference to content, claims, and drawings in the instant disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The instant disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus not limitative of the instant disclosure, wherein: 
         FIG. 1  illustrates a perspective view of an electrical receptacle connector according to an exemplary embodiment of the instant disclosure; 
         FIG. 2  illustrates an exploded view of the electrical receptacle connector; 
         FIG. 3  illustrates an another exploded view of the electrical receptacle connector; 
         FIG. 4  illustrates a lateral sectional view of the electrical receptacle connector shown in  FIG. 3 ; 
         FIG. 5  illustrates an lateral sectional view of the assembled electrical receptacle connector shown in  FIG. 3 ; 
         FIG. 6A  illustrates a partial enlarged view showing an end portion of a first flat contact portion is received in a recess; 
         FIG. 6B  illustrates a partial enlarged view showing an end portion of a first flat contact portion is received in a recess in which the recess runs through the tongue portion; and 
         FIG. 7  illustrates a lateral sectional view of another embodiment of the assembly of the electrical receptacle connector. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIGS. 1 and 2 , illustrating an electrical receptacle connector of an exemplary embodiment of the instant disclosure.  FIG. 1  illustrates a perspective view of an electrical receptacle connector according to an exemplary embodiment of the instant disclosure.  FIG. 2  illustrates an exploded view of the electrical receptacle connector. In this embodiment, the electrical receptacle connector  100  is assembled with a circuit board by sinking technique. That is, one side of the circuit board is cut to form a crack, and the electrical receptacle connector  100  is positioned at the crack and extending toward the side portion of the circuit board. In this embodiment, the electrical receptacle connector  100  can provide a reversible or dual orientation USB Type-C connector interface and pin assignments, i.e., a USB Type-C receptacle connector. In this embodiment, the electrical receptacle connector  100  comprises a metallic shell  11 , a mount member  21 , a tongue portion  22 , a plurality of first receptacle terminals  31 , a plurality of second receptacle terminals  41 , and a shielding plate  7 . 
     Please refer to  FIGS. 1 and 2 . In this embodiment, the metallic shell  11  is a hollowed shell, and the metallic shell  11  comprises a shell body  111  and a receptacle cavity  112  formed in the shell body  111 . In other words, the metallic shell  11  comprises a receptacle cavity  112  for receiving the first receptacle terminals  31  and the second receptacle terminals  41 . In this embodiment, the metallic shell  11  may be a tubular member and the receptacle cavity  112  is formed in the tubular member. The metallic shell  11  may be formed by a multi-piece member; in such embodiment, the metallic shell  11  comprises an inner shell  121  and a cover shell  122 , wherein the inner shell  121  is a tubular member and encloses the mount member  21 , and the cover shell  122  has a U-shape cross section and covers the top and the two sides of the inner shell  121 , but embodiments are not limited thereto. In some embodiments, the cover shell  122  may be a hollowed shell and encloses the inner shell  121 . In addition, an insertion opening  113  with oblong shaped is formed on one side of the metallic shell  11 , and the insertion opening  113  communicates with the receptacle cavity  112 . 
     Please refer to  FIG. 2 . In this embodiment, a terminal module  2  is received in the receptacle cavity  112  of the metallic shell  11 . The terminal module  2  comprises the mount member  21 , the tongue portion  22 , the first receptacle terminals  31 , the second receptacle terminals  41 , and the shielding plate  7 . 
     Please refer to  FIGS. 2 to 5 . In this embodiment, the mount member  21  is received in the receptacle cavity  112  of the metallic shell  11 . The mount member  21  comprises a first terminal base  211  and a second terminal base  213  assembled with each other. The first receptacle terminals  31  are on the first terminal base  211 , and the second receptacle terminals  41  and the shielding plate  7  are on the second terminal base  213 . The second terminal base  213  is integrally formed with the tongue portion  22 , and the first terminal base  211  is assembled on the second terminal base  213 , but embodiments are not limited thereto. In some embodiments, the first terminal base  211  and the second terminal base  213  may be further integrally formed as a whole, and the mount member  21  comprises a plurality of first assembling grooves  214  and a plurality of second assembling grooves  215  (as shown in  FIG. 7 ). The first receptacle terminals  31  are assembled in and engaged with the first assembling grooves  214 , respectively, and the second receptacle terminals  41  are assembled in and engaged with the second assembling grooves  215 , respectively. Accordingly, the connector may have different assembling ways so as to increase the applicability of the connector product. 
