Patent Publication Number: US-6341965-B1

Title: Electric connector with shielding effect

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a high density slot electric connector, and especially to an electric connector for enhancing the shielding effect. 
     2. Description of the Prior Art 
     Since information technology is improved quickly, the information devices are more and more popular. Therefore, the requirement of electric connectors is increased vastly, and thus high density becomes a trend in the design of electric connector for reducing the sizes of the devices. However, in high frequency transmission, noise and interruption will become a serious problem due to the compact arrangement of the high density connectors. In general, grounding and shielding resolves these problems. In grounding, a grounding loop is used in the system with a grounding terminal connected with the grounding loop installed between the signal terminals for achieving the system grounding. In many applications of high frequency transmission, in order to insure an effective and reliable grounding, the signal terminals and grounding terminals are arranged alternatively one by one, such as in U.S. Pat. No. 5,026,292. This patent is incorporated into the present invention as a reference. 
     Although the aforementioned design somewhat decreases the noise and interruption, however, in a high speed and large quantity transmission system, the aforesaid design cannot effectively resolve the problem of interruption. Moreover, the number of grounding terminals is increased, so the normal clamping force that the terminals clamp the edge of the circuit track (golden finger) of a circuit substrate is also increased. As a result, the circuit substrate is difficult to pull out of and to insert into, the connector. 
     SUMMARY OF THE INVENTION 
     A slot connector for receiving a circuit substrate comprises a long insulating housing with a central slot being disposed in the longitudinal direction of the insulating housing and a bank of terminal receiving grooves being longitudinally arranged at two sides of the insulating housing. Each bank of terminal receiving grooves is formed by alternatively arranged signal terminal receiving grooves and grounding terminal receiving grooves. A plurality of signal terminals are received with the respective signal terminal receiving grooves. Each signal terminal includes a contact portion, a flexible arm, a fixing portion and a pin portion. A grounding terminal is received within the respective grounding terminal grooves. Each grounding terminal includes a contact portion, a flexible arm, a fixing portion, and a pin portion. At least one of the contact portion, elastic arm, and fixing portion of each grounding terminal has a size larger than that of the corresponding portion of the respective signal terminal. 
     The contact point between the grounding terminal and the circuit substrate has a position higher than the contact point between the signal terminal and the circuit substrate. When the circuit substrate has not been inserted, the gap between contact points of each paired grounding terminal to be contacted with the circuit substrate is thinner than the gap between the contact points of each paired signal terminal. Alternatively, the contact point between the signal terminal and the circuit substrate has a position higher than the contact point between the grounding terminal and the circuit substrate and when the circuit substrate has not been inserted, the gap between contact points of each paired signal terminal to be contacted with the circuit substrate is thinner than the gap between the contact points of each paired grounding terminal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood and its numerous objects and advantages will become apparent to those skilled in the art by referencing to the following drawings in which: 
     FIG. 1 is a partial, perspective view of the electric connector of the present invention. 
     FIG. 2A is a side view showing the signal terminal of the present invention. 
     FIG. 2B is a side view showing the grounding terminal of the present invention. 
     FIG. 3 is a cross sectional view showing the signal terminal of the present invention placed within a receiving groove. 
     FIG. 4 is a cross sectional view showing the grounding terminal of the present invention placed within a receiving groove. 
     FIG. 5 is a cross sectional view showing the overlapped signal terminals and the grounding terminals in the receiving grooves, wherein the grounding terminals are indicated by solid lines, and the signal terminals are indicated by dashed lines. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following embodiments with the appended figures will describe the present invention. However, these embodiments and figures are to be used only to describe the present invention instead of limiting the present invention which is defined solely by the appended claims. 
     With reference to FIG. 1, the electric connector of the present invention includes a long insulating housing  10  with a central slot  20  in the longitudinal direction of the insulating housing  10 . The central slot  20  serves to receive the edge of a circuit substrate  100 . A bank of terminal receiving grooves is longitudinally arranged at two sides of the insulating housing  10 . Each bank of terminal receiving grooves is formed by alternatively arranged signal terminal receiving grooves  12  and grounding terminal receiving grooves  14 . It is appreciated form the figure that the size of the signal terminal receiving groove  12  is slightly different from that of the grounding terminal receiving, groove  14 . This because that the size of the signal terminal of the present invention is slightly smaller than that of the grounding terminal receiving groove. This will be further described in the following description. 
     With reference to FIGS. 2A and 2B, the side views of the signal terminal  30  and the grounding terminal  40  of the present invention are illustrated. It is appreciated from the figures that each signal terminal  30  includes a contact portion  31 , a flexible arm  32 , a fixing portion  33  and a pin portion  34 . The contact portion  31  includes the portion from the uppermost edge of the signal terminal  30  downwards to approximately the contact point P contacting with the circuit substrate  100 . The elastic arm  32  includes the portion from the contact point P to the fixing portion  33 . The elastic arm  32  provides flexible deformation as the circuit substrate  100  inserted into the central slot  20  so that the contact portion  31  has sufficient normal force to firmly and reliably contact with the edge of the circuit substrate  100 . The fixing portion  33  firmly secures the signal terminal  30  in the signal terminal receiving groove  12 . This is achieved by a buckling flange  331  protruding from the two sides of the fixing portion  33  to engage an inner wall of the signal terminal receiving groove  12 . An inverse hook  332  protrudes upwards from the each buckling flange  331  facing to the signal terminal receiving groove  12 . This inverse hook  332  is used to prick into the inner wall of the signal terminal receiving groove  12  as the signal terminal  30  is installed within the signal terminal receiving groove  12  in order to prevent that the signal terminal  30  from dropping out of the signal terminal receiving groove  12 . A pin portion  34  downwardly extends from the lower portion of the fixing portion  33  for being inserted into the respective hole on a primary circuit board (not shown) so as to connect with the circuit on the primary circuit board. 
