Abstract:
An IC card of the type having a CardBus shield is disclosed in which the dielectric CardBus bridge behind the shield is provided with an upward projection that is positioned behind a front angular part of the top cover of the sheet metal enclosure for the card to support the cover. Preferably, the projection has a front angular surface that conforms to the configuration of the front angular part of the cover. The projection restricts flexural stresses applied to the card and improves environmental sealing of the card.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an IC card and, more particularly, to an IC card having a CardBus shield. 
     IC cards constructed in accordance with PCMCIA (Personal Computer Memory Card International Association) standards, having a CardBus shield for avoiding signal degradation, such as cross-talk between the contacts in the connector of the card, are well known in the art. Examples of such IC cards are disclosed in U.S. Pat. Nos. 5,833,473; 5,896,274; and 5,940,275. 
     As disclosed in the aforementioned patents, a CardBus IC card has a dielectric CardBus bridge mounted within the sheet metal enclosure of the card for positioning a 68-position connector mounted at the front end of the card. The bridge is located at the rear of a cutout that opens at the front of the top cover of the enclosure. The bridge supports the front part of the top cover at the rear of the cutout. A CardBus shield is mounted on the top of the connector spaced forwardly from the front edge of the top cover. A raised projection on the forward portion of the CardBus bridge fills in the space between the front edge of the top cover and the rear of the CardBus shield to provide environmental sealing for the interior of the card. 
     Although the raised projection on the CardBus bridge in the conventional CardBus IC card minimizes the ingress of contaminants into the card and offers some degree of aesthetic continuity, it provides no benefit to the card&#39;s rigidity, which is inherently compromised by the cutout formed in the top cover of the card&#39;s sheet metal enclosure. This cutout allows the connector portion of the card to flex in an upward and downward rotational direction almost entirely unrestricted. The resulting flexural stresses are transferred to the solder joints between the contacts of the  68- position connector, and the conductive pads on the circuit board within the card, and to the solder joints between the tails on the CardBus shield and ground pads on the circuit board, greatly increasing the likelihood of electrical failure. As a result, conventional CardBus IC cards are intrinsically weaker than standard IC cards. 
     It is the object of the present invention to provide an improved CardBus IC card that has enhanced structural strength that resists flexural stresses applied to the card, and improves environmental sealing for the card. 
     SUMMARY OF THE INVENTION 
     According to a principal aspect of the present invention, there is provided an improved CardBus IC card in which the projection on the top of the CardBus bridge is formed adjacent to the rear of the bridge, rather than at the front of the bridge, and is located immediately behind the front angular part of the top cover of the metal enclosure for the card to support the front lateral part of the cover. Preferably, the front surface of the projection has an angular configuration that engages and conforms to the front angular part of the top cover, thereby effectively creating a bend-relief between the bridge and the top cover. This arrangement resists flexural stresses applied to the card and also provides a more effective seal to the inside of the card. 
     Other aspects and advantages of the invention will become more apparent from the following description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an IC card constructed in accordance with the present invention. 
     FIG. 2 is an exploded view of the IC card of FIG.  1 . 
     FIG. 3 is an enlarged sectional view taken along line  3 — 3  of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in detail, there is shown the IC card of the present invention, generally designated  10 , comprising a sheet metal enclosure  12  that encloses a circuit board  14 . The enclosure  12  includes a top cover  16  and bottom cover  18 . A front connector  20  and rear connector  22  are mounted inside the enclosure adjacent to the front end  24  and rear end  26 , respectively, of the circuit board. 
     The front connector  20  is a CardBus connector of the type disclosed in the patents referred to previously herein. The connector comprises a dielectric housing  28  containing two rows of contact passages  30 . Each passage contains a socket contact  32  that is adapted to mate with a pin contact in a host connector (not shown) at the rear of a slot in a personal computer into which the IC card is inserted for use. The connector  20  includes a CardBus shield or ground plate  34  mounted on the top surface of the housing  28  of the connector. The shield includes upstanding bumps  36  that engage a ground plate associated with the host connector. 