     Please refer to  FIGS. 2, 3, and 5 . The tongue portion  22  has two opposite surfaces, one is a first surface  221   a , and the other is the second surface  221   b . In addition, a front lateral surface  221   c  of the tongue portion  22  is connected the first surface  221   a  with the second surface  221   b  and is close to the insertion opening  113 . In other words, the front lateral surface  221   c  is near the insertion opening  113  and perpendicularly connected to the first surface  221   a  and the second surface  221   b , respectively. 
     Please refer to  FIGS. 2, 3, 5, and 6A . In this embodiment, the tongue portion  22  is integrally formed with the mount member  21  and formed on one side of the mount member  21 . The tongue portion  22  comprises a plurality of terminal grooves  23  and a plurality of recesses  24 . The terminal grooves  23  are formed on a surface (i.e., the first surface  21   a ) of the tongue portion  22 . The terminal grooves  23  are provided for assembling the flat contact portions  315  of the first receptacle terminals  31  therein. Each of the recesses  24  is recessed toward a tip of the tongue portion  22  from an inner sidewall  23   a  in the corresponding terminal groove  23 . Each of the recesses  24  comprises two lateral surfaces  241 ,  242  and a bottom surface  243 . For each of the recesses  24 , a first lateral surface  241  is extending from the inner sidewall  23   a  toward the interior of the recess  24  and connected to one of two opposite edges of the bottom surface  243 , a second lateral surface  242  is extending from an inner surface  23   b  of the corresponding terminal groove  23  toward the interior of the recess  24  and connected to the other edge of the bottom surface  243 . Furthermore, the tip of the tongue portion  22  is near the insertion opening  113 . The end portions  315   a  of the flat contact portions  315  are received in the recesses  24 , and abutting surfaces of the end portions  315   a  of the flat contact portions  315  are abutted against the first lateral surfaces  241  of the recesses  24 . Hence, when the tongue portion  22  is inserted into or detached from an electrical plug connector, the end portions  315   a  of the flat contact portions  315  are constrainted in the recesses  24 . Therefore, once the tongue portion  22  is deflected upward or downward, the flat contact portions  315  will not detach from the tongue portion  22 . Accordingly, the connector can provide good stability and reliability in the contact with the electrical plug connector. In detail, in this embodiment, the recess  24  is recessed from one side of the terminal groove  23 ; that is, the tongue portion  22  comprises a plurality of limiting blocks  223  respectively formed on the first lateral surfaces  241  of the recesses  24 , and the end portions  315   a  of the flat contact portions  315  are abutted against and limited by the limiting blocks  223 . Hence, the end portions  315   a  of the flat contact portions  315  can be prevented from being detached from the tongue portion  22 . Therefore, connector can provide stable contact and transmission with the electrical plug connector. 
     In the foregoing embodiment, the recess  24  is formed on one side of the terminal groove  23  but not runs through the tongue portion  22 . In some embodiments, the tongue portion  22  may further comprise a plurality of through holes  225  (as shown in  FIG. 6B ). The through holes  225  are formed on the front lateral surface  22   c  of the tongue portion  22  and respectively communicating with the recesses  24 . In other words, from a front view of the connector, the through holes  225  can be seen, and the through holes  225  are penetrating to the recess  24 . Accordingly, in the formation of the tongue portion  22 , the recesses  24  can be manufactured conveniently, and fixtures can be taken out of the tongue portion  22  through the through holes  225  after the recesses  24  are manufactured. 
     Please refer to  FIGS. 2, 3, 4, and 6A . In this embodiment, the first receptacle terminals  31  are held in the first terminal base  211 . Each of the first receptacle terminals  31  comprises a flat contact portion  315  and a tail portion  316 . The flat contact portions  315  are positioned in the terminal grooves  23 , and front ends  315   a  of the flat contact portions  315  are received in the recesses  24 . Each of the tail portions  316  is extending from one end of the corresponding flat contact portion  315  and protruding from the mount member  21 . In this embodiment, each of the flat contact portions  315  comprises a positioning portion  3151  and a slant portion  3152  outward extending from the positioning portion  3151 , and an end portion of the slant portion  3152  (i.e., the end portion  315   a ) is inserted into the corresponding recess  24 . Accordingly, since the slant portion  3152  is bent downward to create an angle with the positioning portion  3151 , when the slant portions  3152  are received in the terminal grooves  23 , the slant portions  3152  continuously abut against the groove walls of the terminal grooves  23  to prevent the flat contact portions  315  from detaching off the tongue portion  22 . 
