Patent Publication Number: US-6666702-B1

Title: Electrical connector with matching differential impedance

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector, and particularly to an electrical connector with matching differential impedance in according to high transmitting frequency and speed of signal. 
     2. Description of Prior Art 
     During the past decade, PCI standard has been a very successful, general purpose I/O interconnect standard instead of ISA standard. However, demands of emerging and future computing models will exceed the bandwidth and scalability limits that are inherent in multi-drop, parallel bus implementations. Technologies such as Central Process Unit (CPU) speeds that will exceed 10 GHz, faster memory speeds, higher-speed graphics, 1 Gigabit and 10 Gigabit Local Area Network (LAN), IEEE1394b, InfiniBand, fabrics and others will drive the need for much greater internal bandwidth. Thus, an improved industrial interconnect standard, such as 3GIO standard which is established by Intel, is required. The 3GIO architecture will be a high performance, highly flexible, scalable, reliable, stable and cost effective general purpose I/O architecture that is the natural evolution of PCI. The signaling, protocol and mechanical features of 3GIO standard is disclosed on an article entitled “Creating a Third Generation I/O Interconnect”, which is published on the web: 
     http://www.intel.com/technology/3gio/downloads/3rdGenWhitepaper.htm. 
     As the 3GIO standard can stand higher frequency and faster speed than the PCI and ISA, a connector conforming the 3GIO standard requires matching differential impedance as well as the insertion/return losses and the cross-talk. 
     In addition, impedance matching of terminals has already been discussed in U.S. Pat. Nos. 5,066,136, 5,496,183, 4,664,968 and 6,347,962. In these patents, each right angle connectors comprises a terminal module and a shielding member. The shielding member is redesigned to match the impedance of contacts of the terminal module. 
     An alternative electrical connector has been proposed in U.S. Pat. No. 5,713,764. A card edge connector comprises an insulative housing and a plurality of terminals received in the insulative housing. The terminals comprises body portions located in the insulative housing and contact portions for mating with corresponding terminals of a mating connector. The area of the body portion is selectively varied to vary the capacitance of the terminal, therefore, the impedance of the connector may match a given impedance of a mating electrical circuit. 
     However, the designs cannot be applied on an electrical connector conforming to the 3GIO standard with matching differential impedance for high frequency and fast speed. Hence, an improved electrical connector of the 3GIO standard is required to overcome the disadvantages of the conventional connector. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide an electrical connector with matching differential impedance for high frequency and speed. 
     In order to achieve the object set forth, an electrical connector comprises an insulative housing and a first and second terminals received in the insulative housing. The insulative housing comprises an upper wall and a lower wall defining a receiving cavity therebetween for receiving an inserted daughter card. The insulative housing defines a receiving passageway in communicating with the receiving cavity. The receiving passageway includes a first passageway section and a second passageway section. The width of the first passageway section is different from that of the second passageway section. Each of the terminals comprises a contacting portion projecting into the receiving cavity for contacting with the daughter card. The first terminal includes a resilient arm received in the receiving passageway. The width of the first terminal is smaller than that of either of the first passageway sections whereby a room in the receiving passageways is left by the terminals for tuning differential impedance. 
     The invention also contemplates an electrical connector comprising an insulative housing and a plurality of terminals received in the insulative housing. The insulative housing comprises an upper wall and a lower wall with a receiving cavity therebetween. The upper wall forms a plurality of rear projections at a rear end thereof and the lower wall forms a plurality of front projections at a front end thereof. Every two adjacent projections define a receiving recess. Each of the terminal comprises a mounting plate received in a corresponding receiving recess. The mounting plate forms a plurality of retention dimples for engaging with corresponding projections to securely retain the terminal in a true position. 