     The contacts  32  in the front connector  20  have tails  38  that engage a row of signal traces  40  on the upper surface of the circuit board  14 . The CardBus shield  34  includes tails  42  that engage ground traces  44  on the upper surface of the circuit board positioned in a row behind the row of signal traces  40 . 
     The rear connector  22  contains contacts (not shown) for connecting to the contacts of a cable plug that extends to an accessory, such as a facsimile machine, or to a telephone jack. 
     The top cover  16  has a cutout  46  at its forward end  48  in which the front connector  20  is positioned when the top and bottom covers are assembled to form the completed IC card. The rear of the cutout  46  forms the forward edge  50  of the top cover, which is positioned behind the CardBus shield  34  to provide a space therebetween. 
     A dielectric CardBus bridge  52  mounts the front connector  20  on the forward portion of the circuit board  14 . The bridge has a crossbeam  54  extending between two laterally opposite mounting sides  56  and  58  that are fixed to the circuit board. The sides  56  and  58  include downwardly extending pegs (not shown) that extend into holes  60  and  62  in the circuit board to precisely position the bridge  52  and, hence, the front connector  20 , so that the contact tails  38  and CardBus shield tails  42  will properly engage the traces  40  and  44 , respectively, on the circuit board. Solder connections are made between such tails and traces. 
     The top cover  16  of the sheet metal enclosure  12  has a raised flat upper section  70  and outer flanges  72  and  74  extending along the opposite sides  76  and  78 , respectively, of the top cover. An angular section  80  of the cover interconnects the upper section  70  and the outer flanges  72  and  74 . The angular section also includes a front angular part  84  extending along the forward part  86  of the cover adjacent to the forward edge  50  thereof. 
     The CardBus IC card described so far is generally the same as that disclosed in the patents previously identified herein. As mentioned previously herein, the CardBus bridge of a conventional CardBus IC card has a raised projection formed on the top of the crossbeam adjacent to the front of the crossbeam to fill the space between the forward edge of the top cover and the rear of the CardBus shield to minimize the ingress of contaminates into the interior of the card. However, such raised projection on the CardBus bridge in the prior art IC cards provides no benefit to the card&#39;s rigidity, that is inherently compromised by the cutout at the front of the top cover. The cutout allows the front portion of the card to flex in an upward and downward rotational direction that results in flexural stresses transferred to the solder joints at the ends of the tails of the CardBus shield and the contacts in the CardBus connector, respectively, that greatly increases the likelihood of electrical failure. This problem is overcome by the present invention by locating the laterally extending upward projection  88  on the cross-beam  54  of the CardBus bridge adjacent to the rear  90  of the crossbeam just behind the front angular part  84  of the top cover  16 , as best seen in FIG.  3 . 
     The projection  88  supports the forward lateral part  86  of the top cover, and preferably has a front angular surface  92  that conforms to the front angular part  84  of the cover, effectively creating a true bend-relief between the CardBus bridge and the top cover. This arrangement enhances the rigidity of the IC card at its forward end, thereby resisting flexural stresses that might be applied to the card by the user that otherwise occurs due to the cutout at the front part of the top cover. Also, since the projection  88  follows the angular contour of the top cover, it provides a more effective seal to the inside of the cover, thus avoiding the need of a projection on the front part of the crossbeam  54  of the CardBus bridge as used in the conventional CardBus IC cards of the type disclosed in the patents identified hereinabove. The IC card  10  shown in the drawings is a “frameless” type since only the covers and circuit board extend between the front connector  20  and rear connector  22 . Alternatively, a molded plastic rectangular frame could be used with a dielectric bridge  52  forming the front of the frame, and the frame supporting the front and rear connectors. Also, in such arrangement the rear connector  22  could be eliminated.