     It is understood that, the flat contact portions  315  with the slant portions  3152  are for illustrative purposes. Alternatively, each of the flat contact portions  315  may comprise the positioning portion  3151  and a parallel portion  3153  parallel to and outward extending from the positioning portion  3151  (as shown in  FIG. 7 ), and an end portion of the parallel portion  3153  (i.e., the end portion  315   a ) is inserted into the corresponding recess  24 . 
     In this embodiment, the tongue portion  22  comprises a plurality of protruding blocks  231  (as shown in  FIG. 6A ). The protruding blocks  231  are respectively protruding from groove walls of the terminal grooves  23  to abut against bottoms of the flat contact portions  315 . The protruding blocks  231  are in the terminal grooves  23  to make the groove walls of the terminal grooves  23  have different thicknesses. Accordingly, when the slant portions  3152  are assembled in the terminal grooves  23 , the protruding blocks  231  are abutted against bottoms of the slant portions  3152 , and the end portions of the slant portions  3152  are slantly received in the recesses  24  and positioned by the recesses  24 . 
     Please refer to  FIGS. 2 to 4 . The second receptacle terminals  41  and the shielding plate  7  are held in the second terminal base  213 . Each of the second receptacle terminals  41  comprises a flat contact portion  415  and a tail portion  416 . Each of the tail portions  416  is extending from one end of the corresponding flat contact portion  415  and protruding from the mount member  21 . 
     Please refer to  FIGS. 2 and 4 . The shielding plate  7  is held in the mount member  21  and the tongue portion  22 . The shielding plate  7  comprises a plate body  71  and a plurality of legs  72 . The plate body  71  is between the flat contact portions  315  of the first receptacle terminals  31  and the flat contact portions  415  of the second receptacle terminals  41 . Specifically, the plate body  71  may be lengthened and widened, so that the front of the plate body  71  is near the front lateral surface  221   c  of the tongue portion  22 , two sides of the plate body  71  is near two sides of the tongue portion  22  for contacting an electrical plug connector, and the rear of the plate body  71  is near the rear of the tongue portion  22 . Accordingly, the plate body  71  can be disposed on the tongue portion  22  and the second terminal base  213 , and the structural strength of the tongue portion  22  and the shielding performance of the tongue portion  22  can be improved. 
     Please refer to  FIGS. 2, 3, and 5 . The first receptacle terminals  31  comprise a plurality of first signal terminals  311 , power terminals  312 , and ground terminals  313 . The first signal terminals  31  comprises a plurality of pairs of first high-speed signal terminals  3111 / 3113  and a pair of first low-speed signal terminals  3112 . From a front view of the first receptacle terminals  31 , the first receptacle terminals  31  comprise, from left to right, a ground terminal  313  (Gnd), a first pair of first high-speed signal terminals  3111  (TX1+−, differential signal terminals for high-speed signal transmission), a power terminal  312  (Power/VBUS), a first function detection terminal  3141  (CC1, a terminal for inserting orientation detection of the connector and for cable recognition), a pair of first low-speed signal terminals  3112  (D+−, differential signal terminals for low-speed signal transmission), a first supplement terminal  3142  (SBU1, a terminal can be reserved for other purposes), another power terminal  312  (Power/VBUS), a second pair of first high-speed signal terminals  3113  (RX2+−, differential signal terminals for high-speed signal transmission), and another ground terminal  313  (Gnd). In this embodiment, twelve first receptacle terminals  31  are provided for transmitting USB 3.0 signals. Each pair of the first high-speed signal terminals  3111 / 3113  is between the corresponding power terminal  312  and the adjacent ground terminal  313 . The pair of the first low-speed signal terminals  3112  is between the first function detection terminal  3141  and the first supplement terminal  3142 . 
     In some embodiments, the rightmost ground terminal  313  (Gnd) (or the leftmost ground terminal  313  (Gnd)) or the first supplement terminal  3142  (SBU1) can be further omitted. Therefore, the total number of the first receptacle terminals  31  can be reduced from twelve terminals to seven terminals. Furthermore, the ground terminal  313  (Gnd) may be replaced by a power terminal  312  (Power/VBUS) and provided for power transmission. In this embodiment, the width of the power terminal  312  (Power/VBUS) may be, but not limited to, equal to the width of the first signal terminal  311 . In some embodiments, the width of the power terminal  312  (Power/VBUS) may be greater than the width of the first signal terminal  311  and an electrical receptacle connector  100  having the power terminal  312  (Power/VBUS) can be provided for large current transmission. 