    
    
     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. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, perspective and front view of an electrical connector of a first embodiment in accordance to the present invention; 
     FIG. 2 is an exploded, perspective and rear view of the electrical connector of FIG. 1; 
     FIG. 3 is a perspective view of a pair of terminals in FIG. 1; 
     FIG. 4 is an assembled, front view of the electrical connector in FIG. 1; 
     FIG. 5 is an assembled, rear view of the electrical connector in FIG. 2; 
     FIG. 6 is a front planar view of the electrical connector in FIG. 4; 
     FIG. 7 is an enlarged view of a circled portion  7  of FIG. 6; 
     FIG. 8 is a cross-sectional view of the electrical connector showing an upper terminal received in an insulative housing; 
     FIG. 9 is a cross-sectional view of the electrical connector showing a lower terminal receiving in the insulative housing; 
     FIG. 10 is a perspective view of a pair of terminals in accordance to a second embodiment of the present invention; 
     FIG. 11 is an enlarged view similar to FIG. 7 in accordance to the second embodiment; 
     FIG. 12 is a cross-sectional view similar to FIG. 8 in accordance to the second embodiment; and 
     FIG. 13 is a cross-sectional view similar to FIG. 9 in accordance to the second embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made to the drawing figures to describe the present invention in detail. 
     Referring to FIG. 1, an electrical connector  1  conforming to the 3GIO standard in accordance to a first embodiment of the present invention is shown. The electrical connector  1  comprises an insulative housing  2  and a plurality of upper terminals  3  and lower terminals  4  received in the insulative housing  2 . 
     Further referring to FIGS. 1 and 2, the insulative housing  2  comprises a main body  20  and a pair of arms  21  extending forwardly from lateral edges of the main body  20 . The arms  21  each form a latch  210  extending upwardly from a free end thereof for securely retaining an inserted daughter card (not shown) on the insulative housing  2 . The main body  20  defines a mounting surface  208  on a bottom thereof for engaging with a mother board (not shown) and a mating surface  207  perpendicular to the mounting surface  208  for engaging with the inserted daughter card. In addition, the main body  20  comprises an upper wall  201 , a lower wall  202 , a pair of sidewalls  203  interconnecting the upper wall  201  and the lower wall  202 , and a rear wall  204  interconnecting the sidewalls  203 , the upper wall  201  and the lower wall  202  at a rear end thereof. The upper wall  201 , lower wall  202 , rear wall  204  and sidewalls  203  together define a receiving cavity  200  for receiving the daughter card. A key protrusion  23  extends forwardly from a substantially middle portion of the rear wall  204  beyond the mating surface  207  for securing a true insertion of the daughter board. The key protrusion  23  interconnects with the upper wall  201  and the lower wall  202  respectively at an upper and lower end thereof. 
     In conjunction with FIGS. 8 and 9, the insulative housing  2  forms a plurality of retention walls  22  on an inner face of the upper wall  201  and through the rear wall  204 . Every two adjacent retention walls  22  define a receiving passageway in communicating with the receiving cavity  200 . The receiving passageway includes an upper passageway section  230  and a lower passageway section  230 . It should be noted that the width of the lower passageway section  230  is larger than that of the upper passageway section  230  and the width of the upper passageway section  230  is a slightly larger than that of the upper terminal  3 . The rear wall  204  forms a plurality of rear projections  241  at a rear end thereof below the retention walls  241 . Every two adjacent rear projections  241  define a rear retaining recess  240  therebetween. The lower wall  22  forms a plurality of front projections  221  at a front end thereof. Every two adjacent front projections  221  defines a front retaining recess  220  therebetween. In addition, the lower wall  202  defines a plurality of front retaining holes  222  in communicating with corresponding front retaining recesses  220  at a front end thereof and a plurality of rear retaining holes  242  in communicating with corresponding rear retaining recesses  240  at a rear end thereof. It should be noted that the front and rear retaining holes  222 ,  242  extend along a front to rear direction. 