     Each grounding terminal  40  includes a contact portion  41 , a flexible arm  42 , a fixing portion  43  and a pin portion  44 . The fixing portion  43  further includes a buckling flange  431  and an inverse hook  432 . Since the structures of the grounding terminal  40  and the signal terminal  30  are approximately identical, thus the detail about the components thereof will not be described herein. 
     It will be appreciated from FIGS. 2A and 2B that the transverse dimension of contact portion  41  of the grounding terminal  40  is larger than that of the contact portion  31  of the signal terminal  30 . Moreover, the overall transverse dimension of the fixing portion  43  of the grounding terminal  40  is larger than that of the fixing portion  31  of the signal terminal  30 . Thereby, when signals are transferred in the signal terminal  30  between two adjacent grounding terminals  40 , the enlarged portions of the two grounding terminals  40  on either side of the signal terminal  30  will provide a shielding effect. Thus, the interruption of the signal transferred by the signal terminal  30  is greatly reduced. It should be noted that the spirit of the present invention is that some specific portions of the grounding terminal are designed to be slightly larger than the respective portions of the signal terminal. The numbers and positions of the specific portions are dependent on the shape, application, and assembly of the terminal. Although, in this embodiment, the enlarged contact portion  41  and fixing portion  43  of the grounding terminal  40  serves as an example for describing the present invention, this will not limit the present invention. Alternatively, as described above, the receiving groove  14  of the grounding terminal in the present invention is designed to be larger than the signal terminal receiving groove  12 . By providing some specific portions of the grounding terminal to be slightly larger than the respective portions of the signal terminal, the assembling operation may easily identify the signal terminal and the grounding terminal. 
     As described above, due to the high density of the electric connector, the problem of an increase in the number of terminals increasing the inserting force of the circuit substrate  100  into the central slot  20  must be considered. The present invention provides a solution to this problem. 
     With reference to FIGS. 3,  4 , and  5 , FIGS. 3 and 4 show the cross sectional views of the signal terminal and the grounding terminal, respectively, while FIG. 5 is a schematic cross sectional view showing that the signal terminal and the grounding terminal overlapped. Referring to appended figures, if the vertical distance from the contact point P of the contact portion  31  of the signal terminal  30  to the bending point B of the elastic arm  32  of the signal terminal is L, and the vertical distance from the contact point P′ of the contact portion  41  of the grounding terminal  40  to the bending point B′ of the elastic arm  42  of the grounding terminal  40  is L′, then it can be seen clearly from FIGS. 3 and 4, the distance L′ is larger than L. In other words, when the circuit substrate  100  is inserted into the central slot  20 , the edge of the circuit substrate firstly contacts the grounding terminals of the electric connector, and then when the circuit substrate  100  is further inserted, the edge further contacts the signal terminals of the electric connector. By this design, the forces are applied on the circuit substrate in two stages, to avoid a large force applied to the circuit substrate at one time, so that the circuit substrate is easier to be inserted. 
     However, those skilled in the art may appreciate that the above different elevations of contact points will induce a problem caused by different terminal applying different forces (this is because that the arms of force of deformation torque L and L′ are different). In other words, if the stresses between terminals are different, after several insertions, the elastic fatigues of the terminals on the circuit substrate are different. Thus, some terminals will have bad contact. In order to solve such a problem, the present invention controls the displacements of different terminals so that the normal clamping forces on the edge of the circuit substrate from different terminals are approximately equal. In detail, with reference to FIGS. 3 and 4, the horizontal distance between the contact points P of a pair of signal terminals is G, while the horizontal distance between the contact points P′ of a pair of grounding terminals is set as G′. Then, it is apparent that in the present invention, the horizontal distance between the contact points P of a pair of signal terminals G is larger than the horizontal distance structure the contact points P′ of a pair of grounding terminals G′. Thereby, when the circuit substrate is inserted into the central slot of the electric connector, the normal clamping force of the signal terminals and the grounding terminals are approximately equal. 
     With reference to FIG. 5, the grounding terminals therein are indicated by solid lines, while the signal terminals are indicated by dashed lines. It can be seen from the figure that by the assembled contact portion  41  and fixing portion  43  of the grounding terminal  40  of the present invention will effectively shield the respective portions (i.e. contact portion  31  and the fixing portion  33 ) of the signal terminal  30  and thus, interference is effectively reduced. Since, in the present invention, the grounding terminals and the signal terminals are contacted in different levels, moreover, the gaps between contact points of paired terminals are varied. Thus, the electric connector of the present invention not only reduces the inserting force of the circuit substrate, but also the grounding terminal and the signal terminal can be retained with an approximately equal clamping force. 
     Although the present invention has been described using a specified embodiment, the examples are meant to be illustrative and not restrictive. It is clear that many other variations would be possible without departing from the basic approach, demonstrated in the present invention.