     Please refer to  FIGS. 3, 4, and 7 . The first receptacle terminals  31  are held in the first terminal base  211  and formed as the upper-row terminals of the electrical receptacle connector  100 . Each of the first receptacle terminals  31  comprises a flat contact portion  315 , a body portion  317 , and a tail portion  316 . For each of the first receptacle terminals  31 , the body portion  317  is held in the first terminal base  211 , the flat contact portion  315  is extending forward from the body portion  317  in the rear-to-front direction and partly exposed upon the first surface  221   a  of the tongue portion  22 , and the tail portion  316  is extending backward from the body portion  317  in the front-to-rear direction and protruding from the rear of the first terminal base  211 . The first signal terminals  311  are disposed on the first surface  221   a  and transmit first signals (namely, USB 3.0 signals). The tail portions  316  are bent horizontally to form flat legs, named legs manufactured by SMT (surface mounted technology), which can be mounted or soldered on the surface of a printed circuit board by using surface mount technology. Alternatively, the tail portions  316  may be extending downwardly to form vertical legs, named legs manufactured by through-hole technology, which can be inserted into holes drilled in a printed circuit board (PCB). 
     Please refer to  FIGS. 3, 4, and 7 . The second receptacle terminals  41  comprise a plurality of second signal terminals  411 , power terminals  412 , and ground terminals  413 . The second receptacle terminals  41  comprise a plurality of pairs of second high-speed signal terminals  4111 / 4113  and a pair of second low-speed signal terminals  4112 . From a front view of the second receptacle terminals  41 , the second receptacle terminals  41  comprise, from right to left, a ground terminal  413  (Gnd), a first pair of second high-speed signal terminals  4111  (TX2+−, differential signal terminals for high-speed signal transmission), a power terminal  412  (Power/VBUS), a second function detection terminal  4141  (CC2, a terminal for inserting orientation detection of the connector and for cable recognition), a pair of second low-speed signal terminals  4112  (D+−, differential signal terminals for low-speed signal transmission), a second supplement terminal  4142  (SBU2, a terminal can be reserved for other purposes), another power terminals  412  (Power/VBUS), a second pair of second high-speed signal terminals  4113  (RX1+−, differential signal terminals for high-speed signal transmission), and another ground terminal  413  (Gnd). In this embodiment, twelve second receptacle terminals  41  are provided for transmitting USB 3.0 signals. Each pair of the second high-speed signal terminals  4111 / 4113  is between the corresponding power terminal  412  and the adjacent ground terminal  413 . The pair of the second low-speed signal terminals  4112  is between the second function detection terminal  4141  and the second supplement terminal  4142 . 
     In some embodiments, the rightmost ground terminal  413  (or the leftmost ground terminal  413 ) or the second supplement terminal  4142  (SBU2) can be further omitted. Therefore, the total number of the second receptacle terminals  41  can be reduced from twelve terminals to seven terminals. Furthermore, the rightmost ground terminal  413  may be replaced by a power terminal  412  and provided for power transmission. In this embodiment, the width of the power terminal  412  (Power/VBUS) may be, but not limited to, equal to the width of the second signal terminal  411 . In some embodiments, the width of the power terminal  412  (Power/VBUS) may be greater than the width of the second signal terminal  411  and an electrical receptacle connector  100  having the power terminal  412  (Power/VBUS) can be provided for large current transmission. 