     Referring to FIG. 3, each of the upper terminals  3  comprises a first mounting plate  30 , a first connecting portion  31  extending upwardly from a top end of the first mounting plate  30 , a substantially horizontal first resilient arm  32  extending forwardly from a top end of the first connecting portion  31 , a horizontal first retention arm  33  extending forwardly from a top end of the first mounting plate  30  and a horizontal first solder tail  34  at a bottom end of the first mounting portion  30 . A curved first contacting portion  320  projects downwardly at a free end of the first resilient arm  32 . Similarly, each of the lower terminals  4  comprises a second mounting plate  40 , a second connecting portion  41  extending upwardly from a top end of the second mounting plate  40 , a substantially horizontal second resilient arm  42  extending rearwardly from a top end of the second connecting portion  41 , a horizontal second retention arm  43  extending forwardly from a top end of the second mounting plate  40  and a horizontal second solder tail  44  at a bottom end of the second mounting portion  40 . A curved second contacting portion  420  projects upwardly at a free end of the second resilient arm  42 . 
     Referring to FIGS. 4-5 in conjunction with FIGS. 8-9, in assembly, the lower terminals  4  are assembled to the main body  20  of the insulative housing  2  with the second retention arms  43  received in corresponding front retaining holes  222 . The second resilient arms  42  project into the receiving cavity  200  and a portion of each second retention plate  40  is received in a corresponding front retaining recess  220 . The upper terminals  3  are assembled to the main body  20  of the insulative housing  2  with the first resilient arms  32  received in corresponding upper and second passageway sections  230 ,  232  and the first retention arms  33  received corresponding rear retaining holes  242 . The first contacting portions  320  project into the receiving cavity  200  and a portion of each first retention plate  30  is received in a corresponding rear retaining recess  240 . Successively, the electrical connector I is assembled to a mother board (not shown) with the first and second solder tails  34 ,  44  soldering on corresponding solder pads of the mother board. While the daughter card is inserted into the receiving cavity  200  of the main body  20 , the latches  210  engages with lateral edges of the daughter card for securely retaining the daughter card in a true position. Meanwhile, the first contacting portions  320  of the upper terminals  3  are contacting with corresponding contacting pads on an upper surface of the daughter card. The second contacting portions  420  of the lower terminals  4  are contacting with corresponding contacting pads on a lower surface of the daughter card. 
     Referring to FIGS. 6 and 7, the first resilient arms  32  are received in corresponding upper and second passageway sections  230 ,  232 . Because the width of the upper passageway section  230  is slightly larger than that of the first resilient arm  32  of the upper terminals  3  and the width of the lower passageway section  230  is larger than that of the first passageway section  230 , room between the first resilient arm  32  and a corresponding retention wall  22  may be fulfilled with different media, such as air or plastic etc., for tuning capacitance between two adjacent upper terminals  3 . Therefore differential impedance between two adjacent upper terminals  3  is matched in accordance to different transmitting frequency and speed of signal. 
     FIGS. 10-14 show a design of second embodiment in accordance to the present invention. In this embodiment, each of upper (lower) terminals  5  ( 6 ) comprises a mounting plate  50  ( 60 ), a contacting portion  51  ( 61 ) and a solder tail  54  ( 64 ). An insulative housing  7  comprises a plurality of front and rear projections  721  ( 741 ). Every two projections  721  ( 741 ) define a receiving recess for receiving the mounting plate  50  ( 60 ). The mounting section  50  ( 60 ) forms a plurality of transverse retention dimples  500  ( 600 ) for engaging with corresponding projections  721  ( 741 ) to securely retain the terminal  5  ( 6 ) in a true position. There is no retention arm in this embodiment; such will avoid producing inductance between the contacting portion and the retention arm. Therefore, the terminal has a controlled differential impedance in spite of increasing frequency and transmitting speed of the signal. The others are the same as the first embodiment well described in the above; thus, a detailed description thereof is omitted here. 
     It is apparent that the two embodiments may be combined together. For example, in the first embodiment, the terminals may have retention dimples instead of the retention arm. Therefore, the capacitance and inductance of the terminals may be tuned, thereby varying the differential impedance according to different frequency and transmitting speed of signal. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of 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.