     Please refer to  FIGS. 3, 4, and 7 . The second receptacle terminals  41  are held in the second terminal base  213  and formed as the lower-row terminals of the electrical receptacle connector  100 . In addition, the first receptacle terminals  31  are substantially aligned parallel with the second receptacle terminals  41 . In this embodiment, each of the second receptacle terminals  41  comprises a flat contact portion  415 , a body portion  417 , and a tail portion  416 . For each of the second receptacle terminals  41 , the body portion  417  is held in the second terminal base  213  and the tongue portion  22 , the flat contact portion  415  is extending from the body portion  417  in the rear-to-front direction and partly exposed upon the second surface  221   b  of the tongue portion  22 , and the tail portion  416  is extending backward from the body portion  417  in the front-to-rear direction and protruding from the rear of the second terminal base  213 . The second signal terminals  411  are disposed at the second surface  221   b  and transmit second signals (i.e., USB 3.0 signals). The tail portions  416  are bent horizontally to form flat legs, named legs manufactured by SMT (surface mounted technology), which can be mounted or soldered on the surface of a printed circuit board by using surface mount technology. Alternatively, the tail portions  416  may be extending downwardly to form vertical legs, named legs manufactured by through-hole technology, which can be inserted into holes drilled in a printed circuit board (PCB). The tail portions  316  of the first receptacle terminals  31  and the tail portions  416  of the second receptacle terminals  41  are arranged in a staggered manner from the top view. 
     Please refer to  FIGS. 2 and 4 . The legs  72  are extending from the rear portion of the shielding plate  7  to form vertical legs. That is, the legs  72  are exposed from the second terminal base  213  and in contact with a circuit board. In this embodiment, the crosstalk interference can be reduced by the shielding of the shielding plate  7  when the flat contact portions  315 ,  415  transmit signals. Furthermore, the structural strength of the tongue portion  22  can be improved by the assembly of the shielding plate  7 . In addition, the legs  72  of the shielding plate  7  are exposed from the second terminal base  213  and in contact with the circuit board for conduction and grounding. 
     Please refer to  FIGS. 2 and 3 . The shielding plate  7  further comprises a plurality of hooks  73 . The hooks  73  are extending outward from two sides of the front portion of the plate body  71  and protruding from the front lateral surface  221   c  and two sides of the tongue portion  22 . When an electrical plug connector is mated with the electrical receptacle connector  100 , elastic pieces at two sides of an insulated housing of the electrical plug connector are engaged with the hooks  73 , and the elastic pieces would not wear against the tongue portion  22  of the electrical receptacle connector  100 . Hence, the shielding plate  7  can be in contact with the metallic shell  11  for conduction and grounding. 
     Please refer to  FIGS. 2, 3, and 5 . In this embodiment, the first receptacle terminals  31  and the second receptacle terminals  41  are disposed upon the first surface  221   a  and the second surface  221   b  of the tongue portion  22 , respectively, and pin-assignments of the first receptacle terminals  31  and the second receptacle terminals  41  are point-symmetrical with a central point of the receptacle cavity  112  as the symmetrical center. In other words, pin-assignments of the first receptacle terminals  31  and the second receptacle terminals  41  have 180-degree symmetrical design with respect to the central point of the receptacle cavity  112  as the symmetrical center. The dual or double orientation design enables an electrical plug connector to be inserted into the electrical receptacle connector  100  in either of two intuitive orientations, i.e., in either upside-up or upside-down directions. Here, point-symmetry means that after the first receptacle terminals  31  (or the second receptacle terminals  41 ), are rotated by 180 degrees with the symmetrical center as the rotating center, the first receptacle terminals  31  and the second receptacle terminals  41  are overlapped. That is, the rotated first receptacle terminals  31  are arranged at the position of the original second receptacle terminals  41 , and the rotated second receptacle terminals  41  are arranged at the position of the original first receptacle terminals  31 . In other words, the first receptacle terminals  31  and the second receptacle terminals  41  are arranged upside down, and the pin assignments of the flat contact portions  315  are left-right reversal with respect to that of the flat contact portions  415 . An electrical plug connector is inserted into the electrical receptacle connector  100  with a first orientation where the first surface  221   a  is facing up, for transmitting first signals. Conversely, the electrical plug connector is inserted into the electrical receptacle connector  100  with a second orientation where the first surface  221   a  is facing down, for transmitting second signals. Furthermore, the specification for transmitting the first signals is conformed to the specification for transmitting the second signals. Note that, the inserting orientation of the electrical plug connector is not limited by the electrical receptacle connector  100  according embodiments of the instant disclosure. 
     Additionally, in some embodiments, the electrical receptacle connector  100  is devoid of the first receptacle terminals  31  (or the second receptacle terminals  41 ) when an electrical plug connector to be mated with the electrical receptacle connector  100  has upper and lower plug terminals. In the case that the first receptacle terminals  31  are omitted, the upper plug terminals or the lower plug terminals of the electrical plug connector are in contact with the second receptacle terminals  41  of the electrical receptacle connector  100  when the electrical plug connector is inserted into the electrical receptacle connector  100  with the dual orientations. Conversely, in the case that the second receptacle terminals  41  are omitted, the upper plug terminals or the lower plug terminals of the electrical plug connector are in contact with the first receptacle terminals  31  of the electrical receptacle connector  100  when the electrical plug connector is inserted into the electrical receptacle connector  100  with the dual orientations. 
     Please refer to  FIG. 2  and  FIGS. 3 to 5 . In this embodiment, as viewed from the front of the receptacle terminals  31 ,  41 , the position of the first receptacle terminals  31  corresponds to the position of the second receptacle terminals  41 . In other words, the positions of the flat contact portions  315  are respectively aligned with the positions of the flat contact portions  415 , but embodiments are not limited thereto. In some embodiments, the first receptacle terminals  31  may be aligned by an offset with respect to the second receptacle terminals  41 . That is, the flat contact portions  315  are aligned by an offset with respect to the flat contact portions  415 . Accordingly, because of the offset alignment of the flat contact portions  315 ,  415 , the crosstalk between the first receptacle terminals  31  and the second receptacle terminals  41  can be reduced during signal transmission. It is understood that, when the receptacle terminals  31 ,  41  of the electrical receptacle connector  100  have the offset alignment, plug terminals of an electrical plug connector to be mated with the electrical receptacle connector  100  would also have the offset alignment. Hence, the plug terminals of the electrical plug connector can be in contact with the receptacle terminals  31 ,  41  of the electrical receptacle connector  100  for power or signal transmission. 
     In the foregoing embodiments, the receptacle terminals  31 ,  41  are provided for transmitting USB 3.0 signals, but embodiments are not limited thereto. In some embodiments, for the first receptacle terminals  31  in accordance with transmission of USB 2.0 signals, the first pair of the first high-speed signal terminals  3111  (TX1+−) and the second pair of the first high-speed signal terminals  3113  (RX2+−) are omitted, and the pair of the first low-speed signal terminals  3112  (D+−) and the power terminals  312  (PowerNBUS) are retained. While for the second receptacle terminals  41  in accordance with transmission of USB 2.0 signals, the first pair of the second high-speed signal terminals  4111  (TX2+−) and the second pair of the second high-speed signal terminals  4113  (RX1+−) are omitted, and the pair of the second low-speed signal terminals  4112  (D+−) and the power terminals  412  (Power/VBUS) are retained. 
     As above, recesses are provided in the terminal grooves for receiving end portions of the flat contact portions of the first receptacle terminals, and the abutting surfaces of the end portions are abutted against the first lateral surfaces of the recesses. Therefore, when the tongue portion is inserted into or detached from an electrical plug connector, the end portions are constrainted in the recesses. As a result, upon the tongue portion is deflected, the flat contact portions are not detached from the tongue portion. Accordingly, the connector can provide good stability and reliability in the contact with the electrical plug connector. Moreover, the tongue portion comprises the through holes formed on the front lateral surface thereof and communicating with the recesses, respectively. Therefore, the recesses can be manufactured conveniently, and fixtures can be taken out of the tongue portion through the through holes after the recesses are manufactured. Additionally, the flat contact portions of the first receptacle terminals comprise the slant portions. When the slant portions are received in the terminal grooves, the slant portions continuously abut against the groove walls of the terminal grooves to prevent the flat contact portions from detaching off the tongue portion. 
     Furthermore, the first receptacle terminals and the second receptacle terminals are arranged upside down, and the pin-assignment of the flat contact portions of the first receptacle terminals is left-right reversal with respect to that of the flat contact portions of the second receptacle terminals. Accordingly, the electrical receptacle connector can have a 180-degree symmetrical, dual or double orientation design and pin assignments which enables the electrical receptacle connector to be mated with a corresponding plug connector in either of two intuitive orientations, i.e. in either upside-up or upside-down directions. Therefore, when an electrical plug connector is inserted into the electrical receptacle connector with a first orientation, the flat contact portions of the first receptacle terminals are in contact with upper-row plug terminals of the electrical plug connector. Conversely, when the electrical plug connector is inserted into the electrical receptacle connector with a second orientation, the flat contact portions of the second receptacle terminals are in contact with the upper-row plug terminals of the electrical plug connector. Note that, the inserting orientation of the electrical plug connector is not limited by the electrical receptacle connector of the instant disclosure. 
     While the instant disclosure has been described by the way of example and in terms of the preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.